Pollutants Transfer Mechanism Of FCC Regeneration Process

Fluid catalytic cracking(FCC)process is one of the core processes in the petroleum refinary industry,and it is of great significance to further control FCC pollutant emission by researching the transfer mechanism of pollutants during FCC regeneration process.In this work,three spent catalysts from different typical industrial FCC units were selected,and analyzed by different characterization methods.Coke precursors of the three spent catalysts were analyzed by EA,IR,and XPS.Regeneration experiments were conducted to monitor flue gas emissions during regeneration experiments under different regeneration atmosphere by a new online FTIR instrument,Gasmet 4000.This work summarized the transfer mechanism of carbon,nitrogen,and sulfur-containing substances in the regeneration process based on the characterization and experimental results.Main research results include several parts.The coke precursors'characterization revealed that the carbon-containing species mainly exist in the form of aliphatic carbon,aromatic carbon,ethers or phenols,and esters;the nitrogen-containing species mainly exist in the form of pyridine nitrogen,pyrrole nitrogen,quaternary nitrogen and nitrogen oxide;and the sulfur-containing species mainly exist in the form of sulfate,sulfone and thiophene.Regeneration experiments revealed that the pollutant emission temperature range is almost same under different regeneration atmospheres,and the regeneration process can be divided into three temperature ranges,low temperature range(below 400?),high temperature range(400?700?)and very-high temperature range(above 700?)according the emission polutants.In the low temperature range,C7H8,C8H10,NH3 and NO2 are the main emission polutants.In high temperature range,CO2,CO,CH4,HCN,NO,NO2,N2O,and SO2 are the main emission polutants.In very-high temperature range,NH3,NO2,and SO2 are the main emission polutants.The influence of oxygen concentration on spent catalyst regeneration is mainly reflected in two aspects,including emssion temperature range and emssion amount.With the increase of oxygen concentration,the speed and degree of coke oxidation and decomposition are both increasing,the emssion temperature range will move forward,and the overall emission amount will increase.With the addition of water vapor,the overall emissions are reduceing.Combining precursors' changing,regeneration conditions and pollutant emissions,the transfer mechanism of carbon,nitrogen,and sulfur-containing substances in the regeneration process is provided,which could be helpful to predict pollutants emissions and pollutant emission control in the refinery industry.