A scrubbing device for waste gas treatment and its control method

Abstract

The present invention belongs to the technical field of waste gas treatment equipment, and discloses a washing device for waste gas treatment and its control method. It includes a washer, a cyclone separator, a washing liquid circulation storage tank, and a booster fan. The outlet of the washer is connected to the inlet of the cyclone separator. The upper outlet of the cyclone separator is communicated with the booster fan. The bottom of the cyclone separator is connected to the washing liquid circulation storage tank. The washing liquid circulation storage tank is connected to the washing liquid storage tank through a pipeline, and a washing liquid supplementary metering pump is provided on the pipeline. An automatic waste washing liquid discharge valve and a discharge pipeline are also connected to the bottom of the washing liquid circulation storage tank. A pH monitor and a liquid level sensor are also installed in the washing liquid circulation storage tank. The washing liquid circulation storage tank is connected to the upper part of the washer through a pipeline, and a washing liquid circulation pump is also provided on the pipeline. It solves the problems of the Venturi washing system in efficiently treating large fluctuations in the flow rate and SO2 concentration of chemical industry tail gas, low discharge pressure, and containing dust and SO3 aerosol.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste gas treatment equipment, and relates to a washing device for waste gas treatment and a control method thereof. Specifically, it relates to the application of a washing device and a control method for waste gas treatment in the desulfurization and dust removal of chemical tail gas. Background Art

[0002] With the development of China's economy, the environmental pollution caused by energy consumption is becoming more and more serious. Among them, atmospheric dust, acid rain, the greenhouse effect, and the destruction of the ozone layer have become the four major killers endangering people's survival. The acidic gas components (SOx and NOx) in waste gas are one of the main causes of environmental pollution such as acid rain and chemical smog. They not only corrode surrounding structures and instruments, but also pose a direct threat to the human body, have a strong irritating effect on the respiratory system, are an important component of PM2.5, and are the main cause of urban smog. At present, the desulfurization technologies commonly used include non-regenerative wet washing process, regenerative wet washing process, and regenerative wet absorption process, each with its own characteristics and disadvantages. The Venturi washing system has also been widely used due to its small floor area and high desulfurization efficiency.

[0003] Chemical tail gas is characterized by large fluctuations in flow rate and SO2 concentration, low discharge pressure, and containing dust and SO3 aerosol. Facing the characteristics of chemical tail gas, how to automatically maintain high-efficiency desulfurization and dust removal effects in the Venturi washing system is an urgent problem to be solved. Summary of the Invention

[0004] To solve the problems of the Venturi washing system in efficiently treating large fluctuations in the flow rate and SO2 concentration of chemical tail gas, low discharge pressure, and containing dust and SO3 aerosol, the present invention provides a washing device for waste gas treatment and a control method thereof, which can realize the functions of adjustable flow rate, automatic replenishment of washing liquid, and automatic discharge of waste liquid.

[0005] The above object of the present invention is achieved by the following technical solutions:

[0006] A washing device for waste gas treatment includes a washer, a cyclone separator, a washing liquid circulation storage tank, and a booster fan. The outlet of the washer is connected to the inlet of the cyclone separator. The upper outlet of the cyclone separator is communicated with the booster fan. The bottom of the cyclone separator is connected to the washing liquid circulation storage tank. The washing liquid circulation storage tank is connected to a washing liquid storage tank through a pipeline, and a washing liquid replenishment metering pump is provided on the pipeline. The bottom of the washing liquid circulation storage tank is also connected with an automatic valve for discharging waste washing liquid and a discharge pipeline. The washing liquid circulation storage tank is also equipped with a pH monitor and a liquid level sensor. The washing liquid circulation storage tank is connected to the upper part of the washer through a pipeline, and a washing liquid circulation pump is also provided on the pipeline.

[0007] The scrubber is internally provided with a Venturi effect inclined plate. The Venturi effect inclined plate is a conical body welded in a circle in the middle of the scrubber. The downward angle between the upper inclined plate and the outer wall is 60°, and the upward angle between the lower inclined plate and the outer wall is 60°. The upper and lower inclined plates converge into a circular hole concentric with the central axis of the scrubber to connect the upper and lower channels of the scrubber.

