A process for co-processing sludge pyrolysis and fly ash

Abstract

The present application discloses a co-processing technology for oily sludge pyrolysis and fly ash, which relates to the technical field of hazardous waste treatment and includes an oily sludge pyrolysis waste gas treatment process and a fly ash treatment process; the oily sludge pyrolysis process includes the following steps: A1 pyrolysis; A2 high-temperature melting; the fly ash process includes the following steps: B1 pulping; B2 water washing; B3 decalcification treatment; B4 crystallization separation. In the technical solution of the present application, the products in the treatment process of oily sludge and the fly ash treatment process react with each other, saving the caustic solution required for alkali washing in the pyrolysis waste gas; saving the calcium remover required in the process of removing calcium by water washing of fly ash; reducing the chemical agent cost of fly ash water washing; the calcium content in the fly ash after water washing is reduced, which can reduce the amount of additional quartz stone and iron powder in the subsequent high-temperature melting compatibility, reducing the production cost. And the heat of the pyrolysis gas is used to dry the filter cake made from the filter cake, recovering and utilizing the heat of the pyrolysis gas, and reducing the energy consumption of filter cake drying.

Description

Technical Field

[0001] This application relates to the technical field, in particular to the co-processing technology of oily sludge pyrolysis and fly ash. Background Art

[0002] Oily sludge is a waste generated in petrochemical processes such as oil production and refining processes, belonging to hazardous waste, and the waste category belongs to waste mineral oil and waste containing mineral oil (code HW08). Due to its high viscosity, high humidity, high ash content, and rich harmful elements, it is difficult to dispose of oily sludge. Currently, the resource recovery methods for high-oil-content sludge include solvent extraction method, centrifugal separation method, ultrasonic method, and pyrolysis method, etc. The solvent extraction method has problems such as large solvent consumption, easy cost increase, and serious secondary pollution; the centrifugal separation method is difficult to reduce the oil content of oily sludge below 2%; the ultrasonic method can only treat a small amount of oily sludge at present and is difficult to be used in large-scale processes; the pyrolysis method is a new technology developed in recent years, with the advantages of high treatment efficiency and recovery of some energy. The composition of oily sludge is complex, not only containing a large amount of aged crude oil, asphaltene, wax, colloid, bacteria, solid suspended matter, salts, corrosive products, acidic gases, etc., but also including water treatment agents such as corrosion inhibitors, flocculants, bactericides, and scale inhibitors added during the production process. Therefore, after pyrolysis treatment, the exhaust gas will contain a lot of acidic gases, especially sulfur-containing acidic gases. Typical small-molecule sulfur-containing pollutants include H2S, SO2, CS2, and CH4S, which need to be absorbed and treated with alkali solution.

[0003] Incineration fly ash (hereinafter referred to as fly ash) is a powder substance collected in the flue gas purification equipment during the waste incineration power generation process, belonging to hazardous waste, and the waste category belongs to incineration disposal residue (code HW18). The chloride ion content in waste incineration fly ash is relatively high, and chloride ions can affect the volatility of metal elements by affecting their forms. For incineration wastes containing a large amount of chlorinated substances such as kitchen waste and PVC plastics, the chlorination effect during combustion is very obvious. Currently, the chloride ion content in fly ash is between 10 - 20%, and these chloride ions will affect the subsequent high-temperature melting resource treatment. Therefore, it is necessary to carry out the pre-treatment of water washing in the early stage.

[0004] The main components in fly ash are CaO, Al2O3, and SiO2. Especially CaO accounts for 40 - 50% of the total amount. With a relatively high calcium content, to form vitrified products, elements such as silicon and iron need to be supplemented, which will increase the cost of high-temperature melting of fly ash. Therefore, removing most of the calcium during the water washing process helps to reduce the compatibility cost of subsequent high-temperature melting. Removing calcium from fly ash by water washing requires adding additional calcium removers (such as Na2SO4 or Na2CO3), which will also increase the cost of water washing. Summary of the Invention

[0005] To solve at least one of the above technical problems and develop a process that can reduce the cost of sludge treatment, reduce the cost of fly ash water washing, and reduce the calcium and chloride ion contents in the filter cake during fly ash treatment, the present application provides a co-processing process for sludge pyrolysis and fly ash.

