Filter aid for activated sludge dehydration and modifier thereof and preparation method based on coal gasification coal sludge

Abstract

The present invention relates to the field of waste resource utilization and specifically discloses a filter aid modifier for activated sludge dewatering, comprising anionic polyacrylamide, a compound of Formula 1, and a compound of Formula 2. The present invention also provides a filter aid comprising the modifier and coal gasification sludge reselection material, and its use in activated sludge dewatering. The modifier and filter aid described herein can improve the dewatering performance of activated sludge based on their synergistic composition.

Description

Technical Field

[0001] The invention belongs to the technical field of resource utilization of coal chemical waste products, and particularly relates to a method for preparing an activated sludge dehydration filter aid from coal gasification coal sludge. Background Art

[0002] Activated sludge is a byproduct of biological wastewater treatment in municipal wastewater treatment plants. It contains large quantities of bacteria, viruses, and organic matter, as well as heavy metals such as cadmium, chromium, copper, zinc, and lead, and toxic and hazardous substances such as polychlorinated biphenyls (PCBs). It also has a high water content, reaching up to 99%. In recent years, with the rapid construction of wastewater treatment plants, the amount of sludge generated has also increased annually, making its treatment and disposal increasingly problematic. Domestic sludge disposal methods primarily include landfill, land use, and incineration. However, these conventional sludge disposal methods no longer meet environmental protection requirements.

[0003] In recent years, researchers both domestically and internationally have shifted their research focus to new technologies for sludge treatment and disposal that are environmentally friendly and highly resource-efficient. Dewatering and volume reduction are crucial for sludge transportation, treatment, and disposal. Currently, many sewage treatment plants utilize iron salts, aluminum salts, and polymer flocculants to coagulate and condition sludge, reducing clogging of filter media and mud crusts and improving sludge dewatering performance. However, during mechanical dewatering, sludge pellets conditioned by single flocculation methods easily deform under pressure, leading to a decrease in filtration efficiency as pores in the mud crust close and disappear. Filter aids are often used to reduce the compressibility of the mud cake and improve mechanical dewatering efficiency. Compared to flocculants, filter aids are less expensive and significantly increase sludge dewatering speed, leading to increased interest in efficient and cost-effective filter aids. Common filter aids include carbon-based materials such as coke, pulverized coal, and biomass, and mineral materials such as cement, fly ash, and gypsum. Mineral materials are easier to obtain and less expensive than carbon-based materials. Carbon-based materials can also increase the organic matter content and calorific value of sludge while promoting dehydration. Therefore, if sludge is ultimately disposed of by landfill, mineral materials are more appropriate, while if composting or incineration is used, carbon-based materials are more appropriate.

[0004] Coal gasification is an effective way to utilize coal cleanly and efficiently at this stage, but the current poor performance or operation level of gasifier equipment will lead to the production of a large amount of gasification coarse slag and gasification fine slag. Coal gasification fine slag (coal gasification coal slime) is a solid waste residue that is discharged with the flue gas in the form of fly ash in the coal gasifier and separated by the slag removal process. The fine slag is generally gray-black powder, and the mass proportion of particles with a size between 50 and 200 μm is about 72%. The shape is generally spherical particles and irregular honeycomb-shaped particles. The surface is severely oxidized, and the specific surface area can reach 258.29 m 2 / g, with large roughness. Its composition is related to the type of coal, production process and operating conditions, and mainly depends on the inorganic and organic components in the coal. Among them, the inorganic components are mainly composed of calcium iron aluminum silicate and mineral melt. Since it contains more alkali metal oxides, the pH value of coal gasification fine slag is mostly alkaline; the organic components are mainly unburned residual carbon and are dispersed in the inorganic components. Its combustion characteristics are similar to those of inferior bituminous coal. The composition of gasification coarse slag is similar to that of boiler ash, and it can be used as a blending raw material for building materials, roads and bridges; however, gasification fine slag cannot be directly used as construction and road materials due to its high carbon content and large ignition loss. Landfill treatment is currently the main treatment method. This method not only wastes land, but also the leakage of leachate containing heavy metals will cause soil and water pollution. Secondly, the residual carbon cannot be recovered, so the economic and environmental performance is extremely poor. The economic, environmental and efficient treatment of gasification fine slag is an important issue that coal gasification enterprises need to solve. At present, research on the application of gasification slag at home and abroad mainly focuses on the following aspects:

