CN1544129A

CN1544129A - Electron beam deep oxidation flue gas cleaning method

Info

Publication number: CN1544129A
Application number: CNA2003101155228A
Authority: CN
Inventors: 罗经宇
Original assignee: BEIJING ENERGY ENVIRONMENT AND ECONOMY TECHNOLOGY Ltd
Current assignee: BEIJING ENERGY ENVIRONMENT AND ECONOMY TECHNOLOGY Ltd
Priority date: 2003-11-28
Filing date: 2003-11-28
Publication date: 2004-11-10
Anticipated expiration: 2023-11-28
Also published as: CN1221306C

Abstract

The invention relates to an electron-beam deep-oxidization fume-purifying method. It includes: temperature lowering and dust cleaning of high-temperature fume; absorbing SO2 in the fume by absorption liquid and discharging the purified fume into the atmosphere; adjusting pH value by ammonia gas to make the absorption liquid form ammonium sulfite solution; taking out and sending the ammonium sulfite solution into irradiation chamber, and using the electron beam to oxidize the ammonium sulfite, to obtain ammonium sulphate. It can obtain very high desulfurizing efficiency and by-products mainly as the positive salt, and has advantages of low energy consumption, high desulfurizing efficiency and being able to adapt to the change of fume quality and quantity.

Description

Electron beam deep oxidation flue gas purification method

The invention belongs to the technical field of boiler tail gas treatment. In particular to a method for removing sulfur dioxide in flue gas

Background artas economy develops, industrialized societies demand more energy. In the ever-increasing demand for energy, energy relies primarily on fossil fuels: coal and oil. However, burning fossil fuels produces a large amount of harmful gases and pollutants that can contaminate the earth's environment. In order to prevent the diffusion of pollutants and stop destroying the earth's environment, a number of flue gas cleaning methods and devices have been developed. The electron beam method is a new desulfurization and denitrification process, waste water and waste residue are not generated in the method, byproducts can be used as chemical fertilizers, secondary pollution is not generated, and Volatile Organic Compounds (VOC) in smoke are removed at the same time. The technological process includes dedusting fume from coal burning boiler, cooling in cooling tower at temperature below 70 deg.c with cooling water spray, injecting ammonia gas before the fume enters the reactor, and high energy electron irradiationBeam irradiation, N in flue gas₂、O₂Performing radiation reaction with water vapor to generate a large amount of ions, free radicals, electrons and various excited atoms, molecules and other active substances, which are used for removing SO in the flue gas₂And NO_xOxidation to SO₃And NO₂. These high-priced sulfur oxides and nitrogen oxides react with water vapor to generate sulfuric acid and nitric acid in the form of mist, and these acids react with ammonia that has previously entered the reactor to generate ammonium sulfate and ammonium nitrate. And finally, collecting ammonium sulfate and ammonium nitrate in the form of aerosol by using an electrostatic precipitator, discharging the purified flue gas through a chimney, and granulating the byproduct to obtain the fertilizer. The patent documents relating to the above-mentioned electron beam desulfurization method are as follows:

CN88103260A relates to a method and apparatus for treating exhaust gas containing harmful components of sulfur oxides and/or nitrogen oxides, the method comprising: the exhaust gas is irradiated with ionizing radiation or ultraviolet rays in the presence of ammonia to generate solid particles, and the exhaust gas is first treated with an electric precipitator and then further treated with a mechanical filter. The invention relates to an apparatus comprising an electric precipitator followed by a mechanical filter for treating solid particles produced in the process.

CN1035060A discloses a method for purifying exhaust gas containing sulfur oxides and/or nitrogen oxides. The method comprises the following steps: the waste gas is introduced into the irradiation zone, and the by-products (ammonium sulfate and/or ammonium nitrate) are collected by means of a dust collector before, during or after irradiation, and the purified waste gas is evacuated. The amount of ammonia added is less than the amount calculated from the target desulfurization and denitrification efficiencies so as to reduce the escape of ammonia gas. Alkaline materials, excluding ammonia, are added to the exhaust gas to adjust the pH of the by-product to 6 or greater than 6 to suppress the side effects of the aminosulfonic acid impurity.

