Hydrochloric acid modified fly ash assisted by wet desulfurization wastewater and preparation method and application thereof

Abstract

The application discloses hydrochloric acid modified fly ash assisted with wet desulfurization wastewater and a preparation method and application thereof. The preparation method comprises the following steps: preparing a hydrochloric acid solution with a certain concentration by using wet desulfurization wastewater; adding fly ash into the prepared hydrochloric acid solution and heating to react; and filtering and drying after the reaction to obtain the hydrochloric acid modified fly ash. The application adopts a hydrochloric acid thermal activation mode, uses hydrochloric acid as an activator, simultaneously modifies the fly ash by using sufficient halogen atoms in the wet desulfurization wastewater, changes the microstructure of the fly ash and incorporates a small amount of chlorine elements. The preparation method has the advantages of simple operation, simple process, low cost and good practical application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental protection, and particularly relates to hydrochloric acid modified fly ash assisted by wet desulfurization wastewater and a preparation method and application thereof. BACKGROUND

[0002] The causes of mercury pollution mainly include natural release and human pollution, and the human source is a very important factor. The human source of mercury is mainly related to the following aspects: mercury mines and metal smelting, industrial production and use in the electrical industry, and natural fossil fuel combustion. During the coal combustion process, most of the mercury will separate into the atmosphere with the flue gas, and elemental mercury is the main form of mercury in the environment, which has high volatility and low water solubility. Due to easy evaporation at room temperature and long-distance transportation in the atmosphere, it is easy to cause global pollution. In view of the mercury pollution problem generated in the coal combustion process of coal-fired power plants, currently several control methods are mainly proposed, including adsorbent injection method, fixed bed filtration method, and wet flue gas desulfurization combined with mercury removal. However, due to the high cost of the adsorbent, it is urgent to develop a new type of high-efficiency and low-cost adsorbent, the oxidation efficiency of mercury is not high, and there is a possibility of secondary pollution, so it is particularly important to develop a new type of efficient and green desulfurization technology. SUMMARY

[0003] The purpose of the present application is to provide a hydrochloric acid modified fly ash assisted by wet desulfurization wastewater and a preparation method and application thereof.

[0004] The present application explores the conditions for preparing hydrochloric acid modified fly ash from wet desulfurization wastewater, in order to provide application reference for mercury removal of fly ash modified by hydrochloric acid, and to reduce the discharge of wastewater by absorbing wet desulfurization wastewater of coal-fired power plants.

[0005] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0006] The present application provides a preparation method of hydrochloric acid modified fly ash assisted by wet desulfurization wastewater, wherein the preparation method comprises the following steps:

[0007] A hydrochloric acid solution with a certain concentration is prepared by using wet desulfurization wastewater;

[0008] The fly ash is added to the prepared hydrochloric acid solution and heated for reaction;

[0009] After the reaction is completed, filtration and drying are performed to obtain the hydrochloric acid modified fly ash.

[0010] In some preferred embodiments of the present application, the fly ash is pretreated as follows: the fly ash is dried and sieved through a 400-mesh screen.

[0011] In some preferred embodiments of the present application, the concentration of the hydrochloric acid solution is 0.1-5 mol / L, more preferably 0.6 mol / L.

[0012] In some preferred embodiments of the present application, the heating temperature is 20-100℃, preferably 40℃.

[0013] In some preferred embodiments of the present application, the heating is performed with stirring, and the stirring speed is 400 r / min.

[0014] In some preferred embodiments of the present application, the reaction time is 6-24 h, preferably 12 h.

[0015] In some preferred embodiments of the present application, the drying temperature is 40-80℃, and the time is determined according to the drying purpose.

[0016] Another aspect of the present application provides a hydrochloric acid modified fly ash obtained by any of the above preparation methods.

[0017] The hydrochloric acid modified fly ash prepared by the present application has a larger specific surface area and more small slit pores, the specific surface area increases from 11.51 m 2 / g to 28.9 m 2 / g, and the average pore size decreases from 27.39 nm to 16.04 nm.

[0018] Still another aspect of the present application provides an application of the above hydrochloric acid modified fly ash in gaseous mercury adsorption.