[0005] ① Using fumed slag for the production of construction materials, such as aggregates, cementitious materials, wall materials, and unfired bricks. This is an important approach to the large-scale utilization of coal gasification slag. Fumed slag contains a large amount of silicon and aluminum oxides and exhibits a certain pozzolanic activity, making it a useful cement raw material. Due to the well-defined gradation of coal gasification slag particles, it can be used as an aggregate and admixture in concrete production. Researchers have found that the compressive strength of concrete incorporating ground fumed coarse slag is significantly higher than that of baseline concrete, and this strength continues to increase with aging. This suggests that ground fumed coarse slag could be used to partially replace natural sand as fine aggregate in concrete. Using the residual carbon in fumed slag as a pore-forming agent and internal fuel can reduce the density and thermal conductivity of sintered products, enabling the production of thermally insulating, low-density wall materials. By adding water, calcium oxide, and sodium sulfate to coal gangue, steel slag, fumed slag, and boiler slag in a specific mass ratio, unfired bricks with a strength three times that of ordinary bricks can be produced. ② Use gasification slag for the preparation of high value-added materials, such as catalyst carriers, rubber and plastic fillers, ceramic materials, silicon-based materials, etc. Coal gasification slag contains rich aluminum, silicon and carbon resources, so it can be used to prepare inorganic materials with high added value. For example, by using coal gasification slag and alkaline medium low-temperature solid phase activation and dilute acid leaching to obtain a solution rich in aluminum and silicon, and adding appropriate templates, a specific surface area of ​​up to 1200m 2 / g of silica mesoporous material. Porous ceramics can be prepared by using coal gasification slag, kaolin, and calcium carbonate in a ratio of 11:5:4, under a molding pressure of 10MPa and a calcination temperature of 1180°C. Using a compression molding process, porous ceramics with a porosity of 49.20% and an average pore size of 5.96nm can be prepared. ③ Recycling the residual carbon in the gasification slag. The high residual carbon content, low calorific value, and high moisture content of coal gasification slag result in a low direct blending ratio. Co-firing requires the addition of auxiliary equipment, thereby increasing operating costs. The high ignition loss of coal gasification slag is one of the reasons why it is difficult to utilize. Recycling the high-carbon gasification slag not only utilizes the carbon resources in it, but also converts the high-carbon slag into low-carbon slag, which is conducive to the utilization of gasification slag as building materials. The existing scheme for improving the quality of residual carbon by flotation still mainly starts with the selection of flotation reagents, finding suitable reagents and flotation processes. However, the problem of reagent waste caused by the loose and porous characteristics of the gasification fine slag itself has not been substantially solved, making it impossible for the flotation technology of gasification fine slag to better serve the chemical industry, that is, its economic efficiency remains to be verified. ④ Gasification slag is used for soil and water remediation. Applying gasification slag to soil and water remediation is one of the important ways to utilize gasification slag resources, which is in line with the environmental protection concept of treating waste with waste. At present, many scholars have tried to use gasification slag as soil conditioner, sludge conditioner, water treatment adsorbent, etc. Gasification slag is rich in aluminum, silicon, and carbon resources. It is an excellent raw material for preparing silicon adsorbents, carbon adsorbents, carbon-silicon composite materials, and water treatment agents such as polyaluminum chloride. Summary of the Invention

[0006] In response to the problem of unsatisfactory activated sludge dewatering effect, the present invention aims to provide a filter aid and modifier for activated sludge dewatering, aiming to improve the dewatering and modification effects of activated sludge based on the combined synergy of the components.

[0007] The second object of the present invention is to provide an activated sludge dehydration filter aid, aiming to provide a filter aid derived from coal gasification coal slime and having high activated sludge dehydration performance.