[0008] An adjusting ball is provided at the circular hole. The bottom of the adjusting ball is connected to an external automatic elevator through a lifting rod and a seal. The annular channel formed by the gap between the circular hole and the adjusting ball is the throat. A differential pressure transmitter is provided in parallel outside the scrubber. The two ends of the differential pressure transmitter pipeline are respectively arranged above and below the Venturi effect inclined plate, and pressure is taken from the cavities above and below the throat respectively.

[0009] A circulating washing liquid injection pipe passes through the upper part of the scrubber. The circulating washing liquid injection pipe is located above the circular hole. A number of spiral nozzles are installed on the circulating washing liquid injection pipe, and the downward spraying area fully covers the circular hole below.

[0010] Further, the connection between the outlet of the scrubber and the inlet of the cyclone separator is specifically as follows: the scrubber and the outer wall of the cyclone separator are connected tangentially. The purpose of connecting the upper outlet of the cyclone separator to the booster fan is to transport the purified tail gas to the chimney for up-to-standard emission.

[0011] Further, the bottom of the washing liquid circulation storage tank is a conical bottom.

[0012] Further, the inlet of the washing liquid replenishment metering pump is connected to the washing liquid storage tank. The outlet of the washing liquid replenishment metering pump is connected to the washing liquid circulation storage tank.

[0013] Further, the diameter of the circular hole is one-third of the inner diameter of the scrubber. The adjusting ball is a stainless steel sphere.

[0014] Further, the lifting rod is perpendicular to the bottom surface of the scrubber, passes through the seal at the center of the bottom of the scrubber, and is connected to an external automatic elevator.

[0015] Further, the inlet of the washing liquid circulation pump is connected to the washing liquid circulation storage tank.

[0016] Further, the outlet of the washing liquid circulation pump is divided into two paths through a tee and merged into a circulating washing liquid injection pipe. After the washing liquid is pressurized, it is sprayed out from the spiral nozzles.

[0017] Further, the washing liquid storage tank is internally filled with washing liquid, and the washing liquid is a 30% sodium hydroxide solution.

[0018] The differential pressure transmitter, automatic lift, pH monitor, washing liquid replenishment metering pump, liquid level sensor, and waste washing liquid discharge automatic valve are respectively connected to the PLC system.

[0019] The control method of the above-mentioned washing device for waste gas treatment is as follows:

[0020] After the tail gas enters the inlet of the scrubber, it first contacts the coverage area of the washing liquid sprayed through the spiral nozzle, playing a role in pre-washing. Most of the SO2 and a small part of the aerosol and dust are removed during this pre-washing process. When the tail gas and the washing liquid pass through the annular throat, the pressure difference at the inlet and outlet of the throat (i.e., the Venturi effect) forms a strong shear force, which further atomizes the droplets of the washing liquid into extremely fine water mist, increasing the contact surface area of the washing liquid and improving the mass transfer efficiency. As a result, most of the dust and aerosol are absorbed by the washing liquid. After the tail gas and the water mist enter the cyclone separator, they rotate and rise at high speed. Under the action of centrifugal force, the small droplets collide with each other in the rotating upward channel, become large droplets, flow into the washing liquid circulation storage tank, and are then transported back to the scrubber through the washing liquid circulation pump for recycling. The purified tail gas flows out from the upper outlet of the cyclone separator and is transported to the chimney for external discharge by the booster fan.

[0021] When the flow rate of the chemical tail gas changes, the differential pressure transmitter outputs a signal to control the automatic lift to drive the lifting rod to drive the regulating ball to rise or fall, changing the annular area of the throat, so that the pressure difference of the differential pressure transmitter is controlled within 5.0 - 6.5 KPa, meeting the atomization effect of the scrubber and realizing the automatic control of the flow rate fluctuation of the chemical tail gas;

