阅读说明：本技术 一种scr脱硝催化剂及其制备方法 (SCR denitration catalyst and preparation method thereof ) 是由 吴光勇 赵延强 董俊杰 董殿英 于 2019-11-06 设计创作，主要内容包括：本发明公开了一种SCR脱硝催化剂及其制备方法；SCR脱硝催化剂包括纯钛白粉、七钼酸铵、5%钛白、硬脂酸、乳酸、氨水、去离子水、木浆、玻璃纤维、偏钒酸铵溶液(浓度为0.7%)、羧甲基纤维素和聚氧化乙烯；其制备方法为：溶解偏钒酸铵至氨水内、分批投料混炼、一次陈腐、过滤并预挤出、二次陈腐、挤出、干燥、烘焙和切割包装；本发明的SCR脱硝催化剂可用于对烟气的脱硝处理,其具有使用混合挤出法制备处所需的钼含量较高的催化剂的优点。(The invention discloses an SCR denitration catalyst and a preparation method thereof; the SCR denitration catalyst comprises pure titanium dioxide, ammonium heptamolybdate, 5% titanium dioxide, stearic acid, lactic acid, ammonia water, deionized water, wood pulp, glass fiber, ammonium metavanadate solution (the concentration is 0.7%), carboxymethyl cellulose and polyethylene oxide; the preparation method comprises the following steps: dissolving ammonium metavanadate into ammonia water, feeding and mixing in batches, carrying out primary ageing, filtering and pre-extruding, carrying out secondary ageing, extruding, drying, baking, cutting and packaging; the SCR denitration catalyst can be used for denitration treatment of flue gas, and has the advantage of preparing the catalyst with high molybdenum content by using a mixing extrusion method.)

1. The SCR denitration catalyst is characterized by being prepared from the following raw materials in parts by weight: 550 parts of pure titanium white powder, 30-35 parts of ammonium heptamolybdate, 95-105 parts of 5% titanium dioxide, 1-1.5 parts of stearic acid, 3.8-4.2 parts of lactic acid, 43-51 parts of ammonia water, 290 parts of deionized water, 3-4 parts of wood pulp, 35-40 parts of glass fiber, 5-10 parts of ammonium metavanadate solution (with the concentration of 0.7%), 1-2 parts of carboxymethyl cellulose and 5-8 parts of polyoxyethylene.

2. The SCR denitration catalyst according to claim 1, wherein 20 to 30 parts of cerium oxide is added to the raw material.

3. The SCR denitration catalyst according to claim 1, wherein 20 to 30 parts of kaolin is added to the raw material.

4. The method of preparing the SCR denitration catalyst according to any one of claims 1 to 3, characterized by comprising the steps of:

s1, dissolving: weighing the proportioned ammonium metavanadate and dissolving the ammonium metavanadate into NH₃Fully stirring the mixture in ammonia water with the content of 20 percent for later use;

s2, batch feeding and mixing: 300 parts of pure titanium white powder of 250-35 parts, 30-35 parts of ammonium heptamolybdate, 95-105 parts of 5% titanium white, 1-1.5 parts of stearic acid, 3.8-4.2 parts of lactic acid, 20-30 parts of cerium oxide, 20-30 parts of kaolin, 30-35 parts of ammonia water and 260 parts of deionized water are put into a high-speed mixer for mixing at normal temperature;

then, 100-110 parts of pure titanium dioxide and 17-20 parts of deionized water are put into a high-speed mixer for mixing together;

then, 130-140 parts of pure titanium dioxide and 5-6 parts of ammonia water are put into a high-speed mixer to be mixed together;

then 3-4 parts of wood pulp, 35-40 parts of glass fiber, 5-10 parts of ammonium metavanadate solution (0.7%) and 25-35 parts of deionized water are put into a high-speed mixer to be mixed together;

