A metal fiber catalytic filter material for integrated dust removal and denitrification and its preparation method

Abstract

The present invention discloses a dust removal and denitration integrated metal fiber catalytic filter material and a preparation method thereof. The preparation method comprises the following steps: mixing a metal salt A solution and a metal salt B solution, adjusting the pH and stirring under water bath heating conditions, centrifuging, washing, and then dispersing with deionized water to obtain a catalyst suspension containing a hydroxyl precursor; placing a pretreated metal fiber filter material into the catalyst suspension, performing ultrasonic-assisted in-situ deposition, and drying to obtain a catalyst-loaded metal fiber filter material; and calcining the catalyst-loaded metal fiber filter material to obtain a dust removal and denitration integrated metal fiber catalytic filter material. The preparation method provided by the present invention is simple to operate, and the raw materials are readily available, inexpensive, and non-toxic. The catalyst loaded on the prepared metal fiber filter material has high bonding strength, good dispersion performance, and excellent catalytic performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional filter materials, and in particular relates to a metal fiber catalytic filter material integrated with dust removal and denitration and a preparation method thereof. Background Art

[0002] Nitrogen oxides (NO x , including NO and NO2) cause great damage to organisms through direct and indirect effects, such as causing global acid rain, surface ozone and haze. Dust combined with toxic substances adhered to flue gas can also produce extreme weather such as haze, destroying the environment and affecting people's lives and production. Usually, a large amount of NO x (NO / NO x >95%) and dust coexist in the flue gases of various plants, such as coal / biomass power generation, steelmaking, cement manufacturing, glass products and coking plants, and waste incineration. Therefore, the removal of NO from the exhaust gases of these plants is necessary. x and dust are necessary and important.

[0003] Industrial furnaces are characterized by a wide variety, large number, low exhaust temperature, complex pollutant composition, and large concentration fluctuations. The traditional split flue gas treatment process that combines dust removal and denitrification in series has large equipment scale, high investment and operation and maintenance costs, and is difficult to adapt to the complex and changeable flue gas conditions of industrial furnaces. At present, the integrated dust removal and denitrification technology that uses filter materials as a matrix and couples catalytic denitrification active components has the characteristics of low cost, short process, and strong adaptability, and has become a new research direction in the field of industrial flue gas treatment. Among them, metal-based filter materials have excellent properties such as high temperature resistance, low pressure drop, corrosion resistance, and high mechanical strength, and can be used for the synergistic removal of dust and nitrogen oxides under high-temperature flue gas conditions. However, the preparation process of existing metal fiber filter materials is complicated, the catalyst has poor dispersion and low bonding strength, and the catalytic effect is not obvious, which makes it difficult to meet actual production needs. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an integrated metal fiber catalytic filter material for dust removal and denitrification and a preparation method thereof. The operation is simple, the raw materials are easily available, inexpensive and non-toxic, and the catalyst loaded on the metal fiber filter material has high bonding strength, good dispersion performance and excellent catalytic performance.

[0005] The present invention provides the following technical solutions:

[0006] In a first aspect, a method for preparing an integrated metal fiber catalytic filter material for dust removal and denitrification is provided, comprising the following steps:

[0007] The metal salt A solution and the metal salt B solution are mixed, the pH is adjusted and stirred under heating in a water bath, and after centrifugation and washing, the mixture is dispersed with deionized water to obtain a catalyst suspension containing a hydroxyl precursor;

[0008] placing the pretreated metal fiber filter material into the catalyst suspension, performing in-situ deposition with the assistance of ultrasound, and drying to obtain the catalyst-loaded metal fiber filter material;

[0009] The catalyst-loaded metal fiber filter material is calcined to obtain the dust removal and denitration integrated metal fiber catalytic filter material.

[0010] Furthermore, the metal salt A is ferric nitrate or ferric sulfate, and the metal salt B is one or more of ammonium tungstate, ammonium metatungstate, ammonium heptamolybdate, and ammonium molybdate.

[0011] Furthermore, the molar ratio of iron to tungsten in the metal salt A solution and the metal salt B solution is 1 to 9:1.

