System for efficiently removing acid gas in combustion tail gas

Abstract

The utility model belongs to the field of environmental protection, and discloses a system for efficiently removing acid gas in combustion tail gas, the system comprises a desulfurization tower, the middle part of the desulfurization tower is connected with a tail gas input pipe, and the top of the desulfurization tower is provided with a tail gas discharge pipe; a first spraying module and a second spraying module are arranged in the desulfurizing tower; the lower part of the desulfurizing tower is connected with a first circulating pump and a second circulating pump; an inlet of the second circulating pump is connected with an absorbent input pipe; and the absorbent input pipe is connected with a flow meter and a control valve. According to the system, the flow-adjustable absorbent input pipe is arranged at the inlet of the second circulating pump, so that the concentration of spraying liquid of the first spraying module is controlled, the concentration of alkali in the spraying liquid is rapidly adjusted, and sufficient absorption of acid gas is guaranteed while the gas phase resistance is reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of environmental protection especially relates to a system for efficiently removing acid gases in combustion tail gas. BACKGROUND

[0002] At present, the main acid gas removal of combustion tail gas in coal-fired power plants, metallurgical industries and chemical reaction tail gas, after the concentration of acid gas increases, the circulating liquid circulation amount of conventional tail gas treatment process increases sharply, which makes the meteorological resistance of tail gas treatment system increase greatly, and the power consumption of circulating acid removal slurry also increases greatly, and the tail gas treatment cannot meet the standard emission.

[0003] CN107321168A discloses a wet flue gas desulfurization absorption tower tray liquid holding amount monitoring system, which realizes tower tray liquid level control through four circulating pumps to dynamically control the tower bottom liquid amount.

[0004] However, it still does not solve the problem of finding a clever balance between meteorological resistance and treatment capacity when the concentration of sulfur dioxide in the tail gas suddenly increases.

[0005] The problem to be solved by the present application is how to develop a system for efficiently removing acid gases in combustion tail gas. CONTENT OF THE UTILITY MODEL

[0006] The utility model aims at providing a system for efficiently removing acid gases in combustion tail gas, which sets an absorbent input pipe with adjustable flow rate at the inlet of the second circulating pump to control the spray liquid concentration of the first spray module, quickly adjust the concentration of alkali in the spray liquid, and ensure the sufficient absorption of acid gases.

[0007] To achieve the above-mentioned purpose, the present application discloses a system for efficiently removing acid gases in combustion tail gas, which comprises a desulfurization tower, a tail gas input pipe connected to the middle part of the desulfurization tower, and a tail gas discharge pipe arranged at the top of the desulfurization tower; a first spray module and a second spray module are arranged in the desulfurization tower; a first circulating pump and a second circulating pump are connected to the lower part of the desulfurization tower, the first circulating pump is connected to the second spray module, and the second circulating pump is connected to the first spray module; an absorbent input pipe is connected to the inlet of the second circulating pump; a flow meter and a control valve are connected to the absorbent input pipe.

[0008] In the above-mentioned system for efficiently removing acid gases in combustion tail gas, a gas distribution module for inputting air is arranged at the bottom of the desulfurization tower.

[0009] In the above-mentioned system for efficiently removing acid gases in combustion tail gas, the gas distribution module is a first gas distribution module for generating nano micro-bubbles and a second gas distribution module for inputting air to the bottom of the tower body.

[0010] In the system for efficiently removing acid gases in combustion tail gas, the bottom of the desulfurization tower is connected with a liquid discharge pump.

[0011] In the system for efficiently removing acid gases in combustion tail gas, a first sensor for detecting the concentration of acid gases in the flue gas is arranged in the tail gas input pipe.

[0012] In the system for efficiently removing acid gases in combustion tail gas, a second sensor for detecting the pH value of the liquid at the bottom of the desulfurization tower is arranged at the bottom of the desulfurization tower.

[0013] In the system for efficiently removing acid gases in combustion tail gas, a controller is further arranged, and the first sensor, the second sensor and the control valve are electrically connected to the controller, and the controller is used for controlling the opening degree of the control valve according to the data of the first sensor and the second sensor.

[0014] In the system for efficiently removing acid gases in combustion tail gas, an alloy tray for enhancing the gas-liquid mass transfer is arranged below the second spraying module.

[0015] In the system for efficiently removing acid gases in combustion tail gas, a Venturi rod is arranged between the first spraying module and the second spraying module, the Venturi rod is used for improving the mass transfer effect between the spraying liquid of the first spraying module and the flue gas, a baffle separation layer and a stirrer are further arranged at the bottom of the desulfurization tower, and the baffle separation layer is arranged above the gas distribution module.

[0016] In the system for efficiently removing acid gases in combustion tail gas, the first spraying module and the second spraying module are arranged from top to bottom, and the liquid inlet height of the first circulating pump is higher than the liquid inlet height of the second circulating pump.

