WO2018028425A1 - Desulphurization wastewater zero-discharge system for removing fluorine and chlorine from coal-fired flue gas by semi-dry process - Google Patents

Abstract

A desulphurization wastewater zero-discharge system for removing fluorine and chlorine from a coal-fired flue gas by a semi-dry process, comprising a high-concentration alkali solution pipeline (1), a desulphurization wastewater pipeline (2), an alkali solution dilution pipeline (3), an alkali solution atomization device (4), a compressed air pipeline (5), a process water pipeline (6) and a flue (7), wherein the high-concentration alkali solution pipeline (1) comprises a storage tank (1-1), a regulating valve (1-2) and a flow meter (1-3); the desulphurization wastewater pipeline (2) comprises a clarification tank (2-1), a regulating valve (2-2) and a flow meter (2-3); the alkali solution atomization device (4) is arranged in the flue (7) between an air pre-heater (7-1) and a dust remover (7-2); the process water pipeline (6) is connected near an inlet of the desulphurization wastewater pipeline (2); and devices in the flue (7) comprise the air pre-heater (7-1), the dust remover (7-2) and a desulphurization system (7-3).

Description

Zero-emission system of desulfurization wastewater for removing fluorine and chlorine from coal-fired flue gas by semi-dry method Technical field

The invention belongs to the technical field of energy saving and emission reduction, and relates to a zero discharge system of desulfurization wastewater for removing fluorine and chlorine by a semi-dry method of burning coal gas.

Background technique

Coal contains elements such as sulfur, chlorine and fluorine. When coal is burned, these elements form SO ₂ , HCl, HF, SO ₃ and other gases. Among them, HCl, HF and SO ₃ are trace gases, but they are highly corrosive gases. It adversely affects the low temperature flue and equipment at the tail of the boiler. HCl and HF gases can be completely removed in the wet desulfurization system, so Cl ^- and F ^- will be enriched in the desulfurization slurry. Excessive concentrations of Cl ^- and F ^- will reduce the desulfurization efficiency and even poison the desulfurization slurry. At present, the desulfurization system mainly controls the Cl ^- concentration in the desulfurization slurry by discharging the desulfurization wastewater.

The desulfurization wastewater is not only rich in Cl ^- and F ^- , but also rich in various salts. Therefore, the desulfurization wastewater is a kind of pollutant, so the desulfurization wastewater needs to be treated by wastewater to be discharged into the environment. With the awareness of environmental protection and the increase of requirements, zero discharge of desulfurization wastewater is gradually put on the agenda. Most of the pollutants in desulfurization wastewater can be removed by conventional lower cost methods, but Cl ^- is difficult to form because it is difficult to form precipitates. Simple removal, the currently more effective technology is to use the evaporation method, but its energy consumption is large, so there is a problem of excessive operating costs. The conventional zero discharge of wastewater is equivalent to zero pollutant water discharge. At present, attempts have been made to re-spray the desulfurization wastewater into the higher temperature flue to achieve zero flow discharge of the desulfurization wastewater. The method is simple to implement, but there is smoke due to the large amount of water spray. The problem of large temperature drop and serious contamination of the flue is difficult to implement effectively.

Summary of the invention

In order to solve the problem of zero discharge of desulfurization wastewater involved in the background art, the present invention provides a zero-emission system for desulfurization wastewater of a semi-dry method for removing flue gas from coal-fired flue gas, which is sprayed before the coal-fired flue gas enters the precipitator. Into the base solution, the HCl, HF, SO ₃ and other gases in the flue gas are converted into solid salts and removed with the fly ash, which greatly reduces the HCl, HF, SO ₃ and other gases entering the desulfurization tower, thereby greatly reducing The amount of desulfurization waste water, a small amount of desulfurization waste water discharged as a base substance solvent, thereby effectively achieving zero flow discharge of the desulfurization waste water.

The concentration of HCl, HF, and SO ₃ gas contained in coal-fired flue gas is generally about several tens of μL/L, and the flue gas also contains SO ₂ gas of several hundred to several thousand μL/L. Semi-dry method The removal of chlorofluorocarbon technology has a competitive relationship between high concentration of SO ₂ and low concentration target removal, which has a certain influence on the technical feasibility of the present invention. Therefore, before submitting the application of the present invention, the applicant has carried out a mechanistic study, respectively, through chemical reaction dynamics simulation research (using CHEMKIN software) and experimental bench simulation experiments, and obtained the gas reaction of the actual concentration of NaOH and flue gas. The basic rule: when the molar ratio of Na ⁺ and Cl ^{- is} 5, the removal rate of HCl can reach more than 70%, and when the molar ratio of Na ⁺ and Cl ^- reaches 10, the removal rate of HCl can be close to 100%, and the chemical reaction can be 0.1. Fully completed within s. The results obtained by the two research methods are basically the same, indicating that the invention is technically feasible. When the HCl removal rate reaches 70%, the desulfurization wastewater flow rate is reduced to 30%. At this time, the desulfurization wastewater is injected into the flue as a base solvent, which has little effect on the flue temperature. The system of the invention is simple and the investment is small, and the consumption cost of NaOH is much lower than the operating cost of the zero-emission technology of other desulfurization wastewater.

