Mechanical Vapor Recompression Research Articles

Optimization strategies for produced water networks with integrated desalination facilities

Optimal management and desalination of produced water is a major challenge for U.S. oil and gas development. Integrating rigorous desalination models into multi-period produced water network optimization problems presents several hurdles, which need to be tackled using advanced optimization strategies. In this work, a novel multi-period produced water network formulation with separate solid and liquid flows is introduced to avoid singularities at zero flows. Rigorous steady state desalination models based on mechanical vapor recompression are embedded at the desalination sites in the network model. An integrated optimization formulation is developed to co-optimize the design of desalination units along with the operation of the network. Furthermore, a more robust approach based on the trust region filter method is developed to efficiently integrate complex desalination models into the multi-period planning problem. Both optimization approaches are demonstrated on a produced water network from the PARETO library (Drouven et al., 2022) using thermal desalination units. Our results show that while the TRF and integrated approaches have comparable solve times, the TRF approach has better performance reliability in terms of solver convergence. Furthermore, the optimal solution obtained by embedding rigorous models into the network is significantly different than when desalination costs are approximated using simple cost models, which motivates further research in this field.

Fully electrified heat pump assisted distillation process by flash vapour circulation

In industrial processes there are instances where heat pump assisted distillation falls short of full electrification, necessitating an auxiliary reboiler. To solve this limiting issue, this short communication proposes a new method using flash vapour circulation (FVC) to recuperate the waste heat within the heat pump cycle. This method incorporates a flash drum after the throttling valve to generate flash vapour. Rather than employing an auxiliary cooler for condensing the mixed vapour-liquid in a conventional heat pump system, the produced flash vapour is circulated back to the compressor inlet to enhance the recycled heat in the reboiler. With proper energy match, this approach has the potential to realise full electrification of distillation. The distillation of methanol/water serves as an illustrative case study, showcasing the viability of FVC which allows additional 22% energy savings, as compared to mechanical vapour recompression. Yet, this strategy may not be advantageous if the waste heat is already maximally utilised in preheating both the compressor and column inlet feed. The separation of tetrahydrofuran/water is used as case study to demonstrate the constraints of this approach.

Evaluation of mechanical vapor recompression and easy multi-effect desalination systems in different climate conditions-sensitivity and 7E analysis

Evaporative desalination systems, such as Multi-Effect Desalination (MED) and Mechanical Vapor Recompression (MVR), play important roles in addressing this challenge. Although large-scale desalination systems possess limitations in catering to the water demands of remote regions and islands and entail the cost of water transportation to residential areas, it is imperative to concentrate on studying the feasibility of employing centralized evaporative water production systems. Firstly, in this study, the initial focus is on conducting energy and exergy analyses of MVR and Easy MED systems, with a goal of enhancing knowledge about the energy consumption, exergy destruction and exergetic efficiency of these systems. Secondly, an economic analysis is undertaken to assess the feasibility of deploying these systems in various global regions. The analysis takes into account different geographical and techno-economic conditions, such as sea water temperature, interest rates, and electricity costs. This investigation also aims to explore variations in Annual Operative Cost (AOC), Total Annual Cost (TAC) and the cost of fresh water across these diverse regions. Thirdly, a sensitivity analysis is performed for the economic assessment of MVR and Easy MED systems. Lastly, exergoeconomic, environmental, enviroeconomic and exergoenvironmental analyses are conducted for both of these systems. The results show that the exergy efficiency of the Easy MED system surpasses that of the MVR, whereby the exergy destruction for Easy MED and MVR are recorded to be 5460 W and 6360 W respectiveyl. In addition to this, the MVR system demonstrated a higher TAC across all cities. The freshwater production cost of the Easy MED system was less expensive than of the MVR system. Perth was the most cost-effective city, with freshwater costs of 6.8 €/m3 and 11.91 €/m3 for MVR and Easy MED systems, respectively. Further to this, sensitivity analysis revealed that both systems are sensitive to fluctuations in electricity costs and seawater temperatures. The MVR system incurred higher fuel, product, and exergy destruction costs. However, the MVR system also exhibited greater environmental friendliness due to its lower emission of pollution gases.

