An apparatus for treating papermaking black liquor

Abstract

A device for processing papermaking black liquor, comprising a pH adjusting tank, a filter and a three-stage evaporator connected in sequence. The pH adjusting tank is provided with a heating jacket, a pH electrode, a flow adding pipeline and a stirring paddle, which is used for acidifying the black liquor to acidic conditions to precipitate lignin. The filter is a basket filter, which is used for retaining the precipitated lignin. The first, second and third evaporators are connected in series, and material pumps are arranged between each evaporator and the outlet of the filter, which ensures smooth conveying of the high-viscosity black liquor. Forced circulation pumps are arranged between the heaters and the evaporation chambers of the second and third evaporators, which prevent scaling and enhance heat transfer. The device removes lignin through acidification pretreatment, combines multi-effect evaporation and forced circulation, realizes efficient concentration and anti-scaling operation of the black liquor, and improves the thermal efficiency and equipment stability.

Description

Technical Field

[0001] This utility model relates to the technical field of papermaking wastewater treatment equipment, and in particular to a device for treating papermaking black liquor. Background Technology

[0002] After chemical cooking, plant fiber raw materials generally yield 50%–80% pulp, with the remaining 20%–50% of the substances dissolved in the cooking liquor. In alkaline pulping, the cooking liquor is black, hence the name "black liquor." The paper industry often uses alkaline agents containing NaOH and Na₂SO₄ to cook plant fibers, resulting in black liquor containing lignin and alkali, which is a highly concentrated and difficult-to-degrade wastewater.

[0003] Papermaking black liquor contains nutrients such as protein and humic acid, which can be used as fertilizers. Therefore, it is often processed into fulvic acid organic fertilizer through evaporation concentration and spray granulation processes, thus realizing the resource utilization of waste liquor. However, black liquor contains a large amount of lignin, which is difficult for plants to absorb directly. It also has a high carbon-nitrogen ratio and degrades slowly in the soil, failing to provide rapid nutrients to crops. If insufficiently decomposed lignin is applied directly to the soil, microorganisms will multiply rapidly during lignin decomposition, competing with crops for available nitrogen in the soil and affecting crop growth. If microbial decomposition is used before concentration and drying, the production cycle will be significantly extended, resulting in low efficiency. Secondly, from a physical perspective, black liquor itself has high viscosity and poor fluidity, making it prone to scaling on heating surfaces during evaporation and concentration, severely affecting heat transfer efficiency, leading to increased energy consumption, frequent equipment cleaning, and shortened operating cycles.

[0004] Therefore, in view of the shortcomings of the existing technology, it is necessary to design a device for treating papermaking black liquor to solve the above problems.

[0005] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solution of this utility model and facilitating the understanding of those skilled in the art. It should not be assumed that the above content is known to those skilled in the art simply because it has been described in the background section of this utility model. Utility Model Content

[0006] To overcome the shortcomings of the prior art, the present invention aims to disclose an apparatus for treating papermaking black liquor.

[0007] This utility model discloses an apparatus for treating papermaking black liquor, comprising:

[0008] pH adjustment tank, the tank body is equipped with a heating jacket;

[0009] The filter's inlet is connected to the outlet of the pH adjustment tank via a pipe;

[0010] The inlet of the first-effect evaporator is connected to the outlet of the filter via a pipe;

[0011] The inlet of the second-effect evaporator is connected to the outlet of the first-effect evaporator via a pipe.

[0012] The inlet of the third-effect evaporator is connected to the outlet of the second-effect evaporator via a pipe.

[0013] Material pumps are installed on the connecting pipes between the filter and the first-effect evaporator, the connecting pipes between the first-effect evaporator and the second-effect evaporator, the connecting pipes between the second-effect evaporator and the third-effect evaporator, and at the output port of the third-effect evaporator.

[0014] Preferred technical solution: The pH adjustment tank is equipped with a pH electrode and a flow pipe for adding pH adjuster.

[0015] Preferred technical solution: A stirring paddle is installed inside the pH adjustment tank.

[0016] Preferred technical solution: The first-effect evaporator includes a first-effect heater and a first-effect evaporator chamber; the second-effect evaporator includes a second-effect heater and a second-effect evaporator chamber; and the third-effect evaporator includes a third-effect heater and a third-effect evaporator chamber; a forced circulation pump is provided between the second-effect heater and the second-effect evaporator chamber, and between the third-effect heater and the third-effect evaporator chamber.

[0017] Preferred technical solution: The filter is a basket filter.