The technical solution adopted by the present invention to solve the technical problem thereof:

The invention comprises a high concentration alkali liquid pipeline, a desulfurization waste water pipeline, a diluted alkali liquid pipeline, an alkali liquid atomization device, a compressed air pipeline, a process water pipeline, and a flue.

The high-concentration alkali liquid pipeline is used for conveying high-concentration alkali liquor, including a high-concentration alkali liquor storage tank, a high-concentration alkali liquid regulating valve, and a high-concentration alkali liquid flowmeter. The high concentration lye is a saturated or nearly saturated NaOH solution, and may also be other base solutions. After the high-concentration lye is configured, it is stored in a high-concentration lye storage tank. According to the unit load (flue gas volume) and the HCl gas concentration in the flue gas, the high-concentration lye regulating valve is used to control the high-concentration lye flow, and the high-concentration lye The flow rate is measured by a high concentration lye flow meter. Using NaOH as a base, the molar ratio of Na ⁺ and Cl ^- ions is controlled to be 1 to 15.

The desulfurization waste water pipeline is used for conveying desulfurization wastewater, including a desulfurization wastewater clarification tank, a desulfurization wastewater regulating valve, and a desulfurization wastewater flowmeter. The desulfurization wastewater of the desulfurization system is previously subjected to a desulfurization wastewater clarification tank to remove most of the sedimentable matter, and the desulfurization wastewater clarification tank is also used to buffer the flow of the desulfurization wastewater from the desulfurization system. The flow rate of desulfurization wastewater is generally equal to the discharge amount of desulfurization system wastewater, and the self-equilibrium of desulfurization wastewater is realized. In special cases, process water can be used as a necessary supplement or replacement.

The diluted lye line comprises a lye dilution mixer and a high pressure pump. The desulfurized wastewater from the high-concentration lye and the desulfurization waste water pipeline of the high-concentration lye pipeline is uniformly mixed and diluted in the lye dilution mixer, and the diluted lye is sent to the lye atomization device through the high-pressure pump.

The alkali liquid atomizing device is arranged in a flue between the air preheater and the dust remover, atomizes the diluted alkali liquid from the diluted alkali liquid pipeline into a mist droplet, and fully and uniformly mixes with the flue gas, and atomizes The lye can be Reacts with acid gases in the flue gas. The lye atomization device uses pneumatic atomization to accommodate a wide range of load regulation. The lye atomization device adopts a multi-nozzle grid arrangement, so that the atomized lye can be uniformly covered in the entire flue section to meet the requirement of sufficiently uniform mixing of the atomized lye and the flue gas.

The compressed air pipeline is used to provide compressed air required for the alkali liquid atomization device, and serves as a shielding gas when the system is shut down to prevent nozzle clogging of the alkali liquid atomization device. Compressed air comes from the existing compressed air mains of the coal-fired unit.

The process water pipeline is connected to the inlet of the desulfurization waste water pipeline, and is used for cleaning the system pipeline when the system is shut down to prevent pipeline clogging and corrosion. In special cases, the desulfurization wastewater can be supplemented or replaced to ensure stable operation of the system. The process water comes from the existing process jellyfish tube of the coal-fired unit.

The flue is the existing tail flue of the coal burning unit, and the equipment in the flue includes the existing air preheater, dust collector and desulfurization system of the coal burning unit.

The high-concentration lye of the invention controls the flow rate according to the unit load and the HCl concentration in the flue gas, and is mixed with the desulfurization waste water to form a diluted alkali liquid, and then sprayed into the air pre-discharge device and the dust remover through the multi-nozzle grid-arranged alkali liquid atomization device. In the flue between the flue gas, the flue gas is fully and uniformly mixed, and most of the gas such as HCl, HF, SO ₃ in the flue gas is solidified into the fly ash, and the discharge amount of the desulfurization waste water is greatly reduced, and the desulfurization waste water is sprayed as a base solvent. Into the flue, the zero flow discharge of the desulfurization wastewater is realized.

