Numercal Research On Non-Uniform Heat Transfer And Its Impact On Ethylene Cracking Furnace

The ethylene cracking furnace was the core unit, and the thermal cracking process was one of the most important technologies of the ethylene industry. The main and complex process in a pyrolyzer include flow, combustion, pyrolysis reaction and heat transfer. China falls behind other countries of the cracking furnace in design and development. Only some foreign corporations hold the whole technique of cracking process. Thus, it is very significant to study details of transfer and reaction process in the cracking furnace.In this study, the numerical simulation of the flow and heat transfer in firebox and the reaction in tubes were carried out by establishing a three-dimensional model of a KTI GK-V cracking furnace. Majory research work was listed as follows:(1) A numerical model of the 1/4 furnace was developed by taking account of integrated phenomena that involves heat transfer, flow and pyrolysis reaction. The coupled impact of firebox and tubes was also studied. According to the research, non-uniform distribution of heat transfer existed in furnaces, thus resulted in a non-uniform distribution along the reactor tubes and a different product yield in each reactor tube. The mutual effects of heat transfer in the firebox and cracking reaction was responsible for the distribution of the heat boundary.(2) The coupled simulation was also carried out by establishing a three-dimensional model of the 1/2 furnace, which was close to the reality. The 1/2 furnace contains two sets of coils. According to the research, the temperature distribution was different between the 1/4 furnace and the 1/2 furnace due to the asymmetric structure. The coils which were near the wall got a poor heat transfer. The heat boundary condition and cracking reaction in 1/2 cracking furnace and 1/4 cracking furnace was different, due to the furnace tubes'non-uniform heat transfer, which caused different primary product yields.(3) The study of the feed quantity in the firebox and tubes on the yield of the main furnace were carried out. It was found that feed rate affected the secondary reaction in the pyrolysis furnace and the main product.