Research On Crossflow-jet Droplet Evaporation Inside Of The Ethylene Cracking Quench Cooler

The horizontal oil-quenching device is used in the ethylene cracking gas quenchingprocess, and it has the problem of coking during its field application. That quench oil dropletswhich can't evaporate completely adhere on the quench cooler wall is a main cause of coking.In order to understand the droplet evaporation of the quench oil, this article does a series ofwork on it.Firstly, single droplet evaporation formula is gotten from the basic convective heat andmass transfer theory, and it is verified using the n-heptane droplet evaporation in the nitrogenflow. Then, the formula is applied to the calculation of quench oil evaporation process, usingMatlab6.5 programming and numerical calculation method. Relationships of parameterschanging with temperature are obtained by data fitting and entered into the procedures ofcalculation. The influence factors of the quench oil droplet evaporation are analyzed by usingthe calculation results, including velocity, temperature, radiation, etc; The heat transfer law ofthe quench oil during its evaporation is also analyzed; The differences between ITC(infinitethermal conductivity) model and ETC(effective thermal conductivity) model are pointed out.The evaporation of the quench oil droplet inside of the quench cooler is dropletevaporation in the cross-flow jet. In order to understand this process, this article establishes anevaporation model in the cross-flow jet, which is programmed with Matlab6.5. Then, thisevaporation model is used for the quench oil droplet evaporation. Concepts of the best jetangle and the best droplet diameter of the quench oil are put forward, and their values aregotten by calculation. The best quench oil droplet diameter distribution with the jet angle isgiven, and the penetration depths and the flight paths of quench oil droplets with differentdiameters under different jet angles are also gotten.At last, this article makes a promotion of the single droplet evaporation model and tries toestablish a multi-droplet evaporation model, which shows that the evaporation of singledroplet is very different from that of the multi-droplet.According to the results of this thesis, the quench cooler is improved. Coking problem ofthe quench cooler is reduced sigficently, and its production cycle is extended.