[0019] The present application uses hydrochloric acid heat activation, uses hydrochloric acid as an activator, and simultaneously uses sufficient halogen atoms in wet desulfurization wastewater to modify the fly ash, changes the microstructure of the fly ash, and incorporates a small amount of chlorine element. The preparation method has the advantages of simple operation, simple process, and low cost, and has good practical application value.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] 1) The method for modifying fly ash with hydrochloric acid used in the present application can increase the specific surface area of the fly ash and improve the pore structure through simple experimental means, thereby obtaining better adsorption performance for gaseous mercury.

[0022] 2) The fly ash is modified by adding wet desulfurization wastewater and hydrochloric acid, so that the fly ash retains part of the chlorine element and the structural characteristics are changed.

[0023] 3) The hydrochloric acid modified fly ash prepared by the present application has a much greater adsorption capacity for mercury than the original fly ash, and the modification method is simple in operation, simple in process, and low in cost, and at the same time, the wet desulfurization wastewater is disposed of, reducing the environmental impact of wastewater discharge. Attached Figure Description

[0024] Figure 1 This is a SEM image of the hydrochloric acid-modified fly ash obtained in Example 9.

[0025] Figure 2 This is the BET diagram of the hydrochloric acid-modified fly ash obtained in Example 9.

[0026] Figure 3 This is a pore size distribution diagram of the hydrochloric acid-modified fly ash obtained in Example 9.

[0027] Figure 4 This is a fine XPS image of Cl 2p of the hydrochloric acid-modified fly ash obtained in Example 9.

[0028] Figure 5 This is a SEM image of the fly ash obtained in Comparative Example 1.

[0029] Figure 6 This is the BET diagram of the fly ash obtained in Comparative Example 1.

[0030] Figure 7 This is a pore size distribution diagram of the fly ash obtained in Comparative Example 1.

[0031] Figure 8 This is a fine XPS plot of Cl 2p of fly ash obtained in Comparative Example 1. Detailed Implementation

[0032] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0033] All numerical specifications in this invention (e.g., temperature, time, concentration, and weight, including ranges for each) are generally approximate values ​​that may be changed (+) or (-) in increments of 0.1 or 1.0. All numerical specifications are to be understood as being preceded by the term "about".

[0034] Example 1

[0035] This embodiment uses wet desulfurization wastewater to prepare hydrochloric acid-modified fly ash, including the following steps:

[0036] 1) Prepare 10 mL of 0.5 mol / L hydrochloric acid solution using wet desulfurization wastewater. The amount of wet desulfurization wastewater used is 5 mL, and the remainder is deionized water.

[0037] 2) Take 1g of fly ash that has passed through a 400-mesh sieve and disperse it in the prepared hydrochloric acid aqueous solution. Stir at room temperature for 6 hours. Filter the solution after the reaction to obtain gray powder. Wash it several times with deionized water and dry it at 50℃ for 12 hours.

[0038] Example 2

[0039] This example is assisted by wet desulfurization wastewater to prepare hydrochloric acid modified fly ash, including the following steps:

[0040] 1) using wet desulfurization wastewater to prepare 10 mL of 0.5 mol / L hydrochloric acid aqueous solution, wet desulfurization wastewater dosage 5 mL.

[0041] 2) take the fly ash 1 g through 400 mesh sieve and disperse into the prepared hydrochloric acid aqueous solution, stirring at room temperature for 12 h, filtering the reacted solution to obtain gray powder, washing with deionized water for several times, and drying at 50℃ for 12 h.

[0042] Example 3

[0043] This example is assisted by wet desulfurization wastewater to prepare hydrochloric acid modified fly ash, including the following steps:

[0044] 1) using wet desulfurization wastewater to prepare 10 mL of 0.5 mol / L hydrochloric acid aqueous solution, wet desulfurization wastewater dosage 5 mL, and the rest is deionized water.

[0045] 2) take the fly ash 1 g through 400 mesh sieve and disperse into the prepared hydrochloric acid aqueous solution, stirring at room temperature for 24 h, filtering the reacted solution to obtain gray powder, washing with deionized water for several times, and drying at 50℃ for 12 h.

[0046] Example 4

[0047] This example is assisted by wet desulfurization wastewater to prepare hydrochloric acid modified fly ash, including the following steps:

[0048] 1) using wet desulfurization wastewater to prepare 10 mL of 0.5 mol / L hydrochloric acid aqueous solution, wet desulfurization wastewater dosage 5 mL, and the rest is deionized water.

[0049] 2) take the fly ash 1 g through 400 mesh sieve and disperse into the prepared hydrochloric acid aqueous solution, heating and stirring at 20℃ for 12 h, filtering the reacted solution to obtain gray powder, washing with deionized water for several times, and drying at 50℃ for 12 h.

