CN207674430U - A kind of recirculating fluidized bed gasification coupling coal unit peaking generation system - Google Patents

Abstract

The utility model discloses a circulating fluidized bed gasification coupling coal-fired unit peak-shaving power generation system, which includes a gasification system and a coal-fired boiler system. The gasification system mainly includes a fluidized bed gasifier and a cyclone separator. The boiler system mainly includes coal-fired boilers, economizers, SCR denitrification devices and independent combustion chambers; gasification raw materials are gasified in fluidized bed gasifiers, and the generated combustible gases are separated from gas and solid by cyclone separators. The combustible gas is sent into the coal-fired boiler system in two ways, one way is sent into the independent combustion chamber for full combustion to produce auxiliary heating flue gas, and the other way is sent into the coal-fired boiler for direct combustion, and the flue gas produced by the coal-fired boiler is combined with the The auxiliary heating flue gas enters the SCR denitrification device after being mixed. According to the level of boiler load, the coupling mode of the gasification system and the coal-fired boiler system is adjusted to ensure the stable operation of the coupled power generation system under high and low loads and to ensure the denitrification effect of the tail flue gas SCR device.

Description

A circulating fluidized bed gasification coupled coal-fired unit peak regulation power generation system

technical field

The utility model relates to the field of coal and biomass gasification, in particular to a circulating fluidized bed gasification coupling coal-fired unit peak regulation power generation system.

Background technique

There are a large number of large coal-fired power plants in my country, due to excess capacity and changes in electricity load, they need to operate at peak regulation, that is, boiler units operate at low load. However, a major problem facing the low-load operation of coal-fired boilers at present is that during low-load operation, the flue gas temperature is low, which cannot meet the denitrification requirements of the SCR denitrification system, resulting in the denitrification effect not being guaranteed. Coal-fired power plants Flexibility peak shaving capabilities are limited. On the other hand, my country, as a large agricultural country, accumulates a huge amount of biomass raw materials every year but cannot be effectively utilized, and some of them are simply incinerated, resulting in low energy utilization efficiency and aggravating environmental pollution, and the separate combustion or gasification of biomass Utilization is limited by fuel characteristics, resource distribution and logistics costs, making it difficult to achieve large-scale centralized and efficient utilization. Therefore, the efficient and reasonable utilization of biomass energy and the pollution discharge of the energy industry are a technical problem facing energy experts all over the world.

Biomass gasification coupled with co-combustion power generation technology in large coal-fired power plants is one of the important ways for large-scale, efficient and clean utilization of biomass resources. This technology refers to the process in which gasification raw materials undergo partial oxidation-reduction reactions under normal pressure to generate CO, H ₂ , CH ₄ and other hydrocarbon gases.

The operating gas velocity range of the circulating fluidized bed gasifier is between the bubbling fluidized bed and the entrained flow bed, and has a relatively large slip velocity, and the materials in the furnace will move freely under the action of the gasifying agent, showing a fluidized state; The flue gas outlet of the fluidized bed gasifier is equipped with a separator, which can separate the fly ash and carbon particles carried in the gasification gas, and return them to the gasifier for secondary reaction to improve the conversion rate of carbon. CFB gasifier has the characteristics of uniform furnace temperature distribution, fast gasification speed, large processing capacity and high gasification efficiency.

The specific reason why coal-fired power plants cannot achieve flexible peak shaving is that: under low-load operating conditions, on the one hand, it is difficult for the pulverized coal burner in the furnace to ignite and burn stably, which affects the stable and safe operation of the boiler; on the other hand, the smoke entering the SCR denitrification device If the temperature is too low, better denitrification cannot be achieved. In actual production, the generator set may be under various loads. Under low load (such as 20% to 30%), the flue gas temperature of combustion power generation is below 300°C. However, the operating temperature of the catalyst used in the selective catalytic reduction technology (SCR) used in the power industry is generally between 300°C and 400°C. Therefore, once it is in a low-load condition, the SCR denitrification effect cannot meet the NOx emission control requirements. . It can be seen that the low-load flexible peak-shaving power generation technology that couples large-scale coal-fired units with biomass/coal gasification is an effective way to solve the above problems.

