Urea pyrolysis flue gas denitration system

Abstract

The utility model discloses a urea pyrolysis flue gas denitration system which comprises a urea pyrolysis furnace and a denitration device, a normal-temperature fan; the gas inlet end of a cold source gas channel of the low-temperature gas-gas heat exchanger is communicated with the air outlet end of the normal-temperature fan, and the gas inlet end of a heat source gas channel of the low-temperature gas-gas heat exchanger is communicated with a low-grade flue gas heat source; two ends of the three-way pipeline are respectively provided with a main pipeline and a bypass pipeline, and the bypass pipeline is provided with a flow regulating valve; the gas inlet end of a cold source gas channel of the high-temperature gas-gas heat exchanger is communicated with the gas outlet end of the main pipeline, and the gas inlet end of a heat source gas channel of the high-temperature gas-gas heat exchanger is communicated with a high-temperature flue gas heat source. The urea pyrolysis flue gas denitration ultra-low emission system has the beneficial effects that the urea pyrolysis flue gas denitration ultra-low emission system has stable flow and stable temperature under the deep peak regulation condition of the boiler, the influence of the system on the thermal efficiency of the boiler is extremely small, and the normal-temperature fan is adopted, so that a stable dilution gas source and a heat source can be provided for urea pyrolysis; the problems of abrasion and blockage of a fan, a valve and a heat exchanger, conventional urea pyrolysis crystallization and the like are solved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of boiler (or industrial kiln) flue gas denitration purification. More specifically, the utility model relates to a urea pyrolysis flue gas denitration system. BACKGROUND

[0002] At present, the boiler (or industrial kiln) flue gas denitration technology mainly adopts the selective catalytic reduction (SCR) process, and the reducing agent raw material participating in the reaction is mainly ammonia water, liquid ammonia or urea, etc. The ammonia water has a lower safety level, but the storage and transportation equipment has a larger volume, a large amount of additional heat energy is needed to make ammonia gas, which leads to a higher operation cost, and the ammonia water is rarely used as a reducing agent preparation raw material in the field of coal-fired power generation boilers; the liquid ammonia process is simple, and the investment and operation cost is lower, but the liquid ammonia is a dangerous chemical, has a higher safety level, has more local approval restrictions, has high storage and transportation requirements, and the existing liquid ammonia reducing agent projects are gradually replaced by urea; the urea itself has no safety level requirement, and the storage and transportation are convenient, but the urea decomposition needs higher heat energy.

[0003] The urea ammonia preparation process can be divided into urea hydrolysis and urea pyrolysis. The load following property of the urea hydrolysis ammonia preparation process is relatively poor, and it is difficult to realize automatic control when the load fluctuates greatly; the urea hydrolysis device is a pressure container, and the pipeline is prone to corrosion and crystallization during operation, and the maintenance amount is large. The load following property of the urea pyrolysis ammonia preparation process is good, and the system is relatively simple and stable in operation. The traditional urea pyrolysis ammonia preparation process usually adopts hot primary air combined with an electric heater or a gas furnace, and the high required power consumption or gas quantity leads to a high operation cost. For example, according to different coal qualities, the power consumption of the urea pyrolysis ammonia preparation system of a 1000MW grade boiler flue gas denitration device using hot primary air combined with an electric heater is 1000-3000kWh / h, and the power consumption is high and the operation cost is large. The patent with the authorized announcement number CN103191640B discloses an SCR denitration reducing agent urea pyrolysis heat source supply method and device, and the hot primary air is heated to the urea pyrolysis temperature by using boiler hot flue gas; under the background of deep peak regulation, the pressure and flow of the hot primary air usually cannot meet the requirements of the gas-gas heat exchanger, urea pyrolysis and ammonia gas injection, and a booster fan and a fan cooling water system need to be additionally installed, and after the booster fan is additionally installed, the hot primary air has a large dust content after passing through the rotary air preheater, which easily causes the booster fan to wear, the valve and the heat exchanger to be blocked.

[0004] Therefore, there is an urgent need for a urea pyrolysis flue gas denitration system that can solve the above problems. UTILITY MODEL CONTENTS

[0005] An object of the utility model is to solve at least the above problems and provide at least the advantages to be explained later.

[0006] The utility model discloses still have an object is to provide a kind of urea pyrolysis flue gas denitration system, it can avoid valve pipeline blockage and fan abrasion as far as possible, operation is simple, reduce investment operating cost, can adapt to the needs of boiler load variation, nitrogen oxide concentration variation and boiler depth peak shaving.

[0007] In order to realize these purposes and other advantages according to the utility model, a urea pyrolysis flue gas denitration system is provided, which is applied to a boiler or an industrial furnace, and includes a urea pyrolysis furnace, a denitration device, and further includes:

[0008] Normal-temperature fan;

[0009] Low-temperature gas-gas heat exchanger, the gas inlet end of the cold source gas passage thereof is communicated with the air outlet end of the normal-temperature fan, and the gas inlet end of the heat source gas passage thereof is communicated with a low-grade flue gas heat source;

[0010] Three-way pipeline, one end of which is communicated with the gas outlet end of the cold source gas passage of the low-temperature gas-gas heat exchanger, and the other two ends of which are respectively a main pipeline and a bypass pipeline, and a flow regulating valve is arranged on the bypass pipeline;

