System for removing SO3 in flue gas by using alkali liquor

Abstract

The utility model discloses a system for removing SO3 in flue gas by using alkali liquor. The system comprises an alkali liquor delivery pump, a spray gun, a compressed air device, a powder bin, a dilution water tank, a sodium carbonate dissolving tank, a storage tank, an alkali liquor transfer pump, a dilution water pump and a metering distribution module, the powder bin is connected with the Roots blower, and the Roots blower is connected with the dissolving tank; the dissolving tank is communicated with the alkali liquor transfer pump, and the alkali liquor transfer pump is connected with the storage tank; the metering distribution module comprises an alkali liquor pipeline and a dilution water pipeline, demineralized water is connected with a liquid inlet of a dilution water tank, and the dilution water tank is connected with a water feeding pump and a dilution water pump; the water feeding pump is connected with the dissolving tank; the dilution water pump is connected with the dilution water pipeline; the storage tank is connected with an alkali liquor delivery pump; the alkali liquor delivery pump is connected with an alkali liquor pipeline; the metering distribution module is connected with the double-fluid spray gun; the spray gun is connected with a compressed air device. According to the device, SO3 in the flue gas is removed, the content of SO3 in the flue gas is reduced, and follow-up blockage to a catalyst and an air preheater and low-temperature corrosion to the air preheater are reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of alkaline solution desulfurization treatment, in particular to a system for removing SO3 in flue gas with alkaline solution, which is applied to the field of boiler flue gas desulfurization and denitrification treatment in thermal power plants, steel mills, chemical plants, etc. and to the prevention of low-temperature corrosion and blockage of air preheaters. Background Art

[0002] Coal-fired boilers produce a large amount of pollutants during the combustion process. Since coal contains a certain amount of sulfur, a certain concentration of sulfur dioxide and sulfur trioxide will be produced in the final flue gas. Sulfur in coal exists in three forms: organic sulfur (combined with C, H, O, etc. to form complex compounds), pyrite sulfur (FeS2) and sulfate sulfur. Sulfate sulfur is generally no longer oxidized and appears as ash. Combustible sulfur only contains the first two forms.

[0003] The sources of SO3 in coal-fired boiler flue gas are mainly the following:

[0004] (1) During the combustion process in the furnace, part of the sulfur in the coal is directly converted into SO3; during the heat exchange process of the flue gas on the tail heating surface, it is catalytically oxidized by the metal pipe wall and fly ash, and part of the SO2 is converted into SO3;

[0005] (2) The catalyst in the SCR denitrification system also has a strong catalytic oxidation effect, catalytically oxidizing SO2 in the flue gas into SO3; especially when running at low load, the catalytic oxidation of SO2 into SO3 will increase sharply;

[0006] The hazards of SO3 are as follows:

[0007] (1) Generation of ammonium bisulfate: Under SCR operating conditions, NH3 that has not completely reacted in denitrification will react with SO3 to generate ammonium bisulfate. The increase in SO3 concentration will lead to an increase in the concentration of ammonium bisulfate, causing the minimum continuous ammonia injection temperature of the denitrification device to increase, resulting in the SCR denitrification device being unable to be put into operation under low load conditions, and the availability of the denitrification device being reduced.

[0008] (2) Increase the acid dew point of flue gas: The acid dew point of flue gas depends on the concentration of SO3 and H2O in the flue gas. The acid dew point of flue gas increases with the increase of SO3 concentration, which will cause serious corrosion in the low-temperature section of the air preheater.

[0009] (3) Air preheater ash accumulation and blockage: Under SCR operating conditions, NH3 that has not completely reacted with denitrification will react with SO3 to form ammonium bisulfate. Ammonium bisulfate is a very viscous and highly corrosive substance. The viscosity of ammonium bisulfate will cause a large amount of fly ash to cover the surface of the air preheater, causing the air preheater to be blocked, resulting in an increase in the operating resistance of the air preheater, an increase in operating costs, and a decrease in equipment life.

[0010] (4) After SO3 enters the wet flue gas desulfurization process, it easily forms aerosols, causing the chimney to emit "blue smoke" and "smoke plume tails", which are extremely unpleasant to the senses. At the same time, the direct emission of SO3 is the main source of acid rain.

