Regulating system for inlet temperature of flue gas denitration device of biomass boiler

Abstract

The utility model discloses a biomass boiler flue gas denitration device inlet temperature adjusting system which comprises a second flue, a third flue and a fourth flue which are sequentially connected with an outlet of a hearth and are vertically arranged, an inlet of the second flue is connected with the outlet of the hearth, the second flue is communicated with the lower end of the third flue, and the fourth flue is communicated with the outlet of the hearth. The upper end of the third flue is connected with the upper end of the fourth flue through a furnace top turning flue, a temperature adjusting heat exchanger capable of reducing the temperature of flue gas, an evaporator and / or a superheater are sequentially arranged in the third flue, and a denitration device and a tail heating surface are arranged in the fourth flue. A dust remover is arranged in the furnace top turning flue, and a bypass flue capable of increasing the smoke temperature is arranged between the top of the hearth and the dust remover front flue. The boiler DCS system controls the opening degree of the regulating valve or the opening degree of the flue gas baffle according to the temperature, measured by the thermocouple, of the flue gas entering the denitration device, so that the temperature of the flue gas entering the denitration device can be regulated and controlled, and the denitration device is always in the optimal denitration temperature interval.

Description

TECHNICAL FIELD

[0001] The utility model relates to a boiler technical field especially relates to a furnace -grate type biomass boiler of burning biomass. BACKGROUND

[0002] Biomass boiler as the important equipment of biomass energy utilization is the boiler that biomass is directly used as fuel combustion, is widely used in heating, industrial production and power generation etc. The fuel type that biomass boiler adopts is many, the component is complex. Compared with traditional coal-fired boiler, the nitrogen element content in biomass fuel is higher, so the nitrogen oxide (abbreviation NOx) pollutant produced by its combustion is more than coal-fired boiler, and nitrogen oxide is the key atmospheric pollutant, it directly or indirectly causes harm to the environment, building, plant, human, therefore, before discharging, the flue gas needs to carry out denitration treatment, makes the NOx in gas reduce, guarantees the safety of discharge gas, the technical means that can handle NOx at present mainly includes the ammonia injection denitration (SNCR) in furnace and catalytic reduction denitration (SCR), the efficiency of SNCR denitration process is lower relatively, and needs to be arranged in high temperature flue gas area, because of the particularity of biomass boiler structure, the overall bed temperature of hearth is low, generally between 700 DEG C-800 DEG C, and the optimum temperature window of SNCR denitration process is 850 DEG C-1050 DEG C, so the SNCR temperature window is not suitable, leads to very low efficiency even no effect, and ammonia water consumption is far more than the theoretical value, is not economical. The SCR denitration process technology is mature and reliable, can reach the ultra-low emission requirement of state, but it is greatly influenced by the size of boiler load, fuel type change, leads to the instability of SCR denitration efficiency, because of catalyst activity etc. its working temperature is generally at 320 DEG C to 380 DEG C, and when under low load or burning low calorific value fuel, the smoke temperature of SCR inlet does not reach the smoke temperature required by catalyst, leads to the low reaction efficiency of catalytic reduction etc. Some designers set up steam heater at the inlet of SCR, heat the temperature of the smoke temperature of SCR inlet to the activation temperature of catalyst, to improve catalyst activity and improve the reaction efficiency of SCR denitration, then through heat exchanger, the heat is recovered, this needs to increase heat exchanger, the energy consumption of this process heating flue gas is big, therefore, such flue gas denitration system structure is complex, investment cost is high, and needs to consume steam in the operation process, the operation cost is high. But when under high load, the problem of the overhigh smoke temperature of SCR inlet exists, the flue gas temperature cannot meet, and the denitration system has to be out of operation, causes NOx emission to exceed the standard. SUMMARY

[0003] The utility model aims at overcoming the deficiency in the prior art, provides a kind of biomass boiler flue gas denitration device entrance temperature's adjusting system, to solve the problems in background art.

[0004] The utility model discloses a technical scheme adopted for realizing the above-mentioned purpose is:

[0005] A kind of biomass boiler flue gas denitration device entrance temperature's regulating system, including boiler DCS control system, hearth, the second flue, third flue, fourth flue sequentially connected in order with the outlet of hearth, second flue, third flue, fourth flue are vertically arranged, the import of second flue is connected with the outlet of hearth, second vertical flue is connected with the lower end portion of third vertical flue, the upper end of third flue and fourth flue is connected through furnace top elbow flue, evaporator and / or superheater are arranged in third flue, and denitration device and tail heating surface are sequentially arranged in fourth flue according to flue gas flow direction;Dust remover is arranged in furnace top elbow flue, dust remover divides furnace top elbow flue into dust remover front flue and denitration device front flue, characterized by: the upper portion of evaporator and superheater in third flue is provided with temperature regulating heat exchanger capable of reducing flue gas temperature, and the top of hearth is provided with bypass flue capable of improving flue gas temperature between dust remover front flue.