[0012] Furthermore, the specific preparation method of the catalyst suspension includes:

[0013] Prepare metal salt A solution and metal salt B solution separately, and heat them in a water bath to 50-80°C to promote the rapid dispersion of the catalyst precursor, increase the nucleation rate, inhibit the crystallization rate, and increase the specific surface area of ​​the catalyst;

[0014] Adding metal salt A solution to metal salt B solution and adding pH control agent at the same time to control the system pH to 4-6, the atomic coordination environment exposed on the catalyst surface will also be different under different pH conditions. When the pH is between 4-6, more Fe-OW / Mo is exposed on the catalyst surface, the redox performance is strong, and the performance of the catalyst can be further improved;

[0015] Stir for 1 to 3 hours, cool to room temperature, centrifuge, wash with water 2 to 5 times, and then disperse with deionized water to obtain a catalyst suspension containing a hydroxyl precursor with a solid content of 10 to 20%. Controlling the solid content is beneficial to the long-term stability of the catalyst suspension.

[0016] Furthermore, the pH control agent is one or more of ammonia water, urea, and ethanolamine.

[0017] Furthermore, the metal fiber filter material is one of 316L stainless steel filter material (SSFF), titanium fiber filter material (TiFF), Hastelloy fiber filter material (HFF), and nickel fiber filter material (NiFF), and has a three-dimensional porous structure with a porosity of 65-90%. The dust-facing surface is covered with a fine surface layer, and the dust-removing surface is attached with a metal support mesh, with a gram weight of 500-1000g / m 2 .

[0018] Furthermore, the pretreatment method of the metal fiber filter material includes:

[0019] Cut the metal fiber filter material into circular shapes with a diameter of 5 to 20 cm. Prepare a 0.5 to 2 mol / L acid solution and immerse the cut metal fiber filter material in the acid solution for 0.5 to 1 hour for acidification. Then, ultrasonically wash it until neutral and dry it. Acidification removes impurities from the metal fibers, improves the fiber interlacing and internal pore structure, and exposes more attachment sites.

[0020] Furthermore, the acid solution is one or more of nitric acid solution, phosphoric acid solution, and acetic acid solution.

[0021] Furthermore, the catalyst-loaded metal fiber filter material is calcined in a muffle furnace at a temperature of 300 to 600° C. for 2 to 6 hours, and the catalyst loading of the obtained dust removal and denitration integrated metal fiber catalytic filter material is 50 to 400 g / m 2 .

[0022] Furthermore, the catalyst loading can be controlled by repeating the in-situ deposition and drying operations for a certain number of times.

[0023] In a second aspect, a metal fiber catalytic filter material for dust removal and denitrification integrated with the method of the first aspect is provided.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention adopts a pH-adjusted assisted co-precipitation method to prepare a catalyst suspension containing a hydroxyl precursor, and loads the catalyst on the metal binding sites of the pretreated metal fiber filter material by an ultrasound-assisted in-situ deposition method. Through hydrogen bonds and the formed metal-oxygen bonds, the loaded catalyst has high binding strength and good dispersion performance, which helps to improve the catalytic performance;

[0026] (2) The catalyst suspension of the present invention is heated in a water bath environment, which can stabilize the reaction temperature, avoid violent reaction, promote rapid dispersion of the catalyst, increase the nucleation rate, inhibit the crystallization rate, and increase the specific surface area of ​​the catalyst;

[0027] (3) The metal fiber filter material selected in the present invention has excellent properties such as high temperature resistance, low pressure drop, corrosion resistance and high mechanical strength;

[0028] (4) The present invention uses Fe and W or Mo as the active center of the catalyst. Fe-based catalysts are inexpensive, readily available, and have excellent catalytic performance. The introduction of W or Mo elements can improve the acidity of the catalyst surface and provide abundant surface active acid sites, further improving the catalyst performance. It also has the advantages of being green and non-toxic.

[0029] (5) The present invention uses an acidification method to pretreat the metal fiber filter material, which can effectively remove impurities such as oxides on the surface of the metal fiber, thereby exposing more attachment sites, which is beneficial to improving the bonding strength of the catalyst;

[0030] (6) The present invention can form a catalyst metal oxide on the fiber in situ by calcining the catalyst precursor, so that the catalyst and the metal fiber are more firmly bonded and not easily detached;

[0031] (7) The appropriate loading amount of the catalyst of the present invention can not only make the filter material achieve better catalytic performance, but also save production costs. Too low a loading amount may result in too little catalyst, thereby reducing the catalytic performance of the filter material. Too high a loading amount will increase economic costs and cause catalyst agglomeration, which will cause the piezoresistance of the filter material to increase, thereby reducing the filtration performance of the filter material.