[0011] High-temperature gas-gas heat exchanger, the gas inlet end of the cold source gas passage thereof is communicated with the gas outlet end of the main pipeline, and the gas inlet end of the heat source gas passage thereof is communicated with a high-temperature flue gas heat source;

[0012] Preferably, the gas inlet end of the urea pyrolysis furnace is communicated with the gas outlet end of the bypass pipeline and the gas outlet end of the cold source gas passage of the high-temperature gas-gas heat exchanger, respectively, and the gas outlet end of the urea pyrolysis furnace is communicated with the gas inlet end of the denitration device; the low-grade flue gas heat source is the flue gas at the inlet of the denitration device or the flue gas at the outlet of the denitration device; and the high-temperature flue gas heat source is the flue gas in the turning chamber of the boiler or the 500-1000℃ high-temperature flue gas discharged due to combustion of the industrial furnace.

[0013] Preferably, the urea pyrolysis flue gas denitration system further includes a pyrolysis pipeline and an ammonia pipeline, the gas inlet end of the pyrolysis pipeline is communicated with the gas outlet end of the bypass pipeline and the gas outlet end of the cold source gas passage of the high-temperature gas-gas heat exchanger, respectively, the gas outlet end of the pyrolysis pipeline is communicated with the gas inlet end of the urea pyrolysis furnace, the gas outlet end of the urea pyrolysis furnace is communicated with the gas inlet end of the ammonia pipeline, and the gas outlet end of the ammonia pipeline is communicated with the gas inlet end of the denitration device; and a thermocouple is arranged on the pyrolysis pipeline and the ammonia pipeline.

[0014] Preferably, the denitration device includes an inlet flue, a denitration reactor communicated with the inlet flue, an ammonia injection grid, and a static mixer, the gas inlet end of the inlet flue is communicated with flue gas to be denitrated, the ammonia injection grid and the static mixer are arranged in the inlet flue, and the static mixer is arranged between the ammonia injection grid and the denitration reactor; and the gas inlet end of the ammonia injection grid is communicated with the gas outlet end of the ammonia pipeline.

[0015] Preferably, the static mixer is a one-stage or multi-stage static mixer.

[0016] Preferably, the air outlet pipeline is further provided, the outlet end of the normal-temperature fan is communicated with the air inlet end of the air outlet pipeline, the air outlet end of the air outlet pipeline is communicated with the air inlet end of the cold source gas passage of the low-temperature gas-gas heat exchanger, the air outlet pipeline is provided with a flow meter and a fan main circuit regulating valve, and the fan main circuit regulating valve is located on the side of the flow meter close to the normal-temperature fan.

[0017] Preferably, the high-temperature flue gas heat source is 500-1000 DEG C high-temperature flue gas discharged due to combustion of an industrial kiln, and the system further comprises a leading-out device, one end of the leading-out device is communicated with the high-temperature flue gas heat source, and the other end is communicated with the air inlet end of the heat source gas passage of the high-temperature gas-gas heat exchanger.

[0018] The utility model at least includes following beneficial effects:

[0019] By setting normal-temperature fan, low-temperature gas-gas heat exchanger, three-way pipeline, flow regulating valve, high-temperature gas-gas heat exchanger, urea pyrolysis furnace and denitration device, a urea pyrolysis flue gas denitration ultra-low emission system with stable flow and stable temperature under the condition of boiler deep peak shaving is provided, the system has little influence on boiler thermal efficiency, adopts normal-temperature fan, can provide stable dilution gas source and heat source for urea pyrolysis, and solves problems such as fan, valve and heat exchanger wear and blockage, conventional urea pyrolysis crystallization and the like.

[0020] Other advantages, objects and features of the utility model will be embodied partly through the following description, and will be understood by those skilled in the art partly through the research and practice of the utility model. DRAWINGS

[0021] Figure 1 It is the structure schematic diagram of urea pyrolysis flue gas denitration system of one of technical schemes of the utility model.

[0022] Drawing reference: 1-normal-temperature fan;2-flow meter;3-low-temperature gas-gas heat exchanger;5-high-temperature gas-gas heat exchanger;7-bypass regulating valve;8-urea pyrolysis furnace inlet thermocouple;9-urea pyrolysis furnace;10-ammonia injection grid;11-static mixer;12-gas inlet flue;13-denitration reactor;14-air preheater;15-boiler turning chamber;16-low-temperature reheater;17-urea pyrolysis furnace outlet thermocouple;22-fan main circuit regulating valve;25-main pipeline;26-bypass pipeline;27-pyrolysis pipeline;28-ammonia gas pipeline;30-air outlet pipeline. SPECIFIC IMPLEMENTATION

[0023] The utility model discloses make further detailed description in combination with the drawings below, to enable the person skilled in the art to implement with reference to the description text.

