Method for treating coal gasification black water

Abstract

The invention provides a coal gasification black water treatment method. Comprising the following steps: S1, carrying out multi-stage flash evaporation on coal gasification black water to obtain a first residual liquid; s2, a first water treatment agent is added into the first residual liquid for a reaction, and first reaction liquid is obtained; s3, enabling the first reaction liquid to pass through a final-stage flash evaporation pump of multi-stage flash evaporation to obtain second residual liquid; s4, a second water treatment agent is added into the second residual liquid for a reaction, and second reaction liquid is obtained; s5, after the second reaction liquid enters a clarifying tank to be subjected to sedimentation treatment, supernatant liquid and sediment are obtained; the first water treatment agent is an inorganic coagulant, and the second water treatment agent is an organic polymeric flocculant. The method has certain hardness and silicon removal performance while reducing the turbidity of the coal gasification black water and reducing suspended solids in the coal gasification black water, can effectively improve the water quality of the gasification circulating grey water, and greatly improves the operability and stability of industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of coal chemical industry, and in particular to a method for treating coal gasification black water. Background Art

[0002] Coal gasification is the main way to efficiently and cleanly utilize coal, and is a key common technology in the field of clean coal technology. However, during the cooling and washing of raw coal gas in the coal gasification process, a large amount of black water will be produced. Its main components include suspended solid particles (solid substances such as ash and unreacted coal particles in the gasification process), ammonia nitrogen, hardness (i.e. metal ions), COD, cyanide and other harmful substances.

[0003] In order to reduce the environmental damage of coal gasification black water and improve the utilization rate of water resources, the industry usually reuses black water by adding flocculants. However, coal gasification black water has the characteristics of high silicon, high hardness, high solid content and high suspended matter content, and is affected by factors such as coal quality, gasification process, and operating conditions. Its water quality and the form of substances in the water fluctuate greatly. Therefore, in its treatment process, the types and requirements of reagents for coagulation, flocculation, and dispersion in the water system are different.

[0004] At present, in the gasification black water treatment process, industrial production generally only performs black water flocculation and sedimentation treatment by adding a single type of flocculant at the inlet of the sedimentation tank. The poor flocculation effect often causes frequent scaling and clogging of the equipment and pipelines of the coal gasification water system. At the same time, even if the flocculation effect can be guaranteed, the high hardness and high silicon content of the regenerated black water also restrict the stable operation of the gasification water system. Therefore, the development of a flocculant with strong water quality adaptability and certain softening and silicon removal performance is of great significance to improving the continuous and stable operation of the gasification water system. Patent application CN116789876A discloses a blended polymer flocculant and its preparation method and its application in mud flocculation and dehydration treatment, which relates to a blended polymer copolymer and its preparation method, as well as a mud treatment system method using a blended flocculant jet mixing combined with vacuum preloading. This technical solution is mainly aimed at mud dehydration of high-water content sludge, but cannot achieve flocculation and clarification for coal gasification black water, and has a long operation time and is difficult to match with the coal gasification black water system. Patent CN114477404B provides a method for preparing a sewage flocculant, which uses polyaluminium chloride, polyacrylamide, aluminium sulfate and coconut modified fibre as raw materials. The prepared flocculant has a high compactness of the sedimentation flocs formed during use and is not easy to disperse during subsequent treatment. The preparation process of this invention involves acid-base boiling and soaking and other processes, which is complicated to operate, and the product quality is not easy to guarantee. In addition, the raw material of coconut modified fibre has obvious regional restrictions and is not easy to obtain. Patent CN116854215A discloses a coal slime water treatment agent and its preparation method and application. This coal slime water treatment agent includes a coagulant G and a flocculant F prepared separately. When used, the coagulant G is first added to micro-treat and pre-flocculate the coal slime water, and then the flocculant F is added to strengthen the flocculation, which synergistically promotes the flocculation and sedimentation of suspended matter. The flocculant disclosed in this invention has a complex composition, which is not conducive to large-scale continuous online operation, and the suspended matter content of the treated supernatant is still higher than 50mg / L, which still cannot meet the reuse requirements of gasified black water.

