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The steady state design and economic evaluation for coal to synthetic natural gas (SNG) process is rigorously studied, and this study could give a baseline for design and analysis for SNG production in Taiwan or other countries relying on importation of an energy source. SNG is a product that holds very similar composition and heat value to typical natural gas, and can be used as a replacement in industrial and home usages. Natural gas is an important energy source in Taiwan, with increasing demand year by year. Because over 99% of our energy sources is imported in Taiwan, and because of the advantages of coal over natural gas (lower importation price, great abundance, easier transportation and storage, etc.), the process that converts coal into SNG is expected to benefit Taiwan if the related technology is successfully established. The whole process is divided into several parts, including air separation unit (ASU), gasification, the syngas treating section (water gas-shift reaction, syngas cooling, and acid gas removal), methanation reaction section, and electricity production block from upstream to downstream. The overall energy conversion efficiency for the plant is 60.38%, with the SNG production cost to be 10.837 (USD/GJ), thus this process will be economically and practically attractive.

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This paper intends to discuss the economical performances and CO2 reduction potential of two CO2-based dimethyl carbonate (DMC) production processes through rigorous process simulation. One of them is the direct production process with addition of butylene oxide (BO) as dehydrating agent (DIR-BO porocess), while the other is the indirect production process through ethylene carbonate (EC) as an intermediate (IND-EC process). Both processes are systematically optimized and heat-integrated. From economical evaluation, the IND-EC process exhibits economical attractiveness, while the DIR-BO process does not. We suggest that once the reaction rate of the DIR-BO process can be improved, the overall economic performance of the direct process can be much better. From the aspect of CO2 reduction, the net CO2 emissions throughout both processes are calculated. We found that DIR-EO process is largely carbon positive, with CO2 emission of 2.242 (kg CO2/kg DMC), yet for the IND-EC process, it is near carbon neutral, with CO2 emission of 0.049 (kg CO2/kg DMC). Thus, from the aspect of achieving CO2 reduction, converting it into DMC provides limited benefits.

Cyclohexanol is an important precursor in synthesizing intermediates of Nylons and also plasticizers. In this paper, a plantwide reactive-distillation process for the production of cyclohexanol by direct hydration of cyclohexene with water has been studied. Design with excess water is needed to economically increase conversion of cyclohexene to 99.9%. The optimal design of the proposed flowsheet also makes use of the natural liquid–liquid splitting of the binary cyclohexanol–water azeotrope. Realistic fresh cyclohexene feed with impurity of cyclohexane was also considered. This inert is designed to leave the system in the organic outlet stream of a decanter on top of the reactive-distillation column. The reboiler duty requirement of the proposed design flowsheet is compared with existing processes in open literature. It is found that significant energy savings can be realized by using this design.

In this paper, an energy-efficient extraction−distillation process to separate diluted azeotropic acetonitrile−water mixtures is newly developed. Compared with the conventional azeotropic separation methods (i.e., extractive distillation), the potential dominant benefit of this proposed method is that the main separation task can be achieved by an extraction column without needing reboiler duty. In this work, an efficient solvent of n-propyl chloride is proposed to extract the organic compound into the extract phase and to let water remain in the raffinate phase. Ternary liquid−liquid equilibrium experiments are also conducted to verify the separation performance in the extraction column and decanter of the proposed process. It is found that significant savings of 40.3% in steam cost and 34.7% in total annual cost can be obtained by the proposed separation method as compared to that of a three-column extractive distillation system published in open literature.

The steady-state design and economic evaluation of a polygeneration (POLYGEN) process to coproduce synthetic natural gas (SNG) and ammonia are studied in this work. POLYGEN has been a widely studied topic recently, in which several products could be produced parallel at the same time. One of the two products in this study, SNG, has a composition and heat value very similar to those of typical natural gas, and can be used as a replacement in industrial and home usages. Another product, ammonia, is one of the most important inorganic chemicals in the world, and could be used as the precursor of various kinds of chemicals, as fertilizers, or as a cleaning agent. In the POLYGEN process, the relative production rates for different chemicals could be adjusted on the basis of different market demands, daily usages, and also changing political strategies. In our previous study (Yu, B. Y.; Chien, I. L. Design and Economical Evaluation of a Coal-to-Synthetic Natural Gas Process. Ind. Eng. Chem. Res. 2015, 54, 2339–2352), we illustrated that the SNG production price is lower than the liquefied natural gas importation price in Taiwan. The SNG production price is 10.837 USD/GJ (USD = U.S. dollars) in an SNG-only plant. With the POLYGEN process to coproduce SNG and ammonia, the SNG production cost could become even lower. If 20% of the syngas is used to produce ammonia, the SNG production price will drop to 9.365 USD/GJ, and if 40% is used for ammonia production, the SNG production price will drop further to 7.063 USD/GJ. Thus, although the POLYGEN process leads to an increasing total capital investment, it has positive influences from economic aspects. Besides, the flexibility of shifting the production rate of SNG or ammonia makes it possible to adapt to changes in the market demand.

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