CN108679636A - A kind of soot cleaning system and operation method for thermal power plant's low-level (stack-gas) economizer - Google Patents

Abstract

The invention discloses a kind of soot cleaning systems and operation method for thermal power plant's low-level (stack-gas) economizer, belong to the industrial flue gas cleanings such as coal-fired power station boiler, Industrial Boiler and waste heat recovery field.This soot cleaning system is in the low-level (stack-gas) economizer entrance flue before deduster, including ash cleaning jet nozzle, deashing branch pipe, deashing main pipe and valve, one end of deashing branch pipe is connected with deashing main pipe, deashing branch pipe is set at the changeover portion of low-level (stack-gas) economizer gas approach, it is both provided with valve on each deashing branch pipe, several downward opening ash cleaning jet nozzles are additionally provided on each deashing branch pipe.This system is simple and reasonable, the dust stratification of low-level (stack-gas) economizer section flue when can effectively reduce boiler controller system underrun, improves the uniformity of low-level (stack-gas) economizer section flue gas duct.A kind of soot cleaning system operation method for thermal power plant's low-level (stack-gas) economizer is additionally provided, the drag losses of boiler controller system can be effectively reduced, reduces the energy loss of flue gas, enhanced heat exchange effect.

Description

A kind of ash cleaning system and operation method for low temperature economizer in thermal power plant

technical field

The invention relates to an ash cleaning system and an operation method for a low-temperature economizer in a thermal power plant, belonging to the field of industrial flue gas purification and waste heat recovery of coal-fired power plant boilers and industrial boilers.

Background technique

Coal-fired power plant boilers have a large proportion of exhaust heat loss during operation, accounting for more than 50% of the total boiler heat loss. Some thermal power plants operate with exhaust gas temperatures that are often higher than the design value. Therefore, reducing the exhaust gas temperature of power plant boilers has important practical significance for energy saving and emission reduction. Under this background, low-temperature economizers have been widely used. At present, low-temperature economizers are often used to recover and reuse the waste heat of the discharged high-temperature flue gas. The heat recovered by the low-temperature economizers is currently mainly used for the following aspects: 1. Heating the condensate water on the side of the turbine; 2. Heating the tail gas at the desulfurization outlet 3. Heating boiler secondary air. The low temperature economizer is mainly installed on the flue between the air preheater of the power plant boiler and the front of the electrostatic precipitator. : 1. Reduce boiler exhaust gas temperature, recover flue gas heat, and improve boiler efficiency; 2. Reduce dust specific resistance and actual flue gas volume, improve dust removal efficiency; 3. Reduce desulfurization water replenishment; 4. Reduce dust concentration at the outlet of desulfurization absorption tower, Achieve ultra-low emissions from power plants. At present, most low-temperature economizers are arranged on the horizontal flue between the outlet of the air precipitator and the inlet of the electrostatic precipitator. At the same time, in order to prevent the heat exchange tube of the low-temperature economizer from being severely worn; therefore, when designing the flue, the flue gas flow rate in this section of the flue is designed at about 9m/s. At present, the operating load of most power plant boiler units in my country is low. Therefore, the flue gas flow rate in the flue is lower than the design value (9m/s), and the ability of the flue gas to carry fly ash is weakened, resulting in serious ash accumulation in this horizontal section, which directly affects the economy of the boiler. sex and safety. So far, there has been no reasonable solution to the serious problem of low-load ash accumulation in low-temperature economizer systems.

In response to the above problems, the previous practice is mainly to install an ash hopper and ash conveying system at the bottom of the horizontal flue of the low-temperature economizer; that is, during low-load operation, due to the low flow rate of the flue gas, the ability of the flue gas to carry fly ash is greatly weakened; When the flue gas passes through the low-temperature economizer, the fly ash falls into the ash hopper, and the fly ash is transported to the designated position by auxiliary equipment such as the warehouse pump, thereby solving the problem of ash accumulation at the low-temperature economizer due to the low-load operation of the boiler unit . The main equipment of the system includes: warehouse pump, air compressor, air compression tank, gasification fan, ash unloading system, ash hopper heater, steam system, etc.; the system is relatively complex, with high cost and large floor space.

