A system and method for collaboratively removing multiple pollutants from a mobile coal-fired startup boiler

Abstract

The present invention discloses a mobile coal-fired startup boiler multiple pollutant coordinated removal system and method, the system comprises a coal-fired startup boiler, a flue gas recirculation flue, a cyclone water film dust removal system, an induced draft fan, an ozone denitrification system, a combined removal of SO2 / NO X The system includes a cyclone water film dust removal system, a cyclone water film dust removal system, a sedimentation tank, and a clarification tank; the ozone denitrification system includes a sodium-calcium double alkali desulfurization tower, an ozone generator, and an ozone ejector; the pollutant collaborative removal method includes the steps of dust removal, denitrification, desulfurization, and dust removal again. The system equipment of the present invention has the characteristics of stable operation, less influence by operation parameters, small project investment scale, low construction difficulty, less power-consuming equipment, mobility, and high utilization rate.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial waste gas and wastewater purification, and more specifically to a system and method for collaboratively removing multiple pollutants from a coal-fired startup boiler. Background Art

[0002] Coal-fired startup boilers are indispensable auxiliary equipment for large thermal power plants. They are the only steam source for the auxiliary steam system when the first unit of the power plant is cold-started, which directly affects the safe startup of the main engine. Compared with large thermal power generation boilers, coal-fired startup boilers are mostly chain boilers, which have the characteristics of low furnace flame temperature, small boiler capacity, low operating parameters and short operating time. However, due to the large area occupied by coal-fired startup boilers and excessive pollutant emissions, many power plants plan to eliminate coal-fired startup boilers.

[0003] Electrostatic dust removal technology is currently the most widely used technology for flue gas dust removal in large thermal power generation boilers. This dust removal technology requires that the flue gas temperature cannot be too low, otherwise it is easy to cause condensation on insulating parts, creepage, and ash accumulation blocking the ash hopper. Therefore, during the boiler startup phase, the electrostatic dust collector cannot be put into operation. In addition, the electrostatic dust collector also has the disadvantages of large investment scale, high power consumption, and high equipment failure rate.

[0004] Selective catalytic reduction technology (SCR) is currently the most widely used technology for flue gas denitrification in large thermal power generation boilers. The denitrification efficiency of this denitrification technology can reach up to 90%. It is the most mature and reliable denitrification technology and requires a reaction temperature of 300-400°C. In addition, the catalyst of this technology is easily deactivated due to dust accumulation and wear.

[0005] Limestone-gypsum wet desulfurization technology is currently the most widely used technology for flue gas desulfurization of large-scale thermal power generation boilers. The technology is mature and the desulfurization efficiency can reach up to 99%. However, the desulfurization wastewater generated by this technology is difficult to treat. Therefore, a system and method that can remove multiple pollutants is urgently needed. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a system and method for the coordinated removal of multiple pollutants from a mobile coal-fired startup boiler, so as to solve the problem of easy deactivation of catalysts in the selective catalytic reduction denitrification technology and the difficulty in treating wastewater in the limestone-gypsum wet desulfurization technology, so as to ensure the qualified emission of flue gas from boilers in each power plant.

[0007] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0008] A mobile coal-fired startup boiler multi-pollutant collaborative removal system, including a coal-fired startup boiler regulated by a PLC automatic control system and software, a flue gas recirculation flue, a cyclone water film dust removal system, an induced draft fan, an ozone denitrification system, and a combined SO removal system. 2 / NO X system, a wet electrostatic precipitator, and a chimney; the cyclone water film dust removal system includes a cyclone water film dust collector, a sedimentation tank connected to the bottom of the cyclone water film dust collector, and a clarification tank respectively connected to the sedimentation tank and the top of the cyclone water film dust collector; the ozone denitrification system includes a sodium-calcium double alkali desulfurization tower and an ozone generator and an ozone injector used in conjunction with it; the top of the coal-fired startup boiler is connected to the lower part of the cyclone water film dust collector through a flue, and the cyclone water film dust collector is connected to the induced draft fan through an inverted U-shaped outlet flue; the induced draft fan is connected to the sodium-calcium double alkali desulfurization tower with a wet electrostatic precipitator on the top through the flue, and the tail end of the wet electrostatic precipitator is connected to the chimney through the flue; the injection end of the ozone injector extends into the flue between the induced draft fan and the sodium-calcium double alkali desulfurization tower, and the flue between the ozone injector and the induced draft fan is connected to a flue gas recirculation flue, and the other end of the flue gas recirculation flue is connected to a secondary wind box.

