White liquor treatment method, white liquor oxidation monitoring system

Abstract

To provide a technique that can grasp the state of white liquor as accurately as possible.SOLUTION: A white liquor processing method monitors the color tone of white liquor in pulp manufacturing, and controls the state of the white liquor from the color tone. The color tone is color tone data of the white liquor acquired by measuring the color tone of the white liquor, and it is suitable to control the state of the white liquor from the color tone data. It is suitable that the color tone data of the white liquor is one or two or more selected from the group consisting of the R relative light reception amount of the white liquor, and the G relative light reception amount of the white liquor.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a white liquor treatment method, a white liquor oxidation monitoring system, a method for adjusting the polysulfide concentration contained in the white liquor, and the like. [Background technology]

[0002] Pulp is produced by adding pulping water (also called pulping solution) containing sodium hydroxide and sodium sulfide to wood chips and pulping it. White liquor is used as this pulping water. In the pulping process, the wood chips are steamed with alkali (white liquor) to obtain pulp, and pulping agents and thermal energy are recovered from the pulp wastewater (black liquor). In the pulp manufacturing process, chemicals are recovered from the pulping process, pulp washing process, black liquor concentration process, black liquor combustion process, green liquor treatment process, white liquor treatment process, saturation reaction process, caustic reaction process, and lime calcination process, and the recovered chemicals are reused.

[0003] In pulp production, the digestion process is crucial for efficiently obtaining pulp, making it important to improve pulp yield or suppress yield decline. One cause of the decline in pulp yield during this digestion process is the peeling reaction, in which the polysaccharide reducing end groups (aldehyde groups) of pulp (cellulose fibers) are sequentially detached. To counteract this peeling reaction, sodium polysulfide (Na2Sx: also called polysulfide (PS)), which is obtained by oxidizing sodium sulfide, is used. This polysulfide is known to oxidize these reducing end groups into carboxyl groups that are stable against the peeling reaction.

[0004] In current pulp manufacturing, methods for producing white liquor (digesting agent) containing sodium polysulfide and sodium hydroxide include a method of directly adding elemental sulfur to the white liquor, which is the digesting agent of the Kraft process, to produce sodium polysulfide; a method of oxidizing sodium sulfide in the white liquor with air using a solid catalyst such as activated carbon to produce sodium polysulfide (Non-Patent Literature 1); and a white liquor electrolysis method (Non-Patent Literature 2).

[0005] In the pulping process, understanding the sodium polysulfide concentration in the white liquor is crucial for managing, adjusting, or controlling the concentration of sodium polysulfide in the white liquor to prevent peeling reactions. However, conventional techniques do not convert sodium sulfide (Na2S) in the white liquor to sodium polysulfide (Na2S). X Manual analysis using sampling was used to understand the oxidation process.

[0006] Furthermore, as a method for measuring the concentration of sodium polysulfide pulping solution, a method using ion chromatography, a type of liquid chromatography, has been proposed to analyze and calculate the concentration more quickly and with practical accuracy compared to conventional methods (Patent Document 1).

[0007] Patent Document 1 describes a method for composing the ions of sodium polysulfide (Na2S) in the digestant used in the sodium polysulfide digestion process. X This relates to a method for analyzing (x-1)S in the given context. Patent Document 1 discloses a method for analyzing sulfur polysulfide in a sodium polysulfide pulping solution, characterized by reacting sulfite ions with an alkaline aqueous solution containing sodium polysulfide ions of a sodium polysulfide pulping solution to convert the sulfur polysulfide that makes up the sodium polysulfide ions into thiosulfate ions, and then analyzing the thiosulfate ions or sulfite ions in the solution containing these thiosulfate ions and / or sulfite ions as an analytical sample, and calculating the amount of sulfur polysulfide based on the increase in thiosulfate ions obtained or the decrease in the reacted sulfite ions.

[0008] Furthermore, Patent Document 2 discloses a method for analyzing sodium polysulfide, characterized by reacting an alkylating agent with an alkaline aqueous solution containing sodium polysulfide ions to convert each polysulfide ion component that makes up sodium polysulfide into each dialkyl polysulfide, and then performing high-performance liquid chromatography analysis using these compounds as analytical samples. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 07-92148 [Patent Document 2] Japanese Patent Application Laid-Open No. 06-027095 [Patent Document 3] Japanese Patent Application Laid-Open No. 2022-12850 [Patent Document 4] Japanese Patent Application Laid-Open No. 2018-083176 [Non-Patent Document]

[0010] [Non-Patent Document 1] Kazuhiro Kurosu, Journal of the Paper and Pulp Technical Association of Japan, Vol. 65, No. 9, pp. 42-47 (September 2011) [Non-Patent Document 2] Technical News from Overseas, "Polysulfide Digestion by the MOXY Process" (G.C. Smith, S.E. Knowles and R.P. Green., Paper Trade Journal / May 1, 1975), Journal of the Paper and Pulp Technical Association of Japan, Vol. 29, No. 10, pp. 25-28 (October 1975) [Non-Patent Document 3] SCAN-N 30:85 (SCANDINAVIAN PULP, PAPER AND BOARD TESTING. COMMITTEE, 1985). [Summary of the Invention] [Problems to be Solved by the Invention] <00…… (The original text seems to be incomplete here. The ellipsis indicates that there are some parts not fully presented in the provided source text. The translation is continued based on the existing content, but there may be some loss of context due to the incomplete source.)

[0011] In the conventional manual analysis method by sampling, it was impossible to simply and quickly measure sodium polysulfide in white liquor, and it was also difficult to continuously measure it. Therefore, in such a conventional polysulfide detection or measurement method, it was impossible to grasp the concentration of sodium polysulfide in white liquor from before flowing into the polysulfide generation process to after flowing out of the polysulfide generation process in real time. For this reason, the adjustment of the polysulfide concentration in white liquor (also referred to as "polysulfide cooking chemical solution") in the polysulfide generation process could not be sufficiently carried out. Therefore, with the conventional polysulfide concentration detection or measurement method, it was difficult to adjust to a stable polysulfide concentration that could take countermeasures against the peeling reaction in the cooking process. As a result, the pulp yield decreased in the cooking process, significantly inhibiting productivity. Also, in the analysis of the sodium polysulfide concentration in the sodium polysulfide cooking chemical solution by ion chromatography, due to the sample collection and various reagent reaction pretreatments after sample collection, the inventors considered that it was desired to grasp the sodium polysulfide concentration in white liquor as simply and in real time as possible.

[0012] Therefore, the main object of the present invention is to provide a technique that can accurately grasp the state of white liquor as much as possible.

Means for Solving the Problems

[0013] As a result of intensive studies, the inventors have found that, compared with the conventional manual analysis, the state of white liquor (specifically, the estimation of the polysulfide concentration (g / L as S) in white liquor) can be grasped in real time as accurately as possible from the color tone of white liquor, and thus completed the present invention.

[0014] The present invention is as follows.

[0015] The present invention provides a white liquor treatment method for monitoring the color tone of white liquor used in the cooking process of pulp production and controlling the state of white liquor from the color tone. The present invention provides a white liquor oxidation monitoring system that monitors the color tone of the white liquor used in the pulping process of pulp production and controls the state of the white liquor based on color tone data obtained by measuring the color tone of the white liquor. The aforementioned color tone is the color tone data of the white liquid obtained by measuring its color tone, and it is preferable to control the state of the white liquid from this color tone data. Preferably, the color tone data of the white liquid is one or more selected from the group consisting of the R relative light reception amount of the white liquid and the G relative light reception amount of the white liquid. Preferably, the R-relative light-receiving amount of the white liquor, or the G-relative light-receiving amount of the white liquor, correlates with the polysulfide concentration in the white liquor. The aforementioned color data is the R-relative light reception amount of the white liquid or the G-relative light reception amount of the white liquid. If the R relative light intensity or the G relative light intensity is higher than the set value for the R relative light intensity or the G relative light intensity, the state of the white liquor is controlled to promote the polysulfide formation reaction of the white liquor, or If the R-relative light-receiving amount or the G-relative light-receiving amount is lower than the set value for the R-relative light-receiving amount or the G-relative light-receiving amount, it is preferable to control the state of the white liquor so as to suppress the polysulfide formation reaction in the white liquor. The control of the state of the white liquor is preferably achieved by adjusting the amount of oxygen supplied to the white liquor. Preferably, the color tone data is the R-relative light reception amount of the white liquid or the G-relative light reception amount of the white liquid. [Effects of the Invention]

[0016] According to the present invention, a technique can be provided that allows for the most accurate determination of the state of the white liquor. However, the effects of the present invention are not necessarily limited to those described herein, and may include any of the effects described herein. [Brief explanation of the drawing]

[0017] [Figure 1]This is a schematic diagram of a pulp manufacturing system equipped with a polysulfide manufacturing system according to an embodiment of the present invention, but this is just one example of the present invention and is not limited thereto. [Figure 2] Figure 2A is a schematic diagram of the first embodiment, which preferably includes a white liquor color measuring unit (color detection unit) installed near the inlet between the smoking / caustication system 40 and the inlet of the polysulfide production process (reactor), and a control unit for controlling the white liquor state, but is not limited thereto. Figure 2B is a schematic diagram of the second embodiment, which preferably includes a white liquor color measuring unit (color detection unit) installed near the outlet of the polysulfide production process (reactor) and the digestion system 10 (digestion vessel 11), or near the inlet of the digestion vessel 11, and a control unit for controlling the white liquor state, but is not limited thereto. [Figure 3] Figure 3 is a schematic diagram of the third embodiment, which preferably includes a plurality of white liquor color monitoring units (color detection units) installed near the inlet and outlet of the polysulfide production process (reactor), an oxygen supply unit and a temperature control unit related to the polysulfide production process, and a control unit for controlling the white liquor state, but is not limited thereto. [Figure 4] This is an example of a schematic diagram of a flow showing the control of the white liquor state (preferably the polysulfide formation reaction) based on color data in this embodiment, and the present invention is not limited thereto. [Figure 5] This is an example of a schematic diagram of a flow chart showing an example of controlling the white liquor state (preferably the polysulfide formation reaction) by comparing color processing data with set values ​​(set ranges) in this embodiment, and the present invention is not limited thereto. [Figure 6] This is an example of a schematic flow diagram illustrating an example of controlling the state of the white liquor (preferably the polysulfide formation reaction) by comparing color processing data (preferably an estimated value of the polysulfide concentration in the white liquor) with a set range (preferably a set range of polysulfide concentration) in this embodiment, and the present invention is not limited thereto. [Figure 7]This is an example of a schematic flow diagram showing an example of controlling the white liquor state (preferably the polysulfide formation reaction) by comparing color processing data (preferably the relative R light reception amount) with a set range (preferably the set range of the relative R light reception amount) in this embodiment, and the present invention is not limited thereto. [Figure 8] Figure 8A shows the relationship between the relative R, G, and B light levels and the polysulfide concentration in Test Examples 1 No. 1 to 5. The right vertical axis represents the relative R, G, and B light levels, the left vertical axis represents the polysulfide concentration (PS: g / L as S), and the horizontal axis represents Test Examples 1 No. 1 to 5. Figure 8B shows the relationship between the R, G, and B values ​​and the polysulfide concentration in Test Examples 1 No. 1 to 5. The right vertical axis represents the R, G, and B values, the left vertical axis represents the polysulfide concentration (PS: g / L as S), and the horizontal axis represents Test Examples 1 No. 1 to 5. [Figure 9] Figures 9A, B, and C show the correlation between the relative R, G, and B light reception amounts and the polysulfide concentration, as well as the correlation coefficient, in Test Examples 1, Nos. 1-5. The vertical axis represents the polysulfide concentration (PS: g / L as S), and the horizontal axis represents the R, G, and B relative light reception values. Figure 9A shows the relationship between the R relative light reception amount and the PS concentration. Figure 9B shows the relationship between the G relative light reception amount and the PS concentration. Figure 9C shows the relationship between the B relative light reception amount and the PS concentration. [Figure 10] This is a block diagram that simply illustrates the processing steps of a typical specialized AI. [Modes for carrying out the invention]

[0018] The following describes embodiments for carrying out the present invention. The embodiments described below are merely examples of representative embodiments of the present invention and should not be interpreted as limiting the scope of the invention. These embodiments will be described in the following order.

[0019] 1. White liquor treatment method according to this embodiment 1-1. White liquor treatment system according to this embodiment 1-2. White liquor treatment method according to this embodiment 1-2-1. Monitoring the color of the white solution 1-2-2. Color Data Processing 1-2-3. Polysulfide generation process 1-2-4. Controlling the state of the white liquor 1-2-5. Example of this embodiment 2. Apparatus and systems for white liquor treatment 3. Overview of the pulp manufacturing system using the white liquor treatment method in this embodiment 4. About this technology

[0020] 1. White liquor treatment method according to this embodiment

[0021] This embodiment provides a method for treating white liquor in pulp manufacturing by monitoring the color tone of the white liquor and controlling its state based on that color tone. This white liquor treatment method may also be a method for controlling or managing the white liquor treatment. Furthermore, this embodiment provides a white liquor treatment method that includes a white liquor state control step, which involves monitoring the color tone of the white liquor in pulp manufacturing and controlling the state of the white liquor based on its color tone. In this embodiment, the "white liquor in pulp production" is preferably the "white liquor used in the pulping process of pulp production," and the monitored "white liquor used in the pulping process of pulp production" is more preferably the white liquor from the quenching and causticization system to the pulping system.

[0022] This embodiment provides a technology that allows for the most accurate understanding of the state of the white liquor. Furthermore, this embodiment allows for the most real-time and accurate understanding of the sodium polysulfide concentration in the white liquor. In addition, the ability to more accurately understand the state of the white liquor leads to more stable operation, and the ability to more accurately understand the state of the white liquor (preferably the polysulfide concentration and polysulfide formation) leads to more stable operation. By operating stably, it becomes possible to suppress the decrease in chemical pulp yield, and to stabilize pulp yield or pulp production by suppressing the decrease in pulp yield.

[0023] The white liquor treatment method may be one or more selected from (a) a method for stabilizing, improving, or suppressing the decrease in kraft pulp yield or a method for stabilizing, improving, or suppressing the decrease in pulp yield in the pulping process, (b) a method for generating, preparing, or adjusting the concentration of polysulfides in the white liquor, (c) a method for producing or preparing white liquor, or a method for controlling the white liquor oxidation treatment, (d) a method for estimating the polysulfide concentration in the white liquor, or (e) a monitoring system for these methods or a white liquor oxidation monitoring system, or a combination thereof. Furthermore, the control means in this embodiment can be in a state where it can access other means. These other means are not particularly limited and may be internal or external means such as the same device as the control means. Preferably, they include, but are not limited to, one or more selected from, color measuring means such as an optical sensor, oxygen supply means for adjusting the amount of air supplied to the polysulfide formation reaction, temperature control means, additive adding means, and external storage means (server, cloud, etc.).

[0024] In the description of the example of the white liquor treatment method in this embodiment, explanations of each component and each treatment method, such as white liquor, monitoring of the white liquor's color tone, color tone data processing, color tone data, color tone processing data, polysulfide concentration estimation model (estimation formula), polysulfide generation process, control of the white liquor state, and control unit, which overlap with the content described later (for example, "2.", "3.", "4.", etc.), may be omitted as appropriate. However, the explanations in "2." to "4.", etc., also apply to this embodiment and can be adopted as appropriate. In addition, in the description of the example of the white liquor treatment system and white liquor treatment method in this embodiment, the explanations in "2." to "4.", etc., described later can be applied to this embodiment and can be adopted as appropriate.

[0025] 1-1. White liquor treatment system according to this embodiment

[0026] An example of one embodiment of the white liquor treatment according to this embodiment will be described with reference to Figures 1 to 10, etc., but the present invention is not limited thereto. An outline of a white liquor treatment system to which the white liquor treatment method according to the present invention is applied (preferably a system for treating white liquor used in the pulping process) will be briefly described below, but the present invention is not limited thereto and can be applied to various white liquor treatment systems according to the specific site.

[0027] For example, referring to Figure 1, the white liquor treatment system according to this embodiment preferably includes a white liquor treatment system 100 for monitoring and / or controlling the state of the white liquor in order to treat the white liquor containing sulfide salts and hydroxide salts from the quenching and caustication system 40 into a white liquor containing polysulfides to be used in the pulping system 10 (pulping process). Examples of sulfide salts, hydroxide salts, and polysulfide salts include alkali metals such as sodium and potassium, and alkaline earth metals, but alkali metals (more preferably sodium) are preferred.

[0028] The white liquor processing system according to this embodiment may include a white liquor color measurement system that monitors the state of the white liquor (preferably the state of the white liquor subjected to the pulping process) and measures the color tone of the white liquor, and a white liquor state control system that controls the state of the white liquor based on the measured value of the white liquor color tone.

