Gasifier black water recycling process

Abstract

The present application relates to the technical field of industrial chemistry, and discloses a gasifier black water recycling process. The process mainly solves the problems of high energy consumption, low heat exchange efficiency caused by fouling and insufficient utilization of waste heat in the direct treatment of low-flash black water from a gasifier. The process steps include: introducing the low-flash black water generated by the gasifier into a pretreatment unit, injecting a composite scale inhibitor into the unit, and mixing to form a homogeneous dispersion system; sending the pretreated black water into a black water heat exchanger for indirect heat exchange with closed-circulation desalted water, the heated desalted water enters an ORC low-temperature generator set, and energy conversion is completed through an organic working medium circulation system to realize the conversion of heat energy into electric energy; the composite scale inhibitor is prepared by copolymer solution synthesis, modified additive preparation, and compounding with sodium polyepoxysuccinic acid and modified sodium lignosulfonate. The present application effectively prevents fouling of the heat exchanger, significantly improves the heat exchange efficiency and the stability of the system operation, and realizes efficient recovery and resource utilization of the waste heat in the black water.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial chemistry, more particularly, it relates to a gasifier black water recycling process. BACKGROUND

[0002] In the field of industrial production, the gasifier is an important energy conversion equipment, and a large amount of low-flash black water will be generated during its operation. This kind of black water not only contains a large amount of solid impurities, but also carries a certain amount of heat energy. If not properly treated, it will not only cause energy waste, but also may cause subsequent equipment operation problems.

[0003] At present, the conventional treatment method for low-flash black water in the industry is to directly introduce it into a vacuum flash device for treatment. In this process, the heat energy contained in the black water is not effectively recovered, resulting in significant energy loss. At the same time, the vacuum flash process needs to rely on the continuous operation of the vacuum pump set, which consumes a large amount of electric energy and increases the production energy consumption. More importantly, due to the high content of solid impurities in the black water, it is easy to form scale deposition on the inner wall of the related equipment during the treatment and transportation process. This scaling phenomenon will cause the heat exchange efficiency of the heat exchange equipment to decrease significantly, which not only affects the stable operation of the system, but also needs to be cleaned and maintained frequently, further increasing the production cost and operation complexity. In addition, the pretreatment measures for black water in the existing treatment process are single, which cannot effectively solve the scaling problem, resulting in the stability of the long-term operation of the heat exchange system cannot be guaranteed, which restricts the resource utilization of the waste heat in the black water. Therefore, the present application provides a gasifier black water recycling process to solve the above technical problems. SUMMARY

[0004] The purpose of the present application is to provide a gasifier black water recycling process, which can effectively prevent the scaling of the heat exchanger, significantly improve the heat exchange efficiency and the stability of the system operation, and realize the efficient recovery and resource utilization of the waste heat in the black water.

[0005] The present application provides a gasifier black water recycling process, which adopts the following technical scheme:

[0006] (1) The low-flash black water generated by the gasifier is introduced into the pretreatment unit, the black water flow is controlled to be 280-320 m³ / h, the temperature is controlled to be 128-135℃, the composite scale inhibitor is injected into the black water fluid, the addition concentration is 50-200 mg / L, the injection time is 5-10 min, and the homogeneous dispersion system is ensured by fully mixing;

[0007] (2) The pretreated black water enters the titanium alloy black water heat exchanger, and the non-contact heat exchange is carried out with the closed circulating desalted water. The residence time of the black water side in the heat exchange process is controlled to be 8-15 min, the desalted water flow is adjusted to be 300-340 m³ / h, and the temperature after heat exchange is increased to 110-125℃.

[0008] Preferably, the preparation step of the composite scale inhibitor in step (1) is:

[0009] S1, dissolve pectin in deionized water, add sodium tripolyphosphate and sodium aspartate, adjust pH to 5-6, add KH-550 and pyridine at 48-52℃, incubate for 3-5h, adjust pH to neutral, precipitate, filter, wash, vacuum dry to obtain modified additive;

[0010] S2, dissolve itaconic acid, 2-acrylamido-2-methylpropane sulfonic acid, glycidyl methacrylate, itaconic acid monomethyl ester and modified additive in mixed solvent, under nitrogen protection, add initiator dropwise at 70-75℃ for 30-35min, then add 3-mercaptopropionic acid, heat to 75-80℃ for 2-4h to obtain copolymer solution;

[0011] S3, react copolymer solution, sodium polyepoxysuccinate and modified lignin sulfonate sodium at 25-30℃ for 30-35min, adjust pH to 7-8, continue stirring for 20-25min to obtain scale inhibitor.

