Study On Process Of Flue Gas Desulfurization Using Ethylene Spent Caustic And Project

Coal production in China is the first in the world. In the future, energy structurewhich is given priority to with coal in the electric power industry will not change in along time. SO₂generated in coal combustion process will lead to air pollution, acidrain, and severe corrosion such as boiler, pipelines and other mechanical devices.Concentration of sulfur dioxide emissions in2011is more strict than before asstipulated in the <the standard management method of the sewage charge collected>.At present several major flue gas desulfurization technologies are reviewed inthis paper. Combing with comprehensive treatment at home and abroad of ethylenespent caustic, we studied a new desulfurization technology and advances the flue gasdesulfurization technology mode——Ethylene Spent Caustic Applied in FGD mode.We can conclude under high efficiency and the steady state of process parameters toachieve the purpose of using waste treat waste.Experiments of flue gas desulfurization were simulated by using three groups ofdifferent concentration ethylene spent caustic as absorbent. The influence of affectingfactors including inlet gas temperature，oxygen content in flue gas, ratio of liquid togas volume, SO₂concentration at the inlet of flue gas and velocity of flue gas on theefficiency of flue gas desulfurization was studied．It was also analyzed on theeconomic benefits that this process technology is used for one plant．The experimentalresults show that the inlet flue gas temperature is higher, the desulfurization efficiencyis lower; With increasing the concentration of NaOH and Na₂CO₃, highdesulfurization efficiency increases first, then gently; When the inlet flue gastemperature drops to80℃⁹0℃, desulfurization efficiency and economic costare best. When the inlet flue gas oxygen content is less than5.5%, the flue gasdesulfurization efficiency will grow faster along with its growth, when more than5.5%, desulfurization efficiency gradually slow growth;2.0%NaOH/7.2%Na₂CO₃and3.0%NaOH/8.2%Na₂CO₃concentration of spent caustic desulfurization rate ishigher. When liquid gas ratio is1³.5L/m³, desulfurization efficiency also increaseswith the increase of liquid gas ratio; When the liquid gas ratio is greater than5L/m³, the desulfurization efficiency is steady state. When inlet flue gas concentration of SO₂is in460⁶40mg/Nm³, it is little effect on the desulfurization efficiency. In the fluegas velocity of2.0⁴.0m/s, the desulfurization efficiency increases with theincreases,1.0%NaOH and6.2%Na₂CO₃ethylene spent caustic of desulfurizationefficiency increases fastest; And the other two sets of relatively high concentrations ofethylene spent caustic desulphurization efficiency are basically unchanged during3.0⁵.0m/s;3.5⁴.5m/s of flue gas flow velocity is suitable.In order to determine organic compounds and various ions in the ethylene spentcaustic may influence for absorption equipment and absorption process, we havedetermined the composition of spent caustic, and analyzed the trend of foam. Basedon ethylene spent caustic composition detection, ethylene spent caustic from wet airoxidation still contains a certain amount of organic material such as oil. Oil and otherorganic materials are brought into to absorb tower, in which they are saponatedreaction, and formed bubble in the surface of the absorber slurry. When the gas flowvelocity is at2.5m/s⁵.0m/s, foam layer is not very stable. As defoaming time isshort, it is difficult to form the accumulation bubble; When the gas flow velocitydecreased to0.14m/s, the foam height obviously increase and defoaming time is ashigh as60s （It’s not easy to accumulate bubble for defoaming time at10s or less）. Itshows that when the flue gas flow velocity of ethylene spent caustic from wet airoxidation is lower, ethylene spent caustic have certain foaming tendency. When thequantity of bubble affects desulfurization efficiency in the absorption tower, we canadd appropriate defoamers such as Polyether Modified organosilicon defoamer toeliminate bubble and improve desulfurization efficiency.Flue gas desulfurization engineering by ethylene spent caustic method in thermalpower plant in Daqing petrochemical company as an example, the article introducesthe engineering general situation, system composition and the main economic andtechnical indicators of desulfurization system. We have analyzed economic benefit forthis project. Every year3623tons SO₂can be removed. This device will bringtremendous environmental benefit and social benefit for country.