Data Processing And Real-time Optimization Of Acetaldehyde Production Process

Invention of the Wacker process, which is an industrial process for the commercially manufacture of acetaldehyde by directly oxidizing ethene, is a milestone to petrochemical industry. It provides the basis for industrial-scale production of acetic acid, acetone, ethyl acetate, ketene, acetic anhydride, butyraldehyde and vinyl acetate. Optimizing the process operation and management by means of advanced information technology and automation technology is an efficient approach to increase acetaldehyde's production capability. The real-time optimization(RTO) scheme was studied in this thesis, with focus on the crucial problems of steady state detection, data reconciliation, soft modeling and optimization implementation. A practical operation optimization system was developed and applied to the real plant.The main contributions of the work can be summarized in the following:1. It is pointed out that data preprocessing is of great importance to modeling and optimization. A unified algorithm for data merge and steady state detection was presented.2. For reaction process, a data reconciliation arithmetic based on atoms was developed. To get mass flow rate of vent gas and coarse aeetaldehyde from their volume flow rate data, density compensations are performed with regressed relationship between density and (temperature, pressure and concentration). Gross error exiting in flow rate was identified during the calculation. Quality of measurements was improved and balanced data were provided as an important basis for modeling and optimization.3. The soft-sensing model of the concentration of coarse aeetaldehyde was established. Two important concepts of model verification were proposed, ratio of selection for modeling and coefficient of coincidence. The model is updated on hourly basis to compensate the mismatch continually. The whole system was implemented and was kept running for eight months. The average deviation between the predicted values and the off-line laboratory analysis results is about 1.36 percent. The model is effective and practical, and is ready for optimization use.4. Formulation and implementation of yield optimization were intensively studied. The effect of proposed RTO scheme was validated in an overburdened real chemical plant, which implies the effectiveness and practicability of the technique. RTO would make profit for aeetaldehyde production process 6,862,000 yuan RMB per year. Furthermore, the optimization problem was re-formulated with economics introduced. Some key parameters of the model and their impact on overall economics were discussed.