The beneficial effects of the invention are:

A small amount of base solution is sprayed into the flue gas before the precipitator, and the HCl, HF, and SO ₃ in the flue gas are solidified into the fly ash, which greatly reduces the flow rate of the desulfurization waste water, and the desulfurization waste water is used as a solvent for the base substance. The desulfurization wastewater is circulated in the flue, thereby achieving zero-flow discharge of the desulfurization wastewater. The invention has little influence on the temperature of the flue gas, has little influence on the safe and economic operation of the tail flue and the equipment, and at the same time, the gas such as HCl, HF, SO ₃ in the flue gas is removed, and the low temperature flue of the tail is effectively reduced. The tendency of equipment to ash and corrosion, and improve the efficiency of desulfurization. The invention has the remarkable advantages of simple system, small investment and low operating cost.

DRAWINGS

Figure 1 is a schematic diagram of the system.

In the figure, 1, high-concentration lye pipeline; 1-1, high-concentration lye storage tank; 1-2, high-concentration lye regulating valve; 1-3, high-concentration lye flowmeter; 2. desulfurization wastewater pipeline Road; 2-1, desulfurization wastewater clarification tank; 2-2, desulfurization wastewater regulating valve; 2-3, desulfurization wastewater flowmeter; 3, diluted alkali liquor pipeline; 3-1, lye dilution mixer; 3-2 , high pressure pump; 4, alkali liquid atomization device; 5, compressed air pipeline; 5-1, compressed air mother Pipe; 6, process water pipeline; 6-1, process jellyfish pipe; 7, flue; 7-1, air preheater; 7-2, dust collector; 7-3, desulfurization system.

detailed description

The invention is further described below in conjunction with the drawings.

As shown in Figure 1, a zero-emission system for desulfurization of desulfurization wastewater containing semi-dry flue gas from coal-fired flue gas, including high-concentration lye pipeline 1, desulfurization wastewater pipeline 2, diluted lye pipeline 3, lye The atomizing device 4, the compressed air line 5, the process water line 6 and the flue 7.

The high-concentration lye line 1 includes a high-concentration lye storage tank 1-1, a high-concentration lye regulating valve 1-2, and a high-concentration lye flow meter 1-3.

The desulfurization waste water pipeline 2 includes a desulfurization wastewater clarification tank 2-1, a desulfurization wastewater regulating valve 2-2, and a desulfurization wastewater flow meter 2-3.

The diluted lye line 3 includes an lye dilution mixer 3-1 and a high pressure pump 3-2.

The compressed air line 5, the compressed air is from the existing compressed air mother tube 5-1 of the coal burning unit.

The process water line 6 and the process water are derived from the existing process water mother pipe 6-1 of the coal-fired unit.

The flue 7 is the existing tail flue of the coal burning unit, and the equipment in the flue includes the existing air preheater 7-1, the precipitator 7-2 and the desulfurization system 7-3 of the coal burning unit.

The high-concentration lye line 1 is used for transporting a high-concentration lye, and the high-concentration lye is a saturated or nearly saturated NaOH solution, and may also be other base solutions. After the high-concentration lye is configured, it is stored in the high-concentration lye storage tank 1-1. According to the unit load (flue gas volume) and the HCl gas concentration in the flue gas, the high-concentration lye is controlled by the high-concentration lye regulating valve 1-2. Flow rate, high concentration lye flow rate is measured by high concentration lye flow meter 1-3. Using NaOH as a base, the molar ratio of Na ⁺ and Cl ^- ions is controlled to be 1 to 15.

The desulfurization waste water line 2 is used for conveying desulfurization waste water, and the desulfurization waste water of the desulfurization system is previously removed by the desulfurization waste water clarification tank 2-1 to remove most of the sedimentable matter, and the desulfurization waste water clarification tank 2-1 is also used for buffering desulfurization. System 7-3 desulfurization wastewater flow. The flow rate of desulfurization wastewater is generally equal to the discharge amount of desulfurization system wastewater, and the self-equilibrium of desulfurization wastewater is realized. In special cases, process water can be used as a necessary supplement or replacement.

The diluted lye line 3, the high-concentration lye from the high-concentration lye line 1 and the desulfurization waste water of the desulfurization waste water line 2 are uniformly mixed and diluted in the lye dilution mixer 3-1, and diluted. The latter lye is sent to the lye atomizing device 4 through the high pressure pump 3-2.