[0012] Preferably, the preparation step of the modified lignin sulfonate in step S3 is: dissolve sodium lignin sulfonate in 8-10% NaOH and 25-30% H2O2, react at 60-65℃ for 3-4h, then cool to 45-50℃, add mixed solution containing acrylic acid and ammonium persulfate dropwise, incubate for 2-4h, continue to add epichlorohydrin, react at 65-70℃ for 1-2h, then spray dry to obtain modified lignin sulfonate.

[0013] Preferably, in S1, the weight parts are 5-6 parts of pectin, 35-40 parts of deionized water, 0.5-0.7 parts of sodium tripolyphosphate, 0.9-1.2 parts of sodium aspartate, 8-12 parts of KH-550 and 0.2-0.4 parts of pyridine.

[0014] Preferably, in step S1, the mixed solvent consists of 60-70 parts of deionized water and 30-40 parts of ethanol, and the initiator consists of 1.5-2 parts of potassium persulfate and 8-10 parts of water.

[0015] Preferably, in step S2, the weight parts are 22-28 parts of itaconic acid, 10-15 parts of 2-acrylamido-2-methylpropane sulfonic acid, 5-8 parts of glycidyl methacrylate, 3-5 parts of itaconic acid monomethyl ester, 5-8 parts of modified additive, 90-110 parts of mixed solvent, 9.5-12 parts of initiator and 1-1.5 parts of 3-mercaptopropionic acid.

[0016] Preferably, in step S3, the weight parts are 35-40 parts of copolymer solution, 3-5 parts of sodium polyepoxysuccinate and 2-3 parts of modified lignin sulfonate sodium.

[0017] Preferably, in the preparation step of the modified sodium lignin sulfonate, 10-15 parts of sodium lignin sulfonate, 14-16 parts of NaOH, 20-23 parts of H2O2, 5-10 parts of acrylic acid, 1-3 parts of ammonium persulfate and 6-8 parts of epichlorohydrin are used.

[0018] Preferably, in the step (2), the residence time of the heat exchange process is controlled to be 8-15 min, the desalted water flow is adjusted to be 300-340 m³ / h, and the temperature is raised to 110-125 °C after heat exchange, and the wall surface temperature gradient of the heat exchanger is maintained to be stable at 30-35 °C during the heat exchange process.

[0019] In summary, the present application has the following beneficial effects:

[0020] 1. In the present application, the low-flash black water from the gasification furnace is introduced into the pretreatment unit and injected into the composite scale inhibitor to form a homogeneous dispersion system, and then indirectly exchanges heat with the closed-circulation desalted water through the black water heat exchanger, and the heat energy is converted into electric energy by using the ORC low-temperature generator set to form a complete black water recycling process. Through the synergistic design of pretreatment-heat exchange-energy conversion, the present application effectively solves the problem of high energy consumption in the direct treatment of low-flash black water in the prior art, and by combining indirect heat exchange with ORC power generation technology, the present application realizes the efficient recovery and resource utilization of low-grade waste heat in black water, and significantly improves the energy utilization efficiency. At the same time, by cooperating the scale inhibition pretreatment with the special heat exchange equipment, the present application avoids the decrease of heat exchange efficiency caused by fouling in the heat exchange system, ensures the long-term stable operation of the system, reduces the equipment maintenance cost, and the overall process has good energy saving and economic efficiency.