[0006] A co-processing process for sludge pyrolysis and fly ash provided by the present application includes a sludge pyrolysis waste gas treatment process and a fly ash treatment process;

[0007] The sludge pyrolysis process includes the following steps:

[0008] A1 Pyrolysis

[0009] Mix the sludge with other organic hazardous wastes, send the mixture into the pyrolysis furnace for pyrolysis after uniform mixing, and generate pyrolysis gas and carbonized slag; A2 High-temperature melting

[0010] Mix the carbonized slag obtained in step A1 with the filter cake and perform high-temperature melting treatment;

[0011] The fly ash process includes the following steps:

[0012] B1 Pulping

[0013] Input the fly ash into the pulping tank, add water and stir to make a slurry;

[0014] B2 Water washing

[0015] Wash the slurry prepared in step B1, perform solid-liquid separation to obtain a filter cake and wastewater, dry the filter cake using the waste heat of the pyrolysis gas in step A1, and use the dried filter cake for mixing with the carbonized slag in step A2;

[0016] B3 Decalcification treatment

[0017] Pass the pyrolysis gas generated in step A1 into the wastewater obtained in step B2 to decalcify the wastewater;

[0018] B4 Crystallization separation

[0019] Crystallize the wastewater after decalcification treatment in step B3, and separate the crystals from the liquid; the separated liquid is used for water washing in step B2.

[0020] By adopting the above technical solutions, the products in the treatment process of oily sludge and the fly ash treatment process react with each other, saving the lye required for alkali washing in the pyrolysis waste gas; saving the calcium remover required in the process of removing calcium from fly ash by water washing; reducing the chemical agent cost of fly ash water washing; reducing the calcium content in the fly ash after water washing, which can reduce the amount of additional quartzite and iron powder in the subsequent high-temperature melting compatibility, and reducing the production cost. And the filter cake is dried using the waste heat of the pyrolysis gas, recycling the waste heat of the pyrolysis gas and reducing the energy consumption of filter cake drying.

[0021] Optionally, in the pulping step B1, the weight ratio of the fly ash to water is 1:3-4.

[0022] By adopting the above technical solution, it is ensured that the ions in the fly ash are fully dissolved, and at the same time, the amount of water used is minimized to reduce the subsequent wastewater treatment cost.

[0023] Optionally, in the water washing step B2, the weight ratio of liquid to solid is maintained at 3:1 or more.

[0024] By adopting the above technical solution, the ion precipitation amount of the filter cake in the water washing is increased, and at the same time, the amount of water used is minimized to reduce the subsequent wastewater treatment cost.

[0025] Optionally, in the water washing step B2, the water content of the filter cake after solid-liquid separation is not higher than 35%, and the water content of the filter cake after drying is not higher than 15%.

[0026] By adopting the above technical solution, the water content of the filter cake after solid-liquid separation is reduced, so that calcium ions and the like free in the water are separated from the filter cake, and the content of calcium ions and the like in the subsequent filter cake is reduced; reducing the water content of the filter cake after drying can reduce the energy consumption of subsequent high-temperature melting.

[0027] Optionally, the water washing step B2 includes the following steps:

[0028] B2.1 Primary water washing

[0029] The slurry obtained in step B1 is washed with a washing liquid, and solid-liquid separation is performed to obtain a primary filter cake and primary wastewater;

[0030] B2.2 Secondary water washing

[0031] The primary filter cake obtained in step B2 is washed with a washing liquid, and after solid-liquid separation, a secondary filter cake and secondary wastewater are obtained;

[0032] B2.3 Tertiary water washing

[0033] The primary filter cake obtained in step B3 is washed with a washing liquid, and after solid-liquid separation, a tertiary filter cake and tertiary wastewater are obtained.