[0006] In the above-mentioned biomass boiler flue gas denitration device entrance temperature's regulating system, the bypass flue is provided with flue gas baffle, the flue gas baffle is connected with electric actuator, the electric actuator is connected with boiler DCS control system;The temperature regulating heat exchanger is provided with water channel and flue gas channel, and the flue gas in third flue can pass through flue gas channel;The heat source working medium of temperature regulating heat exchanger is flue gas, and the heated working medium is water, the import end of water channel is connected with water inlet pipe, and the export end of water channel is connected with water outlet pipe;The water inlet pipe is provided with water inlet pipe valve, and the water outlet pipe is provided with water outlet pipe valve, and the water inlet pipe valve and water outlet pipe valve are connected with boiler DCS control system.

[0007] Further, the water inlet pipe and the water outlet pipe are connected by a temperature regulating loop, and an adjusting valve is arranged in the temperature regulating loop.

[0008] By adopting the above technical scheme, the bypass flue is arranged between the top of hearth and dust remover front flue, and the flue gas entering third flue and bypass flue is first dusted by dust remover, and then the dust-free flue gas enters denitration device for reaction, so that the denitration device is not affected by alkali metal in fly ash, and the catalyst is not poisoned and disabled.The temperature regulating heat exchanger is arranged in the upper portion of evaporator and superheater in third flue, the flue gas temperature measured by thermocouple arranged in denitration device front flue is fed back to boiler DCS system, after being processed by boiler DCS system, the opening degree of adjusting valve or the opening degree of flue gas baffle is controlled by boiler DCS system, so that the flue gas temperature entering denitration device can be regulated and controlled, and the denitration device is always in the best denitration temperature range.By closing water inlet pipe valve and water outlet pipe valve, the temperature regulating heat exchanger can be withdrawn from temperature regulating operation, and by closing flue gas baffle, the bypass flue can be withdrawn from temperature regulating operation.

[0009] The tail heating surface is the heating surface of an economizer and an air preheater.

[0010] Further, a thermocouple is arranged in the front flue of the denitration device, and the thermocouple is connected with the boiler DCS control system.

[0011] By using the above technical scheme, the boiler DCS control system receives the flue gas temperature entering the denitration device measured by the thermocouple, and can control the opening degree of the flue gas baffle and the inlet water pipe valve / outlet water pipe valve / regulating valve, so as to regulate and control the flue gas temperature entering the denitration device. Beneficial effects

[0012] A bypass flue is arranged between the top of the furnace and the dust remover front flue, and the flue gas entering the third flue and the bypass flue is first dusted by the dust remover, and the dust-free flue gas enters the denitration device for reaction, so as to avoid that the denitration device is affected by alkali metals in the fly ash and causes the catalyst to be poisoned and invalid. The temperature regulating heat exchanger is arranged in the third flue and located at the upper part of the evaporator and the superheater, the thermocouple arranged in the front flue of the denitration device feeds back the measured flue gas temperature to the boiler DCS system, after being processed by the boiler DCS system, the boiler DCS system controls the opening degree of the regulating valve or the opening degree of the flue gas baffle, so as to regulate and control the flue gas temperature entering the denitration device, so that the denitration device is always in the best denitration temperature range, and the requirement of the SCR denitration reaction is met; the problem that the reaction efficiency of the catalytic reduction is low due to that the flue gas temperature at the SCR inlet cannot meet the requirement of the catalyst due to the unstable combustion condition of the boiler and the size of the boiler load caused by the change of the fuel and other factors is solved. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a schematic view of the present application.

[0014] In the figure: 1 furnace, 2 bypass flue, 3 flue gas baffle, 4 boiler DCS control system, 5 second flue, 6 superheater, 7 evaporator, 8 third flue, 9 temperature regulating heat exchanger, 10 dust remover front flue, 11 dust remover, 12 thermocouple, 13 denitration device front flue, 14 inlet water pipe, 14-1 inlet water pipe valve, 15 outlet water pipe, 15-1 outlet water pipe valve, 16 temperature regulating loop, 16-1 regulating valve, 17 denitration device, 18 fourth flue, 19 economizer two, 20 secondary air preheater, 21 primary air preheater, 22 economizer one, 23 flue gas outlet. DETAILED DESCRIPTION

[0015] In order to clearly illustrate the technical features of the present application, the present application will be further described below in conjunction with the drawings and non-limiting examples.

