CN204395778U - A kind of ultra-clean exhaust system for fluidized-bed combustion boiler - Google Patents

Abstract

An ultra-clean exhaust system for a fluidized bed boiler, including a furnace desulfurization device arranged in the dense phase area of the fluidized bed boiler and an SNCR device arranged at the outlet of the furnace, the outlet of the SNCR device is connected to a separator, and the smoke from the separator The gas passes through the superheater and the economizer in sequence and then connects to the high-temperature dust collector. The flue gas outlet of the high-temperature dust collector is connected to the SCR device, the flue gas outlet of the SCR device is connected to the air preheater, and the flue gas outlet of the air preheater is connected to the air preheater. The flue gas inlet of the cryogenic dust collector is connected, the flue gas outlet of the cryogenic dust collector is connected with the flue gas inlet of the desulfurization system, the flue gas from the desulfurization system is discharged to the chimney, and clean flue gas is installed on the pipeline to increase the temperature of the flue gas Generator, this utility model adopts high and low temperature dedusting device for two-stage dedusting and combined with SNCR+SCR mode combined denitrification, and adopts furnace+outside mode desulfurization at the same time, which has high denitrification, desulfurization efficiency, high reliability and adaptability to working conditions Strong, good emission controllability and other advantages.

Description

An ultra-clean exhaust system for fluidized bed boilers

technical field

The utility model belongs to the technical field of boiler environmental protection, in particular to an ultra-clean discharge system for a fluidized bed boiler.

Background technique

Circulating popularized bed boiler technology is a high-efficiency, low-pollution and clean combustion technology that has developed rapidly in the past ten years. It has wide fuel adaptability, high combustion efficiency, high-efficiency desulfurization, low nitrogen oxide (NO _X ) emissions, and high combustion intensity. , Small cross-sectional area of the furnace, large load adjustment range, fast load adjustment, easy to realize comprehensive utilization of ash and slag, simple fuel pretreatment system, few coal feeding points, etc. Therefore, this technology has been widely used commercially in the fields of power station boilers, industrial boilers and waste treatment and utilization.

Operating experience shows that the NO _X emission value of circulating fluidized bed boilers is basically below 400mg/m ³ . The low emission of NO _X from circulating fluidized bed boilers is due to the following two reasons: one _is low-temperature combustion, at which time the nitrogen in the air generally does not generate NO _X ; And make part of the NO _X that has been generated be reduced.

The emission limits for SO ₂ and NO _X in the "Emission Standards for Air Pollution from Thermal Power Plants" (GB13223-2003) are 400mg/m ³ and 450mg/m ³ , respectively. For circulating fluidized bed boilers, only desulfurization in the furnace is required to make _SO2 emissions and _NOx emissions meet the standards, so the original circulating fluidized bed boiler units basically do not have denitrification devices. After the implementation of the "Emission Standards for Air Pollution from Thermal Power Plants" (GB13223-2011), the emission limits for SO ₂ and NO _X were both reduced to 100mg/m ³ , resulting in the existing equipment conditions basically failing to meet environmental protection requirements.

The denitrification technology currently applied to boilers is mainly divided into combustion control technology and flue gas denitrification technology. Combustion control technology includes: CFB boiler combustion technology, air staged combustion, fuel staged combustion, flue gas recirculation, low nitrogen burner technology, combustion optimization; flue gas denitration technology mainly includes: SCR (selective catalytic reduction technology), SNCR ( Selective non-catalytic reduction method), SNCR+SCR. At present, the combustion control technology is mainly used in circulating fluidized bed boilers.

The advantages of SCR are: high denitrification efficiency (70-90%), mature technology, and many domestic applications; the disadvantages are: high investment cost (requires catalyst, cost is more than 3 times that of SNCR), high operating cost (reductant, catalyst ), the installation method changes the boiler structure greatly, the tail is easy to be stained and corroded, and is suitable for new pulverized coal units.

The advantages of SNCR are: small footprint (arranged on the boiler body), low investment cost (1/4-1/3 of SCR), low operating cost (0.003-0.004 yuan/kWh), installation and operation Relatively easy, mature technology; adapt to parameters, loads, and coal quality changes quickly; help reduce average cost, do not catalyze the increase of sulfur trioxide (SO ₃ ), and do not cause blockage or corrosion of the rear heating surface and air preheater; especially It is suitable for the denitrification transformation of CFB units and old units; the disadvantages are: the denitrification efficiency is not high enough, and the amount of ammonia escape is slightly higher than that of SCR.