[0034] By adopting the above technical solution, the tertiary water washing can reduce the content of calcium ions and the like in the tertiary filter cake, which can not only reduce the impact on subsequent high-temperature melting, but also improve the absorption of carbon dioxide and sulfur-containing acidic gases in the pyrolysis gas.

[0035] Optionally, the secondary wastewater generated in the secondary water washing step B2.2 is used as the washing liquid in the primary water washing step B2.1; the tertiary wastewater generated in the tertiary water washing step B2.3 is used as the washing liquid in the secondary water washing step B2.2.

[0036] By adopting the above technical solution, the medium-chlorine wastewater generated from the secondary water washing is reused in the primary water washing, and the low-chlorine wastewater generated from the tertiary water washing is reused in the secondary water washing; while ensuring the water washing effect, the water consumption is reduced, and the cost of wastewater treatment is reduced; and calcium ions in the wastewater are enriched to the greatest extent to form a high-concentration waste liquid for reuse.

[0037] Optionally, the primary wastewater generated in the primary water washing in step B2.1 is used in the decalcification treatment in step B3 and reacts with the pyrolysis gas generated in step A1 for decalcification treatment.

[0038] By adopting the above technical solution, the primary wastewater with a high chlorine content reacts with the pyrolysis gas to absorb the acidic gas in the pyrolysis gas, saving the usage amount of lye.

[0039] Optionally, in the crystallization separation in step B4, an MVR evaporation system is used to crystallize the wastewater.

[0040] Optionally, the distilled water generated by evaporation in the crystallization separation in step B4 is used as the washing liquid in the tertiary water washing in step B2.3.

[0041] By adopting the above technical solution, the distilled water generated by the evaporation system is recycled, and the distilled water is used as the washing liquid in the tertiary water washing in step B2.3, which can fully dissolve calcium ions, sodium ions, potassium ions, etc. in the filter cake. It can not only improve the recycling of these ions, but also reduce the influence of calcium ions on the high-temperature melting of the compatibility between the filter cake and the carbonized slag.

[0042] Optionally, the crystals obtained in the crystallization separation in step B4 are successively subjected to sodium salt centrifugation treatment and potassium salt centrifugation treatment.

[0043] By adopting the above technical solution, sodium chloride and potassium chloride in the crystals are separated by centrifugation; since the temperature of the crystals is relatively high after crystallization separation, according to the different solubility changes of sodium chloride and potassium chloride with temperature, sodium chloride and potassium chloride are successively separated and recycled.

[0044] In summary, the present invention includes at least one of the following beneficial technical effects:

[0045] This application collaboratively treats the oily sludge treatment process and the fly ash treatment process. The products in the two processes react with each other, saving the lye required for alkali washing in the pyrolysis waste gas; saving the calcium remover required in the calcium removal process of fly ash water washing; reducing the chemical agent cost of fly ash water washing; reducing the calcium content in the fly ash after water washing, which can reduce the amount of additional quartz stone and iron oxide in the subsequent high-temperature melting compatibility, reducing the production cost. And the filter cake is dried using the waste heat of the pyrolysis gas, recycling the waste heat of the pyrolysis gas and reducing the energy consumption of filter cake drying. Description of the Drawings

[0046] Figure 1 This is the process flow chart of Embodiment 1 of the present application;

[0047] Figure 2 This is the process flow chart of Embodiment 3 of the present application;

[0048] Figure 3 This is the process flow chart of Embodiment 4 of the present application;

[0049] Figure 4 This is the process flow chart of Embodiment 5 of the present application. Detailed Description of the Invention

[0050] The present application designs a co - treatment process for oily sludge pyrolysis and fly ash, including an oily sludge pyrolysis waste gas treatment process and a fly ash treatment process;

[0051] The oily sludge pyrolysis process includes the following steps:

[0052] A1 Pyrolysis

[0053] Mix the oily sludge with other organic hazardous wastes, send the mixture into a pyrolysis furnace for pyrolysis after uniform mixing to generate pyrolysis gas and carbonized slag; A2 High - temperature melting

[0054] Mix the carbonized slag obtained in A1 with filter cake and conduct high - temperature melting treatment;