[0050] Example 5

[0051] This example is assisted by wet desulfurization wastewater to prepare hydrochloric acid modified fly ash, including the following steps:

[0052] 1) using wet desulfurization wastewater to prepare 10 mL of 0.5 mol / L hydrochloric acid aqueous solution, wet desulfurization wastewater dosage 5 mL, and the rest is deionized water.

[0053] 2) Take the fly ash 1 g through 400 mesh sieve, disperse into the prepared hydrochloric acid aqueous solution, heat and stir for 12 h under the condition of 40 ℃, filter the reacted solution to obtain a gray powder, wash with deionized water for multiple times, and dry at 50 ℃ for 12 h.

[0054] Example 6

[0055] The hydrochloric acid modified fly ash is prepared with the aid of wet desulfurization wastewater in this example, including the following steps:

[0056] 1) Prepare 10 mL of 0.5 mol / L hydrochloric acid aqueous solution using wet desulfurization wastewater, the amount of wet desulfurization wastewater is 5 mL, and the rest is deionized water.

[0057] 2) Take the fly ash 1 g through 400 mesh sieve, disperse into the prepared hydrochloric acid aqueous solution, heat and stir for 12 h under the condition of 100 ℃, filter the reacted solution to obtain a gray powder, wash with deionized water for multiple times, and dry at 50 ℃ for 12 h.

[0058] Example 7

[0059] The hydrochloric acid modified fly ash is prepared with the aid of wet desulfurization wastewater in this example, including the following steps:

[0060] 1) Prepare 10 mL of 0.1 mol / L hydrochloric acid aqueous solution using wet desulfurization wastewater, the amount of wet desulfurization wastewater is 5 mL, and the rest is deionized water.

[0061] 2) Take the fly ash 1 g through 400 mesh sieve, disperse into the prepared hydrochloric acid aqueous solution, heat and stir for 12 h under the condition of 40 ℃, filter the reacted solution to obtain a gray powder, wash with deionized water for multiple times, and dry at 50 ℃ for 12 h.

[0062] Example 8

[0063] The hydrochloric acid modified fly ash is prepared with the aid of wet desulfurization wastewater in this example, including the following steps:

[0064] 1) Prepare 10 mL of 0.3 mol / L hydrochloric acid aqueous solution using wet desulfurization wastewater, the amount of wet desulfurization wastewater is 5 mL, and the rest is deionized water.

[0065] 2) Take the fly ash 1 g through 400 mesh sieve, disperse into the prepared hydrochloric acid aqueous solution, heat and stir for 12 h under the condition of 40 ℃, filter the reacted solution to obtain a gray powder, wash with deionized water for multiple times, and dry at 50 ℃ for 12 h.

[0066] Example 9

[0067] The hydrochloric acid modified fly ash is prepared with the aid of wet desulfurization wastewater in this example, including the following steps:

[0068] 1) Prepare 10 mL of 0.6 mol / L hydrochloric acid solution using wet desulfurization wastewater. The amount of wet desulfurization wastewater used is 5 mL, and the remainder is deionized water.

[0069] 2) Take 1g of fly ash that has passed through a 400-mesh sieve and disperse it in the prepared hydrochloric acid aqueous solution. Heat and stir at 40°C for 12 hours. Filter the solution after the reaction to obtain gray powder. Wash it several times with deionized water and dry it at 50°C for 12 hours.

[0070] Example 10

[0071] This embodiment uses wet desulfurization wastewater to prepare hydrochloric acid-modified fly ash, including the following steps:

[0072] 1) Prepare 10 mL of 1 mol / L hydrochloric acid solution using wet desulfurization wastewater. The amount of wet desulfurization wastewater used is 5 mL, and the remainder is deionized water.

[0073] 2) Take 1g of fly ash that has passed through a 400-mesh sieve and disperse it in the prepared hydrochloric acid aqueous solution. Heat and stir at 40°C for 12 hours. Filter the solution after the reaction to obtain gray powder. Wash it several times with deionized water and dry it at 50°C for 12 hours.

[0074] Example 11

[0075] This embodiment uses wet desulfurization wastewater to prepare hydrochloric acid-modified fly ash, including the following steps:

[0076] 1) Prepare 10 mL of 5 mol / L hydrochloric acid solution using wet desulfurization wastewater. The amount of wet desulfurization wastewater used is 5 mL, and the remainder is deionized water.