[0017] The beneficial effects of the present application are as follows:

[0018] The present scheme is suitable for a system in which the temperature of combustion tail gas is less than 180℃, and the tail gas contains hydrogen chloride, hydrogen fluoride, sulfur dioxide and other acid gases. The pH difference between the upper and lower spraying modules is small, and by controlling the pH difference between the two spraying modules, the liquid-gas ratio can be significantly reduced while maintaining a high oxidation efficiency.

[0019] Further, by controlling the liquid-gas ratio and distribution ratio under different sulfur dioxide concentrations of flue gas, the system can be maintained at a low liquid-gas ratio, reducing the power of the pump, increasing the unit load by 5-6%, and the outlet sulfur dioxide concentration is lower than 15mg / Nm 3 , close to the ultra-low emission index. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of Example 1.

[0021] Figure 2 Control block diagram for Example 1;

[0022] Figure 3 Structural schematic diagram for another implementation form of Example 1. DETAILED DESCRIPTION

[0023] The utility model will be combined with the embodiment of the utility model, the utility model is clearly and completely described, in the description of the utility model, it needs to be explained that the embodiment is not marked with specific condition, according to conventional condition or the condition suggested by manufacturer, the reagent or instrument used is not marked with manufacturer, all are conventional product that can be obtained by market purchase.

[0024] Example 1

[0025] Reference Figure 1 And 2 A system for efficiently removing acid gas in combustion tail gas, comprising a desulfurization tower 1, a tail gas input pipe 2 is connected to the middle part of the desulfurization tower 1, and a tail gas discharge pipe 3 is arranged at the top of the desulfurization tower 1;A first spraying module 4 and a second spraying module 5 are arranged in the desulfurization tower 1;A first circulating pump 6 and a second circulating pump 7 are connected to the lower part of the desulfurization tower 1, the first circulating pump 6 is connected to the second spraying module 5, and the second circulating pump 7 is connected to the first spraying module 4;An absorbent input pipe 8 is connected to the inlet of the second circulating pump 7;A flow meter 9 and a control valve 10 are connected to the absorbent input pipe 8.The absorbent input pipe 8 is used to input calcium hydroxide solution.

[0026] Its working process is as follows: the pH value of the spraying liquid of the first spraying module is controlled between 6.5 to 6.8 by the second circulating pump, the pH value of the spraying liquid of the second spraying module is controlled between 4.8 to 5.5 by the first circulating pump, and the pH of the slurry in the slurry pool at the bottom of the tower is dynamically controlled to be 4.8-5.5;If the pH of the slurry is lower than 4.8, additional calcium carbonate slurry is supplemented to the bottom of the tower body.When the first spraying module falls to the position of the second spraying module, the liquid of the second spraying module is mixed, and the pH at this time is 5.4 to 5.8, which is the best pH range for the oxidation effect of sulfite;At the same time, this pH control strategy can also keep the slurry at the bottom of the tower stable.

[0027] The overall control strategy is as follows:

[0028] The full load processing flow of the desulfurization tower is 100%, and the full load processing amount is 300,000 m 3 / h;

[0029] When the flow in the tail gas input pipe 2 is 30-50%, the content of sulfur dioxide in the tail gas is less than 8000 mg / m 3At that time, the total liquid-to-gas ratio is controlled at 10-15, and the liquid distribution ratio of the first spray module and the second spray module is 1:10-20;

[0030] When the flow rate in the exhaust gas inlet pipe is 50-80%, the sulfur dioxide content in the exhaust gas is below 8000 mg / m³. 3 At that time, the total liquid-to-gas ratio is controlled at 15-20, and the liquid distribution ratio of the first spray module and the second spray module is 1:10-20;

[0031] When the flow rate in the exhaust gas inlet pipe is 80-100%, the sulfur dioxide content in the exhaust gas is less than 8000 mg / m³. 3 At that time, the total liquid-to-gas ratio is controlled at 20-25, and the liquid distribution ratio of the first spray module and the second spray module is 1:10-20;

[0032] When the flow rate in the exhaust gas inlet pipe is 30-50%, the sulfur dioxide content in the exhaust gas is higher than 8000 mg / m³. 3 And below 10000 mg / m 3 At that time, the total liquid-to-gas ratio is controlled at 10-15, and the liquid distribution ratio of the first spray module and the second spray module is 1:10-15;

[0033] When the flow rate in the exhaust gas inlet pipe is 50-80%, the sulfur dioxide content in the exhaust gas is higher than 8000 mg / m³. 3 And below 10000 mg / m 3 At that time, the total liquid-to-gas ratio is controlled at 15-20, and the liquid distribution ratio of the first spray module and the second spray module is 1:5-10;

[0034] When the flow rate in the exhaust gas inlet pipe is 80-100%, the sulfur dioxide content in the exhaust gas is higher than 8000 mg / m³. 3 And below 10000 mg / m 3 At that time, the total liquid-to-gas ratio is controlled at 20-25, and the liquid distribution ratio of the first spray module and the second spray module is 1:3-5.

