Heat Integration Research Articles

Economic, environmental, energy, exergy (4E) analysis and simulated annealing algorithm optimization of dividing-wall column-intensified heterogeneous azeotropic pressure-swing distillation process

This work presents an approach for the recovery of high purity cyclohexane (CYCLO) and tertiary butyl alcohol (TBA) from wastewater. After thermodynamic analysis, a heterogeneous azeotrope-pressure swing distillation process (HAPSD) with a decanter is proposed. The heterogenous azeotrope distillation with a high-pressure column and a dividing-wall column process (HADWC) is also being developed to propose a green and sustainable process. The novel processes are optimized using simulated annealing algorithm (SAA). Those processes are optimized by simulated annealing algorithm by linking Aspen Plus and MATLAB via taking the total annual cost (TAC) as objective function. Three energy-efficient HADWC processes are proposed based on the process intensification approach of heat pump and heat integration technologies. All processes are evaluated for multi-criteria performance including economy, energy consumption, gas emissions and thermodynamic efficiency. As the result, HADWC-HP-HI process shows the best performance with 31.79%, 53.46%, 50.69%, and 57.94% reducing over the conventional HAPSD process in terms of TAC, energy consumption, gas emissions and thermodynamic efficiency, respectively.

Investigation on Distillation Column Sequence and Heat Integration Effects in Methanol to Propylene Separation Unit: An Economic Optimization Study Based on Pinch and Exergy Analysis

Investigation on Distillation Column Sequence and Heat Integration Effects in Methanol to Propylene Separation Unit: An Economic Optimization Study Based on Pinch and Exergy Analysis

Applicability exploration and sustainable assessment of heat integration and vapor recompression heat pump to side-stream extractive distillation processes for separating ternary azeotropic system

The side-stream extractive distillation (SSED) process is attracting extensive attention due to its high energy efficiency for separating ternary azeotropic mixture. However, the correlation between the bottom temperature level of distillation columns depending on the flowrates and compositions of side streams and the introduction of heat integration (HI) and vapor recompression heat pump (VRHP) technology is ignored. In the work, a range of initialization extractive distillation processes including one conventional extractive distillation (CED) process and five SSED processes considering different flowrates, compositions, and feed locations of side streams are proposed for separating acetonitrile/isopropanol/water ternary azeotropic system. The optimization results with the minimum the total annual costs (TAC) as the optimization objective show that not all SSED schemes are superior to the CED separation process, and the SSED separation schemes can achieve up to a 2.72 % reduction in the TAC. Following that, the HI and VRHP assisted extractive distillation schemes are proposed based on the temperature levels between the top and bottom of different distillation columns and compressor restraints for the initialization extractive distillation schemes mentioned after optimization. Moreover, sustainable evaluations covering economy, energy consumption, environment, and energy utilization are implemented for the extractive distillation schemes proposed. The evaluation results indicate that the CED-HI scheme overcomes all SSED-HI and SSED-VRHP schemes in terms of economic costs, but the optimal SSED-HI processes can reduce 8.77 % of energy consumption and 4.73 % of CO2 emissions, while the energy utilization raised from 1.70 % to 1.78 % compared to the CED-HI process.

CCUS-assisted electricity-chemical polygeneration system for decarburizing coal-fired power plant: Process integration and performance assessment

In the context of global carbon neutrality, carbon capture and storage (CCS) technology has become an important transition pathway to decarbonizing coal-fired power plants (CFPP). However, CCS technology has strict requirements for geological storage and the potential risk of CO2 leakage. Meanwhile, the deployment of the CCS technology in the CFPP could drastically reduce plant efficiency. To address the aforementioned issues, a novel carbon capture, utilization and storage (CCUS)-assisted electricity-chemical polygeneration process (i.e., ECPP) was proposed to produce electricity, liquid fuels, and high-calorie synthetic natural gas simultaneously. To reduce the efficiency loss caused by the consumption of internal steam and electricity, heat integration and Organic Rankine Cycle (ORC) technologies were adopted to fully recover the available waste heat and achieve the cascade utilization of the internal energy. Meanwhile, a detailed techno-economic assessment was conducted to further determine the benefits of the process integration. The results indicated that the application of heat integration and ORC technologies improves plant efficiency by 6 %. Moreover, it also reduces the cost of electricity and CO2 conversion cost by 17 and 15 %, respectively. In addition, compared with the traditional CFPPs retrofitted with CCS technology, the CO2 utilization and waste heat recovery technologies in ECPP enhance net electricity output and plant efficiency by 19 and 34 %, respectively. Therefore, the proposed CCUS-assisted ECPP achieves the efficient utilization of the waste CO2, and reduces the efficiency penalty for retrofitting the CFPPs. Overall, the proposed ECPP is an essential alternative for the retrofit of the existing CFPPs, and provides a feasible strategy for establishing a clean and sustainable power polygeneration system.