[0011] At present, SO3 removal mainly relies on wet desulfurization, which can ensure that the amount of SO3 discharged into the atmosphere is reduced, but it cannot eliminate the adverse effects of SO3 on the front-end denitrification device and air preheater;

[0012] Therefore, how to remove SO3 at the front end of denitrification and reduce the harm to subsequent denitrification equipment and air preheaters is a technical problem that technicians in this technical field urgently need to solve. Utility Model Content

[0013] The utility model is to overcome the shortcomings of the above-mentioned prior art and provide a system for removing SO3 from flue gas with alkali solution. The utility model can remove SO3 from flue gas, reduce the content of SO3 in flue gas, reduce subsequent blockage of catalyst and air preheater and low-temperature corrosion of air preheater.

[0014] The technical solution adopted by the utility model to solve its technical problems is:

[0015] A system for removing SO3 from flue gas with alkali solution, comprising a powder bin for containing sodium carbonate dry powder, a dilution water tank, a sodium carbonate dissolving tank, a storage tank, an alkali solution transfer pump, an alkali solution delivery pump, a dilution water pump, a metering and distribution module, a spray gun, and a compressed air device; the powder bin is provided with a dry powder feed port, the bottom of the powder bin is connected to an outlet pipe of a Roots blower, and the outlet of the Roots blower is connected to a sodium carbonate dry powder inlet of a dissolving tank through a pipe; the liquid outlet of the dissolving tank is connected to a liquid inlet of the alkali solution transfer pump through a pipe, and the liquid outlet of the alkali solution transfer pump is connected to a liquid inlet of a storage tank through a pipe;

[0016] The metering and dispensing module comprises an alkali solution pipeline and a dilution water pipeline. The desalted water is connected to the inlet of the dilution water tank through a pipeline, and the outlet of the dilution water tank is respectively connected to the inlet of the water supply pump and the dilution water pump through pipelines; the outlet of the water supply pump is connected to the inlet of the dissolution tank through a pipeline, and the outlet of the dilution water pump is connected to the dilution water inlet of the dilution water pipeline of the metering and dispensing module through a pipeline; the outlet of the storage tank is connected to the inlet of the alkali solution delivery pump through a pipeline, and the outlet of the alkali solution delivery pump is connected to the alkali solution inlet of the alkali solution pipeline of the metering and dispensing module through a pipeline; the mixed solution at the outlet of the metering and dispensing module is connected to the inlet of the dual-fluid spray gun through a pipeline;

[0017] The spray gun is connected to the compressed air device.

[0018] The compressed air device includes an adsorption dryer and a compressed air storage tank. The compressed air main pipe is connected to the air inlet of the adsorption dryer through a gas pipeline, the air outlet of the adsorption dryer is connected to the air inlet of the compressed air storage tank through a pipeline, and the air outlet of the compressed air storage tank is connected to the air inlet of the dual-fluid spray gun through a pipeline.

[0019] Electric regulating valves and flow meters are respectively provided on the alkali solution pipeline and the dilution water pipeline.

[0020] The dilution water pump comprises a dilution water pump A and a dilution water pump B which are arranged in parallel.

[0021] The alkali liquid delivery pump includes an alkali liquid delivery pump A and an alkali liquid delivery pump B which are arranged in parallel.

[0022] The spray gun adopts a double-fluid spray gun.

[0023] The powder bin discharge port is connected to the Roots blower outlet pipe through a feeding shoe, and the Roots blower outlet pipe is connected to the dissolving tank feed port.

[0024] A connected weighing tank is provided at the lower part of the powder bin, and the weighing tank is connected to the feeding boot through a pipeline, a valve switch is provided on the pipeline, and a vacuum pressure release valve and an inspection hole are provided at the upper part of the powder bin.

[0025] The dissolving tank is provided with a dissolving tank agitator.

[0026] The water supply pump is also connected to the liquid inlet pipeline of the alkali solution transfer pump and the liquid inlet pipeline of the alkali solution delivery pump through corresponding pipelines.

