A method for preparing an adsorbent from fly ash, the adsorbent and its application in waste incineration flue gas purification

Abstract

The application relates to the field of resource utilization of waste incineration fly ash, and specifically 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 from the fly ash comprises a fly ash pretreatment process, a mixing process, a secondary water washing liquid modification process, a secondary acid washing liquid modification process and a screening process, wherein the mixing process takes biological straw, fruit peels and pretreated fly ash as raw materials; the secondary water washing liquid modification process and the secondary acid washing liquid modification process respectively take secondary water washing liquid and secondary acid washing liquid collected in the fly ash pretreatment process as treating agents; the prepared adsorbent has excellent adsorption and removal effect on heavy metal lead and dioxin in flue gas, realizes resource utilization of fly ash, straw and fruit peel garbage, solves the disposal problem of the corresponding garbage, helps to realize fly ash zero discharge of a waste incineration power plant, reduces landfill disposal of fly ash and saves land resources.

Description

Technical Field

[0001] This application relates to the field of resource utilization of fly ash from waste incineration, and more specifically, it relates 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 Technology

[0002] Fly ash from waste incineration is a secondary pollutant produced after waste incineration, accounting for approximately 3% to 5% of the total waste incineration volume. It contains a large amount of easily leached heavy metals and is classified as hazardous waste. Simultaneously, the flue gas generated during waste incineration contains heavy metals such as lead and organic pollutants such as dioxins, which can easily cause secondary pollution.

[0003] Among the relevant technologies for fly ash disposal, solidification / stabilization-landfill technology is 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 good solidification and dioxin removal effects for most heavy metals, but its energy consumption is high. Cement kiln co-processing technology can effectively remove dioxins and solidify more than 99% of the heavy metals in fly ash, but it requires additional fly ash pretreatment processes and concentrated saline wastewater treatment facilities before entering the kiln, resulting in high investment costs.

[0004] Therefore, fly ash disposal generally suffers from problems such as high cost, high energy consumption, and serious secondary pollution, and there is an urgent need to find an effective way to both treat fly ash and save land resources. Summary of the Invention

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

[0006] In a first aspect, this application provides a method for preparing an adsorbent using fly ash, employing the following technical solution:

[0007] A method for preparing an adsorbent using fly ash includes the following steps:

[0008] S1. The fly ash from waste incineration is sequentially washed with water, acid-washed, and dried to obtain pretreated fly ash for later use. During the pretreatment process, the water washing step and the acid washing step are repeated at least once, and the secondary water washing liquid from the water washing step and the secondary acid washing liquid from the acid washing step are collected for later use.

[0009] S2. Mix 15-20 wt% of biological straw, 25-35 wt% of fruit peel and the remainder of pretreated fly ash obtained in step S1 evenly to obtain a mixture.

[0010] S3. The mixture obtained in step S2 is impregnated with the secondary washing liquid collected in step S1. The solid-liquid ratio of the impregnation treatment is 0.2-0.5 kg / L, the soaking time is 2-3 h, and the mixture is filtered and dried to obtain modified material A.

[0011] S4. Mix the secondary pickling solution collected in step S1 with anhydrous ethanol at a volume ratio of (2.4-3):1 to obtain a modified acid solution; use the modified acid solution to impregnate the modified material A obtained in step S3, with a solid-liquid ratio of 0.2-0.4 kg / L and an impregnation time of 1.5-2 h, then filter and dry to obtain modified material B;

[0012] The modified material B obtained from the S5 and S4 screening processes is the adsorbent.

[0013] By adopting the above technical solution:

[0014] 1. Due to the strong alkalinity and high hardness of fly ash itself, the washing solution and acid washing solution contain high concentrations of NaOH solution and CaCl2 solution, respectively. These are used to treat fly ash and biological matrix, and to modify them. New hydroxyl functional groups can be introduced, and the stability and surface porous structure of the adsorbent can be increased, thereby enhancing the adsorption effect.

[0015] 2. Using fly ash from waste incineration, bio-straw, and fruit peels as raw materials for making adsorbents can simultaneously solve the disposal problems of these industrial wastes (fly ash) and domestic wastes (bio-straw and fruit peels), realizing resource reuse. The raw materials used in the adsorbent preparation process and the equipment or devices used in other processes can be selected from the existing plant area, which has low energy consumption, less additional investment, and features simple process, low processing cost, and small footprint.

