Method for preparing adsorbent from fly ash, adsorbent and application of adsorbent in waste incineration flue gas purification

Abstract

The invention relates to the field of resource utilization of waste incineration fly ash, and particularly discloses a method for preparing an adsorbent from fly ash, the adsorbent and application of the adsorbent in waste incineration flue gas purification. The method for preparing the adsorbent by using the fly ash comprises a fly ash pretreatment process, a material mixing process, a secondary water washing liquid modification process, a secondary acid washing liquid modification process and a screening process, wherein biological straws, fruit peels and pretreated fly ash are used as raw materials in the material mixing process; in the secondary washing liquid modification process and the secondary pickling liquid modification process, a secondary washing liquid and a secondary pickling liquid collected in the fly ash pretreatment process are used as treating agents respectively; the prepared adsorbent has an excellent adsorption and removal effect on heavy metal lead and dioxin in flue gas, resource utilization of fly ash, straw and fruit peel garbage is achieved, the disposal problem of corresponding garbage is also solved, fly ash zero emission of a garbage incineration power plant is easily achieved, landfill disposal of fly ash is reduced, and land resources are saved.

Description

Technical Field

[0001] The present application relates to the field of resource utilization of fly ash from waste incineration, and more specifically, to a method for preparing an adsorbent using fly ash, the adsorbent and its application in the purification of flue gas from waste incineration. Background Art

[0002] Waste incineration fly ash is a secondary pollutant produced after waste incineration, accounting for about 3% to 5% of the total waste incineration, containing a large amount of easily leached heavy metals, and is a hazardous waste. At the same time, the flue gas produced by waste incineration contains heavy metals such as lead and organic pollutants such as dioxins, which are easy to cause secondary pollution.

[0003] Among the methods of fly ash disposal, solidification / stabilization-landfill technology is currently one of the main technologies for fly ash disposal in China, but it has potential environmental risks such as large land occupation, dioxin penetration and heavy metal leaching. Melting / vitrification technology has good volume reduction effect, and is effective in solidifying most heavy metals and removing dioxins, but its energy consumption is relatively high. Cement kiln co-treatment technology can effectively remove dioxins and solidify more than 99% of heavy metals in fly ash, but it needs to add fly ash pretreatment process and concentrated salt wastewater treatment facilities before entering the kiln, and the investment cost is relatively high.

[0004] Therefore, there are generally problems such as high cost, high energy consumption, and serious secondary pollution in the fly ash disposal process. It is urgent to find an effective way to effectively treat fly ash and save land resources. Summary of the invention

[0005] In order to achieve low-cost and low-energy disposal of incineration fly ash and reduce secondary pollution, the present application provides a method for preparing an adsorbent using fly ash, the adsorbent and its application in the purification of waste incineration flue gas.

[0006] In a first aspect, the present application provides a method for preparing an adsorbent using fly ash, using the following technical solution: A method for preparing an adsorbent using fly ash comprises the following steps: S1. Washing, acid washing and drying the waste incineration fly ash in sequence to obtain pre-treated fly ash for standby use; during the pre-treatment process, the water washing step and the acid washing step are repeated at least once, and the secondary water washing liquid of the water washing step and the secondary acid washing liquid of the acid washing step are collected for standby use; S2, uniformly mixing 15-20wt% of biostraw, 25-35wt% of peel and the remainder of the pretreated fly ash obtained in step S1 to obtain a mixed material; S3, using the secondary water washing liquid collected in step S1 to immerse the mixed material obtained in step S2, the solid-liquid ratio of the immersion treatment is 0.2-0.5kg / L, the immersion time is 2-3h, and the mixture is filtered and dried to obtain modified material A; S4, mixing the secondary pickling liquid collected in step S1 with anhydrous ethanol in a volume ratio of (2.4-3):1 to obtain a modified acid solution; impregnating the modified material A obtained in step S3 with the modified acid solution, wherein the solid-liquid ratio of the impregnation treatment is 0.2-0.4 kg / L, the immersion time is 1.5-2 h, and filtering and drying are performed to obtain a modified material B; S5. Screening the modified material B obtained in step S4 to obtain an adsorbent.

[0007] By adopting the above technical solution: 1. Due to the strong alkalinity and high hardness of fly ash itself, the water wash liquid and the acid wash liquid contain high concentrations of NaOH solution and CaCl2 solution respectively, which are used to treat fly ash and biomatrix and modify them, introduce new hydroxyl functional groups, increase the stability of the adsorbent and the surface porous structure, and enhance the adsorption effect.

