Study On Process Optimization Of Light Alkane Dehydrogenation In A Circulating Fluidized Bed And Coking On The Catalyst In The Process

Different from western developed countries,light alkanes?propane or butane?are commonly utilized as fuels in China,which give rise to serious waste of resources.The conversion of light alkanes to olefins through dehydrogenation can not only promote significantly their high value-added utilization,but also meet the increasing market demand for light olefins.Therefore,in this paper,fundamental investigations in dehydrogenation of light alkanes in a circulating fluidized bed are carried out.?1?Fluidization performance and abrasive resistance of the catalyst for light alkane dehydrogenation.As for the developed PBD-type catalyst,the particle density,size distribution,minimum fluidization velocity and abrasion rate are investigated.The findings indicate that the catalyst PBD with good fluidization performance belongs to Geldart A particles.The abrasion rate of the catalyst PBD is 0.27%,which is only 1/8 to1/4 of that of other catalysts and shows extraordinary performance for circulating fluidization bed process.?2?Optimization of operating conditions for light alkane dehydrogenation process in a circulating fluidized bed setup.By employing a pilot-scale circulating fluidized bed unit,parameters optimization of operating conditions for the dehydrogenation process of light alkanes?propane,iso-butane,n-butane and their mixtures?were systematically investigated.Experimental findings indicate that the reaction temperature?T?and the gas hourly space velocity?GHSV?have great influences on the dehydrogenation process of light alkanes.Proper operating conditions for different feedstock were various.For propane,under the condition of T=600 ^oC and GHSV=1700 h^-1,the conversion of C₃H₈ is39%and the yield of C₃H₆ is 33%;For iso-butane,under the condition of T=580 ^oC and GHSV=1700 h^-1,the conversion of i-C₄H₁₀ is 48%and the yield of i-C₄H₈ is 45%;For n-butane,under the condition of T=580 ^oC and GHSV=1700 h^-1,the conversion of n-C₄H₁₀ is 39%and the yield of C₄H₈ is 33%.Additionally,the catalyst PBD shows high catalytic performances on dehydrogenation of light alkane mixtures.Appropriated operating conditions for different feedstock were finally obtained.?3?Coking on catalyst and its kinetics.The effects of reaction temperature,reaction space velocity and isobutene content in the feedstock on the coking amount of catalyst in the dehydrogenation of iso-butane were investigated by means of a fixed-bed reaction setup.The results show that isobutylene and reaction temperature have a significant effect on the coke content of the coked catalyst.When the reaction temperature exceeds 580 ^oC,with the increase of isobutylene content in feed gas,the amount of coke on catalysts increase rapidly.A catalyst coking kinetics model is also established by investigating in the relationship between catalyst coking rate and gas feed composition partial pressure.The model shows high accuracy.