[0016] 3. During the modification process, fly ash, straw and fruit peel are treated with water washing solution and acid washing solution respectively. Only a small amount of anhydrous ethanol is added, and no additional reagents are added, which saves reagent costs. Moreover, the raw materials are readily available, which is an economical and feasible way to utilize fly ash resources.

[0017] 4. The prepared adsorbent has good adsorption and removal effects on heavy metals and dioxins, and can be reused in the incinerator for incineration power generation after reaching the adsorption capacity, thus achieving zero emission of fly ash from the waste incineration power plant.

[0018] Furthermore, in steps S3 and S4, during the impregnation process, the mixture is stirred for 3 minutes at a speed of 150-200 r / min every 0.5 hours.

[0019] Furthermore, in the S5 process, the gas is passed through a 200-mesh sieve. This increases the specific surface area of ​​the adsorbent, which is beneficial for adsorbing and removing pollutants from the flue gas.

[0020] Furthermore, in the S2 process, the biological straw and fruit peels are crushed and sieved through a 100-mesh screen.

[0021] Furthermore, the bio-stalks and fruit peels are derived from existing municipal solid waste from the waste-to-energy plant. Using municipal solid waste as raw material is low-cost and solves the problem of municipal solid waste disposal within the plant area.

[0022] 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.

[0023] Furthermore, in the S1 process, the pH of the collected secondary washing solution is ≥12.

[0024] Furthermore, in the S1 process, the solid-liquid ratio of water washing is 0.8-1.2 kg / L.

[0025] Furthermore, in the S1 process, the stirring speed during the water washing process is 150-200 r / min, and the stirring is continued for 30-45 min.

[0026] Furthermore, in the S1 process, recycled water is used to wash the fly ash from the waste incineration. The recycled water is obtained from treated domestic sewage and meets the standard of "Urban Wastewater Reuse - Industrial Water" (GB / T19923-2024).

[0027] Furthermore, in the S1 process, the fly ash from waste incineration is acid-washed with hydrochloric acid at a concentration of 0.5-0.8 mol / L.

[0028] Furthermore, in the S1 process, the pickling solid-liquid ratio is 0.4-0.6 kg / L.

[0029] Furthermore, during the pickling process, the stirring speed is 100-150 r / min, and the stirring is continued for 20-30 min.

[0030] Secondly, this application provides an adsorbent prepared by any of the aforementioned adsorbent preparation methods. Further, the adsorbent exhibits an adsorption rate of ≥90% for lead in flue gas and a removal rate of ≥85% for dioxins. This adsorbent demonstrates excellent adsorption performance, achieving "waste-to-waste treatment." After reaching its adsorption capacity, the adsorbent can be collected as ash through a dust removal system. Due to its high carbon content, it has certain recycling value and can be reused in an incinerator for incineration power generation, achieving zero emissions of fly ash from waste-to-energy plants. This reduces subsequent fly ash reduction and harmless treatment processes, lowers the amount of fly ash going to landfills, and helps alleviate land resource constraints.

[0031] Thirdly, this application provides an application of the aforementioned adsorbent in the purification of flue gas from waste incineration. Attached Figure Description

[0032] Figure 1 The diagram below shows the process flow for preparing the adsorbent in this embodiment. Detailed Implementation

[0033] To enable those skilled in the art to better understand the technical solutions of this invention, the present application will be further described in detail below with reference to the accompanying drawings.

[0034] [Example 1]

[0035] A method for preparing an adsorbent, referring to Figure 1 The specific procedures are as follows:

[0036] S1 fly ash pretreatment process:

[0037] First, the fly ash from the waste-to-energy plant is washed once with recycled water at a solid-liquid ratio of 0.8 kg / L. The stirring speed during the washing process is 200 rpm for 30 minutes. The recycled water used is obtained from treated domestic sewage and meets the standard of "Urban Wastewater Reuse - Industrial Water" (GB / T19923-2024). After the first wash, the mixture is filtered, and the filtrate is used for a second wash. The stirring speed during this second wash is 200 rpm for 30 minutes. The filtrate obtained from the filtration is the second wash solution, with a pH ≥ 12, and is temporarily stored for later use. The filtrate is the washed fly ash.

