CN112546748B - Preparation method of low-temperature denitration filter material based on water quenching method - Google Patents

Abstract

The invention relates to the technical field of industrial boiler flue gas purification, in particular to a preparation method of a low-temperature denitration filter material based on a water quenching method. Firstly, mixing and stirring vanadium pentoxide powder, an organic modifier and cerous nitrate hexahydrate uniformly to prepare low-temperature denitration catalyst precursor emulsion; adding the low-temperature denitration catalyst precursor emulsion into a reaction kettle, and placing the filter cloth into the reaction kettle to be soaked in vacuum; finally, drying the soaked filter cloth, and calcining at a medium temperature to obtain a low-temperature denitration filter material; adding deionized water into a reaction kettle, heating and melting vanadium pentoxide powder, quickly pouring the heated and melted vanadium pentoxide powder into the deionized water, and ultrasonically stirring and dissolving; adding an organic modifier into the solution, fully stirring and uniformly mixing to obtain a stable vanadium pentoxide emulsion; and finally, adding cerous nitrate hexahydrate powder into the solution, and stirring until the cerous nitrate hexahydrate powder is completely dissolved to obtain the low-temperature denitration catalyst precursor emulsion.

Description

A method for preparing low-temperature denitration filter material based on water quenching method

Technical Field

The invention relates to the technical field of industrial boiler flue gas purification, and in particular to a method for preparing a low-temperature denitration filter material based on a water quenching method.

Background Art

In recent years, my country's industrialization level has increased rapidly, which has also aggravated environmental problems such as worsening air pollution and excessive PM2.5. Although corresponding environmental protection policies have been implemented, the atmospheric environment is still very severe. Among them, the flue gas produced by the combustion of industrial boilers contains a large amount of nitrogen oxides, sulfur dioxide and smoke, which, if directly discharged into the environment, will seriously threaten human health. Therefore, how to further reduce the content of pollutants in the flue gas of industrial boilers and improve the cleanliness of industrial boilers is still a problem that needs to be solved urgently.

Since the exhaust temperature of industrial boilers is relatively low, if the denitration and dust removal process of power station boilers is directly adopted, there will be a large difference between the denitration temperature and the dust removal temperature, resulting in low denitration efficiency and other problems. Filter bag denitration is a new flue gas denitration technology. With the help of a filter bag with catalytic function and a bag dust removal process, flue gas denitration is achieved at low temperature. This technology has been widely used in foreign industrial boilers. Since vanadium cerium-based catalysts have good low-temperature activity, the existing low-temperature denitration filter material preparation process usually adopts an impregnation method to dissolve the vanadium precursor (ammonium metavanadate) in dilute sulfuric acid to prepare a denitration solution, and then immerse the filter cloth in the solution and calcine it at about 500°C. The above method has poor dispersibility of the denitration active components, weak bonding between the catalyst and the filter bag fiber, reduced fiber strength of the filter cloth, and affected the service life of the filter cloth. Therefore, it is particularly necessary and important to develop a new denitration filter bag preparation technology.

Summary of the invention

In view of the problems existing in the prior art, the present invention provides a method for preparing a denitrification filter bag based on a water quenching method. The denitrification active components have good dispersibility, which effectively improves the fiber strength of the filter cloth, ensures the service life of the filter cloth, and strengthens the bonding force between the catalyst and the filter cloth fiber.

The present invention is achieved through the following technical solutions:

A method for preparing a low-temperature denitration filter material based on a water quenching method comprises the following steps:

Step 1, mixing vanadium pentoxide powder, an organic modifier and cerium nitrate hexahydrate powder and stirring them uniformly to prepare a low-temperature denitration catalyst precursor emulsion;

Step 2, adding a low-temperature denitration catalyst precursor emulsion into a reactor, and placing a filter in the reactor and soaking it under vacuum;

Step 3, drying the soaked filter cloth, and calcining at medium temperature to obtain a low-temperature denitration filter material.

Furthermore, in step 1, the preparation method of the low-temperature denitration catalyst precursor emulsion is as follows:

Step 1.1, add deionized water to a reactor, heat and melt the vanadium pentoxide powder, then quickly pour it into the deionized water and stir and dissolve it by ultrasonic stirring;

Step 1.2, adding an organic modifier to the solution obtained in step 1.1, stirring and mixing thoroughly to obtain a stable vanadium pentoxide emulsion;

Step 1.3, adding cerium nitrate hexahydrate powder to the solution obtained in step 1.2, stirring until completely dissolved to obtain a low-temperature denitration catalyst precursor emulsion.

