Self-heat Recuperation Technology Research Articles

Multiparameter optimization of the acid gas removal process using self-heat recuperation technology in IGCC system based on genetic algorithm

The acid gas removal (AGR) process in the integrated gasification combined cycle (IGCC) system consumes a large amount of heat and reduces the generation efficiency. Process modification of self-heat recuperation (SHR) technology based on vapor compression heat pumps is expected to reduce the energy consumption of the AGR process. On this basis, this paper conducted a comprehensive and parametric analysis of the AGR process integrated with a vapor compression heat pump. Wherein, two key parameters, the stripper pressure (P1) and the heat pump heat exchanger inlet pressure (P2), were analyzed in detail to understand the energy consumption characteristics of each module of the system. By establishing the optimization objective functions of minimizing system operating cost and exergy loss respectively, the system multi-parameter optimization was conducted based on the genetic algorithm by coding and solving in HYSYS and MATLAB. The corresponding parameter variables for the optimal cases of the two optimization objectives are also comparatively derived. The results showed that P1 mainly changes the SHR capacity of the system by changing the allowable flow rate of the SHR mass under different working conditions, while P2 mainly affects the SHR capacity of the system by changing the heat of the fraction at the top of the stripper. The minimum operating cost of the system decreased to 0.0655 $/kgH2S, which is 1.50 % lower compared to the original case. The minimum exergy loss of the system is reduced from 7788.89 kW to 7398.59 MW, which is about 5.01 % lower than that of the original case.

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.

Performance analysis of the acid gas removal from syngas based on self-heat recuperation technology

Considering the high energy consumption of the acid gas removal (AGR) unit in integrated gasification combined cycle (IGCC) systems, this paper innovatively combines the two self-heat recuperation technology (SHRT) forms with the syngas purification process. The AGR unit and the power generation unit in this paper are simulated by Hysys V11. By establishing the energy balance and exergy balance equation for each component, the change of energy consumption and exergy loss of the unit before and after the process modification is analyzed. Compared with the two improved methods, Case1 uses low-pressure water as the working medium of SHRT process, which has the characteristics of high COP of heat pump and low throttling loss, and achieves good results in terms of operating cost and exergy loss. Case1 has 3.75% lower operating cost compared with the basic process, the annual operating cost of H2S removal is reduced by 144,200$, and the exergy loss of the AGR unit is reduced by 23.48 kW. Case2 does not have advantages under the two evaluation indexes. Subsequently, sensitivity analysis of the inlet pressure of Case1 heat pump exchanger further improves the energy-saving potential of this retrofit solution. The article explains the effect of the SHRT process in the AGR unit on the exergy loss of the rich solvent regeneration process and the distillate cooling process, and verifies the energy-saving potential of the SHRT in the acid gas removal unit of IGCC.

Multi-objective Optimization and Control of Self-Heat Recuperative Azeoropic Distillation for Separating an Ethanol/Water Mixture.

Azeotropic distillation is an important method for the separation of an ethanol/water mixture, while the main disadvantage of azeotropic distillation is its high energy consumption. Since the self-heat recuperation technology can effectively recover and utilize the heat of effluent stream in thermal processes, it is introduced into the ethanol dehydration process. The conventional azeotropic distillation and self-heat recuperative azeotropic distillation (SHRAD) are simulated and optimized with multiple objectives. There exists a design point in the Pareto solution set for which the total annual cost is the lowest, the thermodynamic efficiency is the highest, and the CO2 emission is the least. Based on the specified design, the dynamic characteristics of the SHRAD configuration are studied, and two control structures are proposed. The improved control structure of the SHRAD process works well under the feed flowrate and composition disturbance, and the SHRAD system can obtain a high-purity ethanol product. The results show that the SHRAD process has significant advantages over conventional azeotropic distillation in terms of economic and environmental benefits. In addition, an effective control structure can ensure the stable operation of the SHRAD process.

Performance Analysis of the Acid Gas Removal from Syngas Based on Self-Heat Recuperation Technology

Performance Analysis of the Acid Gas Removal from Syngas Based on Self-Heat Recuperation Technology

Electrical-driven self-heat recuperative pressure-swing azeotropic distillation to minimize process cost and CO2 emission: Process electrification and simultaneous optimization

Azeotropic separation by pressure-swing distillation (PSD) is one of the most costly processes in the chemical industry. To minimize process cost and CO2 emission, process electrification based on self-heat recuperation technology (SHRT) has been implemented in many thermal-driven processes. Enlightened by these facts, a novel electrical-driven PSD-SHRT process is proposed and compared with conventional thermal-driven PSD (PSD-CONV) and PSDs integrated with heat integration and heat pump. Two typical binary systems – tetrahydrofuran (THF)/water with minimum-boiling azeotrope and acetone/chloroform with maximum-boiling azeotrope – are selected to investigate the potential economic and environmental benefits of process electrification. To make a fair comparison, all the processes are optimized to a minimum in total annualized cost (TAC) based on a simulation-based optimization framework combining Aspen Plus (process simulator) and MATLAB (external optimizer). The optimization results indicate PSD-SHRT to be the lowest in both TAC and CO2 emission of all the alternative processes. In THF/water system, PSD-SHRT triumphs over PSD-CONV by 23.72% in TAC and 83.67% in CO2 emission, respectively. Corresponding values increase to 47.82% and 92.90% in the acetone/chloroform system. These improvements verify the significant advantages of process electrification and also encourage more originations to introduce SHRT into other processes.