Contents of the invention

The object of the present invention is to provide an ash removal system for low temperature economizers in thermal power plants. The system has a simple and reasonable structure, and the flue gas disturbance is adjusted by opening and closing valves, thereby improving the ash-carrying capacity of the flue gas. , which can effectively reduce the soot deposition in the flue of the low-temperature economizer section when the boiler unit is running at low load, and improve the uniformity of the flue flow field in the low-temperature economizer section; it also provides a cleaning device for low-temperature economizers in thermal power plants The ash system operation method can effectively reduce the resistance loss of the boiler unit, reduce the energy loss of the flue gas, and enhance the heat exchange effect.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

A dust removal system for a low-temperature economizer in a thermal power plant, which is installed in the flue of the inlet section of the low-temperature economizer before the dust collector, and a heat exchanger group is arranged in the flue, and the heat exchanger group includes m vertically arranged (that is, the cross-section of the flue is set from top to bottom), and n heat exchange modules are arranged in a horizontal arrangement (that is, the flue gas flow direction is set), m and n are both natural numbers greater than 1. The system also includes a soot removal nozzle, a soot removal branch pipe, a soot removal main pipe and a valve. One end of the several ash removal branch pipes is connected to a soot removal main pipe, and the ash removal branch pipe is arranged at the inlet flue of the low temperature economizer. At the transition section, valves are arranged on each branch pipe for cleaning dust, and several cleaning nozzles with downward openings are also arranged on each branch pipe for cleaning dust. When the load is low, open the valve on the ash cleaning branch pipe to purge the flue, strengthen the turbulence of the flue gas, and increase the flow capacity of the fly ash deposited at the bottom of the flue, thereby reducing the ash accumulation in the flue.

In the aforesaid ash removal system used for low-temperature economizers in thermal power plants, the installation height L of the ash removal branch pipe is 1/5 to 1/3 of the total height H of the flue.

In the aforesaid ash removal system used for low-temperature economizers in thermal power plants, the distance between the ash removal nozzles on each ash removal branch pipe is 100 mm to 500 mm.

In the aforesaid ash removal system used for low-temperature economizers in thermal power plants, the ash removal nozzles between two adjacent ash removal branch pipes form a certain angle a, a is 5° to 45°, and the specific angle of a is determined by the ash removal Depends on the number of branches.

In the aforesaid ash removal system for low-temperature economizers in thermal power plants, the ash removal branch pipe is supported inside the flue through a support rod, and the support rod is welded to the inner wall of the flue.

In the aforesaid ash removal system used for low-temperature economizers in thermal power plants, the number of valves is equal to the number of ash removal branch pipes.

In the aforesaid ash removal system for low-temperature economizers in thermal power plants, the purging medium in the ash removal main pipe is the primary air of the power plant, the secondary air of the power plant or compressed air.

A method for operating a dust removal system for a low-temperature economizer in a thermal power plant, using the aforementioned ash removal system for a low-temperature economizer in a thermal power plant, including the following method: adjusting the number and frequency of valve openings according to the load signal of the boiler Therefore, when the boiler load is low and the ash-carrying capacity of the flue gas is weak, the valve needs to be opened to prevent ash accumulation, so that the purge medium in the soot cleaning main pipe enters the flue through the soot cleaning branch pipe and the soot cleaning nozzle and blows downward. Sweeping, through the disturbing effect of the sweeping medium, enhances the disturbance ability of the deposited fly ash, raises it again, and takes away the deposited fly ash under the action of the flue gas.

The above-mentioned operation method of the ash removal system used in the low-temperature economizer of the thermal power plant adjusts the start and stop time of the valve on the ash removal branch pipe according to the boiler load change, and purges once every two hours when the load is low.

