CN110980808B - Preparation method and system of ammonium metatungstate for denitration catalyst - Google Patents
Preparation method and system of ammonium metatungstate for denitration catalyst Download PDFInfo
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- CN110980808B CN110980808B CN201911009140.4A CN201911009140A CN110980808B CN 110980808 B CN110980808 B CN 110980808B CN 201911009140 A CN201911009140 A CN 201911009140A CN 110980808 B CN110980808 B CN 110980808B
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- C01—INORGANIC CHEMISTRY
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- C01G41/00—Compounds of tungsten
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8621—Removing nitrogen compounds
- B01D53/8625—Nitrogen oxides
- B01D53/8628—Processes characterised by a specific catalyst
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/24—Nitrogen compounds
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- B01D2258/02—Other waste gases
- B01D2258/0283—Flue gases
Abstract
The invention provides a preparation method and a system of ammonium metatungstate for a denitration catalyst, which belong to the technical field of flue gas denitration and comprise the steps of leaching, clarifying, nanofiltration, filtering, concentrating, crystallizing and the like, wherein the system comprises a stirring tank, filtering equipment, an aging tank, a suction filter, nanofiltration equipment, a crystallizing tank and the like, and the obtained high-purity crystalline ammonium metatungstate is suitable for preparation of the denitration catalyst; the invention also provides a denitration catalyst, which is prepared by using the ammonium metatungstate prepared by the method as a raw material, adding a small amount of surfactant, and combining an ultrasonic treatment process, and has the advantages of high denitration efficiency, large specific surface area and better mechanical strength and abrasion strength performance.
Description
Technical Field
The invention relates to a preparation method and a system of ammonium metatungstate for a denitration catalyst, and belongs to the technical field of flue gas denitration.
Background
Nitrogen Oxides (NO) x ) Is one of the main harmful substances polluting the atmosphere and mainly comes from the combustion of fossil fuels (such as coal, petroleum, natural gas and the like), wherein the flue gas of the coal-fired power plant is NO x Is the primary source of (a). The selective catalytic reduction (selectivecatalytical reduction, SCR) denitration method is to utilize a reducing agent (NH) at a certain temperature under the action of a catalyst 3 Methane, thiourea, CO, H 2 Etc.) to selectively remove NO x Reducing to nitrogen, NH in the reducing agent 3 Most commonly used. Because the SCR technology has the advantages of lower reaction temperature, high purification rate, reliable operation, small secondary pollution and the like, the technology is the flue gas denitration (NO removal) with the widest application at present x ) Techniques. In SCR systems, the performance of the catalyst directly affects NO x The cost of the removal effect of the catalyst is about 20% -40% of the total cost of the SCR system, so the catalyst is one of the cores of the SCR technology.
Currently, three SCR commercial catalysts have been developed: noble metals, metal oxides, and molecular sieve catalysts. Wherein, the titanium dioxide (TiO 2 ) Is a carrier, with tungsten oxide (WO 3 ) Or molybdenum oxide (MoO) 3 ) Metal oxide catalyst as promoter in NO x Reduction and SO 2 The oxidation rate shows a real advantage.
There are a number of documents and patents describing denitration catalysts, but ammonium metatungstate used for denitration catalysts is less common in the prior art. The patent of publication No. CN109529813A relates to a honeycomb type low-temperature SCR denitration catalyst and a preparation method thereof, and has more raw materials and more complicated preparation method.
Disclosure of Invention
The invention provides a preparation method of ammonium metatungstate used for a denitration catalyst, which comprises the steps of leaching, clarifying, nanofiltration, filtering, concentrating, crystallizing and the like, and the obtained high-purity crystalline ammonium metatungstate is suitable for preparing the denitration catalyst.
A method for preparing ammonium metatungstate used for a denitration catalyst, comprising the steps of:
s1, adding wet ammonium paratungstate into pure water with stirring, heating, adding a nitric acid solution, and filtering to obtain a dilute ammonium paratungstate solution;
s2, standing and ageing the dilute ammonium metatungstate solution, filtering to obtain filtrate I, pumping the filtrate I into a reaction kettle, heating and concentrating, and continuing standing and ageing, and filtering by nanofiltration to obtain filtrate II;
s3, pumping the filtrate II into a reaction kettle, heating and concentrating, continuously standing, and filtering to obtain a concentrated ammonium metatungstate solution;
and S4, crystallizing the concentrated ammonium metatungstate solution to obtain the ammonium metatungstate for the denitration catalyst.