Utility model content

The purpose of this utility model is to provide a circulating fluidized bed gasification coupling coal-fired unit flexible peak-shaving power generation system, according to the level of boiler load, adjust the coupling mode of the gasification system and the gas produced by it with the coal-fired boiler system, In order to ensure that the coupled power generation system can operate stably under high and low loads and ensure the denitrification effect of the tail flue gas SCR device.

A circulating fluidized bed gasification coupled coal-fired unit peak regulation power generation system, including a gasification system and a coal-fired boiler system, the gasification system mainly includes a fluidized bed gasifier and a cyclone separator, and the coal-fired boiler system mainly includes a Coal boilers, economizers, SCR denitrification devices and independent combustion chambers;

The gasification raw material is gasified in the fluidized bed gasifier, and the generated combustible gas is separated from gas and solid by the cyclone separator. The combustion produces auxiliary heating flue gas, which is sent to the coal-fired boiler for direct combustion. The flue gas generated by the coal-fired boiler is mixed with the auxiliary heating flue gas after passing through the economizer, and then enters the SCR denitrification device.

The utility model uses a circulating fluidized bed gasification system to produce gas (including CO, H ₂ , CH ₄ , etc.) at a low cost by biomass resources or coal gasification, and at the same time adjusts the gasification system and The coupling method of the gas generated by it and the coal-fired boiler system ensures that the coupled power generation system can operate stably under high and low loads and guarantees the denitrification effect of the tail flue gas SCR device.

The gasification raw material is coal or biomass, and the low-cost gasification raw material (biomass/coal) is used for gasification to produce gas. In the case of large-scale industrial applications such as coupling with coal-fired power generation units, it not only reduces the overall cost and long-term investment, and give full play to the technical advantages of the circulating fluidized bed, such as good fuel adaptability, intense gas-solid phase mixing, and uniform temperature in the circulation loop. Therefore, from the perspective of long-term benefits, it has feasibility and promotion significance. At the same time, it realizes the efficient and clean utilization of biomass, which not only has a higher utilization rate than direct combustion and direct co-combustion with coal, but also can effectively reduce the nitrogen oxide components in the tail gas and reduce pollution emissions.

When biomass is used as the raw material for gasification, under the condition of high-load operation of the coal-fired boiler, the gas generated by the gasification of the biomass is sent to the large-scale high-parameter coal-fired boiler for coupled combustion, so as to realize the high-efficiency power generation of biomass; Under normal circumstances, the gasification gas is used to realize the stable combustion of pulverized coal in the furnace and maintain the temperature of the flue gas entering the SCR, so as to realize the flexible peak shaving of the coal-fired unit. When coal is used as the raw material for gasification, the circulating fluidized bed gasification system can be operated or stopped when the coal-fired boiler is operating at high load, while the gasification gas is used to realize the flexibility of the boiler unit when operating at low load Peak shaving operation.

The gasification raw material is crushed/sieved into particles with an appropriate particle size before gasification, specifically, when the gasification raw material is biomass, it is crushed/sieved into particles with a particle size of 0-20mm before gasification When the gasification raw material is coal, it is crushed/screened into particles with a particle size of 0-10mm before gasification.

Preferably, the gasification raw material is crushed/screened and stored in a silo, and then continuously fed into the fluidized bed gasifier through a feeder.

The fluidized bed gasification furnace uses air or air/steam as the gasification agent.