Compared with the prior art, the benefits of the present invention are:

1. The structure and process of the cleaning system in the present invention are simple, the amount of reconstruction work is small, and the cost is low. By opening and closing the valve, the turbulence of the flue gas is adjusted, and the ash-carrying capacity of the flue gas is improved, which can effectively Reduce the dust accumulation in the flue of the low-temperature economizer section when the boiler unit is running at low load;

2. By adopting the present invention, the ability of the flue gas to carry fly ash can be enhanced, the ash accumulation in the flue can be reduced, and the harm of unit tripping caused by the ash accumulation in the flue can be avoided; when the boiler unit is operating at full load, due to the influence of ash accumulation The flow field of the original flue is changed, and the original flow field will not be damaged by adopting the present invention, the resistance loss of the boiler unit is greatly reduced, and the economy of the boiler operation is improved; the signal adjustment of the boiler load change feedback is used The start and stop time and frequency of purge valves can reduce the dust accumulation in the flue, increase the heat transfer area of the low-temperature economizer, reduce the energy loss of the flue gas, and enhance the heat transfer effect;

3. The operation method of the dust removal system in the present invention is to adjust the start-stop time of the valve on the dust removal branch pipe according to the change of the boiler load. When the load is low, it will be purged once every two hours; when the boiler load is low, due to The flue gas flow rate is low, and the ability of the flue gas to carry fly ash is weakened, resulting in serious ash accumulation in the flue of the inlet section of the low-temperature economizer. Enter the flue through the ash cleaning branch pipe and the nozzle to purge downward, and through the disturbance of the blowing medium, the disturbance ability of the deposited fly ash is enhanced, and it is raised again to take away the deposited fly ash under the action of the flue gas;

4. The operation method of the ash removal system in the present invention adjusts the number and opening frequency of the ash removal branch pipe valves according to the load signal of the boiler, so that when the boiler load is low and the ash carrying capacity of the flue gas is weak, the ash removal can be adjusted. The number and frequency of branch valve openings are used to enhance the turbulence of the flue gas and improve the ash-carrying capacity of the flue gas;

5. Compared with the "Ash Cleaning Device and Method for New Low-Temperature Economizer" submitted on the same day, the present invention only needs to set up one set of soot cleaning devices, and there are more types of ash cleaning nozzles to choose from, and the scope of application is relatively At the same time, the number of purges during operation is relatively small, and the consumption of purge medium is relatively low.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the partially enlarged schematic diagram of place A among the present invention;

Fig. 3 is a top view of the present invention;

Fig. 4 is the B-B view among Fig. 3;

Fig. 5 is the C-C view among Fig. 2;

Fig. 6 is a D-D view in Fig. 5 .

The meanings of the reference signs: 1-cleaning main pipe, 2-heat exchange module, 3-inlet of low-temperature economizer, 4-cleaning nozzle, 5-cleaning branch pipe, 6-transition section, 7-valve.

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Detailed ways

Embodiment 1 of the present invention: as shown in Figures 1-6, a dust removal system for a low-temperature economizer in a thermal power plant is installed in the 3-stage flue at the entrance of the low-temperature economizer in front of the dust collector, and is set in the flue There is a heat exchanger group, and the heat exchanger group includes m heat exchange modules arranged vertically (that is, the flue section is arranged from top to bottom) and n horizontally arranged (that is, the flue gas flow direction is arranged) In the heat exchange module 2, m and n are both natural numbers greater than 1, specifically, m is 4, and n is 2. The system also includes a soot removal nozzle 4, a soot removal branch pipe 5, a soot removal main pipe 1 and a valve 7. One end of the three ash removal branch pipes 5 is connected to a soot removal main pipe 1, and the ash removal branch pipe 5 is set at a low temperature At the transition section 6 of the flue at the inlet 3 of the economizer, a valve 7 is provided on each branch pipe 5 for cleaning dust, and there are twenty-four nozzles 4 for cleaning dust on each branch pipe 5 . The purging medium in the dust cleaning main pipe 1 is the primary air of the power plant, the secondary air of the power plant or compressed air.