[0008] The third object of the present invention is to provide a method for preparing the activated sludge dehydration filter aid of the present invention using coal gasification coal slime, aiming to prepare a filter aid with excellent activated sludge dehydration ability based on the resource utilization of industrial coal gasification coal slime waste.

[0009] The fourth object of the present invention is to provide a method for dewatering activated sludge using the filter aid.

[0010] A filter aid modifier for dehydrating activated sludge, comprising anionic polyacrylamide, a compound of formula 1, and a compound of formula 2;

[0011]

[0012] Formula 1

[0013]

[0014] Formula 2

[0015] In Formula 1, R1 and R2 are independently H, C1-C6 alkyl, C1-C6 alkoxy, halogen, trifluoromethyl or nitro; M is H, Na, K or NH4;

[0016] The R3 is a C2-C8 alkyl group, a methylene group with a substituent, a phenyl group or a phenyl group with a substituent; the substituent is a hydroxyl group, a C1-C6 alkoxy group, a halogen group, a nitro group or a trifluoromethyl group.

[0017] The present invention has found that the innovative use of anionic polyacrylamide in combination with Formula 1 and Formula 2 can achieve synergy and can synergistically improve the dewatering capacity of activated sludge.

[0018] The molecular weight of the anionic polyacrylamide can be 1.0×10 5 ~2×10 8 ; further can be 1.2×10 7 ~1.6×10 7 .

[0019] In the present invention, considering the processing efficiency, effect and cost, the formula 1 is preferably a compound of formula 1-A, which is a compound in formula 1, wherein R1 and R2 are both H and M is Na.

[0020] Preferably, in Formula 2, R3 is a phenyl group or a phenyl group with a substituent, and the substituent is a hydroxyl group, a C1-C3 alkyl group, or a C1-C3 alkoxy group;

[0021] In the present invention, further controlling the ratio of the modifier components helps further improve the synergistic effect of the components in improving activated sludge dewatering. Preferably, the weight ratio of anionic polyacrylamide, Formula 1, and Formula 2 is 0.05-5:0.5-10:0.2-3; more preferably, 0.1-0.5:1-5:1-2; and even more preferably, 0.2-0.4:2-4:1-2. Research in the present invention has found that at this preferred weight ratio, further synergistic improvements in activated sludge dewatering performance are achieved.

[0022] The present invention also provides an activated sludge dehydration filter aid, comprising a re-selected material of coal gasification coal sludge and the filter aid modifier;

[0023] The re-selected material is the remaining material after the heavy components are removed from the coal gasification slime through re-selection.

[0024] The present invention innovatively discovered that, based on the aforementioned collaborative innovation of filter aids and modifiers, the combination of gasification coal slime re-selection materials can further improve the synergy of components, further enhance the dehydration of activated sludge, and improve the calorific value of the sludge. Furthermore, it can achieve the effective disposal of gasification coal slime and realize resource utilization.

[0025] In the present invention, the re-selected material can be realized based on known re-selection equipment. Preferably, the re-selected material is coal gasification slime with a density greater than 2.4 g / m 3 The remaining material of the heavy component.

[0026] In the present invention, the ratio of the reselected material and the modifier in the activated sludge dewatering filter aid helps to further improve the performance of the components in activated sludge dewatering. Preferably, the weight content of the filter aid modifier in the activated sludge dewatering filter aid is 0.5-20%, preferably 2-10%, and further preferably 2.5-5% considering the processing cost.

[0027] The present invention also provides a method for preparing the activated sludge dehydration filter aid using coal gasification coal slime, wherein the coal gasification coal slime is subjected to gravity separation to reduce the heavy components therein to obtain gravity separation material; the gravity separation material is compounded with the filter aid modifier to obtain the filter aid.

[0028] In the present invention, the reselection process can be implemented based on existing means.