[0027] The beneficial effects of the utility model are:

[0028] 1. The utility model's system for removing SO3 from flue gas with alkali solution can remove SO3 at the front end of denitrification, protect the subsequent denitrification catalyst and air preheater from being blocked, reduce low-temperature corrosion of the air preheater, reduce damage to subsequent denitrification devices and air preheaters, and reduce operating costs.

[0029] 2. The outlet of the dual-fluid spray gun is inserted into the SCR inlet flue, and the atomized alkaline solution is fully mixed with the flue gas to achieve the effect of removing sulfur trioxide. The injection amount of the alkaline absorbent is controlled by an electric regulating valve, and the real-time injection amount of the alkaline absorbent is mastered by a flow meter.

[0030] 3. The sodium carbonate dissolving tank and storage tank of the utility model are separately arranged. Since the alkali solution delivery pump is in continuous operation, the preparation and storage of the sodium carbonate alkaline solution are separated by separately arranging the dissolving tank and the storage tank, thereby minimizing the impact on the continuous delivery of the sodium carbonate solution by the system and not affecting the continuous operation of the alkali solution delivery pump.

[0031] 4. The flow rate regulation of the dilution water and the sodium carbonate solution of the utility model is concentrated in the metering and distribution module, which can conveniently uniformly adjust the flow rates of the dilution water and the sodium carbonate solution in the metering and distribution module according to the boiler load, the flue gas flow rate and the SO3 concentration, thereby avoiding the problems of incoordination and accuracy in adjusting the flow rates of the dilution water and the sodium carbonate solution separately in the prior art.

[0032] By respectively arranging electric regulating valves and flow meters on the alkali solution pipeline and the dilution water pipeline, the outlet of the dual-fluid spray gun is inserted into the SCR inlet flue, the electric regulating valve and the flow meter are connected with a control system such as a PLC control system, the injection amount of the alkaline absorbent is controlled by the electric regulating valve, and the real-time injection amount of the alkaline absorbent is grasped by the flow meter, so that the flow rate can be controlled accurately and timely to ensure that the atomized alkaline solution and the flue gas are fully mixed to achieve the effect of removing sulfur trioxide.

[0033] 5. The dilution water pump includes the dilution water pump A and the dilution water pump B which are arranged in parallel; the alkali liquid delivery pump includes the alkali liquid delivery pump A and the alkali liquid delivery pump B which are arranged in parallel. Two alkali liquid delivery pumps and two dilution water pumps are used as one for use and one for backup, so as to ensure the normal operation of the whole system even if one of the alkali liquid delivery pumps or the dilution water pump equipment fails.

[0034] 6. The powder bin discharge port is connected to the Roots blower outlet pipe through a feeding boot, and the Roots blower outlet pipe is connected to the dissolving tank feed port. Since the powder bin discharge port of the utility model is not directly connected to the dissolving tank feed port but is connected to the Roots blower outlet pipe through a feeding boot, and the Roots blower outlet pipe is indirectly connected to the dissolving tank feed port, the problems of the traditional powder bin moisture resorption and compaction and the leakage of dry powder discharge to pollute the surrounding environment are avoided.

[0035] 7. A connected weighing tank is provided at the lower part of the powder silo, which is connected to the feeding boot through a pipeline. A valve switch is provided on the pipeline. A vacuum pressure release valve and an inspection hole are provided at the upper part of the powder silo to facilitate accurate and timely weighing, improve work efficiency, ensure safe and reliable pressure in the sub-bin, and facilitate operator maintenance and inspection. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0037] Figure 1 It is a schematic diagram of the structure of an embodiment of the utility model;

