| Fluid Catalytic Cracking Unit(FCCU)is an important oil refining process,with annual domestic handling capacity of more than 100 million tons.Fractionation system and absorption-stabilization system are the separation sections in FCCU,and the energy consumption,product yield and quality of the system will affect the entire economic benefits of refinery process.Adoption of the advanced column equipments,development and utilization of advanced technological process contribute to the realization of the state's strategies in energy consumption reduction.Therefore,it is of great significant for national economic construction,environmental protection and social development which the optimization of FCCU process and research and industrial application of new column trays.In this thesis,simulation of the whole process of the separation sections of FCCU is conducted with the commercial software Aspen Plus based on some local refinery production data.To verify the accuracy of the model,the property method Grayson-Streed was used for main fractionator and RK-Soave for the absorption-stabilization system and the obtained simulation results were consistent with the local refinery production date.Then,the optimization analysis of entire process of fractionation and absorption-stabilization system is carried out.The gasoline and diesel oil distillation curve could be changed effectively by adjusting the circulation of top and middle for main fractionator tower when other conditions were kept invariable under certain temperature for circulation stream and top production.For the absorption-stabilization system,the absorption rate is obviously increased by adding appropriate intermediate condenser at the middle part of the absorption tower.Increasing the flowrate and reducing temperature of the adsorbent reduce effectively the percentage of C3 and C3?components in the dry gas.Considering desorption of absorption-stabilization system,adding the middle reboiler can effectively improve the thermal efficiency,and the thermal efficiency varies for different feeding ways.For cold feeding,the method of condensing followed by heating leads to the overload in reboiler.A higher thermal efficiency is observed for hot feeding,while it is inclined to excessive desorption.It is found that the thermal efficiency of two-level feeding is higher than that of single-stage feeding,and a special control for the stabilizer tower is necessary for the bottom temperature.The results of the optimization analysis are of great guiding significance for engineering design and operations.Furthermore,a new type of fixed valve tray was proposed,named fixed rotary valve tray,based on a round fixed valve tray developed previously by ZJUT.The fixed rotary valve consists of a valve cover and three valve legs,and the projection surface is a circular area with diameter of 40mm or 50mm diameter.The edge of the cover is deflexed and the valve surface is punched with three 2mm downward arced indentations.The three valve legs are uniformly arranged with 120°interval with a lean in the direction of the arc.Hydraulic performances of the fixed rotary valve tray,including dry and wet pressure drop,are experimentally investigated with air-water system in a 600mm ID plexiglass-column.The effects of the parameters of the valve,including type,quantity and diameter and the open area of the bottom of downcomer on the hydraulic performances are also discussed.In addition,some experimental studies are conducted in a 1200mm plexiglass column.Generally,this work could be theoretically beneficial for the technological design and operation of the FCCU fractionation and absorption-stabilization system,and fundmentally significant for the further research of fixed rotary valve tray. |
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