Heat Pump-assisted Distillation Research Articles

Optimized Water Distillation Layout for Detritiation Purpose

Tritium permeation constitutes a key issue for the future EU-DEMO, especially in the Breeding Blanket (BB) where fusion energy must be delivered to the Primary Heat Transport System (PHTS) and where tritium must be bred. Currently, the mitigation strategy of the tritium permeation from BB into primary coolant is based on the adoption of anti-permeation barriers and on the operation of the Coolant Purification System (CPS). This system must ensure a tritium removal rate from the primary coolant equal to the BB permeation rate at a target tritium-specific activity inside the PHTS. In the case of the Water-Cooled Lithium Lead (WCLL) BB, water distillation was selected as the most promising technology for the primary coolant detritiation due to its intrinsic simplicity and safety. Nevertheless, power consumption was recognized as a relevant concern. For this reason, the present work aims at investigating possibilities to reduce power consumption of the water CPS implementing Heat Pump-Assisted Distillation (HPAD) concepts. To do this, a review of the HPADs developed in the chemical industry was carried out, and the best options for the water CPS were identified based on qualitative considerations. Then, a quantitatively assessment of the best solution in terms of power consumption and tritium inventory was performed with the commercial numerical tool Aspen Plus. Finally, the Mechanical Vapor Recompression (MVR) concept was recognized as the most promising solution, ensuring a power saving of around 80% while keeping a limited tritium inventory.

Dynamics and control of electrified pressure-swing distillation for separating a maximum-boiling azeotrope featuring small pressure-induced shift

Pressure-swing distillation (PSD) is a typical thermal-driven technique for separating pressure-sensitive azeotropes. By implementing heat pump assisted distillation (HPAD) and self-heat recuperation technology (SHRT), the process can be modified as an electrical-driven one. Previous works have verified the overwhelming steady-state economic advantages of electrified PSDs over a conventional design. However, highly integrated electrified processes could jeopardize the dynamics and controllability. In light of potential dynamic control issues, a demonstrating case of a maximum-boiling acetone/chloroform azeotrope featuring a small pressure-induced shift was studied. Severe snowball effects were observed in these complicated electrified systems. To maintain process stability under throughput and composition disturbances, several robust control structures based on decentralized proportional-integral feedback controllers were developed. These control structures feature temperature controllers with no composition measurement. The results indicate that there is no conflict between the steady-state advantage and dynamic controllability. Therefore, considering the great advantages in economic and environmental aspects of electrified PSD, it is encouraged to extend process electrification measures to other distillation processes.

The effective synthesis of heat-pump assisted distillation process with multiple columns for light hydrocarbon separation

The separation of light hydrocarbons (LHCs) by conventional distillation process is highly energy intensive. In this work, a novel method was proposed to optimize heat pump assisted distillation process with multiple columns. The MINLP models were formulated in Python to determine the superstructure of the heat and work exchange networks. A genetic algorithm was utilized to find feasible solutions for HPD with minimum total annualized cost (TAC). With the optimal parameters, 36.9% of TAC was reduced after retrofitted by HP. The establishing of HPD with pumparounds was conducted at high ΔTminand it would contribute to the energy reduction of proposed HPD process. The improved optimization procedure for the DWC process was developed and a high-performance DWC-HPD process was further established with an energy reduction of 60%. MINLP models as well as improved HP/DWC optimization procedure show impressive advantages in the cost and energy reduction of the conventional distillation process.

Purification of isopropanol-butanol-ethanol (IBE) from fermentation broth: process intensification and evaluation

Biofuels from biomass have attracted great attention due to the increasingly serious environmental problems and the increasing demand for fossil fuels. Butanol is considered as a promising alternative biofuel because of its favorable properties, and it can be produced by IBE fermentation broths. Moreover, the high-purity isopropanol-ethanol (IE) mixture produced by IBE fermentation can be used as a gasoline additive. However, the IBE purification process is hindered by its low concentration and energy-intensive separation from IBE fermentation broths. In this work, a novel 6-column distillation process for IBE purification is proposed to reduce the total energy consumption (TEC) and capital cost. Furthermore, for achieving further energy savings, the double-effect distillation (DED) and heat pump assisted distillation (HPAD) technologies are used as the process intensification methods. These processes are compared in terms of energy, economic and environmental impact. The results indicate that the total annual cost (TAC), TEC and gas emissions of the IBE purification process can be reduced effectively by the three intensification processes, among them, the process intensification with HPAD (PI-HPAD) process is the best one, which can achieve 46.72%, 26.96% and 30.52% savings of TEC, TAC and CO2 emission, respectively.