[0021] 2. The composite scale inhibitor of the present application is synthesized by copolymer solution of itaconic acid, 2-acrylamido-2-methylpropane sulfonic acid and other monomers, and then prepared into a modified auxiliary agent with pectin, and compounded with polyepoxysuccinic acid sodium and modified sodium lignin sulfonate. The composite scale inhibitor forms a multi-component synergistic system by the dispersion and lattice distortion effect of the copolymer, the chelation performance of the modified auxiliary agent, the scale inhibition characteristics of the polyepoxysuccinic acid sodium and the dispersion synergistic effect of the modified sodium lignin sulfonate, which can effectively inhibit the deposition of calcium, magnesium and other scale components in the heat exchange process of black water. The functional groups in the copolymer molecules can combine with scale ions and destroy the crystal growth, the modified auxiliary agent can enhance the capture ability of metal ions through chelation, and the synergistic effect of the compounded components can significantly improve the scale inhibition efficiency, greatly reduce the risk of fouling of the heat exchanger, and ensure the efficient progress of the heat exchange process, which provides a key guarantee for the stable recovery of waste heat in black water. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0023] In the following examples, the experimental methods are conventional methods, and the experimental materials used are purchased from conventional biochemical reagent stores, unless otherwise specified. In the quantitative tests in the following examples, three repeated experiments are set, and the data are the average value or average value ± standard deviation of the three repeated experiments.

[0024] KH-550, purchased from Shanghai Notai Chemical Co., Ltd.;

[0025] Example 1

[0026] A gasifier black water recycling process adopts the following technical solutions:

[0027] (1) The low-flash black water generated by the gasifier is introduced into a pretreatment unit, the black water flow is controlled to be 280 m³ / h, the temperature is controlled to be 128℃, a composite scale inhibitor is injected into the black water fluid, the addition concentration is 50 mg / L, the injection time is 5 min, and sufficient mixing is ensured to form a homogeneous dispersion system;

[0028] (2) The pretreated black water enters a black water heat exchanger made of titanium alloy material, and performs non-contact heat exchange with the closed-circulation desalted water, the residence time of the black water side in the heat exchange process is controlled to be 8 min, the desalted water flow is adjusted to be 300 m³ / h, and the temperature of the desalted water after heat exchange is increased to 110℃.

[0029] The preparation step of the composite scale inhibitor in step (1) is as follows:

[0030] S1, 5 parts of pectin are dissolved in 35 parts of deionized water, 0.5 parts of sodium tripolyphosphate and 0.9 parts of sodium aspartate are added, the pH is adjusted to 5, 8 parts of KH-550 and 0.2 parts of pyridine are added at a stirring speed of 400 rpm at 48℃, the pH is adjusted to neutral after 5h of heat preservation reaction, and the modified additive is obtained by precipitation, filtration, washing and vacuum drying;

[0031] S2, 22 parts of itaconic acid, 10 parts of 2-acrylamido-2-methylpropanesulfonic acid, 5 parts of glycidyl methacrylate, 3 parts of itaconic acid monomethyl ester and 5 parts of the modified additive are dissolved in a mixed solvent composed of 60 parts of deionized water and 30 parts of ethanol, an initiator composed of 1.5 parts of potassium persulfate and 8 parts of water is added dropwise under nitrogen protection at a stirring speed of 400 rpm at 70℃ for 30 min, 1 part of 3-mercaptopropionic acid is further added, the temperature is increased to 75℃, and the reaction is carried out for 4h to obtain a copolymer solution.

[0032] S3, stirring 35 parts of copolymer solution, 3 parts of sodium polyepoxysuccinate and 2 parts of modified sodium lignosulfonate at 350 rpm stirring speed at 25℃ for 35 min, adjusting pH to 7, continuing stirring for 25 min to obtain scale inhibitor.

[0033] The preparation step of modified lignosulfonic acid in step S3 is: dissolving 10 parts of sodium lignosulfonate in 14 parts of 10% NaOH and 20 parts of 30% H2O2, reacting at 60℃ for 4h at 350 rpm stirring speed, then cooling to 45℃, adding dropwise a mixed solution containing 5 parts of acrylic acid and 1 part of ammonium persulfate, incubating for 4h, then adding 6 parts of epichlorohydrin, reacting at 65℃ for 2h, and then spray drying to obtain modified lignosulfonic acid.

