Heat-integrated pressure-swing distillation process for separation of the maximum-boiling azeotrope diethylamine and methanol

Effects of Energy Intensification of Pressure-Swing Distillation on Energy Consumption and Controllability

The aim of process integration is the efficient use of energy and natural resources. However, process integration can result in a more precise process operation, that is, it influences controllability. Pressure-swing distillation processes are designed for the separation of azeotropic mixtures, but their inherent heat integration option can be utilized to significantly reduce their energy consumption. One maximum-boiling and three minimum-boiling azeotropes are considered to study and compare the nonintegrated and integrated alternatives with the tool of mathematical modeling where ASPEN Plus and MATLAB software are used. The results show that the heat-integrated alternatives result in 32-45% energy savings that are proportional to the emission reduction and the consumption of natural resources. As far as the operability is concerned, the heat-integrated alternatives show worse controllability features than the nonintegrated base case. This can be due to the loss of one controllability degree of freedom. This recommends using more sophisticated control structures for the sake of safe operation if process integration is applied.

Design and Control of Pressure-Swing Heat Integration Distillation for the Trichlorosilane Purification Process

Trichlorosilane (TCS) is a crucial intermediate product in the polysilicon manufacturing process, and its purification consumes a significant amount of energy. The design and control of the TCS heat integration pressure-swing distillation (HIPSD) process was investigated using Aspen Plus V8.4 and Aspen dynamics in this study. Three partial processes and one full HIPSD process were investigated by adjusting the operating conditions and rationally configuring the material flow. Compared with the conventional distillation process, the partial and full HIPSD can reduce total annual cost by 15.75 and 27.39%, respectively. The aforementioned process was controlled robustly by adding the ratio of reboiler heat duty to feed (Q _R/F) feedforward control structure and the ratio of recycle to feed (F _REC/F) control structure. In addition, the performance of the control structure was evaluated by introducing ±10% disturbances of the feed flowrate and composition. To compare the performance of the control structure, the integral squared error value is combined with the dynamic response curve. The full HIPSD scheme can resist ±10% disturbances of flow and composition with the best economic performance. This study has certain reference significance for the distillation process and control strategy design of TCS in the polysilicon manufacturing process.

Study on the Degradation of Sodium Diethyldithiocarbamate (DDTC) in Artificially Prepared Beneficiation Wastewater with Sodium Hypochlorite

The degradation of DDTC in beneficiation wastewater has become an increasingly concerned issue due to the serious effects on the environment. In this study, the degradation characteristics of DDTC in artificially prepared beneficiation wastewater were investigated by adding sodium hypochlorite as an oxidant, and the influences of different degradation conditions on removal efficiency of DDTC were analyzed systematically. The results indicated that the degradation rate of DDTC without sodium hypochlorite added can reach 88.4% in a stewing time of 6 h. When the dosage of sodium hypochlorite was 400 mg·L−1, the degradation rate of DDTC can reach 91.28% for 1 min reaction time under the natural condition of pH value 5.98 and reaction temperature 25°C. The DDTC in the wastewater was firstly degraded into carbon disulfide and diethylamine, and then carbon disulfide was further degraded into CO2, S, or SO42−, while diethylamine was degraded into N2 and CO2. The research results can provide a technical basis for the treatment of beneficiation wastewater containing DDTC.