Experimental Study On The Collaborative Removal Of Sulfur And Mercury During Decoupled Combustion Of Coal With High Content Of Sulfur

At present, air pollution is more serious on account of coal combustion in our country, ultra-low emission control technology is vigorously promoted in coal-fired power plants over the country,which brings about higher operation cost and more complex end-of-pipe treatment process of SO2,the main pollutant after coal burning.At the same time,mercury emission from coal combustion is considered to be the main source of mercury pollution in the atmosphere,pollution to the environment problem has attracted extensive attention all over the world.Up to now,In China there is no commercial economic and efficient mercury removal technology for the coal-fired power plant.Researches indicates that there is positive influence between sulfur and mercury in coal with high content of sulfur and mercury removal adsorbent.Besides,S and Hg release from coal under similar temperature during pyrolytic process and as pyrolysis products they have chemical reaction basis.In consequence,the reduction in the coal pyrolytic process can be realizable.H2S is the key component of sulfur in coal pyrolysis gas,and the vast majority of sulfurous gas in the flue gas is SO2,while H2S and SO2 can generate elemental S under certain condition.The main form of mercury is Hg0 no matter in the pyrolysis or combustion process.Elemental sulfur can generate HgS with elemental mercury.Based on the above theories,a new method of low sulphur-mercury emissions from coal combustion is proposed,which basic idea is that coal combustion process with high content of sulfur is divided into pyrolysis and combustion process. H2S and SO2 produce elemental sulfur,which further react with elemental mercury, by controlling sulfur pyrolytic product,and the final products will be released from coal pyrolysis gas,which most of the sulfur and mercury can be synergeticaly removed in the initial combustion process.Based on the above technical route, two sets of experiment system were set up,H2S-SO2 reaction experiment system and S-Hg reaction experiment system. Firstly,characteristics and effect factors of the low concentration H2S-SO2 reaction were studied.The results showed that H2S hardly reacted with SO2 without catalytic.Higher reaction temperature with drop of economical efficiency and safety was difficult to apply in practical production.Catalytic addition significantly reduced H2S-SO2 reaction temperature. The highest reaction rate was 87% under 250 ℃,while there was no change on reaction rate with raise of temperature.Optimum reaction molar ratio H2S:SO2 was 2:1,which the average reaction rate was higher and reaction remaining gas was less. The increase of the reaction time can make the reaction more thoroughly and promote the reaction rate.But when the reaction time reached 2s,increase of the reaction rate was no longer obvious.Although catalytic addition significantly promoted the reaction,but addition amount restricted rising trend. O2 had a greater influence on the reaction, the ratio of gas disorder in the reaction of H2S and O2, limiting balance to the direction of sulfur generation.Thus,the ratio of gas would be changed on the basis of O2 concentration.CO2 nearly has no effect on the reaction on account of no secondary reaction and little influence on primary reaction.Secondly.characteristics of S-Hg reaction and effect of temperature on S-Hg reaction were studied in a fixed bed reactor experimentally. The results showed that elemental mercury and sulfur could react at normal temperature,but the reaction rate was low at low temperature,and mercury oxidation rate was the same.With the temperature increased,the reaction rate went up.Mercury oxidation rate reached 55% at 250℃,and arrived 70% at 400 ℃.There was no significantly enhancement on oxidation rate with raise of temperature.The study indicated that different containing sulfur compounds from high sulfur coal pyrolysis product could react with catalytic and optimum reaction conditions were studied.Elemental mercury and sulfur could react under certain temperature,which showed that mercury and sulfur low emission during decoupled combustion of coal with high content of sulfur can come true by reasonable organization...