[0018] Due to the application of the above technical solution, the beneficial effects of this utility model compared with the prior art are as follows:

[0019] This invention employs a pH adjustment tank with heating and stirring functions. Through acidification pretreatment, the pH value of the black liquor is adjusted to acidic (e.g., pH=2), allowing lignin to precipitate preferentially. This lignin is then effectively removed by a pre-filter basket filter. This reduces the lignin content in the final concentrate, avoiding the problem of lignin's poor degradation affecting the fertilizer efficiency of organic fertilizer. Material pumps are installed on key material conveying pipelines after filtration and between each evaporator effect, ensuring smooth material flow throughout the entire process from pretreatment to tertiary evaporation, avoiding blockages or poor conveying caused by the high viscosity and poor flowability of the black liquor. Addressing the issue of increased concentrate viscosity and potential scaling in the later stages of evaporation, forced circulation pumps are installed in the heating units of the second and third evaporators. Forced circulation significantly increases the flow rate within the pipes, disrupting the deposition conditions for scaling substances, enhancing heat transfer, extending the continuous operating cycle of the evaporators, and reducing cleaning frequency and energy consumption. The heating jacket of the pH adjusting tank not only controls the temperature required for acidification but also functions as a preheater, ensuring the black liquor is at a certain temperature before entering the first-effect evaporator, thus improving the thermal efficiency of the entire multi-effect evaporation system. A basket filter is used, and the filter basket can be easily removed for cleaning or replacement. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of a device for treating black liquor from papermaking according to this utility model.

[0022] In the attached diagrams above, 1. pH adjustment tank; 11. Heating jacket; 12. pH electrode; 13. Feed pipe; 14. Stirring paddle; 2. Basket filter; 3. First-effect evaporator; 31. First-effect heater; 32. First-effect evaporator chamber; 4. Second-effect evaporator; 41. Second-effect heater; 42. Second-effect evaporator chamber; 5. Third-effect evaporator; 51. Third-effect heater; 52. Third-effect evaporator chamber; 6. Material pump; 7. Forced circulation pump. Detailed Implementation

[0023] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification.

[0024] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate for the purposes of describing embodiments of this application herein. Furthermore, the terms "comprising" and "having," and their synonyms, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0025] In this application, the terms "upper," "lower," "left," "right," "front," "back," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this utility model and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0026] Furthermore, in addition to indicating direction or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this utility model according to the specific circumstances.

[0027] Furthermore, the terms "installation," "setting," "equipped with," "connection," "linking," "fitting," and "fitting" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, components, or parts. Similarly, "fitting" can mean completely or partially fitted. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] Example:

[0030] like Figure 1 As shown, this utility model discloses an apparatus for treating papermaking black liquor, mainly composed of a pretreatment unit and a multi-effect evaporation and concentration unit. The main components of this utility model will be described in detail below:

[0031] The pretreatment unit includes a pH adjustment tank 1 and a basket filter 2. The pH adjustment tank 1 is a vertical tank with a heating jacket 11 on the outside for heating the material inside. A pH electrode 12 and a feed pipe 13 connecting to a pH adjuster storage tank are installed on the top of the pH adjustment tank 1 for online monitoring of the pH value of the papermaking black liquor raw material. The pH adjustment tank 1 is equipped with a motor-driven agitator 14 to ensure that the added pH adjuster is quickly and evenly mixed with the papermaking black liquor raw material.

[0032] The multi-effect evaporation and concentration unit employs a triple-effect evaporator, comprising a first-effect evaporator 3, a second-effect evaporator 4, and a third-effect evaporator 5. The first-effect evaporator 3 consists of a first-effect heater 31 and a first-effect evaporator chamber 32 connected by pipes. The second-effect evaporator 4 consists of a second-effect heater 41 and a second-effect evaporator chamber 42, with a forced circulation pump 7 installed on the connecting pipe between them. The third-effect evaporator 5 consists of a third-effect heater 51 and a third-effect evaporator chamber 52, with a forced circulation pump 7 also installed on the connecting pipe between them.