[0055] The fly ash process includes the following steps:

[0056] B1 Pulping

[0057] Input the fly ash into a pulping tank, add water and stir to make a slurry;

[0058] B2 Water washing

[0059] Wash the slurry obtained in B1, conduct solid - liquid separation to obtain filter cake and wastewater. The filter cake is dried using the waste heat of the pyrolysis gas in A1, and the dried filter cake is used for mixing with the carbonized slag in A2;

[0060] B3 Decalcification treatment

[0061] Pass the pyrolysis gas generated in A1 into the wastewater obtained in B2 to conduct decalcification of the wastewater;

[0062] B4 Crystallization and separation

[0063] Crystallize the wastewater after B3 decalcification treatment, and separate the crystallized product from the liquid; the separated liquid is used for water washing in B2.

[0064] During the process of treating fly ash and oily sludge, the applicant uses pyrolysis to treat the sludge, which will produce carbonized slag and pyrolysis gas. Among them, the pyrolysis gas contains a lot of acidic gases, including H2S, SO2, CS2 and CH4S, which cannot be directly discharged and require a lot of lye for neutralization treatment. When treating fly ash, the filter cake contains a relatively high amount of chloride ions and calcium (present in the form of calcium oxide), which requires a large amount of quartzite and iron powder during subsequent high-temperature melting, resulting in high costs.

[0065] The applicant adds water to the filter cake produced by fly ash treatment to form lye (calcium oxide reacts with water to form calcium hydroxide solution), and passes the acidic gas generated by the pyrolysis of oily sludge into the lye, which can not only absorb the acidic gas, but also react the sulfur-containing acidic gas and carbon dioxide with calcium hydroxide to form calcium sulfate and calcium carbonate precipitates; moreover, the carbonized slag produced by treating oily sludge can be compatible with the filter cake and, after high-temperature melting treatment, reduce the harm.

[0066] Therefore, the applicant designed the co-treatment process of oily sludge pyrolysis and fly ash. In the oily sludge pyrolysis process, the oily sludge is pyrolyzed after being compatible with organic matter, generating pyrolysis gas containing carbon dioxide and sulfur-containing acidic gas and carbonized slag. The pyrolysis gas is passed into the washing liquid produced by water washing in the fly ash treatment process and reacts with the calcium hydroxide contained therein to precipitate the carbon dioxide and sulfur-containing acidic gas in the pyrolysis gas and the calcium ions in the fly ash, and then the precipitate is removed by solid-liquid separation; and the filter cake with most of the calcium ions removed is compatible with the carbonized slag and then subjected to high-temperature melting treatment.

[0067] Reacting the products in the treatment process of oily sludge with those in the fly ash treatment process saves the lye required for alkali washing in the pyrolysis waste gas; saves the calcium remover required in the process of removing calcium by water washing of fly ash; reduces the chemical agent cost of fly ash water washing; reduces the calcium content in the fly ash after water washing, enabling the subsequent high-temperature melting compatibility to reduce the amount of additional quartzite and iron powder, and reducing the production cost. Moreover, the filter cake is dried using the waste heat of the pyrolysis gas, recovering the waste heat of the pyrolysis gas and reducing the energy consumption for drying the filter cake.

[0068] The sources and test performance results of the products involved in this application are as follows.

[0069] HW08 type oily sludge: Jiangyin Bosen Environmental Protection Technology Co., Ltd.;

[0070] HW49 type woven bags: Shijiazhuang Ruili Packaging Products Co., Ltd.;

[0071] HW13 type organic resin sludge: Zhengzhou Shengbang Chemical Co., Ltd.;

[0072] HW12 type waste paint slag: Fangsong Environmental Protection Technology Hebei Co., Ltd.

[0073]

[0074]

[0075] The following further elaborates on this application in conjunction with the attached Figures 1-4 drawings and embodiments. Specific embodiments

[0077] Embodiment 1

[0078] As Figure 1 shown, mix HW08 oil sludge with HW49 woven bags, HW13 organic resin sludge, and HW12 waste paint slag in a ratio of 10:3:4:3. After mixing evenly, feed it into a pyrolysis furnace for pyrolysis to produce pyrolysis gas and carbonized slag; the pH of the pyrolysis gas is 5 - 6.5.

