Ethylene Feedstock Expansion And Optimization Based On Structure Oriented Lumping Method

With the rising price of international crude oil and the increasing competitive products all over the world, widening ethylene feedstock and optimizing steam cracking process are effective ways to improve the yield of olefins. Kinetics model of steam cracking reaction based on structure oriented lumping method was built to study cracking process conditions and blending ratio of Naphtha(NT), Heavy Vacuum Gas Oil(HVGO) and Waste Cooking Oil(WCO).Firstly, depending on the molecular structure of feedstock, seven kinds of structural units were selected to describe naphtha, six kinds of structural units were selected to describe HVGO and eight kinds of structural units were selected to describe WCO. NT, HVGO and WCO were described by39,106and6kinds of molecular to establish molecular matrix, respectively. According to the cracking reaction mechanism of petroleum hydrocarbons and fatty acids,343reaction rules were built to reflect steam cracking reactions of NT, HVGO and WCO. A method had been established to calculate the rate constant of cracking reaction based on transition state theory. Then the processes of molecular reactions were simulated. A kinetics model of steam cracking reaction was established based on structure oriented lumping method.The steam cracking technology and parallel test were studied in experimental device. Compared the experimental date with industrial date, it conformed the experimental device had good reliability. Under the same process conditions, compared calculated with experimental product distribution of NT, HVGO,80%NT+20%WCO and20%NT+80%, the result showed the errors were less than8%. It illustrated the model had high predicted accuracy. At the same time, compared calculated with experimental product distribution of HVGO under different process conditions including temperature, residence time and water oil ratio, the result showed the errors were less than8%. It proved the model based on Structure Oriented lumping method had good adaptability.Finally, the optimized cracking conditions and blending ratio using model based on Structure Oriented lumping method were calculated. Process conditions and different blending ratio were investigated in experimental device at the same time. Compared calculated optimized conditions and optimized blending ratio with the experimental date showed that the values calculated by the model were quite consistent with the experimental data. It illustrated the model can optimize cracking process conditions and blending ratio. The model showed20%NT+80%WCO was optimized feedstock. When the feedstock was20%NT+80%WCO, the yield of ethylene went up to30.96%under the optimized condition of reaction temperature850℃, duration0.77s and water-oil ratio0.81. A total yield of ethylene, propylene and butadiene were52.58%. Under the same condition, the yield of ethylene of20%NT+80%WCO was5%higher than the yield of ethylene produced by Naphtha. Blending WCO instead of naphtha as feedstock to produce ethylene can broaden the sources of feedstock.