A saturation process using food grade carbon dioxide as a sugar refining agent

Abstract

The application discloses a saturation process using food-grade carbon dioxide as a sugar-making clarifying agent, which comprises the following steps: food-grade carbon dioxide storage; liquid carbon dioxide vaporization; gaseous carbon dioxide pressure regulation and metering; air pressure gas preparation and regulation; primary gas mixing; mixed gas storage and heating; secondary gas mixing; saturation reaction and automatic control. The application uses food-grade carbon dioxide as a clarifying agent, which has high purity and few impurities, avoids the secondary pollution of traditional flue gas impurities to sugar juice, improves the sugar juice clarification effect, is beneficial to guaranteeing the quality of white granulated sugar, realizes the accurate control of gas pressure through a two-stage pressure regulation system, guarantees the stability of gas delivery, realizes the automation of the saturation process through the linkage control of an on-line pH meter and the mixed gas input amount, makes the sugar juice pH value stable within the optimal range, improves the stability and efficiency of the saturation reaction, and reduces the manual operation intensity.

Description

Technical Field

[0001] This invention belongs to the field of sugar juice clarification technology in the sugar industry, specifically relating to a saturation process that uses food-grade carbon dioxide as a sugar clarifying agent, and is particularly suitable for sugar enterprises without lime kilns and boilers. Background Technology

[0002] In the sugar industry, the saturation process is the core step in clarifying sugar juice. It involves the reaction of carbon dioxide with lime milk in the sugar juice to form calcium carbonate precipitate, which adsorbs impurities in the juice, thus purifying it. In traditional saturation processes, carbon dioxide mainly comes from the flue gas produced by calcining lime in lime kilns or boiler flue gas. These gases are low-cost and readily available, but they suffer from low purity (e.g., containing sulfur, dust, and other impurities) and unstable composition, easily leading to secondary contamination of the sugar juice and affecting the quality of white sugar.

[0003] Food-grade carbon dioxide, with a purity of ≥99.9% and extremely low impurity content (such as sulfides and particulate matter), can theoretically significantly improve the clarification of sugar juice and reduce the load on subsequent filtration. However, it is stored in liquid form and requires high pressure to maintain its liquid state at room temperature. Its use involves complex processes such as vaporization, pressure regulation, and mixing. Furthermore, the sugar industry lacks mature application technology, resulting in its extremely limited use in sugar filling processes.

[0004] Sugar refining enterprises, geographically constrained by their inability to construct lime kilns and boilers, face a severe shortage of carbon dioxide, threatening their survival and the maintenance of the quality of their long-established white sugar brands. Therefore, developing a process that effectively utilizes food-grade carbon dioxide as a clarifying agent in sugar refining is of significant practical importance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a saturation process that uses food-grade carbon dioxide as a sugar-making clarifying agent. This solves the problem of the difficulty in applying food-grade liquid carbon dioxide in the sugar-making saturation process, achieves efficient sugar juice clarification under conditions without lime kilns and boilers, and further improves the quality of white sugar products. The white sugar produced by this process is superior to that produced under conditions of lime kilns and boilers.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a saturation process using food-grade carbon dioxide as a sugar clarifying agent, comprising the following steps:

[0008] S1. Storage of food-grade carbon dioxide

[0009] Food-grade liquid carbon dioxide is transported to a carbon dioxide storage tank for storage, with a working pressure of 2.0-2.5 MPa.

[0010] S2. Vaporization of liquid carbon dioxide

[0011] Liquid carbon dioxide is converted into gaseous carbon dioxide through two vaporizers connected in parallel. The vaporizers use natural heating to completely vaporize the liquid carbon dioxide.

[0012] S3. Pressure regulation and measurement of gaseous carbon dioxide

[0013] The vaporized gaseous carbon dioxide is sequentially controlled by two sets of parallel pressure regulating valves to adjust the pressure to 0.30MPa-0.35MPa, while the flow rate of gaseous carbon dioxide is controlled by a flow meter.

[0014] S4. Preparation and Regulation of Compressed Air

[0015] Compressed air at 0.7MPa pressure is sequentially passed through two sets of parallel pressure regulating valves to control the pressure and flow rate, adjusting the pressure to 0.15MPa-0.2MPa, while the flow rate of the compressed air is controlled by a flow meter.

