SO₃Behavior In Oxy-fuel Combustion

Anthropogenic emissions of CO2have generally been accepted as a main cause forglobal warming, CO2produced from coal fired power generation is a large part of theglobal CO2emissions. Reduction of CO2from coal fired power generation is particularlyimportant in China because that nearly70%of the energy consumptions in this country arefrom coal and this situation will continue for years. The oxy-fuel process which supplies astream of CO2suitable for sequestration is one of the most promising and combustiontechnologies for CO2capture and sequestration(CCS) as this process has significantcommercial advantages and technical feasibility and the retrofit technology for existing coalfired power plants is very Convenient. In oxy-fuel firing, enrichment of SO2, extending ofresident time of flue gas and volumetric change in gas flow result in the increase of SO3concentration in flue gas. The higher sulphate levels inside the furnace during oxy-fuelfiring will result in more serious slagging behavior in convection zone, plugging in SCRand inhibited mercury oxidation as SO3would compete for the same oxidation sites.problems of SO3limit the application oxy-fuel technology. Some researchers started aseries of study on SO3by experiment and simulation.The effect of temperature, initial SO2concentration and H2O concentration on SO3formation were investigated in the simulated flue gas during oxy-fuel combustion. Theexperiment included two parts: one was conducted in a horizontal tube furnace below1100℃, the other was conducted in a high-temperature drop tube furnace under1500℃.CO2, O2, H2O and SO2were mixed to simulate flue gas.As the temperature increases, SO3concentration firstly increases then decreases andthe highest value appears at950℃. Most SO3forms around950℃.this because of changesof the O concentration and the rate of SO3dissociation at different temperature. SO3 concentration increases as initial SO2concentration increases, but SO2and SO3bothconsume O, thus SO3/SOxrate become smaller as the lack of O in SO2oxidation. SO3formation obviously declines when H2O is added into reactor. H2O compete O with SO2byturning much O to OH, but only few SO2can be oxidized by OH, so SO3formationobviously declines.