[0022] SO2 in the tail gas reacts with the washing liquid (30% sodium hydroxide solution) and finally forms sodium sulfate dissolved in the washing liquid. The washing liquid in the washing liquid circulation storage tank continuously circulates and reacts with SO2, ultimately causing the pH of the circulating washing liquid in the washing liquid circulation storage tank to slowly decrease. When the concentration of the chemical tail gas increases, the pH decrease rate of the circulating washing liquid will slightly accelerate. When the probe of the pH monitor measures that pH ≤ 7, the washing liquid replenishment metering pump automatically starts to replenish fresh washing liquid to improve the desulfurization efficiency; when the probe of the pH monitor measures that pH ≥ 8, the washing liquid replenishment metering pump automatically stops replenishing, realizing the functions of automatically controlling the tail gas concentration fluctuation and automatically replenishing the washing liquid;

[0023] When the liquid level of the washing liquid circulation storage tank measured by the liquid level sensor is ≥ 90%, the output signal automatically starts the waste washing liquid discharge automatic valve to open and discharge the waste washing liquid to the sewage treatment system; when the liquid level sensor measures ≤ 60%, the output signal controls the waste washing liquid discharge automatic valve to close; realizing the automatic discharge of the waste washing liquid.

[0024] The beneficial effects of the present invention compared with the prior art are:

[0025] A scrubbing device for waste gas treatment provided by the present invention can effectively solve the problems of large fluctuations in the flow rate and SO2 concentration of chemical tail gas, low discharge pressure, and the presence of dust and SO3 aerosol. It can automatically adjust within the range of 50 - 150% fluctuation in the tail gas flow rate, and automatically realize the replenishment of fresh scrubbing liquid and the discharge of waste scrubbing liquid, with a high degree of automation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic structural diagram of the scrubbing device for waste gas treatment of the present invention.

[0027] Figure 2 is Figure 1 A - A cross - sectional view of.

[0028] In the figure: 1. Scrubber; 2. Cyclone separator; 3. Scrubbing liquid circulation storage tank; 4. Booster fan; 5. Scrubbing liquid storage tank; 6. Scrubbing liquid circulation pump; 7. Scrubbing liquid replenishment metering pump; 8. Automatic valve for discharging waste scrubbing liquid; 9. Venturi effect inclined plate; 10. Spiral nozzle; 11. Adjusting ball; 12. Lifting rod; 13. Seal; 14. Automatic elevator; 15. Differential pressure transmitter; 16. pH monitor; 17. Scrubbing liquid; 18. Liquid level sensor; 19. Throat; 20. Circulating scrubbing liquid injection pipe. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The present invention will be described in detail below through specific embodiments, but the protection scope of the present invention is not limited. In this embodiment, the differential pressure transmitter, automatic elevator, pH monitor, scrubbing liquid replenishment metering pump, liquid level sensor, and automatic valve for discharging waste scrubbing liquid connected to the PLC system are not limited in model. Embodiment

[0030] A scrubbing device for waste gas treatment, as Figure 1 - Figure 2 shown, includes a scrubber 1, a cyclone separator 2, a scrubbing liquid circulation storage tank 3, and a booster fan 4. The outlet of the scrubber 1 is connected to the inlet of the cyclone separator 2. The upper outlet of the cyclone separator 2 is communicated with the booster fan 4. The bottom of the cyclone separator 2 is connected to the scrubbing liquid circulation storage tank 3. The scrubbing liquid circulation storage tank 3 is connected to the scrubbing liquid storage tank 5 through a pipeline, and a scrubbing liquid replenishment metering pump 7 is provided on the pipeline. The bottom of the scrubbing liquid circulation storage tank 3 is also connected with an automatic valve 8 for discharging waste scrubbing liquid and a discharge pipeline; The scrubbing liquid circulation storage tank 3 is also equipped with a pH monitor 16 and a liquid level sensor 18; The scrubbing liquid circulation storage tank 3 is connected to the upper part of the scrubber 1 through a pipeline, and a scrubbing liquid circulation pump 6 is also provided on the pipeline;

[0031] Inside the scrubber 1, there is a Venturi effect inclined plate 9. The Venturi effect inclined plate 9 is a cone welded around the middle part inside the scrubber 1. The downward angle between the upper inclined plate and the outer wall is 60°, and the upward angle between the lower inclined plate and the outer wall is 60°. The upper and lower inclined plates converge into a circular hole concentric with the central axis of the scrubber 1 to connect the upper and lower channels of the scrubber 1.