[0077] 2) Take 1g of fly ash that has passed through a 400-mesh sieve and disperse it in the prepared hydrochloric acid aqueous solution. Heat and stir at 40°C for 12 hours. Filter the solution after the reaction to obtain gray powder. Wash it several times with deionized water and dry it at 50°C for 12 hours.

[0078] Example 12

[0079] This embodiment uses wet desulfurization wastewater to prepare hydrochloric acid-modified fly ash, including the following steps:

[0080] 1) Prepare 10 mL of 0.6 mol / L hydrochloric acid solution using wet desulfurization wastewater. The amount of wet desulfurization wastewater used is 3 mL, and the remainder is deionized water.

[0081] 2) Take 1g of fly ash that has passed through a 400-mesh sieve and disperse it in the prepared hydrochloric acid aqueous solution. Heat and stir at 40°C for 12 hours. Filter the solution after the reaction to obtain gray powder. Wash it several times with deionized water and dry it at 50°C for 12 hours.

[0082] Example 13

[0083] This embodiment uses wet desulfurization wastewater to prepare hydrochloric acid-modified fly ash, including the following steps:

[0084] 1) Prepare 10 mL of 0.6 mol / L hydrochloric acid solution using wet desulfurization wastewater. The volume of wet desulfurization wastewater is 8 mL, and the remainder is deionized water.

[0085] 2) Take 1g of fly ash that has passed through a 400-mesh sieve and disperse it in the prepared hydrochloric acid aqueous solution. Heat and stir at 40°C for 12 hours. Filter the solution after the reaction to obtain gray powder. Wash it several times with deionized water and dry it at 50°C for 12 hours.

[0086] Comparative Example 1

[0087] Use fly ash that has passed through a 400-mesh sieve.

[0088] Comparative Example 2

[0089] This embodiment uses wet desulfurization wastewater to prepare hydrochloric acid-modified fly ash, including the following steps:

[0090] 1) 10 mL of 0.6 mol / L hydrochloric acid solution was prepared using deionized water, and wet desulfurization wastewater was not used.

[0091] 2) Take 1g of fly ash that has passed through a 400-mesh sieve and disperse it in the prepared hydrochloric acid aqueous solution. Heat and stir at 40°C for 12 hours. Filter the solution after the reaction to obtain gray powder. Wash it several times with deionized water and dry it at 50°C for 12 hours.

[0092] Mercury removal performance tests were conducted on a total of 15 samples from the above examples and comparative examples. The method involved generating a stable concentration of gaseous mercury using a mercury generator, then introducing a certain mass of powdered sample into the gas path. A Zeeman effect mercury analyzer was used to measure the concentration of gaseous mercury before and after sample introduction, and the adsorption efficiency was calculated. The operating conditions were: nitrogen carrier gas velocity of 60 L / h, and initial mercury concentration of 100–120 μg / m³. 3 The oxygen concentration is 6%, and the NO concentration is 100 mg / m³. 3 SO2 concentration is 500 mg / m³ 3 The amount of adsorbent used was 0.1 g, and the reaction temperature was 200℃. Table 1 below shows the experimental results of mercury adsorption in the above samples.

[0093] As shown in Table 1, compared with Examples 1-3, the mercury removal efficiency was optimal when the activation treatment time was 12 h. Compared with Examples 4-6, the mercury removal efficiency was optimal when the activation temperature was 40℃. Compared with Examples 2 and 7-11, under the same conditions, the best effect was achieved when the hydrochloric acid concentration was 0.6 mol / L. Compared with Examples 9, 12-13 and Comparative Example 2, the mercury removal efficiency was optimal when the volume of desulfurization wastewater used for acid production was 5 mL; the desulfurization wastewater contained a large amount of soluble salts, among which Cl... - F - sulfate ions, Al 3+ The main components are sulfite ions, with Cl- ions playing an effective role. - F - The function and Cl in hydrochloric acid - They serve a similar purpose.