[0009] To further optimize the technical solution, the cyclone water film dust collector is a cylindrical structure, and the height of the cylinder is 6-10 times the diameter of the cylinder.

[0010] To further optimize the technical solution, a dust concentration measuring instrument for testing dust concentration and spray water drainage concentration is set at the outlet of the cyclone water film dust collector; a flue gas regulating baffle is set at the flue gas inlet of the cyclone water film dust collector; and a guide plate with an adjustable angle is set at the inlet flue of the cyclone water film dust collector.

[0011] Further optimizing the technical solution, the combined removal of SO 2 / NO X The system includes a sodium-lime double alkali desulfurization tower. The lower part of the sodium-lime double alkali desulfurization tower is connected to a first circulating water pump, which is sequentially connected to a reaction tank, a combined sedimentation tank, a circulating tank, and a second circulating water pump. The second circulating water pump is connected to the upper part of the sodium-lime double alkali desulfurization tower.

[0012] To further optimize the technical solution, a flue gas recirculation regulating valve for controlling the flue gas circulation ratio between 10% and 15% is provided on the flue gas recirculation duct, and flexible connections are adopted between the flue gas recirculation duct and the secondary air box.

[0013] To further optimize the technical solution, the bottom end of the coal-fired start-up boiler is connected to a primary wind box, and each device in the pollutant coordinated removal system is regulated by a PLC automatic control system and software.

[0014] The present invention also provides a removal method for a mobile coal-fired startup boiler multi-pollutant coordinated removal system, the flue gas enters the cyclone water film dust collector and flows in the opposite direction with the water mist for dust removal, the ozone sprayed by the ozone injector is fully mixed with the flue gas for denitrification, and then desulfurization is carried out through a sodium-calcium double alkali desulfurization tower, and finally dust removal is carried out by a wet electrostatic precipitator; when the combustion of the coal-fired startup boiler is stable, the flue gas recirculation regulating valve is opened to adjust the flue gas flow rate.

[0015] Further optimize the technical solution, adjust the opening of the flue gas regulating baffle at the flue gas inlet of the cyclone water film dust collector according to the change of flue gas volume during startup, to ensure that the flue gas entering the cyclone water film dust collector has an initial velocity of 20m / s; adjust the angle of the inlet guide plate of the cyclone water film dust collector to ensure that the flue gas has the maximum circumferential velocity along the cyclone water film dust collector under different flue gas flow rates.

[0016] Further optimize the technical solution, control the slurry regeneration amount in the reaction tank during desulfurization to ensure that the pH value of the slurry is within the range of 7 to 8; reasonably select the slurry spray flow rate of the second circulating water pump to control the liquid-gas ratio within the range of 2.5 to 2.6L / m3.

[0017] Due to the adoption of the above technical scheme, the technical progress achieved by the present invention is as follows.

