Study On Modeling Of Thermal Cracking And Its Application

Basic chemicals such as ethylene are currently manufactured mainly from hydrocarbon by thermal cracking. Thermal cracking reactions are basically used to break the C-C or C-H bonds of hydrocarbons at a high temperature and at a low pressure, they finally produce lower molecular weight olefins such as ethylene, propylene, butene, butadiene and aromatics such as benzene, toluene, xylene. Cracking mechanism is very complicated and the modeling of thermal cracking is developing to three models:experimental model, molecular model and free radical model. This three models are built up separately and applied in the industry.Above all, the pilot plant was built in the lab to simulate the furnace in the industry. The experimental data such as process data, product yields can match the data from the furnace in the industry. That shows the experimental data can be used to build the simulation model.The experimental model was built based on a large number of the experimental data. A SVM regression algorithm for modeling of thermal cracking of naphtha was developed using as input the analytically determined commercial indices of naphtha and process data, the model can predict the product profiles including 24 product yields. A comparison between model results and industrial data was carried out and good agreement was found, the model can be used in advanced process control in the cracking furnace.The molecular model of naphtha cracking was developed from the KUMAR model, the parameter of primary reaction was estimated based on the experimental data. The result of the model shows, increasing the coil out temperature causes the ethylene yield and low molecular weight products yields to rise. On the other hand, the propylene yield and high molecular weight products yields may have a maximum value and then decrease.The free radical model of C4 alkanes is developed according to the free radical model of ethane and propane, the result of model can meet the data in the industry. The result shows, on the one hand, more radical C2H3·and 1-C4H9·were produced and then the ethylene yield was high in the cracking of normal butane; on the other hand, more radical C3H5·and 2-C4H9·were produced and then the propylene yield was high in the cracking of isobutane. The mixture of normal butane and isobutane casued the ethylene and propylene yields to dereace.A new method for feedstock reconstruction of industrially important hydrocarbon fractions is developed using as input the analytically determined commercial indices, The 32 real components are selected to describe the pyrolysis reaction performance of naphtha. We can get the result through solving the equations set, a good correspondence exists between the simulated result and the analytically ones, the model can be used in a simulation package for steam cracking. The result shows, just as SPYRO, the model can be used to describe the naphtha cracking. This becomes a corner stone for developing the free radical mechanism of naphtha.