[0079] Input fly ash into the pulping tank by pneumatic means, add water to the pulping tank according to the weight ratio of fly ash to water of 1:3, and stir into a slurry. The entire pulping tank is in a closed form to ensure that there is no fly ash dust escaping during the stirring process.

[0080] Transport the above-prepared slurry to the water washing tank by a delivery pump, add water for water washing, and stir for 20 minutes; dehydrate the precipitated slurry through a filter press to obtain a filter cake (with a water content of 30%, a chloride ion content of 2%, and a calcium oxide content of 50%) and wastewater with a pH of 12.

[0081] Utilize the waste heat of the pyrolysis gas to dry the above filter cake to a water content of 15%, mix it with the carbonized slag, and carry out high-temperature melting; introduce the pyrolysis gas into the above wastewater. After the reaction is sufficient, carry out solid-liquid separation through a filter press, filter and remove precipitates such as calcium sulfate and calcium carbonate, and the pH of the filtered waste liquid is 8.5. Subject the filtered waste liquid to an MVR evaporation system for sodium salt centrifugation treatment to separate sodium chloride in the waste liquid; then cool down to cause potassium salts in the waste liquid to crystallize out, and separate potassium chloride through centrifugation treatment.

[0082] Embodiment 2

[0083] Mix HW08 oil sludge with HW49 woven bags, HW13 organic resin sludge, and HW12 waste paint slag in a ratio of 10:3:4:3. After mixing evenly, feed it into a pyrolysis furnace for pyrolysis to produce pyrolysis gas and carbonized slag; the pH of the pyrolysis gas is 5 - 6.5.

[0084] Input fly ash into the pulping tank by pneumatic means, add water to the pulping tank according to the weight ratio of fly ash to water of 1:4, and stir into a slurry. The entire pulping tank is in a closed form to ensure that there is no fly ash dust escaping during the stirring process.

[0085] The prepared slurry is transported to a water-washing tank through a delivery pump, and water is added for water washing, followed by stirring for 15 minutes. The precipitated slurry is dehydrated by a filter press to obtain a filter cake (with a water content of 35%, a chloride ion content of 1.8%, and a calcium oxide content of 45%) and wastewater (with a pH of 10).

[0086] The filter cake is dried to a water content of 15% using the waste heat of the pyrolysis gas, and is formulated with carbide slag and then melted at high temperature. The pyrolysis gas is introduced into the above wastewater. After sufficient reaction, solid-liquid separation is carried out by a filter press to filter and remove precipitates such as calcium sulfate and calcium carbonate. The pH of the filtered waste liquid is 8. The filtered waste liquid is processed by an MVR evaporation system for sodium salt centrifugation to separate sodium chloride in the waste liquid; then the temperature is lowered to crystallize potassium salts in the waste liquid, and potassium chloride is separated by centrifugation.

[0087] Example 3

[0088] As Figure 2 shown, the difference between this example and Example 1 is that the water-washing process in the fly ash treatment process of this example is improved on the basis of Example 1, and three-stage water washing is carried out. The specific process is as follows:

[0089] The slurry prepared in the pulping tank is washed with a washing liquid, and solid-liquid separation is carried out to obtain a primary filter cake and primary wastewater; the primary wastewater in this example is used for decalcification treatment and reacts with the pyrolysis gas generated in A1 for decalcification treatment.

[0090] The above primary filter cake is washed with a washing liquid, and after solid-liquid separation, a secondary filter cake and secondary wastewater are obtained.

[0091] The above secondary filter cake is washed with a washing liquid, and after solid-liquid separation, a tertiary filter cake and tertiary wastewater are obtained.

[0092] The washing liquid used in this example is tap water. The total time and total amount of water for the three-stage water washing are the same as the time and amount of water for water washing in Example 1.