[0034] Example 2

[0035] A gasifier black water recycling process adopts the following technical scheme:

[0036] (1) The low-flash black water generated by the gasifier is introduced into a pretreatment unit, the black water flow is controlled at 290 m³ / h, the temperature is 124℃, a composite scale inhibitor is injected into the black water fluid, the addition concentration is 80 mg / L, the injection time is 7 min, and sufficient mixing is ensured to form a homogeneous dispersion system;

[0037] (2) The pretreated black water enters a black water heat exchanger made of titanium alloy material, and is subjected to non-contact heat exchange with desalted water in closed circulation, the residence time of the black water side in the heat exchange process is controlled at 10 min, and the desalted water flow is adjusted to 320 m³ / h, and the temperature after heat exchange is increased to 115℃.

[0038] The preparation step of the composite scale inhibitor in step (1) is:

[0039] S1, dissolving 5.2 parts of pectin in deionized water, adding 0.6 parts of sodium tripolyphosphate and 1 part of sodium aspartate, adjusting pH to 5.2, adding 10 parts of KH-550 and 0.3 parts of pyridine at 430 rpm stirring speed at 50℃, incubating for 4.7h, adjusting pH to neutral, and then performing precipitation, filtration, washing and vacuum drying to obtain a modified additive;

[0040] S2, dissolving 24 parts of itaconic acid, 12 parts of 2-acrylamido-2-methylpropane sulfonic acid, 7 parts of glycidyl methacrylate, 4 parts of itaconic acid monomethyl ester and 6 parts of modified additive in a mixed solvent composed of 64 parts of deionized water and 33 parts of ethanol, adding dropwise an initiator composed of 1.8 parts of potassium persulfate and 9 parts of water at 440 rpm stirring speed under nitrogen protection at 73℃ for 33 min, then adding 1.2 parts of 3-mercaptopropionic acid, increasing the temperature to 77℃ for 3.8h to obtain a copolymer solution;

[0041] S3, stirring 36 parts of copolymer solution, 4 parts of sodium polyepoxysuccinate and 2.2 parts of modified sodium lignosulfonate at a stirring speed of 370 rpm at 27℃ for 34 min, adjusting pH to 7.3, and continuing to stir for 24 min to obtain the scale inhibitor.

[0042] The preparation step of the modified lignosulfonic acid in step S3 is as follows: dissolving 10-15 parts of sodium lignosulfonate in 15 parts of 9% NaOH and 22 parts of 28% H2O2, reacting at 64℃ for 3.8 h at a stirring speed of 370 rpm, then cooling to 48℃, dropwise adding a mixed solution containing 6 parts of acrylic acid and 2 parts of ammonium persulfate, and reacting for 3.8 h, then continuously adding 7 parts of epichlorohydrin, reacting at 68℃ for 1.8 h, and then spray drying to obtain the modified lignosulfonic acid.

[0043] Example 3

[0044] A gasifier black water recycling process adopts the following technical scheme:

[0045] (1) The low-flash black water generated by the gasifier is introduced into a pretreatment unit, the black water flow is controlled at 320 m³ / h, the temperature is 135℃, a composite scale inhibitor is injected into the black water fluid, the addition concentration is 200 mg / L, the injection time is 10 min, and sufficient mixing is ensured to form a homogeneous dispersion system;

[0046] (2) The pretreated black water enters a black water heat exchanger made of titanium alloy material, and performs non-contact heat exchange with the closed circulating desalted water, the residence time of the black water side in the heat exchange process is controlled at 15 min, and the desalted water flow is adjusted to 340 m³ / h, and the temperature of the black water after heat exchange is increased to 125℃.

[0047] The preparation step of the composite scale inhibitor in step (1) is as follows:

[0048] S1, dissolving 6 parts of pectin in deionized water, adding 0.7 parts of sodium tripolyphosphate and 1.2 parts of sodium aspartate, adjusting pH to 6, adding 12 parts of KH-550 and 0.4 parts of pyridine at a stirring speed of 500 rpm at 52℃, adjusting pH to neutral after reacting for 3 h, and then performing precipitation, filtration, washing, and vacuum drying to obtain the modified additive;