then 5-6 parts of ammonia water, 0.5-1 part of carboxymethyl cellulose and 2.5-4 parts of polyoxyethylene are put into a high-speed mixer to be mixed together;

finally, 3-4 parts of ammonia water, 8-12 parts of deionized water, 0.5-1 part of carboxymethyl cellulose and 2.5-4 parts of polyoxyethylene are put into a high-speed mixer to be mixed together;

s3, molding: firstly, performing one-time staling on the mixed powder; filtering, and putting into a pre-extruder for pre-extrusion;

secondly, performing secondary ageing on the pre-extruded powder; finally putting the mixture into an extruder for extrusion to obtain honeycomb-shaped squares;

s4, drying: firstly, placing honeycomb-shaped blocks on a frame and carrying out primary drying in a drying chamber;

after the primary drying is finished, feeding the honeycomb-shaped square blocks into a kiln for secondary drying;

s5, baking: feeding the dried honeycomb-shaped blocks into a mesh belt kiln for final baking;

s6, cutting and packaging: and cutting the baked and cooled honeycomb-shaped square blocks by a double-head cutting machine, and packaging.

5. The method of preparing the SCR denitration catalyst according to claim 4, wherein in the step S3, the time for the first ageing is 5 to 8 hours, and the time for the second ageing is 10 to 20 hours.

6. The method of preparing the SCR denitration catalyst as set forth in claim 4, wherein the extrusion speed of the extruder for extruding the honeycomb-shaped dice in the step S3 is 700-1000 mm/min.

7. The method of preparing the SCR denitration catalyst of claim 4, wherein in the step S4, a thermal drying method using water vapor as a heat source is used for primary drying, and the primary drying time is 8 to 12 days; the drying medium for the secondary drying is hot air, and the time for the secondary drying is 5-15 h.

8. The method of producing an SCR denitration catalyst according to claim 7, wherein in the step S4, water-soaked straw is laid on a hot steam pipe in a drying chamber that is primarily dried.

9. The method of claim 4, wherein in the step S5, the maximum calcination temperature is 600-620 ℃, and the calcination period is 30-35 h.

10. The method of claim 4, wherein in the step S6, the cut honeycomb briquette leftover is returned to the step S1 for recycling.

Technical Field

The invention relates to the technical field of flue gas denitration, in particular to an SCR denitration catalyst and a preparation method thereof.

Background

The temperature of the traditional SCR denitration technology is above 300 ℃, but a large amount of dust exists in the placement of the catalyst, so that the catalyst poisoning is very easy to occur, and the problem of the traditional SCR denitration technology is effectively solved because the temperature of the low-temperature SCR denitration technology is below 300 ℃; when the SCR denitration catalyst is used in a low-temperature condition, molybdenum element is often required to be added, so that the low-temperature performance of the catalyst is improved.

The existing production method of the honeycomb type low-temperature SCR denitration catalyst mainly comprises a coating method and a mixing extrusion method, wherein the coating method is to coat a granular catalyst on the surface of honeycomb ceramic, and then obtain the required catalyst through drying and roasting, but the catalyst has fewer active components; the mixing extrusion method is to add proper additives into the prepared granular catalyst and finally obtain the required catalyst through various working procedures.

However, the current catalysts with high molybdenum content are difficult to shape in the extrusion stage by using a hybrid extrusion method.

Disclosure of Invention

In view of the disadvantages of the prior art, a first object of the present invention is to provide an SCR denitration catalyst, which has the advantage that a catalyst with a high molybdenum content can be prepared by using a mixing extrusion method.

A second object of the present invention is to provide an SCR denitration catalyst and a method for preparing the same, which have the advantage of preparing a catalyst having a high molybdenum content by using a mixing extrusion method.