[0029] In a specific solution of the present invention, the gravity separation material is a single-stage gravity separation material, which comprises the following steps: slurrying the gasified coal to obtain a slurry, gravity separation the slurry, removing 5-40% (preferably 20-35%) of the original weight of heavy components, collecting the light components and medium components therein, and obtaining the single-stage gravity separation material;

[0030] The coal gasification fine slag with a mass ratio of 0.05-0.2 mm accounts for 70-75%;

[0031] Preferably, the slurry mass concentration is 10% to 50%, more preferably 15% to 30%;

[0032] Preferably, the removed heavy components account for 10-40% of the original weight, more preferably 20-30%.

[0033] A more preferred embodiment of the present invention is a two-stage gravity separation material, comprising the following steps: subjecting the single-stage gravity separation material to liquid-phase grinding to obtain a two-stage slurry, followed by a second-stage gravity separation process to further remove heavy components, collect light and medium components, and obtain a two-stage gravity separation material. The present invention has found that combining the two-stage gravity separation with the modifier can further enhance the synergistic effect between the components, helping to further improve the dewatering effect of the activated sludge, and improve the calorific value and utilization value of the sludge.

[0034] Preferably, the mass concentration of the second stage slurry is 10% to 70%, preferably 30% to 55%;

[0035] Preferably, the proportion of -0.075 mm particles in the second stage slurry is not less than 70%, preferably 85% to 95%;

[0036] Preferably, in the second-stage gravity separation material, the total mass of the light components and intermediate components collected is 60-90 wt% of the weight of the first-stage gravity separation material; more preferably, it is 70-80 wt%.

[0037] In the present invention, the reselected material is dried and then mixed evenly with the filter aid modifier in a kneader, and then dried to obtain the filter aid.

[0038] The present invention also provides an application of the filter aid, which is used as a filter aid for dehydrating activated sludge.

[0039] In the present invention, the activated sludge can be any water-containing sludge that requires dehydration. Considering the value of the process, the water content of the activated sludge can be greater than or equal to 70%, further greater than or equal to 80%, and even further greater than or equal to 90%. Most preferably, the activated sludge has a water content greater than or equal to 95%, which is difficult to treat using existing industry technologies.

[0040] In the present invention, the amount of the filter aid can be adjusted according to the dehydration requirements of the activated sludge. Taking into account the treatment efficiency and cost, the amount of the filter aid is greater than or equal to 1 kg / t, preferably 20 to 100 kg / t, more preferably 20 to 60 kg / t, and even more preferably 30 kg / t to 50 kg / t, based on the dry weight of the activated sludge.

[0041] Beneficial effects

[0042] The present invention provides a new modifier comprising anionic polyacrylamide, formula 1 and formula 2, which can improve the dewatering performance of activated sludge based on the combined synergy of the components.

[0043] The present invention combines the aforementioned modifier with the re-selected material from coal gasification sludge to further synergistically improve the dewatering performance of the activated sludge and improve the calorific value and other utilization value of the sludge. Furthermore, the combination of the second-stage re-selected material and the modifier can further enhance the synergistic effect of the components in improving the dewatering of the activated sludge.

[0044] The invention has simple process, low material cost and can realize waste treatment by waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a flow chart of preparing activated sludge filter aid from coal gasification sludge in Example 1. DETAILED DESCRIPTION

[0046] A more specific solution of the present invention comprises the following steps:

[0047] Step 1: Pulping

[0048] The coal gasification slurry is added with water and stirred to obtain the required slurry, wherein the mass concentration of the slurry is 10% to 50%, more preferably 15% to 30%.

[0049] Step 2: Reselect

[0050] The slurry in the first step is subjected to a first-stage gravity separation using a spiral chute. By adjusting the appropriate discharge port ratio, the total mass of the light component and the intermediate component (first-stage gravity separation material) is 60-90wt% of the starting coal gasification coal slime, preferably 70-80wt%.

[0051] Step 3: Fine grinding and reselection

[0052] The light fraction and intermediate fraction obtained in the second step are combined and finely ground, with the slurry concentration controlled at 10% to 70%, preferably 30% to 55%. To achieve a certain dissociation effect, the grinding fineness (the proportion of particles <0.075 mm in the slurry) is not less than 70%, preferably 85% to 95%. The finely ground slurry is then subjected to gravity separation, with the total mass of the light fraction and intermediate fraction (second-stage gravity separation material) controlled to be 60% to 90% by weight of the first-stage gravity separation material, preferably 70% to 80% by weight.