Simulation of landfill leachate treatment systems involving self-designed disk tube reverse osmosis (DTRO) model integrated with mechanical vapor recompression (MVR)

Four landfill leachate treatment systems involving self-designed disk tube reverse osmosis (DTRO) module integrated with mechanical vapor recompression (MVR) were established in Aspen Plus. To assess the treatment efficiency and the economic feasibility of landfill leachate treatment techniques, simulation of leachate treatment by four systems were conducted, and the corresponding recovery rate Y, removal rate Rt, energy consumption and operating cost were obtained. Results indicate that for the two-stage DTRO system, the optimal operational pressures in compliance with emission standards are 5.6 MPa in the first stage and 3.5 MPa in the second stage. Adding an MVR system to further treat the membrane concentrate (MC) can greatly reduce the pollutant recharge and the energy consumption of the DTRO system. When Y in MVR is not strictly required, the single-stage MVR system is the most energy-saving one. When a high Y (≥80 %) is required, the series double-stage MVR system affords the highest energy-efficiency, offering a 3.14 % lower operating cost, a 3.27 % lower unit COD removal cost, and a 7.29 % lower unit water production cost as compared to the single-stage MVR system.

Joint Modeling and Operational Optimization of a Reverse Osmosis-Mechanical Vapor Recompression System for Coal-Fired Power Plant Wastewater.

The operation of coal-fired power plants generates a large amount of wastewater. With the issuance of increasingly strict drainage standards, the cost of wastewater treatment is increasing, and the need to reduce the cost of wastewater treatment is becoming increasingly urgent. Thus, based on the principles of reverse osmosis (RO) and mechanical vapor recompression (MVR) in wastewater treatment, the operational optimization of an RO-MVR joint system was studied in this work with the consideration of reducing the operating costs of wastewater treatment under given operational conditions. Firstly, based on the basic principles of RO and MVR, corresponding mechanism models were established and their accuracy was verified. Then, an economic model of the RO-MVR joint system was established, with the goal of minimizing the water production unit price and daily operating costs of the joint system for optimization analysis. Finally, we analyzed the cost and water production performance of the RO-MVR joint system before and after optimization under different operating conditions. The results show that this optimization based on the RO-MVR joint system will reduce the unit price of water production to 3.16 CNY/m3, with the daily operating costs being decreased by 22% compared to before optimization. This result helps to reduce the cost of zero-discharge wastewater treatment in coal-fired power plants.

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.

Model Based Optimization of Energy Consumption in Milk Evaporators

This work explores five falling film evaporator (FFE) simulation approaches combined with energy consumption minimization strategies, namely Mechanical Vapor Recompression and Thermal Vapor Recompression (MVR and TVR, respectively). Global system analysis and advanced dynamic optimization strategies are then investigated to minimize steam consumption, the cost of steam, and the total annualized cost and to maximize product yield. The results indicate that higher TVR discharge pressures, or MVR compression ratios, along with higher feed temperatures, enhance evaporation but increase operational costs. The most economical option includes three evaporator effects with TVR to achieve 50% product dry mass content. However, for a 35% dry mass content, MVR becomes cost-effective with an 11% reduction in unit electricity prices or a simultaneous 7% drop in electricity prices and a 5% increase in gas-based steam prices. Furthermore, switching from milk powder production to milk concentrates leads to an annual cost reduction ranging from 10.8 to 44%. Additionally, a forecasted 20% (or more) reduction in biomass-based steam cost can lead to lower annual expenditure compared with the nominal NG-based steam case. Regarding the total annualized cost, for a new plant design, optimization strategies lead to a 9–45% reduction in the total cost depending on the case under consideration.