Preferably, the cyclone separator includes two stages, the combustible gas is separated from the gas and solid through the primary cyclone separator, and the recirculated particles after separation are sent back to the fluidized bed gasifier through the feeder; from the primary cyclone separator The combustible gas that comes out enters the secondary cyclone separator to further separate the solid particles in the combustible gas. After the separated ash passes through the water-cooled spiral ash cooler, it is collected and recycled after cooling down. By setting up a two-stage cyclone separator, most of the biomass ash can be recovered before entering the coal-fired boiler, avoiding a series of follow-up problems caused by boiler slagging and alkali metals (such as heating surface corrosion, etc.).

Further, when the gasification system is a negative pressure system, due to the limitation of high-temperature gas blower equipment, the combustible gas needs to be cooled to 350-400°C through a gas heat exchanger first, and then pressurized by a gas blower before being divided into two parts. into the coal-fired boiler system.

The coal-fired boiler system also includes a diverter regulating valve, through which combustible gas after dedusting is sent into the coal-fired boiler system in two ways.

The combustible gas is treated differently depending on the load. Under high load, all of it can be sent to the coal-fired boiler for mixed combustion with coal, and the original power generation system can be used to generate high-efficiency power generation; The valve guides a certain proportion of combustible gas into the independent combustion chamber for full combustion to generate auxiliary heating flue gas; the remaining combustible gas still enters the coal-fired boiler and co-fires with coal for power generation, and the characteristics of combustible gas that are easy to ignite and burn are used to promote the ignition of pulverized coal And stable combustion, to achieve stable combustion operation in the boiler furnace under low load, the generated flue gas is fully mixed with the above-mentioned auxiliary heating flue gas and then enters the SCR denitrification system for denitrification treatment, ensuring the reliable operation of the SCR denitrification device.

Here, the high load refers to a load condition of 70% or more of the rated load, and the low load refers to a load condition of 20 to 30% of the rated load.

The system can adapt to various loads, while maintaining flue gas denitrification effect. Preferably, under the load condition of 20-30% of the rated load, 8-20% of the combustible gas is sent into the independent combustion chamber for full combustion to generate auxiliary heating flue gas , and the remaining combustible gas is sent to the coal-fired boiler for direct combustion.

The temperature of the mixed gas before entering the SCR denitrification device is 300-400° C. After being processed by this system, the temperature of the gas to be treated before the denitrification device is increased, thereby improving the denitrification effect.

Further, the tail gas after passing through the SCR denitrification device is heated by the air preheater and then discharged through the tail gas treatment device, and the heated air is sent into the coal-fired boiler.

Compared with the prior art, the utility model has the following beneficial effects:

(1) This system takes advantage of the advantages of easy ignition and stable combustion of combustible gas to assist in the stable combustion of coal, that is, to ensure the stable and safe operation of coal-fired boilers under various working conditions, especially low-load conditions, through co-combustion.

(2) For the low-load operation condition, this system specially designed the process of shunting a part of the combustible gas to burn independently and mix it with the low-temperature flue gas entering the SCR, so as to increase the temperature of the flue gas entering the denitrification system and solve the low-load condition of the coal-fired boiler The lower flue gas temperature cannot reach the SCR denitrification temperature window, so there is no need to set up a gas heat exchanger and a high-temperature gas fan separately, which saves energy and simplifies the process.

(3) This system can realize low-temperature gasification, control the precipitation of alkali metals, and at the same time recover most of the biomass ash before entering the coal-fired boiler, avoiding a series of follow-up problems caused by boiler slagging and alkali metals ( Such as heating surface corrosion, etc.).

(4) This system adopts coal and biomass hot gas utilization technology, which has good fuel adaptability, intense gas-solid phase mixing, and high overall thermal efficiency of the system. This system is easy to match with the existing boiler, and the transformation workload is small.

