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What technologies need to be used for desulfurization and denitrification in power plants?

2017-10-9 16:24:23

With the rapid development of thermal power industry, it has become one of the main sources of air pollutants emission in china. The burning of fossil fuels produces large amounts of gas, while the flue gas containing nitrogen oxides (NOx), sulfur dioxide (SO2), mercury (Hg), soot and other harmful substances are the main causes of air pollution, the problem of acid rain. Therefore, the demand for desulfurization and denitrification technology in thermal power plants is very obvious.

Electron beam (EBA) irradiation method is the use of electronic accelerator to produce high-energy plasma beam, SO2 and NOx of gaseous pollutants in the flue gas are high-energy plasma beam irradiation reaction to produce HNO3 and H2SO4, and adding proper amount of NH3 in flue gas generated by the reaction of ammonium nitrate and ammonium sulfate, the electrostatic precipitator to remove these by-products particles. This method can achieve 90% desulfurization rate and 80% denitration rate, and no pollutants, by-products can be processed into agricultural fertilizer, it is generally considered that it is a promising flue gas purification technology. However, this method still has the following problems: low reliability of equipment, high energy consumption of accelerator, difficult to capture by-products, consider the protection of X ray, ammonia leakage and other issues.

Electronic pulse corona desulfurization technology (PPCP) is formed by plasma high voltage power supply, producing a high energy electron, the chemical bond of SO2 and NOx in flue gas by high energy electron interrupted, produce free radicals, so as to achieve the purpose of desulfurization and denitrification. The characteristic is not to electron gun and radiation shielding, in ultra narrow pulse time, can accelerate the electron, there is no radical ion inertia is not accelerated, therefore, this method has much room for improvement in energy efficiency. Experiments show that the method can also remove dust from flue gas, and dust in flue gas has synergistic effect on desulfurization and denitrification. Because the technology uses high voltage power supply, the energy consumption is relatively high, and the operation is unstable. At present, the experimental research is not enough, can not be widely used, its investment is about 40% lower than the electron beam irradiation method.

Complex absorption technology is aminoxyacetic acid ferrous chelate and NO reaction of ferrous nitrosyl chelate compound. Ferrous ferrous chelates are formed by ferrous ions in neutral or alkaline solutions, such as Fe (NTA) and Fe (EDTA). Coordination and dissolved in nitric oxide can absorb O2 and SO2 reaction liquid in N2, N2O, N - S compound, ferric chelate and sulfate to remove SO2, and ferric chelate reaction generated ferrous chelate compounds to achieve regeneration. The main problem of this technology is the serious loss of the chelate in the reaction process, the low regeneration rate and the higher running cost.

Chloric acid oxidation technology is a wet washing method. The technology is divided into two parts: the oxidation absorption tower and the basic absorption tower. The oxidation absorption tower contains a solution containing oxidant HClO3, which is used to oxidize NO, toxic metal and SO2. The basic absorption tower contains absorbent containing Na2S and NaOH, which is used to absorb residual acid gas. The removal rate of nitrogen is over 95%, the desulfurization rate is over 90%, and some toxic metal elements can be removed. Because the catalyst is not used in the technology, there is no catalyst poisoning and catalytic efficiency decrease with time compared with the technology of catalytic conversion. At present, the process is still in the exploratory stage.