[0018] The present invention provides a system and control method for the coordinated removal of multiple pollutants from a mobile coal-fired startup boiler, which can ensure that dust, nitrogen oxides, sulfur dioxide and other pollutants in the flue gas are stably and efficiently removed throughout the entire startup process of each power plant boiler, achieving standard flue gas emissions without instantaneous excessive emissions of flue gas pollutants, and can also effectively treat desulfurization wastewater from power station boilers. In addition, the system equipment also has the characteristics of stable operation, less impact from operating parameters, small project investment scale, low construction difficulty, less power-consuming equipment, mobility and high utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of a system for collaboratively removing multiple pollutants from a mobile coal-fired startup boiler in the present invention;

[0020] Figure 2 It is a schematic diagram of the structure of the cyclone water film dust removal system in the present invention;

[0021] Figure 3 For the combined removal of SO 2 / NO X A schematic diagram of the system structure;

[0022] Among them: 1. primary wind box, 2. secondary wind box, 3. coal-fired start-up boiler, 4. flue gas recirculation flue, 5. cyclone water film dust collector, 6. induced draft fan, 7. ozone generator, 8. ozone ejector, 9. sodium-calcium double alkali desulfurization tower, 10. wet electrostatic precipitator, 11. chimney, 12. clarification tank, 13. sedimentation tank, 14. flue gas recirculation regulating valve, 15. first circulation water pump, 16. reaction tank, 17. combined sedimentation tank, 18. circulation tank, 19. second circulation water pump. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] A mobile coal-fired boiler multi-pollutant collaborative removal system. Each device in the system is regulated by a PLC automatic control system and software. Figures 1 to 3 As shown, the system comprises a coal-fired startup boiler 3 connected to a primary wind box 1 at the bottom, a flue gas recirculation flue 4, a cyclone water film dust removal system, an induced draft fan 6, an ozone denitrification system, and a combined SO removal system. 2 / NO X system, a wet electrostatic precipitator 10, and a chimney 11.

[0025] The cyclone water film dust removal system includes a cyclone water film dust collector 5, a sedimentation tank 13, and a clarification tank 12. The sedimentation tank 13 is connected to the bottom of the cyclone water film dust collector 5 through a pipeline, the outlet of the sedimentation tank 13 is connected to the clarification tank 12, and the outlet of the clarification tank 12 is connected to the top of the cyclone water film dust collector 5.

[0026] The cyclone water film dust collector 5 is a cylindrical structure, and the height of the cylinder is 6-10 times the diameter of the cylinder. The cyclone water film dust collector 5 has relatively low requirements for the operating environment. It can be put into operation in the initial fuel stage of startup to achieve full-cycle pollutant removal. In addition, the main body of the equipment is made of granite, which has the characteristics of wear resistance and corrosion resistance. The water quality requirements for dust removal are relatively low, and the wastewater discharged by the sodium-calcium double alkali method desulfurization tower 9 system can be used for dust removal. The water is sprayed from the nozzle on the upper part of the cylinder of the cyclone water film dust collector 5 along the tangential direction to the inner wall of the cylinder, and a layer of water film is formed on the inner surface of the cylinder of the cyclone water film dust collector 5. The wastewater containing smoke and dust is discharged from the central discharge pipe at the bottom of the dust collector and enters the sedimentation tank 13 and the clarification tank 12. It is separated and cooled step by step, and then sent to the dust collector for closed-loop circulation. A dust concentration measuring instrument is installed at the outlet of the cyclone water film dust collector 5 to test the dust concentration and the spray water drainage concentration; a flue gas regulating baffle is installed at the flue gas inlet of the cyclone water film dust collector 5; and an adjustable angle guide plate is installed at the inlet flue of the cyclone water film dust collector 5. The dust removal efficiency of the cyclone water film dust collector 5 can reach up to 90%, and the water used by the dust collector is recycled to absorb part of the desulfurization wastewater, which can reduce the cost of desulfurization wastewater treatment.