[0008] 2. Using fly ash from garbage incineration, biomass straw and fruit peel as raw materials for making adsorbents can solve the disposal problems of these industrial wastes (fly ash) and domestic wastes (biomass straw and fruit peels) at the same time, and realize resource recycling; the raw materials used in the preparation of the adsorbent and the equipment or devices used in other processes can be selected from the original ones in the factory, which has low energy consumption and less additional investment, and has the characteristics of simple process, low processing cost and small footprint.

[0009] 3. In the modification process, water washing liquid and acid washing liquid are used to treat fly ash, straw and peel respectively. Only a small amount of anhydrous ethanol is added, and no additional reagents are added, which saves the cost of reagents. The raw materials are easy to obtain, which is an economically feasible way to utilize fly ash resources.

[0010] 4. The prepared adsorbent has a good effect on the adsorption and removal of heavy metals and dioxins, and can be reused in the incinerator for incineration and power generation after reaching the adsorption capacity, thus achieving zero fly ash emissions from waste incineration power plants.

[0011] Furthermore, in the S3 step and the S4 step, during the immersion treatment, stirring is performed at a speed of 150-200 r / min for 3 min every 0.5 h.

[0012] Furthermore, in the step S5, the sieve is sieved with 200 meshes, which is beneficial to increase the specific surface area of ​​the adsorbent and to adsorb and remove pollutants in the flue gas.

[0013] Furthermore, in the S2 process, the biostraw and the peel are crushed and sieved through a 100-mesh sieve.

[0014] Furthermore, the bio-straw and peels are from existing domestic waste from waste incineration power plants. Using domestic waste as raw materials is low in cost and can solve the problem of domestic waste disposal in the plant area.

[0015] Furthermore, the biological straw includes at least one of corn straw, wheat straw, rice straw, cotton straw and sorghum straw; the fruit peel includes at least one of orange peel, tangerine peel, grapefruit peel, lemon peel, banana peel, apple peel, pear peel, peach peel, watermelon peel, cantaloupe peel and dragon fruit peel.

[0016] Furthermore, in step S1, the pH of the collected secondary washing liquid is ≥12.

[0017] Furthermore, in the S1 step, the water washing solid-liquid ratio is 0.8-1.2 kg / L.

[0018] Furthermore, in step S1, the stirring speed during the water washing process is 150-200 r / min, and the stirring is continued for 30-45 min.

[0019] Furthermore, in the S1 process, the fly ash from the waste incineration is washed with recycled water. The recycled water is obtained by treating domestic sewage and meets the standard of "Urban Sewage Recycling·Industrial Water" (GB / T19923-2024).

[0020] Furthermore, in step S1, the waste incineration fly ash is acid-washed with hydrochloric acid having a concentration of 0.5-0.8 mol / L.

[0021] Furthermore, in the S1 process, the pickling solid-liquid ratio is 0.4-0.6 kg / L.

[0022] Furthermore, during the pickling process, the stirring speed is 100-150 r / min, and the stirring is continued for 20-30 min.

[0023] In the second aspect, the present application provides an adsorbent, which is prepared by the adsorbent preparation method described in any of the above items. Furthermore, the adsorbent has an adsorption rate of lead in flue gas ≥90%, and a dioxin removal rate ≥85%. This adsorbent has a good adsorption effect and realizes "waste treatment with waste". After reaching the adsorption capacity, the adsorbent can be collected in the form of ash through a dust removal system. Because it contains a high carbon-based substance and has a certain recycling value, it can be reused in an incinerator for incineration and power generation, achieving zero emission of fly ash from waste incineration power plants, reducing the subsequent reduction and harmless treatment procedures of fly ash, reducing the landfill volume of fly ash, and helping to ease the tension in land resources.

[0024] In a third aspect, the present application provides an application of the aforementioned adsorbent in the purification of flue gas from waste incineration. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 4 is a process flow chart for preparing the adsorbent in the embodiment. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present application will be further described in detail below in conjunction with the accompanying drawings.

[0027] [Example 1] A method for preparing an adsorbent, referring to Figure 1 , the specific process is as follows: S1 fly ash pretreatment process: First, the waste incineration fly ash from the waste incineration power plant is washed once with recycled water, the solid-liquid ratio of the washing is 0.8kg / L, the stirring speed is 200r / min during the washing process, and the stirring is continued for 30min; the recycled water used is obtained from the treatment of domestic sewage, which meets the standard of "Urban Sewage Recycling·Industrial Water" (GB / T19923-2024). After the first washing, the filtrate is filtered and the filtrate is washed twice with the filtrate. The stirring speed is 200r / min during the washing process, and the stirring is continued for 30min. The filtrate obtained by filtration is the secondary washing liquid, the pH of which is ≥12 and is temporarily stored for use; the filtrate is the washed fly ash.

