Design Of Float Valve Distillation Tower Dealing With 108 Thousand Tons Of Benzene-toluene Yearly

Tower is an important equipment for the mass and heat transfer between vapor-liquid or liquid-liquid phases, which is widely used in steam (fine) distillation, absorption, desorption, stripping, extraction and other chemical unit operations. The float valve tower, as the main separation facility in chemical production, has become the most widely imployed domestic tower, especially in petroleum and chemical industry.In this thesis, the design is to separate benzene-toluene feed liquid, and benzene is 40 wt%. The annual processing capacity for the tower is 108 thousand tons, with an overhead condenser and partial reflux. The calculation of distillation process is in terms of the conventional algorithm. According to the graphic method, the obtained theoretical tower plate number is 17, and the feed plate is the 7th one. The efficience of the whole tower was 0.612, considering the relationship between the liquid viscosity and relative volatility. Based on this, the actual number of the tower plate is obtained, with 10 actual plates for the rectifying section and 17 ones for the distillation section, and the actual feed plate is on the 11st board.Then, the tower diameter is worked out as 1.6 m. The tower plate is composed of single overflow, arc downcomer and concave shaped liquid disc. The float valve is arranged in diamond array and then the number of float valve is obtained. The mist entrainment, flooding, liquid load upper limit, liquid load lower limit and weeping has been checked, and the flexibility of operation for rectifying and stripping section is 4.6 and 3.05, respectively. The operating point of the tower meets the requirements of the operation.The distillation process simulation is performed by using Aspen Plus programme. Comparing with conventional algorithm, the optimum reflux ratio obtained from Aspen Plus software simulation is smaller. Meanwhile, the heat consumption of the reboiler and condenser calculated by Aspen Plus is lower. The annual total cost with the above two methods is compared, and the calorific value converted into standard coal conversion is calculated, respectively. It will bring economic and environmental benefits for the enterprises. According to the RadFrac model of Aspen Plus, the heat transfer area for condenser is 39 m2, and 138m2 for reboiler. The total height of the tower is also worked out. Q345R, a kind of low alloy steel with higher strength than Q235, is chosen as the material for the tower body.Finally, SW6-2011, a calculation software package, is used for mechanical design of float valve tower. After calculation and check of the equipment strength, the result of design is as followed. The head is 12mm in nominal thickness and 415.41Kg in weight; the tower body is 10mm in nominal thickness and 8922.25Kg in weight; the skirt is 10mm in nominal thickness and 4.8m high. Other parameters such as container shell strength of the whole tower, the wind and earthquake load, have also been listed.In this paper, the process design of the distillation column is carried out. The theoretical plate number, column efficiency, actual plate number and feeding location are obtained. Furthermore, the parameters of installation, such as the tower load and anchor bolt are designed as well.