[0016] S5. Primary gas mixing

[0017] The gaseous carbon dioxide adjusted in step S3 and the compressed air adjusted in step S4 are introduced into a static pipeline mixer and mixed at a volume ratio of 1:4-1:8.

[0018] S6. Storage and heating of mixed gases

[0019] The gas after primary mixing enters the gas storage tank for pressure stabilization, and then is heated to 70-80℃ to obtain the initial mixed gas;

[0020] S7. Gas secondary mixing

[0021] Use a screw blower to blow in 600-1200m 3 / h of air enters the primary mixed gas and then undergoes secondary mixing through a Venturi mixer to obtain a mixed gas that meets the process requirements;

[0022] S8. Saturation Reaction and Automatic Control

[0023] After secondary mixing, the gas passes through the main regulating valve and then enters the No. 1 saturation tank and the No. 2 saturation tank through the branch regulating valves respectively. Before the mixed gas enters the saturation tank, the pH value of the saturation tank is monitored by an online pH meter to establish a linkage between the online pH meter and the mixed gas flow rate, thereby realizing automatic control of the mixed gas flow rate.

[0024] Since the total volumetric flow rate of the carbon dioxide and compressed air mixture obtained in step S6 is 600-1200 m³ / s... 3After running for a period of time, it was found that the plate and frame filter press had great difficulty filtering saturated syrup. Multiple sedimentation experiments revealed that the calcium carbonate particles were small and settled quickly, indicating that the saturation effect was not yet optimal. To solve this problem, numerous experiments were conducted to verify various factors in the saturation process. The final conclusion was that insufficient total volume of saturated gas resulted in small porosity in the calcium carbonate, and the impurity adsorption capacity had not reached its optimal state. Therefore, an additional screw blower was added to pump in 600-1200 m³ of gas. 3 / h of air enters the primary mixture and then undergoes secondary mixing through a Venturi mixer to obtain a mixed gas that meets the process requirements.

[0025] Furthermore, in step S3, the flow rate of gaseous carbon dioxide is controlled at 100-250 m³ / h. 3 / h.

[0026] Furthermore, in step S4, the flow rate of the compressed air is controlled at 500-1000 m³ / h. 3 / h.

[0027] Furthermore, in step S7, the total gas volumetric flow rate after secondary mixing is controlled at 1200-2400 m³ / h. 3 / h.

[0028] Further, in step S8, the logic of the automatic control is as follows: the pH value of the saturated syrup is controlled between 9.0 and 9.5. When the online pH meter detects that the pH value of the saturated syrup is higher than 9.5, the mixed gas flow rate is automatically increased; when the online pH meter detects that the pH value of the saturated syrup is lower than 9.0, the mixed gas flow rate is automatically decreased. The pH value of the saturated syrup is controlled between 8.0 and 8.5. When the online pH meter detects that the pH value of the saturated syrup is higher than 8.5, the mixed gas flow rate is automatically increased; when the online pH meter detects that the pH value of the saturated syrup is lower than 8.0, the mixed gas flow rate is automatically decreased.

[0029] Furthermore, in step S8, each saturated tank is equipped with an independent branch regulating valve at the mixed gas inlet to achieve individual control of the flow rate of a single tank.

[0030] The optimized process of this invention achieves the following effects by increasing gas volume and mixing efficiency:

[0031] (1) This invention systematically solves the problem of applying food-grade liquid carbon dioxide in the sugar saturation process for the first time. Through process design such as vaporization, pressure regulation and multi-stage mixing, it realizes the stable application of food-grade carbon dioxide and provides a feasible solution for sugar enterprises without lime kilns and boilers.

[0032] (2) Food-grade carbon dioxide is used as a clarifying agent. It has high purity and few impurities, which avoids secondary pollution of sugar juice by impurities in traditional flue gas, improves the clarification effect of sugar juice, and helps to ensure the quality of white sugar. It is especially suitable for enterprises that need to maintain the quality of old brands.

[0033] (3) The two-stage pressure regulation system enables precise control of gas pressure and ensures the stability of gas delivery; the use of a static pipeline mixer and a Venturi mixer for two-stage mixing ensures the uniformity of gas mixing.

[0034] (4) A screw blower was installed to supplement air, which solved the problem of mismatch between the total amount of mixed gas and the process requirements, ensuring the full progress of the saturation reaction, ensuring that the calcium carbonate particles generated during the carbonation saturation process are large and have large pores, and that the large calcium carbonate particles fall slowly during the sedimentation experiment, resulting in clear juice and a saturation decolorization rate of 65%.