[0027] The ozone denitrification system includes a sodium-calcium double alkali desulfurization tower 9 and an ozone generator 7 and an ozone injector 8. The sodium-calcium double alkali desulfurization tower 9 uses NaOH solution to absorb SO in the flue gas. 2 The desulfurizer after the reaction is regenerated by lime slurry and then returned to the sodium-calcium double alkali desulfurization tower 9 for recycling. The ozone generator 7 produces ozone by ionizing the high-concentration oxygen delivered by the liquid oxygen storage tank. Ozone oxidizes NO in the flue gas to generate high-valent NO x , and then absorb the high-valent NO through alkaline solution x , speeding up the reaction rate, thereby reducing the NO concentration in the flue gas. The ozone denitrification system is equipped with an independent PLC control system, which incorporates the instrumentation of the raw gas source system and the control of the oxidant preparation system into the denitrification PLC control system. The liquid oxygen flow rate entering the ozone generator 7 is set according to the original flue gas volume and the NOx concentration in the original flue gas as the feedforward signal, and the liquid oxygen flow rate entering the ozone generator 7 is adjusted according to the NOx concentration at the outlet of the sodium-calcium double alkali desulfurization tower 9 as the feedback signal. The equipment in the oxidant preparation area is monitored through the original operation station, which has the advantages of high reliability, flexible configuration, easy installation, and fast operation speed.

[0028] The top of the coal-fired startup boiler 3 is connected to the lower part of the cyclone water film device 5 through a flue, and the cyclone water film dust collector 5 is connected to the induced draft fan 6 through an inverted U-shaped outlet flue; the induced draft fan 6 is connected to the sodium-calcium double alkali desulfurization tower 9 through the flue, and a wet electrostatic precipitator 10 is provided on the top of the sodium-calcium double alkali desulfurization tower 9, and the tail end of the wet electrostatic precipitator 10 is connected to the chimney 11 through the flue. The injection end of the ozone injector 8 extends into the flue between the induced draft fan 6 and the sodium-calcium double alkali desulfurization tower 9, and the nozzle of the ozone injector 8 should be arranged facing the flue gas flow direction, and the distance between the installation position of the ozone injector 8 and the sodium-calcium double alkali desulfurization tower 9 should be able to ensure that the ozone and NO in the flue gas are separated. x The flue between the ozone injector 8 and the induced draft fan 6 is connected to a flue gas recirculation flue 4, and the other end of the flue gas recirculation flue 4 is connected to a secondary wind box 2. The flue gas recirculation flue 4 is provided with a flue gas recirculation regulating valve 14, which is used to control the flue gas circulation ratio at 10% to 15%, so that the carbon content of ash and the amount of nitrogen oxides generated are most economical and optimal; the flue gas recirculation flue 4 and the flue and the secondary wind box 2 are all flexibly connected, and the furnace arch of the secondary wind box 2 on the rear wall of the furnace is moved up by 0.5m, so that the flue gas forms an S-shaped flow at the furnace arch outlet, so as to strengthen the disturbance of the flue gas in the furnace, strengthen the combustion, increase the residence time of the flue gas in the furnace, and allow the carbon black that is not fully burned to be radiated by high-temperature radiation heat for further combustion; in addition, in the turbulent flow, larger dust falls down and burns it in the furnace; after adopting the flue gas recirculation technology, the denitrification efficiency can reach up to 25%.

[0029] Combined SO removal 2 / NO XThe system includes a sodium-lime double alkali desulfurization tower 9, the lower part of which is connected to a first circulating water pump 15, the first circulating water pump 15 is sequentially connected to a reaction tank 16, a combined sedimentation tank 17, a circulating tank 18, and a second circulating water pump 19, and the second circulating water pump 19 is connected to the upper part of the sodium-lime double alkali desulfurization tower 9.

[0030] A removal method for a mobile coal-fired startup boiler multi-pollutant coordinated removal system is as follows.