The characteristics of SNCR+SCR: high denitrification efficiency (40-80%), slightly lower investment cost, slightly lower operating cost (reductant, small amount of catalyst), low ammonia escape, and can greatly reduce the reaction volume of SCR. The escaped ammonia will flow to the downstream SCR system with the flue gas, making its utilization rate more complete. The reducing agent can use urea to replace the more dangerous liquid ammonia. The disadvantages are: less experience in the application of fluidized bed boilers, and there are also problems such as short life of SCR catalysts.

The desulfurization technology currently applied to fluidized bed boilers is mainly in-furnace desulfurization, and flue gas desulfurization is mainly used in pulverized coal boilers. Fluidized bed boilers can control SO ₂ emissions to a low level by adding desulfurizers (limestone, carbide slag, etc.) Desulfurization is difficult to meet the standard and other issues.

Contents of the invention

In order to overcome the above-mentioned shortcomings of the prior art, the purpose of this utility model is to provide an ultra-clean exhaust system for fluidized bed boilers, which has the advantages of high denitrification efficiency, high desulfurization efficiency, high system reliability, and adaptability to working conditions. Strong performance, good controllability of NOx and SO2 emissions, long operating period, and low operating costs, etc., can make the existing fluidized bed boiler meet the requirements of "Emission Standards for Air Pollution from Thermal Power Plants" (GB13223-2011).

In order to achieve the above object, the technical solution adopted by the utility model is:

An ultra-clean exhaust system for a fluidized bed boiler, comprising an in-furnace desulfurization device 17 arranged in the dense phase area of the fluidized bed boiler and an SNCR device 15 arranged at the outlet of the furnace 16, the outlet of the SNCR device 15 is connected to a separator 14. The flue gas exiting the separator 14 passes through the superheater 13 and the economizer 12 in turn, and then connects to the high-temperature dust collector 11. The flue gas outlet of the high-temperature dust collector 11 is connected to the SCR device 22, and the flue gas outlet of the SCR device 22 is connected to the air The preheater 7 is connected, the flue gas outlet of the air preheater 7 is connected to the flue gas inlet of the cryogenic dust collector 6, the flue gas outlet of the cryogenic dust collector 6 is connected to the flue gas inlet of the desulfurization system 1 and is set on the connecting pipeline There is an induced draft fan 23 and a booster fan 26, and a flue gas baffle 3 25 is installed on the connecting pipeline between the induced draft fan 23 and the booster fan 26, and the flue gas exiting the desulfurization system 1 is discharged to the chimney and is installed on the pipeline for lifting the flue gas. Clean flue gas generator 3 at air temperature.

The SCR device 22 is provided with an SCR bypass 10 in parallel, and there is a flue gas baffle 21 on the flue gas inlet connection pipeline between the SCR bypass 10 and the SCR device 22, and the flue gas outlet connection pipe between the SCR bypass 10 and the SCR device 22 There is a flue gas baffle 5 9 on the road, and the SCR bypass 10, flue gas baffle 4 21 and flue gas baffle 5 9 are used to realize the switching of the SCR device 22; the desulfurization system 1 is provided with a desulfurization system in parallel Bypass 24, the desulfurization system 1 is arranged between the flue gas baffle 3 25 and the flue gas baffle 1 4, the desulfurization system bypass 24, the flue gas baffle 3 25 and the flue gas baffle 1 4 are used to realize desulfurization System 1 switchover.

The bottom of the furnace 16 is connected with an air chamber 18 , and the blower 8 supplies air to the air chamber 18 after being preheated by the air preheater 7 .

The lower part of the separator 14 is connected back to the dense phase zone of the fluidized bed boiler through a feeder 19 .

The SNCR device 15 is arranged at the 800-1050°C area at the outlet of the furnace 16, and the furnace desulfurization device 17 is arranged at the lower part of the furnace 16.

The high-temperature dust collector 11 is arranged behind the economizer 12 in the area where the flue gas temperature is 360°C, and the design dust removal efficiency is not lower than 90%. The air preheater 7 is arranged after the SCR device 22 to reduce the flue gas temperature and For heat recovery, the low-temperature dust collector 6 is arranged in the normal exhaust gas temperature area after the air preheater 7 .

The desulfurization system 1 adopts ammonia desulfurization or limestone/gypsum wet desulfurization.