[0035] (5) By linking the online pH meter with the amount of mixed gas introduced, the saturation process was automatically regulated, so that the pH value of the sugar juice was kept within the optimal range, which improved the stability and efficiency of the saturation reaction and reduced the intensity of manual operation. Attached Figure Description

[0036] Figure 1 Specialized equipment for carrying out the process of the present invention is shown.

[0037] Among them: 100-Carbon dioxide tank truck, 101-Carbon dioxide storage tank, 101-1-Carbon dioxide storage tank pressure sensor, 102-Vaporizer, 103-Carbon dioxide pressure regulating valve, 104-Carbon dioxide online pressure and flow meter, 105-Compressed air storage tank, 106-Compressed air pressure regulating valve, 107-Compressed air online pressure and flow meter, 108-Static pipeline mixer, 109-Storage tank, 1091-Mixed gas pressure sensor, 110-Shell-tube heater, 110-1 Mixed gas temperature sensor, 111-Screw blower, 111-1-Blower outlet 111-Air temperature sensor, 111-2-Fan outlet pressure sensor, 112-Venturi mixer, 113-First mixed gas storage tank, 114-Second mixed gas storage tank, 115-C1 gas regulating valve, 115-1-Online mixed gas flow meter, 116-D2 gas regulating valve, 116-1-Online mixed gas flow meter, 117-No.1 saturation tank, 118-C1 online pH meter, 119-No.2 saturation tank D2, 120-D2 online pH meter, 121-Automatic control system for carbon dioxide and air mixing, 122-Automatic control system for saturation process. Detailed Implementation

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0039] Unless otherwise specified, the instruments or reagents used in the examples are all conventional instruments or reagents in the art and are commercially available products. Unless otherwise specified, the specific experimental operations involved in the text are all understandable or known to those skilled in the art based on their common knowledge or conventional technical means, and will not be described in detail here.

[0040] like Figure 1 As shown, a saturation process using food-grade carbon dioxide as a sugar clarifying agent includes the following steps:

[0041] (1) Storage of food-grade carbon dioxide:

[0042] Food-grade liquid carbon dioxide was transported to the factory in a 100-ton carbon dioxide tanker truck and delivered to a 50m³ location. 3 The carbon dioxide is stored in a carbon dioxide storage tank 101, and the working pressure of the carbon dioxide storage tank 101 is 2.0-2.5MPa (e.g. 2.0, 2.1, 2.2, 2.3, 2.4, 2.5MPa, with 2.2MPa being the most preferred). The storage tank 101 is equipped with a carbon dioxide storage tank pressure sensor 101-1.

[0043] (2) Vaporization of liquid carbon dioxide:

[0044] The liquid carbon dioxide in the carbon dioxide storage tank 101 is converted into gaseous carbon dioxide by two parallel vaporizers 102. The vaporizers 102 use natural heating to completely vaporize the liquid carbon dioxide.

[0045] (3) Pressure regulation and measurement of gaseous carbon dioxide:

[0046] The vaporized gaseous carbon dioxide passes sequentially through two sets of parallel carbon dioxide pressure regulating valves 103. The pressure is adjusted by the valves 103 to 0.30 MPa-0.35 MPa (e.g., 0.30, 0.31, 0.32, 0.33, 0.34, 0.35 MPa, with 0.32 MPa being the preferred setting). Simultaneously, the instantaneous pressure and flow rate of the gaseous carbon dioxide are displayed by an online pressure and flow meter 104. The carbon dioxide flow rate is controlled within 100 m³ / s according to the process specifications. 3 / h-250m 3 / h (e.g., 100, 150, 180, 200, 250m) 3 / h, optimal value 180m 3 / h).

[0047] (4) Preparation and regulation of compressed air:

[0048] Compressed air at 0.7 MPa is drawn from the compressed air storage tank 105 and sequentially regulated to 0.15 MPa-0.20 MPa (e.g., 0.15, 0.16, 0.17, 0.18, 0.19, 0.20 MPa, with 0.18 MPa being the most preferred) through two sets of parallel compressed air pressure regulating valves 106. Simultaneously, the compressed air flow rate is displayed as 500 m³ / s on the online compressed air pressure and flow meter 107. 3 / h-1000m 3 / h (e.g., 500, 600, 700, 800, 900, 1000m) 3 / h, optimal value 800m 3 / h).