[0005] Based on this, how to provide a method for treating coal gasification black water to achieve effective treatment of coal gasification black water is one of the important technical problems that need to be solved in this field. Summary of the invention

[0006] The main purpose of the present invention is to provide a method for treating coal gasification black water to solve the problem of poor treatment effect of coal gasification black water in the prior art.

[0007] In order to achieve the above-mentioned purpose, the present invention provides a method for treating coal gasification black water, which comprises: step S1, performing a first multi-stage flash evaporation on the coal gasification black water, and obtaining a first flash gas and a first residual liquid after cooling; step S2, adding a first water treatment agent to the first residual liquid for reaction to obtain a first reaction liquid; step S3, passing the first reaction liquid through a final flash evaporation pump of the first multi-stage flash evaporation to obtain a second residual liquid; step S4, adding a second water treatment agent to the second residual liquid for reaction to obtain a second reaction liquid; step S5, the second reaction liquid is sequentially subjected to a second flash evaporation and enters a clarification tank for sedimentation treatment to obtain an upper clear liquid and a precipitate; the first water treatment agent is an inorganic coagulant, and the second water treatment agent is an organic polymer flocculant.

[0008] Furthermore, the pH value of the first residual liquid is 6.5-9.0.

[0009] Furthermore, the first residual liquid includes solid suspended matter, metal ions and silicon dioxide, and in terms of weight percentage, the content of solid suspended matter is 10000 mg / L to 50000 mg / L, the content of metal ions is 1000 mg / L to 3000 mg / L, and the content of silicon dioxide is 200 mg / L to 400 mg / L; preferably, the metal ions are calcium ions and / or magnesium ions.

[0010] Furthermore, the first water treatment agent is selected from one or more of sodium aluminate, polyaluminum chloride, modified polyaluminum chloride, polyferric sulfate, polyferric chloride, polyferric sulfate, polyaluminum ferric chloride, potassium sodium hydroxide, ferrous sulfate, aluminum sulfate and potassium sodium carbonate, and the first water treatment agent is added in the form of an aqueous solution. Preferably, in the aqueous solution, the mass concentration of the first water treatment agent is 4% to 52%.

[0011] Furthermore, the dosage of the first water treatment agent is 1 mg / L to 150 mg / L.

[0012] Furthermore, the second water treatment agent is polyacrylamide, and the relative molecular mass of polyacrylamide is (0.66-2.1)×10 7 .

[0013] Furthermore, polyacrylamide is added in the form of a polyacrylamide solution, and the mass concentration of the polyacrylamide solution is 1‰ to 10‰.

[0014] Furthermore, the dosage of the second water treatment agent is 1 mg / L to 15 mg / L.

[0015] Furthermore, the dosage ratio of the first water treatment agent to the second water treatment agent is (2.5-70):1; preferably (40-70):1.

[0016] Furthermore, the flow rate of the final flash pump is 200m 3 / h~500m 3 / h, and the pressure is 0.4MPa-1MPa; preferably, the multi-stage flash evaporation is a three-stage flash evaporation, and the third stage flash evaporation is a vacuum flash evaporation.

[0017] By applying the technical solution of the present invention, inorganic coagulants and organic polymer flocculants are added as needed at different stages of the coal gasification black water treatment process, and the synergistic effect between the two is utilized to significantly improve the treatment effect of coal gasification black water. The treatment method provided by the present invention can reduce the turbidity of coal gasification black water and reduce the solid suspended matter therein, while also having certain hardness and silicon removal performance, which can effectively improve the water quality of gasification circulating gray water and greatly improve the operability and stability of industrial production. DETAILED DESCRIPTION