The clean flue gas generator 3 uses natural gas or fuel oil as fuel to increase the flue gas temperature at the outlet of the desulfurization system 1 to ensure the diffusion capacity of the flue gas.

A flue gas baffle 2 is arranged between the clean flue gas generator 3 and the flue gas exiting the desulfurization system 1 .

Compared with the prior art, the beneficial effects of the utility model are:

1) This system adopts high and low temperature dust removal device to carry out two-stage dust removal, and the dust removal efficiency is higher.

2) The SCR device described in this system is arranged in the outlet area of the high-temperature dust collector, so there is less smoke and dust, the catalyst has a better working environment, and the service life is long; at the same time, the working smoke temperature of the SCR device is still high, the catalyst is relatively mature, and the choice is large.

3) The clean flue gas generator set in this system can increase the flue gas temperature at the outlet of the desulfurization system to ensure a high diffusion capacity of the flue gas.

4) The system adopts SNCR+SCR: high denitrification efficiency (40-80%), slightly lower investment cost, slightly lower operating cost (reductant, small amount of catalyst), low ammonia escape, and can greatly reduce the reaction volume of the SCR device. The escaped ammonia will flow to the downstream SCR device with the flue gas flow, making its utilization rate more complete, and the reductant can use urea instead of the more dangerous liquid ammonia; thus, the stability and economy of the system are enhanced, and the ammonia escape Greatly reduced.

5) This system adopts the two-stage desulfurization of the furnace desulfurization combined with the external desulfurization system, which also increases the controllability of _SO2 emissions. The external desulfurization can also recover by-products with certain economic value (ammonium sulfate, gypsum, etc.), reducing operating cost of the desulfurization system.

In summary, this system has the advantages of high denitrification efficiency, high desulfurization efficiency, high system reliability, strong adaptability to working conditions, good controllability of NO _x and SO ₂ emissions, long operation period, and low operation cost.

Description of drawings

Fig. 1 is a structural schematic diagram of the ultra-clean discharge system used in the fluidized bed boiler of the present invention.

Detailed ways

The implementation of the utility model will be described in detail below in conjunction with the accompanying drawings and examples.

In the utility model, the ultra-clean discharge method used for the fluidized bed boiler is mainly realized through the following process links:

In-furnace desulfurization in the dense-phase area of the fluidized bed boiler;

Perform primary denitrification based on SNCR at the furnace outlet;

The flue gas after the primary desulfurization and primary denitrification in the furnace is subjected to high-temperature dedusting, and then the secondary denitrification based on SCR is carried out. The temperature of high-temperature dedusting is above 360°C;

After the second denitrification, the flue gas is heat-exchanged to the normal exhaust gas temperature (130-140°C) and enters the low-temperature dust collector for secondary dust removal;

The flue gas after secondary dedusting is sent to the desulfurization system for secondary desulfurization.

In order to achieve the above method and effectively adapt to various actual working conditions, the utility model provides an ultra-clean exhaust system for fluidized bed boilers, as shown in Figure 1, including The furnace desulfurization device 17 in the zone is located at the lower part of the furnace 16, and the bottom of the furnace 16 is connected with an air chamber 18, and the air chamber 18 communicates with the blower 17 that provides air distribution for the boiler. The SNCR device 15 is arranged in the 800-1050°C area at the outlet of the furnace 16 .

The outlet of the SNCR device 15 is connected to the separator 14, and the lower part of the separator 14 is connected back to the dense-phase zone of the fluidized bed boiler through the feeder 19. The flue gas exiting the separator 14 passes through the superheater 13 and the economizer 12 in sequence, and then connects to the high-temperature dust collector 11. The high-temperature dust collector 11 is arranged behind the economizer 12 in the area where the flue gas temperature is 360°C, and the design dust removal efficiency is not lower than 90 %. The flue gas outlet of the high-temperature dust collector 11 is connected to the SCR device 22, and the flue gas outlet of the SCR device 22 is connected to the air preheater 7. The air preheater 7 is used to reduce the temperature of the flue gas and recover heat, and the blower 8 is connected to the air preheater The air preheater 7 and the air preheater 7 are connected to the air chamber 18 through the fluidizing air duct 20 . The flue gas outlet of the air preheater 7 is connected to the flue gas inlet of the low temperature dust collector 6 , and the low temperature dust collector 6 is arranged in the normal exhaust gas temperature area after the air preheater 7 . The flue gas outlet of the cryogenic dust collector 6 is connected to the flue gas inlet of the desulfurization system 1 and an induced draft fan 23 and a booster fan 26 are arranged on the connecting pipeline, and a flue gas is arranged on the connecting pipeline between the induced fan 23 and the booster fan 26 Baffle 3 25, the flue gas exiting the desulfurization system 1 is discharged to the chimney; in addition, a clean flue gas generator 3 and a flue gas baffle 2 2 are installed to increase the flue gas temperature at the outlet of the desulfurization system to ensure the diffusion of flue gas ability.