[0038] Then, the water-washed fly ash obtained in the previous step was subjected to a first acid wash with 0.8 mol / L hydrochloric acid at a solid-liquid ratio of 0.4 kg / L. The stirring speed during the acid wash was 150 r / min, and the stirring was continued for 20 min. After the first acid wash, the mixture was filtered, and the filtrate was used to perform a second acid wash with the filtrate. The stirring speed during the second acid wash was 150 r / min, and the stirring was continued for 20 min. The filtrate obtained after filtration was the second acid wash solution, which was temporarily stored for later use; the filtrate was the acid-washed fly ash.

[0039] Finally, the pre-drying step yields acid-washed fly ash, which is then used as a raw material for producing adsorbents.

[0040] S2 Raw Material Mixing Process:

[0041] Biological straw and fruit peels are separated from municipal solid waste in a waste-to-energy plant, crushed, and sieved through a 100-mesh sieve to obtain raw materials for later use. The types of biological straw and fruit peels are not limited. Biological straw includes at least one of corn stalks, wheat stalks, rice stalks, cotton stalks, and sorghum stalks. Fruit peels include 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 municipal solid waste. The biological straw, fruit peels, and pretreated fly ash obtained from process S1 are mixed evenly at a ratio of 20 wt% biological straw, 35 wt% fruit peels, and 45 wt% pretreated fly ash to obtain a mixture.

[0042] S3 secondary washing solution modification process:

[0043] The mixture obtained from step S2 was impregnated with the secondary washing liquid collected in step S1. The solid-liquid ratio of the impregnation treatment was 0.2 kg / L, the soaking time was 3 h, and the mixture was stirred at 200 r / min for 3 min every 0.5 h during the impregnation treatment. After filtration and drying, modified material A was obtained.

[0044] S4 secondary pickling solution modification process:

[0045] First, the secondary pickling solution collected in step S1 and anhydrous ethanol are mixed in a volume ratio of 2.4:1 to obtain a modified acid solution. Then, the modified material A obtained in step S3 is impregnated with the modified acid solution. The solid-liquid ratio of the impregnation treatment is 0.2 kg / L, the soaking time is 2 h, and the mixture is stirred at a speed of 200 r / min for 3 min every 0.5 h during the impregnation treatment. After filtration and drying, modified material B is obtained.

[0046] S5 sieving process: Modified material B obtained from the S4 process is passed through a 200-mesh sieve, which yields an adsorbent with a mesh size ≤ 200.

[0047] [Examples 2-3]

[0048] Examples 2-3 are all based on Example 1, with the only difference being that the process parameters of the S1 fly ash pretreatment process are different, as shown in Table 1.

[0049] Table 1. Process parameters for fly ash pretreatment process

[0050]

[0051] In Examples 2-3, adsorbents with a mesh size ≤200 were prepared.

[0052] [Examples 4-8]

[0053] Examples 4-8 are all based on Example 2, with the only difference being that the mixing ratio of bio-straw, fruit peel and pretreated fly ash is different in the raw material mixing process of S2, as shown in Table 2.

[0054] Table 2. Mixture Proportioning Table (by weight percentage)

[0055]

[0056] Adsorbents with a mesh size ≤200 were prepared in Examples 4-8.

[0057] [Examples 9-10]

[0058] Examples 9-10 are all based on Example 2, with the only difference being the process parameters of the secondary washing solution modification process in S3, as shown in Table 3.

[0059] Table 3. Process parameters for modification of secondary washing solution

[0060]

[0061] In Examples 9-10, adsorbents with a mesh size ≤200 were prepared.

[0062] [Examples 11-14]

[0063] Examples 11-14 are all based on Example 10, with the only difference being the process parameters of the secondary pickling solution modification process in S4, as shown in Table 4.

[0064] Table 4. Process parameters for modification of secondary pickling solution

[0065]

[0066] In Examples 11-14, adsorbents with a mesh size ≤200 were prepared.

[0067] [Compare with Example 1]

[0068] Comparative Example 1 is based on Example 1, except that in the raw material mixing process of S2, an equal amount of biological straw is used instead of fruit peel.

[0069] [Compare with Example 2]

[0070] Comparative Example 2 is based on Example 1, except that in the raw material mixing process S2, an equal amount of fruit peel is used instead of biological straw.

[0071] [Performance Testing]

[0072] Experiment 1: The adsorbents of each example / control example were used as samples to adsorb and treat the flue gas from waste incineration at 52°C. The mass-volume ratio of adsorbent to flue gas was 20 g / L. The concentrations of lead (Pb) and dioxins (PCDD / Fs) in the flue gas before and after treatment were tested, and the corresponding removal rates were calculated. The results are shown in Table 5.