Economic Analysis and Environmental Impact Assessment of Heat Pump-Assisted Distillation in a Gas Fractionation Unit

The depletion of fossil fuels and environmental pollution (e.g., greenhouse gas emissions) through the combustion of fossil fuels have stimulated studies on new technologies able to curtail the energy consumption of existing fractionation units. In this regard, heat pumps have garnered substantial attention due to their potential to improve the process energy efficiency. This study aims to provide extensive economic analysis and environmental impact assessment of the application of heat pumps under different conditions and scenarios. For this purpose, we first selected three important conditions: feed composition, plant capacity, and fuel price. Then, we performed a range of analyses to identify the major costs and environmental drivers. The economics and environmental impact of heat pump-assisted distillation was investigated and compared with those of conventional distillation.

Design and economic evaluation of energy-saving industrial distillation processes for separating close-boiling cyclohexanone-cyclohexanol mixture

In this study, several heat-integrated distillation processes are compared to separate the close-boiling cyclohexanone (CHON)-cyclohexanol (CHXA) for improving energy efficiency. A 4-column scheme, including two light ends columns in DRP (distillation with recycle process), a CHON column and a CHXA column, is introduced as the prototype scheme. To make improvement, light and heavy split DRP – are compared for energy optimization upon the prototype. The light split DRP turns out to be superior and thus used for subsequent steps. Four heat-integrated schemes including double-effect distillation (DED), heat pump assisted distillation (HPAD), DED plus HPAD (DEHP) and double HPAD (DHPAD) are sequentially suggested and evaluated based on total annualized cost (TAC). The results show TAC reductions from the prototype of 32.2%, 23.6%, 29.2% and 10.8% for DED, HPAD, DEHP and DHPAD, respectively. The DED scheme requires the lowest TAC due to the 48.4% operating cost and 8% capital cost saving, whereas the DEHP scheme has the lowest 56.3% operating cost reduction with 11.1% more capital investment. The line of thinking in this work will benefit in other close-boiling systems for higher energetic efficiency and economic profit.

Heat-pump assisted distillation versus double-effect distillation for bioethanol recovery followed by pressure swing adsorption for bioethanol dehydration

Abstract Bioethanol recovery (i.e., pre-concentration from 5 to 10 wt.% ethanol to near azeotrope composition) from the fermentation broth requires significantly more energy compared to bioethanol dehydration from near azeotrope composition to >99.5 wt.% ethanol. The present article proposes and evaluates two different alternatives, namely, double-effect distillation (DED) and heat-pump assisted distillation (HPAD) as opposed to simple distillation for bioethanol recovery followed by dehydration using pressure-swing adsorption (PSA). Preliminary design reveals that HPAD-PSA process outperforms DED-PSA process resulting in 19% savings in total annual cost. Multi-objective optimization is hence performed for HPAD-PSA process, and the obtained Pareto-optimal solutions for minimizing fixed capital investment and annual operating cost are presented and discussed. Compared to the simple distillation followed by PSA process, HPAD-PSA process reduces specific energy consumption (SEC) by 38% to 3.2 MJ-fuel/kg of bioethanol. Further, compared with other, recent bioethanol separation processes, HPAD-PSA process results in 35–64% lesser SEC.

Evaluation of the performance of heat pump-assisted distillation of an ethanol–water mixture

ABSTRACTThe process of separation of an ethanol–water mixture was simulated. A heat pump system was then implemented on the distillation column with the highest energy requirements in the process. Complete elimination of hot and cold utilities of the pretreatment column was obtained through an improved system by application of a heat pump at a compressor work of 406.6 kW. Installation of the heat pump system on the pretreatment column of the system results in a reduction of 10.7% of annual operating costs and 6.6% of the total annual costs (TAC). However, the capital costs of the process will enhance by 22.6%.

Selecting suitable energy-saving distillation schemes: Making quick decisions

More and more frequently, chemical engineers need to make quick decisions when selecting suitable energy-saving distillation schemes, for example, choosing between double effect and heat pump. Having endured this situation for years, the authors try to introduce, in this paper, shortcut methods to help choose between heat pump-assisted distillation and multi-effect distillation by evaluating energy efficiency in comparison with a conventional distillation column without any heat integration. To verify the accuracy of the shortcut methods, five binary systems with different relative volatilities, namely, methyltrichlorosilane-dimethyldichlorosilane, 2-methylbutane-n-pentane, benzene-toluene, methanol-water and cyclohexane-cyclohexanol, are studied using the shortcut methods with the aid of rigorous simulations. The energy efficiency results are presented in terms of standard oil versus atmospheric relative volatilities for both double-effect distillation and mechanical vapor recompression assisted distillation. Systems with lower relative volatilities perform best with the heat pump option, while systems with higher relative volatilities perform better with heat integration. The aim of the shortcut methods—to simplify and speed up the decision using only easily accessible data such as relative volatility and utility prices—is achieved.