In order to adapt to different working conditions, the SCR device 22 is provided with an SCR bypass 10 in parallel, and there is a flue gas baffle 21 on the connecting pipeline between the SCR bypass 10 and the flue gas inlet of the SCR device 22, and the flue gas of the SCR bypass 10 and the SCR device 22 There is a flue gas baffle 5 9 on the gas outlet connecting pipeline, and the SCR bypass 10, flue gas baffle 4 21 and flue gas baffle 5 9 are used to realize the switch between switching on and off of the SCR device 22; the desulfurization system 1 is connected in parallel A desulfurization system bypass 24 is provided, and the desulfurization system bypass 24 is arranged between the flue gas baffle 3 25 and the flue gas baffle 1 4, the desulfurization system bypass 24, the flue gas baffle 3 25 and the flue gas baffle -4 is used to realize the switching of the desulfurization system 1 on and off.

The working principle of the utility model is:

The fuel is burned in the circulating fluidized bed boiler, and the desulfurizer is fed by the desulfurization device 17 in the dense phase zone of the boiler to perform primary desulfurization in the furnace; when the combustion flue gas flows to the outlet of the furnace 16, the SNCR device 15 performs primary denitrification and desulfurization. Remove most of the _NOx ; after furnace desulfurization and primary denitrification, the flue gas passes through the heater 13 and the economizer 12, and then enters the high-temperature dust collector 11 for a dust removal, removing about 90% of the smoke; after that, the high-temperature flue gas enters the SCR device 22 Secondary denitrification is carried out to meet the emission standards, so the temperature of the flue gas is still above 360°C, so the catalyst can use relatively mature products, and the choice is large; the flue gas after denitrification is then entered into the air preheater 7 for heat exchange, and then The flue gas at normal exhaust temperature enters the low-temperature dust collector 6 for secondary dust removal to make the emission meet the standard; the flue gas after dust removal enters the desulfurization system 1 for secondary desulfurization to make the emission reach the standard; finally, the ultra-clean flue gas is discharged from the chimney 5 to atmosphere.

Under normal working conditions, close the SCR bypass damper 10 and the desulfurization system bypass 24, open the flue gas damper 5 9, the flue gas damper 4 21, the flue gas damper 1 4, the flue gas damper 3 25, and pass the flue gas Gas baffle 2 2 adjusts the flue gas temperature at the chimney inlet to increase the flue gas diffusion capacity;

When the desulfurization in the furnace and SNCR denitrification can reach the emission target, open the SCR bypass baffle 10, the desulfurization system bypass 24, close the flue gas baffle 5 9, the flue gas baffle 4 21, the flue gas baffle 1 4, the flue gas baffle Gas baffle three 25, adjust the flue gas temperature at the chimney inlet through the flue gas baffle two 2, to increase the flue gas diffusion capacity;

By adjusting the efficiency of desulfurization and SNCR denitrification in the furnace, this system can easily adjust the ratio of desulfurization and denitration in the furnace to that of desulfurization and denitrification outside the furnace, so as to achieve the optimal working condition with the highest comprehensive energy efficiency of the whole system.

Since this system uses high and low temperature dust removal devices for two-stage dust removal, the dust removal efficiency is higher; at the same time, the SCR device 22 is arranged in the outlet area of the high temperature dust collector 11, with less smoke and dust, better catalyst working environment and long service life; and SCR working smoke The temperature is still high, the catalyst is relatively mature, and the choice is large; the SNCR+SCR method has high denitrification efficiency (40-80%), slightly lower investment cost, slightly lower operating cost (reductant, a small amount of catalyst), low ammonia slip, It can greatly reduce the reaction volume of SCR; the escaped ammonia will flow to the downstream SCR system with the flue gas flow, making its utilization rate more complete, and the reductant can use urea instead of dangerous liquid ammonia; thus making the system stable and efficient While the economy is enhanced, the escape of ammonia is greatly reduced; this system adopts the two-stage desulfurization of the furnace desulfurization combined with the external desulfurization system, which increases the controllability of _SO2 emissions, and the by-products (sulfuric acid) with certain economic value can also be recovered by the external desulfurization ammonium, gypsum, etc.), which reduces the operating cost of the desulfurization system.