In order to achieve the first object, the invention provides the following technical scheme: an SCR denitration catalyst is prepared from the following raw materials in parts by weight: 550 parts of pure titanium white powder, 30-35 parts of ammonium heptamolybdate, 95-105 parts of 5% titanium dioxide, 1-1.5 parts of stearic acid, 3.8-4.2 parts of lactic acid, 43-51 parts of ammonia water, 290 parts of deionized water, 3-4 parts of wood pulp, 35-40 parts of glass fiber, 5-10 parts of ammonium metavanadate solution (with the concentration of 0.7%), 1-2 parts of carboxymethyl cellulose and 5-8 parts of polyoxyethylene.

By adopting the technical scheme, stearic acid is added into the SCR catalyst, so that the extrusion rate of the catalyst with high molybdenum content prepared by a mixed extrusion method is improved, and the failure rate of the catalyst mixed extrusion method is reduced; meanwhile, the low-temperature performance of the catalyst is improved by adding molybdenum.

Furthermore, 20-30 parts of cerium oxide is added into the raw materials.

By adopting the technical scheme, when cerium is doped, ammonium bisulfate and ammonium sulfate are generated on the surface of the catalyst when the temperature reaches 250 ℃, the cerium doping can improve the B acid position and the surface of the catalyst to adsorb oxygen, and cerium is combined with sulfur dioxide and water in flue gas to generate cerium sulfate salt, so that the generation of ammonium sulfate salt is inhibited; the cerium oxide has the effect of sulfur resistance of the SCR denitration catalyst.

Furthermore, 20-30 parts of kaolin is added into the raw materials.

By adopting the technical scheme, the kaolin is clay and claystone which mainly comprises kaolinite clay minerals, and the plasticity of the mixed extrusion molding of the SCR denitration catalyst can be improved by adding the kaolin into the SCR denitration catalyst.

In order to achieve the second object, the invention provides the following technical scheme: a method for preparing the SCR denitration catalyst according to any one of claims 1 to 3, comprising the steps of:

s1, dissolving: weighing the proportioned ammonium metavanadate and dissolving the ammonium metavanadate into NH₃Fully stirring the mixture in ammonia water with the content of 20 percent for later use;

s2, batch feeding and mixing: 300 parts of pure titanium white powder of 250-35 parts, 30-35 parts of ammonium heptamolybdate, 95-105 parts of 5% titanium white, 1-1.5 parts of stearic acid, 3.8-4.2 parts of lactic acid, 20-30 parts of cerium oxide, 20-30 parts of kaolin, 30-35 parts of ammonia water and 260 parts of deionized water are put into a high-speed mixer for mixing at normal temperature;

then, 100-110 parts of pure titanium dioxide and 17-20 parts of deionized water are put into a high-speed mixer for mixing together;

then, 130-140 parts of pure titanium dioxide and 5-6 parts of ammonia water are put into a high-speed mixer to be mixed together;

then 3-4 parts of wood pulp, 35-40 parts of glass fiber, 5-10 parts of ammonium metavanadate solution (0.7%) and 25-35 parts of deionized water are put into a high-speed mixer to be mixed together;

then 5-6 parts of ammonia water, 0.5-1 part of carboxymethyl cellulose and 2.5-4 parts of polyoxyethylene are put into a high-speed mixer to be mixed together;

finally, 3-4 parts of ammonia water, 8-12 parts of deionized water, 0.5-1 part of carboxymethyl cellulose and 2.5-4 parts of polyoxyethylene are put into a high-speed mixer to be mixed together;

s3, molding: firstly, performing one-time staling on the mixed powder; filtering, and putting into a pre-extruder for pre-extrusion;

secondly, performing secondary ageing on the pre-extruded powder; finally putting the mixture into an extruder for extrusion to obtain honeycomb-shaped squares;

s4, drying: firstly, placing honeycomb-shaped blocks on a frame and carrying out primary drying in a drying chamber;

after the primary drying is finished, feeding the honeycomb-shaped square blocks into a kiln for secondary drying;

s5, baking: feeding the dried honeycomb-shaped blocks into a mesh belt kiln for final baking;

s6, cutting and packaging: and cutting the baked and cooled honeycomb-shaped square blocks by a double-head cutting machine, and packaging.