[0018] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0019] As described in the background art, the existing technology for treating coal gasification black water has the problem of poor treatment effect. Specifically, in order to achieve good and standard treatment effect, the black water treatment agents in the existing technology often have complicated preparation processes and complex ingredients, and are still not well adapted to the water quality of coal gasification black water. At the same time, the addition method during the application process is single, and the final effect on removing silicon content and reducing hardness of black water is also poor. In order to solve the above technical problems, the present invention provides a method for treating coal gasification black water, which comprises: step S1, performing a first multi-stage flash evaporation on the coal gasification black water, and obtaining a first flash gas and a first residual liquid after cooling; step S2, adding a first water treatment agent to the first residual liquid for reaction to obtain a first reaction liquid; step S3, passing the first reaction liquid through a final flash evaporation pump of the first multi-stage flash evaporation to obtain a second residual liquid; step S4, adding a second water treatment agent to the second residual liquid for reaction to obtain a second reaction liquid; step S5, the second reaction liquid is sequentially subjected to a second flash evaporation and enters a clarification tank for sedimentation treatment to obtain an upper clear liquid and a precipitate; the first water treatment agent is an inorganic coagulant, and the second water treatment agent is an organic polymer flocculant.

[0020] The above-mentioned coal gasification black water treatment method provided by the present invention adds inorganic coagulants and organic polymer flocculants at different stages of the process respectively, and utilizes the synergistic effect between the two to significantly improve the treatment effect of coal gasification black water. Specifically, the inorganic coagulant is added between the final flash evaporation step and the corresponding final flash evaporation pump of the multi-stage flash evaporation treatment, and the organic polymer flocculant is added after the final flash evaporation pump and before entering the clarification tank for sedimentation treatment. In this process, the inorganic coagulant added upstream can first neutralize the charge of the suspended particles in the coal gasification black water to destabilize the colloidal particles and form a first reaction liquid. After passing through the final flash evaporation pump, the concentration of the obtained first residual liquid becomes larger, and the temperature and pressure become more stable. In this state, the addition of the organic polymer coagulant can effectively generate a bridging effect between the destabilized suspended particles, and generate a sweeping effect in the destabilization process to generate settleable flocs, which ultimately significantly improves the purification treatment effect of coal gasification black water. The above-mentioned inorganic coagulants and organic polymer flocculants complement each other in terms of chemical composition, structure, properties and functions. Adding the two into the process flow of coal gasification black water treatment in the above-mentioned order and timing in stages ensures that the two can have an effective synergistic effect, thereby efficiently promoting the flocculation and sedimentation of suspended matter in coal gasification black water and improving the water quality of gasification circulating ash water. At the same time, the above-mentioned coal gasification black water treatment method provided by the present invention has a certain hardness and silicon removal performance in addition to its excellent suspension turbidity reduction effect, and has strong water quality adaptability; and the method is simple to operate, which can reduce the difficulty of gasification black water regeneration in large-scale industrial production and improve the operability and stability of industrial production.

[0021] It should also be emphasized that the above-mentioned coal gasification black water treatment method provided by the present invention, based on the coordinated use of inorganic coagulants and organic polymer flocculants, more importantly, designs and optimizes the timing and order of adding the two respectively, so as to effectively realize the synergistic effect as described above and achieve the technical effects of reducing turbidity, reducing solid suspended matter and reducing hardness.

[0022] In several typical implementations, the pH value of the first residual liquid is 6.5 to 9.0. The method for treating coal gasification black water provided by the present invention obtains a first residual liquid with a specific pH value after multi-stage flash evaporation, so that it can react with the first water treatment agent, i.e., the inorganic coagulant, to effectively remove suspended particles therein.

[0023] Furthermore, the first residual liquid includes solid suspended matter, metal ions and silicon dioxide, and the content of solid suspended matter is 10000mg / L to 50000mg / L, and the content of metal ions is 1000mg / L to 3000mg / L by weight percentage. Among them, the solid suspended matter mainly includes carbon black, and compounds of elements such as silicon, aluminum, iron, magnesium, and oxygen. The treatment method provided by the present invention can obtain better treatment effect when it is aimed at coal gasification black water with the above impurities. And, the above-mentioned treatment method provided by the present invention can produce better removal and separation effect on silicon dioxide, and preferably the content of silicon dioxide is 200mg / L to 400mg / L. Preferably, the metal ions are calcium ions and / or magnesium ions.