Preferably, the specific method for heating and adding the nitric acid solution in the step S1 is as follows:
s11, firstly heating to 60-70 ℃, adding nitric acid, and controlling the pH value of the solution to be 4.5-5.5;
s12, continuously heating to boiling, adding nitric acid, controlling the pH value of the solution to be 3-4, and obtaining the solution WO 3 When the content reaches 200-250g/L, boiling and stirring are carried out for more than 30 minutes.
Preferably, the heating concentration in the step S2 is carried out until the specific gravity of the solution reaches 1.8-2.0.
Preferably, the heating concentration in the step S3 is carried out until the specific gravity of the solution reaches 2.2-2.4
The ammonium metatungstate is prepared by the method.
The invention also provides a preparation system of ammonium metatungstate for the denitration catalyst, which improves the stirring paddle structure by adding nanofiltration equipment and is provided with a plurality of layers of filter cloth, so that the performance of the denitration catalyst can be improved by the obtained ammonium metatungstate.
A system for preparing ammonium meta-tungstate for a denitration catalyst, comprising: stirring tank, reaction kettle, filtering device, aging tank, crystallization tank, nanofiltration device; the ageing jar drain pipe is connected with nanofiltration equipment feed liquor pipe for with the dilute ammonium metatungstate solution purification treatment after ageing, nanofiltration equipment drain pipe and reation kettle feed liquor pipe connection are used for carrying out heating concentration treatment with the dilute ammonium metatungstate solution after the purification, and agitator tank, filtration equipment, ageing jar a, suction filter a, reation kettle a, ageing jar b, nanofiltration equipment, reation kettle b, suction filter b, crystallization tank pass through the pipe connection in proper order.
Preferably, the suction filter a comprises two stages of filter cloth and the suction filter b comprises four stages of filter cloth.
Preferably, the stirring tank is internally provided with stirring paddles which are divided into three layers, wherein the first layer is a net-shaped paddle, and the second layer is a hole-shaped paddle.
The invention also provides a denitration catalyst, which is prepared by using the method as a raw material, and comprises the following steps:
(1) adding a surfactant into pure water, stirring, adding ammonium metatungstate, heating to boil, continuously adding titanium dioxide, mixing and carrying out ultrasonic treatment to obtain a mixture;
(2) and (3) sintering the mixture obtained in the step (1) at a high temperature to obtain the denitration catalyst.
Preferably, the surfactant in the step (1) is tween, and the dosage is 0.1-0.5% of the weight of the ammonium metatungstate.
Preferably, the ammonium metatungstate in the step (1) is used in an amount of 4-6% by weight of the titanium dioxide.
Preferably, the high temperature sintering temperature in step (2) is 800-1200 ℃.
According to the method, the purity of the ammonium metatungstate solution can be improved through the nanofiltration technology, two-stage filter cloth filtration and concentration are firstly carried out in the process steps, then the nanofiltration technology is adopted, and finally four-stage filter cloth filtration and concentration are carried out, on the basis of improving the purity of the ammonium metatungstate solution, the ammonium metatungstate with larger particle size is removed, and in the process of preparing the denitration catalyst by doping titanium dioxide with the ammonium metatungstate, the small-particle-size ammonium metatungstate can be filled in gaps generated by stacking titanium dioxide powder particles, so that the combination is tighter, and the mechanical strength of the catalyst is improved.
In the invention, nitric acid is added after the temperature is raised to a certain temperature in the reaction step, then nitric acid is added continuously after the temperature is raised to a certain temperature, the purpose of adding nitric acid after the temperature is raised to a certain temperature is to activate wet ammonium paratungstate, then nitric acid is added continuously after the temperature is raised to the boiling, the reaction is carried out to generate ammonium paratungstate, the leaching of the ammonium paratungstate is facilitated, and the method is used for WO 3 The conversion rate of the catalyst is improved to a certain extent, and the catalytic efficiency of the denitration catalyst is improved.
According to the system, the structure of the stirring paddle is improved, the upper-layer reticular stirring paddle can crush the input wet ammonium paratungstate simultaneously in the stirring process, the hole-shaped stirring paddle in the middle layer quickens the rotational flow of pure water, the heat transfer efficiency of the pure water can be improved in the heating process, and the reaction leaching efficiency is improved.