By adopting the technical scheme, the raw materials can be mixed more uniformly by batch feeding and mixing of the different components in parts by weight, and then, the step of pre-extrusion is added in the aging and extrusion process, so that the extrusion effect in the final extrusion is improved, and the failure rate of extrusion is reduced; the drying steps of different methods with different temperatures are adopted in the drying process, so that the cracking condition of the extruded honeycomb-shaped blocks under the action of high temperature is reduced, and the final yield is improved.

Further, in the step S3, the time for the first ageing is 5-8 hours, and the time for the second ageing is 10-20 hours.

By adopting the technical scheme, the pre-extrusion is carried out after the first-time staling, the staling time is short, the pre-extrusion is still powder, and then the extrusion is carried out after the second-time staling, so that the success rate of extrusion molding can be improved.

Further, in the step S3, the extrusion speed of the extruder for extruding the honeycomb-shaped dice is 700-1000 mm/min.

By adopting the technical scheme, the extrusion rate of the extruder is controlled, and the extrusion yield is improved under the condition of ensuring the extrusion rate.

Further, in the step S4, the primary drying adopts a thermal drying method using water vapor as a heat source, and the primary drying time is 8 to 12 days; the drying medium for the secondary drying is hot air, and the time for the secondary drying is 5-15 h.

By adopting the technical scheme, the moisture in the honeycomb type square block is slowly dried in a hot steam mode through primary drying at a lower temperature for the first time, and secondary drying at a higher temperature is carried out for the second time after most of water vapor in the honeycomb type square block is dried, so that the final drying step is completed; by dividing the drying into two steps, the water vapor in the honeycomb type square blocks can be removed in a progressive mode, and the condition that the honeycomb type square blocks are cracked caused by high-temperature quick removal is reduced.

Further, in the step S4, the rice straw soaked with water is spread on a hot steam pipe in a drying chamber for primary drying.

By adopting the technical scheme, the rice straws soaked in water are laid on the hot steam pipe, so that the instant drying and cracking caused by the fact that steam is directly sprayed on the honeycomb type square blocks when the hot steam pipe is used for drying the honeycomb type square blocks by hot steam can be reduced, the hot steam is piled up through the soaked rice straws to play a role in buffering, and the drying and cracking of the honeycomb type square blocks are reduced.

Further, in the step S5, the maximum roasting temperature is 600-620 ℃, and the time of the roasting stage is 30-35 h.

By adopting the technical scheme, the roasting can be carried out by four steps of heating, roasting, reheating and roasting, and the temperature rise is carried out by two times, so that the condition that the honeycomb type square blocks crack when the temperature is too high can be reduced.

Further, in the step S6, the scrap after cutting the honeycomb-shaped dice can be returned to the step S1 for recycling.

By adopting the technical scheme, the cut crushed aggregates are returned to the step S1 again for recycling, the utilization rate of materials is improved, and the production cost is reduced.

In conclusion, the invention has the following beneficial effects:

firstly, because the invention adopts batch feeding and mixing and adds a pre-extrusion step before extrusion, the effect of preparing the catalyst with high molybdenum content by using a mixing extrusion method through adding stearic acid is achieved.

Secondly, the drying method of primary drying and secondary drying is preferably adopted in the invention, the moisture in the honeycomb type square block is slowly dried in a hot steam mode through primary drying with lower temperature for the first time, and secondary drying with higher temperature for the second time is carried out after most of the moisture in the honeycomb type square block is dried, so that the final drying step is completed; by dividing the drying into two steps, the water vapor in the honeycomb type square blocks can be removed in a progressive mode, and the condition that the honeycomb type square blocks are cracked caused by high-temperature quick removal is reduced.

Detailed Description

The present invention will be described in further detail with reference to examples.