[0094] Table 1 Mercury removal efficiency of fly ash modified under different modification conditions

[0095] Sample treatment conditions Mercury removal efficiency Example 1 Fly ash stirred in 0.5 mol / L hydrochloric acid at room temperature for 6 h, wastewater dosage 5 mL 40.37％ Example 2 Fly ash stirred in 0.5 mol / L hydrochloric acid at room temperature for 12 h, wastewater dosage 5 mL 47.26％ Example 3 Fly ash stirred in 0.5 mol / L hydrochloric acid at room temperature for 24 h, wastewater dosage 5 mL 33.87％ Example 4 Fly ash stirred in 0.5 mol / L hydrochloric acid at 20°C for 12 h, wastewater dosage 5 mL 57.20％ Example 5 Fly ash stirred in 0.5 mol / L hydrochloric acid at 40°C for 12 h, wastewater dosage 5 mL 62.70％ Example 6 Fly ash stirred in 0.5 mol / L hydrochloric acid at 100°C for 12 h, wastewater dosage 5 mL 53.85％ Example 7 Fly ash stirred in 0.1 mol / L hydrochloric acid at 40°C for 12 h, wastewater dosage 5 mL 36.21％ Example 8 Fly ash stirred in 0.3 mol / L hydrochloric acid at 40°C for 12 h, wastewater dosage 5 mL 48.97％ Example 9 Fly ash stirred in 0.6 mol / L hydrochloric acid at 40°C for 12 h, wastewater dosage 5 mL 74.94％ Example 10 Fly ash stirred in 1 mol / L hydrochloric acid at 40°C for 12 h, wastewater dosage 5 mL 70.45％ Example 11 Fly ash stirred in 5 mol / L hydrochloric acid at 40°C for 12 h, wastewater dosage 5 mL 58.52％ Example 12 Fly ash stirred in 0.6 mol / L hydrochloric acid at 40°C for 12 h, wastewater dosage 3 mL 69.32％ Example 13 Fly ash stirred in 0.6 mol / L hydrochloric acid at 40°C for 12 h, wastewater dosage 8 mL 71.23％ Comparative Example 1 Fly ash not modified by hydrochloric acid 38.42％ Comparative Example 2 Fly ash stirred in 0.6 mol / L hydrochloric acid at 40°C for 12 h, wastewater dosage 0 mL 65.35％

[0096] By comparing the SEM images of Example 9 and Comparative Example 1 ( Figure 1 and Figure 5 As can be seen, its appearance changed after modification; hydrochloric acid modification caused the fly ash to appear as finer particles; compare the BET diagrams of Example 9 and Comparative Example 1. Figure 2 and Figure 6 It can be observed that the pore type is slit pore, but after modification with hydrochloric acid, its specific surface area is 2.5 times that before modification; compare the pore size distribution diagrams of Example 9 and Comparative Example 1 ( Figure 3 and Figure 7 The sample modified with hydrochloric acid had more pores <5nm; compare the fine XPS images of Cl 2p of Example 9 and Comparative Example 1 ( Figure 4 and Figure 8 As can be seen, a small amount of covalent chlorine is present in the sample after hydrochloric acid modification. Overall, hydrochloric acid modification resulted in a larger specific surface area for fly ash (from 11.51 m²). 2 / g increased to 28.9m 2 The finer pore structure (average pore size reduced from 27.39 nm to 16.04 nm) while retaining a small amount of chlorine resulted in a significant increase in mercury removal efficiency.

[0097] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing hydrochloric acid-modified fly ash supplemented with wet desulfurization wastewater, wherein, The preparation method includes the following steps: A hydrochloric acid solution of a certain concentration was prepared using wet desulfurization wastewater; Fly ash is added to a prepared hydrochloric acid solution and heated to carry out the reaction; After the reaction is complete, the mixture is filtered and dried to obtain the hydrochloric acid-modified fly ash.

2. The preparation method according to claim 1, wherein, The fly ash undergoes the following pretreatment: the fly ash is dried and then sieved through a 400-mesh sieve.

3. The preparation method according to claim 1, wherein, The concentration of the hydrochloric acid solution is 0.1–5 mol / L.

4. The preparation method according to claim 1, wherein, The concentration of the hydrochloric acid solution is 0.6 mol / L.

5. The preparation method according to claim 1, wherein, The heating temperature is 20–100°C.

6. The preparation method according to claim 1, wherein, The heating temperature is 40°C.

7. The preparation method according to claim 1, wherein, The reaction time is 6 to 24 hours.

8. The preparation method according to claim 1, wherein, The reaction time was 12 hours.

9. A hydrochloric acid-modified fly ash, obtained by the preparation method according to any one of claims 1-8.

10. The application of hydrochloric acid-modified fly ash as described in claim 9 in the adsorption of gaseous mercury.

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