Furthermore, in step 1.1, when heating to melt, the temperature is 800°C to 900°C; the water-vanadium ratio is 30mL/g to 35mL/g; and the temperature range of deionized water is 25°C to 30°C.

Furthermore, in step 1.1, during ultrasonic stirring for dissolution, the stirring speed is 100 r/min.

Furthermore, in step 1.2, the organic modifier is a polyimide emulsion with a mass concentration of 20%, accounting for 3% to 8% of the mass of the entire catalyst precursor emulsion. After being added to the solution, the stirring speed is 60 r/min.

Furthermore, in step 1.3, the mass ratio of cerium nitrate hexahydrate to vanadium pentoxide is 2:1, and after being added into the solution, the stirring speed is 10 r/min to 15 r/min.

Furthermore, in step 2, the filter cloth is a polyimide fiber filter cloth, which is vacuum impregnated in a reaction kettle, the vacuum degree is maintained at 0.05MPa to 0.1MPa, the temperature is controlled at 58°C to 60°C, and the time is at least 3h.

Furthermore, in step 3, the soaked filter cloth is transparent, first dried at room temperature, then dried in an oven at 130°C until the entire filter cloth turns black, and finally the black filter cloth is calcined in a muffle furnace at 240°C for 4 hours to obtain a low-temperature denitration filter material.

Compared with the prior art, the present invention has the following beneficial technical effects:

The present invention adopts a water quenching method to prepare liquid vanadium pentoxide, adds an organic modifier and hexahydrate cerium nitrate powder thereto, and finally obtains a low-temperature denitration catalyst precursor emulsion; then the filter cloth is immersed in the emulsion under negative pressure conditions, and after calcination, the low-temperature denitration catalyst is loaded on the polyimide fiber filter cloth to prepare a low-temperature denitration filter material. Different from the traditional method for preparing a low-temperature denitration catalyst precursor emulsion, the technical engineering implementation of the present invention requires heating to 800°C to 900°C, keeping warm for 1h, and then quickly pouring into deionized water to prepare a uniform vanadium pentoxide aqueous solution, and then adding polyimide emulsion and hexahydrate cerium nitrate to it to prepare a low-temperature denitration catalyst precursor emulsion. The catalyst precursor emulsion has a high degree of stability, is not sensitive to temperature, and can be maintained for more than one year. Among them, the polyimide emulsion as an organic modifier can significantly improve the stability of the vanadium pentoxide solution, and can also be used as a binder to increase the loading rate of the active component on the filter cloth, and can be reused, which greatly improves the economy and is convenient for industrial large-scale production and promotion and application.

Furthermore, the present invention soaks the filter cloth in the catalyst precursor emulsion under vacuum conditions, which is beneficial for the active components to enter the micropores of the filter cloth, further improving the loading rate and uniformity of the active components of the catalyst.

Furthermore, the present invention only needs to calcine the filter cloth loaded with the denitration catalyst precursor at about 240°C, and there is no need to roast it at a high temperature of 500°C, thereby avoiding the problem of spontaneous combustion of the filter cloth and generation of a large amount of polluting gas due to high-temperature roasting, and the problem of salting out of the active components in the catalyst precursor emulsion on the surface of the filter cloth, thereby reducing the requirement for high temperature resistance of the raw filter cloth, and effectively reducing the production cost of the filter bag.

DETAILED DESCRIPTION

The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

The present invention discloses a method for preparing a denitration filter material based on a water quenching method. The method comprises the following steps: preparing liquid vanadium pentoxide by a water quenching method, adding an organic modifier and an auxiliary agent thereto, and finally obtaining a low-temperature denitration catalyst precursor emulsion; then, immersing a filter cloth in the low-temperature denitration catalyst precursor emulsion under negative pressure conditions, calcining at 240° C., and loading the low-temperature denitration catalyst on a polyimide fiber filter cloth to prepare a low-temperature denitration filter material. The specific steps are as follows:

(1) Add deionized water to a reaction kettle, heat and melt the vanadium pentoxide powder, and then quickly pour it into the deionized water and dissolve it by ultrasonic stirring.

(2) Add an organic modifier to the above solution, stir and mix thoroughly to obtain a stable vanadium pentoxide emulsion.

(3) Add cerium nitrate hexahydrate powder to the above solution and stir until completely dissolved to obtain a low-temperature denitration catalyst precursor emulsion.