Retrofitting Options for Natural Gas Liquid (NGL) Fractionation Trains Using the Concept of Single Column Development

Heat pump assisted distillation (HPAD) system and self-heat recuperation technology (SHRT) have been developed as a result of intensive research to reduce energy consumption of a conventional distillation system. To determine a suitable system for natural gas liquid (NGL) fractionation trains, rigorous analysis and comparative study of several HPAD and SHRT options for the retrofitting of a single column were studied in the present work. The retrofit options considered were vapor compression (VC), mechanical vapor recompression (MVR), thermal vapor recompression (TVR), bottom flashing (BF), side heat exchanger (SHE), intermediate heating and cooling (IHC), self-heat recuperative (SHR) and modified self-heat recuperative (MSHR) distillation. A depropanizer column commonly used in typical NGL plant was selected as a case study. Aspen HYSYS V7.3 was initially used to simulate the eight selected retrofit designs under common sets of criteria. The data from the simulation was then analyzed to determine the best design in term of energy cost reduction. The analysis shows that the MVR gives the highest energy cost reduction of 68.11% as compared to that of the base case (BC) conventional column. It is followed by VC (66.65%), MSHR (64.02%), BF (62.88%), SHR (55.85%), SHE (54.23%), IHC (39.54%), and TVR (12.41%).

Optimal design of advanced distillation configuration for enhanced energy efficiency of waste solvent recovery process in semiconductor industry

The semiconductor industry is one of the largest industries in the world. On the other hand, the huge amount of solvent used in the industry results in high production cost and potential environmental damage because most of the valuable chemicals discharged from the process are incinerated at high temperatures. A distillation process is used to recover waste solvent, reduce the production-related costs and protect the environment from the semiconductor industrial waste. Therefore, in this study, a distillation process was used to recover the valuable chemicals from semiconductor industry discharge, which otherwise would have been lost to the environment. The conventional sequence of distillation columns, which was optimized using the Box and sequential quadratic programming method for minimum energy objectives, was used. The energy demands of a distillation problem may have a substantial influence on the profitability of a process. A thermally coupled distillation and heat pump-assisted distillation sequence was implemented to further improve the distillation performance. Finally, a comparison was made between the conventional and advanced distillation sequences, and the optimal conditions for enhancing recovery were determined. The proposed advanced distillation configuration achieved a significant energy saving of 40.5% compared to the conventional column sequence.

Bubble point measurement and high pressure distillation column design for the environmentally benign separation of zirconium from hafnium for nuclear power reactor

We examined the feasible separation of ZrCl4 and HfCl4 through high pressure distillation as environmentally benign separation for structural material of nuclear power reactor. The bubble point pressures of ZrCl4 and HfCl4 mixtures were determined experimentally by using an invariable volume equilibrium cell at high pressure and temperature condition range of 2.3–5.6 MPa and 440–490 °C. The experimental bubble point pressure data were correlated with Peng-Robinson equation of state with a good agreement. Based on the vapor-liquid equilibrium properties evaluated from the experimental data, the feasibility of high pressure distillation process for the separation of ZrCl4 and HfCl4 was investigated with its main design condition through rigorous simulation using a commercial process simulator, ASPEN Hysys. An enhanced distillation configuration was also proposed to improve energy efficiency in the distillation process. The result showed that a heat-pump assisted distillation with a partial bottom flash could be a promising option for commercial separation of ZrCl4 and HfCl4 by taking into account of both energy and environmental advantages.

Advances in heat pump assisted distillation column: A review

Progressive depletion of conventional fossil fuels with increasing energy demand and federal laws on environmental emissions have stimulated intensive research in improving energy efficiency of the existing fractionation units. In this light, the heat pump assisted distillation (HPAD) scheme has emerged as an attractive separation technology with great potential for energy saving. This paper aims at providing a state-of-the-art assessment of the research work carried out so far on heat pumping systems and identifies future challenges in this respect. At first, the HPAD technology is introduced with its past progresses that have centered upon column configuration, modeling, design and optimization, economic feasibility and experimental verification for steady state operation. Then the focus is turned to review the progress of a few emerging heat integration approaches that leads to motivate the researchers for further advancement of the HPAD scheme. Presenting the recently developed hybrid HPAD based heat integrated distillation configurations, the feasibility of heat pumping in batch processing is discussed. Finally the work highlights the opportunities and future challenges of the potential methodology.