[0053] Step 4: Preparation of activated sludge dewatering filter aid

[0054] The intermediate component obtained by reselection in the third step is combined with the light component and filtered to obtain a filter cake, which is mixed in a kneader together with the modifier and dried to obtain the product. The product is added to the sludge for conditioning, and the dewatering performance of the sludge is evaluated with the sludge specific resistance (SRF) and the mud cake moisture content (MC) as indicators. The modifier contains anionic polyacrylamide, formula 1 and formula 2. The proportion of anionic polyacrylamide in the filter aid is 0.05-5wt%, preferably 0.1-0.5wt%; the proportion of formula 1 in the filter aid is 0.5-10wt%, preferably 1-3wt%; the proportion of formula 2 in the filter aid is 0.2-3wt%, preferably 1-2wt%; the amount of filter aid is 1kg / t-50kg / t (dry sludge), preferably 30kg / t-50kg / t (dry sludge);

[0055] In the present invention, in the following typical cases, the coal gasification slime is a coal gasification slime with an ash content of 35.79% (the mass of the ash content between 0.05 and 0.2 mm accounts for 70-75%) from a coal chemical plant in Yunnan. In the present invention, the heavy tailings discarded by the gravity separation have a density of more than 2.4 g / m 3 ingredients.

[0056] The molecular weight of the anionic polyacrylamide is 1.2×10 7 ~1.6×10 7 .

[0057] In the following cases, Formula 1 is typically represented by Formula 1-A, which is a compound in Formula 1 wherein R1 and R2 are H and M is Na.

[0058] The formula 2 is represented by formula 2-A, which is a compound in formula 2 where R3 is a phenyl group.

[0059] Example 1

[0060] This example uses an activated sludge from Changsha as the experimental material. The sludge has a moisture content of 98.76% to 99.25% and a specific resistance of 150×10 12 m·kg. The specific steps are as follows:

[0061] First, the coal gasification slurry is stirred with water to obtain a slurry with a mass concentration of 30%. It is then re-selected using a spiral chute. By adjusting the appropriate discharge port ratio, the total mass ratio of the light component and the intermediate component (first stage re-selection material) is 70%. This is then finely ground to control the mass concentration of the slurry to 30% and the grinding fineness to 90%. The finely ground slurry is then re-selected to control the total mass ratio of the light component and the intermediate component (second stage re-selection material) to 70wt%. The filter cake is then filtered and mixed with the modifier in a kneader. After drying, the filter aid product is obtained.

[0062] The modifier comprises anionic polyacrylamide (APAM), formula 1-A and formula 2-A, and based on dry weight, the anionic polyacrylamide (APAM) accounts for 0.25wt% in the filter aid; the formula 1-A accounts for 2wt% in the filter aid; and the formula 2-A accounts for 1.5wt% in the filter aid;

[0063] Add an appropriate amount of filter aid to the sludge slurry and stir to mix it evenly. The amount of filter aid is 50kg / t (dry sludge). Then, perform filter pressing and dehydration at 0.6MPa (the filter pressing cycle including feeding, pressure holding, unloading and plate loading takes a total of 40 minutes). The water content, sludge specific resistance and calorific value of the sludge cake are measured.

[0064] The test results are:

[0065]

[0066] Example 2

[0067] Compared with Example 1, the only difference is that the weight content of APAM in the filter aid is changed to: APAM accounts for 0.1, 0.3, and 0.5% respectively. The same method as Example 1 was used to carry out the activated sludge filter press dewatering experiment, and the test results are as follows:

[0068]

[0069] It can be seen from Examples 1 to 2 that good dehydration effects can be obtained at the required APAM content, and further controlling the APAM content at 0.2-0.4%, and further at 0.25-0.3%, can achieve better dehydration effects and better mud cake calorific value.