[0032] (8) The solid content of the catalyst suspension in the present invention is controlled within an appropriate range. On the one hand, it can ensure the presence of abundant hydroxyl groups in the catalyst suspension, so that the catalytic particles can be stably present in the solution. If the solid content is too low, the catalyst loading will be too low, the preparation efficiency will be low, and the production cost will be high. If the solid content is too high, the catalytic suspension will be unstable. When the catalyst is loaded on the filter material, the catalyst will be unevenly distributed on the filter material, which is not conducive to the catalyst penetrating into the interior of the metal fiber filter material, and may cause blockage, affecting the filtration and catalytic performance of the filter material.

[0033] (9) The preparation method provided by the present invention is simple to operate, and the raw materials are readily available, inexpensive and non-toxic. No binder is required, which reduces the production cost. At the same time, it has the characteristics of being green and pollution-free, and can achieve efficient and environmentally friendly integrated removal of NOx and dust. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is an appearance diagram of the FeW / SSFF filter material prepared in Example 1;

[0035] Figure 2 is a SEM image of the FeW / SSFF filter material prepared in Example 1;

[0036] Figure 3 Graphs showing the catalyst binding strength of FeW / SSFF, FeW / TiFF, and FeMo / NiFF filter materials prepared in Examples 1, 2, and 3. DETAILED DESCRIPTION

[0037] The following examples are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0038] Example 1

[0039] (1) Weigh 0.008 mol of H28 N6O 41 W 12 (ammonium metatungstate) and 0.8 mol of Fe(NO3)3·9H2O (ferric nitrate) were dissolved in water (the molar ratio of W to Fe was n W :n Fe =1:8), and two metal salt solutions were obtained.

[0040] (2) Heat in a water bath at 50°C, then mix the two metal salt solutions, adjust the pH to about 6 with ammonia water, stir at high speed for 1 hour, cool to room temperature, centrifuge, wash twice, and disperse with deionized water to obtain a FeW catalyst suspension with a solid content of 15%.

[0041] (3) Select a porosity of 65% and a weight of 100g / m 2 The SSFF was cut into circular filter discs with a diameter of 5 cm, and acidified by immersing them in 2 mol / L nitric acid for 30 min. The discs were then ultrasonically washed for 30 min, washed three times with water until neutral, and dried at 120 °C. The mass was recorded for later use.

[0042] (4) Place the SSFF pretreated in step (3) into the FeW catalyst suspension and perform in-situ deposition with ultrasound for 10 min. Then place it in an oven and dry it at 120°C. Record the catalyst loading. Repeat the operation several times and adjust the catalyst loading to 400 g / m 2 The filter disc was placed in a muffle furnace and heated to 300 °C for 2 h before being taken out and recorded as FeW / SSFF.

[0043] Example 2

[0044] (1) Weigh 0.007 mol of (NH4)6W7O 24 ·6H2O (ammonium tungstate) and 0.25mol FeSO4·5H2O (ferric sulfate) were dissolved in water (n W :n Fe =1:5), and two metal salt solutions were obtained.

[0045] (2) Heat the mixture in a water bath at 60°C, then mix the two metal salt solutions, adjust the pH to about 5 with urea, stir at high speed for 2 hours, cool to room temperature, centrifuge, wash three times, and disperse with deionized water to obtain a FeW catalyst suspension with a solid content of 10%.

[0046] (3) Select a porosity of 80% and a weight of 750g / m 2 The TiFF was cut into circular filter discs with a diameter of 10 cm, and acidified by immersing them in 1 mol / L phosphoric acid for 30 min. The discs were then ultrasonically washed for 30 min, washed three times with water until neutral, and dried at 120 °C. The mass was recorded for later use.

[0047] (4) Place the TiFF pretreated in step (3) into the FeW catalyst suspension and perform in-situ deposition with ultrasound for 10 minutes. Then place it in an oven and dry it at 120°C. Record the catalyst loading. Repeat the operation several times and adjust the catalyst loading to 200 g / m 2 The filter disc was placed in a muffle furnace and heated to 450 °C for 6 h before being taken out and recorded as FeW / TiFF.

