CN111551031A - A tube furnace test system and method for catalytic oxidation of CO in coal-fired flue gas - Google Patents

Abstract

The invention relates to a system and a method for testing a tubular furnace for catalytic oxidation of CO in coal-fired flue gas, wherein the system comprises a gas distribution system, a vacuumizing system, a temperature control device, a cooling system, a vertical furnace body, a hearth heat-insulating layer arranged in the furnace body and a reaction tube arranged in a hearth, wherein the vacuumizing system is arranged above the furnace body; the hearth heat-insulating layer is arranged in multiple layers, and a cooling passage for cooling medium circulation is arranged between two adjacent layers; the temperature measuring end and the heating end of the temperature control device are both arranged in the hearth; the cooling system is used for cooling the circulation of a cooling medium, the output end of the cooling system is connected with the input end of the cooling passage, and the input end of the cooling system is connected with the output end of the cooling passage; the reaction tube is internally provided with a supporting layer, the input end of the reaction tube is connected with a gas distribution system and a vacuum pumping system which are connected in parallel, and the output end of the reaction tube is connected with an analysis absorption system. According to the method, a hearth is heated and controlled to reach a target temperature in an oxygen-free vacuum environment, and after an oxidation-reduction reaction occurs when input gas passes through a catalyst, main component analysis and waste gas absorption treatment are performed.

Description

A tube furnace test system and method for catalytic oxidation of CO in coal-fired flue gas

technical field

The invention relates to the technical field of flue gas nitrogen oxide pollutant removal, in particular to a tube furnace test system and method for catalytic oxidation of CO in coal combustion flue gas.

Background technique

Coal-fired power plants emit a large amount of nitrogen oxides (NO _x ) in the production process. The NO _x emission limit for newly built units is required to reach 50mg/m ³ . The core of controlling nitrogen oxide emissions from coal-fired power plants is flue gas denitrification technology. Tauster and Murrell first proposed the research idea of using CO to selectively catalyze NO reduction. Ir, Pt, Pd and other noble metal elements have certain denitration performance in the oxygen-enriched state. The research of Spassova et al. It has a catalytic synergistic effect _on Al ₂ O ₃ and can improve the catalytic activity _of the catalyst at low temperature. At 300 ℃, all have certain denitrification performance in CO atmosphere.

At present, the denitration catalytic reaction under catalytic conditions can be studied through the thermal test of the small gas distribution quartz tube. However, the existing vertical tube furnaces are usually simple in structure, and because of the difficulty of processing quartz tubes, only one quartz light tube is usually provided as the reaction tube of the tube furnace. For the requirement to be filled with catalyst, the existing quartz tubes are often unable to meet the requirements, and the directly purchased tube furnace is not equipped with a structure to support the catalyst. In addition, the cooling process of ordinary tube furnaces adopts natural cooling, or a cooling system is installed in the extension section of the reaction tube, but whether it is a corundum tube or a quartz tube, rapid cooling in the high temperature test range of 1000 ° C - 1600 ° C is not tolerated. . Therefore, the common commercial tube furnace is limited by the space in the furnace and the reaction temperature range, and the quartz tube structure in the furnace is difficult to meet the needs of many different reaction conditions.

SUMMARY OF THE INVENTION

Aiming at the problems existing in the prior art, the present invention provides a tube furnace test system and method for catalytic oxidation of CO in coal-fired flue gas, which has the advantages of simple structure, convenient use, low cost, convenient transformation and obvious effect, and is suitable for rapid screening of different Screening of catalysts for catalytic oxidation of CO under the atmosphere of coal-fired flue gas with high concentration.

