Modified fly ash dechlorinating agent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of flue gas dechlorination, and discloses a modified fly ash dechlorinating agent as well as a preparation method and application thereof. The method comprises the following steps: (1) mixing fly ash and calcium carbonate to obtain a mixture; (2) carrying out mechanical ball milling on the mixture obtained in the step (1); wherein in the step (1), the total use amount of the fly ash and the calcium carbonate is 100 wt%, and the use amount of the calcium carbonate is 10-30 wt%; the average particle size of the calcium carbonate is 0.1-0.3 [mu] m. According to the method, the technological process is simple and efficient, meanwhile, the waste fly ash can be utilized to the maximum extent, resource utilization of the waste fly ash is achieved, and the cost is reduced; meanwhile, the modified fly ash dechlorinating agent prepared by the method has a good dechlorinating effect and low price, and has a good application prospect in the flue gas dechlorinating process of a coal-fired power plant.

Description

Technical Field

[0001] The invention relates to the technical field of flue gas dechlorination, and in particular to a modified fly ash dechlorination agent and a preparation method and application thereof. Background Art

[0002] Flue gas pollutants produced by coal-fired power plants include sulfur oxides, nitrogen oxides, carbon oxides, hydrogen chloride, heavy metals and fly ash. Sulfur oxides and nitrogen oxides have been well controlled through wet desulfurization and SCR. After the implementation of ultra-low emission standards for atmospheric pollutants in coal-fired power plants, the reduction and harmless treatment of desulfurization wastewater has become an environmental protection goal of zero emissions. Chlorine and its compounds produced by coal combustion are absorbed and enriched in the desulfurization slurry. However, too high a concentration of chloride ions will cause corrosion to the equipment, and will also cause the discharge of desulfurization wastewater and the high operating cost of desulfurization wastewater purification equipment. In addition, the chloride ions in the desulfurization slurry entering the desulfurization gypsum will also reduce the performance of the desulfurization gypsum. Therefore, after the implementation of ultra-low emission standards for coal-fired power plants, the reduction of desulfurization wastewater has become the primary technical problem to be solved. The most fundamental way to achieve wastewater reduction is to carry out flue gas dechlorination. The dechlorination agents currently used are mainly calcium-based or sodium-based adsorbents, such as calcium oxide and sodium hydroxide, but they have the problems of poor dechlorination effect and high cost, and will also have a certain impact on the reuse of fly ash.

[0003] In view of the above problems, finding a dechlorination agent with good dechlorination effect, low cost and little impact on fly ash performance has become an urgent problem to be solved. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of poor dechlorination effect and high cost in the prior art, and to provide a method for preparing a modified fly ash dechlorinating agent. The preparation process of the method is simple and efficient, and fly ash waste can be utilized at the same time, which is green, environmentally friendly and low in cost. The modified fly ash dechlorinating agent prepared by the method has good dechlorination effect and will not affect the performance of the fly ash.

[0005] In order to achieve the above object, the present invention provides a method for preparing a modified fly ash dechlorination agent, which comprises the following steps:

[0006] (1) mixing fly ash and calcium carbonate to obtain a mixture;

[0007] (2) subjecting the mixture obtained in step (1) to mechanical ball milling;

[0008] Wherein, in step (1), the total amount of fly ash and calcium carbonate is 100 weight %, and the amount of calcium carbonate is 10-30 weight %;

[0009] The average particle size of the calcium carbonate is 0.1-0.3 μm.

[0010] Preferably, in step (1), the fly ash contains one or more of unburned carbon, CaO, SiO2 and Al2O3.

[0011] Preferably, in step (2), the mechanical ball milling is carried out in the presence of ball milling beads.

[0012] Preferably, the ball milling beads include small ball milling beads and large ball milling beads, the particle size of the small ball milling beads is 4-6 mm, and the particle size of the large ball milling beads is 9-11 mm.

[0013] Preferably, in step (2), the weight ratio of the small ball milling beads to the large ball milling beads is 1-5:7.

[0014] Preferably, the weight ratio of the mixture to the ball milling beads is 1:5-10.