[0032] There is an adjusting ball 11 at the circular hole. The bottom of the adjusting ball 11 is connected to an external automatic elevator 14 through a lifting rod 12 and a seal 13. The annular channel formed by the gap between the circular hole and the adjusting ball 11 is the throat 19. There is a parallel differential pressure transmitter 15 outside the scrubber 1. The two ends of the pipeline of the differential pressure transmitter 15 are set at the upper and lower positions of the Venturi effect inclined plate 9 respectively, and the pressure is taken from the upper and lower cavities of the throat 19 respectively.

[0033] A circulating washing liquid injection pipe 20 passes through the upper part of the scrubber 1. The circulating washing liquid injection pipe 20 is located above the circular hole, and there is 1 spiral nozzle 10 installed on the circulating washing liquid injection pipe 20, and the downward spraying area fully covers the lower circular hole.

[0034] Further, the connection between the outlet of the scrubber 1 and the inlet of the cyclone separator 2 is specifically: the scrubber 1 is connected to the outer wall of the cyclone separator 2 in a tangential direction. The purpose of connecting the upper outlet of the cyclone separator 2 to the booster fan 4 is to transport the purified tail gas to the chimney for up-to-standard emission.

[0035] Further, the bottom of the washing liquid circulation storage tank 3 is a conical bottom.

[0036] Further, the inlet of the washing liquid replenishment metering pump 7 is connected to the washing liquid storage tank 5. The outlet of the washing liquid replenishment metering pump 7 is connected to the washing liquid circulation storage tank 3.

[0037] Further, the diameter of the circular hole is one-third of the inner diameter of the scrubber 1. The adjusting ball 11 is a stainless steel sphere.

[0038] Further, the lifting rod 12 is perpendicular to the bottom surface of the scrubber 1, passes through the seal 13 at the central position of the bottom of the scrubber 1, and is connected to the external automatic elevator 14.

[0039] Further, the inlet of the washing liquid circulation pump 6 is connected to the washing liquid circulation storage tank 3.

[0040] Further, the outlet of the washing liquid circulation pump 6 is divided into two paths through a tee and converges into a circulating washing liquid injection pipe 20. After the washing liquid 17 is pressurized, it is sprayed out from the spiral nozzle 10.

[0041] Further, the washing liquid storage tank 5 contains washing liquid, and the washing liquid 17 is a 30% sodium hydroxide solution.

[0042] The differential pressure transmitter 15, the automatic lift 14, the pH monitor 16, the washing liquid replenishment metering pump 7, the liquid level sensor 18, and the waste washing liquid discharge automatic valve 8 are respectively connected to the PLC system.

[0043] The control method of the above-mentioned washing device for waste gas treatment is as follows:

[0044] After the tail gas enters the inlet of the scrubber 1, it first contacts the coverage area of the washing liquid 17 sprayed by the spiral nozzle 10, playing a role in pre-washing. Most of the SO2 and a small part of the aerosol and dust are removed during this pre-washing process; when the tail gas and the washing liquid pass through the annular throat 19, the pressure difference at the inlet and outlet of the throat 19 (i.e., the Venturi effect) forms a strong shear force, which further atomizes the droplets of the washing liquid 17 into extremely fine water mist, increasing the contact surface area of the washing liquid and improving the mass transfer efficiency. As a result, most of the dust and aerosol are absorbed by the washing liquid; after the tail gas and the water mist enter the cyclone separator 2, they rotate upward at high speed. Under the action of centrifugal force, the small droplets collide with each other in the rotating upward channel, turn into large droplets, flow into the washing liquid circulation storage tank 3, and are then transported back to the scrubber 1 by the washing liquid circulation pump 6 for recycling. The purified tail gas flows out from the upper outlet of the cyclone separator 2 and is transported to the chimney for external discharge by the booster fan 4.