[0016] SeeFigure 1 The application relates to a biomass boiler flue gas denitration device inlet temperature regulating system, which comprises a boiler DCS control system 4, a furnace 1, a second flue 5, a third flue 8 and a fourth flue 18 which are sequentially connected in sequence with the outlet of the furnace 1, the second flue 5, the third flue 8 and the fourth flue 18 are vertically arranged, the inlet of the second flue 5 is connected with the outlet of the furnace 1, the second flue 5 is connected with the lower end of the third flue 8, the upper end of the third flue 8 is connected with the fourth flue 18 through a furnace top turning flue, a superheater 6 and an evaporator 7 are arranged in the third flue 8 in sequence according to the flue gas flow direction, a denitration device and tail heating surfaces are arranged in the fourth flue 18 in sequence according to the flue gas flow direction, in the embodiment, the tail heating surfaces are the heating surfaces of an economizer and an air preheater, the denitration device 17, the second economizer 19, the secondary air preheater 20, the primary air preheater 21 and the first economizer 22 are arranged in the fourth flue 18 in sequence according to the flue gas flow direction, a dust remover 11 is arranged in the furnace top turning flue, the dust remover 11 divides the furnace top turning flue into a flue before the dust remover 10 and a flue before the denitration device 13, a thermocouple 12 is arranged in the flue before the denitration device 13, and the thermocouple 12 is connected with the boiler DCS control system 4.

[0017] A temperature regulating heat exchanger 9 is arranged in the third flue 8 and located at the upper portion of the evaporator 7, the temperature regulating heat exchanger 9 is provided with a water channel and a flue gas channel, and the flue gas in the third flue 8 can pass through the flue gas channel; the heat source working medium of the temperature regulating heat exchanger 9 is flue gas, and the heated working medium is water; the heating surface of the temperature regulating heat exchanger 9 absorbs the heat in the flue gas to heat the water and simultaneously reduce the temperature of the flue gas; the inlet end of the water channel is connected with a water inlet pipe 14, and the outlet end of the water channel is connected with a water outlet pipe 15; the water inlet pipe 14 is provided with a water inlet pipe valve, the water outlet pipe 15 is provided with a water outlet pipe valve, and the water inlet pipe valve 14-1 and the water outlet pipe valve are connected with the boiler DCS control system 4; a temperature regulating loop 16 is connected between the water inlet pipe 14 and the water outlet pipe 15, and an adjusting valve 16-1 is arranged in the temperature regulating loop 16 and connected with the boiler DCS control system 4; in the embodiment, the heated working medium is water, which can be the internal circulating water of the boiler or water from other sources; for unconventional design, other heat conducting oils or other heat exchange mediums can be used according to the process flow of the user.

[0018] A bypass flue 2 is arranged between the top of the furnace 1 and the flue before the dust remover 10, a flue gas baffle 3 is arranged in the bypass flue 2, the flue gas baffle 3 is connected with an electric actuator, and the electric actuator is connected with the boiler DCS control system 4.

[0019] The boiler flue gas flow process is as follows:

[0020] The flue gas successively passes through the furnace 1, the second flue gas passage, the third flue gas passage, and after successively flushing the superheater 6, the evaporator 7 and the temperature-adjusting heat exchanger 9 in the third flue gas passage, enters the tail convection heating surface through the furnace top turning flue, is dedusted by the dust collector 11 in the turning flue, and is successively passed through the denitration device 17, the economizer 2 19, the secondary air preheater 20, the primary air preheater 21, the economizer 1 22 in the tail convection heating surface, and is discharged by the flue gas outlet 23.

[0021] Temperature-adjusting principle of flue gas:

[0022] When the flue gas temperature is increased due to the combustion of fuel with high heat value, the combustion of fuel with high intensity, the high load of the boiler or other reasons, the thermocouple 12 arranged in the flue 13 before the denitration device measures the flue gas temperature entering the denitration device 17 in real time, and feeds back to the boiler DCS control system through the signal cable. When the flue gas temperature in the flue 13 before the denitration device exceeds the design value, the boiler DCS control system will display an alarm, and the boiler DCS control system controls the opening of the water inlet pipe valve 14-1, the water outlet pipe valve and the regulating valve 16-1 (which can also be manually opened), so as to increase the flow of the heat-absorbing medium entering the temperature-adjusting heat exchanger 9, increase the heat-absorbing amount, and reduce the flue gas temperature. When the thermocouple 12 measures the flue gas temperature in the flue 13 before the denitration device to be within the design range, the signal is fed back to the boiler DCS control system through the signal cable, and the boiler DCS control system controls the regulating valve 16-1 to reduce the opening (which can also be manually adjusted), so as to ensure the appropriate flow of the heat-absorbing medium entering the temperature-adjusting heat exchanger 9, thereby stably controlling the flue gas temperature in the flue 13 before the denitration device, and making the reaction efficiency of the denitration device 17 highest.

