Potential for Significant Energy-Saving via Hybrid Extraction–Distillation System: Design and Control of Separation Process for <i>n</i>‑Propanol Dehydration

The hybrid extraction–distillation separation system is a process combining liquid–liquid extraction and also distillation. This hybrid system can be viewed as a derivative of the heterogeneous azeotropic distillation method. In this work, the potential for significant energy-saving via this hybrid process is demonstrated with both conceptual illustration and a case study of <i>n</i>-propanol dehydration. Diisopropyl ether (DIPE) is selected as the extraction solvent considering its favorable properties of density, heat of vaporization, and lower toxicity. Since the solvent flow rate is the most important design degree-of-freedom in this process that influences overall energy consumption, an iterative optimization procedure is conducted to minimize total annual cost. Furthermore, a novel control strategy is proposed on the basis of closed-loop and open-loop sensitivity tests. Here, an adjustable solvent flow rate during dynamic control allows steady-state operation at the optimal condition. Dynamic simulation results show that both <i>n</i>-propanol and water products can still be maintained at high purities despite large variations in feed flow rate and feed composition disturbances

Design and Economic Evaluation of a Coal-Based Polygeneration Process To Coproduce Synthetic Natural Gas and Ammonia

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. <i>Ind. Eng. Chem. Res.</i> <b>2015</b>, <i>54</i>, 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

Design and Economic Evaluation of a Coal-to-Synthetic Natural Gas Process

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

Potential for Significant Energy-Saving via Hybrid Extraction–Distillation System: Design and Control of Separation Process for <i>n</i>‑Propanol Dehydration

The hybrid extraction–distillation separation system is a process combining liquid–liquid extraction and also distillation. This hybrid system can be viewed as a derivative of the heterogeneous azeotropic distillation method. In this work, the potential for significant energy-saving via this hybrid process is demonstrated with both conceptual illustration and a case study of <i>n</i>-propanol dehydration. Diisopropyl ether (DIPE) is selected as the extraction solvent considering its favorable properties of density, heat of vaporization, and lower toxicity. Since the solvent flow rate is the most important design degree-of-freedom in this process that influences overall energy consumption, an iterative optimization procedure is conducted to minimize total annual cost. Furthermore, a novel control strategy is proposed on the basis of closed-loop and open-loop sensitivity tests. Here, an adjustable solvent flow rate during dynamic control allows steady-state operation at the optimal condition. Dynamic simulation results show that both <i>n</i>-propanol and water products can still be maintained at high purities despite large variations in feed flow rate and feed composition disturbances

Assessment on CO₂ Utilization through Rigorous Simulation: Converting CO₂ to Dimethyl Carbonate

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

Fuzzy-Logic-Based Supervisor of Insulin Bolus Delivery for Patients with Type 1 Diabetes Mellitus

In this article, a fuzzy-logic-based supervisor of insulin bolus delivery for type 1 diabetes mellitus (T1DM) is proposed. The proposed supervisor incorporates expert knowledge into three phases, including recall, inference, and learning phases. A recently developed and well-acknowledged meal simulation model of the glucose–insulin system for T1DM was employed to create virtual subjects for testing. Data from virtual subjects were used to identify an intermediate physiological model, and then our proposed supervisor was synthesized based on this intermediate model. The key features of this fuzzy-logic-based supervisor are that the implementation does not need an online model and it can gradually be updated meal-by-meal. In addition, only two blood glucose measurements between each meal are needed for updating the insulin bolus delivery. The simulation results show that effective and robust glycemic control performance can be achieved. This methodology can be widely applied to patients with continuous subcutaneous insulin infusion (CSII) or multiple daily injections (MDI)

Critical Assessment of Using an Ionic Liquid as Entrainer via Extractive Distillation

Ionic liquids (ILs) have received much attention in the last two decades. One of the important applications is to use this relatively new class of compounds for the separation of azeotropic mixtures via extractive distillation. In this paper, overall extractive distillation processes of two azeotropic separation systems using a favorable ionic liquid as entrainer are rigorously developed. The optimized design flowsheets are compared with the conventional processes using an industrial entrainer. The two ionic liquid extractive distillation systems include separating acetone and methanol using 1,3-dimethylimidazolium dimethylphosphate ([MMIM]­[DMP]) as entrainer and another system of separating isopropyl alcohol and water using 1-ethyl-3-methylimidazolium acetate ([EMIM]­[OAC]) as entrainer. The potential drawbacks of using an ionic liquid in the extractive distillation systems are given in the paper. It is found that the degradation temperature and high normal boiling point temperature of the ionic liquids in these two systems require the IL processes to use high vacuum operating conditions, thus making them only economically comparable to the conventional processes

Energy-Saving Optimal Design and Effective Control of Heat Integration-Extractive Dividing Wall Column for Separating Heterogeneous Mixture Methanol/Toluene/Water with Multiazeotropes

To the best of our knowledge, very few efforts have been investigated for separating heterogeneous mixtures methanol/toluene/water with multiazeotropes using extractive dividing-wall column (EDWC). In this work, we propose a systematic approach for the energy-efficient EDWC to achieve less capital cost and operating cost in separating heterogeneous multiazeotropes mixtures, which involves thermodynamic feasible insights via residue curve maps to find separation constraints, global optimization based on a proposed CPOM model, and a dynamic control through Aspen Dynamics simulator to better maintain product purities. An energy-saving EDWC with heat integration (HI-EDWC) flowsheet is then proposed to achieve the minimum total annualized cost (TAC). The computational results show that the TAC of the proposed HI-EDWC is significantly reduced by 15.14% compared with the optimal double-column extractive distillation with an additional decanter. Furthermore, an effective control strategy CS3 with a fixed reboiler duty-to-feed ratio and temperature/(S/F) cascade is proposed to better handle the methanol, toluene, and water product purities than basic control structures CS1 and CS2 while feed flow rate and composition disturbances are introduced in the proposed HI-EDWC process

Energy-Efficient Extraction–Distillation Process for Separating Diluted Acetonitrile–Water Mixture: Rigorous Design with Experimental Verification from Ternary Liquid–Liquid Equilibrium Data

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 <i>n</i>-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

Design and Control of the Glycerol Tertiary Butyl Ethers Process for the Utilization of a Renewable Resource

In this paper, the design and control of an improved process for the manufacture of a fuel additive (glycerol tertiary butyl ethers, GTBE) from glycerol and isobutylene is developed. The improved process redirects one recycle stream, uses a stripping column instead of a flash tank to recover isobutylene, and uses a rectifying column instead of a distillation column to purify the product. Economic analysis shows that the improved process has a 22% lower total annual cost (TAC) than the best known process published in the literature. Significant increases in the selectivity of the overall process from 84.7% to 99.3% can also be realized by comparing the optimized improved design versus the original design. Dynamic simulations were also conducted and indicated that stringent product specification can be met with a simple decentralized feedback control structure despite impurities in the feed streams and also changes in the throughput