Abstract: The current situation of our country thermal power plant desulfurization technology, introduces the development of coal-fired flue gas desulphurization technology Several thermal power plants and their respective characteristics and selection process are summarized desulfurization technology, the development prospects were discussed.

1 Introduction

With the rapid development of society and economy, the issue of environmental pollution has become increasingly prominent, seriously endangering people's physical and mental health and affecting the sustainable development of society, and has gradually become a major social issue that threatens the survival and development. At present, China's air pollution is more serious, the main pollutants are sulfur dioxide and soot, sulfur dioxide emissions from about 60 to 70%, most of which come from coal-fired power plant process. Therefore, the development of low-cost, high-efficiency desulfurization technology has become the top priority of power generation companies. In recent years, China has grasped the flue gas desulfurization work and made significant progress. Various types of flue gas desulfurization technologies have been introduced from abroad and put into operation.

2 China's existing desulfurization technology

2.1 limestone gypsum wet desulfurization technology

The basic principle is that the flue gas first enters the electrostatic precipitator to remove the dust and then enters the heat exchanger to cool down and finally enters the absorption tower. During upward flow, SO2 chemically reacts with the absorbent to generate CaSO3. Clean flue gas emissions after heating in the heat exchanger, CaSO3 reacts with oxygen to generate gypsum.

The technology has the advantages of large flue gas treatment, high desulfurization efficiency, wide range of raw materials needed for desulfurization, low price, good adaptability of coal and good performance of the desulfurization device. In addition, the desulfurization product (gypsum) As a raw material for cement production, it has broad application prospects. At the same time, there are also problems such as easy plugging, fouling, corrosion of calcium sulfate and mechanical breakdown, etc., and the energy consumption is relatively large, wastewater needs to be disposed of, and the investment and operation cost are high.

2.2. Spray drying desulfurization technology

Spray drying method is the basic principle of lime slurry for desulfurization agent, the lime slurry aqueous solution is injected into the absorber with a nebulizer, mortar with very fine droplets and SO2 in the flue gas contact and chemical reaction, the formation of sub Calcium sulfate and calcium sulfate, the use of heat in the flue gas droplets vaporized vaporization, the dried powder was flue gas desulfurization away.

Spray drying method can not only remove SO2, but also for SO2 and Cl-removal rate is also higher, generally up to 95%. This method does not produce wastewater and does not require wastewater treatment facilities. Drying tower operating temperature higher than the saturation temperature, purified flue gas without reheating equipment, the energy consumption is only half of the wet FGD process, more used in medium and small power plants.

Spray drying method will usually introduce lime, to a certain extent affect the comprehensive utilization of desulfurization products, higher operating costs. At the same time, this method is also prone to atomization nozzle clogging wear, easy deposition of solid matter, slurry ponds, bins and pipe scaling, dust removal equipment easy to cause local corrosion defects, resulting in lower utilization of desulfurization agent, usually only 45% to 55%.

2.3. Seawater flue gas desulfurization technology

Natural seawater contains a large number of alkaline soluble salts, natural alkalinity is usually 1.2 ~ 2.5mol / L, with natural acid-base buffer capacity and ability to absorb SO2.

The basic principle for the cooling flue gas into the absorption tower, and sea water in the reverse contact on the plate to remove SO2. The cleaned flue gas is discharged after demisting, and the seawater that has absorbed SO2 enters the aeration tank for aeration, until the water quality is fully recovered and returned to the sea.

Seawater desulfurization process is more suitable for burning low-sulfur coal in coastal power plants, the process is relatively simple, low investment and operating costs, there is no waste disposal problems, and high desulfurization efficiency.

2.4. Pulsed corona discharge plasma flue gas desulfurization and denitration technology

The basic principle of the high-voltage pulse generated by the pulse power applied to the electrode of the reactor, so that a strong electric field, electron ionization to produce part of the fumes molecules in strong electric field, the electrons gain energy in the accelerating electric field becomes strong energetic Electrons, high-energy electrons can activate, pyrolysis, ionization of other flue gas molecules, resulting in a variety of OH-, O2, H20 and other active particles and free radicals. In the reactor, SO2 and NOX in the flue gas are oxidized to high-grade oxide SO3 and chemically react with H20 in the flue gas to form H2SO4. When NH3 or other neutralizer is injected, (NH4) 2SO4 Of aerosol.

The process has the advantages of simple installation, low operation cost, thorough removal of harmful pollutants, no secondary pollution, etc., and can not only desulfurization and denitrification but also dedusting, by-products are good fertilizers in themselves. The technology is not widely used The biggest problem is the high energy consumption.

2.5. Wet flue gas desulfurization dust integrated purification technology

The basic principle of wet dedusting is to create the opportunity for the flue gas to contact with water. Adding desulphurizing agent into the water, then dedusting can be carried out at the same time. Wet dust removal mechanism can be summarized as the following: the use of inertia, Brownian motion, surface tension and gravity so that the dust particles are liquid droplets, liquid film retention, adhesion; dust particles co-condensing with each other, , Enhance the cohesiveness of the dust, and strengthen the above-mentioned dust-removing effect. The thermophoretic force and the electrostatic force cause the dust particles to be collected on the liquid surface to be removed.

Flue gas and water or washing liquid in contact with the following main ways: The use of atomizer to desulfurization agent containing washing liquid atomized into small droplets, sprayed into the flue gas, such as the spray chamber flue gas scrubber, so that flue gas By absorbing the liquid layer, the flue gas comes into contact with the absorbing liquid in the form of bubbles, that is, the flue gas is washed and the device utilizing the principle is currently being developed and applied more, such as a fluidized bed flue gas purifier, a turbulent tower flue gas purifier, a water bath Flue gas purification and so on. Use of inertia to make the flue gas contact with the water film, such as the cyclone water film dust collector, Venturi water film dust collector. The use of electrostatic force to make the flue gas in the dust and liquid film contact, such as electrostatic water film precipitator.

2.6 electron beam ammonia flue gas desulfurization and denitrification industrialization desulfurization technology

E-beam ammonia flue gas desulfurization and denitrification is a flue gas desulfurization and denitrification technology that uses high-energy electron beam to irradiate flue gas and convert sulfur dioxide and nitrogen oxides in the flue gas into ammonium sulfate and ammonium nitrate. The basic principle is to purify the flue gas first into the cooling tower to adjust the temperature and humidity, and then enter the reactor, encountered in the electron beam irradiation produce a variety of active groups, SO2 and NOX in the flue gas oxidation by these active groups, the formation of The corresponding acid, acid reacts with ammonia to form ammonia sulfate and ammonium nitrate particles.

The process is simple, not wet investment

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