Simulation Calculation Of Oxygen-enriched Combustion In Vacuum Furnace

The vacuum heating furnace,being the key heating equipment of the crude oil distillation unit,is one of the main energy-consuming equipment in the oil refinery.The application of oxygen-enriched combustion technology in vacuum furnace can effectively improve the thermal efficiency,reduce fuel consumption,and therefore lower the operating cost of the furnace.In recent years,the research methods of oxygen-enriched combustion technology have mainly concentrated on experimental research and numerical simulation;the research objects are mainly concentrated on coal,coke and biomass solid combustion;the research fields are mainly concentrated on combustion characteristics,pollutant emissions and oxygen-enriched atmosphere radiation Heat transfer calculation method,etc.Due to the development of computer technology and the improvement of mathematical models,the errors of numerical simulation results are getting smaller and smaller,and computer simulation has become more prominent in research.As a new type of clean combustion technology,oxygen-enriched combustion technology has been widely used in industries such as steel smelting and pulverized coal combustion,and has achieved obvious technical advantages and significant economic benefits.At present,the application of oxygen-enriched combustion technology in the petroleum refining industry is still in the exploratory stage,and there are still some key technical problems that need to be resolved: on the one hand,the furnace temperature of the heating furnace increases,the risk of coking of the furnace tube increases,and the manufacturing cost is also an important constraint.The radiation chamber of the heating furnace is regarded as a combustion model based on a fully stirred reactor,and the combustion process is programmed and calculated in Fortran language.The purpose is to investigate the oxygen-enriched combustion characteristics of a26.4MW vacuum heating furnace using refinery gas as fuel.The effects of oxygen content,excess air coefficient,and radiant chamber volume on refinery gas combustion,flue gas composition,and radiant chamber temperature and fuel savings were investigated respectively and the combustion characteristics of refinery gas under ordinary air atmosphere were compared.In addition,the effect of oxygen-enriched combustion on the heat transfer characteristics of the convection chamber of the decompression heating furnace and the heat transfer characteristics of the heat pipe air preheater is also studied.The results are shown as following:(1)As the oxygen content in the combustion-supporting gas increases,the furnace temperature of the decompression heating furnace gradually rises,and the thermal efficiency of the furnace rises.The greater the oxygen content,the smaller the furnace volume required for refinery gas combustion to achieve the same conversion rate;(2)With the continuous increase of oxygen content in the furnace,the refinery gas burns more completely,and the residual amount of combustible components in the flue gas gradually decreases.When the oxygen content in the combustion air increases to 25%,the influence of the change of furnace volume on the combustion effect of refinery gas gradually weakens;(3)When the oxygen content is constant,as the excess air coefficient increases,the amount of combustion-supporting air increases,the emission of flue gas increases,the consumption of refinery gas increases,and the thermal efficiency of the heating furnace decreases.When the excess air coefficient is 1.1,the change of the furnace volume has the least influence on the combustion of refinery gas,the content of each component of the flue gas,and the temperature of the furnace.(4)As the oxygen content in the combustion-supporting air increases,the amount of flue gas produced by the combustion of refinery gas decreases,and the flow rate of the flue gas decreases,resulting in a decrease in the convective heat transfer coefficient;(5)The heat transfer coefficient of the heat pipe air preheater increases with the increase of the excess air coefficient.The greater the excess air coefficient,the more obvious the change in the heat transfer coefficient.