[0024] It should be noted that part of the silica content in the residual liquid is suspended colloidal particles and part is soluble silicate ions (such as SiO(OH)2 - ).

[0025] As for the type of inorganic coagulant used in the first water treatment agent, in several typical embodiments, it is preferably selected from one or more of sodium aluminate, polyaluminium chloride, modified polyaluminium chloride, polyferric sulfate, polyferric chloride, polyaluminium ferric hydroxide, ferrous sulfate, aluminium sulfate and potassium sodium carbonate, and the first water treatment agent is added in the form of an aqueous solution; in the aqueous solution, the mass concentration of the first water treatment agent is 4% to 52%. Although the inorganic coagulants commonly used in the art can be tried as treatment agents for coal gasification black water, the inventor has selected the above-mentioned specific types through a large number of experiments, and allowed them to enter the treatment system in the form of 4 to 52% aqueous solution, because within this concentration range, the above-mentioned inorganic coagulants can better neutralize the charge of suspended particles and destabilize the obtained colloidal particles, thereby improving the removal effect of suspended particles, and at the same time, to a greater extent, improve the compatibility with subsequent organic polymer flocculants, and weaken the negative impact on the environment, thereby comprehensively improving the treatment effect.

[0026] Furthermore, in order to enhance the destabilization effect of the solid suspended particles and to coordinately consider the coupling effect with the subsequent organic polymer flocculant, the dosage of the first water treatment agent is preferably 1 mg / L to 150 mg / L.

[0027] In several typical embodiments, the second water treatment agent is polyacrylamide, and the relative molecular mass of polyacrylamide is (0.66-2.1)×10 7. The inventors have optimized the relative molecular weight of the organic polymer flocculant, i.e., polyacrylamide, according to the type and dosage of the above-mentioned inorganic coagulant, through a large number of experiments, and found that the polyacrylamide flocculant with the above-mentioned relative molecular weight can more effectively react with the colloidal particle system including the inorganic coagulant and the suspended matter in the black water to form a more stable flocculent body, thereby improving the flocculation effect. On this basis, in order to achieve a more significant purification treatment effect, the inventors have further optimized the addition of polyacrylamide in the form of a polyacrylamide solution through a large number of experiments, and the mass concentration of the polyacrylamide solution is 1‰ to 10‰.

[0028] In application, polyacrylamide can be selected from one or more of the non-ionic, anionic and cationic types, all of which can achieve good synergistic effects with inorganic coagulants.

[0029] Furthermore, in order to better cooperate with the inorganic coagulant, that is, to react more effectively with the colloidal particles formed between the inorganic coagulant and the solid suspended matter, and to make the formed floccules in a more suitable size, thereby effectively improving the flocculation effect, the preferred dosage of the second water treatment agent is 1 mg / L to 15 mg / L.

[0030] In several typical implementations, in order to make the synergistic coupling effect between the inorganic coagulant and the organic polymer flocculant more significant, thereby effectively improving the final technical effects of reducing turbidity, reducing solid suspended matter and reducing hardness, the inventors have preferred the dosage ratio of the first water treatment agent to the second water treatment agent to be (2.5-70): 1 after a large number of experiments. On the basis of the above, the dosage ratio of the first water treatment agent to the second water treatment agent is more preferably (40-70): 1, and under this dosage relationship, a higher SiO2 and calcium and magnesium ion removal rate is obtained, which significantly optimizes the water quality of the coal gasification black water after treatment.

[0031] In several more typical embodiments, the first water treatment agent is a combination of potassium sodium carbonate and sodium aluminate, and the weight ratio of potassium sodium carbonate to sodium aluminate is 1: (1-1.5). The inventors have conducted a large number of experiments and synergistically optimized the types of inorganic coagulants used to obtain the above scheme. The first water treatment agent provided by the scheme can better remove hardness and silicon dioxide, and the supernatant obtained after treatment has lower turbidity, higher removal rates of suspended solids, SiO2 and calcium and magnesium ions, and more significant treatment effect.