[0015] Preferably, in step (2), the conditions for mechanical ball milling include: a rotation speed of 400-600 rpm and a time of 30-60 min.

[0016] The second aspect of the present invention provides a modified fly ash dechlorination agent prepared by the above method.

[0017] Preferably, the average particle size of the modified fly ash dechlorination agent is less than 10 μm, and the specific surface area is 19.5-26 m 2 / g, pore volume is 0.03-0.05cm 3 / g.

[0018] The third aspect of the present invention provides the use of the modified fly ash dechlorination agent in the flue gas dechlorination process of a coal-fired power plant.

[0019] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0020] (1) The process flow of the method for preparing the modified fly ash dechlorinating agent of the present invention is simple and efficient, and at the same time, the waste fly ash can be utilized to the greatest extent, thereby realizing the resource utilization of the waste fly ash and reducing costs;

[0021] (2) The modified fly ash dechlorinating agent prepared by the method described in the present invention has good dechlorination effect and low price, and has good application prospects in the flue gas dechlorination process of coal-fired power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is an electron microscope image of the modified fly ash dechlorinating agent prepared in Example 1 of the present invention;

[0023] Figure 2 is an electron microscope image of the modified fly ash dechlorinating agent prepared in Example 2 of the present invention;

[0024] Figure 3 is an electron microscope image of the modified fly ash dechlorinating agent prepared in Example 3 of the present invention;

[0025] Figure 4 It is an electron microscope image of the modified fly ash dechlorinating agent prepared in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0026] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0027] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0028] The present invention provides a method for preparing a modified fly ash dechlorinating agent, the method comprising the following steps:

[0029] (1) mixing fly ash and calcium carbonate to obtain a mixture;

[0030] (2) subjecting the mixture obtained in step (1) to mechanical ball milling;

[0031] Wherein, in step (1), the total amount of fly ash and calcium carbonate is 100 weight %, and the amount of calcium carbonate is 10-30 weight %;

[0032] The average particle size of the calcium carbonate is 0.1-0.3 μm.

[0033] In the method described in the present invention, the mixture obtained by mixing fly ash and calcium carbonate is subjected to mechanical ball milling, which can not only reduce the average particle size of fly ash and calcium carbonate and increase the specific surface area, but also cause calcium carbonate and fly ash to react chemically so as to increase the active sites on the surface of fly ash. At the same time, with the total amount of fly ash and calcium carbonate being 100 weight percent, the amount of calcium carbonate is controlled to be 10-30 weight percent and the average particle size of calcium carbonate is 0.1-0.3 μm, so that the finally prepared modified fly ash dechlorination agent has good dechlorination effect and low cost.

[0034] In the method of the present invention, the "fly ash" refers to "fine solid particles in the flue gas ash generated by fuel combustion".

[0035] In a preferred embodiment, in step (1), the fly ash contains one or more of unburned carbon, CaO, SiO2 and Al2O3.

[0036] In a specific embodiment, in step (1), the total amount of fly ash and calcium carbonate is 100 weight%, and the amount of calcium carbonate can be 10 weight%, 15 weight%, 20 weight%, 25 weight% or 30 weight%.

[0037] In a preferred embodiment, in step (2), the mechanical ball milling is performed in the presence of ball milling beads.

[0038] In a more preferred embodiment, in order to improve the effect of mechanical ball milling, better reduce the specific surface area of ​​fly ash and calcium carbonate and complete the chemical modification of fly ash by calcium carbonate, the ball milling beads include small ball milling beads and large ball milling beads, the particle size of the small ball milling beads is 4-6 mm, and the particle size of the large ball milling beads is 9-11 mm.

[0039] In a more preferred embodiment, in order to further improve the effect of mechanical ball milling and improve the dechlorination effect of the modified fly ash dechlorination agent, in step (2), the weight ratio of the small ball milling beads to the large ball milling beads is 1-5:7; specifically, the weight ratio of the small ball milling beads to the large ball milling beads can be 1:7, 2:7, 3:7, 4:7 or 5:7.

