Simulation Of A Catalytic Distillation Process For Production Of Ethylene Glycol Monoethyl Ether

Glycol Ethers is an excellent organic solvent, widely used in various industries; in addition, it is a great demand in the market. The traditional process, used to product glycol ethers, is generally tube or tank process, therefore, it have lots of disadvantage, such as lower yield of the target product, higher equipment investment cost, higher energy consumption, severe corrosion problem, etc. Taking Ethylene Glycol Monoethyl Ether (EGME) as a product, this paper presents a new process-catalytic distillation to solve these problems. To analyze the steady-state and dynamic characteristics of the process, a simulation study is completed with the software, furthermore, an effective control strategy and start program are developed on this basis, aiming at providing a theoretical basis and guidance for the application of catalytic distillation technology in the industrial production of Glycol Ethers.In this paper, the main research contents and conclusions are as follows:(1) Based on equilibrium stage theory, the process simulation, for the EGME catalytic distillation column in steady state, is completed through Aspen plus. Total reflux mode of operation is used in the column, excess Ethyl Alcohol (EtOH) was fully utilized. For the above reasons, on the basis of conversion in EtOH at 82%, the selectivity of EGME is increased to 89%.(2) The dynamic simulation study of semi-batch catalytic distillation column has been taken out using Aspen Dynamic. Dynamic behavior of vertical distribution of temperature and composition, conversion of EtOH, selectivity of EGME has been explored through simulation. Then, in the feed rate of Ethylene Oxide (EO)10kmol/h, several operating parameters are optimized including:EtOH/EO mole ratio in the feed, heat duty of reboiler, feed location through simulation. The optimal operation parameters are determined to be:mole ratio 1.15:1, heat duty 1500kW, feed location 3 5. As a result, conversion of EtOH increased from 69.4% to 82.29%, selectivity of EGME increased from 81.23% to 89.68%.(3) On the basis of the optimization results of the steady-state, design and simulation of control schemes for the EGME catalytic distillation column is completed. First of all, according to the steady open-loop gain of tray temperature to manipulated variables, the 12th plate was selected as the sensitive plate tray. In the research system of this paper, stability of the system is very sensitive to EtOH/EO mole ratio in the feed, therefore, a control strategy is developed in which feed rate of EtOH is as a manipulated variable. Then, two different control structures are developed which is CS1 and CS2. In CS1, feed rate of EtOH control reflux drum level and in another, feed rate of EtOH control temperature of sensitive plate. In the control loops designed, controllers are all designed to PI controller. Parameters of EO feed controller and pressure controller are given the value of experience (EO feed controller Kc=0.5,T1=0.3; pressure controller Kc=20,T1=12), on the other hand, all other parameters are tuned using the Ziegler-Nichols method, thus, the influences of to the control from tuning parameters of controller. Finally, the step signal of EO feed rate changes in±10% is added to the controller and analysis and comparison of the response curves are completed. With the same expected results, the EtOH/EO mole ratio in the feed is effectively stabilized, thus, product quality are well controlled in CS1 or CS2. Compared to CS1, CS2 has a better performance including:smaller Maximum Deviation, shorter Transition Time; Maximum Deviation of product quality and the residue could be controlled within 0.54%; Transition Time is 4h.(4) In the research system of this paper, EO is flammable and explosive dangerous goods and EtOH is excess in feed and mode of operation is total reflux. According to these characteristics, total reflux startup program has been developed. In the program, EtOH was stabilized at a state of total reflux in column, neither feed nor products at the initial time. During startup, heat duty of sump is fixed, at the same time, pressure and the level of reflux drum and sump are automatically controlled. They have the same control loops and parameters with CS2.The startup process is modeled by Aspen Dynamic, in addition, dynamic responses of variables was analyzed and find that the startup program has many advantages, such as shorter start-up time, smaller fluctuation range, more stable process. In the role of this startup program, pressure and level can restore stability in 3h; their Maximum Deviation is only 1.3%; response curve of composition in the product are very smooth; the reaction profile is stable; the whole startup process could be completed within 6h.