Advanced purification of isopropanol and acetone from syngas fermentation

AbstractBACKGROUNDIsopropanol and acetone production by syngas fermentation is a promising alternative to conventional fossil carbon‐dependent production. However, this alternative technology has not yet been scaled up to an industrial level owing to the relatively low product concentrations (about 5 wt% in total). This original research aims to develop cost‐effective and energy‐efficient processes for the recovery of isopropanol and acetone from highly dilute fermentation broth (>94 wt% water) for large‐scale production (about 100 ktIPA+AC y−1).RESULTSVacuum distillation and pass‐through distillation enhanced with heat pumps or multi‐effect distillation were efficiently coupled with regular atmospheric distillation and extractive distillation in several innovative intensified downstream processes. Over 99.2% of isopropanol and 100% of acetone were recovered as high‐purity end‐products (>99.8 wt%). Advanced heat pumping (mechanical vapor recompression) and heat integration techniques were implemented to decrease total annual costs (0.109–0.137 USD kgIPA+AC−1), reduce energy requirements (1.348–2.043 kWth h kgIPA+AC−1) and lower CO2 emissions (0.067–0.191 kgCO2 kgIPA+AC−1), resulting in highly competitive recovery processes.CONCLUSIONThe proposed three novel isopropanol and acetone recovery processes from dilute broth significantly contribute to the expansion of sustainable industrial fermentation. Furthermore, this original research is the first one to develop novel pass‐through distillation technology for the complex isopropanol–acetone–water system. All the designed processes are highly economically competitive and environmentally viable. In addition to recovering efficiently both isopropanol and acetone, the designed downstream processes offer the possibility to enhance the fermentation process by recycling all the present microorganisms and reducing fresh‐water requirements. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Experimental investigation on the hybrid system of mechanical vapor recompression and hollow fiber vacuum membrane distillation applied for wastewater treatment

In order to achieve zero discharge and resource utilization of industrial high salt wastewater, a hybrid system of mechanical vapor recompression (MVR) and hollow fiber vacuum membrane distillation (HFVMD) was constructed, and several experiments of air tightness, single working condition and multiple working conditions were carried out with ammonium chloride solution as feed, then thermal economic performance were evaluated via a single factor analysis method. The obtained results showed that the system had excellent airtightness to ensure normal evaporation experiment, and high separation efficiency of 99.9% and lower evaporation energy consumption to achieve high efficient separation by combining the advantages of the hydrophobic membrane evaporation and latent heat recovery in view of MVR and HFVMD technologies. Furthermore, increasing feed temperature and feed flow rate increased evaporation rate and decreased evaporation energy consumption, while increasing feed concentration decreased evaporation rate and increased evaporation energy consumption. Finally, the single factor analysis indicated that total investment cost, annual operation cost and annual evaporation capacity were the main factors while environmental cost and equipment service life were the secondary factors which affected the specific evaporation cost. The above research provides theoretical and experimental bases for the development of the proposed system in the future.

Techno-economic and environmental analysis of high temperature heat pumps integration into industrial processes: the ammonia plant and pulp mill cases

Heat pumps will play an important role in improving the performance of the industrial processes aiming to decarbonize their heating requirements. Yet, defining the best operating conditions of those devices may be a challenging task, as they are embedded in larger energy conversion systems and in direct competition with fired and electric heaters and other waste heat recovery systems. The costs of the energy inputs also influence the selection of either a heat pump or a gas boiler, which affects the overall efficiency and the incremental cost of the final solution. Thus, a systematic analysis must be applied in order to determine the best option to supply the heating requirement, without considerably impacting the operational feasibility of the overall plant. In this work, the base-case performance of two industrial applications with intensive heating demand, namely, the solvent regeneration process of a carbon capture unit and the black liquor concentration process of a kraft pulp mill, are compared to that of the scenarios in which a high temperature heat pump or a mechanical vapor recompression unit are integrated, aiming to reduce the energy consumption and the environmental impact. The benefits of the integration of a heat pump or a mechanical vapor recompression unit over a conventional reboiler and a multiple effect evaporation system are discussed in the light of thermodynamic, economic and environmental indicators. As a result, the alternative approaches remain competitive vis-à-vis the conventional solutions in terms of energy consumption and operating costs. In addition, the emissions associated to the heating applications could be reduced by 45% if a high temperature heat pump is integrated. The optimized solution using a heat pump has an overall exergy efficiency 9% higher compared to the typical configuration of the ammonia plant. In pulp mills, the integration of mechanical vapor recompression systems slightly affects the performance compared to the conventional scenario with a multiple effect evaporation system.