[0024] It should be understood that the terms such as "have", "contain" and "include" used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0025] As Figure 1 Indicated, the utility model provides a kind of urea pyrolysis flue gas denitration system, it is applied to boiler or industrial kiln, including urea pyrolysis furnace 9, denitration device, further include:

[0026] Normal temperature fan 1;

[0027] Low-temperature gas-gas heat exchanger 3, the gas inlet end of its cold source gas passage is communicated with the air outlet end of normal temperature fan 1, and the gas inlet end of its heat source gas passage is communicated with low-grade flue gas heat source;

[0028] Three-way pipe, one end of which is communicated with the gas outlet end of the cold source gas passage of low-temperature gas-gas heat exchanger 3, and the other two ends of the pipe body are main pipe 25 and bypass pipe 26 respectively, and a flow regulating valve is arranged on the bypass pipe 26;

[0029] High-temperature gas-gas heat exchanger 5, the gas inlet end of its cold source gas passage is communicated with the gas outlet end of the main pipe 25, and the gas inlet end of its heat source gas passage is communicated with high-temperature flue gas heat source;

[0030] Among them, the gas inlet end of the urea pyrolysis furnace 9 is communicated with the gas outlet end of the bypass pipe 26 and the gas outlet end of the cold source gas passage of the high-temperature gas-gas heat exchanger 5 respectively, and the gas outlet end of the urea pyrolysis furnace 9 is communicated with the gas inlet end of the denitration device;The low-grade flue gas heat source is denitration device inlet flue gas or denitration device outlet flue gas;The high-temperature flue gas heat source is boiler turning chamber 15 flue gas or 500~1000℃ high-temperature flue gas discharged by industrial kiln due to combustion;

[0031] In the above technical solution, the model of normal temperature fan 1 is selected according to the system air volume demand, the pressure head can be set to 8~15kPa, the normal temperature fan 1 is installed in the well-ventilated machine room, the air outlet end thereof is closely connected with the gas inlet end of the cold source gas passage of low-temperature gas-gas heat exchanger 3, and the air inlet end of the normal temperature fan 1 is communicated with the ambient air to introduce ambient air;

[0032] The gas inlet end of the heat source gas passage of low-temperature gas-gas heat exchanger 3 is communicated with low-grade flue gas heat source, and the low-grade flue gas heat source is low-grade flue gas in boiler or industrial kiln, specifically, the low-grade flue gas has multiple sources, for example Figure 1In the existing denitration system of the boiler or industrial furnace, the flue gas outlet end of the denitration device is communicated with an air preheater 14, and the low-grade flue gas can be the flue gas between the denitration device and the air preheater 14, that is, the flue gas at the outlet end of the denitration device, or the flue gas at the inlet of the denitration device Figure 1 The low-grade flue gas heat source is communicated with the inlet end of the heat source gas passage of the low-temperature gas heat exchanger 3 in various ways, for example, it can be as follows Figure 1 The low-temperature gas heat exchanger 3 is arranged in the flue gas area behind the outlet end of the denitration device to receive the low-grade flue gas of the denitration device, or the low-temperature gas heat exchanger 3 is arranged in the flue gas area at the inlet of the denitration device

[0033] The three-way pipe is installed at the outlet end of the cold source gas passage of the low-temperature gas heat exchanger 3, specifically: the three-way pipe has three pipes, one pipe is communicated with the outlet end of the cold source gas passage of the low-temperature gas heat exchanger 3 to ensure firm connection without leakage, and the other two pipes are a main pipe 25 and a bypass pipe 26, respectively, and the bypass pipe 26 is provided with a flow regulating valve, which is a bypass regulating valve 7, and the bypass regulating valve 7 is preferably an electric regulating valve, which can be connected to an automatic control system for intelligent control

[0034] The outlet port of the main pipe 25 is communicated with the inlet end of the cold source gas passage of the high-temperature gas heat exchanger 5, and the inlet end of the heat source gas passage of the high-temperature gas heat exchanger 5 is communicated with a high-temperature flue gas heat source in the boiler or industrial furnace, specifically: the high-temperature flue gas heat source has various sources, for example, it can be the high-temperature flue gas in the boiler diversion chamber 15 upstream of the boiler low-temperature reheater 16, or the 500-1000℃ high-temperature flue gas discharged due to combustion in the industrial furnace, and in actual use, the high-temperature gas heat exchanger 5 is preferably arranged in or near the boiler diversion chamber 15, and when the high-temperature gas heat exchanger 5 is arranged near the boiler diversion chamber 15, an induced pipe can be designed, one end of the induced pipe is sealed and communicated with the inside of the boiler diversion chamber 15, and the other end is sealed and communicated with the heat source gas inlet end of the high-temperature gas heat exchanger 5, so as to induce the high-temperature flue gas in the boiler diversion chamber to the heat source gas passage of the high-temperature gas heat exchanger 5

[0035] The gas outlet ports of the bypass pipeline 26 and the cold source gas passage of the high-temperature gas-gas heat exchanger 5 are in communication with the gas inlet end of the urea pyrolysis furnace 9. Specifically, the urea pyrolysis furnace 9 is installed near the denitration device, and the gas inlet ends of the urea pyrolysis furnace 9 and the cold source gas passage of the high-temperature gas-gas heat exchanger 5 are in sealed communication. The two ports can be connected by a connecting pipeline. In actual use, the connecting pipeline is provided with necessary support and fixing devices. The gas outlet end of the urea pyrolysis furnace 9 is connected to the gas inlet end of the denitration device through a pipeline, and the pipeline is sealed well to prevent ammonia gas leakage. The denitration device is installed near the flue gas to be denitrated in the boiler or industrial furnace, such as being installed at a suitable position of the tail flue of the boiler, and is arranged in cooperation with the entire flue gas treatment system.