[0049] S2, dissolving 28 parts of itaconic acid, 15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 8 parts of glycidyl methacrylate, 5 parts of itaconic acid monomethyl ester, and 8 parts of the modified additive in a mixed solvent composed of 70 parts of deionized water and 40 parts of ethanol, dropwise adding an initiator composed of 2 parts of potassium persulfate and 10 parts of water under nitrogen protection at a stirring speed of 500 rpm at 75℃ for 30 min, then adding 1.5 parts of 3-mercaptopropionic acid, and reacting at 80℃ for 2 h to obtain the copolymer solution;

[0050] S3, stirring 40 parts of the copolymer solution, 5 parts of sodium polyepoxysuccinic acid and 3 parts of modified sodium lignosulfonate at 30℃ for 30 min at a stirring speed of 450 rpm, adjusting the pH to 8, and continuing to stir for 20 min to obtain the scale inhibitor.

[0051] The preparation step of the modified sodium lignosulfonate in step S3 is as follows: 15 parts of sodium lignosulfonate are dissolved in 16 parts of 8% NaOH and 23 parts of 25% H2O2, and reacted at 65℃ for 3 h at a stirring speed of 400 rpm, then cooled to 50℃, and a mixed solution containing 10 parts of acrylic acid and 3 parts of ammonium persulfate is added dropwise, and reacted for 2 h, then 8 parts of epichlorohydrin is added, and reacted at 70℃ for 1 h, and then spray dried to obtain the modified sodium lignosulfonate.

[0052] Example 4

[0053] A gasifier black water recycling process adopts the following technical scheme:

[0054] (1) The low-flash black water generated by the gasifier is introduced into a pretreatment unit, the black water flow is controlled to be 320 m³ / h, the temperature is 128℃, a composite scale inhibitor is injected into the black water fluid, the addition concentration is 100 mg / L, the injection time is 8 min, and sufficient mixing is ensured to form a homogeneous dispersion system;

[0055] (2) The pretreated black water enters a black water heat exchanger made of titanium alloy material, and performs non-contact heat exchange with desalted water in closed circulation, the residence time of the black water side in the heat exchange process is controlled to be 15 min, and the desalted water flow is adjusted to be 320 m³ / h, and the temperature after heat exchange is increased to 115℃.

[0056] The preparation step of the composite scale inhibitor in step (1) is as follows:

[0057] S1, 6 parts of pectin are dissolved in deionized water, 0.6 parts of sodium tripolyphosphate and 1 part of sodium aspartate are added, the pH is adjusted to 5.5, 12 parts of KH-550 and 0.3 parts of pyridine are added at a stirring speed of 480 rpm at 50℃, and the pH is adjusted to neutral after 4 h of heat preservation reaction, and then the modified additive is obtained by precipitation, filtration, washing and vacuum drying;

[0058] S2, 28 parts of itaconic acid, 15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 8 parts of glycidyl methacrylate, 4 parts of itaconic acid monomethyl ester and 6 parts of the modified additive are dissolved in a mixed solvent composed of 70 parts of deionized water and 40 parts of ethanol, an initiator composed of 2 parts of potassium persulfate and 10 parts of water is added dropwise under nitrogen protection at a stirring speed of 500 rpm at 75℃ for 30 min, 1.5 parts of 3-mercaptopropionic acid is added, the temperature is increased to 80℃, and the reaction is carried out for 3 h to obtain the copolymer solution.

[0059] S3, stirring 40 parts of copolymer solution, 4 parts of sodium polyepoxysuccinate and 2.5 parts of modified sodium lignosulfonate at a stirring speed of 450 rpm at 28℃ for 32 min, adjusting pH to 7.5, and continuing to stir for 20 min to obtain the scale inhibitor.

[0060] In the step S3, the modified lignosulfonic acid is prepared by dissolving 15 parts of sodium lignosulfonate in 16 parts of 9% NaOH and 20 parts of 28% H2O2, reacting at 65℃ for 3.2 h at a stirring speed of 400 rpm, cooling to 50℃, adding a mixture containing 10 parts of acrylic acid and 2 parts of ammonium persulfate dropwise, and reacting for 2.6 h, then adding 7 parts of epichlorohydrin, and reacting at 70℃ for 1.3 h, and then spray drying to obtain the modified lignosulfonic acid.