[0031] The primary bellows 1 accelerates the flow of flue gas in the coal-fired startup boiler 3. The flue gas enters the cyclone water film dust collector 5 and flows in the opposite direction to the water mist for dust removal. The opening of the flue gas regulating baffle at the flue gas inlet of the cyclone water film dust collector 5 is adjusted according to the change of the flue gas volume during the startup process, so that the flue gas entering the cyclone water film dust collector 5 has an initial velocity of 20m / s, and the dust particles in the flue gas enter the water film under the action of centrifugal force. The angle of the guide plate at the inlet of the cyclone water film dust collector 5 is adjusted so that the flue gas has the maximum circumferential velocity along the cyclone water film dust collector 5 under different flue gas flow rates. The dust concentration measuring instrument set at the outlet of the cyclone water film dust collector 5 measures the spray water drainage concentration and adjusts the spray water flow rate according to the dust concentration at the outlet of the cyclone water film dust collector 5 and the spray water drainage concentration.

[0032] Use appropriate ozone injector 8 branch pipe diameter to fully mix the flue gas with the ozone injected into the flue by the injector 8 to denitrify the low-valent NO x Oxidized to high-valent NO x ; During desulfurization, the pH value of the slurry in the reaction tank 16 is controlled to be 7-8; the slurry spray flow rate of the second circulating water pump 19 is reasonably selected to control the liquid-gas ratio at 2.5-2.6L / m 3 Then the flue gas is desulfurized by the sodium-calcium double alkali desulfurization tower 9. 2 , NO concentration to coordinate the adjustment of the liquid oxygen flow entering the ozone generator 7 and the number of branch pipes put into operation, SO in the flue gas 2 and high-valence NO x The Na in the slurry of sodium-calcium double alkali desulfurization tower 9 is 2 CO 3 / NaOH reaction absorption, the slurry after the reaction is pumped into the reaction tank 16 for regeneration through the first circulating water pump 15, and then overflows into the circulation tank 18 after precipitation in the combined sedimentation tank 17, and then sprayed to the sodium-calcium double alkali desulfurization tower 9 through the second circulating water pump 19, and the liquid-gas ratio is controlled at 2.5-2.6L / m 3 range, and control the pH value of the slurry within the range of 7 to 8 to avoid SO 2 Insufficient removal capacity or scaling. Finally, the wet electrostatic precipitator 10 removes dust from the flue gas again.

[0033] In the initial stage of starting the coal-fired startup boiler 3, the furnace temperature is low and the combustion is unstable, so the flue gas recirculation regulating valve 14 needs to be closed to ensure stable combustion of the pulverized coal. When the combustion of the coal-fired startup boiler 3 is stable, the flue gas recirculation regulating valve 14 is adjusted to adjust the flue gas flow rate so that the oxygen content in the furnace is gradually reduced. In addition, during the adjustment process, the NOx concentration in the flue gas at the furnace outlet, the carbon content of the fly ash and other parameters are measured to ensure that the efficient combustion of the pulverized coal is taken into account while reducing the NOx generation.

Claims

1. A mobile coal-fired startup boiler multiple pollutant coordinated removal system, characterized by: The pollutant removal system includes a coal-fired start-up boiler (3) regulated by a PLC automatic control system and software, a flue gas recirculation flue (4), a cyclone water film dust removal system, an induced draft fan (6), an ozone denitrification system, and a combined SO2 / NO removal system. X system, a wet electrostatic precipitator (10), and a chimney (11); the cyclone water film dust removal system comprises a cyclone water film dust collector (5), a sedimentation tank (13) connected to the bottom of the cyclone water film dust collector (5), and a clarification tank (12) respectively connected to the sedimentation tank (13) and the top of the cyclone water film dust collector (5); the ozone denitrification system comprises a sodium-calcium double alkali desulfurization tower (9) and an ozone generator (7) and an ozone injector (8) used in conjunction with the tower; the top of the coal-fired startup boiler (3) is connected to the bottom of the cyclone water film dust collector (5) through a flue, and the cyclone water film dust collector (5) is connected to the induced draft fan (6) through an inverted U-shaped outlet flue; the induced draft fan (6 ) is connected to a sodium-calcium double alkali desulfurization tower (9) having a wet electrostatic precipitator (10) on the top through a flue, and the tail end of the wet electrostatic precipitator (10) is connected to a chimney (11) through the flue; the injection end of the ozone injector (8) extends into the flue between the induced draft fan (6) and the sodium-calcium double alkali desulfurization tower (9), and the flue between the ozone injector (8) and the induced draft fan (6) is connected to a flue gas recirculation flue (4), and the other end of the flue gas recirculation flue (4) is connected to a secondary wind box (2); the flue gas recirculation flue (4) and the flue and the secondary wind box (2) are all flexibly connected, and the furnace arch of the secondary wind box (2) on the rear wall of the furnace is moved up by 0.5m; A dust concentration measuring instrument for testing dust concentration and spray water drainage concentration is provided at the outlet of the cyclone water film dust collector (5); A flue gas regulating baffle is provided at the flue gas inlet of the cyclone water film dust collector (5); and a guide plate with an adjustable angle is provided at the inlet flue of the cyclone water film dust collector (5).