[0093] The water content of the tertiary filter cake obtained in this example is 30%, the chloride ion content is 1.1%, the calcium oxide content is 40%, and the pH of the primary wastewater is 12.2.

[0094] The filter cake is dried to a water content of 12% using the waste heat of the pyrolysis gas, and is formulated with carbide slag and then melted at high temperature. The pyrolysis gas is introduced into the primary wastewater. After sufficient reaction, solid-liquid separation is carried out by a filter press to filter and remove precipitates such as calcium sulfate and calcium carbonate. The pH of the filtered waste liquid is 8.7.

[0095] Example 4

[0096] As Figure 3As shown in the figure, the difference between this embodiment and Embodiment 3 is that the water washing process in the fly ash treatment process of this embodiment is improved on the basis of Embodiment 3, and the primary wastewater and secondary wastewater generated in the three-stage water washing are recycled. The specific process is as follows:

[0097] The secondary wastewater in this embodiment is used as the washing liquid in the primary water washing; the tertiary wastewater is used as the washing liquid in the secondary water washing.

[0098] The water content of the tertiary filter cake obtained in this embodiment is 32%, the chloride ion content is 1.2%, the calcium oxide content is 42%, and the pH of the primary wastewater is 12.8.

[0099] Using the waste heat of the pyrolysis gas, the above-mentioned filter cake is dried to a water content of 12.5%, and is formulated with the carbonized slag and melted at high temperature; the pyrolysis gas is introduced into the tertiary wastewater. After the reaction is sufficient, solid-liquid separation is carried out by a filter press, and precipitates such as calcium sulfate and calcium carbonate are filtered out. The pH of the filtered waste liquid is 8.6.

[0100] Embodiment 5

[0101] As Figure 4 shown, the difference between this embodiment and Embodiment 4 is that the distilled water obtained by the MVR evaporation system in this embodiment is used as the washing liquid in the three-stage water washing.

[0102] The water content of the tertiary filter cake obtained in this embodiment is 31.5%, the chloride ion content is 1%, the calcium oxide content is 38%, and the pH of the primary wastewater is 13. Using the waste heat of the pyrolysis gas, the above-mentioned filter cake is dried to a water content of 11.8%, and is formulated with the carbonized slag and melted at high temperature; the pyrolysis gas is introduced into the tertiary wastewater. After the reaction is sufficient, solid-liquid separation is carried out by a filter press, and precipitates such as calcium sulfate and calcium carbonate are filtered out. The pH of the filtered waste liquid is 8.9.

[0103] Through Embodiments 1-2, it can be seen that by jointly treating the oily sludge treatment process and the fly ash treatment process in this application, in the filtered filter cake, the chloride ion content is 1.8-2%, the calcium content (calcium oxide) is 45-50%, and the pH of the filtered wastewater is 10-12, effectively reducing the chloride ion and calcium content in the filter cake. After introducing the pyrolysis gas and reacting sufficiently, the pH of the wastewater drops to 8-8.5, meeting the pH index of the wastewater discharge standard.

[0104] Through Embodiment 3, it can be seen that on the basis of Embodiment 1, the water washing step is improved. After changing the single water washing to three-stage water washing, the chloride ion content in the filtered filter cake is reduced to 1.1%, and the calcium content is reduced to 40%; the pH of the filtered wastewater is 12.2, which can effectively improve the absorption of the pyrolysis gas. After reacting with the pyrolysis gas, the pH of the wastewater drops to 8.7, meeting the pH index of the wastewater discharge standard.

[0105] As can be seen from Example 4, on the basis of Example 3, the wastewater in the three-stage water washing is recycled. The chloride ion content in the filter cake obtained by filtration is 1.2%, and the calcium content is 42%. The pH of the wastewater obtained by filtration is 12.5. In the technical solution of this example, the wastewater in the three-stage water washing is recycled, reducing the water consumption and thus reducing the amount of wastewater.

[0106] As can be seen from Example 5, on the basis of Example 4, distilled water is used as the water for the three-stage water washing, thereby improving the elution rate of chloride ions and calcium oxide in the ash by the three-stage water washing, reducing the chloride ions in the filter cake to 1%, and the calcium content to 38%. And the distilled water comes from the MVR evaporation system, which not only plays a role in reusing the distilled water in the subsequent process, but also reduces the water consumption and the generated wastewater in the whole process.

