[en] The trichlorosilane (TCS) purification process has significant energy requirements to achieve a TCS purity of 10 N. In this study, a dividing wall column was used to improve the performance of the TCS process. A response surface methodology was applied to the design of the dividing wall column. The conventional dividing wall column and top dividing wall column have significant benefits, e.g. decreasing the operating cost and minimizing the total annual cost. Incorporating a heat pump in the top diving wall columns was also proposed to enhance the energy efficiency further. Furthermore, a column grand composite curve was used to evaluate the thermodynamic feasibility of implementing the heat pump system into DWC. The operating cost could be reduced by 83% by novel combinations of internal and external heat integration: top dividing wall columns using a top vapor recompression heat pump. A compact integrating TCS purification process was finally proposed. -- Highlights: • A compact and energy efficient TCS purification process is proposed. • Optimal design is efficiently done by response surface methodology. • CGCC is used to evaluate the thermodynamic feasibility of implementing the heat pump. • Novel combination of internal and external heat integration is proposed. • The operating cost could be reduced by 83.01%

[en] Highlights: • A compact biorefinery design was proposed for cellulosic ethanol purification. • Actual fermentation broth from lignocellulosic biomass was considered. • Process integration and intensification achieves competitive biorefinery context. • The response surface method optimizes the complex column structure effectively. • The proposed process could save up to 47.6% of total annual cost. - Abstract: Biofuels have the most potential as an alternative to fossil fuels and overcoming global warming, which has become one of the most serious environmental issues over the past few decades. As the world confronts food shortages due to an increase in world population, the development of biofuels from inedible lignocellulosic feedstock may be more sustainable in the long term. Inspired by the NREL conventional process, this paper proposes a novel heat–integrated and intensified biorefinery design for cellulosic ethanol production from lignocellulosic biomass. For the preconcentration section, heat pump assisted distillation and double–effect heat integration were evaluated, while a combination of heat–integrated technique and intensified technique, extractive dividing wall column (EDWC), was applied to enhance the process energy and cost efficiency for the purification section. A biosolvent, glycerol, which can be produced from biodiesel production, was used as the extracting solvent in an EDWC to obtain a high degree of integration in a biorefinery context. All configuration alternatives were simulated rigorously using Aspen Plus were based on the energy requirements, total annual costs (TAC), and total carbon dioxide emissions (TCE). In addition, the structure of the EDWC was optimized using the reliable response surface method, which was carried out using Minitab statistical software. The simulation results showed that the proposed heat–integrated and intensified process can save up to 47.6% and 56.9% of the TAC and TCE for the purification section, respectively, compared to the conventional purification process.

[en] Highlights: • Novel hybrid configuration is proposed for debottlenecking of side stream column. • Significant saving in operating cost could be achieved. • A DWC can increase the energy efficiency of a heat pump. • A synergetic advantage of enhancing energy efficiency and reducing capital cost. • Can be applied to both close-boiling and wide-boiling mixtures. - Abstract: Improving the energy efficiency of distillation columns and reducing the related CO_2 emissions is a part of the global effort towards greater sustainability in chemical processing industries. Furthermore, increasing the capacity, which has been a major focus of the chemical process industry, can cause an entrainment flooding or a bottleneck problem in the distillation column. This paper reports the results of a techno-economic feasibility study to retrofit and debottleneck side stream columns, as one of most popular industrial distillation columns, in order to maximize energy efficiency and column throughput by using a novel hybrid configuration – heat pump assisted dividing wall column. The heat pump technique was used to improve the energy efficiency of a dividing wall column in debottlenecking a side stream column. On the other hand, the dividing wall column was exploited to increase the performance of a heat pump while also to removing bottlenecking problems. Several industrial cases were examined to demonstrate the proposed configuration. A heat pump assisted dividing wall column was optimized using a response surface methodology. The results showed that the proposed heat pump assisted dividing wall column can remove the bottleneck problem effectively and achieve substantial energy saving and CO_2 emission reduction as well. Notably, an 83.7%, 85.9% and 61.3% reduction in operating costs could be achieved in the ethylene dichloride, acetic acid and alkanes separation processes, respectively. The proposed configuration can be applied to both close-boiling and wide-boiling mixtures, and also employed to both retrofit and grass-roots designs.