The present invention is achieved through the following technical solutions:

A tube furnace test system for catalytically oxidizing CO in coal-fired flue gas includes a gas distribution system, a vacuum pumping system, a temperature control device and a cooling system, a furnace body with a vertical structure, and a furnace heat preservation layer arranged in the furnace body, A reaction tube arranged in the furnace;

The furnace insulation layer is arranged in multiple layers, and a cooling passage for cooling medium circulation is arranged between two adjacent layers;

The temperature measuring end and the heating end of the temperature control device are all arranged in the furnace;

The cooling system is used for circulating cooling of the cooling medium, the output end is connected to the input end of the cooling passage, and the input end is connected to the output end of the cooling passage;

The reaction tube is provided with a support layer, the input end is connected to the parallel gas distribution system and the vacuum pumping system, and the output end is connected to the analysis and absorption system.

Preferably, two reaction tubes arranged in parallel in the furnace form a group, the support layer in one reaction tube is loaded with catalyst, and the support layer in the other reaction tube is not loaded with catalyst; the two reaction tubes are connected in parallel, and the input ends are connected in parallel The gas distribution system and the vacuum pumping system are connected to the analysis and absorption system at the output end.

Preferably, the support layer is arranged in a disc shape, and the edges are symmetrically arranged with grooves.

Preferably, both ends of the reaction tube extend out of the furnace body through flange sealing, and a cooling device is provided at the end of the reaction tube extending out of the furnace body.

Preferably, the gas distribution system includes a gas premixing device, and the test gas cylinders are respectively connected in parallel to the input end of the gas premixing device, and are sequentially connected to the tube furnace inlet valve and the air inlet flowmeter at the output end of the gas premixing device;

The test gas cylinders include N ₂ gas cylinders, CO gas cylinders, O ₂ gas cylinders and CO ₂ gas cylinders, and the test gas cylinders are connected to the input end of the gas premixing device through their corresponding gas valves and gas distribution flowmeters. .

Preferably, the analysis and absorption system includes a CO\CO ₂ analyzer and a gas absorption bottle sequentially connected to the output end of the reaction tube.

Preferably, the analysis and absorption system includes a gas absorption bottle connected to the output end of the reaction tube, and a gas sampling tube arranged between the output end of the reaction tube and the gas absorption bottle.

Preferably, the reaction tube is made of quartz reaction tube or corundum reaction tube, and the support layer is made of ceramic sand core, quartz wool, quartz sand board or quartz wool board.

A test method for a tube furnace for catalytic oxidation of CO in coal-fired flue gas, based on the system described in any one of the above schemes, comprising the following steps:

In step 1, the oxygen in the reaction tube and the system is discharged through the vacuum system, and the protective gas is filled;

In step 2, the furnace chamber is heated and controlled by the temperature control device, and the target temperature is reached through the temperature control device. When the gas input by the gas distribution system passes through the catalyst, an oxidation-reduction reaction occurs, and then leaves the tube furnace, and the analysis and absorption system is used to analyze and analyze the main components. Waste gas absorption treatment.

Preferably, in each test, the N ₂ provided by the N ₂ gas cylinder is used as the protective gas for excluding oxygen, and the corresponding gases provided by the N ₂ gas cylinder, the CO gas cylinder, the O ₂ gas cylinder and the CO ₂ gas cylinder are mixed. get mixed gas;

The mixed gas entering the tube furnace is divided into two paths, which respectively pass through the reaction tube without catalyst and the reaction tube loaded with catalyst; during data processing in the analysis, the data collected from the reaction tube without catalyst is used as a control.

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

By setting a cooling system on the thermal insulation layer, the invention can extend the cooling effect of the reaction tube, which can meet the requirements of the experiment with many changing working conditions and the need to speed up the cooling process. It not only avoids the cooling of the reaction tube and causes damage to the reaction tube during the quenching process, but also achieves the purpose of cooling. While saving the time for sampling and changing samples, it also ensures the normal operation of the test system. It is widely used in the test phase of catalytic removal of flue gas pollutants in coal-fired power plants.

Further, by setting up two reaction tubes, the temperature difference between the mixed gas entering the high temperature tube furnace from low temperature is eliminated, resulting in the change of gas composition, resulting in measurement error and ensuring the authenticity and accuracy of the data. Therefore, while ensuring the catalytic oxidation of CO by the catalyst in the coal-fired flue gas atmosphere, the system of the present invention can simply compare and screen out the catalyst with the best denitration effect in the test atmosphere, so as to achieve the purpose of denitration.