[0040] In a preferred embodiment, in order to further improve the dechlorination effect of the modified fly ash dechlorination agent, the weight ratio of the mixture to the ball milling beads is 1:5-10; specifically, the weight ratio of the mixture to the ball milling beads can be 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10.

[0041] In a preferred embodiment, in step (2), the conditions of mechanical ball milling include: a rotation speed of 400-600 rpm and a time of 30-60 min; specifically, the rotation speed can be 400 rpm, 450 rpm, 500 rpm, 550 rpm or 600 rpm; and the time can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

[0042] The present invention also provides a modified fly ash dechlorinating agent prepared by the method.

[0043] The modified fly ash dechlorinating agent prepared by the above method not only has a good dechlorination effect, but also can greatly reduce the cost due to the resource utilization of waste fly ash, so that the prepared modified fly ash dechlorinating agent is low in price.

[0044] In a preferred embodiment, the modified fly ash dechlorination agent has an average particle size of <10 μm and a specific surface area of ​​19.5-26 m 2 / g, pore volume is 0.03-0.05cm 3 / g.

[0045] The present invention also provides application of the modified fly ash dechlorinating agent in the dechlorination process of flue gas in a coal-fired power plant.

[0046] The modified fly ash dechlorinating agent is used in the flue gas dechlorination process of coal-fired power plants and has an excellent low-temperature dechlorination effect at a temperature of 150-250°C.

[0047] The following examples further illustrate the modified fly ash dechlorination agent and its preparation method and application described in the present invention. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples.

[0048] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0049] Example 1

[0050] Preparation of modified fly ash dechlorinating agent S1:

[0051] (1) 18 g of fly ash and 2 g of calcium carbonate having an average particle size of 0.1 μm were mixed to obtain a mixture;

[0052] (2) The mixture obtained in step (1) was placed in a planetary ball mill at a rotation speed of 450 rpm and mechanically ball-milled for 30 min to obtain a modified fly ash dechlorination agent S1 (whose microscopic morphology is as follows: Figure 1 wherein the ball milling beads include 30 g of small ball milling beads with a diameter of 5 mm and 70 g of large ball milling beads with a diameter of 10 mm, that is, the weight ratio of the mixture to the ball milling beads in the planetary ball mill is 1:5.

[0053] Example 2

[0054] Preparation of modified fly ash dechlorinating agent S2:

[0055] (1) 16 g of fly ash and 4 g of calcium carbonate having an average particle size of 0.2 μm were mixed to obtain a mixture;

[0056] (2) The mixture obtained in step (1) was placed in a planetary ball mill with a rotation speed of 600 rpm and mechanically ball-milled for 30 min to obtain a modified fly ash dechlorination agent S2 (whose microscopic morphology is as follows: Figure 2 wherein the ball milling beads include 30 g of small ball milling beads with a diameter of 4 mm and 70 g of large ball milling beads with a diameter of 9 mm, that is, the weight ratio of the mixture to the ball milling beads in the planetary ball mill is 1:5.

[0057] Example 3

[0058] Preparation of modified fly ash dechlorinating agent S3:

[0059] (1) 14 g of fly ash and 6 g of calcium carbonate having an average particle size of 0.3 μm were mixed to obtain a mixture;

[0060] (2) The mixture obtained in step (1) was placed in a planetary ball mill at a rotation speed of 400 rpm and mechanically ball-milled for 60 min to obtain a modified fly ash dechlorination agent S3 (whose microscopic morphology is as follows: Figure 3 wherein the ball milling beads include 30 g of small ball milling beads with a diameter of 6 mm and 70 g of large ball milling beads with a diameter of 11 mm, that is, the weight ratio of the mixture to the ball milling beads in the planetary ball mill is 1:5.