Embodiment 2: As shown in Figures 1-6, a dust removal system for low-temperature economizers in thermal power plants is installed in the 3-stage flue at the entrance of the low-temperature economizer in front of the dust collector, and a heat exchange device is installed in the flue The heat exchanger group includes m heat exchange modules 2 arranged vertically (that is, the flue section is arranged from top to bottom), and n heat exchange modules arranged horizontally (that is, the flue gas flow direction is arranged). Module 2, m and n are all natural numbers greater than 1. The system also includes ash removal nozzle 4, ash removal branch pipe 5, ash removal main pipe 1 and a valve 7. One end of the several ash removal branch pipes 5 is connected to the ash removal main pipe 1, and the ash removal branch pipe 5 is set at a low temperature At the transition section 6 of the flue at the inlet 3 of the economizer, valves 7 are arranged on each branch pipe 5 for cleaning dust, and the number of valves 7 is equal to the number of branch pipes 5 for cleaning dust. Each ash removal branch pipe 5 is also provided with several ash removal nozzles 4 with downward openings. When the load is low, open the valve 7 on the ash removal branch pipe 5 to purge the inside of the flue, strengthen the turbulence of the flue gas, and increase the flow capacity of the fly ash deposited at the bottom of the flue, thereby reducing the ash accumulation in the flue.

The installation height L of the ash removal branch pipe 5 is 1/5-1/3 of the total height H of the flue, and the distance between the ash removal nozzles 4 on each ash removal branch pipe 5 is 100 mm to 500 mm. The ash removal nozzles 4 between two adjacent ash removal branch pipes 5 form a certain angle a, a is 5° to 45°, and the specific angle of a is determined by the number of ash removal branch pipes 5 . Further, the ash-cleaning branch pipe 5 is supported inside the flue through a support rod, and the support rod is welded to the inner wall of the flue. The purging medium in the dust cleaning main pipe 1 is the primary air of the power plant, the secondary air of the power plant or compressed air.

Embodiment 3: As shown in Fig. 1-Fig. 6, a kind of operation method of the ash removal system for the low temperature economizer of the thermal power plant adopts the aforementioned ash removal system for the low temperature economizer of the thermal power plant, including the following methods: According to the load signal of the boiler, the opening quantity and opening frequency of the valve 7 are adjusted, so that when the boiler load is low and the ash-carrying capacity of the flue gas is weak, the valve 7 needs to be opened in order to prevent ash accumulation, so that the purge in the main pipe 1 The medium enters the flue through the soot-cleaning branch pipe 5 and the soot-cleaning nozzle 4 and blows downwards. Through the disturbance of the blowing medium, the disturbance ability of the deposited fly ash is enhanced, and it is raised again. Gray take away. Adjust the start-stop time of the valve 7 on the ash-cleaning branch pipe 5 according to the boiler load change, and purge once every two hours when the load is low.

Embodiment 4: As shown in Figures 1-6, a dust removal system for a low-temperature economizer in a thermal power plant is installed in the flue transition section of the inlet section of the low-temperature economizer after the air preheater and before the dust collector 6, a low-temperature economizer is installed in the flue, and the low-temperature economizer includes m heat exchange modules arranged vertically (that is, the cross section of the flue is set from top to bottom) 2, and n horizontally arranged (that is, the flue gas flow direction Set) heat exchange module 2, the device includes ash removal branch pipe 5, ash removal nozzle 4, ash removal main pipe 1 and valve 7. One end of the several ash removal branch pipes 5 is connected with the ash removal main pipe 1, and the ash removal branch pipe 5 is arranged at the transition section 6 of the inlet 3 flue of the low-temperature economizer, and each ash removal branch pipe 5 is provided with The valve 7 is also provided with several ash removal nozzles 4 with openings facing downwards on each ash removal branch pipe 5 . When the load is low, open the valve 7 on the ash removal branch pipe 5 to purge the inside of the flue, strengthen the turbulence of the flue gas, and increase the flow capacity of the fly ash deposited at the bottom of the flue, thereby reducing the ash accumulation in the flue.