Simulation and modification of an Ethane-Ethylene separation Unit using vapor recompression heat Pump: Energy, Exergy, and economic analyses

This paper presents a comprehensive analysis involving simulation and thermo-economic evaluation of thermal integration technology, specifically the vapor recompression method, applied to an existing ethane-ethylene distillation process. The study commences with the simulation of the current process, revealing a favorable level of accuracy as evidenced by the strong agreement between simulation outcomes and real plant data. The energy analysis highlights key parameters, with consumption rates of 0.4 kg of refrigerant per kg of vapor in the condenser and 0.743 kg of heating fluid per kg of liquid in the reboiler. Moving to the economic analysis, the total investment cost for the existing process is estimated at 16,925,333 USD. However, a noteworthy concern is the high refrigerant consumption in the condenser, leading to elevated operational costs within ethylene production facilities. Consequently, this study focuses on reducing refrigerant consumption and enhancing the thermodynamic efficiency of the ethane-ethylene distillation column. Simulation results for the proposed process demonstrate an investment cost of 968,837 USD, marking a 5.72 % reduction compared to the current process. The optimization process, driven by sensitivity analysis, determines the optimal outlet fluid pressure for the compressor, setting it at 3730 kPa. Under this optimized condition, refrigerant consumption for condensing the overhead vapors within the distillation column drops by a significant 34.29 % compared to the base case. From an energy perspective, the optimal Mechanical Vapor Recompression method leads to a substantial reduction in utility consumption, decreasing the rate for feed separation from 3.92 kg of utilities per kg of feed to 1.52 kg of utilities per kg of feed. This represents an impressive improvement in process efficiency. The exergy analysis reveals that the Joule-Thomson valve is the primary contributor to total exergy loss. Notably, the reboiler and distillation column's condenser exhibit significantly reduced exergy losses, 33.77 % and 39.05 % lower, respectively, compared to the base case. This emphasizes the positive impact of the proposed optimization on exergy efficiency.

Performance comparison of vertical and horizontal vacuum membrane distillation module coupled with mechanical vapor recompression

This paper focuses on the comparative study of vertical and horizontal vacuum membrane distillation (VMD) modules coupled with mechanical vapor recompression (MVR) system to obtain the optimal system layout structure and further improve operation stability and energy efficiency in the wastewater treatment. Firstly, freshwater accumulation characteristic in the vertical VMD module was explored under different working conditions. Then, comparative experiments of vertical and horizontal VMD-MVR systems were conducted. Finally, comprehensive performance of horizontal VMD-MVR system were evaluated. The obtained results showed that freshwater production in the distilling tank and freshwater accumulation in the VMD module were affected by operation time, feed temperature, feed flow rate, feed concentration and vacuum side pressure. Furthermore, the horizontal VMD-MVR system was proved to be a better choice due to lower freshwater accumulation in the VMD module and energy consumption in comparison to the vertical VMD-MVR system. Finally, long term operation experiment of 240 h indicated evaporation rate dropped to 55 kg/h as operation time reached to 180 h owing to membrane fouling. After membrane cleaning, evaporation rate recovered from 55 to 62 kg/h with a higher recovery efficiency of 95.1 %. Compared to conventional wastewater treatment systems, the horizontal VMD-MVR system exhibited excellent comprehensive performance.

