Research On The Emission Control Of Acid Gases From Municipal Waste Incineration Power Plant

With the development of urbanization and industrialization in China, the amount of municipal solid waste is growing fast in recent years, and landfill is unable to meet the demand for waste disposal. Waste incineration technology has been more and more popular due to its advantages of reduction, harmlessness and recycling. The principle of municipal solid waste incineration for electricity generation technology is that intense chemical reactions occur with waste and oxygen at high temperature, heat energy released from these reactions is reused for electricity generation and heating, which is beneficial for recycling resources.Because of the complicated composition of municipal solid waste, secondary pollutants generated from incineration process are also complicated and the main pollutants include dust, NOx, acid gases（HCl and SO₂）, CO, heavy metals（Pb, Cd, Hg） and dioxins（PCDD/Fs）. With the application of low-nitrogen combustion, SNCR and three-T（temperature, residence time of flue gas and turbulence） technologies, NOx and dioxins（PCDD/Fs） are controlled effectively during incineration. However, there are still environmental risks due to incomprehensive consideration when calculating the discharged amount of HCl and SO₂ during designing, and high failure rate of limestone slurry preparation system and atomizing disc. Therefore, it has practical significance to study the generation amount of acid gases（HCl and SO₂） and the way to prevent pollution.Given the diverse conditions of municipal solid waste incineration, research in this paper mainly focused on the impacts of the generation amount of HCl and SO₂ under different conditions, such as different incineration temperatures, seasons, with injection of leachate, and coincinerating with sludge. Research result showed that there are mainly five measures to control incineration gas-emission under the Directive 2000/76 / EC standard on the incineration of waste, which are:（1） The more thoroughly the incineration is, the higher efficiency of conversion of chlorine and sulphur-containing substances into HCl and SO₂. Under high temperature, inorganic chlorine salts will decompose into HCl, which is also generated through chemical reaction between SO₂ and NaCl. Usually, boiler ceiling temperature is controlled between 850 950 ℃ during incineration.（2） In winter and spring, for the impact of low environment temperature, it is difficult for waste hard to be fermented thoroughly, and furnace temperature is lower than that in summer and autumn, in consequence, the generation amount of HCl and SO₂ is lower, too.（3） Injection of leachate has no impact on the generation amount of HCl and SO₂, but it is helpful to control the furnace temperature.（4） Co-incinerating with 10%（w） sludge would reduce the generation amount of HCl and SO₂.（5） Dry + Semi-dry deacidification process can guarantee the gases emission meet the requirements of EU2000/76 / EC standard about acid gases discharge; the amount of lime used in dry deacidification process can be reduced with lime slurry concentration of 4 8%, filter pressure difference of 1.4 to 1.6 KPa, gas temperature of 150 165 ℃ at reaction tower outlet.