The denitration catalyst prepared by the method comprises the steps of adding a small amount of surfactant into pure water, adding titanium dioxide into the pure water, and balancing TiO (titanium dioxide) 2 The surface tension among the nano particles reduces the difference between the evaporation rates of the moisture in the sintering process, reduces the occurrence of cracks of the catalyst product, improves the abrasion strength, prolongs the service life of the catalyst, combines ultrasonic treatment in mixing, and ultrasonic treatment can improve the mixing effect on one hand, so that the mixing is uniform, and further breaks the titanium pigment in the mixing on the other hand, thereby increasing the specific surface area of the catalyst.
The invention has the advantages that:
1. the nanofiltration technology is added, the filter cloth filtering and concentrating process in the system is combined, the particle size of the ammonium metatungstate is reduced on the basis of improving the purity of the ammonium metatungstate solution, so that the ammonium metatungstate is tightly combined with the titanium white, and the mechanical strength of the denitration catalyst is improved.
2. The two-step method of nitric acid leaching reaction can improve WO 3 And simultaneously enhances the catalytic efficiency of the denitration catalyst.
3. The improved stirring paddle structure in the stirring tank of the system has the double effects of further crushing wet ammonium paratungstate and improving the heat transfer efficiency of pure water.
4. The prepared denitration catalyst is added with a small amount of surfactant, and the technical effects of prolonging the service life of the catalyst and increasing the specific surface area of the catalyst can be achieved by combining an ultrasonic treatment process.
Drawings
Fig. 1 is a system configuration diagram of a preferred embodiment of the present invention.
Fig. 2 is a structural view of a stirring tank in a preferred embodiment of the present invention.
Reference numerals: a stirring tank 1, a filtering device 2, an aging tank a3, a suction filter a4, a reaction kettle a5, an aging tank b6, a nanofiltration device 7, a reaction kettle b8, a suction filter b9 and a crystallization tank 10.
Detailed Description
Embodiments of the present invention are further described below with reference to the accompanying drawings.
Example 1
The preparation system of ammonium meta-tungstate for the denitration catalyst comprises: stirring tank, reaction kettle, filtering device, aging tank, crystallization tank, nanofiltration device; the ageing jar drain pipe is connected with the nanofiltration equipment 7 feed liquor pipe for with the dilute ammonium metatungstate solution purification treatment after ageing, nanofiltration equipment 7 drain pipe and reation kettle feed liquor pipe connection are used for carrying out the heating concentration treatment with the dilute ammonium metatungstate solution after purifying, and agitator tank 1, filtration equipment 2, ageing jar a3, suction filter a4, reation kettle a5, ageing jar b6, nanofiltration equipment 7, reation kettle b8, suction filter b9, crystallization jar 10 loops through the pipe connection. The suction filter a3 is provided with two-stage filter cloth, and the suction filter b9 is provided with four-stage filter cloth. The embodiment is provided with a plurality of layers of filter cloth, so that the filtering effect is ensured, and the purity of the product is improved.
Example 2
This embodiment is a modification of embodiment 1 in that a stirring paddle 13 is installed in the stirring tank 1, the stirring paddle 13 is divided into three layers, the first layer is a mesh blade 11, and the second layer is a hole blade 12. In the stirring process, the upper-layer reticular stirring paddles can be changed into the porous stirring paddles in the middle layer to accelerate the rotational flow of pure water, so that the heat transfer efficiency of the pure water can be improved in the heating process, and the reaction leaching efficiency can be improved.