Description of drawings

Figure 1 is a schematic diagram of a negative pressure circulating fluidized bed gasification coupling coal-fired unit peak regulation power generation system of the present invention; in the figure, 1 - pressurized feeder, 2 - fluidized bed gasifier, 3 - primary cyclone separation Device, 4-air compressor, 5-feeder, 6-secondary cyclone separator, 7-ash outlet, 8-gas heat exchanger, 9-high temperature gas fan, 10-splitting control valve, 11-combustion Coal boiler, 12-coal bunker, 13-burner, 14-coal economizer, 15-turbine generator set, 16-independent combustion chamber, 17-induced fan, 18-SCR denitrification device, 19-air preheater, 20-blower, 21-tail gas treatment device;

Figure 2 is a schematic diagram of a positive pressure circulating fluidized bed gasification coupling coal-fired unit peak regulation power generation system of the utility model; in the figure, 1 - pressurized feeder, 2 - fluidized bed gasifier, 3 - primary cyclone separation Device, 4-air compressor, 5-feeder, 6-secondary cyclone separator, 7-ash outlet, 10-splitting control valve, 11-coal-fired boiler, 12-coal bunker, 13-burner, 14- Economizer, 15- Turbine generator set, 16- Independent combustion chamber, 17- Induced fan, 18- SCR denitrification device, 19- Air preheater, 20- Blower, 21- Exhaust gas treatment device.

Detailed ways

In order to better illustrate the utility model, the technical solutions in the embodiments of the utility model are clearly and completely described below in combination with the accompanying drawings in the implementation cases of the utility model.

Example 1

As shown in Figure 1, under the negative pressure system (the negative pressure system refers to the boiler system whose internal pressure is lower than the external atmospheric pressure), the utility model circulating fluidized bed gasification coupling coal-fired unit peak regulation power generation system, including gas Gasification system and coal-fired boiler system, gasification system mainly includes fluidized bed gasifier 2 and cyclone separator 3,6, coal-fired boiler system mainly includes coal-fired boiler 11, economizer 14, SCR denitrification device 18 and independent combustion chamber 16;

Pine wood sawdust is selected as biomass raw material for gasification, and after crushing/screening process, particles with an average particle size in the range of 0-20mm are produced and stored in the biomass material bin for later use.

The biomass is continuously fed into the fluidized bed gasifier 2 through the pressurized feeder 1 at a rate of 20 t/h, and the air supplied by the air compressor 4 is used as the gasification agent in the fluidized bed gasifier 2 for gasification. to produce flammable gases. After leaving the fluidized-bed gasifier 2 with entrained solids in the high-temperature gas, it enters the first-stage cyclone separator 3 for gas-solid separation, and the separated recycled particles are sent back to the fluidized-bed gasifier 2 through the feeder 5 . The other part of the fly ash is removed through the secondary cyclone separator 6, and the separated ash is collected and recycled through the ash outlet 7. The remaining combustible gas containing O ₂ , N ₂ , CO, CO ₂ , H ₂ S, NOx and other components is first cooled by the gas heat exchanger 8 (the temperature of the cooled gas is not lower than the condensation temperature of the contained tar; the heating surface The wall surface temperature is not lower than the tar condensation temperature), pressurized by the high-temperature gas blower 9, and sent to the coal-fired boiler system through the diverter control valve 10.

The gasification system is coupled with a 600MWe coal-fired boiler. The raw materials of the coal-fired boiler are stored in the coal bunker 12 for standby use. After being burned by the burner 13, they enter the coal-fired boiler 11. When the boiler is working at a high load, all combustible gas is sent into the coal-fired boiler. The boiler 11 is co-fired with coal, and the heating steam drives the turbogenerator unit 15 to generate electricity; under low load (20%-30%), after the combustible gas is purified, 15%-20% of the gas is diverted through the diverter regulating valve 10 Complete combustion in the independent combustion chamber 16 and raise the temperature to 1000-1200°C, and the air is supplied by the induced draft fan 17; the remaining 80%-85% combustible gas is sent to the coal-fired boiler 11 as fuel; the flue gas from the boiler passes through the economizer 14 , mixed with the tail gas of the independent combustion chamber 16 to form a gas at 300°C to 400°C, which is sent to the SCR denitrification device 18 to remove nitrogen oxides, and the air is heated by the air preheater 19 and then discharged through the tail gas treatment device 21. The air preheater 19 is supplied with air by blower 20, and the air is sent into coal-fired boiler 11 after being heated.