[0038] In the figure, powder silo 1, Roots blower 2, dissolving tank 3, storage tank 4, dilution water tank 5, alkali solution transfer pump 6, alkali solution delivery pump 7, water supply pump 8, dilution water pump 9, metering and distribution module 10, adsorption dryer 11, compressed air storage tank 12, dual-fluid spray gun 13, SCR inlet flue 14, electric regulating valve 15, flow meter 16, vacuum pressure release valve 17, inspection hole 18, silo top dust collector 19, dissolving tank agitator 20, weighing tank 21, feeding shoe 22, valve switch 23, exhaust fan 24, desalted water 25, compressed air main pipe air 26. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0040] like Figure 1 As shown, a system for removing SO3 from flue gas by using alkali solution comprises a powder bin 1 for containing sodium carbonate dry powder, a dilution water tank 5, a sodium carbonate dissolving tank 3, a storage tank 4, an alkali solution transfer pump 6, an alkali solution delivery pump 7, a dilution water pump 9, a metering and distribution module 10, a spray gun 13, and a compressed air device; the powder bin 1 is provided with a dry powder feed port, which is connected to a tank truck through a pipeline, a vertebral discharge port at the bottom of the powder bin 1 is connected to an outlet pipe of a Roots blower 2 through a pipeline, and the outlet of the Roots blower 2 is connected to the sodium carbonate dry powder inlet of the dissolving tank 3 through a pipeline;

[0041] The liquid outlet of the dissolving tank 3 is connected to the liquid inlet of the alkali solution transfer pump 6 through a pipeline, and the liquid outlet of the alkali solution transfer pump 6 is connected to the liquid inlet of the storage tank 4 through a pipeline;

[0042] The liquid outlet of the storage tank 4 is connected to the liquid inlet of the alkali solution delivery pump 7 through a pipeline, and the liquid outlet of the alkali solution delivery pump 7 is connected to the alkali solution inlet of the alkali solution pipeline of the metering and dispensing module 10 through a pipeline;

[0043] The metering and dispensing module 10 includes an alkali solution pipeline and a dilution water pipeline. The desalted water 25 is connected to the inlet of the dilution water tank 5 through a pipeline, and the outlet of the dilution water tank 5 is connected to the inlets of the water supply pump 8 and the dilution water pump 9 through pipelines respectively; the outlet of the water supply pump 8 is connected to the inlet of the dissolution tank 3 through a pipeline, and the outlet of the dilution water pump 9 is connected to the dilution water inlet of the dilution water pipeline of the metering and dispensing module 10 through a pipeline;

[0044] The mixed solution at the liquid outlet of the metering and dispensing module 10 is connected to the liquid inlet of the dual-fluid spray gun 13 through a pipeline;

[0045] The spray gun 13 is connected to a compressed air device.

[0046] The compressed air device includes an adsorption dryer 11 and a compressed air storage tank 12. The compressed air main pipe gas 26 is connected to the air inlet of the adsorption dryer 11 through a gas pipeline. The air outlet of the adsorption dryer 11 is connected to the air inlet of the compressed air storage tank 12 through a pipeline. The air outlet of the compressed air storage tank 12 is connected to the air inlet of the dual-fluid spray gun 13 through a pipeline.

[0047] An electric regulating valve 15 and a flow meter 16 are respectively provided on the alkali solution pipeline and the dilution water pipeline, and the electric regulating valve 15 and the flow meter 16 are connected to the controller.

[0048] The dilution water pump 9 includes a dilution water pump A and a dilution water pump B which are arranged in parallel.

[0049] The alkali liquid delivery pump 7 includes an alkali liquid delivery pump A and an alkali liquid delivery pump B which are arranged in parallel.

[0050] The spray gun adopts a double-fluid spray gun 13.

[0051] The discharge port of the powder bin 1 is connected to the outlet pipe of the Roots blower 2 through a feeding boot, and the outlet pipe of the Roots blower is connected to the feed port of the dissolving tank 3. Since the discharge port of the powder bin 1 of the utility model is not directly connected to the feed port of the dissolving tank 3 but is connected to the outlet pipe of the Roots blower 2 through a feeding boot, and the outlet pipe of the Roots blower is indirectly connected to the feed port of the dissolving tank 3, the problems of moisture resorption and compaction of the traditional powder bin and leakage of dry powder discharge to pollute the surrounding environment are avoided.

[0052] A connected weighing tank 21 is provided at the lower part of the powder silo 1, and the weighing tank is connected to the feeding shoe 22 through a pipeline, and a valve switch 23 is provided on the pipeline. A vacuum pressure release valve 17, an inspection hole 18, and a silo top dust collector 19 are provided at the upper part of the powder silo 1.