[0048] Example 3

[0049] (1) Weigh 0.01 mol of (NH4)2MoO4 (ammonium molybdate) and 0.09 mol of FeSO4·5H2O (ferric sulfate) and dissolve them in water (n Mo :n Fe =1:9), and two metal salt solutions were obtained.

[0050] (2) Heat in a water bath at 80°C, then mix the two metal salt solutions, adjust the pH to about 4 with ethanolammonium, stir at high speed for 3 hours, cool to room temperature, centrifuge, wash five times, and disperse with deionized water to obtain a FeMo catalyst suspension with a solid content of 20%.

[0051] (3) Select a porosity of 90% and a weight of 500g / m 2 The NiFF was cut into circular filter discs with a diameter of 20 cm, and acidified by immersing them in 0.5 mol / L acetic acid for 30 min. The discs were then ultrasonically washed for 30 min, washed three times with water until neutral, and dried at 120 °C. The mass was recorded for later use.

[0052] (4) Place the NiFF pretreated in step (3) into the FeMo catalyst suspension and perform in-situ deposition with ultrasound for 10 minutes. Then place it in an oven and dry it at 120°C. Record the catalyst loading. Repeat the operation several times and adjust the catalyst loading to 50 g / m 2 The filter disc was placed in a muffle furnace and heated to 600 °C for 4 h before being taken out and recorded as FeMo / NiFF.

[0053] Performance Comparison

[0054] (1) Figure 1 This is an appearance diagram of the FeW / SSFF filter material prepared in Example 1. As can be seen from the figure, the catalyst is evenly dispersed on the surface of the metal filter material, indicating that the pH-assisted co-precipitation method used in the present invention is beneficial to improving the dispersion performance of the catalyst.

[0055] (2) Figure 2This is the SEM image of the FeW / SSFF filter material prepared in Example 1. It can be seen from the figure that the catalyst particles are evenly distributed inside the metal filter material, indicating good bonding strength between the catalyst and the metal fiber filter material.

[0056] (3) The catalyst bonding strength test was conducted on the FeW / SSFF obtained in Example 1, the FeW / TiFF obtained in Example 2, and the FeMo / NiFF obtained in Example 3. Specifically, a blowing experiment was used, and the experimental conditions were: V gas =1m / min, P gas =0.5MPa, spray once every 5 seconds.

[0057] The results of the spraying experiment are as follows Figure 3 As shown, the quality of the catalysts synthesized in the three examples did not decrease significantly after 500 injections, and all had excellent bonding strength, which demonstrates the advantages of the acidification treatment of the metal filter material, the reasonable solid content and loading amount, and the in-situ deposition synthesis method in the present invention.

[0058] (4) FeW / SSFF obtained in Example 1, FeW / TiFF obtained in Example 2, and FeMo / NiFF obtained in Example 3 were subjected to NO x The conversion rate was tested, and the denitrification efficiency and dust removal efficiency were calculated. The results are shown in Table 1 below.

[0059] NO x The conversion rate test was carried out in a homemade tubular metal fixed-bed reactor.

[0060] Test conditions: NH3 500ppm, NO x 500ppm, O2 10%, H2O 5%, N2 as carrier gas, gas flow rate of 1m / min, reaction temperature of 100~450℃.

[0061] After being fully mixed in the mixing tank, the reaction gas is preheated in the preheater and finally enters the reactor. The composition and content of the inlet and outlet gases of the fixed bed reactor are continuously monitored online using a gasmet analyzer.

[0062] Calculate denitrification efficiency = [(C-C0) / C0]*100%

[0063] Where C0 represents the initial NO x concentration, C represents the NO after reaction x concentration.

[0064] Calculate dust removal efficiency = (1-C'*Q / C0'*Q0)*100%

[0065] Where C' is the dust concentration of the gas at the outlet of the integrated filter material, Q is the gas flow rate at the outlet of the integrated filter material, C0' is the dust concentration of the gas at the outlet of the integrated filter material, and Q0 is the gas flow rate at the outlet of the integrated filter material.