[0029] The white liquor state control system according to this embodiment preferably monitors the white liquor in pulp manufacturing and controls the white liquor state based on color data (preferably color processing data) obtained by measuring the color tone of the white liquor. Furthermore, the white liquor state control system according to this embodiment may include a white liquor monitoring system for monitoring the white liquor in pulp production, a color data analysis system for analyzing the color data of the white liquor obtained from the monitoring results, and a polysulfide production adjustment system for adjusting the polysulfide concentration in the polysulfide production process based on the monitoring results, and may include one or more of these. Furthermore, in the white liquor state control system according to this embodiment, the white liquor is preferably the white liquor used in the pulping process of pulp production. Furthermore, the white liquor state control system according to this embodiment may control or manage one or more selected from a white liquor color monitoring system, a white liquor color data analysis system, a white liquor polysulfide concentration estimation system, and a white liquor polysulfide generation adjustment system.

[0030] The white liquor treatment system 100 according to this embodiment can be connected to various locations, parts, and systems via lines (e.g., flow paths, piping, etc.). For example, the quenching / caustication system 40, the white liquor treatment system 100, and the pulping system 10 can be connected via lines. The white liquor containing sulfides and hydroxides from the quenching / caustication system 40 is preferably the white liquor from the white liquor clarifier 42 or the white liquor tank 43. In the pulping system 10, it is preferable to use the white liquor to produce pulp slurry or pulp kraft from the raw material, wood chips.

[0031] A preferred flow of this embodiment is as follows: white liquor (containing sodium sulfide and sodium hydroxide) from the scavenging / caustic system 40 flows into the white liquor treatment system 100 as a raw material for the pulping agent; the white liquor that flows into the white liquor treatment system 100 is treated in a polysulfide formation step (preferably an oxidation reaction step) to generate polysulfides in the white liquor, which is then treated into white liquor (containing a predetermined concentration of sodium polysulfide), and the white liquor is discharged into the pulping system; and the discharged white liquor is used as the pulping agent in the pulping system (see, for example, Figures 1 to 3).

[0032] In this embodiment, it is preferable to measure the color tone of the white liquor in the polysulfide formation process, and monitoring of this formation process may include not only during the formation process, but also before inflow into the formation process and / or after outflow from the formation process. Furthermore, in this embodiment, it is preferable to measure the color tone of the white liquor before inflow into the polysulfide formation process and / or after outflow at the same time or at separate times (see, for example, Figures 2 and 3). In this embodiment, it is preferable to determine the polysulfide concentration or estimated polysulfide concentration in the white liquor in the polysulfide formation process based on the white liquor color tone measurement results and to control the state of the white liquor.

[0033] 1-2. White liquor treatment method according to this embodiment

[0034] The white liquor treatment method according to this embodiment is preferably used to monitor the color tone of the white liquor in pulp production and to control the state of the white liquor based on that color tone. More specifically, the white liquor in pulp production is preferably the white liquor used in the pulping process of pulp production. The white liquor treatment is preferably performed in the polysulfide formation process (preferably the oxidation reaction process) in the white liquor, by treating the white liquor from the sequestering and causticization system (the white liquor contains sulfide salts and hydroxide salts) to a white liquor containing polysulfides used in the pulping process.

[0035] In this embodiment, it is preferable to monitor the state of the white liquor (preferably adjusting the polysulfide concentration in the white liquor) by monitoring and / or measuring the color tone and further combining it with the amount of light received. This makes it possible to more accurately understand the state of the white liquor (preferably the polysulfide concentration) in the polysulfide generation process and to operate stably.

[0036] The white liquor treatment method according to this embodiment preferably includes: monitoring the color tone of the white liquor with a white liquor color tone measuring device; acquiring color tone processing data (preferably conversion or processing data, etc.) related to controlling the state of the white liquor based on the color tone data (preferably color tone measurement data) of the white liquor; and adjusting the formation of polysulfides in the white liquor based on the acquired color tone processing data. It is more preferable that these monitoring, acquisition of color tone processing data, and adjustment of polysulfide formation are included in a control step for controlling the state of the white liquor.

[0037] The aforementioned color tone is preferably white liquor color tone data obtained by measuring the color tone of the white liquor used in the pulping process of the pulp manufacturing, and it is even more preferable to control the state of the white liquor from said color tone data. The aforementioned color tone is preferably white liquor color tone data (preferably color tone measurement data, color tone processing data) obtained by measuring the color tone of the white liquor used in the pulping process of the pulp manufacturing process, and it is even more preferable to control the state of the white liquor from said color tone data.

[0038] In this embodiment, the color processing data is preferably data obtained by processing (converting, modifying, etc.) color data (preferably color measurement data) so that it can be used or participate in controlling the state of the white liquor. Furthermore, the color processing data is preferably processed and acquired based on the white liquor color measurement data.

[0039] The aforementioned color data (preferably color processing data) is preferably an estimated value of the R, G, B relative light reception amount of the white liquor and / or the polysulfide concentration in the white liquor. In this embodiment, the R, G, B relative light reception amount of the white liquor refers to one or more selected from the R relative light reception amount of the white liquor, the G relative light reception amount of the white liquor, and the B relative light reception amount of the white liquor. The relative R, G, and B light-receiving amounts of the white liquor preferably have a statistical relationship (preferably a correlation) with the polysulfide concentration in the white liquor, and more preferably have a negative correlation with the polysulfide concentration in the white liquor. It is more preferable that the color tone data is one or more selected from the group consisting of the R relative light reception amount of the white liquid and the G relative light reception amount of the white liquid, and more preferably the R relative light reception amount of the white liquid.

[0040] The control of the state of the white liquor is preferably carried out in the polysulfide formation process. The control of the state of the white liquor is preferably carried out by controlling the polysulfide formation reaction or the polysulfide formation process, and is also preferably carried out by controlling the polysulfide concentration in the white liquor, the polysulfide formation reaction in the white liquor, or the oxidation reaction of the white liquor.

[0041] Furthermore, the control of the state of the white liquor is preferably performed by controlling the state of the white liquor so that the excess or deficiency of the polysulfide concentration in the white liquor falls within a predetermined or set range. This control is preferably performed based on the color tone or color tone data (preferably color tone measurement data, color tone processing data) of the white liquor, or based on a polysulfide concentration estimation model in the white liquor (preferably the estimated concentration of polysulfides in the white liquor).

[0042] The control of the state of the white liquor is preferably by one or more selected from the group consisting of adjustment of the addition amount of aids (preferably sulfide, oxidant) to the white liquor, adjustment of the temperature of the white liquor, and adjustment of the oxygen supply amount to the white liquor. Among these, the adjustment of the oxygen supply amount is more preferable because it is easier to control the oxidation reaction more simply.

[0043] 1-2-1. Monitoring of the color tone of white liquor In the method for treating white liquor of the present embodiment, it is preferable to monitor the color tone of the white liquor. The white liquor is preferably the white liquor used in the cooking step of pulp production. Thereby, the treatment status of the white liquor state in the polysulfide generation step can be grasped quickly and accurately, the state of the white liquor (preferably the polysulfide concentration) can be grasped more accurately, and stable operation can be performed.

[0044] The color tone of the white liquor is not particularly limited, but it is preferably a color tone of a color system that can be numerically expressed. As the color system, either a mixed color system or a dominant color system may be used, but it is preferable to use the CIE color system. As the CIE color system, for example, RGB system, XYZ color system, L * a * b * color system, L * u * v * color system, etc. may be mentioned, but it is not limited thereto. Among these, one or more selected from the RGB system, XYZ color system, and L * a * b * color system are more preferable.

[0045] Also, these CIE color systems can be converted into each other as necessary. For example, it is possible to convert from the RGB system color tone to the XYZ color system color tone or the L * a * b * color system color tone, etc., and it is also possible to convert from the XYZ color system color tone, etc. to the L * a * b * color system color tone, etc., and the reverse conversion is also possible. Therefore, in this embodiment, L is selected from the RGB color system color tone obtained as the color tone of the white liquid. * a * b * Convert to a color system and tones, and the converted L * a * b * The state of the white solution may be controlled by a color system or other means, L * a * b * The color system tones may be converted to RGB color systems, and the state of the white solution may be controlled using the converted RGB color systems.

[0046] The aforementioned color tone of the white liquid is preferably white liquid color tone data (preferably white liquid measurement data) obtained by measuring the color tone of the white liquid. More specifically, when monitoring the color tone of the white liquid, the color tone of the white liquid can be measured by a white liquid color tone measuring device, which will be described in detail later, and this measured value can be obtained as color tone data of the color system. After obtaining the color tone data, the color tone measuring device may transmit the color tone data to the control device or store it in an internal or external storage unit. The color tone measuring device can be appropriately set at the color tone monitoring location described below. Note that the device in this embodiment may be a unit, system, or means, etc.

[0047] It is preferable to monitor the color of the white liquid over time, thereby obtaining the color of the white liquid over time. Obtaining the color over time makes it easier to control the state of the white liquid more accurately. The color tone of the white liquid may be monitored continuously or intermittently (preferably at regular intervals). These "regular intervals" may be, for example, 1 to 60-minute intervals or 5 to 20-minute intervals. By monitoring at regular intervals, the amount of data acquired can be reduced, and the processing speed of the control unit can be improved.

[0048] The white liquor to be monitored may be any white liquor at any location or in any part of the process from the quenching / caustication system to the pulping system, as described in <1-1. White Liquor Processing System According to This Embodiment> above, and the polysulfide formation system is included between the quenching / caustication system and the pulping system. More specifically, the white liquor to be monitored may be one or more white liquors selected from white liquor after the quenching / caustication system, such as in a white liquor clarifier or white liquor tank, white liquor in the polysulfide formation device, white liquor before the pulping system, and white liquor in each line connecting them (e.g., flow path, piping, etc.).

[0049] The white liquor to be monitored is more preferably the white liquor from the suffocation / caustication system to before the pulping system. More preferably, one or more types selected from the following are suitable: the white liquor in the inflow line to the polysulfide generation apparatus (transfer line from the suffocation / caustication system), the white liquor inside the polysulfide generation apparatus, and the white liquor in the outflow line from the polysulfide generation apparatus (transfer line to the pulping system). Even more preferably, one or more types of white liquor selected from the white liquor inlet, white liquor outlet, and transfer lines near these inlets or outlets provided in the polysulfide generation apparatus are more suitable. Even more preferably, the white liquor inlet and / or white liquor outlet, or its vicinity, more preferably the white liquor outlet or its vicinity, with the white liquor outlet being even more preferable. More preferably, the timing is "immediately after" the inflow or outflow of the white liquor, and "immediately after" this inflow or outflow is more preferably within about 2 hours before inflow or within about 2 hours after outflow, even more preferably within about 1 or 0.5 hours before inflow or within about 1 or 0.5 hours after outflow, for example, a suitable "immediately after" outflow is within 2 hours after outflow.

[0050] The location for monitoring the color of the white liquid may be any of the locations or parts of the white liquid processing system described above. The number of color monitoring locations for the white liquor is not particularly limited and may be one or two or more. By having multiple color monitoring locations, it becomes easier to understand the state of the white liquor, making it easier to control it to achieve a more appropriate state (preferably, a more appropriate polysulfide concentration in the white liquor). Furthermore, when monitoring the white liquor over time, the white liquor at the same location may be monitored over time, or white liquor at different locations may be monitored over time. Preferably, color data (preferably color measurement data and color processing data) is obtained over time from the white liquor at the same location. This is preferable because it makes it easier to accurately monitor or predict the color change of the white liquor (preferably the white liquor before and after the polysulfide formation process) over time. Based on such color data over time, the state of the white liquor can be controlled more appropriately.

[0051] Furthermore, when monitoring the white liquor, it is possible to monitor it from any direction in the X, Y, or Z directions, but it is preferable to monitor it from above (Z-axis direction, vertical direction). Also, when monitoring the white liquor, it is preferable to monitor the color tone of the white liquor from a predetermined distance (interval) from the white liquor (preferably the liquid surface or measuring surface). This predetermined distance can be appropriately adjusted depending on the performance of the device and the condition of the white liquor, but for example, 0 to 1000 mm is preferable, more preferably 30 to 500 mm, and even more preferably 50 to 200 mm. In addition, when monitoring the white liquor, a color tone monitoring line (e.g., a bypass line) for flowing in and monitoring the white liquor may be provided at each location or part of the white liquor processing system. In this case, it is preferable to flow in white liquor near the liquid surface (for example, between the liquid surface and about 50 cm above the liquid surface). This makes it easier to monitor the white liquor and to adjust the temperature of the white liquor.

[0052] A white liquor color measuring device (e.g., a color sensor) can be installed at the location where the white liquor color is monitored. This allows for easy, continuous, or over-the-counter monitoring of white liquor that would otherwise be difficult to analyze manually, such as when dealing with strong alkalis, corrosive components, and odorous components. Furthermore, by employing a non-contact method, this white liquor color measuring device does not require contact with the white liquor, making it easy to install in the white liquor processing system.

[0053] The pH and temperature of the white liquor being monitored are not particularly limited, but the pH of the white liquor (at 20°C) is preferably 12 or higher, more preferably 13 or higher. Furthermore, the temperature of the white liquor to be monitored is preferably 4°C or higher, more preferably 30°C or higher, and even more preferably 40°C or 50°C or higher as a suitable lower limit, and preferably 100°C or lower, more preferably 90°C or lower, even more preferably 80°C or lower, and even more preferably 70°C or lower as a suitable upper limit from the viewpoint of suppressing the decomposition of polysulfides. Furthermore, the preferred pH and temperature of the white liquor being monitored may also be the preferred pH and temperature in the polysulfide formation process.

[0054] 1-2-2. Color Data Processing In the white liquor processing method of this embodiment, it is preferable to process (convert, modify, etc.) the color tone acquired by the monitoring into color tone data. In the white liquor treatment method of this embodiment, it is preferable to process and acquire color treatment data related to the control of the state of the white liquor based on color data (preferably white liquor color measurement data). By using this color treatment data, the state of the white liquor can be grasped more accurately, leading to stable operation.

[0055] The color tone or color tone data of the white liquor is not particularly limited, but is preferably white liquor color tone measurement data obtained by measuring the color tone of the white liquor in the pulp manufacturing process. The white liquor is preferably the white liquor used in the digestion process of pulp manufacturing. In a more preferred embodiment, the color tone or color tone data of the white liquor is color tone processing data that has been processed (e.g., processed, converted, etc.) by a control unit or the like based on the obtained white liquor color tone measurement data.

[0056] The color tone or color tone data (preferably color tone processing data) of the white liquid is preferably the color tone or color tone data of the white liquid flowing into the polysulfide production process, and / or the color tone or color tone data of the white liquid flowing out from the polysulfide production process. The aforementioned color tone data of the white liquor (preferably color-processed data) is preferably color tone data that is related to (preferably statistically related, more preferably correlated) with the polysulfide concentration in the white liquor. More preferably, specific examples include one or more selected from the R, G, B relative light reception amount of the white liquor and the estimated polysulfide concentration in the white liquor, but is not particularly limited to these.

[0057] In this embodiment, it is preferable to estimate the polysulfide concentration in the white liquor based on the color tone or color tone data (preferably color tone processing data) of the white liquor. In a more preferable embodiment, it is preferable to obtain an estimated concentration of polysulfides in the white liquor based on the color tone or color tone data (preferably color tone processing data) of the white liquor, and even more preferably, to estimate the polysulfide concentration in the white liquor from the color tone measurement results using an estimation model or estimation formula for estimating the polysulfide concentration in the white liquor, and even more preferably, to adjust the generation of the polysulfide concentration in the white liquor based on the obtained estimated result (estimated value) and set value (target value, objective value) of the polysulfide concentration in the white liquor. In this embodiment, it is preferable to set the above-mentioned set value (target set value) to a value that falls within a suitable range for the polysulfide concentration of the white liquor, depending on the conditions of the white liquor treatment at the site (e.g., for each machine, for each season).

[0058] As shown in the examples below, the inventors have found that the polysulfide concentration in the white liquor can be determined more accurately by using the relative R, G, B light-receiving values, which are color-processed data obtained by processing (converting, modifying) the color-measurement data, rather than using the R, G, B values, which are color-measurement data obtained from the color-measurement results of the white liquor. This allows for continuous image analysis of the color tone of the white liquor, and by understanding the operating status of the pulp production system (preferably the pulp chemical solution generation system and the pulp system) from the color tone of the white liquor and controlling it in real time, the pulp production system (preferably the pulp chemical solution generation system, the pulp system, and the kraft pulp method) can be stabilized.

[0059] In this specification, the "relative R, G, and B light reception amounts" can be calculated and obtained using the following formulas: R relative light reception amount = total light reception amount × R value / (R value + G value + B value); G relative light reception amount = total light reception amount × G value / (R value + G value + B value); B relative light reception amount = total light reception amount × B value / (R value + G value + B value). Furthermore, since the relative R, G, and B light reception amounts used in this embodiment do not use complex mathematical formulas, the amount of data and the burden of data processing are small, and it is possible for operators (humans) to easily calculate and input them into devices as appropriate, and verification is also easy, which are excellent advantages.

[0060] Furthermore, the inventors have found that there is a statistical relationship (specifically, a negative correlation) between the color processing data of the relative R, G, and B light reception amounts (more preferably, the relative R light reception amount and the relative G light reception amount) and the polysulfide concentration in the white liquor. By discovering this statistical relationship, the inventors have made it possible to measure the color tone of the white liquor, process (convert or modify, etc.) the color tone measurement results into relative R, G, and B light reception amounts, and then more accurately determine the polysulfide concentration in the white liquor or the estimated polysulfide concentration in the white liquor based on the obtained relative R, G, and B light reception amounts.