Evaluating the Operation of a Full-Scale Sequencing Batch Reactor–Reverse Osmosis–Evaporation System Used to Treat Landfill Leachates: Removal of Pollutants, Energy Consumption and Greenhouse Gas Emissions

Limited information is available in the literature regarding the energy consumption and the greenhouse gases emitted during landfill leachates treatment. A full-scale landfill leachates treatment system that included primary sedimentation, biological treatment in sequencing batch reactors, reverse osmosis and mechanical vapor recompression evaporation was monitored and evaluated for the removal of major pollutants, energy consumption and greenhouse gas emissions. Samples were taken during a period of two years from different points of the system, while the actual power consumption was calculated considering the available mechanical equipment and the hours of operation. The quantities of greenhouse gases emitted were estimated using appropriate equations and based on the operational characteristics of the system. According to chemical analyses, biological treatment resulted in partial removal of COD and total nitrogen, while the removal of BOD5 and NH4-N was significant, reaching 90 and 98%, respectively. Use of reverse osmosis increased the removal of all pollutants, satisfying the requirements of the legislation on wastewater discharge into the environment. Power consumption was calculated to be 35.3 KWhr per m3 of treated leachate, while mechanical vapor recompression evaporation was responsible for 60.5% of the total energy required. The contribution of other processes to energy consumption was as follows, in decreasing order: sequencing batch reactors > reverse osmosis > primary treatment. The roots blower vacuum pump used for mechanical vapor recompression evaporation, and the blowers providing air to the sequencing batch reactors, were the most energy-intensive pieces of apparatus, contributing 44.2% and 11.3% of the required energy, respectively. The quantity of greenhouse gases emitted was estimated to be 27.7 Kg CO2eq per m3 of treated leachates. Among the different processes used, biological treatment and mechanical vapor recompression evaporation contributed to 45.7% and 44.1% of the total emissions, respectively. The findings of this study reveal that an integrated landfill leachate treatment system that combines biological treatment and reverse osmosis can assure the protection of the aquatic environment by producing high-quality effluent; however, further research should be conducted regarding the sustainable management of reverse osmosis concentrate. Mechanical vapor recompression evaporation contributes significantly to the environmental footprint of the landfill leachates treatment system due to both high energy consumption and elevated emissions of greenhouse gases.

Energy-saving process development for the purification of propylene glycol based on MVR heat pump distillation combined with thermally coupled technology

In the process of recovering organic compounds from wastewater generated by propylene oxide (PO) production plant, the low concentration of propylene glycol (PG) in the wastewater makes it difficult and energy-intensive to achieve the high concentrations purify of PG using conventional distillation technology. Additionally, there is no publicly available commercial technology for this purpose. Therefore, the aim of this work is to develop an energy-efficient PG purification process based on mechanical vapor recompression (MVR) heat pump distillation combined with thermally coupled technology. Several energy-saving methods were implemented as follows. Firstly, MVR distillation technology was used to purify PG from 2.22% to 33.3% in the PG concentration tower, and the gas at the top of the tower was compressed and pressurized to serve as the heating medium for the reboiler, which significantly reduced the consumption of fresh steam. Secondly, in order to achieve heat matching, the dehydration tower was divided into two parts. The surplus steam compressed by the compressor was then served as the heat source for the reboiler of the first dehydration tower to reduce steam consumption, while achieving 98.7% water removal. Thirdly, the condenser of the de-heavy tower and the scraping film evaporator were thermally coupled to reduce the consumption of heating and cooling media. Based on the aforementioned energy-saving measures, the developed optimization process can achieve PG purification of over 90%, while significantly reducing costs. The total annual cost (TAC) is reduced by 34.89% compared to the traditional distillation process.