Design and thermo-enviro-economic analyses of a novel thermal design process for a CCHP-desalination application using LNG regasification integrated with a gas turbine power plant

Designing and studying processes with reduced thermodynamic irreversibility and environmental impact is imperative to improve the global applicability of the stand-alone gas turbine cycles. Hence, the present study introduces a novel cascade heat integration tool for a gas turbine cycle combined with a liquefied natural gas cold energy utilization and regasification process. A saltwater desalination subsystem, an absorption chiller, and an organic Rankine cycle are also included in the integrated system. Therefore, the developed system demonstrates an environmentally friendly combined cooling, heating, power, and freshwater production framework, improving the performance of the system in comparison to previous research. This configuration is simulated within the Aspen HYSYS software for comprehensive energy, exergy, environmental, and economic assessments. The findings demonstrate that the whole configuration yields energy and exergy efficiencies of 92.92% and 63.5%, respectively. In comparison, these efficiencies in the single-generation mode are found to be 45.92% and 43.72%, correspondingly. The environmental analysis reveals that the carbon dioxide footprint equals 0.1792 kg/kWh when operating in the multigeneration mode and 0.4591 kg/kWh in the single-generation mode. Furthermore, the economic evaluation exhibits that the cost of energy equals 67.2 $/MWh and 135.92 $/MWh for the multigeneration and single-generation operational modes, respectively.

Design and energy-saving strategy of sustainable pressure-swing distillation with thermally and electrically coupled intensification for separating ternary mixture with multiple azeotropes

The separation of ternary mixtures that form multiple azeotropes is frequently encountered in industry. Benefiting from the pressure-sensitive nature of the azeotropic mixture, the pressure-swing distillation (PSD) is promising to realise the separation without introducing foreign solvents. However, the wide application of PSD seems challenging from an energetic point of view. This work has developed a sustainable PSD process with thermally and electrically coupled intensification to decrease energy consumption, taking the separation of homogeneous acetonitrile/ethanol/water mixture as a demonstrating example. Two conventional PSD processes with different product sequences are designed through the ternary phase diagram and further optimised using the NSGA-II, considering multiple objectives, including total capital cost, total operating cost, and CO2 emissions. The optimal solution is selected by the TOPSIS analysis for each sequence and is then intensified with thermal heat integration and electricity-driven heat pump techniques. The results show that, in comparison to the non-heat-integrated PSD process, the proposed intensified design can dramatically reduce the total annual cost by up to 48%, simultaneously decreasing CO2 emissions by up to 60% and boosting energy efficiency. The present study can be of reference for designing a sustainable PSD process in ternary azeotropic separation.

Thermo-environmental multi- investigation and ANN-based optimization of a novel heat integration criteria system integrated with a marine engine generating liquefied hydrogen