Example 3
The preparation method of the ammonium metatungstate used for the denitration catalyst comprises the following steps:
s1, stirring pure water in a stirring tank 1 by using a reticular blade 11 and a porous blade 12, adding wet ammonium paratungstate into the stirred pure water, heating to 60-70 ℃, adding nitric acid, controlling the pH value of the solution to be 4.5-5.5, continuously heating to boil, adding nitric acid, controlling the pH value of the solution to be 3-4, and adding a solution WO (WO) 3 When the content reaches 200-250g/L, boiling and stirring for more than 30 minutes, and filtering in a filtering device 2 to obtain a dilute ammonium metatungstate solution;
s2, standing and ageing the dilute ammonium metatungstate solution in an ageing tank a3, filtering the dilute ammonium metatungstate solution in a suction filter a4 in two stages to obtain filtrate I, pumping the filtrate I into a reaction kettle a5, heating and concentrating the filtrate I until the specific gravity of the solution reaches 1.8-2.0, continuing standing and ageing the solution in an ageing tank b6, and filtering the solution in a nanofiltration device 7 to obtain filtrate II;
s3, pumping the filtrate II into a reaction kettle b8, heating and concentrating until the specific gravity of the solution reaches 2.2-2.4, standing, and filtering in a suction filter b9 for four stages to obtain a concentrated ammonium metatungstate solution;
and S4, crystallizing the concentrated ammonium metatungstate solution in a crystallization tank 10 to obtain the ammonium metatungstate for the denitration catalyst.
Example 4
The preparation method of the ammonium metatungstate used for the denitration catalyst comprises the following steps:
s1, adding wet ammonium paratungstate into pure water with stirring, heating to 60 ℃, adding nitric acid, controlling the pH value of the solution to be 4.5, continuously heating to boiling, adding nitric acid, controlling the pH value of the solution to be 3, and adding a solution WO (WO) 3 When the content reaches 200g/L, boiling and stirring for more than 30 minutes, and filtering to obtain a dilute ammonium metatungstate solution;
s2, standing and ageing the dilute ammonium metatungstate solution, filtering to obtain a filtrate I, pumping the filtrate I into a reaction kettle, heating and concentrating until the specific gravity of the solution reaches 1.8, continuing standing and ageing, and filtering by nanofiltration to obtain a filtrate II;
s3, pumping the filtrate II into a reaction kettle, heating and concentrating until the specific gravity of the solution reaches 2.2, continuously standing, and filtering to obtain a concentrated ammonium metatungstate solution;
and S4, crystallizing the concentrated ammonium metatungstate solution to obtain the ammonium metatungstate for the denitration catalyst.
The method for preparing the denitration catalyst by using the ammonium metatungstate as a raw material comprises the following steps:
(1) adding a surfactant which is tween in an amount of 0.1 percent by weight of ammonium metatungstate into pure water, stirring, adding the ammonium metatungstate, heating to boiling, continuously adding titanium white in an amount of 4 percent by weight of the titanium white, mixing and carrying out ultrasonic treatment to obtain a mixture;
(2) and (3) performing high-temperature sintering at 800 ℃ on the mixture obtained in the step (1) to obtain the denitration catalyst.
Example 5
The preparation method of the ammonium metatungstate used for the denitration catalyst comprises the following steps:
s1, adding wet ammonium paratungstate into pure water with stirring, heating to 65 ℃, adding nitric acid, controlling the pH value of the solution to be 5, continuously heating to boiling, adding nitric acid, controlling the pH value of the solution to be 3.5, and obtaining the solution WO 3 When the content reaches 220g/L, boiling and stirring for more than 30 minutes, and filtering to obtain a dilute ammonium metatungstate solution;
s2, standing and ageing the dilute ammonium metatungstate solution, filtering to obtain a filtrate I, pumping the filtrate I into a reaction kettle, heating and concentrating until the specific gravity of the solution reaches 1.9, continuing standing and ageing, and filtering by nanofiltration to obtain a filtrate II;
s3, pumping the filtrate II into a reaction kettle, heating and concentrating until the specific gravity of the solution reaches 2.3, continuously standing, and filtering to obtain a concentrated ammonium metatungstate solution;
and S4, crystallizing the concentrated ammonium metatungstate solution to obtain the ammonium metatungstate for the denitration catalyst.
The method for preparing the denitration catalyst by using the ammonium metatungstate as a raw material comprises the following steps:
(1) adding a surfactant which is tween in an amount of 0.3 percent by weight of ammonium metatungstate into pure water, stirring, adding the ammonium metatungstate, heating to boiling, continuously adding titanium white, wherein the amount of the ammonium metatungstate is 5 percent by weight of the titanium white, mixing and carrying out ultrasonic treatment to obtain a mixture;
(2) and (3) sintering the mixture obtained in the step (1) at a high temperature of 1000 ℃ to obtain the denitration catalyst.