[0033] The connections of the apparatus are as follows: The bottom outlet of the pH adjustment tank 1 is connected to the inlet of the basket filter 2 via a pipe. The purified liquid outlet of the basket filter 2 is connected to the material inlet of the first-effect evaporator 3 (specifically, the material inlet of the first-effect heater 31) via a pipe, and a first material pump 6 is installed on this connecting pipe. The concentrated liquid outlet of the first-effect evaporator 3 (located in the first-effect evaporator chamber 32) is connected to the second-effect evaporator 4 (specifically, the material inlet of the second-effect heater 41) via a pipe, and a second material pump 6 is installed on this pipe. The concentrated liquid outlet of the second-effect evaporator 4 (located in the second-effect evaporator chamber 42) is connected to the third-effect evaporator 5 (specifically, the material inlet of the third-effect heater 51) via a pipe, and a third material pump 6 is installed on this pipe. The final concentrated liquid outlet of the third-effect evaporator 5 (located in the third-effect evaporator chamber 52) is equipped with a fourth material pump 6 for outputting the finished concentrated liquid.

[0034] The work process is as follows:

[0035] Papermaking black liquor raw material from the alkali recovery section or storage tank of a paper mill is fed into pH adjustment tank 1. The agitator 14 is started, and a pH adjuster is quantitatively added into the tank through the feed pipe 13. Simultaneously, the pH value of the papermaking black liquor raw material is adjusted to approximately 2.0 by monitoring feedback through the pH electrode 12, allowing lignin to fully precipitate and form fine suspended particles. During this process, the heating jacket 11 is turned on to preheat the papermaking black liquor raw material.

[0036] The treated black liquor raw material flows through basket filter 2, where the precipitated lignin particles are retained by the filter basket, resulting in a relatively clear black liquor. The black liquor is pressurized and pumped by the first material pump 6 to the first-effect heater 31 of the first-effect evaporator 3. Steam generated by the heating tubes of the first-effect heater 31 enters the first-effect evaporator chamber 32 for separation. The concentrated black liquor produced by the first-effect evaporator 3 is sent to the second-effect evaporator 4 by the second material pump 6.

[0037] The concentrated black liquor entering the second-effect heater 41 of the second-effect evaporator 4 is heated using the secondary steam generated in the first effect as a heat source. Driven by the forced circulation pump 7, the concentrated black liquor circulates at high speed between the second-effect heater 41 and the second-effect evaporator chamber 42, effectively preventing scaling and improving evaporation intensity. The concentrated black liquor produced by the second-effect evaporator 4 is sent to the third-effect evaporator 5 by the third material pump 6.

[0038] The concentrated black liquor entering the triple-effect heater 51 of the third-effect evaporator 5 is heated using the secondary steam generated by the second-effect evaporator 4 as a heat source. Driven by the forced circulation pump 7, the concentrated black liquor circulates at high speed between the triple-effect heater 51 and the triple-effect evaporator chamber 52, effectively preventing scaling and improving evaporation intensity. The concentrated black liquor produced by the third-effect evaporator 5 is discharged from the bottom of the triple-effect evaporator chamber 52 by the fourth material pump 6 and sent to the subsequent organic fertilizer granulation section. The secondary steam generated by each evaporator chamber is used as a heat source for the next effect, while the secondary steam from the last effect enters the condensation system for condensation.

[0039] Finally, it should be noted that the above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An apparatus for treating papermaking black liquor, characterized in that, include: pH adjustment tank, the tank body is equipped with a heating jacket; The filter has its inlet connected to the outlet of the pH adjustment tank via a pipe; The inlet of the first-effect evaporator is connected to the outlet of the filter via a pipe; The inlet of the second-effect evaporator is connected to the outlet of the first-effect evaporator via a pipe. The inlet of the third-effect evaporator is connected to the outlet of the second-effect evaporator via a pipe. Material pumps are installed on the connecting pipe between the filter and the first-effect evaporator, the connecting pipe between the first-effect evaporator and the second-effect evaporator, the connecting pipe between the second-effect evaporator and the third-effect evaporator, and at the output port of the third-effect evaporator.

2. The apparatus for treating papermaking black liquor according to claim 1, characterized in that: The pH adjustment tank is equipped with a pH electrode and a flow pipe for adding pH adjuster.

3. The apparatus for treating papermaking black liquor according to claim 1, characterized in that: The pH adjustment tank is equipped with a stirring paddle.

4. The apparatus for treating papermaking black liquor according to claim 1, characterized in that: The first-effect evaporator includes a first-effect heater and a first-effect evaporator chamber; the second-effect evaporator includes a second-effect heater and a second-effect evaporator chamber; and the third-effect evaporator includes a third-effect heater and a third-effect evaporator chamber. Forced circulation pumps are provided between the second-effect heater and the second-effect evaporator chamber, and between the third-effect heater and the third-effect evaporator chamber.

5. The apparatus for treating papermaking black liquor according to claim 1, characterized in that: The filter is a basket filter.

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