[0036] The gas outlet port of the low-temperature gas-gas heat exchanger 3 is connected to the gas inlet end of the urea pyrolysis furnace 9. Specifically, the urea pyrolysis furnace 9 is installed near the denitration device, and the gas inlet ends of the urea pyrolysis furnace 9 and the cold source gas passage of the high-temperature gas-gas heat exchanger 5 are in sealed communication. The two ports can be connected by a connecting pipeline. In actual use, the connecting pipeline is provided with necessary support and fixing devices. The gas outlet end of the urea pyrolysis furnace 9 is connected to the gas inlet end of the denitration device through a pipeline, and the pipeline is sealed well to prevent ammonia gas leakage. The denitration device is installed near the flue gas to be denitrated in the boiler or industrial furnace, such as being installed at a suitable position of the tail flue of the boiler, and is arranged in cooperation with the entire flue gas treatment system.

[0037] In the above technical solution, the use process is as follows: before the system starts, all equipment is comprehensively checked to ensure that the equipment is correctly installed, firmly connected, and the valves and instruments are in normal working condition. The running condition of the normal-temperature fan 1 is checked to observe whether the fan is normally reversed, vibrates and makes noise. When all parts are in normal operation, the air inlet end of the normal-temperature fan 1 introduces the ambient air into the normal-temperature fan 1, and outputs the ambient air from the air outlet end of the normal-temperature fan 1 to the gas inlet end of the cold source gas passage of the low-temperature gas-gas heat exchanger 3. At the same time, the low-grade flue gas heat source is introduced into the heat source gas passage of the low-temperature gas-gas heat exchanger 3. The ambient air and the low-grade flue gas are heat exchanged in the low-temperature gas-gas heat exchanger 3 to heat the ambient air to the required temperature to obtain intermediate air. The intermediate air is divided into two paths, one of which enters the cold source gas passage of the high-temperature gas-gas heat exchanger 5 through the main pipeline 25, and the other of which enters the bypass pipeline 26.

[0038] The high-temperature flue gas heat source such as the boiler diversion chamber 15 is introduced into the heat source gas passage of the high-temperature gas-gas heat exchanger 5, and the intermediate air located in the cold source gas passage of the high-temperature gas-gas heat exchanger 5 exchanges heat with the high-temperature flue gas in the high-temperature gas-gas heat exchanger 5, so that the intermediate air is further heated to the required temperature to obtain high-temperature air; the high-temperature air is combined with the intermediate air entering the bypass pipeline 26 to form mixed air with high temperature, and the mixed air with high temperature enters the urea pyrolysis furnace 9 from the inlet of the urea pyrolysis furnace 9; the mixed air with high temperature pyrolyzes the urea solution in the urea pyrolysis furnace 9 into ammonia gas and dilutes the ammonia gas, and the diluted ammonia gas is transported to the denitration device through a pipeline for denitration; in the denitration device, the ammonia gas and the nitrogen oxides in the flue gas undergo an oxidation-reduction reaction to achieve the purpose of denitration; during the operation of the entire system, the operation parameters of each device, such as temperature, pressure, flow, nitrogen oxide concentration, etc., can be closely monitored in cooperation with an external control system, and the system operation parameters can be adjusted in time according to the monitoring data to ensure stable operation of the system;

[0039] In the above process, the bypass regulating valve 7 can be adjusted adaptively according to the load condition of the boiler and the denitration requirement, the proportion of the intermediate air in the main pipeline 25 and the bypass pipeline 26 is controlled, and then the temperature of the mixed air entering the urea pyrolysis furnace 9 is controlled to stabilize it in the required temperature range; for example, when the temperature of the mixed air is too low, the flow of the bypass pipeline 26 is appropriately reduced, so that more intermediate air enters the high-temperature gas-gas heat exchanger 5 to be further heated, and when the temperature of the mixed air is too high, the flow of the bypass pipeline 26 is appropriately increased, so that less intermediate air enters the high-temperature gas-gas heat exchanger 5;

[0040] The beneficial effects obtained by the technical scheme are that the urea pyrolysis flue gas denitration system is provided by arranging the normal-temperature fan 1, the low-temperature gas-gas heat exchanger 3, the three-way pipeline, the flow regulating valve, the high-temperature gas-gas heat exchanger 5, the urea pyrolysis furnace 9 and the denitration device, the ambient air is used as the pyrolysis air source of the urea pyrolysis furnace 9, the dust content of the ambient air is lower than that of the hot primary air in the prior art, so that the blockage of each pipeline in the system and the abrasion of the fan can be avoided as much as possible, the operation and maintenance are simple, the ambient air is preheated by using the low-grade heat source flue gas, on the one hand, the utilization rate of the low-grade heat source in the boiler or industrial furnace is improved, and on the other hand, the ambient air is further heated by the subsequent high-temperature flue gas, so that the operation cost of the system is saved, in addition, the main pipeline 25, the bypass pipeline 26 and the bypass regulating valve 7 are arranged, the temperature of the mixed air entering the urea pyrolysis furnace 9 can be adjusted, the temperature of the mixed air entering the urea pyrolysis furnace 9 is stabilized in the required range, the stability of the system operation is improved, finally, the ambient air is used as the medium and cooperates with the bypass regulating valve 7, the needs of the boiler load change, the nitrogen oxide concentration change and the boiler deep peak regulation are met, and the application prospect is good; in addition, the low-temperature gas-gas heat exchanger and the normal-temperature fan are arranged synchronously, the flue gas at the inlet of the denitration device or the flue gas at the outlet of the denitration device can be selected as the low-grade heat source flue gas according to the actual demand, the utilization rate of the low-grade heat source flue gas in the boiler or furnace is improved, the waste of the low-grade heat source flue gas is avoided, and the operation cost of the entire denitration system is reduced, in addition, compared with the hot primary air in the prior art, the normal-temperature fan and the low-temperature gas-gas heat exchanger are introduced in the present application, the flue gas at the outlet or the inlet of the denitration device can be selected as the low-grade heat source flue gas, the utilization rate and the selection range of the low-grade flue gas in the boiler or furnace are improved, and the practicability is stronger.

