Development Of The On-line Optimization Model For Delayed Coking Furnace

Coking furnace is an important equipment affecting the operation cycle of delayed coking plant.The furnace tube coking rate is a key factor in limiting the operating cycle of coking furnace.The traditional approach to determine the status of furnace tube coking is to measure the skin temperatures of the furnace tube.But the tube skin temperatures were influenced by the heat load,the convection heat transfer coefficient,the thermal resistance of the tube and so on.The traditional approach cannot fundamentally reflect the status of furnace tube coking.In order to eliminate influence such as the heat load and the convective heat-transfer coefficient,this paper presents new indicator such as coke-thickness number and equivalent skin temperature was used to diagnose the status of furnace tube coking.Furnace tube coking diagnosis and prediction system was developed in this thesis combined by commercial data.Based on the theory of heat transfer film,analyzing correspondence between the heat intensity and temperature difference for heat-transfer,a dimensionless number was deduced which is used to diagnose tube coking.This dimensionless number is defined as coke-thickness number.By introducing equivalent status,the measured tube skin temperatures were equivalently transformed into the same equivalent tube skin temperatures.These diagnostic method eliminate the operating state fluctuations which effect on the skin temperature,and more theoretical and precise characterize the status of furnace tube coking in the current operating status.In order to validate the effectiveness of diagnosis method,factors effect on the tube skin temperature during the startup was analyzed.The diagnosis method has been inspected by using the test data.The results indicate that coke-thickness number and equivalent skin temperature can significantly eliminate the fluid quantity and the inlet and outlet temperature effect on the skin temperature,characterize the tube coking situation and reflect the current trends of coking.In order to ensure furnace tube coking diagnosis method is applied conveniently for practical industry,furnace tube coking diagnosis and prediction system was developed by VB.NET,which can diagnose the degree of furnace tube coking and predict the remaining cycles.The software has been tested by the actual operating data.