[0061] The inventors have discovered a statistical relationship (specifically, a correlation) between color data and polysulfide concentration in the white liquor, and have found that a model (estimation formula) for estimating polysulfide concentration in the white liquor can be obtained. By using this estimation model, the polysulfide concentration in the white liquor at the site (preferably the polysulfide concentration in the white liquor during the polysulfide generation process) can be estimated more accurately and simply from color processing data (relative R, G, B light reception, etc.) from measured values. Furthermore, by measuring the color data of the white liquor and the polysulfide concentration in the white liquor for each white liquor treatment situation (for each machine, each season, etc.) used in the actual pulp manufacturing digestion process, a model (estimation formula) for estimating polysulfide concentration in the white liquor can also be obtained. By using such situation-specific estimation models (estimation formulas), the situation of white liquor treatment in actual pulp manufacturing (for each machine, each season, etc.) can be grasped as accurately as possible, and responses can be made more precise for each situation.

[0062] In a preferred embodiment of this design, the state of the white liquor can be controlled more accurately by comparing the estimated polysulfide concentration in the white liquor obtained from color processing data processed from actual measured values ​​with a preferred set value (target value) for the polysulfide concentration in the white liquor. This allows for a more accurate understanding and control of the state of the white liquor. The fact that this set value can be set according to the conditions of the white liquor treatment at the site (each machine, each season, etc.) is a significant advantage of this design, as it allows for a more responsive approach to the actual situation. Furthermore, the set value in this design may be a characteristic item (feature quantity) that has a statistically related relationship (preferably a correlation) with the polysulfide concentration. For this reason, the set value of the polysulfide concentration may be converted into numerical values ​​of characteristic items related to it (for example, relative R, G, B light reception, air supply rate, etc.) using a statistically related (preferably correlated) mathematical formula (such as a simple regression equation).

[0063] The set value for the polysulfide concentration in the white liquor is preferably a value set as a target or desired value for a suitable polysulfide concentration in the white liquor, and a suitable polysulfide concentration, such as a target value, can be appropriately set according to the conditions of the white liquor treatment at the site.

[0064] The set value (g / L as S) for the polysulfide concentration is not particularly limited, but a suitable lower limit is preferably 3.0 or higher, more preferably 3.5 or higher, even more preferably 4.0 or higher, and a suitable upper limit is preferably 10 or lower, more preferably 9 or lower, even more preferably 8 or lower, more preferably 7 or lower, more preferably 6 or lower, more preferably 5.5 or lower, and even more preferably 5.0 or lower. From the viewpoint of the air oxidation PS pulping method, the suitable numerical range is preferably 4 to 6, and a more preferable upper limit is 5 to 6 or lower. Considering the polysulfide generation method at the site, the pulping chemical production equipment, and its generation capacity (such as the upper limit of generation), a suitable concentration range may be set according to the conditions of the white liquor treatment at the site. For example, in the air oxidation PS pulping method, the upper limit is usually said to be around 5-6 g / L as S, and in the white liquor electrolytic PS pulping method, the upper limit is usually said to be around 10 g / L as S.

[0065] Furthermore, in this embodiment, it is possible to set values ​​other than the polysulfide concentration in the white liquor described above as the setting value (target setting value) for comparison with the color tone or color tone data (preferably color tone processing data), and it is preferable to use characteristic items (feature quantities) that have a statistically related relationship (preferably correlation) with the polysulfide concentration in the white liquor. For example, the polysulfide concentration in the white liquor set as the target setting value may be processed (converted or modified) into R, G, B relative light reception amounts, and the obtained R, G, B relative light reception amounts may be used as the target setting value. This makes it possible to compare the R, G, B relative light reception amounts obtained from the measurement results with the target setting value of the R, G, B relative light reception amount without having to further process the data from time to time. As a result, further data processing steps can be omitted, skipped, or reduced, thereby reducing the data processing load, such as the amount of data and data processing.

[0066] Furthermore, data for determining the statistical relationship between each characteristic item (each feature quantity), such as the relationship between the color tone of the white liquor used in this embodiment (preferably the relative R, G, B light reception) and the polysulfide concentration in the white liquor, can be obtained using statistical processing such as multivariate analysis, depending on the conditions of the white liquor treatment at the site (each machine, each season, etc.). For this reason, instead of being bound by specific mathematical formulas like those shown in Figures 8 and 9 of the [Examples] section below, it is possible to obtain a model or mathematical formula (e.g., a simple regression equation) by multivariate analysis (e.g., regression analysis) using measured values ​​(features) obtained according to the conditions of the white liquor treatment at the site (actual machine, season, temperature, climate, raw pulp, etc.), and then appropriately adopt the obtained model or mathematical formula (e.g., an estimated model). In addition, as a sample, in addition to the white liquor from the actual machine at the site, a simulated white liquor (more specifically, a simulated white liquor with different polysulfide concentrations before and after oxidation, etc.) may be used. For example, the measured color data of the sample (preferably color-processed data) and the polysulfide concentration data in the white liquor may be analyzed using multivariate analysis to obtain a model or formula (e.g., a simple regression equation) of the correlation between these, which can then be used as an estimation model or formula.

[0067] In this embodiment, the method for measuring the polysulfide concentration in the white liquor is not particularly limited, but a method that can be used to determine the statistical relationship (preferably correlation) with the color data of the white liquor is desirable, and known or future methods for measuring the polysulfide concentration in the white liquor or analytical methods for sodium polysulfide pulverized solutions can be appropriately adopted. For example, methods for analyzing sulfur polysulfide that constitutes sodium polysulfide (Patent Document 1: Japanese Patent Publication No. H07-92148), acid titration methods commonly used for quantitative analysis of sodium sulfide and sodium hydroxide in white liquor, methods for performing acid titration by adding formalin to sodium polysulfide pulverized solution, two-step analytical methods using mercury compounds and potentiometric titration, methods for measuring the absorbance of elemental sulfur that constitutes sulfur polysulfide at a wavelength of 370 nm, and analytical methods for each component ion that makes up sodium polysulfide (Patent Document 2: Japanese Patent Publication No. Hei 06-027095) are examples, but the method is not particularly limited to these.

[0068] In this embodiment, it is more preferable to use an estimation model of the white liquor state (preferably an estimation model of the polysulfide concentration in the white liquor) (e.g., an estimation formula) derived from the statistical relationship or relationship between "color data (preferably color processing data)" and "polysulfide concentration in the white liquor." These relationships and estimation models may be used as appropriate by the user, or they may be pre-stored in the memory unit of the white liquor processing device or system, or in the cloud or on a server, and accessed and transmitted to the memory unit as needed by the control unit, or they may be appropriately input by the operator to the control unit or the white liquor processing device or system when using the white liquor processing device. Furthermore, in this embodiment, the "polysulfide concentration in the white liquor" and the "production reaction, oxidation reaction (more preferably, oxygen supply, even more preferably, air supply amount)" are further defined as characteristic items (characteristic quantities), and an estimation model of the white liquor state (preferably, an estimation model of the polysulfide production reaction in the polysulfide production process) (e.g., an estimation formula, etc.) obtained from the relationship between these may be used in combination with the estimation model of the polysulfide concentration in the white liquor, and this estimation model or estimation formula can be obtained as follows. Based on this estimation model of the polysulfide production reaction (preferably the oxidation reaction) in the polysulfide production process, the production reaction (preferably the oxidation reaction, more preferably the oxygen supply, even more preferably the air supply amount) can be adjusted or controlled to achieve a predetermined polysulfide concentration by performing the production reaction (preferably the oxidation reaction, more preferably the oxygen supply, even more preferably the air supply amount) to achieve the target set value, and in this case, it is preferable to set or fix the temperature so that it is within a suitable temperature range. The items of the target set value are preferably the same as the items of the characteristic items (e.g., polysulfide concentration in the white liquor, air supply amount, etc.). Suitable estimation formulas include, for example, regression equations (y=ax+b: y is the air supply rate, x is the polysulfide concentration (g / L as S), a is the slope, b is the intercept, and there is a positive correlation).

[0069] The estimation model for the white liquor state (preferably, the estimation model for the polysulfide concentration in the white liquor) is preferably obtained by statistical processing, as described above, to match the actual equipment. The estimation model can be obtained using known or future statistical processing methods. For example, a regression equation (y = -ax + b: y is the relative light reception amount of R, G, B, which are color processing data, x is the polysulfide concentration (g / L as S), a is the slope, b is the intercept, and there is a negative correlation) as shown in the example below can be used. The estimation model or estimation formula for the white liquor state in this embodiment can be obtained and used by appropriately employing simple regression analysis, multiple regression analysis, multivariate analysis, etc. Note that the width of the slope a of the simple regression equation used in the estimation formula may be set to the slope a ± 0.005 obtained by actual measurement, and the width of the intercept b of the estimation formula may be set to the intercept b ± 0.5 obtained by actual measurement.

[0070] Furthermore, by using the estimation model or estimation formula for the white liquor state (preferably polysulfide concentration) in this embodiment, the set value (target value) of the polysulfide concentration in the white liquor can be processed (converted or modified, etc.) into R, G, B relative light reception amounts, and the set value (target value) of the R, G, B relative light reception amounts can be obtained. It is also possible to compare this set value (target value) of the R, G, B relative light reception amounts with the R, G, B relative light reception amounts, which are color-processed data processed from the measured color tone measurement data of the white liquor. This eliminates the need to process (convert or modify) the measured values ​​into polysulfide concentration in the white liquor over time or continuously, thereby reducing the amount of data and the data processing load. Note that processing such as conversion or modification may be performed not only on the items of R, G, B relative light reception amounts and polysulfide concentration, but also on characteristic items (features) that have a high statistical correlation (e.g., correlation).

[0071] Furthermore, in this embodiment, an estimation model or estimation formula of this embodiment may be created using statistical processing or the like from each characteristic item (feature quantity) using AI learning or the like. Examples of such feature quantities include, but are not limited to, the "color tone of the white liquor (preferably color tone processing data)" and the "polysulfide concentration in the white liquor," such as the white liquor at the site or a simulated white liquor.

[0072] 1-2-3. Polysulfide generation process In the white liquor treatment method of this embodiment, it is preferable to control the state of the white liquor (preferably by adjusting the formation of polysulfides in the white liquor) based on the color tone or color tone data (preferably color tone treatment data). The color tone treatment data is preferably color tone treatment data related to the control of the state of the white liquor obtained based on the color tone measurement data of the white liquor, and more preferably is the estimated value of the R, G, B relative light reception amount of the white liquor and / or the polysulfide concentration in the white liquor. The white liquor is preferably the white liquor used in the pulping process of pulp manufacturing.

[0073] The polysulfide production process used in this embodiment (for example, a polysulfide production method, a method for preparing the white liquor (polysulfide pulping agent), etc.) is preferably a known or future polysulfide production process or method.

[0074] The location of production of the white liquor (also called "polysulfide pulping solution") is not particularly limited. For example, it may be produced by carrying out a polysulfide production process or method in the digester. However, from the viewpoint of preventing peeling reactions, it is preferable to produce the white liquor (polysulfide pulping solution) by providing a polysulfide production process or apparatus and using it in the digester. For example, it is preferable to provide a polysulfide production process between the suffocation / caustication system 40 and the pulping system 10 (see Figures 1-3). The white liquor from the suffocation / caustication system contains sodium sulfide and sodium hydroxide circulating in the pulp production system. In the polysulfide production process, it is preferable to use these sodium sulfide and sodium hydroxide contained in the white liquor from the suffocation / caustication system as raw materials for polysulfides and carry out a polysulfide production reaction using them so that the polysulfides reach a set concentration, thereby producing a white liquor (polysulfide pulping solution) of the target set value (set concentration).

[0075] The method for producing polysulfides is not particularly limited, but examples include adding elemental sulfur to the white liquor, oxidizing the white liquor (preferably by air oxidation), and electrolysis of the white liquor. One or more of these methods can be used. This embodiment has the advantage of being applicable to the oxidation treatment method of white liquor, which is commonly used in pulp manufacturing. As a method for generating polysulfides, it is preferable to use an oxidation treatment method of white liquor (preferably an air oxidation method). Furthermore, the sodium sulfide concentration (as Na2O) of the white liquor before the polysulfide formation step is not particularly limited, but its preferred lower limit is preferably 5 g / L (as Na2O) or more, more preferably 10 g / L (as Na2O) or more, and its preferred upper limit is preferably 60 g / L (as Na2O) or less, more preferably 50 g / L (as Na2O) or less. The sodium hydroxide concentration (as Na2O) of the white liquor before the polysulfide formation step is not particularly limited, but its preferred lower limit is preferably 15 g / L (as Na2O) or more, more preferably 20 g / L (as Na2O) or more, and its preferred upper limit is preferably 100 g / L (as Na2O) or less, more preferably 90 g / L (as Na2O) or less. The temperature of the white liquor during the polysulfide formation reaction is not particularly limited, but is preferably 4 to 100°C, and more preferably 40 to 90°C. The pH of the white liquor during the polysulfide formation reaction is not particularly limited, but is preferably 12 or higher, and more preferably 13 or higher.

[0076] The air oxidation method of white liquor has the advantage of making it easier to maintain the balance of circulating Na and S in the Kraft process compared to the method of adding additives to the white liquor, and by supplying oxygen (air) to the white liquor, polysulfides can be easily obtained from sodium sulfide.

[0077] While not particularly limited, a suitable method for air oxidation of white liquor is to use a solid catalyst such as activated carbon to air-oxidize the sodium sulfide in the white liquor to obtain sodium polysulfide. Suitable catalysts include activated carbon particles with a hydrophilic surface. The MOXY (Mead Oxidation) method is commonly used for air oxidation of white liquor.

[0078] As a method for controlling the oxidation treatment of the white liquor (preferably the air oxidation method of the white liquor), one or more methods selected from temperature control, oxygen supply adjustment, and auxiliary agent (such as oxidation catalyst) adjustment are recommended. As a method for controlling the air oxidation method of the white liquor, one or more methods selected from temperature control and oxygen supply adjustment are preferred.

[0079] In this embodiment, it is preferable to control the state of the white liquor more easily by mainly controlling the adjustment of oxygen supply in the air oxidation method based on the color data (preferably color processing data), and to adjust the polysulfide concentration in the white liquor more easily so that it reaches the target set value. For oxygen supply, one or more types can be selected based on factors such as oxygen concentration and oxygen supply rate. Typically, inexpensive and easy-to-handle air is used, resulting in an oxygen concentration of around 20%. Therefore, it is desirable to adjust the polysulfide concentration by increasing or decreasing the oxygen supply rate. To adjust the oxygen supply, it is preferable to adjust the air-white liquor ratio. If the conversion rate to polysulfides (polysulfide concentration in the white liquor) is high, it is preferable to decrease the proportion of air, and if it is low, it is preferable to increase the proportion of air. The oxygen supply rate (preferably air supply rate) Nm3 / H (unit) is equal to the amount of white liquor m 3 The ratio is not particularly limited, but a preferred lower limit is preferably 0.5 or more, more preferably 1 or more, and a preferred upper limit is preferably 3 or less, more preferably 2 or less.

[0080] While there are no particular limitations on temperature control, it is preferable to adopt a temperature range that is normally used in on-site white liquor oxidation treatment methods, as the polysulfide formation reaction can be promoted or suppressed by adjusting the oxygen supply. If the temperature falls outside this range, it is preferable to adjust the temperature to bring it within that range. Furthermore, in the white liquor treatment method of this embodiment, it is preferable to adopt a normal temperature range that is used in on-site white liquor oxidation treatment methods. This allows the promotion or suppression of the polysulfide formation reaction to be controlled by adjusting the oxygen supply, thereby simplifying the factors or number of steps in the oxidation treatment.

[0081] 1-2-4. Controlling the state of the white liquor

[0082] In the white liquor treatment method of this embodiment, the state of the white liquor is preferably controlled by monitoring the color tone of the white liquor in pulp production and controlling the state of the white liquor based on that color tone. The white liquor is preferably the white liquor used in the pulping process of pulp production. The control of the state of the white liquor is preferably achieved by controlling the state of the white liquor (polysulfide pulping agent) in the polysulfide production process. The control of the state of the white liquor is preferably achieved by controlling the polysulfide formation reaction or the polysulfide formation process, or by controlling the polysulfide concentration in the white liquor, the polysulfide formation reaction in the white liquor, or the oxidation treatment or oxidation reaction of the white liquor.

[0083] The control of the state of the white liquor is preferably one or more selected from the group consisting of adjusting the oxygen supply to the white liquor (preferably adjusting the amount of oxygen supplied), adjusting the temperature of the white liquor, and adjusting the amount of oxidizing agent (preferably sulfide salt) added to the white liquor. In a more preferred embodiment, the control of the state of the white liquor is by adjusting the oxygen supply to the white liquor (preferably the amount of oxygen supplied), and more preferably by adjusting the oxygen supply (preferably the amount of oxygen supplied) and the temperature. Furthermore, the gas used for adjusting the oxygen supply is preferably oxygen or an oxygen-containing gas (preferably air), with air being more preferred, for example.