The alkali liquid atomizing device 4 is disposed in the flue 7 between the air preheater 7-1 and the dust remover 7-2, and atomizes the diluted alkali liquid from the diluted alkali liquid line 3 into a mist. And fully mixed with the flue gas, the atomized alkali solution can react with the acid gas in the flue gas. The lye atomizing device 4 uses pneumatic atomization to accommodate a wide range of load regulation. The lye atomization device 4 adopts a multi-nozzle grid arrangement, so that the atomized lye can be uniformly covered in the entire flue section to meet the requirement of sufficiently uniform mixing of the atomized lye and the flue gas.

The compressed air line 5 is used to supply compressed air required for the lye atomizing device 4, and serves as a shielding gas when the system is shut down to prevent clogging of the nozzle of the lye atomizing device 4.

The process water pipeline 6 is connected to the vicinity of the inlet of the desulfurization waste water pipeline 2, and is used for cleaning the system pipeline when the system is shut down to prevent pipeline clogging and corrosion. In special cases, the desulfurization wastewater can be supplemented or replaced to ensure stable operation of the system.

Claims (7)

1. A zero-emission system for desulfurization wastewater for removing fluorine and chlorine by semi-dry method for burning coal-fired flue gas, characterized by comprising high-concentration alkali liquid pipeline, desulfurization waste water pipeline, diluted alkali liquid pipeline, alkali liquid atomization device, compressed air Pipeline, process water pipe, flue;

   The high-concentration alkali liquid pipeline is used for conveying high-concentration alkali liquid, including high-concentration alkali liquid storage tank, high-concentration alkali liquid regulating valve, high-concentration alkali liquid flow meter; high-concentration alkali liquid is arranged and stored in high The concentration of the alkali liquid storage tank controls the high-concentration alkali liquid flow rate through the high-concentration alkali liquid regulating valve, and the high-concentration alkali liquid flow rate is measured by the high-concentration alkali liquid flow meter;

   The desulfurization waste water pipeline is used for conveying desulfurization waste water, including a desulfurization waste water clarification tank, a desulfurization waste water regulating valve, a desulfurization waste water flow meter; the desulfurization waste water is previously subjected to a desulfurization waste water clarification tank to remove most of the sedimentable matter, and the desulfurization waste water clarification tank is also Used to buffer the flow of desulfurization wastewater;

   The alkali liquid atomizing device is arranged in a flue between the air preheater and the dust remover, atomizes the diluted alkali liquid from the diluted alkali liquid pipeline into a mist droplet, and fully and uniformly mixes with the flue gas, and atomizes The lye can react with the acid gas in the flue gas;

   The compressed air pipeline is used for providing compressed air required for the alkali liquid atomization device, and serves as a shielding gas when the system is shut down, preventing the nozzle of the alkali liquid atomization device from being blocked;

   The process water pipeline is connected to the inlet of the desulfurization waste water pipeline, and is used for cleaning the system pipeline when the system is shut down to prevent pipeline clogging and corrosion;

   The flue is the existing tail flue of the coal burning unit, and the equipment in the flue includes the existing air preheater, dust collector and desulfurization system of the coal burning unit.
2. A zero-emission system for desulfurization wastewater for removing fluorine chlorine by a semi-dry method for burning coal-fired flue gas according to claim 1, wherein said high-concentration alkali solution is a saturated or nearly saturated base solution.
3. The zero-emission system for desulfurization waste water for removing fluorine chlorine by a semi-dry method for burning coal-fired flue gas according to claim 2, wherein the high-concentration alkali solution is a NaOH solution.
4. A zero-emission system for desulfurization wastewater for removing fluorine chlorine by a semi-dry method for burning coal-fired flue gas according to claim 3, characterized in that NaOH is used as a base, and the molar ratio of Na ⁺ and Cl ^- ions is controlled to be 1 to 15.
5. A zero-emission system for desulfurization wastewater for removing fluorine chlorine from a coal-fired flue gas semi-dry method according to claim 1, wherein the alkali liquid atomization device adopts pneumatic atomization to adapt to a wide range of load regulation; The lye atomization device adopts a multi-nozzle grid arrangement, so that the atomized lye can be uniformly covered in the entire flue section to meet the requirement of sufficiently uniform mixing of the atomized lye and the flue gas.
6. A zero-emission system for desulfurization wastewater for removing fluorine chlorine by a semi-dry method for burning coal-fired flue gas according to claim 1, wherein the compressed air is derived from a compressed air mother pipe existing in the coal-fired unit.
7. A zero-emission system for desulfurization wastewater for removing fluorine chlorine by a semi-dry method for burning coal-fired flue gas according to claim 1, wherein the process water is derived from a process water master pipe existing in a coal-fired unit.

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