Marine transportation is a significant contributor to overall energy consumption among transportation sectors and is responsible for producing a considerable amount of greenhouse gases. A potential solution for alternative applications involves implementing combined heat integration, thereby enabling the production of additional utilities and mitigating emissions. The current work introduces an innovative heat integration process for a marine engine, focusing on implementing an optimal thermal matching technique to minimize overall irreversibility in producing liquefied hydrogen and coolant. The process incorporates an organic flash-bi-evaporator cooling cycle, a humidification dehumidification desalination, a polymer electrolyte membrane water electrolysis process, and a Claude cycle. The generated freshwater is delivered to the electrolyzer to produce gaseous hydrogen. This product and the cooling for freezing are utilized in the Claude cycle for hydrogen liquefaction. The study utilizes an advanced thermo-environmental multi-criteria investigation and optimization, considering sensitivity analysis and optimization based on artificial intelligence method. The optimization process incorporates the training and testing of artificial neural networks, NSGA-II method, and TOPSIS decision-making. The primary objective functions include exergetic efficiency and carbon dioxide emission. The findings demonstrate that the specified objectives are computed to be 0.121 and 2.67 kg/MWh, correspondingly. Besides, this condition exhibits a liquefied hydrogen flow rate of 6.44 L/h and a cooling output of 43.61 kW, showing an energy efficiency of 0.1145. Also, the total exergy destruction rate associated with the arranged structure is 124.5 kW. Furthermore, the optimum state reveals an exergoenvironmental index of 0.840 and an exergetic stability factor of 0.869.

Thermodynamic feasibility evaluation of an innovative multigeneration system using biogas dry reforming integrated with a CCHP-desalination process

This work investigates a new method for developing systems that use a creative heat integration process that provides heating, cooling, fresh water and power. Specifically, the suggested framework operates by syngas obtained through the dry reforming process of biogas. Environmental considerations and decrease in thermodynamic irreversibility are main features of suggested system. The energy, exergy-related, environmental, and thermoeconomic properties of the suggested system are evaluated after it has been simulated using the Aspen HYSYS software. Results indicate 99,775.5 kW of net power, 10,880 kW of cooling power, and 141,800 kW of heating power. Also, the multigeneration scenario exhibits energy and exergy efficiencies of 58.06 % and 36.0 %, respectively. From the exergetic point of view, total exergy destruction rate is found at 493479 kW. The results of the environmental assessment show that the structure emits 0.27 kg of carbon dioxide per kWh while it is operating in the multigeneration mode. This value is contrasted with a reduction of 34.15 % in heat generation and a decrease of 69.11 % in power generation modes. According to the economic study, when the system functions under multigeneration conditions, the total equipment cost and the levelized cost of products are obtained at 59,536,233 $ and 0.029 $/kWh.

A comprehensive approach for hydrogen production from crude glycerol: Process synthesis, energy integration, and storage

This study presents a comprehensive technique for the production of hydrogen (H2), storage of H2, and energy integration aspects in a single synthesis frame. The crude glycerol, which is derived from waste sources, is being used as a raw material for the production of H2, with the implementation of Aspen Plus software. To further resolve the storage issues, H2 is converted to methanol (CH3OH). The initial crude glycerol undergoes a series of unit operations and processes, such as saponification, acidification, and distillation, to transform it into purified glycerol. Then, using glycerol steam reforming, the generated glycerol is combined with steam to produce H2, where 68 mol% of H2 is produced. The storage and transportation of H2 is a crucial undertaking for several industries. To address this challenge, a unique strategy involves the conversion of H2 into CH3OH through a series of processes, including compression, methanation, and fractionation. Further, a comprehensive evaluation of the entire process is conducted from the perspective of process integration. The design of a heat integration network is customized to each production process. Two key factors—flow and cost—determine the net energy savings. The analysis reveals that 41.44 % of utilities achieve savings based on flow, while 14.24 % achieve savings based on cost.

Energy and economic analysis of alternatives for the valorization of hydrogen rich stream produced in the aqueous phase reforming of pyrolysis bio-oil aqueous fraction

Aqueous phase reforming has been explored for renewable H2 production from waste biomass. Promising results have been reported for pyrolysis bio-oil aqueous fractions (AFB), but economical assessments are needed to determine process feasibility, which requires both energy consumption minimization and optimal H2 valorization. This work compares different alternatives using process simulation and economic evaluation computational tools. Experimental results and a specific thermodynamic model are used to set mass balances. An adequate heat integration allows to reduce the process energy demand, covering the 100 % of the reactor duty. Optimal H2 unit cost is achieved if part of the produced H2 is valorized for energy self-covering and the rest is commercialized. Renewable H2 net production of c.a. 3.3 kgH2/m3 of treated AFB at a preliminary 1–2 €/kg unit cost is estimated, which can be considered as competitive with green H2, even though a case of diluted AFB is considered.