[0032] Also, to avoid ambiguity, the "sodium aluminate alkaline solution" involved in the present invention is an aqueous solution of sodium aluminate, but because sodium aluminate will undergo hydrolysis reaction with water in an aqueous solution to form a strong alkaline, it is called sodium aluminate alkaline solution.

[0033] Furthermore, in order to cooperate with the synergistic effect between the above two treatment agents and achieve better treatment effect, the inventor adjusted the parameter setting of the final flash pump through a large number of experiments, and preferably set its flow rate to 200m 3 / h~500m 3 / h, and the pressure is 0.4MPa-1MPa. In order to further reduce turbidity and realize continuous operation and improve the treatment effect, in several typical implementations, it is preferred that the multi-stage flash evaporation is a three-stage flash evaporation, and the third-stage flash evaporation is a vacuum flash evaporation, so that the residual liquid to be treated at each stage can be better adapted to its corresponding treatment agent, and finally a more significant treatment effect is obtained.

[0034] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0035] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0036] It should be noted in advance that the coal gasification black water treated in the present invention comes from the high-temperature, high-pressure, high-suspended black water produced by the quenching chamber of the gasifier of the entrained-bed gasification device and the synthesis gas washing system. The water quality indicators and hydraulic environment are shown in the following table:

[0037] Water quality indicators and hydraulic environment of black water index Temperature / ℃ 240 Pressure / MPa 5 pH 7.5 Suspended solids / mg / L <![CDATA[1.5×10 4 ]]> Silicon content / mg / L 394 Hardness / mg / L 1260 Ammonia nitrogen / mg / L 221 COD / mg / L 700

[0038] Example 1

[0039] A method for treating coal gasification black water:

[0040] The coal gasification black water having the component contents in the above table is subjected to three-stage flash evaporation, wherein the pressure of the first stage flash evaporation is 0.7±0.1MPa, the pressure of the second stage flash evaporation is 0.4±0.1MPa, and the third stage flash evaporation is vacuum flash evaporation, to obtain the first flash gas and the first residual liquid, the pH of the first residual liquid is 7.5, and the main components thereof are shown in the following table:

[0041] Water quality indicators Solid particles silicon Calcium and magnesium ions Ammonia nitrogen compounds COD Content (mg / L) 12500 360 1105 205 603

[0042] Before the first residual liquid passes through the final flash pump of the first flash treatment, a liquid sodium aluminate alkaline solution with a mass concentration of 52% and an addition amount of 60 mg / L is added to carry out a first reaction to obtain a first reaction liquid.

[0043] The first reaction liquid has a flow rate of 330 m 3 / h, and a final flash pump with a pressure of 0.6 MPa to obtain a second residual liquid.

[0044] Before the subsequent flash evaporation and sedimentation operations, the obtained second residual liquid was added with a polyacrylamide solution with a concentration of 1‰, wherein the relative molecular mass of polyacrylamide was 1.6×10 7 , the dosage is 1.5 mg / L, and a second reaction is carried out to obtain a second reaction liquid.

[0045] The second reaction liquid turbulently enters the clarification tank for sedimentation treatment to obtain supernatant liquid and precipitate, thus completing the treatment process.

[0046] The dosage ratio of the first water treatment agent to the second water treatment agent is 40:1.

[0047] Example 2

[0048] A method for treating coal gasification black water:

[0049] The difference between this embodiment and embodiment 1 is that the first water treatment agent, the second water treatment agent and the corresponding dosage are different. Specifically, the first water treatment agent is a 15% polyaluminium chloride (PAC) solution with a dosage of 50 mg / L, and the second water treatment agent is a 10‰ polyacrylamide solution, wherein the relative molecular mass of polyacrylamide is 1.6×10 7 , the dosage is 2mg / L.

[0050] The dosage ratio of the first water treatment agent to the second water treatment agent is 25:1.

[0051] Example 3

[0052] A method for treating coal gasification black water:

[0053] The difference between this embodiment and embodiment 1 is that the first water treatment agent, the second water treatment agent and the corresponding dosage are different. Specifically, the first water treatment agent is a 4% modified polyaluminium chloride (MPAC) solution with a dosage of 5 mg / L, and the second water treatment agent is a 1‰ polyacrylamide solution, wherein the relative molecular mass of polyacrylamide is 1.6×10 7 , dosage 2mg / L.