Example 6
The preparation method of the ammonium metatungstate used for the denitration catalyst comprises the following steps:
s1, adding wet ammonium paratungstate into pure water with stirring, heating to 70 ℃, adding nitric acid, controlling the pH value of the solution to be 5.5, continuously heating to boiling, adding nitric acid, controlling the pH value of the solution to be 4, and obtaining the solution WO 3 When the content reaches 250g/L, boiling and stirring for more than 30 minutes, and filtering to obtain a dilute ammonium metatungstate solution;
s2, standing and ageing the dilute ammonium metatungstate solution, filtering to obtain a filtrate I, pumping the filtrate I into a reaction kettle, heating and concentrating until the specific gravity of the solution reaches 2.0, continuing standing and ageing, and filtering by nanofiltration to obtain a filtrate II;
s3, pumping the filtrate II into a reaction kettle, heating and concentrating until the specific gravity of the solution reaches 2.4, continuously standing, and filtering to obtain a concentrated ammonium metatungstate solution;
and S4, crystallizing the concentrated ammonium metatungstate solution to obtain the ammonium metatungstate for the denitration catalyst.
The method for preparing the denitration catalyst by using the ammonium metatungstate as a raw material comprises the following steps:
(1) adding a surfactant which is tween in an amount of 0.5% by weight of ammonium metatungstate into pure water, stirring, adding ammonium metatungstate, heating to boil, continuously adding titanium white in an amount of 6% by weight of the titanium white, mixing and performing ultrasonic treatment to obtain a mixture;
(2) and (3) sintering the mixture obtained in the step (1) at a high temperature of 1200 ℃ to obtain the denitration catalyst.
Example 7
The difference from example 5 is that:
the method for preparing the denitration catalyst by using the ammonium metatungstate as a raw material comprises the following steps:
(1) adding a surfactant which is tween in an amount of 0.2 percent by weight of ammonium metatungstate into pure water, stirring, adding the ammonium metatungstate, heating to boiling, continuously adding titanium white, wherein the amount of the ammonium metatungstate is 4.5 percent by weight of the titanium white, mixing and carrying out ultrasonic treatment to obtain a mixture;
(2) and (3) performing high-temperature sintering at 900 ℃ on the mixture obtained in the step (1) to obtain the denitration catalyst.
Example 8
The difference from example 6 is that:
the method for preparing the denitration catalyst by using the ammonium metatungstate as a raw material comprises the following steps:
(1) adding a surfactant which is tween in an amount of 0.4 percent by weight of ammonium metatungstate into pure water, stirring, adding the ammonium metatungstate, heating to boiling, continuously adding titanium white in an amount of 5.5 percent by weight of the titanium white, mixing and carrying out ultrasonic treatment to obtain a mixture;
(2) and (3) sintering the mixture obtained in the step (1) at a high temperature of 1100 ℃ to obtain the denitration catalyst.
Comparative example 1
The difference from example 4 is that:
in step S2, nanofiltration is not performed, but the filtrate II is obtained by filtration with a filtration device.
Comparative example 2
The difference from example 5 is that:
s1, adding wet ammonium paratungstate into pure water with stirring, heating to boil, adding nitric acid, controlling the pH value of the solution to be 3.5, and obtaining a solution WO 3 When the content reaches 220g/L, boiling and stirring are carried out for more than 30 minutes, and the dilute ammonium metatungstate solution is obtained by filtering.
Comparative example 3
The difference from example 6 is that:
in the step (1), no surfactant is added into the pure water, and the pure water is directly stirred and added with ammonium metatungstate
Comparative example 4
The difference from example 7 is that:
in the step (1), an ultrasonic process is not adopted, and the mixture is obtained through mixing treatment.
Test example:
the catalysts prepared in examples 4 to 8 and comparative examples 1 to 4 of the present invention were subjected to the following experiments.
1. Denitration efficiency of the catalyst of the invention: the performance of the catalyst is evaluated on a fixed bed device, the reaction flue gas is simulated flue gas, and the total flow is 3.98m 3 /h，O 2 3% by volume, 8% by volume of water vapor, NH 3 With NO x The volume ratio is 1:1, NO x Volume fraction of 200. Mu.L/L, SO 2 Volume fraction of 500. Mu.L/L, reaction space velocity of 23000h -1 The reaction temperature was 380 ℃. The flue gas measurement adopts a Germany portable flue gas analyzer. Denitration efficiency of catalyst with NO x Conversion (. Eta.) NOx ) The calculation formula is as follows:
η NOx ＝(C NOx，in -C NOx，out )/C NOx，in ×100％
wherein: c (C) NOx，in Is the volume fraction of nitrogen oxides in the air inlet; c (C) NOx，out Is the volume fraction of nitrogen oxide at the air outlet.