[0053] The dissolving tank 3 is provided with a dissolving tank agitator 20 and an exhaust fan 24 .

[0054] The water supply pump 8 is also connected to the liquid inlet pipeline of the alkali solution transfer pump 6 and the liquid inlet pipeline of the alkali solution delivery pump 7 through corresponding pipelines.

[0055] Combination Figure 1 , water is injected into the dilution water tank 5 through the desalted water pipe connected to the liquid inlet of the dilution water tank 5, and the desalted water in the dilution water tank 5 is pumped into the dissolution tank 3 through the water supply pump 8. When the liquid level in the dissolution tank 3 reaches a certain height, the injection of desalted water is stopped; the powder bin 1 containing sodium carbonate dry powder is connected to the outlet pipe of the Roots blower 2 through the bottom discharge port, and the sodium carbonate dry powder in the powder bin 1 is pneumatically transported to the dissolution tank 3 through the Roots blower 2 for dissolution configuration; the configured solution alkali liquid transfer pump 6 is transported to the storage tank 4 through the pipeline for storage; Figure 1As shown, water is injected into the dilution water tank 5 through the desalted water pipe connected to the liquid inlet of the dilution water tank 5, and the desalted water in the dilution water tank 5 is pumped into the dissolution tank 3 through the water supply pump 8. After the liquid level in the dissolution tank 3 reaches a certain height, the injection of desalted water is stopped; the powder bin 1 containing sodium carbonate dry powder is connected to the outlet pipe of the Roots blower 2 through the bottom discharge port, and the sodium carbonate dry powder in the powder bin 1 is pneumatically transported to the dissolution tank 3 through the Roots blower 2 for dissolution configuration; the configured solution alkali liquid transfer pump 6 is transported to the storage tank 4 through the pipeline for storage;

[0056] The compressed air drawn from the compressed air main pipe in the factory area first enters the adsorption compressed air dryer 11 through a pipeline for drying, and then enters the compressed air storage tank 12 through a pipeline. The compressed air storage tank 12 provides compressed air to the dual-fluid spray gun 13 to atomize the sodium carbonate solution. The atomized sodium carbonate solution is directly sprayed into the flue before SCR through the spray gun to mix with the flue gas to remove SO3 in the flue gas.

[0057] The outlet of the dual-fluid spray gun 13 is inserted into the SCR inlet flue, and the atomized alkaline solution is fully mixed with the flue gas to achieve the effect of removing sulfur trioxide. The injection amount of the alkaline absorbent is controlled by the electric regulating valve 15, and the real-time injection amount of the alkaline absorbent is mastered by the flow meter 16.

[0058] The sodium carbonate dissolving tank and the storage tank of the utility model are separately arranged. Since the alkali solution delivery pump is in continuous operation, the preparation and storage of the sodium carbonate alkaline solution are separated by separately arranging the dissolving tank and the storage tank, thereby minimizing the influence on the continuous delivery of the sodium carbonate solution by the system and not affecting the continuous operation of the alkali solution delivery pump.

[0059] The flow rate regulation of the dilution water and the sodium carbonate solution of the utility model is concentrated in the metering and distribution module, and the flow rates of the dilution water and the sodium carbonate solution can be conveniently and uniformly regulated in the metering and distribution module according to the boiler load, the flue gas flow rate and the SO3 concentration, thereby avoiding the problems of incoordination and accuracy in regulating the flow rates of the dilution water and the sodium carbonate solution separately in the prior art.

[0060] The system of the utility model for removing SO3 from flue gas by using alkaline solution can effectively reduce the low-temperature corrosion and clogging problems of the subsequent air preheater, thereby reducing the operating cost.

[0061] In the description of the present invention, the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "vertical", "horizontal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the purpose of describing the present invention rather than requiring the present invention to be constructed or operated in a specific position, and therefore cannot be understood as a limitation on the present invention. The terms "connected" and "connected" in the present invention should be understood in a broad sense, for example, it can be a connection or a detachable connection; it can be a direct connection or an indirect connection through an intermediate component. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0062] The above is a preferred embodiment of the present invention, and the description of the specific embodiment is only used to better understand the concept of the present invention. For ordinary technicians in this technical field, several improvements or equivalent substitutions can be made according to the principle of the present invention, and these improvements or equivalent substitutions are also considered to fall within the protection scope of the present invention.