[0035] Because the concentration of sulfur dioxide in the flue gas exceeds 10,000 mg / m³ 3 Such cases are rare, so they are not considered in this embodiment. When such cases occur, they can be handled according to the maximum flue gas flow rate, which can meet the relevant requirements.

[0036] We categorize the above operating conditions into low sulfur dioxide concentration conditions (sulfur dioxide < 8000 mg / m³). 3 ), medium to high sulfur dioxide concentration conditions (8000 mg / m³) 3 ≤Sulfur dioxide <10000 mg / m³ 3 The control strategies for the above operating conditions are completely different.

[0037] For low sulfur dioxide concentration conditions, only the tail gas flow needs to be considered, the total liquid gas ratio is controlled according to the tail gas flow, and the liquid distribution ratio is fixed at a suitable value;

[0038] For medium and high sulfur dioxide concentration conditions, not only the total liquid gas ratio (taking the tail gas flow as the consideration index) needs to be considered, but also the intelligent adaptation of the liquid distribution ratio; more specifically, when the tail gas flow is larger, the spraying amount of the first spraying module needs to be increased to improve the absorption effect, at the same time, the pH value of the first spraying module is reduced after absorbing sulfur dioxide, which will increase the liquid amount flowing through the second spraying module, and this part of the liquid will reduce the pH value impact of the high-flow tail gas on the liquid sprayed by the second spraying module, so as to maintain the liquid pH value of the second spraying module near the target value.

[0039] Through the above optimization, under different working conditions, the above strategy is used for processing, tail gas sampling of the tail gas discharge pipe, and the sulfur dioxide content in the tail gas is less than 15mg / Nm 3 , reaching the ultra-low emission index.

[0040] As a preferred control mode of the utility model, the pH value of the slurry at the bottom of the desulfurization tower 1 is 4.8-5.5; if the pH value of the slurry is lower than 4.8, calcium carbonate slurry is additionally supplemented to the bottom of the desulfurization tower 1; the pH value of the spraying liquid of the first spraying module is controlled to be between 6.5 and 6.8 by the second circulating pump, and the pH value of the spraying liquid of the second spraying module is controlled to be between 4.8 and 5.5 by the first circulating pump. After calculation, when the pH value of the calcium hydroxide / calcium carbonate solution reaches 6.8, the absorption efficiency of nearly 99.5% can be reached; at the same time, when the relationship between the pH value and the liquid gas ratio is independently investigated, it is found that when the pH value is close to 7, the liquid gas ratio can be reduced to 12; this also means that by controlling the pH difference of the two spraying modules, the liquid gas ratio can be significantly reduced while maintaining a high oxidation efficiency.

[0041] The circulating pumps of the utility model are not limited to two, but at least two are recommended, and two circulating pumps can more rapidly absorb the dynamic adjustment of the reagent.

[0042] Preferably, the bottom of the desulfurization tower 1 is provided with a gas distribution module 11 for inputting air, and the gas distribution module 11 is generally a gas distribution disc for guiding air into the tower bottom absorption liquid to oxidize sulfite to sulfate.

[0043] Preferably, the bottom of the desulfurization tower 1 is connected with a liquid discharge pump 12.

[0044] In order to realize the automation of the system, a controller 13 is further included, the tail gas input pipe 2 is provided with a first sensor 14 for detecting the concentration of acid gas in the flue gas, and the bottom of the desulfurization tower 1 is provided with a second sensor 15 for detecting the pH value of the tower bottom liquid of the desulfurization tower 1; the first sensor 14, the second sensor 15 and the control valve 10 are electrically connected to the controller 13, and the controller 13 is used for controlling the opening degree of the control valve 10 according to the data of the first sensor 14 and the second sensor 15.

[0045] In the control process, the first sensor 14 and the second sensor 15 continuously transmit the data of the concentration of acid gas in the flue gas and the pH value of the tower bottom absorption liquid, when the concentration of acid gas fluctuates, the controller 13 calculates the required flow of the absorbent according to the preset algorithm, and then controls the opening degree of the control valve 10.

[0046] At the same time, the data of the concentration of acid gas and the pH value of the tower bottom absorption liquid are continuously collected to dynamically adjust the opening degree of the control valve 10.

[0047] Preferably, the first spraying module 4 and the second spraying module 5 are arranged from top to bottom; the liquid inlet height of the first circulating pump 6 is higher than that of the second circulating pump 7.