The working principle of an embodiment of the present invention: Fig. 1-Fig. 5 show the schematic diagram of the installation structure when the ash cleaning system of the low temperature economizer of the present invention is used in the existing low temperature economizer system. The low-temperature economizer is composed of m×n heat exchange modules 2 in the form of building blocks. As shown in Figure 1, after the high-temperature flue gas leaves the air preheater, it enters the horizontal flue through the 90° elbow of the flue. When the load is low, open the valve 7 on the branch pipe to purge the flue downwards, strengthen the turbulence of the flue gas, and increase the flow capacity of the fly ash deposited at the bottom of the flue, thereby reducing the ash accumulation in the flue. The device of the invention can effectively reduce the dust deposition in the flue of the low-temperature economizer section when the boiler unit operates at low load, and improve the uniformity of the flow field of the flue in the low-temperature economizer section. The invention also provides an operation method of the dust cleaning device, which can effectively reduce the resistance loss of the boiler unit, reduce the energy loss of the flue gas, and enhance the heat exchange effect.

Claims (9)

1. A kind of cleaning system for the low-temperature economizer of thermal power plant is installed in the flue of the low-temperature economizer inlet (3) section before the dust collector, and a heat exchanger group is arranged in the flue, and the heat exchanger group It includes m heat exchange modules (2) arranged vertically and n heat exchange modules (2) arranged horizontally, m and n are both natural numbers greater than 1, and it is characterized in that it includes dust cleaning nozzles (4), cleaning Ash branch pipe (5), ash removal main pipe (1) and valve (7), one end of the several ash removal branch pipes (5) is connected with ash removal main pipe (1), and the ash removal branch pipe (5) is set At the transition section (6) of the flue at the entrance (3) of the low-temperature economizer, a valve (7) is provided on each ash removal branch pipe (5), and several valves (7) are also installed on each ash removal branch pipe (5). Cleaning nozzles (4) with downward openings. 2. The ash removal system for low-temperature economizers in thermal power plants according to claim 1, wherein the installation height L of the ash removal branch pipe (5) pipeline is 1/5 to 1/5 of the total height H of the flue. 1/3. 3. The ash removal system for low-temperature economizers in thermal power plants according to claim 1, characterized in that the distance between the ash removal nozzles (4) on each ash removal branch pipe (5) is 100 mm to 500 mm. 4. The ash removal system for low temperature economizers in thermal power plants according to claim 1, characterized in that the ash removal nozzles (4) between two adjacent ash removal branch pipes (5) form a certain angle a , a is 5°～45°. 5. The ash removal system for low-temperature economizers in thermal power plants according to claim 1, characterized in that, the ash removal branch pipe (5) is supported inside the flue through a support rod, and the support rod is welded to the flue on the inner wall of the road. 6. The ash removal system for low temperature economizers in thermal power plants according to claim 1, characterized in that the number of valves (7) is equal to the number of ash removal branch pipes (5). 7. The ash cleaning system for low-temperature economizers in thermal power plants according to claim 1, characterized in that, the purging medium in the soot cleaning main pipe (1) is the primary wind of the power plant, the secondary wind of the power plant or compressed air. 8. A method for operating the ash removal system of a low-temperature economizer in a thermal power plant, using the ash removal system for a low-temperature economizer in a thermal power plant according to any one of claims 1-7, characterized in that it includes the following methods : According to the load signal of the boiler, the opening quantity and opening frequency of the valve (7) are adjusted, so that when the boiler load is low and the ash-carrying capacity of the flue gas is weak, the valve (7) needs to be opened in order to prevent ash accumulation, so that the ash cleaning main pipe The purge medium in (1) enters the flue through the ash removal branch pipe (5) and the ash removal nozzle (4) to purge downwards. Through the disturbance of the purge medium, the disturbance ability of the deposited fly ash is enhanced, and the ash is raised again. , The deposited fly ash is taken away under the action of flue gas. 9. the ash removal system operating method for the low temperature economizer of thermal power plant according to claim 8, is characterized in that, adjusts the start-stop time of valve (7) on the ash removal branch pipe (5) according to boiler load variation, low Purge every two hours while on load.