Simultaneous production of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from recovered volatile fatty acid with treatment of leachate by Pilot-Scale Mechanical Vapor Recompression

Serious global problems faced due to many petroleum-based materials in the last century, which is called the plastic age, constitute the main motivation of this research. Considering wastewater treatment from this perspective, both the recovery of organic acids from wastewater and their conversion into bioplastics are extremely important in terms of reducing petroleum dependency. In this study, while the treatment of landfill leachate was provided with biological process integrated into Mechanical Vapor Recompression (MVR), simultaneously PHBV production was carried out with 84.9% recovered VFA as carbon source. The effects of C/N/P ratio and feeding regime on PHBV storage were investigated by Cupriavidus necator. PHBV storage of 96% (g PHBV/g DCW) was maximized by 2-stage feeding and nitrogen restriction. The ratio of 3HV to 3HB of PHBV was 45%. In addition, extracted PHBV was compared with standard PHA in terms of thermal and chemical properties with FTIR, XRD, TGA and DSC analyses.

Techno-economic assessment for black liquor concentration system of chemical pulp integrating mechanical vapor recompression

Mechanical vapor recompression (MVR) is mostly used for the evaporation of black liquor in chemical pulp production process because of low operating cost, high thermal efficiency and small footprint. This paper designed a black liquor concentration system of Chemical pulp integrating MVR (BLCS-MVR), modeled the energetic and economic requirements of BLCS-MVR. The results found that the total cost increases as the solid content of black liquor leaving MVR segment increases, MVR has lower operation cost than the traditional evaporation technology when the solid content of black liquor after MVR segment is less than 37.5%. Compared with the traditional evaporation system, the total energy cost of new system is reduced by 21.0%, and the latter three-effects of the traditional six-effect evaporation can be replaced by MVR system. Steam consumption can be reduced by 48.2%, and the payback period is only 2.72 years. Sensitivity analysis showed the steam price impacts the economy of BLCS-MVR most, followed by the electricity price, the investment cost and the production scale. This research provides a theoretical basis and technical reference for the application of MVR in the black liquor concentration of chemical pulp, which contributes to the realization of “carbon neutralization”.

Evaluation of volatile fatty acids and ammonia recovery approach from landfill leachate using pilot-scale mechanical vapor recompression

Treatment of landfill leachate is still a current problem due to the high treatment costs in addition to the difficulty of meeting the discharge criteria. However, there is a more important issue that should be underlined; it is also valuable compounds that leachate contains. Conventional methods used for treatment of leachate such as membrane filtration, advanced oxidation processes, biological processes and their combinations have largely focused on treatment. However, the recovery of ammonia and volatile organic acids (VFA) in leachate is a promising approach both to overcome high treatment costs and to sustainably manage leachate. In this study, leachate treatment potential was investigated by mechanical vapor recompression (MVR) process, which offers an operational opportunity to recover high value-added products from leachate while providing an effective treatment for wastewater. Optimum operating conditions for the pilot-scale MVR process have been determined by laboratory-scale studies. VFAs were recovered as organic acid salts from the pilot-scale MVR distillate, while ammonia recovery was accomplished as ammonium sulfate from a highly contaminated concentrate stream. VFA and ammonia recovery rates were 89% and 99%, respectively. The treatment cost of leachate with MVR process was calculated according to the data obtained in pilot scale MVR studies considering the operating cost, chemical cost and economical contribution of value-added products. The results showed that the integrated MVR-crystallization process, all treatment costs are covered, with a net gain of 3.8 USD/m3. Consequently, MVR integrated crystallization process offers an economical and sustainable solution for the treatment of leachate by recovering valuable products.