[0084] The state of the white liquor is preferably controlled using color tone data of the white liquor obtained by measuring its color tone (preferably color tone measurement data or color tone processing data). The control of the state of the white liquor is preferably performed using white liquor color data, and more preferably using white liquor color processing data that has been processed (converted or modified, etc.) based on the white liquor color measurement data.

[0085] The aforementioned color tone data of the white liquor (preferably color tone processing data) is preferably one or more selected from the relative R, G, B light reception of the white liquor and the estimated value of the polysulfide concentration in the white liquor. The relative R, G, B light reception of the white liquor is preferably data that has a statistical relationship (preferably a negative correlation) with the polysulfide concentration in the white liquor. These relationships are preferably linked to or embedded in the file information of one or both of these and stored in a memory unit, cloud, server, etc. The control unit may access the memory unit, etc. as needed and send and receive this file information or data related to the control of the state of the vaporized white liquor (for example, various data related to the color tone or processing (conversion, processing, etc.) of the color tone or color tone data and its acquisition information, various data related to processing and acquisition information in the estimation model or estimation formula for the polysulfide concentration in the white liquor, various data related to the polysulfide formation reaction, etc.) to each unit.

[0086] The control of the state of the white liquor is preferably performed such that the color data is the R-relative light reception amount of the white liquor or the G-relative light reception amount of the white liquor, and the state of the white liquor is preferably controlled such that (a) when the R-relative light reception amount or G-relative light reception amount is higher than the target R-relative light reception amount or G-relative light reception amount set value (i.e., when the polysulfide concentration is low), the polysulfide formation reaction of the white liquor is promoted, or (b) when the R-relative light reception amount or G-relative light reception amount is lower than the target R-relative light reception amount or G-relative light reception amount set value (i.e., when the polysulfide concentration is high), the polysulfide formation reaction of the white liquor is suppressed. The set value may be a set value preset by the control unit, or a set value set or entered by the operator.

[0087] In controlling the state of the white liquid, it is preferable to use a convertible model or formula to match either the color data or the target set value to one of the conditions (standard, unit). In controlling the state of the white liquor, if the set value is the polysulfide concentration in the white liquor and the data thereof is to be adapted to this, the R, G, B relative light reception amount or data thereof may be processed (converted or modified) to an estimated value of the polysulfide concentration in the white liquor using a polysulfide concentration estimation model or estimation formula. Also, in this embodiment, if the set value is the polysulfide concentration in the white liquor, the set value may be processed (converted or modified) to the R, G, B relative light reception amount using a polysulfide concentration estimation model or estimation formula.

[0088] In controlling the state of the white liquor, it is preferable to control the state of the white liquor based on the acquired color processing data of the white liquor (preferably at least one of the relative light reception amounts of R, G, and B) based on the color tone or color tone data of the white liquor. More preferably, the acquired color processing data (one of the relative light reception amounts of R, G, and B) is compared with a set value corresponding to the color processing data (preferably a set value for the relative light reception amount of the white liquor), and the state of the white liquor is controlled based on the result of this comparison. More preferably, the state of the white liquor is controlled so that the excess or deficiency of the polysulfide concentration in the white liquor is within a set range, and such control can be one or more selected from polysulfide formation reactions, polysulfide concentration, and oxidation reactions.

[0089] In controlling the state of the white liquor, it is preferable that the R-relative light-receiving amount of the white liquor, the G-relative light-receiving amount of the white liquor, or the B-relative light-receiving amount of the white liquor, which are the color tone or color tone data (preferably color tone processing data) of the white liquor, have a statistical relationship, preferably a correlation and a simple regression equation (more preferably a negative correlation) with the polysulfide concentration in the white liquor. In controlling the state of the white liquor, it is preferable to estimate the polysulfide concentration in the white liquor based on the color tone or color tone data (preferably color tone processing data) of the white liquor. In controlling the state of the white liquor, it is preferable to control the polysulfide formation reaction, polysulfide concentration, or oxidation reaction based on the estimated concentration of polysulfides in the white liquor obtained based on the color tone of the white liquor or color tone data (preferably color tone processing data).

[0090] In controlling the state of the white liquor, it is preferable to compare the color processing data obtained based on the color tone or color tone data (preferably color tone measurement data) with a target set value, and to control the state of the white liquor (preferably polysulfide formation reaction, polysulfide concentration, or oxidation reaction) based on this comparison result. In the polysulfide concentration estimation model, it is preferable that the color processing data and the polysulfide concentration data have a negative correlation.

[0091] In controlling the state of the white liquor, it is preferable that the color tone or color tone data (preferably color tone processing data) is the R relative light reception amount of the white liquor or the G relative light reception amount of the white liquor, and it is preferable to (a) control the state of the white liquor to increase or promote the oxidation reaction of the white liquor, the polysulfide formation reaction, or the polysulfide concentration of the white liquor when the R relative light reception amount or the G relative light reception amount is higher than the set value of the R relative light reception amount or the G relative light reception amount (i.e., when the polysulfide concentration is low), or (b) control the state of the white liquor to decrease or suppress the oxidation reaction of the white liquor when the R relative light reception amount or the G relative light reception amount is lower than the set value of the R relative light reception amount or the G relative light reception amount (i.e., when the polysulfide concentration is high), or (c) control the state of the white liquor to maintain the oxidation reaction of the white liquor when the R relative light reception amount or the G relative light reception amount is within the range of the set value of the R relative light reception amount or the G relative light reception amount.

[0092] In controlling the state of the white liquor, it is preferable to control the state of the white liquor by comparing the estimated concentration of polysulfides in the white liquor obtained based on the color tone or color tone data (preferably color tone processing data) with the polysulfide concentration in the white liquor set or stored as a suitable range, and by (a) if the estimated concentration of polysulfides is less than the suitable range (less than the lower limit) of the polysulfides, increasing or promoting oxidation reactions, polysulfide formation reactions, or polysulfide concentration in the white liquor (for example, increasing the air ratio), or (b) if the estimated concentration of polysulfides exceeds the suitable range (exceeding the upper limit) of the polysulfides, decreasing or suppressing oxidation reactions in the white liquor (for example, decreasing the air ratio), or (c) if the estimated concentration of polysulfides falls within the suitable range (above the lower limit and below the upper limit) of the polysulfide concentration, maintaining oxidation reactions in the white liquor (for example, maintaining the air ratio).

[0093] 1-2-5. Example of this embodiment The control of the state of the white liquor in this embodiment will be described with reference to the first to seventh embodiments shown in Figures 1 to 8, but this embodiment is not limited to these. The first to third embodiments have some differences in the configuration of the apparatus, and the methods of this embodiment can be appropriately adopted, for example, the control methods of the fourth to seventh embodiments can be appropriately adopted. Furthermore, the fourth to seventh embodiments differ in some aspects of the control process, and the apparatus or system of these embodiments can be appropriately adopted. For example, the apparatus or system of the first to third embodiments can also be appropriately adopted. Furthermore, the configurations and control methods of the first to third embodiments and the fourth to seventh embodiments can be appropriately adopted and these first to seventh embodiments can be arbitrarily combined.

[0094] The apparatus or system for white liquor treatment described below according to this embodiment may also be an apparatus or system for white liquor monitoring, and the apparatus or apparatus for white liquor treatment or white liquor monitoring may also be a system.

[0095] This embodiment can provide a white liquor processing apparatus or white liquor monitoring system that monitors the color tone of the white liquor in pulp production and controls the state of the white liquor based on color tone data obtained by measuring the color tone of the white liquor. Furthermore, this embodiment can provide a white liquor processing apparatus or white liquor monitoring system that includes a control unit that monitors the color tone of the white liquor in pulp production and controls the state of the white liquor based on color tone data obtained by measuring the color tone of the white liquor. The white liquor in pulp production is preferably the white liquor used in the pulp digestion process. The control unit may also be accessible to various parts or devices. This provides a technology that allows for the most accurate understanding of the state of the white liquor. Furthermore, it enables monitoring of the color tone of the white liquor in pulp production (preferably the white liquor used in the pulping process) and control of the state of the white liquor based on the color tone data obtained by measuring the color tone of the white liquor. In this embodiment, the color treatment data of the white liquor can be processed into polysulfide concentration data, and the judgment can be made based on the polysulfide concentration. Alternatively, the target setting value can be processed into R, G, B relative light reception data, and the judgment can be made based on the R, G, B relative light reception. Furthermore, the data processing (conversion, manipulation, etc.) can be changed to other items that have a high statistical relationship (e.g., correlation) with these characteristic items, rather than just "polysulfide concentration" and "R, G, B relative light reception."

[0096] In this embodiment, the control unit is preferably located in one or more types selected from personal computers (pads, notebooks, desktops, etc.), servers, clouds, etc. In this embodiment, the control unit is preferably configured to transmit and receive data wirelessly or via wired connection to one or more devices selected from a color tone measuring device, a polysulfide generating device, an oxygen supply device, a temperature control device, and an auxiliary agent adding device, and is preferably connected to at least a color tone measuring device, or to a color tone measuring device and an oxygen supply device, or to a color tone measuring device, an oxygen supply device, and a polysulfide generating device.

[0097] <Embodiment 1 to Embodiment 3> An example of an apparatus or system for white liquor treatment in this embodiment will be described below as the First to Third Embodiments, but this embodiment is not limited thereto. Furthermore, the configurations, apparatus, etc. of the First to Third Embodiments may be combined in any way. As shown in Figure 2A, the apparatus or system according to this first embodiment preferably includes a white liquor color measuring unit (color detection unit) installed near the inlet between the quenching / caustication system 40 and the inlet of the polysulfide generation process (reactor), and a control unit for controlling the state of the white liquor. In this first embodiment, a preferred configuration includes a white liquor color measuring unit (color detection unit) installed near the inlet between the scavenging / caustication system 40 and the inlet of the polysulfide production process (reactor), an oxygen supply unit that supplies oxygen to the polysulfide production process, and a control unit that controls the white liquor state, wherein the control unit is in a state that allows access to the other units.

[0098] As shown in Figure 2B, the apparatus or system according to this second embodiment preferably includes a white liquor color measuring unit (color detection unit) installed between the outlet of the polysulfide generation process (reactor) and the digestion system 10 (digestion vessel 11), from near the outlet to near the inlet of the digestion vessel 11, and a control unit for controlling the state of the white liquor. In this second embodiment, a preferred configuration includes a white liquor color measuring unit (color detection unit) installed near the outlet of the polysulfide production process (reactor) or near the inlet of the digestion system 10 (digestion vessel 11) between the outlet and the digestion system 10 (digestion vessel 11), an oxygen supply unit that supplies oxygen to the polysulfide production process, and a control unit that controls the state of the white liquor, wherein the control unit is in a state that allows access to the other units.

[0099] As shown in Figure 3, the apparatus or system according to this third embodiment preferably comprises a plurality of white liquor color monitoring units (color detection units) installed near the inlet and outlet of the polysulfide generation process (reactor), an oxygen supply unit and a temperature control unit related to the polysulfide generation process, and a control unit for controlling the white liquor state. In this third embodiment, a preferred configuration includes a plurality of white liquor color monitoring units (color detection units) installed near the inlet between the quenching / caustication system 40 and the inlet of the polysulfide production process (reactor), and installed near the outlet between the outlet of the polysulfide production process (reactor) and the digestion system 10 (digestion vessel 11), an oxygen supply unit for supplying oxygen to the polysulfide production process, a temperature control unit for adjusting the temperature of the polysulfide production process, and a control unit for controlling the white liquor state, wherein the control unit is in a state where it can access the other units.

[0100] <This first embodiment> This first embodiment will be described with reference to Figure 2A. The white liquor treatment apparatus 100-1 according to this first embodiment includes a polysulfide generator 101 configured to generate polysulfides in the white liquor, a color tone measuring device 102 configured to measure the color tone of the white liquor, an oxygen supply device 103 configured to adjust the oxygen supply to the polysulfide generator (increase, decrease, maintain, etc.), and a control unit 110 that controls these. Part or all of the white liquor containing sodium sulfide and sodium hydroxide flows from the quenching / caustication system 40 into the white liquor treatment apparatus 100-1 through the inlet. Although not shown, the white liquor from the quenching / caustication system 40 may be transferred to the pulping system 10 via a separate line that does not pass through the white liquor treatment apparatus.

[0101] In this first embodiment, the color measuring device 102 is positioned immediately after the inlet of the polysulfide generator 101 to monitor the lines of the quenching / caustication system 40 and the polysulfide generator 101.

[0102] The control unit 110 monitors the color tone of the white liquor before it flows into the polysulfide generator 101 using the color tone measuring device 102. The control unit 110 receives color tone measurement data of the white liquor from the color tone measuring device 102 and processes the color tone measurement data of the white liquor as described above to generate color tone processing data (relative R, G, B light reception amount of the white liquor).

[0103] The control unit 110 preferably accesses a unit that stores a polysulfide concentration estimation model (estimation formula) in the white liquor and a suitable or appropriate polysulfide concentration (set value of polysulfide concentration) in the polysulfide generation apparatus 101, which are stored in a memory unit or server, and acquires data for these estimation models and set values. In addition to the estimation model for the polysulfide concentration in the white liquor, it is preferable to use in combination an estimation model for the oxidation reaction of polysulfides in the polysulfide generation process (for example, an estimation model or estimation formula that has a correlation between polysulfide concentration and air supply amount) in order to estimate and supply the required amount of air based on the difference between the set value of polysulfide concentration and the estimated value of polysulfide concentration in the white liquor. The control unit 110 then applies the color processing data of the white liquor to a model for estimating the polysulfide concentration in the white liquor, and calculates and obtains an estimated value of the polysulfide concentration in the white liquor.

[0104] The control unit 110 compares the estimated polysulfide concentration in the white liquor with the set value for the polysulfide concentration in the white liquor and determines the conditions for the oxidation treatment of the incoming white liquor. Based on the result of this comparison, if the polysulfide concentration in the white liquor is lower than the set value, the control unit 110 commands the oxygen supply device 103 to promote the polysulfide formation reaction in the incoming white liquor to reach the set value (for example, by increasing the oxygen supply amount); if the polysulfide concentration in the white liquor is higher than the set value, the control unit 110 commands the oxygen supply device 103 to suppress the polysulfide formation reaction in the incoming white liquor to reach the set value (for example, by decreasing the oxygen supply amount); or if the value is within the set range, the control unit 110 commands the oxygen supply device 103 to maintain the polysulfide formation reaction in the incoming white liquor (for example, by maintaining the oxygen supply amount). The control unit 110 may also measure the reaction temperature with a thermometer or the like, compare the reaction temperature with the set temperature, and command the temperature control device to reach the set temperature, thereby controlling the temperature adjustment of the polysulfide formation reaction.

[0105] This allows the first embodiment to determine the sodium polysulfide concentration of the white liquor before inflow as close to real-time and as accurately as possible. Furthermore, in this first embodiment, the state of the white liquor can be controlled so that the polysulfide concentration in the incoming white liquor can be adjusted to a target set value. This makes it possible to provide the pulping system with white liquor having an appropriate polysulfide concentration. The control unit 110 may process the color processing data of the white liquor into polysulfide concentration and make a judgment based on the polysulfide concentration, or it may process the set value into R, G, B relative light reception and make a judgment based on the R, G, B relative light reception. When the comparison between the measured value and the set value is the R, G, B relative light reception, the relative light reception has a negative correlation with the polysulfide concentration. Therefore, if the R, G, B relative light reception is higher than the set value, the polysulfide formation reaction in the white liquor is promoted, or if it is lower than the set value, the polysulfide formation reaction in the white liquor is suppressed.

[0106] <This second embodiment> This second embodiment will be described with reference to Figure 2B. The white liquor processing apparatus 100-2 according to this second embodiment is the same as the white liquor processing apparatus 100-1 according to this first embodiment, except that the arrangement of the color tone measuring device 102 is different from that of the white liquor processing apparatus 100-1 according to this first embodiment. Therefore, redundant devices, mechanisms, and operations similar thereto will be omitted as appropriate. The color measuring device 102 of this second embodiment is positioned immediately after the outlet of the polysulfide generator 101 to monitor the white liquor in the line (preferably a flow path, piping, etc.) of the polysulfide generator 101 and the digestion system 10.

[0107] The control unit 110 monitors the white liquor after it has flowed out of the polysulfide generator 101 using the color tone measuring device 102. The control unit 110 receives color tone measurement data of the white liquor from the color tone measuring device 102 and processes the color tone measurement data of the white liquor as described above to generate color tone processing data (relative R, G, B light reception amount of the white liquor).