Therefore, this system has the advantages of high denitrification efficiency, high desulfurization efficiency, high system reliability, strong adaptability to working conditions, good controllability of NO _x and SO ₂ emissions, long operation period, and low operation cost.

An example of the utility model has been described in detail above, but the content is only a preferred embodiment of the utility model, and cannot be considered as limiting the implementation scope of the utility model. All changes and improvements made according to the scope of application of the utility model should still belong to the scope of protection of the utility model.

Claims (8)

1. the ultra-clean exhaust system for fluidized-bed combustion boiler, comprise the desulfuration in furnace device (17) that is arranged in fluidized-bed combustion boiler emulsion zone and be arranged in the SNCR device (15) that burner hearth (16) exports, it is characterized in that, described SNCR device (15) outlet connects separator (14), the flue gas going out separator (14) accesses hot precipitator (11) successively after superheater (13) and economizer (12), the exhanst gas outlet of hot precipitator (11) is connected with SCR device (22), the exhanst gas outlet of SCR device (22) is connected with air preheater (7), the exhanst gas outlet of air preheater (7) is connected with the smoke inlet of cold precipitator (6), the exhanst gas outlet of cold precipitator (6) is connected with the smoke inlet of desulphurization system (1) and on connecting line, is provided with air-introduced machine (23) and booster fan (26), the connecting line of air-introduced machine (23) and booster fan (26) is provided with gas baffle three (25), the flue gas going out desulphurization system (1) drains into chimney and on pipeline, arranges the clean flue gas generator (3) for promoting flue-gas temperature.

2. according to claim 1 for the ultra-clean exhaust system of fluidized-bed combustion boiler, it is characterized in that, described SCR device (22) has been arranged in parallel SCR bypass (10), SCR bypass (10) and the smoke inlet connecting line of SCR device (22) there is gas baffle four (21), SCR bypass (10) and the exhanst gas outlet connecting line of SCR device (22) have gas baffle five (9), and described SCR bypass (10), gas baffle four (21) and gas baffle five (9) move back switching for the throwing realizing SCR device (22); Described desulphurization system (1) has been arranged in parallel desulphurization system bypass (24), desulphurization system (1) is arranged between gas baffle three (25) and gas baffle one (4), and described desulphurization system bypass (24), gas baffle three (25) and gas baffle one (4) move back switching for the throwing realizing desulphurization system (1).

3. according to claim 1 for the ultra-clean exhaust system of fluidized-bed combustion boiler, it is characterized in that, described burner hearth (16) bottom is connected with air compartment (18), and pressure fan (8) air feed is by leading to air compartment (18) after air preheater (7) preheating.

4. according to claim 3 for the ultra-clean exhaust system of fluidized-bed combustion boiler, it is characterized in that, material returning device (19) tieback is passed through to fluidized-bed combustion boiler emulsion zone in the bottom of described separator (14).

5. according to claim 1 for the ultra-clean exhaust system of fluidized-bed combustion boiler, it is characterized in that, described SNCR device (15) is arranged in burner hearth (16) outlet 800 ~ 1050 DEG C of regions, and described desulfuration in furnace device (17) is arranged in the bottom of burner hearth (16).

6. according to claim 1 for the ultra-clean exhaust system of fluidized-bed combustion boiler, it is characterized in that, described hot precipitator (11) is arranged in economizer (12) flue-gas temperature 360 DEG C of regions afterwards, efficiency of dust collection design is not less than 90%, after described air preheater (7) is arranged in SCR device (22), for reducing flue-gas temperature and heat recovery, described cold precipitator (6) is normal exhaust gas temperature region after being arranged in air preheater (7).

7. according to claim 1 for the ultra-clean exhaust system of fluidized-bed combustion boiler, it is characterized in that, described desulphurization system (1) adopts the ammonia process of desulfurization or wet limestone-gypsum FGD.

8. according to claim 1 for the ultra-clean exhaust system of fluidized-bed combustion boiler, it is characterized in that, between described clean flue gas generator (3) and the flue gas going out desulphurization system (1), be provided with gas baffle two (2).