[0054] The dosage ratio of the first water treatment agent to the second water treatment agent is 2.5:1.

[0055] Example 4

[0056] A method for treating coal gasification black water:

[0057] The difference between this embodiment and embodiment 1 is that the first water treatment agent, the second water treatment agent and the corresponding dosage are different. Specifically, the first water treatment agent is a 35% polyferric sulfate (PFS) solution with a dosage of 65 mg / L, and the second water treatment agent is a 1‰ polyacrylamide solution, wherein the relative molecular mass of polyacrylamide is 1.6×10 7 , dosage 2mg / L.

[0058] The dosage ratio of the first water treatment agent to the second water treatment agent is 32.5:1.

[0059] Example 5

[0060] A method for treating coal gasification black water:

[0061] The difference between this embodiment and embodiment 1 is that the first water treatment agent, the second water treatment agent and the corresponding dosage are different. Specifically, the first water treatment agent is a mixed solution of 35% potassium sodium carbonate and sodium aluminate (the weight ratio of potassium sodium carbonate to sodium aluminate is 3:4), the dosage is 140 mg / L, and the second water treatment agent is a 1‰ polyacrylamide solution, wherein the relative molecular mass of polyacrylamide is 1.6×10 7 , dosage 2mg / L.

[0062] The dosage ratio of the first water treatment agent to the second water treatment agent is 70:1.

[0063] Example 6

[0064] A method for treating coal gasification black water:

[0065] The difference between this embodiment and embodiment 1 is that the first water treatment agent, the second water treatment agent and the corresponding dosage are different. Specifically, the first water treatment agent is a 10% polyaluminium ferric chloride (PAFC) solution with a dosage of 40 mg / L, and the second water treatment agent is a 1‰ polyacrylamide solution, wherein the relative molecular mass of polyacrylamide is 2.1×10 7 , dosage 2mg / L.

[0066] The dosage ratio of the first water treatment agent to the second water treatment agent is 20:1.

[0067] Example 7

[0068] A method for treating coal gasification black water:

[0069] The difference between this embodiment and embodiment 1 is that the first water treatment agent, the second water treatment agent and the corresponding dosage are different. Specifically, the first water treatment agent is a 10% polyaluminium ferric chloride (PAFC) solution with a dosage of 40 mg / L, and the second water treatment agent is a 1‰ polyacrylamide solution, wherein the relative molecular mass of polyacrylamide is 1.1×10 7 , dosage 5mg / L.

[0070] The dosage ratio of the first water treatment agent to the second water treatment agent is 8:1.

[0071] Example 8

[0072] A method for treating coal gasification black water:

[0073] The only difference between this embodiment and embodiment 1 is that the coal gasification black water raw material is changed so that the pH of the first residual liquid is 4.5.

[0074] Example 9

[0075] A method for treating coal gasification black water:

[0076] The difference between this embodiment and embodiment 1 is that the first water treatment agent and the second water treatment agent used are different. Specifically, the concentration of the sodium metaaluminate alkaline solution of the first water treatment agent is 2%, and the concentration of the polyacrylamide solution used as the second water treatment agent is 15‰, wherein the relative molecular mass of the polyacrylamide is 0.5×10 7 .

[0077] Example 10

[0078] A method for treating coal gasification black water:

[0079] The difference between this embodiment and embodiment 1 is that the first water treatment agent and the second water treatment agent used are different. Specifically, the concentration of the sodium metaaluminate alkaline solution of the first water treatment agent is 55%, and the concentration of the polyacrylamide solution used as the second water treatment agent is 0.8‰, wherein the relative molecular mass of the polyacrylamide is 2.4×10 7 .

[0080] In this embodiment, because the mass concentration of the sodium aluminate alkaline solution rises to 55%, which is higher than the mass concentration range of 4 to 52% preferred by the present invention, trace precipitation may be generated during the application process, resulting in slight instability and deterioration, and ultimately a slight decrease in the treatment effect.