The industrial analysis and elemental analysis results of the biomass raw material pine sawdust in this example are shown in Table 1, and the composition and volume fraction of the biomass combustible gas obtained after gasification are shown in Table 2.

Table 1. Industrial analysis and elemental analysis of biomass raw material pine sawdust.

In Table 1, M _ad % represents total water content; A _ad % represents ash content; V _ad % represents volatile matter content; FC _ad % represents fixed carbon content; Q _b,ad represents high calorific value; Q _net,ad represents low Calorific value; C _ad % means carbon content; H _ad % means hydrogen content; N _ad % means nitrogen content; S _t,ad % means total sulfur content; O _ad % means oxygen content.

Table 2. Biomass combustible gas composition and volume fraction

gas composition H ₂ CO CH ₄ C _n H _m CO ₂ Volume fraction 4.25% 26.16% 5.08% 1.23% 12.48%

Example 2

As shown in Figure 2, under the positive pressure system (the positive pressure system refers to the boiler system whose internal pressure is greater than the external atmospheric pressure), the utility model circulating fluidized bed gasification coupling coal-fired unit peak regulation power generation system, including gasification system and coal-fired boiler system, the gasification system mainly includes fluidized bed gasifier 2 and cyclone separator 3,6, and the coal-fired boiler system mainly includes coal-fired boiler 11, economizer 14, SCR denitrification device 18 and independent combustion Room 16;

The Zhalainuoer coal is used as gasification raw material for gasification, and the particles with an average particle size in the range of 0-10mm are obtained through the crushing/screening process and stored in the silo for later use.

The coal is continuously fed into the fluidized bed gasifier 2 through the pressurized feeder 1 at a rate of 25 t/h, and the air supplied by the air compressor 4 is used as the gasification agent to be gasified in the fluidized bed gasifier 2 , generating flammable gases. After leaving the fluidized bed gasifier 2 with solid particles entrained by the high-temperature gas, it enters the primary cyclone separator 3 for gas-solid separation, and the separated recycled particles are sent back to the fluidized bed gasifier 2 through the feeder 5 . The other part of the fly ash is removed through the secondary cyclone separator 6, and the separated ash is collected and recycled through the ash outlet 7. The rest of the combustible gas containing O ₂ , N ₂ , CO, CO ₂ , NOx and other components is sent to the coal-fired boiler system through the diverter control valve 10 .

The gasification system is coupled with a 600MWe coal-fired boiler. The raw materials of the coal-fired boiler are stored in the coal bunker 12 for standby use. After being burned by the burner 13, they enter the coal-fired boiler 11. When the boiler is working at a high load, all combustible gas is sent into the coal-fired boiler. The boiler 11 is co-combusted with coal, and the heating steam drives the turbine generator set 15 to generate electricity; under low load (20%-30%), after the combustible gas is purified, 9%-12% of the gas is diverted to the The independent combustion chamber 16 fully burns and heats up to 1100-1300°C, and the air is supplied by the induced draft fan 17; the remaining 88%-91% combustible gas is directly sent to the coal-fired boiler 11 as fuel; the flue gas from the boiler passes through the economizer 14 , mixed with the tail gas of the independent combustion chamber 16 to form a gas at 300°C to 400°C, which is sent to the SCR denitrification device 18 to remove nitrogen oxides, and then the air is heated by the air preheater 19 and then discharged through the tail gas treatment device 21, and the air is preheated The device 19 is supplied with air by the blower 20, and the air is heated and sent to the coal-fired boiler 11.

The results of industrial analysis and elemental analysis of Zhalainuoer coal in this example are shown in Table 3, and the composition and volume fraction of the combustible gas of Zhalainuoer coal obtained after gasification are shown in Table 4.