CN1225035A discloses a method and apparatus for treating gas by electron beam irradiation. The method comprises the following process flows: the high-temperature flue gas from the boiler is firstly cooled by a heat exchanger, then water is sprayed to the high-temperature flue gas in a cooling tower, the flue gas is cooled and humidified, the flue gas mixed with ammonia, water and air is irradiated by electron beams in an irradiation chamber, sulfur oxides and/or nitrogen oxides in the flue gas undergo complex chemical reaction with the ammonia, the water and the oxygen under the irradiation of the electron beams to generate ammonium sulfate and/or ammonium nitrate, a dust collector is used at an outlet of a system to collect generated reactants, and the purified flue gas can be directly discharged.

CN1332029A relates to a flue gas purification method of a semidry method. The method comprises the following process flows: after high-temperature flue gas from a factory is dedusted, spraying is carried out through a spray drying device, cooling and humidifying are carried out, large-particle by-products with particle size of more than 100 micrometers are collected, the remaining small particles with particle size of less than 100 micrometers are collected in a dust collector, heated ammonia gas and flue gas are mixed and then enter an irradiation chamber, reaction is carried out under the irradiation of electron beams generated by a linear pulse accelerator, and ammonium sulfate and/or ammonium nitrate is/are sprayed and dissolved by solution in a wet electrostatic precipitator.

The method has the defects that the object of electron beam irradiation is flue gas, the size is large, the consumed electron beam power is large, the equipment investment, the operation cost and the maintenance cost are high, and the economy of flue gas purification is influenced.

The invention aims to overcome the defects of the prior art and provide an electron beam deep oxidation flue gas purification method which can obtain high desulfurization efficiency by paying out very little energy and can obtain byproducts mainly containing normal salt, and has the advantages of low energy consumption, high desulfurization rate, adaptability to flue gas quality and quantity change and the like.

The invention provides an electron beam deep oxidation flue gas purification method which is characterized by comprising the following steps:

1) cooling and dedusting the high-temperature flue gas from the outlet of the boiler (the step can be realized by various conventional technical means);

2) absorbing sulfur dioxide in the cooled and dedusted flue gas by using an absorption liquid, and discharging the purified flue gas from which the sulfur dioxide is removed into the atmosphere, wherein the absorption liquid mainly comprises the following components in mass concentration: 25-35% of ammonium sulfite, 5-10% of ammonium bisulfite, 0-5% of ammonium sulfate and the balance of water; the pH value of the absorption liquid is between 6.0 and 8.5;

3) when the PH value of the absorption liquid is reduced to 3.8-5.0, ammonia is used for adjusting the PH value of the solution, so that the PH value is kept between 6.0-8.5, and the sulfur dioxide in the absorption liquid is enabled to continuously form an ammonium sulfite solution (steps 2 and 3 can be realized by adopting various absorption towers and equipment with corresponding functions);

4) extracting a part of the ammonium sulfite solution, conveying the part of the ammonium sulfite solution into an irradiation chamber, oxidizing ammonium sulfite in the solution by using an electron beam to obtain an ammonium sulfate solution, wherein the solution can be directly used for agriculture or a crystallization and granulation device is used for obtaining a solid fertilizer with the main component of ammonium sulfate so as to realize flue gas purification and obtain the fertilizer, oxygen-containing gas is injected into the irradiation chamber, the mass ratio of the gas to the liquid is (3-60) to 100, the volume oxygen content of the gas is 21-100%, and the pressure of the gas in the irradiation chamber is 10-100 Pa lower than the atmospheric pressure; adding the rest part of ammonium sulfite solution into the process water to reduce the concentration of the solution to 10-40 percent, and transferring the solution as new absorption solution to the steps 2), 3) and 4) for circulation.

The above process is a continuous cycle of steps and the initial absorption solution can be produced directly from the untreated flue gas mixed with ammonia and water or obtained by other conventional methods.

The amount of the ammonium sulfite solution conveyed into the irradiation chamber in the method is calculated according to the amount of flue gas treated in actual operationof the method, the content of sulfur dioxide in the flue gas and the desulfurization rate, and the specific methods are common general knowledge in the field.

The invention has the characteristics and effects that:

the invention firstly absorbs sulfur dioxide in flue gas, and then uses electron beam irradiation to process the absorption product to obtain the fertilizer taking ammonium sulfate as the main component.