(4) Place the filter in the reactor and use a vacuum pump to maintain negative pressure in the reactor.

(5) Drying the soaked filter cloth and calcining it at medium temperature to obtain a low-temperature denitration filter material.

Among them, (1), (2) and (3) are steps for preparing a low-temperature denitration catalyst precursor emulsion, which is made of vanadium pentoxide powder, cerium nitrate hexahydrate and an organic modifier;

Wherein, in step (1), the vanadium pentoxide powder is heated to 800°C to 900°C, kept warm for 1 hour, and then quickly poured into deionized water. Wherein, the water-vanadium ratio is 30mL/g to 35mL/g, and the temperature is maintained at 25°C to 30°C. The reactor agitator is stirred at a speed of 100r/min for 1 hour;

Wherein, in step (2), the organic modifier is a polyimide emulsion, and its mass concentration is 20%, accounting for 3% to 8% of the low-temperature denitration catalyst precursor emulsion. After addition, the stirring speed is 60r/min, and the stirring time is 30h;

Wherein, in step (3), the mass ratio of cerium nitrate hexahydrate to vanadium pentoxide is 2:1. After adding cerium nitrate hexahydrate, stir thoroughly at a speed of 10 r/min to 15 r/min for 30 min;

Wherein, in step (4), the vacuum degree in the reactor is maintained at 0.05 MPa to 0.1 MPa, the filter cloth is immersed in the reactor for 1 h to 2 h, and the temperature is controlled at about 60° C.;

Wherein, in step (5), after taking out the filter cloth, first dry it at room temperature for 12 hours, then dry it in an oven at 130° C. for 2 hours to 3 hours, and finally calcine it in a muffle furnace at 240° C. for 4 hours to obtain a low-temperature denitration filter material;

In practical applications, when preparing low-temperature denitration filter material using the method provided by the present invention, the following steps are included:

First, weigh an appropriate amount of vanadium pentoxide powder, put it into a tongs pot, heat it to 800°C to 900°C in a muffle furnace, and keep it warm for 1 hour to obtain vanadium pentoxide in a molten state;

Add deionized water to the reactor, with a water-vanadium ratio of 30 mL/g to 35 mL/g, and quickly pour the vanadium pentoxide obtained in step (1) into the deionized water and stir immediately. The solution in the reactor is controlled at 25°C to 30°C, the stirring blade speed is 100 r/min, and the stirring time is 1 hour;

Then add 20% polyimide emulsion to the above solution and stir it evenly. The stirring speed of the reactor is 60r/min and the stirring time is 30min to obtain a stable vanadium pentoxide emulsion. The polyimide emulsion accounts for 3% to 8% of the mass of the entire catalyst precursor emulsion.

Then, add cerium nitrate hexahydrate to the above-mentioned vanadium pentoxide emulsion, stir at a speed of 10 r/min to 15 r/min, and stir for 30 min to finally obtain a low-temperature denitration catalyst precursor emulsion. The mass ratio of cerium nitrate hexahydrate to vanadium pentoxide is 2:1;

Next, the polyimide filter cloth is immersed in the low-temperature denitration catalyst and precursor emulsion in step (4), and the reactor is sealed. The reactor is evacuated using a vacuum maintenance pump. The polytetrafluoroethylene filter cloth is immersed in a vacuum degree of 0.05 MPa to 0.1 MPa and a temperature of 58° C. to 60° C. for 1 h to 2 h.

Finally, spread the transparent filter cloth on a drying net and dry it at room temperature for 12 hours until the surface of the filter cloth is dry. Then dry it in a 130℃ oven until the entire filter cloth turns black, which takes about 2 to 3 hours. Finally, calcine it in a muffle furnace at 240℃ for 4 hours to obtain a low-temperature denitrification filter material.

The obtained low-temperature denitrification filter material was used to evaluate the denitrification performance using simulated flue gas on a test bench. The concentrations of NO and _NO2 in the flue gas at the inlet and outlet of the reactor were tested using a flue gas analyzer to calculate the _NOx removal efficiency.

Example 1

In this embodiment, a water-vanadium ratio of 30 mL/g, a vanadium pentoxide heating temperature of 800°C, a deionized water temperature of 25°C, a polyimide emulsion content of 3%, and a vacuum degree of 0.05 MPa are used for specific description, and the low-temperature denitration filter material obtained under these conditions is evaluated for denitration performance using simulated flue gas on a test bench, that is, the NO and _NO2 concentrations in the reactor inlet and outlet flue gas are tested with a flue gas analyzer, and the _NOx removal efficiency is calculated to be 82%.