[0107] The above are all the preferred embodiments of this application. The protection scope of this application is not limited by this. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A process for co - treating sludge pyrolysis and fly ash, characterized in that, It includes the oily sludge pyrolysis waste gas treatment process and the fly ash treatment process; The oily sludge pyrolysis waste gas treatment process includes the following steps: A1 Pyrolysis Mix the oily sludge with other organic hazardous wastes, send the mixture into the pyrolysis furnace for pyrolysis after uniform mixing, and generate pyrolysis gas and carbonized slag; A2 High-temperature melting Mix the carbonized slag obtained in step A1 with the filter cake and conduct high-temperature melting treatment; The fly ash treatment process includes the following steps: B1 Pulp making Input the fly ash into the pulping tank and add water for stirring to make a slurry; B2 Water washing Wash the slurry obtained in step B1 with water, and perform solid-liquid separation to obtain a filter cake and wastewater. The filter cake is dried using the waste heat of the pyrolysis gas in step A1, and the dried filter cake is used for mixing with the carbonized slag in step A2; B3 Decalcification treatment Pass the pyrolysis gas generated in step A1 into the wastewater obtained in step B2 to perform decalcification on the wastewater; B4 Crystallization separation Crystallize the wastewater after decalcification treatment in step B3, and separate the crystals from the liquid; the separated liquid is used for water washing in step B2.

2. The sludge pyrolysis and fly ash co-treatment process according to claim 1, wherein, In the pulp making of step B1, the weight ratio of the fly ash to water is 1:3 - 4.

3. The sludge pyrolysis and fly ash co-treatment process according to claim 1, characterized in that, In the water washing of step B2, the weight ratio of liquid to solid is maintained at 3:1 or more.

4. The sludge pyrolysis and fly ash co-treatment process according to claim 1, characterized in that, In the water washing of step B2, the water content of the filter cake after solid-liquid separation is not higher than 35%, and the water content of the dried filter cake is not higher than 15%.

5. The sludge pyrolysis and fly ash co-treatment process according to claim 1, characterized in that, The water washing of step B2 includes the following steps: B2.1 Primary water washing Wash the slurry obtained in step B1 with the washing liquid, and perform solid-liquid separation to obtain a primary filter cake and primary wastewater; B2.2 Secondary water washing Wash the primary filter cake obtained in step B2.1 with the washing liquid, and perform solid-liquid separation to obtain a secondary filter cake and secondary wastewater; B2.3 Tertiary water washing Wash the secondary filter cake obtained in step B2.2 with the washing liquid, and perform solid-liquid separation to obtain a tertiary filter cake and tertiary wastewater.

6. The sludge pyrolysis and fly ash co-treatment process according to claim 5, characterized in that, The secondary wastewater generated in the secondary water washing of step B2.2 is used as the washing liquid in the primary water washing of step B2.1; the tertiary wastewater generated in the tertiary water washing of step B2.3 is used as the washing liquid in the secondary water washing of step B2.

2.

7. The sludge pyrolysis and fly ash co-treatment process according to claim 5, characterized in that The primary wastewater generated in the primary water washing of step B2.1 is used in the decalcification treatment of step B3 to react with the pyrolysis gas generated in step A1 for decalcification treatment.

8. The sludge pyrolysis and fly ash co-treatment process according to claim 5, characterized in that, In the crystallization separation of step B4, an MVR evaporation system is used to crystallize the wastewater.

9. The sludge pyrolysis and fly ash co-treatment process according to claim 8, characterized in that The distilled water generated by evaporation in the crystallization separation of step B4 is used as the washing liquid in the tertiary water washing of step B2.

3.

10. The sludge pyrolysis and fly ash co-treatment process according to claim 1, characterized in that, The crystallization separation of step B4 includes successively performing sodium salt centrifugation treatment and potassium salt centrifugation treatment.

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