Pilot Study On Riser Reactor's Structure For Maximizing Light Olefins By Catalytic Pyrolysis Of Heavy Oil

Ethylene and propylene are both important basic raw materials used in organic synthesis, and their global consumption is significantly upgrading lately, especially for propylene. Steam cracking with naphtha, which is the conventional process for producing ethylene and propylene, is now falling into a limited development in our country because of the shortness of feed with high quality and the production's limitation of propylene as a result of ethylene. As heavy oil is relatively abundant and cheap, the FCC processes using heavy oil as feedstock for maximizing ethylene and propylene are gaining more and more attention now.The thesis is completed on the basis of the Two-Stage Riser FCC(TSRFCC) technology in the newly-built FCC test unit. As there are several deficiency in initial unit, such as serious back mixing between the catalyst particles, low entrance velocity of oil and gas and being not able to achieve the stratifying injections of light and heavy feed in the riser, the newly-built unit is improved consequently. The added pre-lifting stage and the increased entrance velocity of oil and gas effectively reduces the back mixing in the riser; The increase of catalyst reserves and feed handling capacity, together with the true meaning of stratifying injections of light and heavy feed, makes the control of temperature and residence time and the selectivity of feed injection style more flexible. All these advancement lays good foundation for scientific research of the laboratory. Under the same conditions, there are less dry gas and coke, more light oil yield in the newly-built unit, compared with initial unit.The stratifying injections experiment on the best ratio of light and heavy feed and the experiment of maximizing Ethylene and Propylene by Two-stage riser catalytic pyrolysis technology(TEP) were carried on in the newly-built unit by using Fushun Atmospheric Residue, Qilu mixing C₄, Hengyuan light cracked naphtha and the catalyst LTB-2 under the instruction of the idea in TEP technology. The results showed the stratifying injections of mixing C₄ and FushunAR significantly increased propylene yield, compared with the reaction results of FushunAR alone. Propylene and ethylene yield gradually increased as a result of the increase of ratio of mixing C₄ and FushunAR, however, they began to decrease when the ratio was too large. The optimal ratio was between 25% to 30%. In the experiment of TEP technology, although the ratio was less than 25% in the first-stage reaction and the feed of the second-stage reaction was adversely the mixing of heavy cracked naphtha, diesel and heavy oil coming from the product of the first-stage reaction, the single conversion of fresh feed still reached 85.77%, the yield of total desired products were 77.81% and the low value products were only 11.72%. The sum of ethylene and propylene yield achieved 39.21% and high selectivity of ethylene and propylene were attained simultaneously. The gasoline, whose yield was 23.16% and in which the content of aromatics reached 64.93%, can become reconciliation component for high octane-number gasoline. If the ratio reached the expected value and the mixed feeding was avoided in the second-stage reaction, it is estimated that the sum of ethylene and propylene yield would be more than 40%, which reflected the apparent advantage of TEP technology in maximizing ethylene and propylene.