[0049] (5) Primary gas mixing:

[0050] The gaseous carbon dioxide adjusted in step 3 and the compressed air adjusted in step 4 are introduced into the static pipeline mixer 108 and mixed at a volume ratio of 1:4-1:8 (e.g., 1:4, 1:5, 1:6, 1:7, 1:8, with 1:6 being the most preferred).

[0051] (6) Storage and heating of mixed gases:

[0052] The gas after primary mixing enters 3.5m 3 The gas is stabilized in the gas storage tank 109 and then heated to 70°C-80°C (e.g., 70°C, 75°C, 80°C, with 75°C being the most preferred) by the tube heater 110 (equipped with a mixed gas temperature sensor 110-1).

[0053] (7) Secondary mixing of gases:

[0054] The total volume of the carbon dioxide and compressed air mixture obtained in step (6) is 600 m³. 3 / h-1200m 3 / h (e.g., 600, 700, 800, 900, 1000, 1100, 1200m) 3 / h, optimal value 900m 3 / h), after operation, it was found that the filter mud had high light conversion and was difficult to filter, resulting in limited production capacity. 3 units of 120m 2 The plate and frame filter press only has a sugar dissolving capacity of 430 tons / day. After multiple sedimentation experiments, it was found that the calcium carbonate particles produced by saturation were small and settled quickly, leading to filtration difficulties. Therefore, after repeated experiments, it was determined that the saturation gas volume needed to be increased to meet production requirements. A screw blower 111 (equipped with blower outlet air temperature sensor 111-1 and blower outlet pressure sensor 111-2) was added to blow in 600m³ of gas. 3 / h-1200m 3 / h (e.g., 600, 700, 800, 900, 1000, 1100, 1200m) 3 / h, optimal value 900m 3 Air (at a rate of 1 / h) enters the primary mixture, and then undergoes a secondary thorough mixing via Venturi mixer 112, resulting in a total volume of 1200 m³. 3 / h-2400m 3 / h (e.g., 1200, 1400, 1600, 1800, 2000, 2200, 2400m) 3 / h, optimal value 1800m 3 The mixed gas ( / h) meets the process requirements. The secondary mixed gas enters the first mixed gas storage tank 113 and then the second mixed gas storage tank 114. The secondary mixing of the gas is controlled by the carbon dioxide and air mixing automatic control system 121.

[0055] (8) Saturation reaction and automatic control:

[0056] After secondary mixing, the gas enters the saturation tank from the second mixed gas storage tank 114. The first carbon saturation tank enters the No. 1 saturation tank 117 through the first carbon gas regulating valve 115 (equipped with a mixed gas online flow meter 115-1), and the second carbon saturation tank enters the No. 2 saturation tank 119 through the second carbon gas regulating valve 116 (equipped with a mixed gas online flow meter 116-1).

[0057] Before the mixed gas enters the saturation tank, the pH value of the saturated syrup is monitored by an online saturation pH meter 118. The online pH meter 118 is connected to the saturation process automatic control system 122, which is connected to the saturation gas regulating valve 115 to establish an automatic control logic relationship: when the online pH meter 118 detects that the saturation pH value is higher than the set upper limit of 9.5, the control system 122 controls the saturation gas regulating valve 115 to increase the mixed gas flow rate; when the pH value is lower than the set lower limit of 9.0, the control system 122 controls the saturation gas regulating valve 115 to reduce the mixed gas flow rate, so that the pH value of the saturated syrup is stabilized within the range of 9.0-9.5.

[0058] Before the mixed gas enters the saturation tank, the pH value of the carbon 2 saturation syrup is monitored by an online carbon 2 saturation pH meter 120. The online pH meter 120 is connected to the automatic control system 122 of the saturation process, which is in turn connected to the carbon 2 gas regulating valve 116 to establish an automatic control logic relationship: when the online carbon 2 pH meter 120 detects that the carbon 2 saturation pH value is higher than the set upper limit of 8.5, the control system 122 controls the carbon 2 gas regulating valve 116 to increase the mixed gas flow rate; when the pH value is lower than the set lower limit of 8.0, the control system 122 controls the carbon 2 gas regulating valve 116 to reduce the mixed gas flow rate, so that the pH value of the carbon 1 saturation syrup is stabilized within the range of 8.0-8.5.