[0041] In another technical scheme, the pyrolysis pipeline 27 and the ammonia pipeline 28 are further included, the gas inlet ends of the pyrolysis pipeline 27 are in communication with the gas outlet ends of the bypass pipeline 26 and the cold source gas passage of the high-temperature gas-gas heat exchanger 5 respectively, the gas outlet end of the pyrolysis pipeline 27 is in communication with the gas inlet end of the urea pyrolysis furnace 9, the gas outlet end of the urea pyrolysis furnace 9 is in communication with the gas inlet end of the ammonia pipeline 28, and the gas outlet end of the ammonia pipeline 28 is in communication with the gas inlet end of the denitration device; wherein the pyrolysis pipeline 27 and the ammonia pipeline 28 are both provided with thermocouples.

[0042] In the above technical scheme, the air inlet end of the pyrolysis pipeline 27 is reliably connected with the air outlet end of the bypass pipeline 26 and the air outlet end of the cold source gas channel of the high-temperature gas gas heat exchanger 5, specifically, the air outlet end of the heat source gas channel of the high-temperature gas gas heat exchanger 5 is sealingly communicated with a connecting pipeline, one end of the connecting pipeline away from the high-temperature gas gas heat exchanger 5 and the air outlet end of the bypass pipeline 26 are both communicated with the air inlet end of the pyrolysis pipeline 27, that is, the connecting pipeline, the bypass pipeline 26 and the pyrolysis pipeline 27 form a three-way pipeline; during the connection of each pipeline, sealing gaskets and bolts are used to prevent air leakage, and at the same time, the layout of the pipelines should be reasonable to reduce bends and resistance and ensure that air can flow smoothly into the pyrolysis pipeline 27; the air outlet end of the pyrolysis pipeline 27 is sealingly communicated with the air inlet end of the urea pyrolysis furnace 9, and after installation, pressure test can be performed to ensure that there is no leakage at the connection part.

[0043] The air outlet end of the urea pyrolysis furnace 9 is sealingly communicated with the air inlet end of the ammonia gas pipeline 28, and the sealing and firmness of the connection should also be ensured during the connection process; the air outlet end of the ammonia gas pipeline 28 is connected with the air inlet end of the denitration device, and during actual installation, the problem of thermal expansion of the pipeline should be considered, and an appropriate expansion joint should be arranged; the ammonia gas pipeline 28 should be installed at a position convenient for maintenance and inspection, and good heat preservation measures should be taken to reduce heat loss.

[0044] Among them, thermocouples are installed at appropriate positions on the pyrolysis pipeline 27 and the ammonia gas pipeline 28, the thermocouple on the pyrolysis pipeline 27 is the urea pyrolysis furnace inlet thermocouple 8, which is used to detect the temperature of mixed air at the inlet of the urea pyrolysis furnace 9, and the thermocouple on the ammonia gas pipeline 28 is the urea pyrolysis furnace outlet thermocouple 17, which is used to detect the temperature of diluted ammonia gas at the outlet of the urea pyrolysis furnace 9; the installation of the thermocouples should ensure accurate measurement, the probes thereof should be inserted into the pipeline interior to an appropriate depth to avoid interference from external factors, and after installation, the thermocouples should be calibrated to ensure the accuracy of the measurement data.

[0045] In the technical solution, the use process is as follows: before the system starts, all the equipment is comprehensively checked to ensure that the equipment is in normal operation; the normal temperature fan 1, the low-temperature gas-gas heat exchanger 3 and the high-temperature gas-gas heat exchanger 5 are started, and the corresponding heat source and cold source are introduced; in actual use, the operating parameters of each device can be adjusted through the automatic control system to make the air flow according to the designed process; during the operation of the system, the temperature data of the thermocouples on the pyrolysis pipeline 27 and the ammonia pipeline 28 are monitored in real time, and the mixed air temperature at the inlet of the urea pyrolysis furnace 9 detected by the inlet thermocouple 8 of the urea pyrolysis furnace is compared with the set target temperature range (for example, 450~650℃); if the temperature of the mixed air at the inlet is lower than the target range, the opening degree of the bypass regulating valve 7 on the bypass pipeline 26 is appropriately reduced, so that more intermediate air passes through the high-temperature gas-gas heat exchanger 5 for heating, thereby increasing the air temperature entering the urea pyrolysis furnace 9; on the contrary, if the temperature of the mixed air at the inlet is higher than the target range, the opening degree of the bypass regulating valve 7 is increased, so that more intermediate air enters the bypass pipeline 26 and mixes with the high-temperature air in the pyrolysis pipeline 27 to reduce the temperature of the mixed air at the inlet; at the same time, the temperature of the diluted ammonia gas at the outlet of the urea pyrolysis furnace 9 detected by the outlet thermocouple 17 on the ammonia pipeline 28 is monitored, and according to the change of the temperature of the diluted ammonia gas at the outlet, the opening degree of the bypass regulating valve 7 is further adjusted to ensure that the temperature of the diluted ammonia gas at the outlet is also stabilized in the required range (for example, 360~420℃), so as to ensure the effect of urea pyrolysis and the smooth progress of denitration reaction; in addition, the system can also be tested for stability under different boiler load conditions (such as high load and low load) to observe whether the temperature data detected by the pair of thermocouples can quickly respond to the change of the working condition, and the temperature is stabilized in the target range by adjusting the bypass regulating valve 7.