[0048] Reference Figure 3 , Figure 3 In Figure 1On the basis of further optimization, the first air distribution module 16 for generating micro-nano bubbles is added, the alloy tray 17 for enhancing gas-liquid mass transfer is arranged below the second spraying module, the Venturi rod 18 is arranged between the first spraying module and the second spraying module, the Venturi rod 18 is used to improve the mass transfer effect between the spraying liquid of the first spraying module and the flue gas; the inclined plate separation layer 19 and the agitator 20 are further arranged at the bottom of the desulfurization tower 1, and the inclined plate separation layer 19 is arranged above the air distribution module. The Venturi rod 18 is used, and the flue gas flow rate is greatly improved by adding the Venturi rod 18. Due to the wall attachment effect of the slurry, that is, the spraying liquid of the first spraying module adheres to the Venturi rod 18, when the flue gas contacts at high speed, the original slurry surface is stripped, a new gas-liquid contact surface is formed, the original two-phase mass transfer surface is broken, and thus the gas-liquid two-phase mass transfer rate is accelerated, that is, the SO2 absorption is improved. The agitator 20 is a suspension pump, when the calcium carbonate slurry needs to be supplemented to the tower bottom, the calcium carbonate slurry can be supplemented to the tower bottom through a slurry supplementing pipeline 21. By controlling the spraying pH of the first spraying module and the combination of the Venturi rod 18, the absorption efficiency of sulfur dioxide in the absorption stage can be significantly improved; the agitator 20 keeps the inside of the tower body in a turbulent mixing state, so that the micro-nano bubbles generated by the first air distribution module 16 can be dispersed into the tower body, the micro-nano bubbles and the tower bottom liquid are fully contacted, so that the oxidation reaction can be fully carried out at the bottom of the tower body; through the cooperation of the alloy tray 17, the first air distribution module 16, the second air distribution module and the agitator 20, the oxidation reaction can be kept relatively sufficient during the oxidation reaction at the tower bottom and the spraying process; through the pH control of the Venturi rod 18 and the first spraying module, the sulfur dioxide absorption effect can be significantly improved, and then a better oxidation basis is provided for the subsequent oxidation, so as to further promote the smooth progress of the oxidation reaction.

Claims

1. A system for efficiently removing acidic gases from combustion exhaust gas, comprising a desulfurization tower, wherein an exhaust gas inlet pipe is connected to the middle of the desulfurization tower, and an exhaust gas outlet pipe is provided at the top of the desulfurization tower; a first spray module and a second spray module are provided inside the desulfurization tower; and a first circulation pump and a second circulation pump are connected to the lower part of the desulfurization tower, characterized in that, The first circulating pump is connected to the second spray module, and the second circulating pump is connected to the first spray module; the inlet of the second circulating pump is connected to an absorbent input pipe; a flow meter and a control valve are connected to the absorbent input pipe.

2. The system for efficiently removing acidic gases from combustion exhaust gas according to claim 1, characterized in that, The bottom of the desulfurization tower is equipped with an air distribution module for inputting air.

3. The system for efficiently removing acidic gases from combustion exhaust gas according to claim 2, characterized in that, The air distribution module consists of a first air distribution module for generating nano-microbubbles and a second air distribution module for inputting air to the bottom of the tower.

4. The system for efficiently removing acidic gases from combustion exhaust gas according to claim 1, characterized in that, A drain pump is connected to the bottom of the desulfurization tower.

5. The system for efficiently removing acidic gases from combustion exhaust gas according to claim 1, characterized in that, The exhaust gas inlet pipe is equipped with a first sensor for detecting the concentration of acidic gases in the flue gas.

6. The system for efficiently removing acidic gases from combustion exhaust gas according to claim 5, characterized in that, The bottom of the desulfurization tower is equipped with a second sensor for detecting the pH value of the liquid at the bottom of the desulfurization tower.

7. The system for efficiently removing acidic gases from combustion exhaust gas according to claim 5, characterized in that, It also includes a controller, wherein the first sensor, the second sensor, and the control valve are electrically connected to the controller, and the controller is used to control the opening degree of the control valve based on the data from the first sensor and the second sensor.

8. The system for efficiently removing acidic gases from combustion exhaust gas according to claim 1, characterized in that, The second spray module is provided with an alloy tray below it to enhance gas-liquid mass transfer.

9. The system for efficiently removing acidic gases from combustion exhaust gas according to claim 8, characterized in that, A Venturi rod is provided between the first spray module and the second spray module. The Venturi rod is used to improve the mass transfer effect between the spray liquid and the flue gas in the first spray module. An inclined plate partition layer and a stirrer are also provided at the bottom of the desulfurization tower. The inclined plate partition layer is located above the gas distribution module.

10. The system for efficiently removing acidic gases from combustion exhaust gas according to any one of claims 1-9, characterized in that, The first spray module and the second spray module are arranged from top to bottom; the liquid inlet height of the first circulation pump is higher than that of the second circulation pump.

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