Energy Optimization through Heat and Power Integration on a Chlorobenzenes Production Plant

In this research work, an attempt has been made to address the heat and power integration opportunities for the process of the chlorination of benzene. This process produces a mixture of chlorobenzenes. To increase the production of the dichlorobenzene portion, the ratio of chlorine to benzene is typically 2:1. A process simulation model is designed using Aspen Plus for the production of 70,000 tons/year of dichlorobenzene via the reaction of liquid benzene with gaseous chlorine. Energy analysis is performed for the effective utilization of the utilities by networking the heat exchangers. This modification reduced the process heating and cooling requirements by 56.7% and 12.7%, respectively, and a reduction by 35.4% in the operating costs is achieved, while the annualized fixed cost increased by 9.6%; these changes resulted in savings in the total annual costs of about 10.9%.

Two-stage thermal pyrolysis of plastic solid waste: Set-up and operative conditions investigation for gaseous fuel production

In response to the escalating global challenge of mounting plastic waste and the imperative to adopt more sustainable practices for resource utilization, our study focuses on the utilization of plastic solid waste (PSW) through a two-stage thermal pyrolysis process. This aims to demonstrate its potential as a high-performance alternative to existing two-stage catalytic pyrolysis methods. The experimentation involved processing real scrap PSW material in a lab-scale batch set-up, emphasizing optimizing residence time in the cracking reactor to maximize gas yield and its lower heating value (LHV). The study underscores the advantages of the employed two-stage thermal pyrolysis apparatus through a comparative analysis with established set-up dedicated to maximizing gas yield. Once the operative conditions were explored, resulting pyrolysis products underwent detailed characterization to assess their suitability as a sustainable fuel source. The study also presents a practical application of the produced gaseous fuel, envisioning its combustion in an internal combustion engine (ICE), known for its flexibility regarding fuel properties. This application is demonstrated through a simulation conducted in Unisim Design©. The successful processing of real PSW material in the two-stage lab-scale experimental set-up showcased optimal gas yield achievements (>65 % w/w) with an LHV (∼41 MJ/kg), comparable to that of natural gas. This emphasizes the potential of these sustainable alternatives to replace fossil fuels, especially in the context of ICE applications. The integration of the pyrolysis plant with an ICE demonstrated promising prospects for generating electricity in the transportation sector and facilitating thermal power for heat integration in pyrolysis reactors.

Water management and heat integration in direct air capture systems

Water management and heat integration in direct air capture systems

Photoelectric dual-mode triggered phase change materials for all-weather personal thermal management and shape memory

To cope with the demand of more complex and variable applications, it is urgent to develop dual-mode triggered, breathable, and shape-memory wearable heaters for all-weather personal thermal management of composite phase change materials (PCMs). Herein, after high-temperature carbonization of ZnCo-MOF (metal–organic framework) nanosheet array grown in situ on flexible and breathable carbon cloth (CC) and subsequent encapsulation of polyethylene glycol (PEG), the as-prepared PEG/CC@Co/CNT (carbon nanotube) composite PCMs exhibited good breathability, mechanical strength (tensile strength of 9.15 MPa), thermal energy storage density (114.19 J/g), and shape memory due to the synergy of flexible CC skeleton and rigid PEG. More importantly, composite PCMs possessed excellent solar-thermal (93.7 %, 100 mW/cm2) and electro-thermals (94.5 %, 2.0 V) conversion and storage capacity, benefiting from the conjugation effect of high graphitized carbon/carbon heterostructure with fast electron/photon/phonon transmission and the localized surface plasmon resonance effect of Co nanoparticles. Therefore, the integration of solar heating and Joule heating into breathable composite PCMs can be accurately used for next-generation all-weather, all-season, dual-mode triggered personal thermal management, including indoor/outdoor, daytime/night, rainy/cloudy and other complex and changeable scenarios.