[0046] By adopting the technical solution, the beneficial effects are obtained: by arranging the pyrolysis pipeline 27, the ammonia pipeline 28 and the pair of thermocouples, the temperature of the mixed air at the inlet of the urea pyrolysis furnace 9 and the temperature of the diluted ammonia gas at the outlet can be detected by the pair of thermocouples, and then the bypass regulating valve 7 is adjusted adaptively according to the required temperature, so as to stabilize the temperature of the mixed air at the inlet of the urea pyrolysis furnace 9 and the temperature of the diluted ammonia gas at the outlet in the required range as much as possible, thereby improving the operation stability of the denitration system.

[0047] In another technical solution, the denitration device comprises an inlet flue 12, a denitration reactor 13 communicated with the inlet flue 12, an ammonia injection grid 10, and a static mixer 11. The inlet end of the inlet flue 12 is communicated with the flue gas to be denitrated. The ammonia injection grid 10 and the static mixer 11 are both arranged in the inlet flue 12. The static mixer 11 is arranged between the ammonia injection grid 10 and the denitration reactor 13. The inlet end of the ammonia injection grid 10 is communicated with the outlet end of the ammonia gas pipeline 28, so that the ammonia gas after pyrolysis in the ammonia gas pipeline 28 is sprayed into the inlet flue 12 and mixed with the flue gas to be denitrated in the static mixer 11.

[0048] In the above technical solution, the denitration device is installed near the port of the flue gas to be denitrated in the boiler or industrial furnace, so that the inlet end of the inlet flue 12 can be smoothly communicated with the flue gas to be denitrated. The installation position of the entire device is convenient for subsequent maintenance and repair, and the space coordination with other equipment is considered.

[0049] The inlet flue 12 is installed to ensure the sealing of the connection between the inlet flue 12 and the denitration reactor 13. The connection part can be treated by welding and sealing glue to prevent leakage of the flue gas to be denitrated. The support structure of the inlet flue 12 is firm and can bear the pressure of the flue gas and its own weight. The installation interface of the ammonia injection grid 10 and the static mixer 11 is reserved on the inlet flue 12. The position and size of the interface strictly meet the design requirements. The inlet flue 12 is the flue in the existing boiler system or industrial furnace system that connects the flue gas to be denitrated and the denitration reactor 13.

[0050] The ammonia injection grid 10 is installed at a suitable position in the inlet flue 12. The inlet end of the ammonia injection grid 10 is communicated with the outlet end of the ammonia gas pipeline 28, so that the diluted ammonia gas from the urea pyrolysis furnace 9 is sprayed into the inlet flue 12 through the ammonia injection grid 10. In actual use, the outlet end of the ammonia gas pipeline 28 can be sealed and extended into the inlet flue 12 and communicated with the inlet end of the ammonia injection grid 10, so that the ammonia gas after pyrolysis can smoothly enter the ammonia injection grid 10. After installation, it is checked whether the nozzle of the ammonia injection grid 10 is unobstructed. If there is blockage, it is cleaned in time. The static mixer 11 is installed in the inlet flue 12 between the ammonia injection grid 10 and the denitration reactor 13. The static mixer 11 is used to mix the ammonia gas and the flue gas to be denitrated.

[0051] The denitration reactor 13 is installed at the end of the inlet flue 12. The inlet end of the denitration reactor 13 is sealed and communicated with the outlet end of the inlet flue 12. The foundation of the denitration reactor 13 is firm and can bear the weight of the reactor and the internal catalyst. In actual connection, the inlet and outlet of the denitration reactor 13 are connected with the inlet flue 12 and the subsequent flue gas discharge pipeline, so that the connection part is sealed well.

[0052] Wherein, the above structure and connection are one or more implementation manners, and other implementation manners exist in the prior art, and the structures and installation of the inlet flue 12, the ammonia injection grid 10, the static mixer 11 and the denitration reactor 13 are the prior art in the field, and more specific details can be referred to the prior art;

[0053] In the above technical solution, the use process is as follows: before system debugging, all equipment is comprehensively checked, and after confirmation of no error, when the boiler load is lifted to above the minimum stable combustion load (generally 25-30% of the boiler BMCR load), the normal temperature fan 1, the low-temperature gas-gas heat exchanger 3, the high-temperature gas-gas heat exchanger 5, the urea pyrolysis furnace 9, the ammonia injection grid 10, the static mixer 11, the denitration reactor 13 and other equipment are started in turn, so that the ammonia gas after pyrolysis is transported to the ammonia injection grid 10 through the ammonia gas pipeline 28, at the same time, the denitration flue gas is introduced into the inlet flue 12, so that the ammonia gas and the denitration flue gas are preliminarily mixed, then the denitration flue gas in the inlet flue 12 is sprayed together with the ammonia gas to the static mixer 11 through the ammonia injection grid 10, and is fully mixed under the action of the static mixer 11, and then the mixed ammonia gas and denitration flue gas enter the denitration reactor 13 for final denitration;

[0054] By adopting the technical solution, the beneficial effects are that by arranging the inlet flue 12, the denitration reactor 13, the ammonia injection grid 10 and the static mixer 11, compared with the existing urea direct injection process in the furnace, the corrosion of the boiler heating surface is avoided, and the problems of high energy consumption of the existing urea pyrolysis system, reduced utilization rate of the boiler heating surface and easy crystallization and blockage are solved.