[0045] When the flow rate of the chemical tail gas changes, the differential pressure transmitter 15 outputs a signal to control the automatic lift 14 to drive the lifting rod 12 to drive the adjusting ball 11 to rise or fall, changing the annular area of the throat 19, so that the pressure difference of the differential pressure transmitter 15 is controlled within 5.0 - 6.5 KPa, meeting the atomization effect of the scrubber and realizing the problem of automatically controlling the fluctuation of the chemical tail gas flow rate;

[0046] SO2 in the tail gas reacts with the washing liquid (30% sodium hydroxide solution) and finally forms sodium sulfate dissolved in the washing liquid. The washing liquid in the washing liquid circulation storage tank 3 circulates continuously and reacts with SO2, eventually causing the pH of the circulating washing liquid 17 in the washing liquid circulation storage tank 3 to slowly decrease; when the concentration of the chemical tail gas increases, the pH decrease rate of the circulating washing liquid 17 will slightly accelerate. When the probe of the pH monitor 16 measures that pH ≤ 7, the washing liquid replenishment metering pump 7 automatically starts to replenish fresh washing liquid 17 to improve the desulfurization efficiency; when the probe of the pH monitor 16 measures that pH ≥ 8, the washing liquid replenishment metering pump 7 automatically stops replenishing, realizing the functions of automatically controlling the fluctuation of the tail gas concentration and automatically replenishing the washing liquid 17;

[0047] When the liquid level in the washing liquid circulation storage tank 3 measured by the liquid level sensor 18 is ≥ 90%, the output signal automatically starts the opening of the automatic waste washing liquid discharge valve 8 to discharge the waste washing liquid to the sewage treatment system; when the liquid level sensor 18 measures ≤ 60%, the output signal controls the closing of the automatic waste washing liquid discharge valve 8; realizing the automatic discharge of the waste washing liquid.

[0048] The above-described embodiments are only the preferred embodiments of the present invention, and not all the feasible embodiments of the present invention. For those of ordinary skill in the art, any obvious modifications made without departing from the principles and spirit of the present invention should be considered to be included within the scope of the claims of the present invention.

Claims

1. A washing device for waste gas treatment, characterized in that, It includes a scrubber (1), a cyclone separator (2), a scrubbing liquid circulation storage tank (3), and a booster fan (4). The outlet of the scrubber (1) is connected to the inlet of the cyclone separator (2). The upper outlet of the cyclone separator (2) is communicated with the booster fan (4). The bottom of the cyclone separator (2) is connected to the scrubbing liquid circulation storage tank (3). The scrubbing liquid circulation storage tank (3) is connected to a scrubbing liquid storage tank (5) through a pipeline, and a scrubbing liquid supplementary metering pump (7) is provided on the pipeline. The bottom of the scrubbing liquid circulation storage tank (3) is also connected with a waste scrubbing liquid discharge automatic valve (8) and a discharge pipeline; The scrubbing liquid circulation storage tank (3) is also equipped with a pH monitor (16) and a liquid level sensor (18); The scrubbing liquid circulation storage tank (3) is connected to the upper part of the scrubber (1) through a pipeline, and a scrubbing liquid circulation pump (6) is also provided on the pipeline; Inside the scrubber (1), there is a Venturi effect inclined plate (9). The Venturi effect inclined plate (9) is a conical body welded around the middle inside the scrubber (1). The upper inclined plate forms an angle of 60° with the downward outer wall, and the lower inclined plate forms an angle of 60° with the upward outer wall. The upper and lower inclined plates converge into a circular hole concentric with the central axis of the scrubber (1) to connect the upper and lower channel parts of the scrubber (1); An adjusting ball (11) is provided at the circular hole. The bottom of the adjusting ball (11) is connected to an external automatic elevator (14) through a lifting rod (12) and a seal (13); The annular channel formed by the gap between the circular hole and the adjusting ball (11) is the throat (19); A differential pressure transmitter (15) in parallel is provided outside the scrubber (1); Above the scrubber (1), a circulating scrubbing liquid injection pipe (20) is penetrated. The circulating scrubbing liquid injection pipe (20) is located above the circular hole, and a number of spiral nozzles (10) are provided on the circulating scrubbing liquid injection pipe (20).

2. The washing device for waste gas treatment according to claim 1, characterized in that, The differential pressure transmitter (15), the automatic elevator (14), the pH monitor (16), the scrubbing liquid supplementary metering pump (7), the liquid level sensor (18), and the waste scrubbing liquid discharge automatic valve (8) are respectively connected to the PLC system.

3. The washing device for waste gas treatment according to claim 2, characterized in that, The bottom of the scrubbing liquid circulation storage tank (3) is a conical bottom.