[0061] Comparative Example 1

[0062] A gasifier black water recycling process, which is different from Example 4 in that no composite scale inhibitor is added, i.e. no composite scale inhibitor is added in step (1), and the heat exchange reaction is directly carried out, and other conditions are the same as those of Example 4.

[0063] Comparative Example 2

[0064] A gasifier black water recycling process, which is different from Example 4 in that step S3 in the preparation of the composite scale inhibitor is not carried out, i.e. only steps S1 and S2 are completed to prepare the copolymer solution and it is directly used as a scale inhibitor, and other conditions are the same as those of Example 4.

[0065] Comparative Example 3

[0066] A gasifier black water recycling process, which is different from Example 4 in that no modified additive is added in the preparation process of the composite scale inhibitor, i.e. step S1 for preparing the copolymer solution without the modified additive is omitted, and the copolymer solution prepared by step S1 without the modified additive is used to prepare the composite scale inhibitor by step S3, and other conditions are the same as those of Example 4.

[0067] Comparative Example 4

[0068] A method for preparing a composite scale inhibitor in a gasifier black water recycling process, which is different from Example 4 in that sodium lignosulfonate is used instead of modified sodium lignosulfonate in the preparation process of the composite scale inhibitor, i.e. only 2.5 parts of lignin is directly used as modified sodium lignosulfonate in step S3, and other conditions are the same as those of Example 4.

[0069] Comparative Example 5

[0070] A method for preparing a composite scale inhibitor in a gasifier black water recycling process, which is different from Example 4 in that no itaconic acid monomethyl ester is added in the preparation of the composite scale inhibitor, i.e. 4 parts of itaconic acid monomethyl ester is omitted in step S1, and other conditions are the same as those of Example 4.

[0071] Comparative Example 6

[0072] A preparation method of a composite scale inhibitor in a gasifier black water recycling process, which is different from Example 4 in that no sodium polyepoxysuccinate is added in the preparation of the composite scale inhibitor, that is, 4 parts of sodium polyepoxysuccinate are omitted in step S3, and other conditions are the same as those in Example 4.

[0073] Performance test

[0074] The gasifier black water recycling processes of Examples 1-4 and Comparative Examples 1-6 were subjected to performance tests, and the test results are shown in Table 1.

[0075] Table 1

[0076] Test item Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Scale inhibition rate 94.27 93.98 91.66 90.83 0 70.88 76.45 79.07 82.61 85.09 Heat transfer coefficient retention rate 92.59 93.84 95.31 96.55 62.37 78.84 82.12 84.37 86.74 88.96

[0077] The gasifier black water recycling processes of Examples 1-4 exhibit excellent scale inhibition effect and heat exchange stability, with scale inhibition rates of more than 90% and heat transfer coefficient retention rates of more than 92%. This is due to the synergistic effect of the components in the process, the dispersion and lattice distortion of the composite scale inhibitor through the copolymer, the chelation of the modification aid, the scale inhibition properties of sodium polyepoxysuccinate, and the dispersion enhancement of modified sodium lignosulfonate, which effectively inhibits the deposition of calcium, magnesium and other components in the black water on the surface of the heat exchanger, reduces the influence of scale on heat exchange efficiency, thereby maintaining a high heat transfer coefficient and ensuring efficient operation of the waste heat recovery system.

[0078] The performance data of the comparative examples are significantly lower than those of the examples. Comparative Example 1 completely loses scale inhibition ability due to the absence of a composite scale inhibitor, resulting in severe scale formation on the surface of the heat exchanger and a significant decrease in heat transfer coefficient; Comparative Example 2 does not perform the compounding step, and the single copolymer cannot fully play a scale inhibition role, resulting in a significant reduction in effect; Comparative Example 3 lacks a modification aid, which weakens the overall scale inhibition ability; Comparative Example 4 uses unmodified sodium lignosulfonate, which has insufficient dispersion performance and weakens the synergistic effect; Comparative Example 5 does not add monomethyl itaconate, and the copolymer structure is incomplete, affecting the dispersion and scale inhibition effect; and Comparative Example 6 lacks sodium polyepoxysuccinate, which loses its unique scale inhibition contribution, and the overall synergistic system is destroyed.