2. Mechanical strength and attrition strength of the catalyst of the invention: the compressive strength of the catalyst is tested by using a YAW-100 cement mortar pressure tester, and a test sample is cut into squares with the side length of 150mm, and the loading rate is 1.125kN/s; the abrasion performance is detected according to the requirements in the national standard GB/T31587-2015 of honeycomb flue gas denitration catalyst, the catalyst is cut into two sample modules with 8mm multiplied by 8mm holes, the two sample modules are dried for 2 hours at 105 ℃, and the two sample modules are respectively placed into a test sample and a comparison sample after being cooled, the wind speed is 14.5m/s, and the mass concentration of quartz sand is 52g/m 3 The test time was 2h.
3. Specific surface area of the catalyst of the invention: the specific surface area of the catalyst sample was measured using a TriStar3000 Micromeritics type adsorber, the sample was pretreated at 300℃for 2h with N 2 For adsorbate, at liquid nitrogen temperatureAdsorption, treatment with BET method.
The results of the above test data are shown in Table 1.
TABLE 1 Properties of catalysts prepared according to inventive examples and comparative examples
As can be seen from the test data in Table 1, the ammonium meta-tungstate prepared by the method and the denitration catalyst prepared by the subsequent preparation have better denitration efficiency, mechanical strength, abrasion strength, specific surface area and other performances, the denitration efficiency can reach more than 96%, the axial compression resistance and the radial compression resistance can respectively reach more than 4.5MPa and 0.90, the abrasion strength can be reduced to below 0.09%/kg, and the specific surface area can reach 62m 2 And/g. Wherein, the mechanical strength of the comparative example 1 without adopting the nanofiltration process is obviously lower than that of the examples 4-8 of the invention, the denitration efficiency is slightly lower than that of the examples 4-8 of the invention, which shows that the nanofiltration process further reduces the particle size of the ammonium metatungstate on the basis of improving the purity of the ammonium metatungstate, the mechanical strength of a denitration catalyst product can be improved by the small-particle ammonium metatungstate, and the denitration efficiency can be improved along with the improvement of the purity of the ammonium metatungstate; comparative example 2, which uses a nitric acid one-time leaching process, shows that the denitration efficiency is significantly lower than that of examples 4-8 of the present invention, indicating that the present invention is two nitric acid leaches, for WO 3 The conversion rate of the catalyst is improved to a certain extent, and the denitration efficiency of the denitration catalyst is improved accordingly; comparative example 3, where no surfactant was added, showed significantly lower abrasion performance than examples 4-8 of the present invention, demonstrating that the addition of a small amount of surfactant to pure water balances the TiO 2 The surface tension among the nano particles improves the abrasion strength of the catalyst product; comparative example 2, which does not employ ultrasonic technology, has a significantly lower specific surface area than examples 4-8 of the present invention, demonstrating that ultrasonic technology further breaks the titanium pigment mixture added, increasing the specific surface area of the catalyst.
In conclusion, the invention adopts a two-step method of nitric acid leaching reaction, then increases the nanofiltration process, improves the stirring paddle structure in the stirring tank of the system, and finally adds a small amount of surfactant in the method for preparing the catalyst, and combines the ultrasonic treatment process, so that the prepared denitration catalyst has high denitration efficiency, large specific surface area and better mechanical strength and abrasion strength performance.
The invention is not limited to the above-described embodiments, and a person skilled in the art may make various modifications thereto, but any equivalent or similar modifications as the invention are intended to be included within the scope of the claims of the present invention.