[0070] Example 3

[0071] Compared with Example 1, the only difference is that the proportions of Formula 1-A are 1, 3, and 5% respectively. The test results are:

[0072]

[0073] Example 4

[0074] Compared with Example 1, the only difference is that the gravity material is a single-stage gravity material, and other operations and parameters are the same as those in Example 1.

[0075] The test results are:

[0076]

[0077] Comparison between Examples 1 and 4 shows that the use of the preferred two-stage gravity separation process is helpful to further improve the combined synergistic effect of the process and the modifier, and can further improve the dehydration efficiency and effect.

[0078] Example 5

[0079] Compared with Example 1, the only difference is that the amount of filter aid added is 30, 40, and 80 kg / t respectively. The test results are:

[0080]

[0081] Comparative Example 1

[0082] Compared with Example 1, the only difference is that the sludge slurry is directly filtered without adding filter aid. The test results are:

[0083]

[0084] Comparative Example 2

[0085] Compared with Example 1, the only difference is that APAM is missing from the filter aid, and its missing weight is supplemented by Formula 1-A.

[0086] The test results are:

[0087]

[0088] Comparative Example 3

[0089] Compared with Example 1, the only difference is that, in the filter aid, nonionic polyacrylamide (HPAM) of equal weight is used to replace APAM, and other operations and parameters are the same as those in Example 1.

[0090] The test results are:

[0091]

[0092] Comparative Example 4

[0093] Compared with Example 1, the only difference is that the filter aid lacks Formula 1-A, and its missing weight is supplemented by APAM.

[0094]

[0095] Comparative Example 5

[0096] Compared with Example 1, the only difference is that an equal weight of sodium hexametaphosphate is used to replace Formula 1-A in the filter aid, and other operations and parameters are the same as those in Example 1.

[0097] The test results are:

[0098]

[0099] Comparative Example 6

[0100] Compared with Example 1, the only difference is that the coal gasification coal slime is used in the filter aid instead of the gravity separation material (that is, the coal gasification coal slime is not subjected to gravity separation and is directly compounded with the modifier to form the filter aid). Other operations and parameters are the same as those in Example 1.

[0101] The test results are:

[0102]

[0103] In summary, the use of the reselected material of the present invention in combination with the composite modifier can unexpectedly achieve synergy and improve the dehydration effect.

Claims

1. A filter aid modifier for activated sludge dehydration, characterized in that: It includes anionic polyacrylamide, a compound of formula 1 and a compound of formula 2; Formula 1 Formula 2 In Formula 1, R1 and R2 are independently H, C1-C6 alkyl, C1-C6 alkoxy, halogen, trifluoromethyl or nitro; M is H, Na, K or NH4; R3 is a C2-C8 alkyl group, a methylene group with a substituent, a phenyl group, or a phenyl group with a substituent; The substituent in the substituted methylene group is hydroxy, C1-C6 alkoxy, halogen, nitro or trifluoromethyl; The substituent in the phenyl group with a substituent is a hydroxyl group, a C1-C3 alkyl group, a C1-C6 alkoxy group, a halogen group, a nitro group or a trifluoromethyl group.

2. The filter aid modifier according to claim 1, wherein The molecular weight of the anionic polyacrylamide is 1.0×10 5 ~2×10 8 .

3. The filter aid modifier according to claim 2, wherein The molecular weight of the anionic polyacrylamide is 1.2×10 7 ~1.6×10 7 .

4. The filter aid modifier according to claim 1, wherein In formula 1, R1 and R2 are both H, and M is Na.

5. The filter aid modifier according to claim 1, wherein In Formula 2, R3 is a phenyl group or a phenyl group with a substituent, and the substituent is a hydroxyl group, a C1-C3 alkyl group, or a C1-C3 alkoxy group.

6. The filter aid modifier according to claim 1, wherein The weight ratio of anionic polyacrylamide, formula 1 and formula 2 is 0.05-5:0.5-10:0.2-3.

7. The filter aid modifier according to claim 6, wherein The weight ratio of anionic polyacrylamide, formula 1 and formula 2 is 0.1-0.5:1-5:1-2.