[0066] Table 1 Denitrification efficiency and dust removal efficiency results of filter materials in Examples 1-3

[0067] sample Reaction temperature (℃) Denitrification efficiency (%) Dust removal efficiency (%) Example 1 200 95 99.996 Example 2 250 96 99.996 Example 3 450 97 99.990

[0068] As can be seen from Table 1, the three filter materials synthesized in the examples of the present invention all have good dust removal and denitrification efficiencies, and can achieve efficient integrated removal of dust and nitrogen oxides, which indicates that the present invention has good application prospects in the field of industrial flue gas treatment.

[0069] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a metal fiber catalytic filter material for integrated dust removal and denitrification, characterized in that: The following steps are involved: The metal salt A solution and the metal salt B solution are mixed, heated in a water bath to 50-80° C., the pH is adjusted to control the system pH to 4-6, stirred, centrifuged, washed, and then dispersed with deionized water to obtain a catalyst suspension containing a hydroxyl precursor with a solid content of 10-20%, wherein the metal salt A is ferric nitrate or ferric sulfate, and the metal salt B is one or more of ammonium tungstate, ammonium metatungstate, ammonium heptamolybdate, and ammonium molybdate; The pretreated metal fiber filter material is placed in the catalyst suspension, ultrasonically assisted in in-situ deposition is performed, and the catalyst-loaded metal fiber filter material is dried to obtain the catalyst-loaded metal fiber filter material. The pretreatment method of the metal fiber filter material comprises: placing the cut metal fiber filter material in an acid solution and immersing it for 0.5 to 1 hour for acidification treatment, then ultrasonically washing it with water until it is neutral, and drying it; The catalyst-loaded metal fiber filter material is calcined at a temperature of 300-600° C. for 2-6 hours to obtain a dust removal and denitration integrated metal fiber catalytic filter material.

2. The method for preparing the integrated metal fiber catalytic filter material for dust removal and denitrification according to claim 1, characterized in that: The atomic molar ratio of iron to tungsten or molybdenum in the metal salt A solution and the metal salt B solution is 1-9:

1.

3. The method for preparing the integrated metal fiber catalytic filter material for dust removal and denitrification according to claim 1, characterized in that: The specific preparation method of the catalyst suspension comprises: Prepare metal salt A solution and metal salt B solution separately and heat them in a water bath to 50-80°C; Add the metal salt A solution to the metal salt B solution, and simultaneously add a pH control agent to control the system pH to 4-6. Stir for 1-3 hours, cool to room temperature, centrifuge, wash with water 2-5 times, and then disperse with deionized water to obtain a catalyst suspension containing a hydroxyl precursor with a solid content of 10-20%.

4. The method for preparing the integrated metal fiber catalytic filter material for dust removal and denitrification according to claim 3, characterized in that: The pH control agent is one or more of ammonia water, urea, and ethanolamine.

5. The method for preparing the integrated metal fiber catalytic filter material for dust removal and denitrification according to claim 1, characterized in that: The metal fiber filter material is one of 316L stainless steel filter material, titanium fiber filter material, Hastelloy fiber filter material, and nickel fiber filter material, and has a three-dimensional porous structure with a porosity of 65-90%. The dust-facing side is covered with a fine surface layer, and the dust-removing side is attached with a metal support mesh. The gram weight is 500-1000g / m 2 .

6. The method for preparing the integrated metal fiber catalytic filter material for dust removal and denitrification according to claim 1, characterized in that: The pretreatment method of the metal fiber filter material comprises: Cut the metal fiber filter material into a circle with a diameter of 5~20cm, prepare a 0.5~2mol / L acid solution, place the cut metal fiber filter material in the acid solution and immerse it for 0.5~1h for acidification treatment, then ultrasonically wash it until it is neutral and dry it.

7. The method for preparing the integrated metal fiber catalytic filter material for dust removal and denitrification according to claim 6, characterized in that: The acid solution is one or more of nitric acid solution, phosphoric acid solution and acetic acid solution.

8. The method for preparing the integrated metal fiber catalytic filter material for dust removal and denitrification according to claim 1, characterized in that: The catalyst-loaded metal fiber filter material is calcined in a muffle furnace to obtain a catalyst loading of 50-400 g / m 2 .

9. A metal fiber catalytic filter material for dust removal and denitrification prepared by the method according to any one of claims 1 to 8.

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