Economic and environmental assessment of heat pump integration in thermally coupled hybrid separation

Process intensification of thermally coupled hybrid separation is presented in this paper. Production of ethyl acetate via reactive distillation with a stripper column (RDS) is employed as a basic thermally coupled hybrid separation process. The reactive distillation column has a condenser and a reboiler and the stripper column has a reboiler only. In addition, no auxiliary separation equipment such as a decanter or a regeneration column is required. On the other hand, despite the RDS process being highly integrated, it has several bottlenecks; large equipment (columns and heat exchangers); high external energy requirements for both cooling and heating. Also, it is known for large recycles (liquid and vapor). Therefore, to further intensify the RDS process, including a heat pump is proposed. A mechanical vapor recompression heat pump (MVRHP) is employed to reduce external cooling and heating requirements; to replace conventional energy source (heating steam) by an external source (compressor driven by electricity from renewable sources). Two different alternatives of heat pump-assisted RDS processes are designed. Performance and effectivity of the designed alternatives are compared with original RDS process using several indicators, including energy aspects, process economics, and environmental footprint. Results show that MVRHP can be deployed in the RDS process effectively reducing energy requirements while no equipment size changes (columns) are needed. Heat pump-assisted RDS processes show better economic performance despite higher capital costs. More importantly, when MVRHP is introduced in the RDS process, environmental footprint in form of CO2 emissions is decreased significantly. Finally, heat pump application in thermally coupled hybrid separation is highly recommended despite higher capital costs. Lower amount of emissions and utilization of electricity from renewable sources being the main benefits.

Advanced downstream processing of bioethanol from syngas fermentation

Syngas fermentation is used industrially to produce diluted bioethanol (about 1–6 wt%). This research study proposes a novel downstream process that recovers bioethanol in an energy-efficient and cost-effective manner, improves fermentation yield by recycling all fermentation broth components (microbes, acetate and water), and is designed for full-scale industrial-level application. Therefore, vacuum distillation at fermentation temperature was conceptually studied as an initial ethanol recovery step, leading to a bottom stream that may be recycled. Advanced separation and purification techniques were designed to recover 99.5% of initially present ethanol as high-purity product (99.8 wt%). Mechanical vapor recompression and heat integration methods were used to maximize sustainability and eco-efficiency of the proposed recovery process. Implementation of these techniques on a process using 6 wt% ethanol feed stream decreased the total annual costs by 54.2% (from 0.175 to 0.080 $/kgEtOH), reduced the primary energy requirement by 66.1% (from 2.82 to 0.96 kWthh/kgEtOH), lowered the CO2 emission by up to 82.6% (from 0.414 to 0.072 kgCO2/kgEtOH), and reduced the fresh water usage by 62.6% (from 0.242 to 0.091 m3W/kgEtOH). Sensitivity analysis for ethanol concentrations ranging from 6 to 1 wt% showed that the recovery costs and energy use increased to 0.336 $/kgEtOH and 1.78 kWthh/kgEtOH respectively. Since ethanol recovery performs better but fermentation will perform worse at higher ethanol concentration in fermentation broth, there is a trade-off concentration for the overall process. The current analysis is an important step toward determining this trade-off.

Research and design experience of a 150 kt/a CO2 capture and purification project in the Shaanxi Guohua Jinjie power plant

There was little research and demonstration experience in large flue gas carbon projects in China. 150 kt/a flue gas CO2 capture project in the Guohua Jinjie power plant, which is the largest-scale flue gas carbon capture project in China, effectively solved this technical bottleneck. The performance of the used compound amine absorbent, phase change absorbent, and the ionic liquid was described, and the compatibility of performance was considered in the project; new energy-saving processes integrated mechanical vapor recompression heat pump, interstage cooling, and split flow desorption. The plane layout of the project was put forward, and the utility consumption of the capture system was analyzed. The paper explained the health, safety, and environmental protection instructions, presented test category tables, and developed energy consumption and economic analyses. The results showed that the renewable energy consumption per unit product was 2.32 GJ/t CO2, the loss of absorbent was less than or equal to 1.0 kg/t CO2, and the total investment (excluding tax) of the project was 13.8398 million yuan. When the CO2 sales price (excluding tax) was 203.43 Yuan/t, the yield was 0 %, and when the CO2 sales price (excluding tax) was 260.949 Yuan/t, the yield was 8 %. The feasibility study research conclusions indicated that the project was technically and economically feasible.