The method can pay out very little energy, obtain very high desulfurization efficiency, can obtain byproducts mainly containing normal salt, and has the advantages of low energy consumption, high desulfurization rate, adaptability to flue gas quality and quantity change and the like.

The embodiment of the method for purifying the flue gas by the electron beam deep oxidation provided by the invention specifically comprises the following steps of:

1) high-temperature flue gas (120 ℃ C., 200 ℃ C., 1X 10 ℃ C.) from an outlet of a boiler (with a granite water film dust remover)³-3×10⁶Standard cubic meter/hour, wherein the content of sulfur dioxide is 100-. The cooled flue gas enters a granite water film dust remover to remove most of smoke dust and a small amount of sulfur dioxide in the flue gas (the temperature of the flue gas at the outlet of the water film dust remover is 50-70 ℃, the content of sulfur dioxide is 80-4500ppm, and the content of smoke dust is 80-200 mg/standard cubic meter).

2) The flue gas after dust removal enters the tower from the bottom of the plate-type absorption tower, flows upwards in the tower, sequentially passes through the spraying section and the tower plate, and is contacted with absorption liquid, so that the temperature of the flue gas is reduced, the moisture content is increased, and meanwhile, sulfur dioxide in the flue gas enters the absorption liquid through mass transfer, so that the sulfur dioxide in the flue gas reaches the emission standard, and the purification of the flue gas is realized; the purified flue gas continuously runs upwards in the tower, and is discharged out of the absorption tower after entrained liquid is removed by the demister. The temperature of the flue gas discharged from the absorption tower is 40-50 ℃, the sulfur dioxide content is less than 50ppm, and the smoke dust content is less than 50 mg/standard cubic meter. The temperature of the flue gas is raised to more than 80 ℃ after the flue gas is discharged from the tower through a temperature raising heat exchanger, and the heat of the temperature raising heat exchanger comes from the aforementioned temperature lowering heat exchanger. And finally, discharging the flue gas into the atmosphere through a fan and a chimney. For a power plant adopting the electrostatic dust collector, the flue gas from the boiler is firstly introduced into the electrostatic dust collector, then enters the cooling heat exchanger, the temperature of the flue gas is reduced to 50-70 ℃ by the cooling heat exchanger, and then enters the absorption tower, and the later process is the same as the process.

The absorption liquid mainly comprises ammonium sulfite, ammonium bisulfite and ammonium sulfate, and the mass concentration of each component is as follows: ammonium sulfite is 25-35% (30% in the embodiment), ammonium bisulfite is 5-10% (6% in the embodiment), ammonium sulfate is 0-5% (2% in the embodiment), and the balance is water; the PH value is between 6.0 and 8.5, and the sulfur dioxide absorbent has extremely strong capability of absorbing sulfur dioxide. The absorption liquid absorbs sulfur dioxide in the flue gas and then settles at the bottom of the tower, and ammonium sulfite in the absorption liquid is converted into ammonium bisulfite.

3) When the pH value is lowered to 3.8-5.0 and the capacity for absorbing sulfur dioxide is reduced, ammonia gas (12 kg/hr ammonia gas per hour in this example) is added to the solution to adjust the pH value of the solution to a neutral or slightly alkaline pH value of 6.0-8.5 (pH value is adjusted to 8 or more in this example), a part of the solution is then drawn off and fed to a solution tank before the oxidation apparatus (feeding amount is 152 kg/hr), and the remaining part of the solution is fed to another solution tank and process water is added to reduce the concentration to 10-40% as a new absorbing solution (concentration is maintained at 25% in this example). The main chemical reactions of the absorption process are:

4) the high-concentration ammonium sulfite solution led out from the absorption tower is conveyed to a nozzle in the irradiation chamber by a pump and is sprayed out from the nozzle to form fog drops with the grain diameter of 20-200 microns. The nozzle may be a two-phase nozzle or a single-phase nozzle. Spraying oxygen-containing gas into the irradiation chamber while spraying liquid droplets from a two-phase nozzle, wherein the mass ratio of the gas to the liquid is (3-60) to 100 (30/100 in the embodiment), and the volume oxygen content of the gas is 21-100% (21% in the embodiment); only liquid is sprayed into the irradiation chamber by using a single-phase nozzle, and an oxygen-containing gas is injected into the irradiation chamber by using an additional gas introducing device, wherein the mass ratio of the gas to the liquid in the irradiation chamber is also (3-60) to 100, the volume oxygen content of the gas is 21-100%, and the pressure of the gas in the irradiation chamber is 10Pa-100Pa lower than the atmospheric pressure. The liquid fog drops in the irradiation chamber and the oxygen-containing gas move at the speed of 0.5-100m/s after being mixed, pass through the area irradiated by the high-energy electrons and are irradiated by the electrons. The direction of movement of the liquid droplets and the oxygen-containing gas may be horizontal, or may be downward or upward. The high-energy electron irradiation area can be one, can be a plurality of high-energy electron irradiation areas which are arranged in parallel, can be two opposite high-energy electron irradiation areas, can be a plurality of groups of high-energy electron irradiation areas which are opposite to each other, and can also be a combination of the modes. The method for generating the high-energy electron irradiation area has various methods, in the embodiment, a high-energy electron accelerator can be used for emitting electrons with the energy of 0.3-100Mev, the beam intensity of the electrons is 0.1-300mA, and the electrons enter the irradiation chamber after passing through a titanium window to form an irradiation field inside the irradiation chamber. The liquid fog drops and the gas continue to move after being irradiated, the gas and the liquid are separated at one end of the irradiation chamber, the gas is discharged into the atmosphere, and the liquid is collected in the solution tank. The liquid may be irradiated one or more times; after a certain number of irradiations, the main components in the liquid are converted from ammonium sulfite into ammonium sulfate. Then the solution with ammonium sulfate as main component is discharged from irradiation device, or directly used in agriculture, or concentrated and crystallized to be used as fertilizer.

In this embodiment, two electron accelerators can be used, which emit electrons with an energy of 0.45Mev, and the beam intensity of the electrons emitted by each accelerator is 40mA, and after the electrons enter the irradiation chamber, an irradiation field is formed inside the irradiation chamber. The absorbed dose of the solution was 80 kGy. The solution fog drops and the air continue to move after being irradiated, the air and the solution are separated at one end of the irradiation chamber, the air is discharged into the atmosphere, and the solution is collected in the solution tank. After the solution is irradiated once, the main components are converted into ammonium sulfate from ammonium sulfite, and the ammonium sulfate is discharged from an irradiation chamber and used as a fertilizer after being concentrated and crystallized.

Claims

1. An electron beam deep oxidation flue gas purification method is characterized by comprising the following steps:

1) cooling and dedusting the high-temperature flue gas from the outlet of the boiler;

2) the absorption liquid absorbs sulfur dioxide in the cooled and dedusted flue gas, and discharges the purified flue gas from which the sulfur dioxide is removed into the atmosphere, the absorption liquid mainly comprises ammonium sulfite, ammonium bisulfite and ammonium sulfate, and the mass concentration of each component is as follows: 25-35% of ammonium sulfite, 5-10% of ammonium bisulfite, 0-5% of ammonium sulfate and the balance of water; the pH value of the absorption liquid is between 6.0 and 8.5;

3) when the PH value of the absorption liquid is reduced to 3.8-5.0, adjusting the PH value of the solution by ammonia gas to keep the PH value between 6.0-8.5, and continuously forming ammonium sulfite solution by sulfur dioxide in the absorption liquid;

4) the method comprises the steps of conveying the ammonium sulfite solution into an irradiation chamber, oxidizing the ammonium sulfite in the solution by using an electron beam to obtain an ammonium sulfate solution, wherein the solution can be directly used for agriculture or a crystallization granulation device is used for obtaining a solid fertilizer with the main component of ammonium sulfate, so that flue gas purification is realized and the fertilizer is obtained, oxygen-containing gas is injected into the irradiation chamber, the mass ratio of the gas to liquid is (3-60) to 100, the volume oxygen content of the gas is 21-100%, and the pressure of the gas in the irradiation chamber is 10-100 Pa lower than the atmospheric pressure.

2. The electron beam deep oxidation flue gas purification method according to claim 1, wherein only a part of the ammonium sulfite solution extracted in step 4) is sent to the irradiation chamber, and the other part of the solution is added with process water to reduce the concentration of the solution to 10-40%, and the solution is recycled as a new absorption solution to carry out steps 2), 3) and 4).