[0055] In another technical solution, the static mixer 11 is a one-stage or multi-stage static mixer 11; specifically, the inlet flue 12 adopts the arrangement mode of the existing boiler and kiln denitration system, and a one-stage or multi-stage static mixer 11 is arranged at the vertical upward flue of the existing inlet flue 12, so that the ammonia gas and the flue gas can be fully mixed under the action of the static mixer 11, and then enter the denitration reactor 13 to occur redox reaction, which can meet the higher denitration efficiency (more than 90%) of the denitration device and realize ultra-low emission of nitrogen oxides in the boiler flue gas.

[0056] In another technical solution, the outlet flue 30 is further included, the outlet end of the normal temperature fan 1 is communicated with the inlet end of the outlet flue 30, the outlet end of the outlet flue 30 is communicated with the inlet end of the cold source gas passage of the low-temperature gas-gas heat exchanger 3, the flow meter 2 and the fan main road regulating valve 22 are arranged on the outlet flue 30, and the fan main road regulating valve 22 is located on the side of the flow meter 2 close to the normal temperature fan 1;

[0057] In the above technical solution, specifically, the air outlet pipeline 30 can be made of high-quality carbon steel, and its diameter is determined according to the design air volume of the normal-temperature fan 1 and system requirements; the air inlet end of the air outlet pipeline 30 is in sealed communication with the outlet end of the normal-temperature fan 1, and a sealing gasket can be used to prevent air leakage; the air outlet end of the air outlet pipeline 30 and the air inlet end of the cold source air passage of the low-temperature air-to-air heat exchanger 3 are also flange-connected, and the verticality and levelness of the pipeline should be ensured during installation to reduce air flow resistance; during actual installation of the air outlet pipeline 30, pipeline supports can be arranged at intervals on the air outlet pipeline 30, and the supports should be firm and reliable to bear the weight of the pipeline and the internal air; the bends and branches should be well supported to prevent pipeline deformation.

[0058] The flow meter 2 is installed at a suitable position on the air outlet pipeline 30, and the installation position should be selected at a straight pipe section away from bends, valves and other components that interfere with air flow, to ensure the accuracy of measurement; generally, the length of the upstream straight pipe section of the flow meter 2 should be no less than ten times the pipe diameter, and the length of the downstream straight pipe section should be no less than five times the pipe diameter; during installation of the flow meter 2, the flow meter 2 can be flange-connected to the air outlet pipeline 30, and attention should be paid to the direction of the flow meter 2 during installation to ensure that the air flow direction is consistent with the direction indicated on the flow meter 2; after installation is completed, the flow meter 2 should be sealed to prevent air leakage from affecting measurement accuracy.

[0059] The fan main route regulating valve 22 is located on the side of the flow meter 2 close to the normal-temperature fan 1, and the fan main route regulating valve 22 can also be flange-connected to the air outlet pipeline 30; during installation, the installation height of the valve should be suitable for operation and maintenance; after installation is completed, the fan main route regulating valve 22 should be debugged to check its sealing performance and flexibility.

[0060] In this technical solution, the use process is as follows: before system debugging, all equipment is comprehensively checked, including whether the installation of the air outlet pipeline 30, the flow meter 2 and the fan main route regulating valve 22 is correct, whether the normal-temperature fan 1 and the low-temperature air-to-air heat exchanger 3 are normal, etc.; then the normal-temperature fan 1 is started, air enters the low-temperature air-to-air heat exchanger 3 through the air outlet pipeline 30, the display data of the flow meter 2 is observed, the air flow entering the low-temperature air-to-air heat exchanger 3 is recorded, and the opening of the fan main route regulating valve 22 is adaptively adjusted according to the change of the boiler load to optimize the air flow entering the low-temperature air-to-air heat exchanger 3.

[0061] By adopting the technical solution, the flow of normal-temperature air entering the low-temperature air-to-air heat exchanger can be monitored, and the required normal-temperature air flow can be adaptively adjusted according to the change of the boiler load, so that the system can better adapt to the change of the boiler load to meet the deep peak shaving demand of the boiler;

[0062] Specifically, in the above technical solution, more specifically, the details are as follows:

[0063] Further comprising a standby fan, which is communicated with the gas inlet end of the cold source gas passage of the low-temperature gas gas heat exchanger 3 through a pipeline, and a flow regulating valve is arranged on the pipeline, so that when the normal-temperature fan 1 fails, the normal-temperature fan 1 and the fan main road regulating valve 22 are closed, the standby fan and the flow regulating valve are started, and the ambient air is continuously supplied into the low-temperature gas gas heat exchanger 3, so that the system can continue to operate stably.