8. The filter aid modifier according to claim 6, wherein The weight ratio of anionic polyacrylamide, formula 1 and formula 2 is 0.2-0.4:2-4:1-2.

9. An activated sludge dewatering filter aid, characterized in that: Comprising a reselected material of coal gasification coal slime and the filter aid modifier according to any one of claims 1 to 8; The re-selected material is the remaining material after the heavy components are removed from the coal gasification slime through re-selection.

10. The activated sludge dewatering filter aid according to claim 9, characterized in that: The re-selected material is the coal slime with a density greater than 2.4g / m3 that is reduced by re-selection. 3 The remaining material of the heavy component.

11. The activated sludge dewatering filter aid according to claim 9 or 10, characterized in that: In the activated sludge dewatering filter aid, the weight content of the filter aid modifier is 0.5-20%.

12. The activated sludge dewatering filter aid according to claim 11, wherein In the activated sludge dewatering filter aid, the weight content of the filter aid modifier is 2-10%.

13. A method for preparing the activated sludge dewatering filter aid according to any one of claims 9 to 12 by using coal gasification sludge, characterized in that: The coal gasification slime is subjected to gravity separation to reduce the heavy components therein to obtain gravity separation material; the gravity separation material is compounded with the filter aid modifier to obtain the filter aid.

14. The method according to claim 13, wherein The gravity separation material is a single-stage gravity separation material, which comprises the following steps: slurrying the gasified coal to obtain a slurry, gravity separation the slurry, removing 5-40% of the original weight of heavy components, collecting the light components and medium components therein, and obtaining the single-stage gravity separation material; The coal gasification slime has a mass proportion of 70-75% between 0.05 and 0.2 mm.

15. The method according to claim 14, wherein The slurry mass concentration is 10%~50%.

16. The method according to claim 15, wherein The slurry mass concentration is 15%~30%.

17. The method according to claim 14, wherein The removed heavy components account for 10~40% of the original weight.

18. The method according to claim 17, wherein The removed heavy components account for 20~30% of the original weight.

19. The method according to claim 14, wherein The gravity separation material is a two-stage gravity separation material, and the steps are: subjecting the single-stage gravity separation material to liquid phase grinding treatment to obtain a two-stage ore pulp, and then subjecting it to a second-stage gravity separation treatment to continue to remove heavy components, collect light components and medium components, and obtain a two-stage gravity separation material.

20. The method according to claim 19, wherein The mass concentration of the second stage slurry is 10%~70%.

21. The method according to claim 20, wherein The mass concentration of the second stage slurry is 30%~55%.

22. The method according to claim 20, wherein The proportion of -0.075mm particles in the second stage slurry is not less than 70%.

23. The method according to claim 22, wherein The proportion of -0.075mm particles in the second stage slurry is 85%~95%.

24. The method of claim 22, wherein: In the second-stage gravity separation material, the total mass of the collected light components and intermediate components accounts for 60~90wt%.

25. The method of claim 24, wherein: In the second-stage gravity separation material, the total mass of the collected light components and intermediate components accounts for 70~80wt%.

26. The method according to any one of claims 13 to 25, wherein: The reselected material is dried and mixed evenly with the filter aid modifier in a kneader, and dried to obtain the filter aid.

27. Use of the filter aid according to any one of claims 9 to 12 or the filter aid prepared by the preparation method according to any one of claims 13 to 26, characterized in that: It is used as a filter aid for dewatering activated sludge.

28. The use according to claim 27, characterized in that The water content of the activated sludge is greater than or equal to 70%.

29. The use according to claim 27, characterized in that Calculated on the dry weight of activated sludge, the amount of filter aid used is greater than or equal to 1 kg / t.

30. The use according to claim 29, characterized in that Based on the dry weight of activated sludge, the dosage of filter aid is 20~100kg / t.

31. The use according to claim 30, characterized in that Based on the dry weight of activated sludge, the dosage of filter aid is 20~60kg / t.

32. The use according to claim 30, wherein Based on the dry weight of activated sludge, the dosage of filter aid is 30 kg / t~50 kg / t.

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