[0081] Embodiment 11

[0082] A method for treating coal gasification black water:

[0083] The only difference between this embodiment and embodiment 1 is that the dosage of the first water treatment agent and the second water treatment agent used is different. Specifically, the dosage of the first water treatment agent is 0.8 mg / L, and the dosage of the second water treatment agent is 0.4 mg / L, and the ratio between the two is 2:1.

[0084] Example 12

[0085] A method for treating coal gasification black water:

[0086] The only difference between this embodiment and embodiment 1 is that the dosage of the first water treatment agent and the second water treatment agent used is different. Specifically, the dosage of the first water treatment agent is 160 mg / L, and the dosage of the second water treatment agent is 2 mg / L, and the ratio between the two is 80:1.

[0087] Comparative Example 1

[0088] A method for treating coal gasification black water:

[0089] The only difference between this comparative example and Example 1 is that the first water treatment agent is not added.

[0090] Comparative Example 2

[0091] A method for treating coal gasification black water:

[0092] The only difference between this comparative example and Example 1 is that no second water treatment agent is added.

[0093] Comparative Example 3

[0094] A method for treating coal gasification black water:

[0095] The coal gasification black water is subjected to the conditions in Example 1 to obtain a first flash gas and a first residual liquid.

[0096] Before the first residual liquid passes through the final flash pump, a 52% mass concentration of liquid sodium aluminate alkaline solution and a 1‰ concentration of polyacrylamide solution (wherein the relative molecular mass of polyacrylamide is 1.6×10 7 ), and the dosage of sodium aluminate alkaline solution is 60 mg / L, and the dosage of polyacrylamide solution is 1.5 mg / L, and a first reaction is carried out to obtain a first reaction solution.

[0097] The first reaction liquid is passed through the final flash pump and then subjected to sedimentation treatment under the conditions of Example 1 to obtain a supernatant and a precipitate, thus completing the treatment process.

[0098] That is, the only difference between this comparative example and Example 1 is that the first water treatment agent and the second water treatment agent are added simultaneously.

[0099] Comparative Example 4

[0100] A method for treating coal gasification black water:

[0101] The coal gasification black water is subjected to the conditions in Example 1 to obtain a first flash gas and a first residual liquid.

[0102] Before the first residual liquid passes through the final flash pump, a polyacrylamide solution with a concentration of 1‰ is added, wherein the relative molecular mass of polyacrylamide is 1.6×10 7 , the dosage is 1.5 mg / L, a first reaction is carried out to obtain a first reaction liquid.

[0103] The first reaction liquid is passed through a final flash pump under the conditions in Example 1 to obtain a second residual liquid.

[0104] Before the subsequent operation, the obtained second residual liquid was added with a 52% sodium aluminate alkaline solution in an amount of 60 mg / L to carry out a second reaction to obtain a second reaction liquid.

[0105] The second reaction liquid is further subjected to sedimentation treatment under the conditions of Example 1 to obtain a supernatant and a precipitate, thus completing the treatment process.

[0106] That is, the difference between this comparative example and Example 1 is that the order of adding the first water treatment agent and the second water treatment agent is exchanged.

[0107] The supernatants obtained after sedimentation of the above-mentioned embodiments and comparative examples were tested and analyzed to obtain the treatment results shown in Table 1.

[0108] Table 1

[0109]

[0110]

[0111] From the above description, it can be seen that the above-mentioned embodiments of the present invention achieve effective treatment of coal gasification black water. The turbidity of the treated coal gasification black water is significantly reduced to <10. At the same time, the removal rate of total suspended solids, especially silicon dioxide, is significantly increased. At the same time, the calcium and magnesium ions in the black water solution are also effectively removed, and the hardness of the solution is significantly reduced.