Claims (6)
1. The preparation method of the ammonium metatungstate used for the denitration catalyst is characterized by comprising the following steps: the method comprises the following steps:
s1, adding wet ammonium paratungstate into pure water with stirring, heating, adding a nitric acid solution, and filtering to obtain rare tungsten
An ammonium acid solution;
s2, standing and aging the dilute ammonium metatungstate solution, filtering to obtain filtrate I, pumping the filtrate I into a reaction kettle, heating and concentrating, and then continuously standing
Aging, and filtering by nanofiltration to obtain filtrate II;
s3, pumping the filtrate II into a reaction kettle, heating and concentrating, continuously standing, and filtering to obtain a concentrated ammonium metatungstate solution;
s4, crystallizing the concentrated ammonium metatungstate solution to obtain ammonium metatungstate used for a denitration catalyst;
the specific method for heating and adding the nitric acid solution in the step S1 is as follows:
s11, firstly heating to 60-70 ℃, adding nitric acid, and controlling the pH value of the solution to be 4.5-5.5;
s12, continuously heating to boiling, adding nitric acid, controlling the pH value of the solution to be 3-4, and obtaining the solution WO 3 When the content reaches 200-250g/L, boiling and stirring are carried out for more than 30 minutes.
2. The method for preparing ammonium metatungstate for a denitration catalyst according to claim 1, wherein:
heating and concentrating the solution in the step S2 until the specific gravity of the solution reaches 1.8-2.0;
and (3) heating and concentrating the solution until the specific gravity of the solution reaches 2.2-2.4.
3. A preparation system for ammonium metatungstate of denitration catalyst, characterized by: comprising the following steps: stirring tank, reaction kettle and filtration
Equipment, an aging tank, a crystallization tank and nanofiltration equipment; the ageing tank drain pipe is connected with the nanofiltration equipment liquid inlet pipe and is used for purifying the aged dilute ammonium metatungstate solution, the nanofiltration equipment drain pipe is connected with the reaction kettle liquid inlet pipe and is used for heating and concentrating the purified dilute ammonium metatungstate solution, and the stirring tank, the filtering equipment, the ageing tank a, the suction filter a, the reaction kettle a, the ageing tank b, the nanofiltration equipment, the reaction kettle b, the suction filter b and the crystallization tank are connected through pipelines in sequence;
the suction filter a comprises two stages of filter cloth, and the suction filter b comprises four stages of filter cloth;
the stirring tank is internally provided with stirring paddles which are divided into three layers, wherein the first layer is a net-shaped paddle, and the second layer is a hole-shaped paddle.
4. A denitration catalyst prepared by using the ammonium metatungstate produced by the production method according to claim 1 or 2, characterized in that: the method comprises the following steps:
(1) adding a surfactant into pure water, stirring, adding ammonium metatungstate, heating to boil, continuously adding titanium dioxide, mixing and carrying out ultrasonic treatment to obtain a mixture;
(2) and (3) sintering the mixture obtained in the step (1) at a high temperature to obtain the denitration catalyst.
5. The denitration catalyst as claimed in claim 4, characterized by: the surfactant in the step (1) is Tween, and the dosage is 0.1-0.5% of the weight of the ammonium metatungstate.
6. The denitration catalyst as claimed in claim 4 or 5, characterized in that:
the dosage of the ammonium metatungstate in the step (1) is 4-6% of the weight of the titanium dioxide;
the high-temperature sintering temperature in the step (2) is 800-1200 ℃.
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| CN101618893A (en) * | 2009-08-05 | 2010-01-06 | 江西稀有稀土金属钨业集团有限公司 | Method for preparing ammonium metawolframate |
| CN101928039A (en) * | 2010-09-29 | 2010-12-29 | 中南大学 | Method for preparing ammonium metatungstate |
| CN103318962A (en) * | 2013-03-25 | 2013-09-25 | 赣县安美特钨制品有限公司 | Production method for ammonium metatungstate |
| CN105727931A (en) * | 2016-03-17 | 2016-07-06 | 辽宁鑫隆科技有限公司 | Preparation method of low-temperature and non-toxic SCR denitration catalyst |
| CN108439472A (en) * | 2018-05-08 | 2018-08-24 | 江西铜鼓有色冶金化工有限责任公司 | A kind of method and system preparing the ammonium metatungstate for petroleum cracking catalyst |
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| CN101928039A (en) * | 2010-09-29 | 2010-12-29 | 中南大学 | Method for preparing ammonium metatungstate |
| CN103318962A (en) * | 2013-03-25 | 2013-09-25 | 赣县安美特钨制品有限公司 | Production method for ammonium metatungstate |
| CN105727931A (en) * | 2016-03-17 | 2016-07-06 | 辽宁鑫隆科技有限公司 | Preparation method of low-temperature and non-toxic SCR denitration catalyst |
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