Conversion Of Glycerol And Oil Into Syngas By Rotating Arc Plasma

Waste edible oil is generated from catering. More than 5 megatons of waste edible oil has been produced in China every year, causing serious pollution and various social problems. Crude glycerol is one of the most stable byproducts of biodiesel production and facing the badly surplus. Currently there exist many problems about the disposal of waste edible oil and crude glycerol, so an environmentally friendly technique is needed to achieve resources utilization. Thermal plasma, which can produce large density of active particles, has characteristics of high temperature and high enthalpy. By thermal plasma, waste edible oil and crude glycerol could be converted into syngas without any pretreatment. It’s a promising method for the disposal of waste edible oil and crude glycerol because of its short process and non-catalyst. In this study, glycerol and soybean oil were converted into syngas in a homemade rotating arc plasma torch/reactor. Effects of different parameters on reaction characteristics were investigated to make solid foundation for the future industrial application.In this study, the mixture of pure glycerol and deionized water was used as a substitute of crude glycerol. Effects of input power, feed rate, water/glycerol mass ratio and magnetic induction on glycerol conversion were investigated. The results demonstrated that a large amount of syngas, accounted for 92.17vol%-97.78vol% of product gas, with a small amount of CO2 and hydrocarbons could be obtained. With the increase of input power and decrease of feed rate, the content of H2 increased while that of CO2 and hydrocarbons decreased. Carbon conversion increased with input power and could reach 100%. Energy conversion efficiency grew to a maximum, about 64.54%, before it began to decrease. Increased water/glycerol mass ratio would lead to more H2 and CO2 but less CO and hydrocarbons in product gas. Energy conversion efficiency and syngas yield decreased with the increase of water/glycerol mass ratio but carbon conversion didn’t change significantly. H2/CO mole ratio increased from 1.49 to 1.95 and could be used as raw materials for the synthesis of methyl ether. Magnetic induction has little effect on results but it could protect the anode from erosion. Compared with other forms of plasma for glycerol conversion, this work shows a better result with higher carbon conversion and syngas yield. For the production of syngas with H2/CO mole ratio of 1.5, the optimum condition is that input power/feed rate is 0.21 kW/(g·min-1) and water/glycerol mass ratio is 0.18. Under this condition, carbon conversion reaches to 99.27% and energy conversion efficiency is 64.39%. H2/CO mole ratio is 1.48 and yields of CO and H2 are 91.06% and 82.33%. The production cost is 1.58 yuan/Nm3.Soybean oil was used as a substitute of waste oil and effects of input power, water/soybean oil mass ratio and magnetic induction on reaction characteristics were investigated. Similar to glycerol conversion, the main product gas was CO, H2, CO2 and hydrocarbons. Syngas was accounted for 89.30vol%-95.10vol% of product gas, smaller than that from glycerol conversion. Carbon conversion increased to 98.53% with the increase of input power and energy conversion efficiency reached the maximum of 72.86% at 17.86 kW. H2/CO mole ratio was maintained at 2.45-2.68 as product gas compositions changed slightly. Water/soybean oil mass ratio has a large impact on product gas compositions and energy conversion efficiency but little impact on carbon conversion and syngas yield. The yield of H2 and CO decreased with the increase of water/soybean oil mass ratio. H2/CO mole ratio increased from 2.13 to 2.58 and could be used as raw materials of methanol or F-T synthesis. The best condition for syngas production with H2/CO mole ratio of 2-2.5 is that input power/feed rate is 0.17 kW/(g·min-1) and water/soybean oil mass ratio is 1.38. Under this condition, carbon conversion is 86.28% and energy conversion efficiency is 72.86%. H2/CO mole ratio reaches to 2.56 and yields of CO and H2 are 59.46% and 76.93%. The production cost is 1.58 yuan/Nm3, smaller than that from glycerol conversion. Compared with crude glycerol, syngas from waste oil conversion has a smaller syngas content but larger H2/CO mole ratio and energy conversion efficiency. Its production cost is smaller than that from crude glycerol conversion. So it’s better to be feedstock for syngas production than crude glycerol.