[0079] The above content is merely an example and description of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, as long as they do not deviate from the scope of the invention or exceed the scope defined by the present claims.

Claims

1. A gasifier black water recycling process, characterized by, The method comprises the following steps: (1) introducing low-flash black water generated by a gasification furnace into a pretreatment unit, controlling the black water flow rate to be 280-320 m³ / h and the temperature to be 128-135℃, injecting a composite scale inhibitor into the black water flow, and fully mixing to form a homogeneous dispersion system; (2) sending the pretreated black water into a heat exchanger to perform indirect heat exchange with desalted water in closed circulation, sending the heated desalted water into an ORC low-temperature generator set to complete the evaporation, expansion and condensation processes in the organic working medium circulation system, and realizing the conversion of heat energy into electric energy; In the step (1), the preparation steps of the composite scale inhibitor are as follows: S1, dissolving pectin in deionized water, adding sodium tripolyphosphate and sodium aspartate, adjusting pH, adding KH-550 and pyridine, adjusting pH to neutral after heat preservation reaction, and obtaining a modified additive through precipitation, filtration, washing and vacuum drying; S2, dissolving itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, glycidyl methacrylate, itaconic acid monomethyl ester and the modified additive in a mixed solvent, adding an initiator dropwise under nitrogen protection, adding 3-mercaptopropionic acid, and obtaining a copolymer solution through heat reaction; S3, reacting the copolymer solution, polyepoxysuccinic acid sodium and modified lignin sulfonate sodium, adjusting pH, and continuing to stir to obtain the scale inhibitor; In the step S3, the preparation steps of the modified lignin sulfonate sodium are as follows: dissolving lignin sulfonate sodium in 8-10% NaOH and 25-30% H2O2, cooling after reaction, dropwise adding a mixed solution containing acrylic acid and ammonium persulfate, continuing to add epichlorohydrin after heat preservation reaction, and obtaining the modified lignin sulfonate sodium through spray drying after reaction.

2. The gasifier blackwater recycling process of claim 1, wherein, In the step S1, the components are as follows in terms of weight parts: 5-6 parts of pectin, 35-40 parts of deionized water, 0.5-0.7 parts of sodium tripolyphosphate, 0.9-1.2 parts of sodium aspartate, 8-12 parts of KH-550 and 0.2-0.4 parts of pyridine.

3. The gasifier blackwater recycling process of claim 1, wherein, In the step S2, the mixed solvent is composed of 60-70 parts of deionized water and 30-40 parts of ethanol, and the initiator is composed of 1.5-2 parts of potassium persulfate and 8-10 parts of water.

4. The gasifier blackwater recycling process of claim 1, wherein, In the step S2, the components are as follows in terms of weight parts: 22-28 parts of itaconic acid, 10-15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 5-8 parts of glycidyl methacrylate, 3-5 parts of itaconic acid monomethyl ester, 5-8 parts of the modified additive, 90-110 parts of the mixed solvent, 9.5-12 parts of the initiator and 1-1.5 parts of 3-mercaptopropionic acid.

5. The gasifier black water recycling process of claim 1, wherein, In the step S3, the components are as follows in terms of weight parts: 35-40 parts of the copolymer solution, 3-5 parts of polyepoxysuccinic acid sodium and 2-3 parts of the modified lignin sulfonate sodium.

6. The gasifier black water recycling process of claim 1, wherein, In the preparation steps of the modified lignin sulfonate sodium, the components are as follows in terms of weight parts: 10-15 parts of lignin sulfonate sodium, 14-16 parts of NaOH, 20-23 parts of H2O2, 5-10 parts of acrylic acid, 1-3 parts of ammonium persulfate and 6-8 parts of epichlorohydrin.

7. The gasifier blackwater recycling process of claim 1, wherein, The residence time of the black water side in the heat exchange process in step (2) is 8-15 min, the flow rate of the desalted water is adjusted to 300-340 m3 / h, and the temperature is raised to 110-125℃ after heat exchange. The temperature gradient of the wall surface of the heat exchanger is maintained at 30-35℃ during the heat exchange process.