Energy-Saving Optimization And Control Of Dilute Acetic Acid Dehydration Process

Acetic acid (HAc) serves as a kind of important synthetic raw materials and organic solvent which has been widely used in chemical industry. To increase product utilization, it is of great value to recycle the HAc from its industrial wastewater. In this study, recovery of 10w% concentration HAc wastewater is researched. To reduce energy consumption in dilute HAc dehydration and purification, basing on the idea of withholding concentration, raw materials is extracted and concentrated firstly, then it is sent to distillation column for dehydration. The extraction agent and entrainer is same, so an extraction agent recycling process is reduced. Extraction and distillation process mode is established to study energy saving strategy via Aspen Plus and Aspen Dynamics.Mixture of N-butyl acetate (NBA) and butyl alcohol (BuOH) is used as extracting agent and entrainer. On the basis of extraction and azeotropic distillation combined technology, the proportion of BuOH in extracting agent and entrainer and the proportion of dilute HAc feed which is sent to extraction column are optimized. It shows that 5.5% BuOH and 23% HAc feed can achieve an optimal balance between energy consumption and design requirements. Guthrie simplified equation is then used for economy verification. Compared with traditional distillation, it could save 14.68% equipment investment and 22% operating costs. Furthermore, dynamic model is built where appropriate tray position is chosen for dual temperature control. According to disturbance analysis, the control strategy that regulates the ratio of reboiler duty Q and feed rate F, and the ratio of aqueous phase reflux dual temperature is superior among the three control schemes provided.Methyl tert-butyl ether (MTBE) is employed as extracting agent and entrainer. The feasibility of separation is analyzed based on physical properties and residual curve. Extraction and distillation combined technology model of dilute HAc feed total concentration is then established. Through optimizing the operating conditions of the extraction column and HAc dehydration distillation column, nearly 68.66% equipment investment and over 80% operating costs can be saved, compared with traditional distillation. In the meantime, HAc mass fraction at the bottom of dehydration column is up to 99%. Finally, a stable control scheme is designed so that the system could react quickly under feed flow and component disturbances.