[0061] Example 4

[0062] Preparation of modified fly ash dechlorinating agent S4:

[0063] (1) 18 g of fly ash and 2 g of calcium carbonate having an average particle size of 0.1 μm were mixed to obtain a mixture;

[0064] (2) The mixture obtained in step (1) is placed in a planetary ball mill at a rotation speed of 400 rpm and mechanically ball-milled for 60 min to obtain a modified fly ash dechlorination agent S4; wherein the ball milling beads include 60 g of small ball milling beads with a diameter of 5 mm and 140 g of large ball milling beads with a diameter of 10 mm, that is, the weight ratio of the mixture to the ball milling beads in the planetary ball mill is 1:10.

[0065] Example 5

[0066] Preparation of modified fly ash dechlorinating agent S5:

[0067] (1) 18 g of fly ash and 2 g of calcium carbonate having an average particle size of 0.1 μm were mixed to obtain a mixture;

[0068] (2) The mixture obtained in step (1) is placed in a planetary ball mill at a rotation speed of 450 rpm and mechanically ball-milled for 60 min to obtain a modified fly ash dechlorination agent S5; wherein the ball milling beads include 15 g of small ball milling beads with a diameter of 5 mm and 35 g of large ball milling beads with a diameter of 10 mm, that is, the weight ratio of the mixture to the ball milling beads in the planetary ball mill is 1:2.5.

[0069] Example 6

[0070] Preparation of modified fly ash dechlorinating agent S6:

[0071] (1) 18 g of fly ash and 2 g of calcium carbonate having an average particle size of 0.1 μm were mixed to obtain a mixture;

[0072] (2) The mixture obtained in step (1) is placed in a planetary ball mill at a rotation speed of 450 rpm and mechanically ball-milled for 60 min to obtain a modified fly ash dechlorination agent S6; wherein the ball milling beads include 50 g of small ball milling beads with a diameter of 5 mm and 50 g of large ball milling beads with a diameter of 10 mm, that is, the weight ratio of the mixture to the ball milling beads in the planetary ball mill is 1:5.

[0073] Comparative Example 1

[0074] Preparation of modified fly ash dechlorinating agent D1:

[0075] (1) 19 g of fly ash and 1 g of calcium carbonate having an average particle size of 0.1 μm were mixed to obtain a mixture;

[0076] (2) The mixture obtained in step (1) was placed in a planetary ball mill at a rotation speed of 450 rpm and mechanically ball-milled for 30 min to obtain a modified fly ash dechlorination agent D1; wherein the ball milling beads included 30 g of small ball milling beads with a diameter of 5 mm and 70 g of large ball milling beads with a diameter of 10 mm, that is, the weight ratio of the mixture to the ball milling beads in the planetary ball mill was 1:5.

[0077] Comparative Example 2

[0078] Preparation of modified fly ash dechlorinating agent D2:

[0079] (1) 18 g of fly ash and 2 g of calcium carbonate having an average particle size of 0.4 μm were mixed to obtain a mixture;

[0080] (2) The mixture obtained in step (1) was placed in a planetary ball mill at a rotation speed of 450 rpm and mechanically ball-milled for 30 min to obtain a modified fly ash dechlorination agent D2; wherein the ball milling beads included 30 g of small ball milling beads with a diameter of 5 mm and 70 g of large ball milling beads with a diameter of 10 mm, that is, the weight ratio of the mixture to the ball milling beads in the planetary ball mill was 1:5.

[0081] Comparative Example 3

[0082] Preparation of modified fly ash dechlorinating agent D4:

[0083] (1) 18 g of fly ash and 2 g of calcium carbonate having an average particle size of 0.1 μm were mixed to obtain a mixture;

[0084] (2) The mixture obtained in step (1) was placed in a planetary mixer at a rotation speed of 450 rpm and mechanically stirred for 30 min to obtain a modified fly ash dechlorination agent D4.

[0085] Comparative Example 4

[0086] Preparation of modified fly ash dechlorinating agent D5:

[0087] 20 g of fly ash was placed in a planetary ball mill at a speed of 450 rpm and mechanically milled for 30 min to obtain a modified fly ash dechlorination agent D5 (its microscopic morphology is shown in FIG. Figure 4 wherein the ball milling beads include 30 g of small ball milling beads with a diameter of 5 mm and 70 g of large ball milling beads with a diameter of 10 mm, that is, the weight ratio of the mixture to the ball milling beads in the planetary ball mill is 1:5.