[0108] The control unit 110 compares the estimated polysulfide concentration in the white liquor with the set value of the polysulfide concentration in the white liquor to determine the state of the discharged white liquor (preferably the polysulfide concentration in the pulping solution). Based on the result of this comparison, if the polysulfide concentration in the white liquor is lower than the set value, the control unit 110 commands the oxygen supply device 103 to promote the polysulfide formation reaction in the white liquor during the polysulfide formation process to reach the set value (for example, by increasing the oxygen supply amount). If the polysulfide concentration in the white liquor is higher than the set value, the control unit 110 commands the oxygen supply device 103 to suppress the polysulfide formation reaction in the white liquor during the polysulfide formation process to reach the set value (for example, by decreasing the oxygen supply amount). If the polysulfide concentration in the white liquor is within the range of the set value, the control unit 110 commands the oxygen supply device 103 to maintain the polysulfide formation reaction in the white liquor during the polysulfide formation process (for example, by maintaining the oxygen supply amount).

[0109] As a result, this second embodiment allows for the determination of the sodium polysulfide concentration in the white liquor (digestion solution) after effluent as close to real-time and as accurately as possible. Furthermore, this enables feedback control of the state of the white liquor. In this second embodiment, the polysulfide concentration in the white liquor during the polysulfide formation process can be adjusted to a set value, thereby controlling the state of the white liquor. This second embodiment also allows for rapid and accurate feedback control of the polysulfide formation concentration in the white liquor (digestion solution) after effluent to the polysulfide formation process as close to real-time as possible. This enables the provision of a white liquor with an appropriate polysulfide concentration to the digestion system. Furthermore, using the relative R, G, B light reception as a reference, the comparison between the measured value and the set value is such that, in the case of the relative R, G, B light reception, this relative light reception has a negative correlation with the polysulfide concentration. Therefore, if this relative R, G, B light reception is higher than the set value, the polysulfide formation reaction in the white liquor is promoted, or if this relative R, G, B light reception is lower than the set value, the polysulfide formation reaction in the white liquor is suppressed.

[0110] <This third embodiment> This third embodiment will be described with reference to Figure 3. The white liquid processing apparatus 100-3 according to this third embodiment is the same in configuration and operation as the first and second embodiments, except that the color measuring device 102 is placed in both the arrangement of the color measuring device 102 in the first embodiment and the arrangement of the color measuring device 102 in the second embodiment, and a temperature control device 104 is placed to adjust the temperature of the polysulfide generating apparatus 101. Therefore, redundant devices, mechanisms, and similar operations are omitted as appropriate.

[0111] The control unit 110 monitors the color tone of the white liquid before it flows into the polysulfide generator 101 using the color tone measuring device 102 and the color tone of the white liquid after it flows out using the color tone measuring device 102 in combination. The control unit 110 receives color tone measurement data of the white liquid before and / or after flow out from the respective color tone measuring devices 102, 102, and processes the color tone measurement data of the white liquid before and / or after flow out as described above to generate color tone processing data of the white liquid before and / or after flow out (relative R, G, B light reception amount of the white liquid).

[0112] The control unit 110 compares the estimated polysulfide concentration in the white liquor before inflow with the set value for polysulfide concentration and determines the conditions for the oxidation treatment of the incoming white liquor. Based on the result of this comparison, the control unit 110 commands the oxygen supply device 103 to adjust the oxygen supply amount so that the polysulfide concentration reaches the set value.

[0113] The control unit 110 then compares the estimated polysulfide concentration of the white liquor after discharge with the set value for polysulfide concentration and determines the conditions for the oxidation treatment of the white liquor in the polysulfide generation process. Based on the result of this comparison, the control unit 110 commands the oxygen supply device 103 to adjust the oxygen supply amount so that the polysulfide concentration reaches the set value.

[0114] Furthermore, when the temperature of the polysulfide production process falls outside a predetermined range, the control unit 110 commands the temperature adjustment unit 104 to bring the reaction temperature back within the predetermined range. This suppresses the instability of the polysulfide concentration caused by excessive or insufficient temperature.

[0115] This third embodiment allows for the determination of the sodium polysulfide concentration in the white liquor before and / or after discharge as close to real-time and as accurately as possible. Furthermore, in this third embodiment, the polysulfide concentration in the white liquor during the polysulfide formation process can be adjusted to a set value based on the polysulfide concentration in the incoming and outgoing white liquor, thereby controlling the state of the white liquor. This third embodiment also makes it possible to provide rapid and accurate feedback control of the polysulfide formation concentration in the white liquor before and / or after discharge to the polysulfide formation process as close to real-time and as accurately as possible. As a result, the pulping system can be provided with white liquor having an appropriate polysulfide concentration. Furthermore, using the relative R, G, B light reception as a reference, the comparison between the measured value and the set value is such that, in the case of the relative R, G, B light reception, this relative light reception has a negative correlation with the polysulfide concentration. Therefore, if this relative R, G, B light reception is higher than the set value, the polysulfide formation reaction in the white liquor is promoted, or if this relative R, G, B light reception is lower than the set value, the polysulfide formation reaction in the white liquor is suppressed.

[0116] <Embodiment 4 to Embodiment 7> As an example of a control unit or control method for the state of the white liquor in this embodiment, the control or control method of the 4th to 7th embodiments will be described below, but this embodiment is not limited thereto. Furthermore, the configurations, steps, methods, etc. of the 4th to 7th embodiments may be arbitrarily combined. In addition, each step and each numerical value setting may be performed by the control unit, or the operator may input them as appropriate. In this embodiment, the control unit preferably measures the color tone of the white liquid to acquire color tone data of the white liquid, and converts or processes the acquired color tone data of the white liquid into color tone data related to the control of the state of the white liquid to acquire color tone processing data. On the other hand, the control unit of this embodiment preferably calculates in advance the statistical relationship (e.g., correlation) between the color processing data and the polysulfide concentration in the white liquor, and obtains a polysulfide concentration estimation model or estimation formula in the white liquor. The control of this embodiment may appropriately store the set value of the polysulfide concentration in the white liquor in the polysulfide generation process (a suitable numerical range, an upper limit of generation, etc.), the polysulfide concentration estimation model in the white liquor, and various related, embedded or linked data in a memory unit, server, etc.

[0117] The control unit of this embodiment compares the color processing data with the set value and controls the polysulfide formation reaction so that the polysulfide concentration reaches the target set value, thereby controlling the state of the white liquor. The color processing data may be the relative R, G, B light reception amount, or it may be an estimated value of the polysulfide concentration in the white liquor. The control unit of this embodiment commands the polysulfide generation process or a related process to promote the polysulfide generation reaction if the color processing data is lower than a set value for the polysulfide concentration, to suppress the polysulfide generation reaction if the color processing data is higher than a set value for the polysulfide concentration, or to maintain the polysulfide generation reaction if the color processing data is within the range of the set value for the polysulfide concentration.

[0118] A preferred embodiment involves performing an air oxidation method. In this air oxidation method, it is desirable that the control of this embodiment instructs the oxygen supply device (e.g., a compressor) that supplies air to the polysulfide generation device to increase the oxygen supply amount when promoting the polysulfide generation reaction, to decrease the oxygen supply amount when suppressing the polysulfide generation reaction, or to maintain the oxygen supply amount when maintaining the polysulfide generation reaction.

[0119] As a result, the control unit of this embodiment can grasp the sodium polysulfide concentration of the white liquor before inflow and / or after outflow as close to real-time and as accurately as possible. Furthermore, the control unit of this embodiment can adjust the measured polysulfide concentration in the white liquor to a target set value, thereby controlling the state of the white liquor. This makes it possible to provide the pulping system with white liquor having an appropriate polysulfide concentration. In this embodiment, the control unit processes the measured color processing data of the white liquor into polysulfide concentration and makes a judgment based on the polysulfide concentration. However, the target setting value may be processed into the relative R, G, B light reception amount, and the judgment may be made based on the relative R, G, B light reception amount.

[0120] <This fourth embodiment> In this fourth embodiment, in step 101, the control unit starts controlling the state of the white liquor. The white liquor is preferably the white liquor used in the pulping process of pulp production. In step 102, the control unit has the color tone of the white liquor measured by a color tone measuring device and acquires the color tone data of the white liquor. It is preferable to convert or process the color tone data of the white liquor into color tone processing data of the white liquor (relative R, G, B light reception amount, estimated polysulfide concentration in the white liquor) based on the color tone measurement data of the white liquor. It is also preferable for the control unit to receive a polysulfide concentration estimation model (estimation formula) in the white liquor, which has been prepared in advance using the relative R, G, B light reception amount and the polysulfide concentration in the white liquor as feature quantities and based on their relationship, from a storage unit or the like and acquire the set value.

[0121] In step 103, the control unit controls the polysulfide formation reaction in the polysulfide formation step based on the color data (color processing data) of the white liquor. In a preferred embodiment, the control unit compares the color data of the white liquor with a set value and controls the PS formation reaction based on this comparison result. For example, it is preferable for the control unit to compare the color data of the white liquor (preferably color processing data converted to polysulfide concentration) with a set value of polysulfide concentration and instruct the unit to promote the reaction if the polysulfide concentration is lower than the set value, to suppress the reaction if the polysulfide concentration is higher than the set value, or to maintain the reaction if the polysulfide concentration is within the range of the set value. Furthermore, in the case of the relative R, G, B light intensity, the control unit is preferable to instruct the system to promote the polysulfide formation reaction in the white liquor if the comparison between the measured value and the set value of the white liquor's color tone data is higher than the set value, or to suppress the polysulfide formation reaction in the white liquor if the comparison is lower than the set value, since the relative light intensity is negatively correlated with the polysulfide concentration.

[0122] In step 104, the control unit determines whether to continue the production of the white liquor. If it chooses to continue, it returns to step 102; otherwise, it terminates the reaction in step 105.

[0123] <This fifth embodiment> In this fifth embodiment, in step 201, the control unit starts controlling the state of the white liquor. The white liquor is preferably the white liquor used in the pulping process of pulp production. In step 202, the control unit has a color measuring device measure the color tone of the white liquid and acquires the color tone data of the white liquid. In step 203, the control unit acquires color processing data (relative R, G, B light reception amount, estimated PS concentration) based on the color data of the white liquor. It is preferable to process (convert, modify) the color data of the white liquor into color processing data of the white liquor (relative R, G, B light reception amount, estimated polysulfide concentration in the white liquor) based on the color measurement data of the white liquor. It is preferable for the control unit to receive a polysulfide concentration estimation model (estimation formula) in the white liquor, which has been prepared in advance using the relative R, G, B light reception amount and the polysulfide concentration in the white liquor as features and based on their relationship, from a storage unit or the like, and to acquire set values.

[0124] In step 204, the control unit compares the color data of the white liquor with a set value and controls the PS generation reaction based on this comparison result. This comparison step can be compared to step 103 in this fourth embodiment.

[0125] In step 205, it is preferable for the control unit to instruct the system to promote the PS formation reaction if the color data of the white liquor is lower than the set value for polysulfide concentration, to suppress the reaction if it is higher than the set value for polysulfide concentration, or to maintain the reaction if it is within the range of the set value for polysulfide concentration. Furthermore, if the comparison between the measured value and the set value for the color data of the white liquor is the relative R, G, B light reception, then it is preferable for the control unit to instruct the system to promote the polysulfide formation reaction in the white liquor if the relative light reception is higher than the set value for R, G, B light reception, or to suppress the polysulfide formation reaction in the white liquor if it is lower than the set value for R, G, B light reception, since this relative light reception has a negative correlation with the polysulfide concentration.

[0126] In this case, a preferred mode of the PS generation reaction is the air oxidation method, in which the control unit commands the air ratio to increase if the PS generation reaction is to be promoted, to decrease the air ratio if the PS generation reaction is to be suppressed, or to maintain the air ratio if the PS generation reaction is to be maintained.

[0127] In step 206, the control unit determines whether to continue the production of the white liquor. If it chooses to continue, it returns to step 202; otherwise, it terminates the reaction in step 207.

[0128] <This sixth embodiment> In this sixth embodiment, in step 301, the control unit starts controlling the state of the white liquor. The white liquor is preferably the white liquor used in the pulping process of pulp production. In step 302, the control unit has a color measuring device measure the color tone of the white liquid and acquires the color tone data of the white liquid.

[0129] In step 303, the control unit acquires color processing data (relative R, G, B light reception amount, estimated PS concentration) based on the color data of the white liquor. It is preferable to process (convert, modify) the color data of the white liquor into color processing data of the white liquor (relative R, G, B light reception amount, estimated polysulfide concentration in the white liquor) based on the color measurement data of the white liquor. It is preferable for the control unit to receive a polysulfide concentration estimation model (estimation formula) in the white liquor, which has been prepared in advance using the relative R, G, B light reception amount and the polysulfide concentration in the white liquor as features and based on their relationship, from a storage unit or the like, and to acquire set values.

[0130] In step 304, the control unit compares the color data of the white liquor (estimated polysulfide concentration) with the set value A of the polysulfide concentration and determines whether the color data of the white liquor is lower than the set value A of the polysulfide concentration. If it is lower than the set value A of the polysulfide concentration (Yes), the unit proceeds to step 305; on the other hand, if it is higher (No), the unit proceeds to step 308.

[0131] In step 305, if the polysulfide concentration is lower than the set value A (Yes), the control unit promotes the PS generation reaction and proceeds to step 306.

[0132] In step 308, the control unit compares the color data of the white liquor (estimated polysulfide concentration) with the set value B of the polysulfide concentration and determines whether the color data of the white liquor is higher than the set value B of the polysulfide concentration. If it is higher than the set value B of the polysulfide concentration (Yes), the process proceeds to step 308; on the other hand, if it is lower (No), the process proceeds to step 306. In this lower case (No), there is no acceleration or inhibition of the PS generation reaction, and the PS generation reaction remains in the same state as before.

[0133] In step 309, if the polysulfide concentration is higher than the set value B (Yes), the control unit suppresses the PS generation reaction and proceeds to step 306.

[0134] In step 306, the control unit determines whether to continue the PS generation reaction. If it decides to continue (Yes), it returns to step 302 to acquire color tone data. If it decides not to continue (No), it terminates in step 307.

[0135] In steps 303 to 309, the control unit is instructed to promote the polysulfide formation reaction in the white liquor if the comparison between the measured value and the set value of the white liquor color data is higher than the set value (step 304a), or to suppress the polysulfide formation reaction in the white liquor if it is lower than the set value (step 308a), because the relative light reception amount of R, G, and B is negatively correlated with the polysulfide concentration.

[0136] <This seventh embodiment> In this seventh embodiment, in step 401, the control unit starts controlling the state of the white liquor. In step 402, the control unit has a color measuring device measure the color tone of the white liquid and acquires the color tone data of the white liquid. In step 403, the control unit processes (converts, processes) the white liquor color measurement data into R relative light reception data, which is the color processing data, and obtains it. It is preferable for the control unit to receive a pre-defined polysulfide concentration estimation model (estimation formula) for the white liquor, which is created based on the relationship between the R relative light reception amount and the polysulfide concentration in the white liquor, from a storage unit or the like, and obtain the set value.

[0137] In step 404, the control unit compares the measured R-relative light reception amount of the white liquid with the set value A (R-relative light reception amount > 300) and determines whether the color tone data of the white liquid (R-relative light reception amount) is higher than the set value A for the R-relative light reception amount. If it is higher than the set value A for the R-relative light reception amount (Yes), the unit proceeds to step 405; on the other hand, if it is lower (No), the unit proceeds to step 408.

[0138] In step 405, if the relative light intensity R is higher than the set value A (in other words, if the polysulfide concentration is low) (Yes), the control unit increases the air ratio to promote the PS generation reaction and proceeds to step 406.

[0139] In step 408, the control unit compares the measured color data of the white liquor with the set value B (relative R light reception < 100) to determine whether the color data of the white liquor (relative R light reception) is lower than the set value B for relative R light reception. If it is lower than the set value B for relative R light reception (Yes), the process proceeds to step 408; on the other hand, if it is higher (No), the process proceeds to step 406. In this case where it is higher (No), there is no promotion or suppression of the PS generation reaction (increase in air ratio and raw materials), so the PS generation reaction (air ratio) remains the same as before.

[0140] In step 409, if the color data of the white liquor (relative R light reception) is lower than the set value B for the relative R light reception (in other words, if the polysulfide concentration is high) (Yes), the control unit suppresses the PS generation reaction (reduction of air ratio) and proceeds to step 406. In step 406, the control unit determines whether to continue the PS generation reaction. If it decides to continue (Yes), it returns to step 402 to acquire color tone data. If it decides not to continue (No), it terminates in step 407.

[0141] Although this seventh embodiment has been described using the relative R light intensity, the steps may be performed similarly by substituting the relative R light intensity with the relative G light intensity or the relative B light intensity. In this case, the values ​​of the relative R light intensity in steps 404 and 408 can be converted to the corresponding polysulfide concentration using a polysulfide concentration estimation model (estimation formula), and then converted to the relative G light intensity or relative B light intensity corresponding to the converted polysulfide concentration.

[0142] 2. Apparatus and systems for white liquor treatment

[0143] In describing the example of the apparatus and system for white liquor treatment in this embodiment, explanations of each configuration and each treatment method, such as white liquor, monitoring of the color tone of the white liquor, color tone data processing, color tone data, color tone processing data, polysulfide concentration estimation model (estimation formula), polysulfide generation process, and control of the state of the white liquor, will be omitted as appropriate, as they overlap with the above-mentioned content (e.g., "1.") and the content described later (e.g., "3.", "4."), etc. However, the explanations in "1." to "4.", etc." also apply to this embodiment and can be adopted as appropriate.