[0028] Then, the washed fly ash obtained in the previous step is pickled once with hydrochloric acid at a concentration of 0.8 mol / L, the solid-liquid ratio of the pickling is 0.4 kg / L, the stirring speed during the pickling process is 150 r / min, and the stirring is continued for 20 minutes. After the first pickling, the filtrate is filtered and the filtrate is pickled twice with the filtrate, the stirring speed during the pickling process is 150 r / min, and the stirring is continued for 20 minutes. The filtrate obtained by the suction filtration is the secondary pickling liquid, which is temporarily stored for use; the filtrate is the pickled fly ash.

[0029] Finally, the acid-washed fly ash obtained in the preceding step of drying is used to obtain pretreated fly ash, which is used as a raw material for making an adsorbent.

[0030] S2 Raw material mixing process: Separate the biostraw and peel from the domestic waste of the waste incineration power plant, crush and pass through a 100-mesh sieve to obtain the biostraw and peel raw materials for standby use. The types of biostraw and peel are not limited. The biostraw includes at least one of corn straw, wheat straw, rice straw, cotton straw and sorghum straw, and the peel includes at least one of orange peel, tangerine peel, grapefruit peel, lemon peel, banana peel, apple peel, pear peel, peach peel, watermelon peel, cantaloupe peel and dragon fruit peel, depending on the type of domestic waste. According to the ratio of 20wt% of biostraw, 35wt% of peel and 45wt% of pre-treated fly ash, the biostraw, peel and pre-treated fly ash obtained in step S1 are evenly mixed to obtain a mixed material.

[0031] S3 secondary water washing liquid modification process: The mixed material obtained in step S2 was impregnated with the secondary water washing liquid collected in step S1. The solid-liquid ratio of the impregnation treatment was 0.2 kg / L and the immersion time was 3 h. During the impregnation treatment, the material was stirred at a speed of 200 r / min for 3 min every 0.5 h, filtered and dried to obtain modified material A.

[0032] S4 secondary pickling liquid modification process: First, the secondary pickling liquid collected in the S1 process and anhydrous ethanol are mixed in a volume ratio of 2.4:1 to obtain a modified acid solution; then the modified acid solution is used to impregnate the modified material A obtained in the S3 process. The solid-liquid ratio of the impregnation treatment is 0.2 kg / L, the immersion time is 2 h, and the impregnation treatment is stirred at a speed of 200 r / min for 3 min every 0.5 h, filtered, and dried to obtain modified material B.

[0033] S5 screening process: the modified material B obtained in the S4 process is passed through a 200-mesh sieve to obtain an adsorbent with a mesh number ≤ 200 mesh.

[0034] [Example 2-3] Examples 2-3 are all based on Example 1, with the only difference being that the process parameters of the S1 fly ash pretreatment step are different, as shown in Table 1 for details.

[0035] Table 1. Process parameters of fly ash pretreatment process

[0036] In Examples 2-3, adsorbents with a mesh size of ≤200 mesh were prepared.

[0037] [Examples 4-8] Examples 4-8 are all based on Example 2, with the only difference being that in the S2 raw material mixing process, the mixing ratios of biostraw, peel and pretreated fly ash are different, as shown in Table 2 for details.

[0038] Table 2. Mixture ratio table (by weight percentage)

[0039] In Examples 4-8, adsorbents with a mesh size of ≤200 mesh were prepared.

[0040] [Examples 9-10] Examples 9-10 are all based on Example 2, and the only difference is that the process parameters of the S3 secondary water washing liquid modification step are different, as shown in Table 3.

[0041] Table 3. Secondary water washing liquid modification process parameters In Examples 9-10, adsorbents with a mesh size of ≤200 mesh were prepared.

[0042] [Examples 11-14] Examples 11-14 are all based on Example 10, with the only difference being that the process parameters of the S4 secondary pickling solution modification step are different, as shown in Table 4 for details.

[0043] Table 4. Secondary pickling solution modification process parameters

[0044] Examples 11-14 all prepared adsorbents with a mesh size of ≤200 mesh.

[0045] [Comparative Example 1] Comparative Example 1 is based on Example 1, with the only difference being that in the S2 raw material mixing process, an equal amount of bio-straw is used instead of the peel.

[0046] [Comparative Example 2] Comparative Example 2 is based on Example 1, with the only difference being that in the S2 raw material mixing process, an equal amount of fruit peel is used instead of biological straw.

[0047] [Performance test] Test 1: The adsorbent of each embodiment / control example was taken as a sample, and the waste incineration flue gas at 52°C was adsorbed. The mass volume ratio of the adsorbent to the flue gas was 20g / L. The lead (Pb) concentration and dioxin (PCDD / Fs) concentration in the flue gas before and after the treatment were tested, and the corresponding removal rate was calculated. The results are shown in Table 5.