[en] Many design variables and constraints, such as operating temperature and pressure of existing batch distillation or operating temperature of existing cooling and heating media, must be verified and satisfied during design and optimization when an existing batch distillation column is utilized for new mixture. The convergence of batch distillation simulation is sensitive with the initial values of these variables. Thus, a new systematic methodology was proposed to design and optimize separation of a new mixture using an existing batch column. The systematic methodology was based on an industrial case study of dichlorodifluoromethane (R-12) reclamation from a waste refrigerant mixture. Based on a comparison of the Pxy diagram with experimental data, “REFerence fluid PROPerties” was selected as the thermodynamic model. After design and optimization using shortcut and rigorous methodologies, the existing batch distillation unit was operated to validate the proposed methodology. The experimented performance match well with the simulated results. Under the optimized operating condition, complete purification of R-12 (purity=99.5%) was achieved experimentally after 28.3 h. The advantages and disadvantages of the proposed methodology were then discussed.

[en] Highlights: • An enhanced SMR process using hydraulic turbines was proposed for improving energy efficiency. • Synergistic effects by hydraulic turbines with optimization were investigated. • The proposed SMR process reduces energy requirement up to 16.5%. • Efficient utilization of recovered energy further reduces energy requirement up to 25.7%. • The proposed hydraulic turbine based liquefaction can be extended to other natural gas liquefaction processes. The advancement in hydraulic turbine (HT) technology was exploited for energy and cost benefits in natural gas liquefaction. Replacing the conventional Joule–Thompson (JT) valve with HT has the potential to recover the work input. This research investigated the effect of replacing the JT valve with HT in the energy efficiency enhancement of a single mixed refrigerant (SMR) process. To fully take the potential benefit of the HT, the proposed SMR schemes were optimized by using a modified coordinate descent optimization method, which was implemented in Microsoft Visual Studio environment and linked to the rigorous HYSYS^® model. The results showed that the required energy of the proposed HT based SMR process could be saved up to 16.5% in comparison with the conventional SMR process using the JT valves. Utilization of the recovered energy into boosting the natural gas feed pressure could further reduce the energy requirement up to 25.7%. Exergy efficiency analysis also showed that whole exergy efficiency of the enhanced SMR process can be increased by about 11% as compared to the base case. The proposed HT based liquefaction technology can be extended to other natural gas liquefaction processes as an attractive option for enhancing the energy efficiency.

[en] Highlights: • Simple, compact and energy-efficient SMR processes were proposed. • Proposed process showed a synergetic advantage of enhancing energy efficiency. • Energy saving of 30.6% can be accomplished by a knowledge-inspired optimization. • Energy requirement is reduced significantly lowering the intercooler temperature. - Abstract: This study examined the enhancement of the single mixed refrigerant (SMR) natural gas liquefaction process. The effects of the main parameters, such as mixed refrigerant (MR) composition and operating pressures on the compression energy requirement were investigated. A process knowledge inspired decision-making method was exploited for liquefied natural gas process optimization. The results showed that the proposed optimization methodology is simple and effective in determining the optimal operating conditions and could save up to 30.6% in terms of the compressor duty compared to the base case. In addition, the proposed optimization methodology provides process understanding, which is essential to process engineers. Another benefit of the proposed methodology is that it can be applied to any MR liquefaction cycle. The use of heavier refrigerants, such as isobutane and isopentane, and the addition of a NG compressor were examined to improve the energy efficiency of the SMR process. The effect of the intercooler outlet temperature on energy saving was also considered. The synergistic effects of those modifications on improving the performance of the liquefaction process were investigated.