[0073] Experiment 2: Adsorption and Removal Efficiency Test of Organic Pollutants. Using the chlorinated aromatic hydrocarbon model compound o-DCB as a representative organic pollutant, 80 mg of adsorbent was packed into a stainless steel adsorption bed (inner diameter: 5 mm), with quartz wool pads at both ends. A fixed-bed adsorption-online detection system was used to evaluate the adsorption and removal performance of o-DCB from the gas phase in each example / control example. The adsorbed o-DCB was detected by GC-FID, and the o-DCB removal rate was calculated. Adsorption conditions: total gas flow rate 60 mL / min, O2 content 5%, o-DCB concentration 150 ppm, adsorbent mass 80 mg, adsorption temperature 50℃, and adsorption time 60 min. An o-DCB removal rate versus adsorption time curve was plotted. The time (T) required for the o-DCB removal rate to reach 90% was calculated based on the curve, thus characterizing the adsorption and removal efficiency of the adsorbent for organic pollutants. A shorter time indicates higher efficiency in removing organic pollutants. Specific results are shown in Table 5.

[0074] Table 5. Performance Test Results

[0075]

[0076] The data in the table above shows that the adsorbent prepared according to the method of this invention, using fly ash, biological straw, and fruit peels as raw materials, and secondary washing liquid and secondary acid washing liquid from fly ash treatment as the main treatment agents, exhibits good adsorption and removal effects on heavy metals lead and dioxins in flue gas. The removal rate for dioxins can reach over 85%, and the removal rate for lead can reach over 90%. Furthermore, in the adsorption test of the chloroaromatic hydrocarbon model compound o-DCB, compared to the adsorbent in the control example, the adsorbents in each embodiment can remove 90% of o-DCB in a shorter time, demonstrating higher removal efficiency for organic pollutants in flue gas.

[0077] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for preparing an adsorbent, characterized in that, The process includes the following steps: S1. The fly ash from waste incineration is sequentially washed with water, acid-washed, and dried to obtain pretreated fly ash for later use. During the pretreatment process, the water washing step and the acid washing step are repeated at least once, and the secondary water washing solution from the water washing step and the secondary acid washing solution from the acid washing step are collected for later use. In step S1, the fly ash from waste incineration is acid-washed with hydrochloric acid with a concentration of 0.5-0.8 mol / L, and the pH of the collected secondary water washing solution is ≥12. S2. Mix 15-20 wt% of biological straw, 25-35 wt% of fruit peel and the remainder of pretreated fly ash obtained in step S1 evenly to obtain a mixture. S3. The mixture obtained in step S2 is impregnated with the secondary washing liquid collected in step S1. The solid-liquid ratio of the impregnation treatment is 0.2-0.5 kg / L, the soaking time is 2-3 h, and the mixture is filtered and dried to obtain modified material A. S4. Mix the secondary pickling solution collected in step S1 with anhydrous ethanol at a volume ratio of (2.4-3):1 to obtain a modified acid solution; use the modified acid solution to impregnate the modified material A obtained in step S3, with a solid-liquid ratio of 0.2-0.4 kg / L and an impregnation time of 1.5-2 h, then filter and dry to obtain modified material B; The modified material B obtained from the S5 and S4 screening processes is the adsorbent.

2. The method for preparing an adsorbent according to claim 1, characterized in that: In processes S3 and S4, during the impregnation treatment, the mixture is stirred for 3 minutes at a speed of 150-200 r / min every 0.5 hours.

3. The method for preparing an adsorbent according to claim 1, characterized in that: In the S5 process, the sample is passed through a 200-mesh sieve.

4. The method for preparing an adsorbent according to claim 1, characterized in that: The bio-stalks and fruit peels are derived from existing municipal solid waste from waste-to-energy plants.

5. The method for preparing an adsorbent according to claim 1, characterized in that: In the S1 process, the solid-liquid ratio of water washing is 0.8-1.2 kg / L.

6. The method for preparing an adsorbent according to claim 1, characterized in that: In the S1 process, the pickling solid-liquid ratio is 0.4-0.6 kg / L.

7. An adsorbent prepared by the adsorbent preparation method according to any one of claims 1-6.

8. The application of the adsorbent prepared by any one of the adsorbent preparation methods of claims 1-6, or the adsorbent of claim 7, in the purification of flue gas from waste incineration.

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