[0112] Specifically, the correct selection and appropriate dosage of the first water treatment agent determine the final effect of black water softening and silicon removal. The aluminum-containing reagent is easily hydrolyzed to generate colloidal aluminum hydroxide to adsorb and destabilize silica gel particles, thus having a good silicon removal effect. The alkaline solution can neutralize the temporary bicarbonate in the water to generate calcium carbonate precipitation to achieve the purpose of hardness removal. Compared with Examples 1 and 5, Examples 2, 3, 4, 6, 7, and 8 only have a more significant silicon removal effect. Examples 9, 10, and 11 all have a reduced silicon removal effect due to improper selection of agents or improper dosage, and Example 12 causes a waste of agents; The correct selection and appropriate dosage of the second water treatment agent determine the removal effect of turbidity and suspended matter after black water treatment. Examples 1, 2, 3, 4, 5, 6, and 7 have achieved good turbidity reduction and suspended matter removal effects. The acidic water quality of Example 8 causes the agent to have a poor turbidity reduction and suspended matter removal effect. Examples 9, 10, 11, and 12 have unsatisfactory turbidity reduction and suspended matter removal effects due to improper selection of agents or improper dosage. Comparative Examples 1 to 4 illustrate that the coordinated use of the first water treatment agent and the second water treatment agent, as well as the specific order of their addition, are the most important factors in improving the treatment effect.

[0113] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0114] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for treating coal gasification black water, characterized in that: The processing method comprises: Step S1, performing multi-stage flash evaporation on the coal gasification black water to obtain a first residual liquid; Step S2, adding a first water treatment agent to the first residual liquid for reaction to obtain a first reaction liquid; Step S3, passing the first reaction liquid through the final flash pump of the multi-stage flash evaporation to obtain a second residual liquid; Step S4, adding a second water treatment agent to the second residual liquid for reaction to obtain a second reaction liquid; Step S5, the second reaction liquid enters a clarification tank for sedimentation treatment to obtain a supernatant and a precipitate; The first water treatment agent is an inorganic coagulant, and the second water treatment agent is an organic polymer flocculant.

2. The processing method according to claim 1, characterized in that: The pH value of the first residual liquid is 6.5-9.

0.

3. The processing method according to claim 1 or 2, characterized in that: The first residual liquid includes solid suspended matter, metal ions and silicon dioxide, and in terms of weight percentage, the content of the solid suspended matter is 10000 mg / L to 50000 mg / L, the content of the metal ions is 1000 mg / L to 3000 mg / L, and the content of the silicon dioxide is 200 mg / L to 400 mg / L; Preferably, the metal ions are calcium ions and / or magnesium ions.

4. The processing method according to any one of claims 1 to 3, characterized in that: The first water treatment agent is selected from one or more of sodium aluminate, polyaluminium chloride, modified polyaluminium chloride, polyferric sulfate, polyferric chloride, polyferric chloride sulfate, polyaluminium ferric chloride, potassium sodium hydroxide, ferrous sulfate, aluminium sulfate and potassium sodium carbonate, and the first water treatment agent is added in the form of an aqueous solution; Preferably, in the aqueous solution, the mass concentration of the first water treatment agent is 4% to 52%.

5. The processing method according to claim 4, characterized in that: The dosage of the first water treatment agent is 1 mg / L to 150 mg / L.

6. The processing method according to any one of claims 1 to 5, characterized in that: The second water treatment agent is polyacrylamide, and the relative molecular mass of the polyacrylamide is (0.66-2.1)×10 7 .

7. The processing method according to claim 6, characterized in that: The polyacrylamide is added in the form of a polyacrylamide solution, and the mass concentration of the polyacrylamide solution is 1‰ to 10‰.

8. The processing method according to claim 6 or 7, characterized in that: The dosage of the second water treatment agent is 1 mg / L to 15 mg / L.

9. The processing method according to any one of claims 1 to 8, characterized in that: The dosage ratio of the first water treatment agent to the second water treatment agent is (2.5-70):1, preferably (40-70):

1.

10. The processing method according to any one of claims 1 to 9, characterized in that: The flow rate of the final flash pump is 200m 3 / h~500m 3 / h, pressure is 0.4MPa~1MPa; Preferably, the multi-stage flash evaporation is a three-stage flash evaporation, and the third stage flash evaporation is a vacuum flash evaporation.

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