[0059] The various embodiments of the saturation process of the present invention are shown in Table 1 below.

[0060] Table 1. Process parameters for each embodiment

[0061]

[0062] The saturation decolorization rates of Examples 1, 2, and 3 were 57%, 60%, and 65%, respectively, which are significantly higher than those of the traditional process using flue gas.

[0063] The purity of granulated sugar increased by 0.1%, 0.13%, and 0.2%, respectively.

[0064] As can be seen, compared with the traditional process using flue gas, the process of this embodiment increases the saturation decolorization rate from 55% to 65%, and the impurities in the white sugar are significantly reduced to near zero. For example, after dissolving 20 kg of white sugar and filtering it through an 8μm filter membrane, the bottom color is clean and free of impurities. At the same time, the purity of the white sugar is increased by 0.1-0.2%, the product quality is significantly improved, and the process stability is significantly enhanced, meeting the needs of enterprises to maintain the quality of their old brand of white sugar.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A saturation process using food-grade carbon dioxide as a sugar-clarifying agent, characterized in that, Includes the following steps: S1. Storage of food-grade carbon dioxide Food-grade liquid carbon dioxide is transported to a carbon dioxide storage tank for storage, with a working pressure of 2.0-2.5 MPa. S2. Vaporization of liquid carbon dioxide Liquid carbon dioxide is converted into gaseous carbon dioxide through two vaporizers connected in parallel. The vaporizers use natural heating to completely vaporize the liquid carbon dioxide. S3. Pressure regulation and measurement of gaseous carbon dioxide The vaporized gaseous carbon dioxide is sequentially controlled by two sets of parallel pressure regulating valves to adjust the pressure to 0.30 MPa-0.35 MPa, while the flow rate of gaseous carbon dioxide is controlled by a flow meter. S4. Preparation and Regulation of Compressed Air Compressed air at 0.7 MPa pressure is sequentially passed through two sets of parallel pressure regulating valves to control pressure and flow, adjusting the pressure to 0.15 MPa-0.2 MPa, while the flow rate of the compressed air is controlled by a flow meter. S5. Primary gas mixing The gaseous carbon dioxide adjusted in step S3 and the compressed air adjusted in step S4 are introduced into a static pipeline mixer and mixed at a volume ratio of 1:4-1:

8. S6. Storage and heating of mixed gases The gas after primary mixing enters the gas storage tank for pressure stabilization, and then is heated to 70-80℃ to obtain the initial mixed gas; S7. Secondary mixing of gases Air at a rate of 600-1200 m³ / h is blown into the primary mixed gas using a screw blower, and then the gas is mixed a second time using a Venturi mixer to obtain a mixed gas that meets the process requirements. S8. Saturation reaction and automatic control After secondary mixing, the gas passes through the main regulating valve and then enters the No. 1 saturation tank and the No. 2 saturation tank through the branch regulating valves respectively. Before the mixed gas enters the saturation tank, the pH value of the saturation tank is monitored by an online pH meter to establish a linkage relationship between the online pH meter and the mixed gas flow rate, thereby realizing automatic control of the mixed gas flow rate. In step S8, the automatic control logic is as follows: the pH value of the saturated syrup is controlled between 9.0 and 9.

5. When the online pH meter detects that the pH value of the saturated syrup is higher than 9.5, the mixed gas flow rate is automatically increased; when the online pH meter detects that the pH value of the saturated syrup is lower than 9.0, the mixed gas flow rate is automatically decreased. The pH value of the saturated syrup is controlled between 8.0 and 8.

5. When the online pH meter detects that the pH value of the saturated syrup is higher than 8.5, the mixed gas flow rate is automatically increased; when the online pH meter detects that the pH value of the saturated syrup is lower than 8.0, the mixed gas flow rate is automatically decreased. In step S3, the flow rate of gaseous carbon dioxide is controlled at 100-250 m³ / h; In step S4, the flow rate of compressed air is controlled at 500-1000 m³ / h; In step S7, the total gas volume flow rate after secondary mixing is controlled at 1200-2400 m³ / h.

2. The process according to claim 1, characterized in that, In step S8, each saturated tank is equipped with an independent branch regulating valve at the mixed gas inlet to achieve individual control of the flow rate of a single tank.

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