[0144] The apparatus or system for white liquor treatment according to this embodiment is preferably configured to monitor the color tone of the white liquor in pulp production and to control the state of the white liquor based on that color tone. The white liquor in pulp production is preferably the white liquor used in the pulping process of pulp production. The system or apparatus is preferably configured to implement the method of this embodiment described in "1. White Liquor Treatment Method According to This Embodiment" above or the methods of this embodiment described in "3." and "4." below.

[0145] In a more preferred embodiment of this design, the apparatus or system for white liquor treatment monitors the color tone of the white liquor in pulp production and controls the state of the white liquor based on color tone data (preferably color tone treatment data) obtained by measuring the color tone of the white liquor. The apparatus or system for the white liquor treatment preferably includes a control unit configured to monitor the color tone of the white liquor in pulp manufacturing and to control the state of the white liquor based on color tone data (preferably color tone treatment data) obtained by measuring the color tone of the white liquor. In this case, the control unit can access various parts (color tone measurement unit, polysulfide generation unit, memory unit, etc.) located other than the apparatus or system for the white liquor treatment and acquire various data.

[0146] The apparatus or system for the white liquor treatment is preferably selected from a white liquor oxidation monitoring system, a white liquor treatment apparatus, a white liquor state control apparatus, a white liquor oxidation monitoring apparatus, or a white liquor oxidation control apparatus. The aforementioned system or apparatus is preferably used to implement the method of this embodiment described above or later. The apparatus or system for white liquor treatment preferably has a color tone or color tone data (preferably color tone processing data) that is selected from the group consisting of the R relative light reception amount of the white liquor, the G relative light reception amount of the white liquor, and the B relative light reception amount of the white liquor, which is one or more types.

[0147] Furthermore, a preferred embodiment is a polysulfide production process comprising a control device configured to monitor the color tone of the white liquor in pulp production and to control the state of the white liquor based on its color tone. An example of a polysulfide production process in this preferred embodiment is an apparatus or system for white liquor treatment that processes white liquor from a scavenging / caustic system into white liquor for use in a pulping system. The white liquor in pulp production is preferably the white liquor used in the pulping process. Moreover, it is even more preferable to provide a white liquor color measuring device for measuring or monitoring the color tone of the white liquor in pulp production (preferably the white liquor before and / or after the polysulfide production process). In addition, in the apparatus or system, the white liquor color measuring device may be connected to the control device for access.

[0148] The apparatus or system is more preferably further comprising a white liquor color measuring device for measuring the color of the white liquor in pulp production, and / or a reaction device configured to generate polysulfides in the white liquor. In addition, in the apparatus or system, the white liquor color measuring device and / or the polysulfide generation reaction device may be connected to a control device for access. The white liquor in pulp production is preferably the white liquor used in the pulping process of pulp production.

[0149] The apparatus or system is more preferably further equipped with one or more selected from the following to regulate the formation of polysulfides in the white liquor during the polysulfide formation process: an oxygen supply device that supplies oxygen or air to the white liquor; an additive addition device that adds an auxiliary agent (sodium sulfate) to the white liquor to regulate the formation of polysulfides in the white liquor; and a temperature control device that adjusts the temperature of the white liquor to regulate the formation of polysulfides in the white liquor. Furthermore, one or more selected from these devices may be connected to the control device so as to be accessible.

[0150] The oxygen supply device is preferably configured to adjust the amount of air (oxygen) supplied by a compressor or the like, and to mix the air with the white liquor within the reaction apparatus.

[0151] The temperature control device preferably comprises a temperature measuring device and a heating device. The temperature control device preferably includes a heating and / or cooling device, a temperature sensor, a temperature control mechanism, etc. The temperature control device may be configured to enable feedback temperature control. The operation control for the temperature control may use known operation controls, for example, ON / OFF operation control, P operation (proportional operation) control, and PID operation control are preferred.

[0152] The temperature measuring device may include, but is not limited to, temperature sensors, temperature controllers, and other measuring instruments. The temperature measuring device preferably includes at least a temperature sensor. The temperature sensor may be either contact-type or non-contact-type. Examples of contact-type temperature sensors include thermistors, thermocouples, and resistance thermometers, while examples of non-contact-type temperature sensors include radiation temperature sensors and color temperature sensors. One or more of these can be selected. Furthermore, the temperature sensor can be installed in the same location as the color monitoring location and / or in a location where the reaction temperature of the polysulfide production process can be measured. Examples of the heating and / or cooling mechanisms include heat exchange systems using fluids (liquids or gases), heaters, and cooling mechanisms (refrigerant piping, cooling water piping, etc.).

[0153] In the apparatus or system, the white liquor whose color is monitored in the white liquor color measuring device is preferably the white liquor flowing through the line (preferably a channel, pipe, etc.) through which the white liquor of the saturation / caustication system flows into the reaction apparatus, and / or the white liquor flowing through the line (preferably a channel, pipe, etc.) through which it flows out of the reaction apparatus to the pulping system.

[0154] The apparatus or system preferably (a) estimates the polysulfide concentration in the incoming white liquor based on color data (preferably color processing data) obtained by monitoring the color tone of the incoming white liquor, and controls the state of the white liquor so that the excess or deficiency of the polysulfide concentration in the white liquor falls within a predetermined range by comparing the estimated polysulfide concentration with a set value for the polysulfide concentration, and / or (b) estimates the polysulfide concentration in the outgoing white liquor based on color data (preferably color processing data) obtained by monitoring the color tone of the outgoing white liquor, and controls the state of the white liquor so that the excess or deficiency of the polysulfide concentration in the white liquor falls within a predetermined range by comparing the estimated polysulfide concentration with a set value for the polysulfide concentration.

[0155] The apparatus or system preferably (a) obtains at least one of the R relative light reception amount of the white liquid, the G relative light reception amount of the white liquid, or the B relative light reception amount of the white liquid based on color tone data (preferably color tone processing data) obtained by monitoring the color tone of the incoming white liquid, and controls the state of the white liquid by comparing the obtained relative light reception amount of the white liquid with a set value for the relative light reception amount of the white liquid so that the excess or deficiency of the polysulfide concentration in the white liquid is within a predetermined range, and / or (b) obtains at least one of the R relative light reception amount of the white liquid, the G relative light reception amount of the white liquid, or the B relative light reception amount of the white liquid based on color tone data (preferably color tone processing data) obtained by monitoring the color tone of the outgoing white liquid, and controls the state of the white liquid by comparing the obtained relative light reception amount of the white liquid with a set value for the relative light reception amount of the white liquid so that the excess or deficiency of the polysulfide concentration in the white liquid is within a predetermined range.

[0156] The white liquor treatment management or white liquor oxidation monitoring system according to this embodiment preferably includes a white liquor treatment management device or white liquor oxidation monitoring device equipped with at least the control unit described above. The white liquor treatment management or white liquor oxidation monitoring system of this embodiment may further include a communication unit that can transmit and receive wirelessly and / or via wired connections between the control unit or the white liquor treatment management device equipped with the control unit and other units or other devices.

[0157] Furthermore, the method according to this embodiment can also be implemented by a device or control unit including a CPU in an apparatus (e.g., a computer, PLC, server, cloud service, etc.) for managing the white liquor processing status, the state of the white liquor, etc. Alternatively, the method according to this embodiment can be stored as a program in hardware resources equipped with a recording medium (non-volatile memory (USB memory, etc.), HDD, CD, DVD, Blu-ray, etc.) and implemented by a control unit. The control unit can also provide an apparatus equipped with the control unit or system, such as a management system for monitoring the white liquor processing status or white liquor oxidation, which controls the polysulfide formation reaction (air oxidation method) in the white liquor. The management apparatus may also include an input unit such as a keyboard, a communication unit such as a network, a display unit such as a display, etc.

[0158] A device or management system for managing the white liquor processing status or monitoring white liquor oxidation may include an input unit such as a keyboard, a communication unit such as a network, an output unit such as a display, a storage unit such as an HDD, and the aforementioned color tone measurement unit. The device or system preferably includes an input unit, an output unit, and a storage unit, and more preferably includes a communication unit and / or a measurement unit. The input unit can receive user input from an operator performing the method of this embodiment. This input unit may include, for example, a mouse and / or a keyboard. Alternatively, the display surface of the display device may be configured as an input unit that accepts touch input. The output unit can output information related to the white liquor processing status or white liquor oxidation monitoring (e.g., tables, figures, explanatory text, etc.). The output unit may be, but is not limited to, a display device for displaying images, a speaker for outputting sound, or a printing device for printing on paper or other printing media. The storage unit can store data entered by the operator, data set to monitor the white liquor processing status, or data for monitoring white liquor oxidation. The storage unit may include, for example, a recording medium. Furthermore, the system relating to white liquor processing management, etc., according to this embodiment can be executed by utilizing a program and hardware. One embodiment of computer 1 according to one embodiment of the present invention (not shown) is not limited to this, but the computer 1 may include at least a CPU as a component, and may further include one or two selected from RAM, storage unit, output unit, input unit, communication unit, ROM, and measurement unit, of which it is preferable to include RAM, storage unit, output unit, and input unit, and further, it is preferable to include at least one communication unit, measurement unit, ROM, etc. The respective components are preferably connected by a bus, for example, as a data transmission path.

[0159] In this embodiment, a simplified example of the processing procedure for the specialized AI used as a trained model can be described as "(1) training data → (2) algorithm → (3) trained model" or "(4) input data → (3) trained model → (5) result", but is not limited to this (see, for example, Figure 10). In a broad framework, specialized AI is a mechanism in which a result is obtained by applying arbitrary input data to a trained model, which is constructed by incorporating training data (teaching data) into an algorithm that functions as a learning program.

[0160] In this embodiment, the white liquor in the training data (teaching data) can include white liquor from the field and simulated white liquor from experiments. The control unit acquires multiple sets of data, each containing at least two values: a measured color tone of the white liquor and the polysulfide concentration in the white liquor, as training data (teaching data). It is preferable to use at least these two values ​​as one data set. The control unit also prefers to process (convert, modify) the measured color tone of the white liquor into R, G, B relative light reception data and use this processed data. The control unit can read two or more selected teaching data sets from a storage unit, server, cloud, etc. The storage unit may pre-store measured color tone of the white liquor and polysulfide concentration values ​​in the white liquor obtained from multiple field sites or experiments. Furthermore, multiple samples with polysulfide concentration gradients (or different concentrations), multiple samples prepared by the external standard addition method, etc., may be used as the white liquor for training data.

[0161] Next, the control unit can construct a predictive or estimation model (trained model) for the polysulfide concentration in the white liquor by incorporating the training data read from the memory unit into a pre-set algorithm. As a result, the control unit is configured to have a predictive or estimation model for the polysulfide concentration in the white liquor. As described above, the trained model (such as a predictive model for the polysulfide concentration in the white liquor) can be obtained using "statistical analysis".

[0162] The algorithm described above can function as a machine learning algorithm, for example. The type of machine learning algorithm is not particularly limited; it may be an algorithm using a neural network such as RNN (Recurrent Neural Network), CNN (Convolutional Neural Network), or MLP (Multilayer Perceptron), or any other algorithm.

[0163] Next, the control unit inputs the input data (4) input data (input layer) from the operator to a constructed prediction model of the polysulfide concentration in the white liquor (trained model), thereby generating data (5) results (output layer) related to the polysulfide generation process of the white liquor (white liquor color processing data, estimated polysulfide concentration in the white liquor, etc.) for output from the display. The pre-trained model may be, for example, a pre-trained model generated by deep learning. For example, the pre-trained model may be a multilayer neural network, for example, a deep neural network (DNN), and more specifically, a convolutional neural network (CNN). A multilayer neural network may be used as the pre-trained model, and the multilayer neural network may have an input layer into which the subject or the like inputs age values ​​and measurement values, an output layer that outputs the wrinkle evaluation results of the subject, and at least one intermediate layer provided between the input layer and the output layer.

[0164] The control unit can implement methods such as generating a trained model, estimating the polysulfide concentration in the white liquor at a target site using the trained model, or controlling the state of the white liquor or processing the white liquor using the estimation method. A method for generating a trained model, comprising: (a) acquiring multiple training data sets that include at least two values ​​as data: a color tone measurement of the white liquor (preferably, the relative R, G, B light reception amount) and the polysulfide concentration value in the white liquor; (b) inputting at least two values, the color tone measurement of the white liquor and the polysulfide concentration value in the white liquor, using the training data; and (c) generating a trained model that outputs a white liquor state estimation model (preferably a model for estimating the polysulfide concentration in the white liquor) for estimating the white liquor state (preferably the polysulfide concentration in the white liquor) from these input data.

[0165] (d) Acquiring data of at least two values: a measured color of the white liquor and a polysulfide concentration in the white liquor; (e) Applying at least two values: a measured color of the white liquor and a measured polysulfide concentration in the white liquor to a trained model generated by the trained model generation method using at least two values: a measured color of the white liquor and a measured polysulfide concentration in the white liquor, thereby generating a polysulfide concentration value in the white liquor estimated in relation to the measured color of the white liquor (preferably, relative R, G, B light intensity); and (f) Providing a method such as a white liquor processing method, a polysulfide concentration estimation method, or a method for adjusting the polysulfide concentration in the white liquor, using the generated estimated value. A program that causes a computer to execute a method such as the white liquor treatment method described above, or a recording medium that stores said program. An apparatus or system related to white liquor treatment, a white liquor treatment apparatus or a white liquor oxidation monitoring system, etc., including said program or said recording medium.

[0166] 3. Overview of the pulp manufacturing system using the white liquor treatment method in this embodiment

[0167] In describing the example of the pulp manufacturing system in this embodiment, explanations of each component and each processing method, such as white liquor, monitoring of the color tone of the white liquor, color tone data processing, color tone data, color tone processing data, polysulfide concentration estimation model (estimation formula), polysulfide generation process, and control of the state of the white liquor, will be omitted as appropriate, as they overlap with the above-mentioned contents (e.g., "1.", "2.", etc.) and contents described later (e.g., "4.", etc.). However, the explanations in "1." to "4.", etc. also apply to this embodiment and can be adopted as appropriate.

[0168] The outline of a pulp manufacturing system using the white liquor treatment method according to the present invention will be described below, but the pulp manufacturing system described herein is just one example, and this embodiment is not particularly limited to this pulp manufacturing system.

[0169] Figure 1 is a schematic diagram of a pulp manufacturing system 1 using the white liquor treatment method according to the present invention, and the present invention is not limited thereto. In this embodiment, the pulp manufacturing system may be a general pulp manufacturing system into which the white liquor treatment or white liquor treatment management apparatus or system of this embodiment is incorporated.

[0170] The pulp production system 1 according to this embodiment may include a digestion system 10, a black liquor treatment system 20, a green liquor treatment system 30, and a scavenging / causticization system 40. These systems may be connected to each other by pipes shown by solid lines in Figure 1, and may together constitute a circulation path (see, for example, Patent Document 4: Japanese Patent Application Publication No. 2018-083176). The following provides a more detailed explanation of each system.

[0171] <3-1. Digestion System> The digestion system 10 has a digester 11 having heaters (not shown) at the top and / or bottom, and a pulp refining section may be provided downstream of the digester 11. Wood chips, which are the raw material for pulp, and a white liquor containing caustic soda (preferably a polysulfide digestant) are fed into the digester 11, and the wood chips are digested. The resulting pulp is transferred to a pulp sorting system, where it undergoes sorting and washing processes, followed by bleaching and papermaking processes to produce paper. Meanwhile, the waste liquid, black liquor, is transferred to an evaporator 21, described later, for purposes such as the recovery of caustic soda.

[0172] <3-2. Black Liquor Treatment System> The black liquor treatment system 20 may include, in order from upstream, an evaporator 21 and a boiler 22. After the black liquor is concentrated in the evaporator 21 (black liquor concentration step), it is transferred to the boiler 22 and burned in the boiler 22 (black liquor combustion step). As a result, the inorganic sodium salts contained in the black liquor melt and are discharged as smelt from the bottom of the boiler 22. The discharged smelt is transferred to a dissolving tank 31.

[0173] The boiler 22 may be equipped with a heat recovery system for recovering thermal energy. Conventional heat recovery systems can be used for this purpose.

[0174] <3-3. Green sap treatment system> The green liquor production system 30 comprises, in order from upstream, a dissolution tank 31, a green liquor clarifier 32, and a green liquor tank 33. The green liquor is agitated and dissolved in water in the dissolution tank 31. This produces a green liquor rich in sodium carbonate in addition to sodium hydroxide. The dissolution tank 31 is equipped with a liquid transfer pump (not shown), and the green liquor is drawn into this pump and transferred to the green liquor clarifier 32. Any remaining undissolved components of the green liquor are removed in the green liquor clarifier 32. After that, it is transferred to the green liquor tank 33 for storage and eventually transferred to the causticization system 41.