Description of drawings

FIG. 1 is a schematic diagram of the system structure of the present invention.

FIG. 2 is a schematic diagram of a system for direct treatment of the outlet gas of the tube furnace after sampling in the present invention.

FIG. 3 is a front view of the structure of the support layer quartz wool board in the present invention.

FIG. 4 is a schematic cross-sectional structural diagram of a support layer quartz wool board in the present invention.

In the picture: 1-N ₂ gas cylinder, 2-CO gas cylinder, 3-O ₂ gas cylinder, 4-CO ₂ gas cylinder, 5-gas valve, 6-gas distribution flowmeter, 7-gas premixing device, 8 -Inlet valve, 9-Inlet flow meter, 10- Vacuum system, 11- Furnace body, 12- Support layer, 13- Furnace insulation layer, 14- Temperature control device, 15- Cooling system, 16-CO\CO ₂ analyzer, 17-gas absorption bottle, 18-gas sampling tube, 19-reaction tube, 20-flange, 21-groove, 22-quartz wool board.

Detailed ways

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

The present invention takes the catalytic oxidation reaction pathway of CO in the flue gas of the coal-fired power plant as the research object, and the adopted tubular furnace is a vertical structure, including a furnace body 11, a furnace heat preservation layer 13 and a reaction tube 19; Gas premixing device 7, vacuuming system 10, support layer 12, temperature control device 14, cooling system 15, CO/CO ₂ analyzer 16; tube furnace preferably adopts quartz tube furnace.

The gas distribution system adjusts the gas composition through the gas valve of each gas cylinder, and then enters the reaction tube 19 of the tubular furnace after premixing by the gas premixing device 7, and reacts through the catalyst on the support layer 12 in the reaction tube 19, Finally out of the tube furnace.

The purpose of evacuating the tube furnace is to discharge the oxygen in the furnace as much as possible and eliminate the possibility that the oxygen concentration in the air will participate in the redox reaction in the reaction tube 19 . First, close all valves on the vacuum pumping system 10, open the vacuum pump and vacuum valve on the vacuum pumping system 10, observe that the pressure is expressed to a certain degree of vacuum (eg -0.1MPa) and stabilized, then close the vacuum valve and vacuum pump; open the vacuum pumping system 10 The _N2 gas cylinder and the intake valve in the gas distribution system connected to the above, wait until the pressure gauge returns to normal pressure, then close the intake valve, at this time, the air concentration in the tube furnace 11 decreases. Repeat this step for many times, and finally the air is exhausted to obtain a high-purity test atmosphere. After vacuuming, close the vacuum valve first, and then close the vacuum pump to avoid the backflow of air when the vacuum pump is not working. For the CO catalytic oxidation process in the coal-fired flue gas atmosphere, and the sintering process of additives or catalysts in the high-temperature pumpable atmosphere, micro-positive pressure is usually used in normal work, such as less than 0.02MPa.

The furnace body insulation layer 13 of the present invention adopts a three-layer structure, and a refrigerating cooling medium is respectively provided between each two insulation layers, and the cooling medium is provided by the cooling system 15. The cooling medium can enter from one end of the top of the furnace body 11 and come out from the other end of the top of the furnace body 11 . The temperature rise of the surface of the furnace body 11 can be effectively controlled to be less than 30°C, so as to achieve the purpose of rapidly cooling the surface of the furnace body, so as to meet the requirements of changing working conditions under multiple working conditions in the test system. The furnace body is provided with an air outlet at the top. The furnace heat preservation layer 13 can be made of commercial alumina polycrystalline fiber material, which is formed by vacuum adsorption mature in the prior art, with small shrinkage rate and low thermal conductivity, and can achieve a good heat preservation effect. It can also be composed of thermal insulation materials such as alumina felt cloth and thermal insulation cotton. The heating of the furnace is regulated by a temperature control device 14, which is commercially available. For example, the molybdenum-containing iron-chromium-aluminum resistance wire material can reach a maximum of 1100°C. A K-type thermocouple is arranged in the middle of the furnace body, which is controlled by the temperature control device 14 . It is suitable for temperature test with atmosphere less than 1300℃.