[0064] In another technical solution, the high-temperature flue gas heat source is 500-1000 DEG C high-temperature flue gas discharged due to combustion in an industrial kiln; further comprising a leading device, one end of the leading device is communicated with the high-temperature flue gas heat source, and the other end is communicated with the gas inlet end of the heat source gas passage of the high-temperature gas gas heat exchanger 5; specifically, the high-temperature flue gas heat source is selected from 500-1000 DEG C high-temperature flue gas discharged due to combustion in an industrial kiln, when the area where the high-temperature flue gas in the industrial kiln is located is not convenient to arrange the high-temperature gas gas heat exchanger 5, the high-temperature gas gas heat exchanger 5 is arranged, and then the leading device such as a leading pipeline is used, one end of the leading pipeline is communicated with the high-temperature flue gas, and the other end is communicated with the gas inlet end of the heat source gas passage of the high-temperature gas gas heat exchanger 5, so as to lead the high-temperature flue gas into the high-temperature gas gas heat exchanger, and such design can flexibly arrange the high-temperature gas gas heat exchanger 5, and improve the use range of the system.

[0065] The number of devices and the processing scale described herein are used to simplify the description of the present application. The application, modification and change of the urea pyrolysis flue gas denitration system of the present application are obvious to those skilled in the art.

[0066] Although the embodiments of the present application have been disclosed as above, it is not limited to the application and embodiments listed in the specification, and it can be fully applied to various fields suitable for the present application, and other modifications can be easily realized by those skilled in the art, therefore, the present application is not limited to specific details and the figures shown and described herein, without departing from the general concept defined by the claims and the equivalent scope.

Claims

1. A urea pyrolysis flue gas denitration system applied to a boiler or an industrial furnace, comprising a urea pyrolysis furnace and a denitration device, characterized in that, Also comprising: Normal temperature fan; Low-temperature gas-gas heat exchanger, the cold source gas passage of which is communicated with the air outlet end of the normal temperature fan, and the inlet end of the heat source gas passage is communicated with the low-grade flue gas heat source; Three-way pipeline, one end of which is communicated with the outlet end of the cold source gas passage of the low-temperature gas-gas heat exchanger, and the other two ends are respectively the main pipeline and the bypass pipeline, and a flow regulating valve is arranged on the bypass pipeline; High-temperature gas-gas heat exchanger, the inlet end of the cold source gas passage of which is communicated with the outlet end of the main pipeline, and the inlet end of the heat source gas passage is communicated with the high-temperature flue gas heat source; Wherein, the inlet end of the urea pyrolysis furnace is communicated with the outlet end of the bypass pipeline and the outlet end of the cold source gas passage of the high-temperature gas-gas heat exchanger, and the outlet end of the urea pyrolysis furnace is communicated with the inlet end of the denitration device; the low-grade flue gas heat source is the flue gas at the inlet of the denitration device or the flue gas at the outlet of the denitration device; the high-temperature flue gas heat source is the flue gas at the turning chamber of the boiler or the 500-1000℃ high-temperature flue gas discharged due to combustion of the industrial kiln.

2. The urea pyrolysis flue gas denitration system according to claim 1, characterized in that, Further comprising pyrolysis pipeline and ammonia pipeline, the inlet end of the pyrolysis pipeline is communicated with the outlet end of the bypass pipeline and the outlet end of the cold source gas passage of the high-temperature gas-gas heat exchanger, the outlet end of the pyrolysis pipeline is communicated with the inlet end of the urea pyrolysis furnace, the outlet end of the urea pyrolysis furnace is communicated with the inlet end of the ammonia pipeline, and the outlet end of the ammonia pipeline is communicated with the inlet end of the denitration device; wherein, a thermocouple is arranged on the pyrolysis pipeline and the ammonia pipeline.

3. The urea pyrolysis flue gas denitration system according to claim 2, characterized in that, The denitration device comprises an inlet flue, a denitration reactor communicated with the inlet flue, an ammonia injection grid, and a static mixer, the inlet end of the inlet flue is communicated with the flue gas to be denitrated, the ammonia injection grid and the static mixer are arranged in the inlet flue, and the static mixer is arranged between the ammonia injection grid and the denitration reactor; wherein, the inlet end of the ammonia injection grid is communicated with the outlet end of the ammonia pipeline.

4. The urea pyrolysis flue gas denitration system according to claim 3, characterized in that, The static mixer is a one-stage or multi-stage static mixer.

5. The urea pyrolysis flue gas denitration system according to claim 4, characterized in that, Further comprising an air outlet pipeline, the outlet end of the normal temperature fan is communicated with the air inlet end of the air outlet pipeline, the air outlet end of the air outlet pipeline is communicated with the inlet end of the cold source gas passage of the low-temperature gas-gas heat exchanger, a flow meter and a fan main road regulating valve are arranged on the air outlet pipeline, and the fan main road regulating valve is located on the side of the flow meter close to the normal temperature fan.

6. The urea pyrolysis flue gas denitration system according to claim 1, characterized in that, The high-temperature flue gas heat source is the 500-1000℃ high-temperature flue gas discharged due to combustion of the industrial kiln; further comprising a leading device, one end of the leading device is communicated with the high-temperature flue gas heat source, and the other end is communicated with the inlet end of the heat source gas passage of the high-temperature gas-gas heat exchanger.

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