Studies On The Conversion Rule Of Waste Oil By Steam Cracking

Waste oil is a cooked mixture of waste edible oils and fats, unscrupulous traders madethe abandoned oil into cooking oil or used for the production of fried foods and sauces.It isharmfulto the society and the food safety.And great environmental problems will be caused ifit is discharged directly into the environment without anytreatment.Waste oil is an importantpart of the renewable energy, the main component is triglyceride that can be used to generatelight olefins by steam cracking.It not only can achieve good economic benefits, but also canreduce environmental pollution, resulting in greater environmental benefits.In this work, the influenceof different factors,including the cracking temperature, thewater-oil ratio, the residence time and unsaturationof the feed molecule on the productionrules of waste oil steam crackingwas investigated, in order to find the best operating conditionof the light olefins.The influence of different factors, including the mixing ratio, the crackingtemperature, the water-oil ratio andthe residence time on the production rules of naphthablended with waste oilwas also investigated.It is expected to use waste oil aspartsubstitutefeedstocks for steam cracking and to alleviate the situation of scarcity of raw materials.When waste oil was used as raw material,the yield of light olefins was graduallyincreasing with the increase of temperature, and when the temperature increased to750℃,thechanges of the light olefins yield were not obvious. The yield of the liquid product showed agradual decline trend.The liquid product acid value increases and then decreases.With theincrease of the water-oil ratio,light olefins and the liquid product acid value increase and thendecrease.When the residence time is increased,the yield of ethylene first increased and thendecreased when the residence time was greater than0.4s.The yield of propylene and1,3-butadiene did not change significantly.The optimum operation conditions were determined tobe,steam cracking temperature750℃,water-oil ratio0.8,residence time0.4s.When the steam cracking feedstock is naphtha mixed with different proportions of wasteoil,the result shows that the proportion of waste oil hasno significant effect on the yield of light oiefins.In the case of the mixing ratio of naphtha and waste oil being1:1, the optimumoperating conditions are obtained as follows,steam cracking temperature775℃,water-oilratio0.65, residence time0.35s.The cracking mechanism of raw materials can be divided into three parts:firstly,the estergroup of the waste oil is broken;secondly, a variety of long chain fatty acids aregenerated;thirdly,long chain fatty acidsare thermally cracked, forming a variety ofshort/medium-chain fatty acids and hydrocarbons;and the fatty acids and hydrocarbonscontinue to attendthermal cracking reactions and the secondary reaction to generate smallmolecules and aromatic compounds.