Thermodynamic analysis of novel mixtures including siloxanes and cyclic hydrocarbons for high-temperature heat pumps

This paper presents the investigation of zeotropic binary fluid mixtures containing cyclohexane (critical temperature above 200 °C) as the base fluid with R600, R600a, R601, R601a, R1336mzz(Z), R1234ze(Z), R1233zd(E) and cyclopropane (critical temperatures between 100 °C and 200 °C). For pure components and their mixtures, the performance of the vapor compression system with an internal heat exchanger was analysed at 50 °C and 80 °C heat source and sink inlet, respectively. Variation of the heat source temperature difference and the internal heat exchanger pinch point temperature difference at supply temperatures (140–170 °C) were also investigated. A pinch point temperature difference of 5 K was maintained for the evaporator and condenser. An increase of 6.59 % in COP was obtained with the zeotropic mixture of cyclohexane/cyclopropane compared to that of pure cyclopropane. The design point analysis showed that increasing the heat source temperature difference and internal heat exchanger pinch point temperature difference reduces the COP. The adopted mixture criteria increased the performance between 3.23 % and 3.91 % with respect to standard working fluids like R1233zd(E) and R601, for a 170 °C supply temperature. With this promising thermodynamic analysis in a subcritical operation, the cyclohexane/cyclopropane mixture has prospect of full integration heat pump design.

Design of an integrated system for electrofuels production through Fischer-tropsch process

There has been a growing recognition in recent years that Electrofuels (e-fuels), also known as renewable and sustainable fuels, which are produced from hydrogen and carbon dioxide as the primary feedstocks, have great potential to reduce carbon footprint and address climate change. In the present study, contrary to most previous studies in which the sources of feedstock's preparation were considered as block boxes, two stand-alone processes are taken into account and incorporated into the e-fuels production system. H2 is obtained by a high-temperature electrolysis system having an overall efficiency nearly twice that of a low-temperature electrolysis system. CO2 is captured from a power plant flue gas stream with a purity of 99.81%. Investigating heat integration potential in such an integrated plant is an up-to-date and interesting topic and has not yet been well explored. Therefore, a heat integration within the three individual processes is implemented to reduce energy consumption. The design of the process-to-process heat transfer section is carried out using pinch design rules. By integrating individual units, approximately 42% of the required cold utility, traditionally supplied by chilled water and refrigerants, is allocated to generate high and medium-pressure steams. Having used the high-temperature steam electrolysis for H2 production, a process that requires less external electricity compared to low-temperature water electrolysis, a power-to-liquid efficiency of 70% is achieved. Furthermore, the results reveal a carbon conversion ratio of 98.6%, indicating the effective converting the carbon from the feedstock into liquid hydrocarbons.

Critical impacts of energy targeting on the sustainability of advanced biobutanol separation

Biobutanol stands out as an advanced renewable biofuel, yet its production through fermentation yields a low butanol concentration, necessitating expensive and energy-intensive separation methods, particularly by distillation. Alternative approaches, including adsorptive separation, have emerged, with the 2-column zeolite-based process showing promise. This study employed Aspen Plus for simulating adsorptive separation, utilized Pinch technology for heat integration, and analyzed various alternatives using the life cycle assessment (LCA) approach. Compared to the base case, which relied on our previously acquired experimental data and further purification through atmospheric distillation, the adoption of indirect heating/cooling adsorption reduced heating energy demand by 59.5%. Additionally, cooling energy usage was increased notably by 68.9%, and chilling prerequisites were eliminated. The implementation of Pinch technology further reduced heating and cooling energy requirements by approximately 36%. Multi-pressure distillation was also explored, revealing its potential to reduce heating energy consumption by 46.6%, accompanied by a modest 6.2% increase in cooling energy demand. A gate-to-gate LCA framework was used to evaluate the environmental impacts. The results showed that the combination of indirect heating/cooling adsorption, multi-pressure distillation, and energy-efficient practices resulted in over a 98% reduction in damages related to human health, ecosystem well-being, and resource depletion compared to the base case. Prioritization of key performance indicators revealed that human health had the most significant influence, with prominent midpoint effects attributed to human toxicity and global warming. This study underscores the pivotal role of energy targeting in curtailing energy consumption and enhancing the sustainability of adsorptive biobutanol separation.