The reaction tube 19 is made of quartz material. There are many kinds of quartz glass, its softening point temperature is about 1730℃, it can be used for a long time at about 1100℃, and the maximum use temperature can reach 1400℃ in a short time, which can be used as the material of high temperature reaction tube.

Because the material of the quartz reaction tube is difficult to process and knead into other structures. Therefore, a catalyst support needs to be arranged in the reaction tube, and the material can be selected from ceramic sand core, quartz wool, quartz sand board, and the like. For example, the quartz wool board 22 made of quartz fiber cotton felt has the advantages of high temperature resistance, corrosion resistance, dimensional stability, minimal elongation and shrinkage, and high strength. The resistance is small, and it is a high-efficiency high-temperature material, which can be used as a high-temperature-resistant thermal insulation material and a high-temperature catalyst carrier. The quartz wool plate 22 is processed into a support member with a symmetrical groove 21 structure, and a quartz wool plate 22 with a certain thickness is used to clamp the groove 21 with a long clip and gently send it into the middle of the reaction tube 19 . The groove 21 at the edge is filled with quartz wool, which can increase the friction between the quartz wool plate 22 and the smooth inner wall of the quartz tube, prevent the quartz wool plate 22 from slipping off after loading the catalyst, and facilitate removal and replacement. The selected material has low resistance to gas filtration and high temperature resistance; the cleaning effect is obvious, economical and reliable, easy to replace, save time, and high safety.

The reaction tube 19 is set as an elongated quartz tube, which can reduce the temperature of the end extending out of the furnace body. Under the conditions allowed by the material of the reaction tube, a cooling device (such as a water cooling device) can be added to the end according to the needs, which can effectively reduce the temperature of the reaction tube quickly and facilitate the replacement of the catalyst; Auxiliary cooling measures.

Flange seals 20 are installed at both ends of the quartz reaction tube 19, such as stainless steel flanges and O-rings (high temperature resistant materials such as fluorine rubber) to avoid the poor sealing performance of traditional grinding plugs and poor sealing performance during vacuum operation Cause the reaction tube to burst or leak.

The reaction system is set as a reaction tube structure with two quartz tubes as a group. The difference between the two quartz tubes is that the catalyst is loaded on the quartz wool plate of one quartz tube, and the catalyst is not loaded on the quartz wool plate of the other quartz tube. , the rest of the structure is the same. In each test, the mixed gas entering the tube furnace was divided into two paths, respectively passing through the quartz tube without catalyst and the quartz tube loaded with catalyst. In the final data processing, the data of the quartz tube without catalyst should be considered to avoid the mixed gas from entering the high temperature atmosphere of the tube furnace. The temperature difference between the front and rear causes the gas composition to change, resulting in measurement errors and ensuring the participation of CO in the vacuum state. The catalytic oxidation reaction is carried out normally, and the authenticity and accuracy of the data collection. Economical and reliable, easy to replace, save time and high safety.

Example 1

As shown in FIG. 1 , the present invention includes a gas distribution system, a gas premixing device 7 , a vacuum pumping system 10 , a quartz tube furnace, a temperature control device 14 , a cooling system 15 , and a CO/CO ₂ analyzer 16 .

Among them, the gas distribution system is composed of _N2 gas cylinder 1, CO gas cylinder 2, _O2 gas cylinder 3, _CO2 gas cylinder 4, gas valve 5 corresponding to each gas cylinder, and gas distribution flowmeter 6; The mixing device 7 reaches the furnace body 11 of the evacuated tube furnace through the inlet valve 8 and the inlet flowmeter 9 of the tube furnace.