[0175] <3-4. Elimination and Caustic System> The quenching and causticization system 40 may include a causticization system 41, a white liquor clarifier 42, and a white liquor tank 43. The quenching and causticization system 40 may further include a lime mud washer 46, a lime mud filter 45, and a kiln 44 located downstream of the white liquor clarifier 42. The causticization system 41, the white liquor clarifier 42, and the white liquor tank 43 are connected to each other and together constitute a circulation path.

[0176] The clarified green liquor, transferred to the caustication system 41, is mixed with calcium oxide supplied from the kiln 44. This mixing process will be described in more detail.

[0177] The caustication system 41 may have a slaker 411 and a plurality of caustication reaction tanks 412 located downstream of the slaker 411. The clarified green liquor (usually 90-100°C, pH 13-14) transferred to the slaker 411 is mixed with calcium oxide, which is also supplied to the slaker 411. This causes the calcium oxide to be quenched with water to produce calcium hydroxide (quenching reaction step). Subsequently, when transferred to the caustication reaction tanks 412, the sodium carbonate in the green liquor reacts with the calcium hydroxide to produce caustic soda and calcium carbonate (caustication reaction step).

[0178] The white liquor obtained in this way is transferred to the white liquor clarifier 42. In the white liquor clarifier 42, insoluble calcium carbonate settles and is separated, and the white liquor is then stored in the white liquor tank 43 and eventually circulated back to the digester 11 for reuse. Meanwhile, the separated calcium carbonate is recovered in the kiln 44, where it is roasted and returned to calcium oxide (lime calcination process), and reused in the causticization system 41.

[0179] More specifically, in the causticization system 41, calcium oxide (CaO) obtained in the kiln 44 is added to the clarified green liquor in the slaker 411 to undergo a sequestering reaction: CaO + water → Ca(OH)2 + water. This reaction then reacts with Na2CO3 in the clarified green liquor of the slaker 411 to form Ca(OH)2 + Na2CO3 + water → CaCO3(↓) + 2NaOH + water. The aqueous solution containing NaOH from which CaCO3 has been recovered is then used as a white liquor. In this way, caustic soda and calcium carbonate are repeatedly reused as recycled resources in the recovery cycle during the causticization process.

[0180] 4. About this technology This technology can employ the following configuration. · [1] A method for treating white liquor, which involves monitoring the color of the white liquor used in the pulping process of pulp manufacturing and controlling the state of the white liquor based on that color. This white liquor treatment method may also be a method for controlling or managing the white liquor treatment. • [2] The white liquor treatment method according to [1] above, wherein the color tone is obtained by measuring the color tone of the white liquor used in the pulping process of the pulp manufacturing (preferably color tone measurement data, color tone processing data, etc.), and the state of the white liquor is controlled from the color tone data. • [3] A white liquor treatment method comprising: a white liquor state control step, which monitors the color tone of the white liquor used in the pulping process of pulp manufacturing and controls the state of the white liquor based on the color tone or the color tone data (preferably color tone processing data). Furthermore, it is preferable to include a white liquor color tone measurement step for measuring the color tone of the white liquor in pulp manufacturing. • [4] The white liquor treatment method according to any one of [1] to [3] above, wherein the white liquor treatment involves treating the white liquor from a quenching / caustication system containing sulfide salts and hydroxide salts in a polysulfide formation step (preferably an oxidation reaction step) in the white liquor to a white liquor containing polysulfides to be used in the pulping step.

[0181] • [5] The white liquor treatment method described in any one of the above [1] to [4], wherein the white liquor treatment method is (a) a method for stabilizing, improving, or suppressing the decrease in kraft pulp yield or a method for stabilizing, improving, or suppressing the decrease in pulp yield in the pulping process, (b) a method for generating, preparing, or adjusting the concentration of polysulfides in the white liquor, (c) a method for producing or preparing white liquor for use in the pulping process, or a method for controlling white liquor oxidation treatment, or (d) a method for estimating the polysulfide concentration in the white liquor, or (e) a monitoring system for these methods or a white liquor oxidation monitoring system.

[0182] • [6] The control of the state of the white liquor is a white liquor treatment method according to any one of [1] to [5] above, which controls the state of the white liquor (polysulfide pulping agent) in the polysulfide production process. • [7] The method for treating white liquor according to any one of [1] to [6] above, wherein the control of the state of the white liquor is to control the polysulfide formation reaction or the polysulfide formation process, or to control the polysulfide concentration in the white liquor, the polysulfide formation reaction in the white liquor, or the oxidation treatment or oxidation reaction of the white liquor. The oxidation treatment or oxidation method is preferably an air oxidation method (preferably an air oxidation method by the MOXY method), and the air oxidation catalyst is activated carbon particles (preferably hydrophilically treated activated carbon particles). • [8] The control of the state of the white liquor is performed by one or more selected from the group consisting of adjusting the amount of an oxidizing agent (preferably a sulfide salt) added to the white liquor, adjusting the temperature of the white liquor, and adjusting the amount of oxygen supplied to the white liquor, as described in any one of [1] to [7] above. Of these, adjusting the temperature of the white liquor and adjusting the amount of oxygen supplied to the white liquor are preferred. • [9] The control of the state of the white liquor is performed by adjusting the oxygen supply (preferably the amount of oxygen supplied) to the white liquor, and more preferably by adjusting the oxygen supply and the temperature, as described in any one of [1] to [8] above. The gas used for adjusting the oxygen supply is preferably oxygen or an oxygen-containing gas, and for example, air is more preferable.

[0183] ·

[10] The white liquid treatment method according to any one of [1] to [9] above, wherein the color tone or color tone data of the white liquid is color tone processing data processed (converted or modified, etc.) based on the color tone or color tone data (preferably color tone measurement data), and preferred color tone processing data is the relative R, G, B light reception amount of the white liquid and an estimated value of the polysulfide concentration in the white liquid. ·

[11] The white liquid treatment method according to any one of [1] to

[10] , wherein the color tone or color tone data (preferably color tone processing data) of the white liquid is one or more selected from the group consisting of the R relative light reception amount of the white liquid, the G relative light reception amount of the white liquid, and the B relative light reception amount of the white liquid. Preferably, the R relative light reception amount of the white liquid or the G relative light reception amount of the white liquid. ·

[12] A white liquor treatment method according to any one of [1] to

[11] above, wherein the polysulfide formation reaction, polysulfide concentration, or oxidation reaction is controlled based on at least one of the R relative light reception amount of the white liquor, the G relative light reception amount of the white liquor, or the B relative light reception amount of the white liquor obtained based on the color tone or color tone data (preferably color tone measurement data) of the white liquor. ·

[13] A white liquor treatment method according to any one of [1] to

[12] above, comprising: obtaining at least one of the R relative light reception amount of the white liquor, the G relative light reception amount of the white liquor, or the B relative light reception amount of the white liquor based on the color tone or color tone data (preferably color tone measurement data) of the white liquor; and controlling the state of the white liquor by comparing the obtained relative light reception amount of the white liquor with a set value for the relative light reception amount of the white liquor, so that the excess or deficiency of the polysulfide concentration in the white liquor is within a predetermined range. ·

[14] The method for treating a white liquor according to any one of [1] to

[13] , wherein the R relative light reception amount of the white liquor, the G relative light reception amount of the white liquor, or the B relative light reception amount of the white liquor, which are the color tone or color tone data (preferably color tone processing data) of the white liquor, have a correlation (preferably a simple regression equation) with the polysulfide concentration in the white liquor. •

[15] A method for treating a white liquor according to any one of [1] to

[14] above, wherein the concentration of polysulfides in the white liquor is estimated based on the color tone or color tone data (preferably color tone processing data) of the white liquor. ·

[16] A method for treating white liquor according to any one of [1] to

[15] , wherein a polysulfide formation reaction, polysulfide concentration, or oxidation reaction is controlled based on the estimated concentration of polysulfides in the white liquor obtained based on the color tone of the white liquor or color tone data (preferably color tone processing data). •

[17] The white liquor treatment method according to any one of [1] to

[16] , wherein the color tone or color tone data (preferably color tone processing data) of the white liquor is the color tone or color tone data (preferably color tone processing data) of the white liquor flowing into the polysulfide production process, and / or the color tone or color tone data (preferably color tone processing data) of the white liquor flowing out from the polysulfide production process. •

[18] A white liquor treatment method according to any one of [1] to

[17] above, comprising comparing color processing data obtained based on the aforementioned color tone or color tone data (preferably color tone measurement data) with a set value, and controlling a polysulfide formation reaction, polysulfide concentration, or oxidation reaction based on the comparison result. ·

[19] If the aforementioned color tone or color tone data (preferably color tone processing data) is the R-relative light reception amount of the white liquor or the G-relative light reception amount of the white liquor, and the R-relative light reception amount or the G-relative light reception amount is higher than a set value, the state of the white liquor is controlled to increase or accelerate the oxidation reaction of the white liquor, the polysulfide formation reaction, or the polysulfide concentration of the white liquor, or If the R relative light reception amount or the G relative light reception amount is lower than the set value, the state of the white liquor is controlled to reduce or suppress oxidation reactions, etc. The white liquor treatment method described in any one of the above [1] to

[18] . ·

[20] A white liquor treatment method according to any one of [1] to

[19] above, comprising: comparing the estimated concentration of polysulfides in the white liquor obtained based on the aforementioned color tone or color tone data (preferably color tone processing data) with the polysulfide concentrations in the white liquor that have been set or stored in advance as a suitable range; and controlling the state of the white liquor so as to (a) increase or promote oxidation reactions, polysulfide formation reactions, or polysulfide concentrations in the white liquor (for example, by increasing the air ratio) if the estimated concentration of polysulfides is less than the range of suitable polysulfide concentrations (less than the lower limit); (b) decrease or suppress oxidation reactions in the white liquor (for example, by decreasing the air ratio) if the estimated concentration of polysulfides is less than the range of suitable polysulfide concentrations (less than the lower limit); or (c) maintain oxidation reactions in the white liquor (for example, by maintaining the air ratio) if the estimated concentration of polysulfides is within the range of suitable polysulfide concentrations (above the lower limit and below the upper limit). Furthermore, using the relative R, G, B light reception as a reference, it is preferable to control the state of the white liquor in such a way that, when comparing the measured value with the set value, the relative R, G, B light reception is (a) increased or promoted if it exceeds the set value, the polysulfide formation reaction in the white liquor is increased, (b) decreased or suppressed if it falls below the set value, or (c) maintained if it falls within the specified range.

[0184] ·〔twenty one〕 An apparatus or system for white liquor treatment that monitors the color tone of the white liquor used in the digestion process of pulp manufacturing and controls the state of the white liquor based on color tone data (preferably color tone treatment data) obtained by measuring the color tone of the white liquor. The system or apparatus preferably implements the method described in any one of [1] to

[20] above. ·〔twenty two〕 The apparatus or system for the white liquor treatment described in

[21] is selected from a white liquor oxidation monitoring system, a white liquor treatment apparatus, a white liquor state control apparatus, a white liquor oxidation monitoring apparatus, or a white liquor oxidation control apparatus. ·〔twenty three〕 An apparatus or system for white liquor treatment, comprising a control unit configured to monitor the color tone of the white liquor used in the digestion process of pulp production and to control the state of the white liquor based on color tone data (preferably color tone treatment data) obtained by measuring the color tone of the white liquor, or the apparatus or system according to

[21] or

[22] above. ·〔twenty four〕 An apparatus or system for white liquor treatment that carries out the method described in any one of the above [1] to

[20] . ·〔twenty five〕 The apparatus or system for white liquor processing according to any one of

[21] to

[24] , wherein the color tone or color tone data (preferably color tone processing data) is one or more selected from the group consisting of the R relative light reception amount of the white liquor, the G relative light reception amount of the white liquor, and the B relative light reception amount of the white liquor.

[0185] •

[26] The control device is configured to monitor the color of the white liquor used in the pulping process of pulp production and to control the state of the white liquor based on its color. An apparatus or system for white liquor treatment in a polysulfide production process, which processes white liquor from a quenching / caustication system to produce white liquor for use in a pulping system, or an apparatus or system for white liquor treatment according to any one of

[21] to

[25] above. Furthermore, it is preferable to provide a white liquor color measuring device for measuring or monitoring the color of the white liquor used in the pulping process of pulp production (preferably the white liquor before and / or after the polysulfide formation process). •

[27] Furthermore, an apparatus or system for white liquor treatment according to any one of

[21] to

[26] above, which further accesses and controls a white liquor color measuring device for measuring the color of the white liquor used in the pulping process of pulp production, and / or a reaction device configured to generate polysulfides in the white liquor. The apparatus or system may access various devices as appropriate and acquire various data. •

[28] Furthermore, the apparatus or system for white liquor treatment according to any one of

[21] to

[27] further comprises a white liquor color measuring device for measuring the color of the white liquor used in the pulping process of pulp production, and / or a reaction device configured to generate polysulfides in the white liquor. ·

[29] Furthermore, the apparatus or system for white liquor treatment according to any one of

[21] to

[28] further includes, and / or, accessing and controlling one or more selected from the following in order to adjust the formation of polysulfides in the white liquor during the polysulfide formation process: an oxygen supply device that supplies oxygen or air to the white liquor; an additive addition device that adds an auxiliary agent (sodium sulfate) to the white liquor to adjust the formation of polysulfides in the white liquor; and / or a temperature control device that adjusts the temperature of the white liquor to adjust the formation of polysulfides in the white liquor. The apparatus or system may access the various devices as appropriate and acquire various data. •

[30] In the aforementioned white liquid color measuring device, the white liquid whose color is monitored is: An apparatus or system for white liquor treatment according to any one of

[21] to

[29] , wherein the white liquor of the smoking / caustication system flows through a line (preferably a channel, pipe, etc.) into the reaction apparatus, and / or the white liquor flows through a line (preferably a channel, pipe, etc.) out of the reaction apparatus to the pulping system. ·

[31] Based on the color data (preferably color processing data) obtained by monitoring the color tone of the incoming white liquor, the polysulfide concentration in the incoming white liquor is estimated, and the estimated polysulfide concentration is compared with a set value for the polysulfide concentration to control the state of the white liquor so that the excess or deficiency of the polysulfide concentration in the white liquor falls within a predetermined range, and / or An apparatus or system for treating white liquor according to any one of

[21] to

[30] above, comprising: monitoring the color tone of the discharged white liquor and estimating the polysulfide concentration in the discharged white liquor based on color tone data (preferably color tone processing data) obtained; comparing the estimated polysulfide concentration with a set value for polysulfide concentration and controlling the state of the white liquor so that the excess or deficiency of the polysulfide concentration in the white liquor falls within a predetermined range. ·

[32] Based on the color tone data (preferably color processing data) obtained by monitoring the color tone of the incoming white liquid, at least one of the R relative light reception amount of the white liquid, the G relative light reception amount of the white liquid, or the B relative light reception amount of the white liquid is acquired, and the acquired relative light reception amount of the white liquid is compared with a set value for the relative light reception amount of the white liquid to control the state of the white liquid so that the excess or deficiency of the polysulfide concentration in the white liquid is within a predetermined range, and / or An apparatus or system for white liquor treatment according to any one of

[21] to

[31] , wherein, based on color data (preferably color processing data) obtained by monitoring the color tone of the discharged white liquor, at least one of the R relative light reception amount of the white liquor, the G relative light reception amount of the white liquor, or the B relative light reception amount of the white liquor is obtained, and the state of the white liquor is controlled so that the excess or deficiency of the polysulfide concentration in the white liquor is within a predetermined range by comparing the obtained relative light reception amount of the white liquor with a set value for the relative light reception amount of the white liquor. [Examples]

[0186] Embodiments of the present invention will be described with reference to the following examples and comparative examples. However, the scope of the present invention is not limited to these examples.

[0187] [Test Example 1] As described below, a white liquor treatment apparatus equipped with a color detection device can be used to continuously measure the color of the white liquor in the reaction apparatus (oxidation apparatus) for polysulfide production. Based on the results of this white liquor color measurement, the amount of oxygen supplied to the reaction apparatus (oxidation apparatus) and the temperature can be adjusted.

[0188] <Configuration of the white liquid processing device (white liquid color detection device)> The white liquor processing system used in this test includes an RGB color sensor, a multi-sensor controller, a programmable controller, and a network communication unit, along with a basic color sensor device (white liquor color tone measuring device). Furthermore, the white liquor processing system used in this test includes a thermocouple thermometer (commercially available) that can measure the temperature of the white liquor with a temperature sensor, and an oxygen supply unit configured to adjust the amount of air (oxygen) supplied by a compressor and mix the air with the white liquor, although these can also be considered auxiliary parts.

[0189] The white liquor treatment apparatus has the following configuration. (1) RGB color sensor LR-W500 manufactured by Keyence Corporation (2) Controller: MU-N12, manufactured by Keyence Corporation (3) PLC (Keyence Corporation KV-NC32T) (4) Communication unit: NU-EP1 manufactured by Keyence Corporation (5) Thermocouple thermometer (6) Oxygen supply unit (air compressor)

[0190] For the RGB color sensor, we used the LR-W500 (manufactured by Keyence Corporation), which is a white spot photoelectric sensor with a built-in amplifier. As a multi-sensor controller, we used the MU-N12 multi-sensor controller (manufactured by Keyence Corporation). A 16-input / 16-output KV-NC32T2 (manufactured by Keyence Corporation) was used as the programmable logic controller (PLC). As a network communication unit, the communication unit EtherNet / IP TM The compatible NU-EP1 (manufactured by Keyence Corporation) was used.