Claims

1. A system for removing SO3 from flue gas by using alkali solution, comprising an alkali solution delivery pump, a spray gun, and a compressed air device connected to each other, and also comprising a powder bin for containing sodium carbonate dry powder, a dilution water tank, a sodium carbonate dissolving tank, a storage tank, an alkali solution transfer pump, a dilution water pump, and a metering and dispensing module; the powder bin is provided with a dry powder feed port, the bottom of the powder bin is connected to an outlet pipe of a Roots blower, and the outlet of the Roots blower is connected to a sodium carbonate dry powder inlet of a dissolving tank through a pipe; the liquid outlet of the dissolving tank is connected to a liquid inlet of an alkali solution transfer pump through a pipe, and the liquid outlet of the alkali solution transfer pump is connected to a liquid inlet of a storage tank through a pipe; The metering and dispensing module comprises an alkali solution pipeline and a dilution water pipeline. The desalted water is connected to the inlet of the dilution water tank through a pipeline, and the outlet of the dilution water tank is respectively connected to the inlet of the water supply pump and the dilution water pump through pipelines; the outlet of the water supply pump is connected to the inlet of the dissolution tank through a pipeline, and the outlet of the dilution water pump is connected to the dilution water inlet of the dilution water pipeline of the metering and dispensing module through a pipeline; the outlet of the storage tank is connected to the inlet of the alkali solution delivery pump through a pipeline, and the outlet of the alkali solution delivery pump is connected to the alkali solution inlet of the alkali solution pipeline of the metering and dispensing module through a pipeline; the mixed solution at the outlet of the metering and dispensing module is connected to the inlet of the dual-fluid spray gun through a pipeline; The spray gun is connected to the compressed air device.

2. The system for removing SO3 from flue gas by using alkali solution according to claim 1, characterized in that: The compressed air device includes an adsorption dryer and a compressed air storage tank. The compressed air main pipe is connected to the air inlet of the adsorption dryer through a gas pipeline, the air outlet of the adsorption dryer is connected to the air inlet of the compressed air storage tank through a pipeline, and the air outlet of the compressed air storage tank is connected to the air inlet of the dual-fluid spray gun through a pipeline.

3. The system for removing SO3 from flue gas by using alkali solution according to claim 1, characterized in that: Electric regulating valves and flow meters are respectively provided on the alkali solution pipeline and the dilution water pipeline.

4. The system for removing SO3 from flue gas by using alkali solution according to claim 1, characterized in that: The dilution water pump comprises a dilution water pump A and a dilution water pump B which are arranged in parallel.

5. The system for removing SO3 from flue gas by using alkali solution according to claim 1, characterized in that: The alkali liquid delivery pump includes an alkali liquid delivery pump A and an alkali liquid delivery pump B which are arranged in parallel.

6. The system for removing SO3 from flue gas by using alkali solution according to claim 1, characterized in that: The spray gun adopts a double-fluid spray gun.

7. The system for removing SO3 from flue gas by using alkali solution according to claim 1, characterized in that: The powder bin discharge port is connected to the Roots blower outlet pipe through a feeding shoe, and the Roots blower outlet pipe is connected to the dissolving tank feed port.

8. The system for removing SO3 from flue gas by using alkali solution according to claim 7, characterized in that: A connected weighing tank is provided at the lower part of the powder bin, and the weighing tank is connected to the feeding boot through a pipeline, a valve switch is provided on the pipeline, and a vacuum pressure release valve and an inspection hole are provided at the upper part of the powder bin.

9. The system for removing SO3 from flue gas by using alkali solution according to claim 1, characterized in that: The dissolving tank is provided with a dissolving tank agitator.

10. The system for removing SO3 from flue gas by using alkali solution according to claim 1, characterized in that: The water supply pump is also connected to the liquid inlet pipeline of the alkali solution transfer pump and the liquid inlet pipeline of the alkali solution delivery pump through corresponding pipelines.

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