The tube furnace 11 has two parallel reaction tubes 19 built in, and a support layer 12 is provided in the middle respectively, and a quartz wool plate 22 with grooves 21 is used as the support layer 12 of the catalyst. After the temperature control device 14 reaches the target temperature, the gas undergoes redox reaction when passing through the catalyst, and then leaves the quartz tube furnace 11. The CO/CO ₂ analyzer 16 is used to analyze the main components, which is convenient for evaluating the effect of the catalyst. The waste gas is treated by the chemical absorption bottle 14 containing the absorption liquid.

The tube furnace reaction tube is made of materials that are resistant to high temperature and easy to obtain, such as quartz tube, corundum tube, etc., which can be purchased directly and are easy to replace. The catalyst is supported by a high temperature resistant quartz wool plate 22, as shown in Figure 3 and Figure 4, the setting position can be in the middle of the furnace tube, for example, the diameter of the furnace tube is 50mm, the length is 1000mm, the length of the heating section is 440mm, the length of the constant temperature section is 200mm, and the supporting layer 12 can be set in the middle of the furnace tube.

Example 2

In the present invention, as shown in FIG. 2 , the gas components mainly related to the CO redox reaction in the flue gas are selected, such as N ₂ , CO, O ₂ , CO ₂ , through the valve 5 and the gas distribution flowmeter, in the gas premixing device 7 . The mixed gas with different components is formed in the gas and enters into the micro-pressure tube furnace 11 . The mixed gas enters the reaction tube 19 simultaneously in two ways. One reaction tube 19 is filled with catalyst on the support layer 12; the other reaction tube is not filled with catalyst on the support layer 12. The redox reaction of CO occurs on the support layer 12 of the catalyst loaded in the quartz reaction tube. The appropriate reaction temperature is set by the temperature control device 14 in advance. After the reaction is completed, the mixed gas leaves the tube furnace, does not pass through the CO/CO ₂ analyzer 16, but is sampled by the gas sampling pipe 18, and is sent in batches. Go to the sampling and analysis unit to analyze the main components, which can effectively use the tube furnace to conduct multiple tests with different parameters during the heating period. It is worth noting that when data processing, blank experimental data needs to be considered, which can avoid errors caused by the change in the composition of the mixed gas due to the temperature difference after the mixed gas enters the tube furnace, thereby ensuring the authenticity and reliability of the experimental data. . After sampling, the gas is directly absorbed by the gas absorption bottle 14 containing the chemical absorption liquid (such as cuprous chloride complex aqueous solution), or the gas is first ignited to remove the CO in it, and then the chemical absorption liquid (such as concentrated hydrogen) is used to absorb the CO. sodium oxide solution) to remove the CO ₂ therein.

The support layer 12 of the tube furnace reaction tube 19 can also be supported by a high temperature resistant ceramic sand core. Using the ceramic sand core with certain porosity and high temperature resistance characteristics, the ceramic sand core is wrapped with quartz wool and placed in the quartz tube. , can also be loaded with catalysts. The setting position can be in the middle of the furnace tube, for example, the diameter of the furnace tube is 50mm, the length is 1000mm, the length of the heating section is 440mm, and the length of the constant temperature section is 200mm. The support layer can be set in the middle of the furnace tube.

Claims (10)