Design, modeling, and optimization of a novel 6 kWe hybrid solid oxide fuel cell high temperature-proton exchange membrane fuel cell system

This work investigates a novel approach in terms of design, configuration, heat integration and optimization of a 6 kWe total energy system fueled with natural gas. Specifically, a Solid Oxide Fuel Cell (SOFC) is used for both electricity generation and fuel reforming, since its exhaust stream fuels a polybenzimidazole (PBI)-based, High Temperature-Proton Exchange Membrane Fuel Cell (HT-PEMFC). The study investigates the possible advantages of such a system in both technical and economic terms. After modeling each component/subsystem, the total system model is optimized with the objective function aiming to maximize the net electrical efficiency of the total hybrid system. The system is optimized with a genetic algorithm-based optimization strategy, reaching a net electrical efficiency of 43.6 %. In comparison to standalone fuel cell systems with the same net electrical power output, the proposed hybrid system outperforms both an HT-PEMFC system and an SOFC system, which perform at net electrical efficiencies of 23.2 % and 40.7 %, respectively. Also, the lifecycle cost for the proposed system is $64,097, which is lower than both standalone HT-PEMFC and SOFC systems. Therefore, with the current high rising costs for natural gas, such highly efficient systems are likely to become important elements of the future energy infrastructure.

UTLIZATION OF GENERALIZED HEAT FLUX MODEL ON THERMAL TRANSPORT OF POWELL-EYRING MODEL VIA OHAM WITH HEAT GENEARTION ASPECTS

The focus of this work is on the flow of a spinning Powell-Eyring nanofluid in the boundary layer in three dimensions using magnetohydrodynamics (MHD). The research simulates mass transfer processes and heat transfer processes using non-Fick's mass flux theory and non-Fourier heat flux theory, respectively. Heat transport phenomena are analyzed by the integration of non-linear heat generation/absorption and thermal radiation properties. The boundary layer method is employed to solve a system of nonlinear partial differential equations (PDE) in the mathematical formulation. These equations are converted into nonlinear ordinary differential equations (ODES), and then the optimal OHAM with convergence control parameters is used to solve them. The impact of various physical movement circumstances on concentration and temperature profiles is visually represented through the generation of diagrams. This study provides important new understandings for both applied and scholarly research on complex heat transfer and fluid dynamics mechanisms in the context of three-dimensional MHD boundary layer flows of rotating Powell-Eyring nanofluids.

Energy-saving exploration of separation for EG/1,2-BDO binary azeotrope based on energy, environmental and economic analysis

In the synthesis of ethylene glycol (EG) from syngas, the inevitable by-product, 1,2-butanediol (1,2-BDO), is generated. Additionally, EG and 1,2-BDO form minimum boiling homoazeotrope, which is a challenge for conventional distillation method. To address this, four processes, extractive distillation process (EDP), extractive distillation with heat integration process (HI-EDP), side-stream extractive distillation process (SSEDP), and extractive dividing wall column process (EDWCP), are used for the separation of EG/1,2-BDO binary system. Firstly, a combination of VLE analysis and COSMO-SAC model analysis was employed to select appropriate entrainers (eugenol). Subsequently, interaction region indicator (IRI) was utilized to reveal the extractive distillation mechanism at the molecular level, demonstrating the feasibility of eugenol as an entrainer for separating EG/1,2-BDO mixture. Next, simulations of the EDP, HI-EDP, SSEDP, and EDWCP processes were conducted through Aspen Plus V11. The optimal process parameters for each flowsheet were determined by the minimum Total Annual Cost (TAC). Furthermore, the process performance was evaluated from economic, energy, and environmental aspects. The EDWCP process demonstrates superior performance compared to the EDP process, with reductions of 16.79% in TAC, 17.6% in TOC, and 14.8% in TCC. Additionally, emissions of acidic gases of decreased by 19.78%, while thermal efficiency improved by 32.91%. EDWCP process represent enormous potential in the field of energy efficiency, economy and environment.