[0048] Test 2: Organic pollutant adsorption and removal efficiency test, taking the chlorinated aromatic model compound o-DCB as the representative of organic pollutants, 80 mg of adsorbent was loaded into a stainless steel adsorption bed (inner diameter: 5 mm), and quartz wool pads were loaded at both ends of the adsorbent. The fixed bed adsorption-online detection system was used to evaluate the performance of the adsorption and removal of the chlorinated aromatic model compound o-DCB in the gas phase of each embodiment / control example. The o-DCB after adsorption was detected by GC-FID, and the o-DCB removal rate was calculated. Adsorption conditions: total gas flow rate of 60 mL / min, O2 content of 5%, o-DCB concentration of 150 ppm, adsorbent mass of 80 mg, adsorption temperature of 50 ° C, and adsorption time of 60 min. The o-DCB removal rate and adsorption time curve was drawn, and the time (T) required for the o-DCB removal rate to reach 90% was calculated according to the curve to characterize the adsorption and removal efficiency of the adsorbent for organic pollutants. The shorter the time, the more efficient the removal of organic pollution. The results are shown in Table 5.

[0049] Table 5. Performance test results

[0050] From the data in the above table, it can be seen that the adsorbent prepared by the method of the present invention using fly ash, biomass straw and fruit peel as raw materials and using the secondary water washing liquid and secondary acid washing liquid treated with fly ash as the main treatment agent has a good adsorption and removal effect on heavy metal lead and dioxin in flue gas, wherein the removal rate of dioxin can reach more than 85%, and the removal rate of lead can reach more than 90%. At the same time, in the adsorption test of the chlorinated aromatic model compound o-DCB, compared with the adsorbent of the control example, the adsorbent of each embodiment can remove 90% of o-DCB in a shorter time, and has a higher removal efficiency for organic pollutants in flue gas.

[0051] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing an adsorbent using fly ash, characterized in that: Including the following processes: S1. Washing, acid washing and drying the waste incineration fly ash in sequence to obtain pre-treated fly ash for standby use; during the pre-treatment process, the water washing step and the acid washing step are repeated at least once, and the secondary water washing liquid of the water washing step and the secondary acid washing liquid of the acid washing step are collected for standby use; S2, uniformly mixing 15-20wt% of biostraw, 25-35wt% of peel and the remainder of the pretreated fly ash obtained in step S1 to obtain a mixed material; S3, using the secondary water washing liquid collected in step S1 to immerse the mixed material obtained in step S2, the solid-liquid ratio of the immersion treatment is 0.2-0.5kg / L, the immersion time is 2-3h, and the mixture is filtered and dried to obtain modified material A; S4, mixing the secondary pickling liquid collected in step S1 with anhydrous ethanol in a volume ratio of (2.4-3):1 to obtain a modified acid solution; impregnating the modified material A obtained in step S3 with the modified acid solution, wherein the solid-liquid ratio of the impregnation treatment is 0.2-0.4 kg / L, the immersion time is 1.5-2 h, and filtering and drying are performed to obtain a modified material B; S5. Screening the modified material B obtained in step S4 to obtain an adsorbent.

2. The method for preparing an adsorbent using fly ash according to claim 1, characterized in that: In the S3 and S4 steps, during the immersion treatment, stirring is performed at a speed of 150-200 r / min for 3 min every 0.5 h.

3. The method for preparing an adsorbent using fly ash according to claim 1, characterized in that: In the S5 step, the product is sieved through a 200-mesh sieve.

4. The method for preparing an adsorbent using fly ash according to claim 1, characterized in that: The bio-straw and fruit peels come from existing domestic waste from waste-to-energy plants.

5. The method for preparing an adsorbent using fly ash according to claim 1, characterized in that: In step S1, the pH of the collected secondary washing liquid is ≥12.

6. The method for preparing an adsorbent using fly ash according to claim 5, characterized in that: In the S1 process, the solid-liquid ratio of water washing is 0.8-1.2 kg / L.

7. The method for preparing an adsorbent using fly ash according to claim 1, characterized in that: In the S1 process, the waste incineration fly ash is acid washed with hydrochloric acid having a concentration of 0.5-0.8 mol / L.

8. The method for preparing an adsorbent using fly ash according to claim 7, characterized in that: In the S1 process, the pickling solid-liquid ratio is 0.4-0.6 kg / L.

9. An adsorbent prepared by the adsorbent preparation method according to any one of claims 1 to 8.

10. Use of the adsorbent prepared by the method of any one of claims 1 to 8 or the adsorbent according to claim 9 in the purification of flue gas from waste incineration.

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