Under the above parameter conditions, the specific preparation process is as follows:

(1) Weigh an appropriate amount of vanadium pentoxide powder, put it into a tongs pot, heat it to 800°C in a muffle furnace, and keep it warm for 1 hour to obtain vanadium pentoxide in a molten state.

(2) Add deionized water to the reactor, with a water-vanadium ratio of 30 mL/g, and quickly pour the vanadium pentoxide obtained in step (1) into the deionized water, and stir immediately. The solution in the reactor is controlled at 25° C., the stirring blade speed is 100 r/min, and the stirring time is 1 h.

(3) Adding a polyimide emulsion with a mass concentration of 20% to the solution of step (2), stirring the mixture evenly, stirring the mixture at a stirring speed of 60 r/min for 30 min, and obtaining a stable vanadium pentoxide emulsion. The polyimide emulsion accounts for 3% of the mass of the catalyst precursor emulsion.

(4) adding cerium nitrate hexahydrate to the vanadium pentoxide emulsion in step (3), stirring at a speed of 10 r/min for 30 min, and finally obtaining a low-temperature denitration catalyst precursor emulsion. The mass ratio of cerium nitrate hexahydrate to vanadium pentoxide is 2:1.

(5) Immerse the polyimide filter cloth in the low-temperature denitration catalyst precursor emulsion obtained in step (4), and seal the reactor. Use a vacuum maintenance pump to evacuate the reactor. Immerse the polytetrafluoroethylene filter cloth at a vacuum degree of 0.05 MPa and a temperature of 58° C. to 60° C. for 1 h to 2 h.

(6) Spread the transparent filter cloth after soaking on a drying net and dry it at room temperature for 12 hours until the surface of the filter cloth is dry. Then dry it in a 130℃ oven until the entire filter cloth turns black, which takes about 2 to 3 hours. Finally, calcine it in a muffle furnace at 240℃ for 4 hours to obtain a low-temperature denitrification filter material.

The preparation parameters and _NOx removal efficiency of Examples 1 to 10 are shown in the following table. The preparation process is the same as that of Example 1, except for the different preparation parameters.

Claims (1)

1. A method for preparing a low-temperature denitration filter material based on a water quenching method, characterized in that it comprises the following steps: Step 1, vanadium pentoxide powder, an organic modifier and cerium nitrate hexahydrate powder are mixed and ultrasonically stirred to uniformly prepare a low-temperature denitration catalyst precursor emulsion; the stirring speed is 100 r/min; Step 2, adding the low-temperature denitration catalyst precursor emulsion into the reactor, and placing the polyimide fiber filter in the reactor for vacuum impregnation under negative pressure conditions, maintaining the vacuum degree at 0.05MPa to 0.1MPa, and controlling the temperature at 58°C to 60°C for at least 3h; Step 3, drying the soaked filter cloth, and calcining at medium temperature to obtain a low-temperature denitration filter material; the soaked filter cloth is transparent, first dried at room temperature, then dried in an oven at 130°C until the entire filter cloth turns black, and finally calcining the black filter cloth in a muffle furnace at 240°C for 4 hours to obtain a low-temperature denitration filter material; In step 1, the preparation method of the low-temperature denitration catalyst precursor emulsion is as follows: Step 1.1, adding deionized water to a reaction kettle, heating and melting vanadium pentoxide powder, and then quickly pouring it into deionized water, stirring and dissolving it by ultrasonic stirring; when heating and melting, the temperature is 800°C to 900°C, and the temperature is kept for 1 hour; the water-vanadium ratio is 30mL/g to 35mL/g; the temperature range of deionized water is 25°C to 30°C; Step 1.2, adding a polyimide emulsion with a mass concentration of 20% to the solution obtained in step 1.1, wherein the polyimide emulsion accounts for 3% to 8% of the mass of the entire catalyst precursor emulsion. After adding the polyimide emulsion to the solution, the stirring speed is 60 r/min, and the mixture is fully stirred and mixed to obtain a stable vanadium pentoxide emulsion; Step 1.3, adding cerium nitrate hexahydrate powder to the solution obtained in step 1.2, the mass ratio of cerium nitrate hexahydrate to vanadium pentoxide is 2:1, stirring speed is 10r/min~15r/min, stirring until completely dissolved to obtain a low-temperature denitration catalyst precursor emulsion.