4. The washing device for waste gas treatment according to claim 3, characterized in that, The inlet of the scrubbing liquid supplementary metering pump (7) is connected to the scrubbing liquid storage tank (5); The outlet of the scrubbing liquid supplementary metering pump (7) is connected to the scrubbing liquid circulation storage tank (3); The diameter of the circular hole is one-third of the inner diameter of the scrubber (1); The lifting rod (12) is perpendicular to the bottom surface of the scrubber (1), passes through the seal (13) located at the center of the bottom of the scrubber (1), and is connected to the external automatic elevator (14); The inlet of the scrubbing liquid circulation pump (6) is connected to the scrubbing liquid circulation storage tank (3).

5. The washing device for waste gas treatment according to claim 4, characterized in that, The outer walls of the scrubber (1) and the cyclone separator (2) are communicated in a tangential direction.

6. The washing device for waste gas treatment according to claim 5, characterized in that, The scrubbing liquid storage tank (5) is filled with scrubbing liquid, and the scrubbing liquid (17) is a 30% sodium hydroxide solution.

7. A control method for the washing device for waste gas treatment according to claim 6, characterized in that, After the tail gas enters the inlet of the scrubber (1), it first acts on the coverage area of the scrubbing liquid (17) sprayed through the spiral nozzle (10) to play a role in pre-scrubbing. Most of the SO2, a small part of the aerosol and dust are removed during this pre-scrubbing process. When the tail gas and the scrubbing liquid pass through the annular throat (19), the pressure difference between the inlet and outlet of the throat (19) forms a strong shear force, which further atomizes the droplets of the scrubbing liquid (17) into extremely fine water mist, increasing the contact surface area of the scrubbing liquid and improving the mass transfer efficiency. As a result, most of the fine dust and aerosol are absorbed by the scrubbing liquid. After the tail gas and the water mist enter the cyclone separator (2), they rotate upward at high speed. Under the action of centrifugal force, the small droplets collide with each other in the rotating upward channel, become large droplets and flow into the scrubbing liquid circulation storage tank (3), and then are transported back to the scrubber (1) through the scrubbing liquid circulation pump (6) for recycling. The purified tail gas flows out from the upper outlet of the cyclone separator (2) and is transported to the chimney for external discharge by the booster fan (4); When the flow rate of the chemical tail gas changes, the differential pressure transmitter (15) outputs a signal to control the automatic elevator (14) to drive the lifting rod (12) to drive the adjusting ball (11) to rise or fall, changing the annular area of the throat (19), so that the differential pressure of the differential pressure transmitter (15) is controlled at 5.0 - 6.5 KPa, meeting the atomization effect of the scrubber and realizing the problem of automatically controlling the fluctuation of the chemical tail gas flow rate; SO2 in the tail gas reacts with the scrubbing liquid and finally forms sodium sulfate dissolved in the scrubbing liquid. The scrubbing liquid in the scrubbing liquid circulation storage tank (3) continuously circulates and reacts with SO2, finally causing the pH of the circulating scrubbing liquid (17) in the scrubbing liquid circulation storage tank (3) to slowly decrease. When the concentration of the chemical tail gas increases, the pH of the circulating scrubbing liquid (17) will decrease slightly faster. When the probe of the pH monitor (16) measures that pH ≤ 7, the scrubbing liquid replenishment metering pump (7) automatically starts to replenish fresh scrubbing liquid (17) to improve the desulfurization efficiency. When the probe of the pH monitor (16) measures that pH ≥ 8, the scrubbing liquid replenishment metering pump (7) automatically stops replenishing, realizing the functions of automatically controlling the fluctuation of the tail gas concentration and automatically replenishing the scrubbing liquid (17); When the liquid level of the scrubbing liquid circulation storage tank (3) measured by the liquid level sensor (18) is ≥ 90%, the output signal automatically starts the waste scrubbing liquid discharge automatic valve (8) to open and discharge the waste scrubbing liquid to the sewage treatment system. When the liquid level sensor (18) measures ≤ 60%, the output signal controls the waste scrubbing liquid discharge automatic valve (8) to close, realizing the automatic discharge of the waste scrubbing liquid.

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