2. A mobile coal-fired startup boiler multiple pollutant coordinated removal system according to claim 1, characterized in that: The cyclone water film dust collector (5) is a cylindrical structure, and the height of the cylinder is 6-10 times the diameter of the cylinder.

3. The mobile coal-fired startup boiler multiple pollutant coordinated removal system according to claim 1 is characterized by: The combined removal of SO2 / NO X The system comprises a sodium-calcium dual alkali desulfurization tower (9), the lower part of the sodium-calcium dual alkali desulfurization tower (9) is connected to a first circulating water pump (15), the first circulating water pump (15) is sequentially connected to a reaction tank (16), a combined sedimentation tank (17), a circulating tank (18), and a second circulating water pump (19), and the second circulating water pump (19) is connected to the upper part of the sodium-calcium dual alkali desulfurization tower (9).

4. The mobile coal-fired startup boiler multiple pollutant coordinated removal system according to claim 1 is characterized by: The flue gas recirculation duct (4) is provided with a flue gas recirculation regulating valve (14) for controlling the flue gas circulation ratio between 10% and 15%, and the flue gas recirculation duct (4) is flexibly connected to the flue and the secondary wind box (2).

5. The mobile coal-fired startup boiler multiple pollutant coordinated removal system according to claim 1 is characterized by: The bottom end of the coal-fired startup boiler (3) is connected to a primary wind box (1), and each device in the pollutant coordinated removal system is regulated by a PLC automatic control system and software.

6. A method for removing multiple pollutants using the system according to any one of claims 1 to 5, characterized in that: The flue gas enters the cyclone water film dust collector (5) and flows in the opposite direction to the water mist for dust removal. The ozone ejected by the ozone ejector (8) is fully mixed with the flue gas for denitrification. The flue gas then passes through the sodium-calcium double alkali desulfurization tower (9) for desulfurization. Finally, the wet electrostatic precipitator (10) is used for dust removal. When the combustion of the coal-fired start-up boiler (3) is stable, the flue gas recirculation regulating valve (14) is opened to adjust the flue gas flow rate.

7. A method for removing multiple pollutants according to claim 6, characterized in that: According to the change of the flue gas volume during the startup process, the opening of the flue gas regulating damper at the flue gas inlet of the cyclone water film dust collector (5) is adjusted to ensure that the flue gas entering the cyclone water film dust collector 5 has an initial velocity of 20m / s; The angle of the guide plate at the inlet of the cyclone water film dust collector (5) is adjusted to ensure that the flue gas has a maximum circumferential velocity along the tangent direction of the cyclone water film dust collector (5) under different flue gas flow rates.

8. A method for removing multiple pollutants according to claim 7, characterized in that: During desulfurization, the amount of slurry regeneration in the reaction tank (16) is controlled to ensure that the pH value of the slurry is within the range of 7 to 8; the slurry spraying flow rate of the second circulating water pump (19) is reasonably selected to control the liquid-gas ratio within the range of 2.5 to 2.6 L / m 3 within the range.

Images