Table 3. Industrial analysis and elemental analysis of Zhalainuoer coal

In Table 3, M _ad % means total water content; A _ad % means ash content; V _ad % means volatile matter content; FC _ad % means fixed carbon content; Q means calorific value; C _ad % means carbon element content; H _ad % represents hydrogen content; Na _ad % represents nitrogen content; S _t,ad % represents total sulfur content; O _ad % represents oxygen content.

Table 4. Combustible gas composition and volume fraction of Zhalainuoer coal

gas composition H ₂ CO CH ₄ CO ₂ Volume fraction 31.9% 40.1% 4.16% 20.8%

The above is only a preferred specific mode of the utility model, but the scope of protection of the utility model is not limited thereto, and any person familiar with the technical field can easily think of the technical scope disclosed in the utility model Changes or replacements should fall within the protection scope of the present utility model. Therefore, the protection scope of the present utility model should be based on the protection scope of the claims.

Claims (9)

1. a kind of recirculating fluidized bed gasification coupling coal unit peaking generation system, which is characterized in that including gasification system and combustion Coal burning boiler system, gasification system include mainly fluidized-bed gasification furnace and cyclone separator, and coal-burning boiler system includes mainly fire coal Boiler, economizer, SCR denitration device and independent combustion chamber；

Gasified raw material gasifies in fluidized-bed gasification furnace, and the fuel gas of generation carries out gas solid separation, dedusting through cyclone separator Fuel gas afterwards divides two-way to be sent into coal-burning boiler system, is sent into independent combustion chamber fully burning all the way and generates auxiliary heating cigarette Gas, another way are sent into coal-burning boiler and directly burn, and the flue gas that coal-burning boiler generates heats flue gas after economizer with the auxiliary Enter SCR denitration device after mixing.

2. recirculating fluidized bed gasification coupling coal unit peaking generation system according to claim 1, which is characterized in that institute It is coal or biomass to state gasified raw material.

3. recirculating fluidized bed gasification coupling coal unit peaking generation system according to claim 2, which is characterized in that institute State gasified raw material be biomass when, be crushed/be sieved into before gasification grain size for 0-20mm particle；The gasified raw material is coal When, it be crushed/is sieved into the particle that grain size is 0-10mm before gasification.

4. recirculating fluidized bed gasification coupling coal unit peaking generation system according to claim 3, which is characterized in that institute It states gasified raw material and is stored in feed bin after broken/screening, then continuously feed the fluidized-bed gasification furnace through dispenser.

5. recirculating fluidized bed gasification coupling coal unit peaking generation system according to claim 1, which is characterized in that institute It includes two-stage to state cyclone separator, and fuel gas carries out gas solid separation, the recycling particle after separation through primary cyclone Fluidized-bed gasification furnace is sent back to by material returning device；The fuel gas come out from primary cyclone enters secondary cyclone, After the ash separated is by water-cooling spiral device for cooling ash, recycling is collected after cooling.

6. recirculating fluidized bed gasification coupling coal unit peaking generation system according to claim 1, which is characterized in that institute It further includes shunting valve to state coal-burning boiler system, and the fuel gas after dedusting divides two-way to be sent into coal-fired pot by shunting valve Furnace system.

7. recirculating fluidized bed gasification coupling coal unit peaking generation system according to claim 1, which is characterized in that Under 20~30% loading condiction of rated load, 8~20% fuel gas is sent into independent combustion chamber fully burning generation auxiliary Flue gas is heated, remaining fuel gas is sent into coal-burning boiler and directly burns.

8. recirculating fluidized bed gasification coupling coal unit peaking generation system according to claim 1, which is characterized in that into The temperature for entering the mixed gas before the SCR denitration device is 300~400 DEG C.

9. recirculating fluidized bed gasification coupling coal unit peaking generation system according to claim 1, which is characterized in that warp Tail gas after SCR denitration device is discharged by exhaust gas processing device again after heating air by air preheater, the sky after heating Pneumatic transmission enters in coal-burning boiler.