[0023] When the boiler furnace 1 burns low calorific value fuel or the combustion condition is poor or the boiler load is low or other causes (such as when the boiler starts or stops) cause the flue gas temperature to decrease, the thermocouple 12 arranged on the denitration device front flue 13 will measure the flue gas temperature entering the denitration device 17 in real time, and feedback to the boiler DCS control system through the signal cable. When the flue gas temperature in the denitration device front flue 13 is lower than the design value, the boiler DCS control system will display an alarm, and the boiler DCS system controls the inlet pipe valve 14-1 and the outlet pipe valve to be closed (which can also be manually closed); then the boiler DCS control system controls the opening of the flue gas baffle 3 on the bypass flue 2, and the high-temperature flue gas in the furnace 1 is directly introduced into the dust collector front flue 10, and the flue gas temperature in the dust collector front flue 10 is increased by mixing a large amount of high-temperature flue gas; when the thermocouple 12 measures that the flue gas temperature in the denitration device front flue 13 is increased to the design interval, the signal is fed back to the boiler DCS control system through the signal cable, and the boiler DCS control system controls the flue gas baffle 3 to reduce the opening degree (which can also be manually adjusted), so as to reduce the high-temperature flue gas entering the dust collector front flue 10, thereby stably controlling the flue gas temperature in the denitration device front flue 13, and the reaction efficiency of the denitration device 17 is the highest.

[0024] Unless otherwise explicitly specified and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or detachably connected, or integrally connected; it can be mechanically connected, it can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above-mentioned terms in the present application can be understood according to the specific circumstances.

[0025] In addition to the technical features described in the specification, they are known to those skilled in the art.

[0026] The above-mentioned embodiments are only for understanding the present application, and are not a limitation on the technical solutions described in the present application. Those skilled in the art can make various changes or modifications on the basis of the technical solutions described in the claims. All equivalent changes or modifications should be covered within the protection scope of the claims of the present application.

Claims

1. A biomass boiler flue gas denitration device inlet temperature regulating system, comprising a boiler DCS control system, a furnace, a second flue, a third flue and a fourth flue connected in sequence with the outlet of the furnace, the second flue, the third flue and the fourth flue are vertically arranged, the inlet of the second flue is connected with the outlet of the furnace, the lower end of the second vertical flue is communicated with the lower end of the third vertical flue, the upper end of the third flue is connected with the upper end of the fourth flue through a furnace top elbow flue, an evaporator and / or a superheater is arranged in the third flue, and a denitration device and a tail heating surface are arranged in the fourth flue in sequence according to the flue gas flow direction; a dust remover is arranged in the furnace top elbow flue, the dust remover divides the furnace top elbow flue into a flue before the dust remover and a flue before the denitration device, characterized in that: The third flue is provided with a temperature adjusting heat exchanger at the upper part of the evaporator and the superheater, and a bypass flue is arranged between the top of the furnace and the flue before the dust remover. ​ 2. The system for regulating the inlet temperature of a biomass boiler flue gas denitration device according to claim 1, characterized in that: The bypass flue is provided with a flue gas baffle connected with an electric actuator connected with the DCS control system of the boiler; the temperature adjusting heat exchanger is provided with a water channel and a flue gas channel, the flue gas in the third flue can pass through the flue gas channel; the heat source working medium of the temperature adjusting heat exchanger is flue gas, and the heated working medium is water; the inlet end of the water channel is connected with a water inlet pipe, and the outlet end of the water channel is connected with a water outlet pipe; the water inlet pipe is provided with a water inlet pipe valve, the water outlet pipe is provided with a water outlet pipe valve, and the water inlet pipe valve and the water outlet pipe valve are connected with the DCS control system of the boiler.

3. The system for regulating the temperature of the inlet of the biomass boiler flue gas denitration device according to claim 2, characterized in that: The water inlet pipe and the water outlet pipe are connected with a temperature adjusting loop provided with an adjusting valve connected with the DCS control system of the boiler.

4. The system for regulating the inlet temperature of a biomass boiler flue gas De-NOx device according to claim 1, wherein: The tail heating surface is the heating surface of the economizer and the air preheater.

5. The system for regulating the inlet temperature of a biomass boiler flue gas denitration device according to claim 1 or 2 or 3 or 4, characterized in that: The denitration device front flue is provided with a thermocouple connected with the DCS control system of the boiler.

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