Structure Optimization Of FCC Feed Injection Zone And The Experimental Study On The Pressure Pulsations

FCC is one of the most key secondary processings in China refineries.The flow and contacting of feed oil with catalysts in the feed injection zone of riser reactor considerably influence the product yield/distribution,as it is the initial area of the mixing between oil and catalysts.On the other hand,the pressure pulsatin generally reflects the interacting of solids and gas.The relation of pressure pulsatin to the two-phase flow in feed injection zone is mainly investigated and it is anticipated to be used in engineering design ppurpose.In a large-scale cold model experimental setup,the gas-solid two-phase flows in four kinds of catalyst-feed counter-current contacting injection schemes were studied.The feed injection zones included equi-diameter structures with differernt sizes and varying diameter structures with different feed locations.Modern multiphase flow measuring techniques were used to study the axial and radial distributions of the solid hold-ups,the particle velocities,the characteristic concentrations of jet gas,and the standard deviations of pressure pulsations in these four feed injection zones under different operating conditions.The main factors influcing the standard deviation distributions of pressure pulsations were analyzed in detail.The results showed that the whole feed injection zone can be divided into three subzones,the jet gas upstream influence zone,the jet gas controlling zone and the jet gas downstream influence zone.The radial areas in different axial cross-sections of the feed injection zones are also distinct,including the particle controlling area,the pre-lift gas controlling area,the jet gas controlling area,the mixed gas controlling area and the gas-solid interaction area.Both the flowrate-ratio of the pre-lift gas to the jet gas and the particle flux generally influence on the distribution patterns of the pressure pulse strengths.Under the same solid flux,the decrease of the diameter of the feed injection zone increased the local solid flowrate,which restrain the downward penetration of the feed jets.Furthermore,based on the experimental data,the correlations between the oil matching indexes and the standard deviations of pressure pulsations in the feed injection zone weregiven,which provided a reference for evaluating the match degree of oil/catalyst through the standard deviations of pressure pulsations.