1. a tube furnace test system for catalytic oxidation of CO in coal-fired flue gas, is characterized in that, comprises gas distribution system, evacuation system (10), temperature control device (14) and cooling system (15), and vertical A furnace body (11) with the same structure, a furnace insulation layer (13) arranged in the furnace body (11), and a reaction tube (19) arranged in the furnace; The furnace insulation layer (13) is arranged in multiple layers, and a cooling passage for circulation of a cooling medium is arranged between two adjacent layers; The temperature measuring end and the heating end of the temperature control device (14) are both arranged in the furnace; The cooling system (15) is used for circulating cooling of the cooling medium, the output end is connected to the input end of the cooling passage, and the input end is connected to the output end of the cooling passage; The reaction tube (19) is provided with a support layer (12), the input end is connected to the parallel gas distribution system and the vacuum system (10), and the output end is connected to the analysis and absorption system. 2. the tube furnace test system of a kind of catalytic oxidation of CO in the coal-fired flue gas according to claim 1, is characterized in that, two reaction tubes (19) that are arranged in parallel in the hearth form one group, one reaction tube The support layer (12) in (19) is loaded with catalyst, and the support layer (12) in the other reaction tube (19) is not loaded with catalyst; the two reaction tubes (19) are connected in parallel, and the input ends are connected to the parallel gas distribution system and the vacuum pumping system (10), the output ends are all connected to the analysis and absorption system. 3. A tube furnace test system for catalytically oxidizing CO in coal-fired flue gas according to claim 1, wherein the support layer (12) is arranged in a disk shape, and the edges are symmetrically provided with grooves (twenty one). 4. A tube furnace test system for catalytic oxidation of CO in coal-fired flue gas according to claim 1, characterized in that, both ends of the reaction tube (19) extend out of the furnace body (11) through flange sealing (20) A cooling device is provided at the end of the reaction tube (19) extending out of the furnace body (11). 5. A tube furnace test system for catalytically oxidizing CO in coal-fired flue gas according to claim 1, wherein the gas distribution system comprises a gas premixing device (7), which is respectively connected in parallel to the gas The test gas cylinder at the input end of the premixing device (7) is sequentially connected to the inlet valve (8) and the inlet flowmeter (9) of the tubular furnace at the output end of the gas premixing device (7); The test gas cylinders include N ₂ gas cylinders (1), CO gas cylinders (2), O ₂ gas cylinders (3) and CO ₂ gas cylinders (4), and the test gas cylinders pass through their corresponding gas valves ( 5) and the gas distribution flow meter (6) are connected to the input end of the gas premixing device (7). 6. A kind of tube furnace test system for catalytic oxidation of CO in coal-fired flue gas according to claim 1, is characterized in that, described analysis and absorption system comprises the CO\CO that is sequentially connected to the output end of reaction tube (19) ₂ Analyzer (16) and gas absorption bottle (17). 7. A tube furnace test system for catalytic oxidation of CO in coal-fired flue gas according to claim 1, wherein the analysis and absorption system comprises a gas absorption bottle ( 17), and a gas sampling tube (18) arranged between the output end of the reaction tube (19) and the gas absorption bottle (17). 8. a kind of tube furnace test system for catalytic oxidation of CO in coal-fired flue gas according to claim 1, is characterized in that, reaction tube (19) adopts quartz reaction tube or corundum reaction tube, and support layer (12) adopts It is made of ceramic sand core, quartz wool, quartz sand board or quartz wool board (22). 9. A tube furnace test method for catalytic oxidation of CO in coal-fired flue gas, characterized in that, based on the system described in any one of claims 1-8, comprising the steps, Step 1, through the vacuuming system (10), the reaction tube (19) and the oxygen in the system are discharged, and filled with protective gas; In step 2, the furnace chamber is heated and controlled by the temperature control device (14), and the target temperature is reached through the temperature control device (14), and the gas input by the gas distribution system undergoes a redox reaction when passing through the catalyst, and then leaves the tube furnace, using analytical absorption. The system performs principal component analysis and exhaust gas absorption treatment. 10. A tube furnace test method for catalytic oxidation of _CO in coal-fired flue gas according to claim ₉ , characterized in that, during each test, the N provided by the N gas cylinder is used as the protective gas for removing oxygen , the mixed gas is obtained by mixing the corresponding gases provided by the N ₂ gas cylinder (1), the CO gas cylinder (2), the O ₂ gas cylinder (3) and the CO ₂ gas cylinder (4); The mixed gas entering the tube furnace is divided into two paths, which respectively pass through the reaction tube without catalyst and the reaction tube loaded with catalyst; during data processing in the analysis, the data collected from the reaction tube without catalyst is used as a control.

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