[0088] Test Case

[0089] (1) The performance of the modified fly ash dechlorination agent prepared in the examples and comparative examples was characterized, mainly including average particle size, specific surface area and pore volume. The test results are shown in Table 1;

[0090] (2) The dechlorination performance of the modified fly ash dechlorinating agent prepared in the embodiment and the comparative example and the original fly ash was tested. The fixed bed test system was used for the experiment. The national standard HJ549-2016 was used to determine the HCl concentration in the treated flue gas. The specific test method was as follows: in the gas path of 1 L / min, the hydrogen chloride concentration was controlled to be 200 ppm. After passing through the flue gas premixing device, it entered a tubular furnace at a temperature of 200° C. 100 mg of the modified fly ash dechlorinating agent was placed in the middle of the tubular furnace to dechlorinate the gas. The hydrogen chloride content of the mixed gas after the reaction was detected, thereby calculating the removal rate of hydrogen chloride. The results are shown in Table 1.

[0091] Table 1

[0092] serial number Average particle size (μm) <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Pore volume (cm 3 / g)]]> Hydrogen chloride removal rate (%) Example 1 4.51 19.74 0.05 68 Example 2 3.75 22.17 0.03 72 Example 3 2.71 25.71 0.03 74 Example 4 4.42 19.72 0.04 71 Example 5 4.51 18.63 0.05 63 Example 6 4.58 18.37 0.04 65 Comparative Example 1 4.67 17.79 0.04 59 Comparative Example 2 6.17 16.79 0.04 58 Comparative Example 3 8.74 14.09 0.04 45 Comparative Example 4 4.97 15.41 0.05 40 Raw fly ash 10.29 12.93 0.05 20

[0093] It can be seen from the results in Table 1 that the modified fly ash dechlorinating agent prepared by the method of the present invention has a good dechlorination effect, and its hydrogen chloride removal rate is as high as 60% or more. At the same time, the average particle size of the prepared modified fly ash dechlorinating agent is less than 10 μm, and the specific surface area is 19.5-26 m 2 / g, pore volume is 0.03-0.05cm 3 / g.

[0094] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a modified fly ash dechlorinating agent, characterized in that: The method comprises the following steps: (1) mixing fly ash and calcium carbonate to obtain a mixture; (2) subjecting the mixture obtained in step (1) to mechanical ball milling; Wherein, in step (1), the total amount of fly ash and calcium carbonate is 100 weight %, and the amount of calcium carbonate is 10-30 weight %; The average particle size of the calcium carbonate is 0.1-0.3 μm.

2. The method according to claim 1, characterized in that In step (1), the fly ash contains one or more of unburned carbon, CaO, SiO2 and Al2O3.

3. The method according to claim 1 or 2, characterized in that: In step (2), the mechanical ball milling is carried out in the presence of ball milling beads.

4. The method according to claim 3, characterized in that The ball milling beads include small ball milling beads and large ball milling beads. The particle size of the small ball milling beads is 4-6 mm, and the particle size of the large ball milling beads is 9-11 mm.

5. The method according to claim 4, characterized in that In step (2), the weight ratio of the small ball milling beads to the large ball milling beads is 1-5:

7.

6. The method according to claim 4 or 5, characterized in that: The weight ratio of the mixture to the ball milling beads is 1:5-10.

7. The method according to any one of claims 1 to 6, characterized in that: In step (2), the conditions for mechanical ball milling include: a rotation speed of 400-600 rpm and a time of 30-60 min.

8. A modified fly ash dechlorinating agent prepared by the method according to any one of claims 1 to 7.

9. The modified fly ash dechlorination agent according to claim 8, characterized in that: The average particle size of the modified fly ash dechlorination agent is less than 10 μm, and the specific surface area is 19.5-26 m 2 / g, pore volume is 0.03-0.05cm 3 / g.

10. Use of the modified fly ash dechlorinating agent according to claim 8 or 9 in the flue gas dechlorination process of a coal-fired power plant.

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