[0191] <White Spot Photoelectric Sensor LR-W500> Detection distance: 30-500 mm (from the light source to the liquid surface of the sample) Minimum spot size: Variable spot approx. φ3.5 at 100mm / approx. φ9 at 250mm / approx. φ18mm at 500mm Response time: Switchable between 200μs / 1ms / 10ms / 100ms / 500ms Light source White LED Ambient illuminance for use: Incandescent lamp: 10,000 lux or less; Sunlight: 20,000 lux or less; Operating ambient temperature: -20 to +50°C (do not freeze) Operating ambient humidity: 35-85% RH (non-condensing)

[0192] <Measurement principle> The principle of measuring white liquor (or white liquor oxide) is as follows: a white LED light emitted from a color sensor strikes the object to be measured (liquid surface), the light receiving part of the color sensor detects the color reflected by the object, and the data is calculated and output as RGB color components. This RGB value data is transmitted externally from a communication unit. This RGB value data is sent to a computer including the white liquor processing control unit, and the RGB values ​​at this time are displayed on the computer screen. The white liquor processing control unit then calculates the sodium polysulfide concentration (estimated value) in the white liquor from the calculated output to an arbitrary color coordinate and the change in the measured value. The white liquor processing control unit can also measure the temperature of the white liquor during oxidation processing or oxidation reaction using a thermocouple thermometer in the oxidation device and receive the result. The white liquor processing control unit can control each part and other devices of the white liquor processing device, and can issue commands to each part and other devices to control the state of the white liquor (oxidation reaction of the white liquor).

[0193] <Test Example 1> A simulated white liquor was prepared using NaOH, Na2CO3, and Na2S before the reaction. The same sample was titrated twice, and the results are shown in Table 1. The aqueous quality of the simulated white liquor before polysulfide formation (oxidation reaction) is also shown in Table 1. The total titration alkali was measured according to SCAN-N 30:85 (Non-Patent Document 3). Furthermore, "g / L asNa2O" indicates that the total sodium salt is generally expressed as Na2O.

[0194] [Table 1]

[0195] To 100 mL of this simulated white liquor (adjusted liquor: No. 1-5), 0 to 2 g (0, 0.5, 1.0, 1.5, 2.0 g) of MnO₂ was added, and it was stirred while heating to 60 °C for oxidation. The simulated white liquor after the oxidation reaction was filtered with 5A filter paper, and for the filtrate, polysulfide analysis (Patent Document 1: JP-A-07-92148: Analysis method of polysulfur composing sodium polysulfide) and color tone analysis (Patent Document 3: JP-A-2022-12850 (Japanese Patent Application No. 2020-114974)) were carried out according to the methods. The results of polysulfide formation obtained by the oxidation reaction are shown in Table 2 as PS (g / L as S). Note that as the oxidizing agent, a MnO₂ reagent (manufactured by Kishida Chemical Co., Ltd., primary manganese(IV) oxide, powder, purity (90.0% or more)) was used.

[0196] <Measurement conditions for color tone analysis> Measurement container: 100 mL glass beaker Measurement distance: Distance between the liquid surface and the color sensor is 16 cm Measurement temperature: 60 °C

[0197] <Polysulfide analysis> <Preparation of sodium polysulfide digestion chemical solution / analysis sample for the previous stage> Into three 100 mL volumetric flasks purged with nitrogen, 95 mL of deoxygenated water was put, and 1 mL each of the above-mentioned "simulated white liquor after oxidation reaction (sample)" was added separately, and deoxygenated water was added thereto to make a constant volume of 100 mL. The prepared sodium polysulfide digestion chemical solution is used as the analysis sample for the previous stage. [[ID=第十九]] [[ID=二十]]

[0198] [[ID=二十一]] [[ID=二十二]]<Preparation of sodium polysulfide digestion chemical solution / analysis sample for the latter stage>[[ID=二十三]] [[ID=二十四]]By the same operation, 0.115 grams of sodium sulfite was added and dissolved in each volumetric flask prepared to a constant volume of 100 mL by adding 1 mL each of the above-mentioned "simulated white liquor after oxidation reaction (sample)" separately, heated under an inert gas atmosphere, heated to 70 °C, and held at that temperature for 1 hour. The sodium polysulfide digestion chemical solution after the reaction was completed by maintaining the temperature is used as the analysis sample for the latter stage. [[ID=二十五]] [[ID=二十六]]

[0199] [[ID=二十七]] [[ID=二十八]]<Analysis operation>[[ID=二十九]] Inject 10 μL each of the previously mentioned sodium polysulfide pulping chemical solution, the analysis samples of each previous stage, and the analysis samples of the subsequent stage into a high-performance liquid chromatograph analyzer. In the analysis operation, when using the same ion chromatograph device for the previous and subsequent processes, inject the analysis sample of the previous stage, and after creating a chromatogram chart, inject 10 μL of a dilute solution of sodium sulfite (1 gram per liter) into the column for cleaning. The analysis conditions are as follows.

[0200] <Analysis Conditions> (1) The high-performance liquid chromatograph analyzer is the 800 series manufactured by JASCO (2) The separation column is TSK-gel / IC-Anion-PW (trade name of Tosoh), with a diameter of 4.6 mm, a length of 50 mm, and two columns in series (3) The temperature of the separation column is 45 °C (4) The detector is a UV detector (5) The detection wavelength is 225 nm (6) The mobile phase is an aqueous solution of dipotassium hydrogen phosphate at 4 mmol (7) The flow rate is 1.2 mL / min (8) The sample injection volume is 10 μL

[0201] <Creation of Chromatogram Chart> Calculate the amount of sodium thiosulfate in the analysis samples of each previous and subsequent stage from the peak areas of the obtained chromatogram charts, and from these values, according to the formula shown in [Chemical Formula 01], determine the amount of polysulfur in the sodium polysulfide that composes the "simulated white liquor (sample) after the oxidation reaction". Note that [Chemical Formula 01] uses the weight converted to sulfur as the unit.

[0202] <Calculation of Polysulfur> (1) When calculating by analyzing thiosulfate ions, prepare a column for analyzing thiosulfate ions contained in the sodium polysulfide pulping chemical solution and a column for analyzing thiosulfate ions increased by reacting sulfite ions with this sodium polysulfide pulping chemical solution, and based on the difference in thiosulfate ions quantified by these columns, the amount of polysulfur can be determined according to the formula of [Chemical Formula 01].

[0203] [Chemical Formula 01] Sulfur polysulfide = (S2O3 after reaction with sulfite ions) 2- - S2O3 before sulfite ion action 2- )÷2

[0204] The results of the white liquor oxidation test for preparation solutions No. 1 to 5 (Test Examples 1-1 to 1-5) of Test Example 1 are shown in Table 2, Figure 8A (relationship between relative light reception and polysulfides), Figure 8B (relationship between relative light reception R, G, B and polysulfides), and Figures 9A, B, C (correlation between relative light reception R, G, B and polysulfides, and correlation coefficients).

[0205] [Table 2]

[0206] The inventors prepared simulated white liquor by gradually changing the polysulfide concentration and analyzed the color tone of this simulated white liquor using a non-contact optical sensor in accordance with the color tone analysis described in Patent Document 3: Japanese Patent Application Publication No. 2022-12850 (Japanese Patent Application No. 2020-114974). However, with this color tone analysis method, the R value is capped at 255, making it difficult to adequately grasp the state of polysulfide (PS) formation. After further intensive research, the inventors focused on the fact that the amount of light received by the optical sensor decreases in accordance with the formation of polysulfide (PS), as the amount of transmitted light from the white liquor decreases.

[0207] Furthermore, the inventors have newly discovered that, in observing the color tone of the white liquid, they can combine the concept of the amount of light received with the concept of the color tone of the white liquid to derive the relative amount of light received, and by monitoring this relative amount of white light received, they can estimate the concentration of polysulfides in the white liquid.

[0208] More specifically, we found that by using the following formulas, we can monitor the state of the white liquor containing polysulfides: R relative light reception = total light reception × R / (R+G+B), G relative light reception = total light reception × G / (R+G+B), and B relative light reception = total light reception × B / (R+G+B). Furthermore, the inventors discovered a correlation between the relative R, G, and B light levels and the polysulfide concentration. They also found that the polysulfide concentration in the white liquor (dependent variable (y)) can be estimated by regression analysis using the relative R light levels, relative G light levels, and relative B light levels as explanatory variables (x). Of these, the high correlation coefficients suggest that estimating and controlling the polysulfide concentration in the white liquor based on the relative R light levels and / or relative G light levels is preferable, and estimating and controlling the polysulfide concentration based on the relative R light level is more preferable.

[0209] In actual field operations, the range of polysulfide concentrations required or preferred in the white liquor for the pulping process varies depending on the conditions of the white liquor at the site (actual equipment, season, raw materials, etc.). However, the present invention has the advantage of being able to obtain an estimation model (simple regression equation) of polysulfide concentration from the measurement results of color tone measurements and polysulfide concentration measurements at the site, according to the conditions of white liquor treatment at the site. In this case, an estimation model (estimation equation) of polysulfide concentration in the white liquor calculated using two features, color tone data and polysulfide concentration data, is preferred.

[0210] Furthermore, with this invention, a target polysulfide concentration range can be set according to the conditions of the white liquor treatment at the site. By comparing this set value with the estimated polysulfide concentration in the white liquor calculated by applying the measured color tone values ​​to the polysulfide concentration estimation model, the state of the white liquor (the state of the polysulfide concentration (g / L as S) in the white liquor) can be better understood and controlled. In addition, the set value of the polysulfide concentration can be converted to the same items and units as the measured color tone processing data (relative light reception amount, etc.) using the polysulfide concentration measurement model. With this invention, it is not necessary to process the color tone data (preferably color tone processing data) acquired over time to the estimated polysulfide concentration in the white liquor, thus reducing the amount of data, shortening processing time, and reducing power consumption.

[0211] As a specific example from those shown in Figures 8 and 9, we will explain the R-value of white liquor oxides and polysulfides. The PS concentration (g / L as S) is determined by utilizing the fact that as the PS concentration increases within the range of 0 to 5 (g / L as S), the R relative light reception decreases linearly. PS concentration (y) = -0.0266 × R (relative light received (x)) + 8.2251 (correlation coefficient R) 2 =0.9143; negative correlation) For example, if the relative R light intensity is 200, the PS concentration is estimated to be 2.9 (g / L as S).

[0212] The control unit can set a target value of 4-5 (g / L as S) for a suitable polysulfide concentration in the white liquor. The control unit then uses a polysulfide concentration estimation model to calculate that a suitable polysulfide concentration of 4-5 (g / L as S) in the white liquor corresponds to an R-relative light reception of 121-159, and determines this set value to be the target value. When the measured R-relative light reception is 200, the control unit, having exceeded the target value of 159, instructs the air supply device to increase the air-to-white liquor ratio to promote the oxidation reaction and thus reduce the R-relative light reception. Furthermore, an increase in the air-white liquor ratio promotes polysulfide formation (oxidation reaction), leading to a decrease in R-relative light reception. This decreasing trend in color processing data can be continuously measured and monitored using a color sensor device.

[0213] When the R relative light reception amount calculated based on the color tone measurement data from the color sensor device falls below 121 (estimated PS concentration of 5 g / L as S), the control unit instructs the air supply device to reduce the air-white liquid air ratio. Furthermore, when the R relative light reception amount calculated based on the color tone measurement data from the color sensor device is 121-159 (estimated PS concentration of 4-5 g / L as S), the control unit instructs the system to maintain the air-white liquor air ratio. Alternatively, instead of the control unit, the person in charge of the white liquor treatment (white liquor oxidation reaction) may manage the air ratio of the air supply device and control the white liquor reaction and the PS concentration in the white liquor.

[0214] Furthermore, in the general air oxidation PS method, the concentration of sodium polysulfide in white liquor (in terms of S conversion) is about 5 to 6 g / L as S. Therefore, in the case of the R relative light reception amount, when controlling the concentration of polysulfide in white liquor based on the R relative light reception amount (especially in the air oxidation PS method), it can be said that there is a balanced slope between the sodium polysulfide concentration of 0 to 6 g / L as S. The air oxidation method for obtaining PS is easier to maintain the balance of circulating Na and S compared with the method of adding sulfur from the outside to white liquor in the kraft pulp process.

[0215] Regarding using the G relative light reception amount and the B relative light reception amount as explanatory variables (x), similar to the R relative light reception amount, the concentration of polysulfide in white liquor (objective variable (y)) can be estimated. When the color tone measurement data is the G value, PS concentration (S conversion) = -0.0206 × G relative light reception amount (x) + 5.3226 (correlation coefficient R 2 = 0.8367). When grasping and controlling the concentration of polysulfide in white liquor based on the G relative light reception amount, it can be said that it can be preferably used between the polysulfide concentration of 0 to 3 g / L as S. When the color tone measurement data is the B value, PS concentration (S conversion) = -0.0242 × B relative light reception amount (x) + 4.0974 (correlation coefficient R 2 = 0.5859). When grasping and controlling the concentration of polysulfide in white liquor based on the B relative light reception amount, it is considered that it can be preferably used between the polysulfide concentration of 0 to 0.5 g / L as S.

[0216] In this specification, the upper limit (less than or equal to) and lower limit (greater than or equal to) of a numerical range (~) can be arbitrarily combined as desired. Also, in this specification, for example, "to monitor" may be a method, process, step or means, a "step" may be "to do", a method, process or means, a "process" or "method" may be "to do", a step or means, a "means" may be "to do", a method, process or step, and these may also be mechanisms, devices, means or parts. Furthermore, in this specification, "system" may refer to a mechanism, apparatus, means or part, or method; "mechanism" may refer to a system, apparatus, means or part, or method; "apparatus" may refer to a system, mechanism, means or part, or method; "means" may refer to a mechanism, system, apparatus, or part; and "part" may refer to a mechanism, means, apparatus, or system, method, or a mechanism, means, or apparatus for providing these. [Explanation of symbols]

[0217] 1 Pulp production system; 10 Digestion system; 11 Digestion kettle; 20 Black liquor treatment system; 21 Evaporator; 22 Boiler; 30 Green liquor treatment (crude green liquor treatment) system; 31 Dissolution tank (dispersion); 32 Green liquor clarifier (clarification); 33 Clarified green liquor tank; 36 Extraction pump; 37 Sludge concentration measuring unit; 34 Chemical tank; 35 Chemical injection pump; 40 Suppression / causticization system; 41 Causticization system; 42 White liquor clarifier; 43 White liquor tank; 44 Kiln; 411 Slaker; 412 Causticization reaction vessel; 45 Lime mud filter; 46 Lime mud washer; 100 White liquor treatment system (white liquor oxidation monitoring system); 101 Polysulfide production equipment (polysulfide production process); 102 Color tone measurement (color tone monitoring) device (color tone measurement process); 103 Oxygen supply device (oxygen supply process); 104 Temperature control device (temperature control process); 110 Control device (control process)

Claims

1. This is a white liquor treatment method that monitors the color of the white liquor used in the pulping process and controls the polysulfide concentration in the white liquor based on that color. The aforementioned color tone is the color tone data of the white liquid obtained by measuring the color tone of the white liquid. The white liquid treatment method wherein the color tone data of the white liquid is one or more selected from the group consisting of the R relative light reception amount of the white liquid and the G relative light reception amount of the white liquid.

2. The method for treating a white liquor according to claim 1, wherein the R-relative light-receiving amount of the white liquor, or the G-relative light-receiving amount of the white liquor, is correlated with the polysulfide concentration in the white liquor.

3. A white liquor treatment method comprising monitoring the color tone of the white liquor used in the pulping process of pulp production and controlling the polysulfide concentration in the white liquor based on the color tone, The aforementioned color tone is the color tone data of the white liquid obtained by measuring the color tone of the white liquid. The aforementioned color data is the R-relative light reception amount of the white liquid or the G-relative light reception amount of the white liquid. If the R-relative light-receiving amount or the G-relative light-receiving amount is higher than the set value for the R-relative light-receiving amount or the G-relative light-receiving amount, the polysulfide concentration in the white liquor is controlled to promote the polysulfide formation reaction in the white liquor, or If the R relative light reception amount or the G relative light reception amount is lower than the set value for the R relative light reception amount or the G relative light reception amount, the polysulfide concentration in the white liquor is controlled to suppress the polysulfide formation reaction in the white liquor. The aforementioned white liquor treatment method.

4. The method for treating white liquor according to claim 1 or 3, wherein the amount of oxygen supplied to the white liquor is adjusted to control the polysulfide concentration in the white liquor.

5. The color of the white liquor used in the pulp manufacturing digestion process is monitored, and the concentration of polysulfides in the white liquor is controlled based on the color data obtained by measuring the color of the white liquor. The aforementioned color data is the R-relative light reception amount of the white liquid or the G-relative light reception amount of the white liquid. White liquor oxidation monitoring system.

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