Self-recuperative high temperature co-electrolysis-based methanol production with vortex search-based exergy efficiency enhancement

Abstract The reduction of greenhouse gas emission via the transformation of carbon dioxide into methanol results in several secondary benefits including the production of a valuable by-product that can be used for energy storage and as a fuel source. As such, this is a promising approach for mitigating climate change. Methanol production via the co-electrolysis process using solid oxide electrolyzer cells is an efficacious solution to the issue of excess electricity storage in the context of renewable energy and carbon dioxide utilization. However, this process is an energy-intensive and temperature-sensitive method, mainly due to the requirement of high-temperature electrolysis. In this context, this study investigates and evaluates the potential for overall performance improvement by minimizing energy consumption and increasing methanol production using self-heat recuperation technology. The newly developed vortex search strategy was employed to achieve the maximum potential benefit from retrofitted recuperators. Detailed exergy analysis was performed for the process and the evaluation of its performance. The findings revealed that the electrochemical system for co-electrolysis has the highest exergy destruction rate. By employing the vortex search approach, the exergy loss of the energy process system can be reduced by 61.7% with a total reduction of the exergy loss of 15.9%, while improving methanol production and decreasing distillation reboiler duty. The simple solution of self-recuperation with optimization that was utilized in this study is a flexible approach that can be directly applied to the improvement of co-electrolysis and methanol synthesis.

Thermodynamic analysis of a novel wood drying system based on self-heat recuperation technology

ABSTRACT The issue of energy consumption in the field of wood drying has attracted widespread concern worldwide. In this paper, combining with the self-heat recuperation technology, a novel self-heat recuperation wood drying system (SHRWDS) with a fixed bed dryer is proposed to recover the sensible heat and latent heat of humid air, which is not fully utilized in the general drying process of wood. Mathematical models of the SHRWDS based on the conservation of mass and energy are established, and the effects of drying temperature, airspeed, and compression ratio on the energy and exergy input as well as the economy of the whole system are also carried out. The simulation results show that the drying temperature and the airspeed have a positive influence on the system performance, with optimal values, while the effect of the compression ratio is closely related to the relative humidity of the humid air at the outlet of the dryer. Furthermore, the minimum energy input of 77.23 kJ/s and exergy input of 28.27 kJ/s for the system are obtained at the condition of t= 60°C, v= 1.5 m/s, and φ= 90%, while the minimum annual consumption of standard coal volume and the lowest cost of wood drying for the SHRWDS are 68.34 t and 16.54 $/t. All of this indicates the remarkable superiority of the presented system compared with the traditional device.

A systematic method for optimum heterogeneous azeotropic distillation systems with vapor recompression

In this work, a systematic method is proposed to determine the optimum combination of self-heat recuperation technology (SHRT) and heterogeneous azeotropic distillation (HAD). The heat exchanger network and vapor recompression heat pump are applied to develop the energy-saving HAD process based on SHRT (HAD-SHRT). Then the heat exchanger network (HEN) is utilized to optimize HAD-SHRT process through minimizing the hot utility utilization. Pyridine/water and 1,4-Dioxan/water systems are studied to examine the feasibility of the systematic method. The results show that the systematic method can effectively handle the combinations of SHRT and HAD. When the maximum heat provided by the compressed stream is greater than or equal to the hot utility requirement of the reboiler, the overhead vapor is directly compressed to provide heat for the bottom stream. Otherwise, adding preheater or auxiliary reboiler are favorable options with regard to economic and energy-saving performance.

Process synthesis and simulation-based optimization of ethylbenzene/styrene separation using double-effect heat integration and self-heat recuperation technology: A techno-economic analysis

Ethylbenzene/styrene separation is a typical example of the most costly processes in the chemical industry due to their close-boiling points of these two species. To reduce the cost of their separation, the concepts of double-effect distillation (DED) and self-heat recuperation technology (SHRT) have been implemented to produce three energy-efficient distillation configurations in either an individual or synergistic manner. To obtain a fair comparison, all the candidate processes were optimized to a minimum in total annual cost (TAC), using a simulation-based optimization framework on a simulator Aspen Plus and an optimizer programmed in MATLAB with a metaheuristic algorithm. For a small treatment capacity (100 kmol/h) and a short payback period (PBP, 3 years), the DED and SHRT configurations were found to reduce the TAC by ~8% compared to the conventional process design. The TAC reduction can be improved to as much as ~28% with a larger capacity (1000 kmol/h). The synergistic DED-SHRT configuration has the lowest energy consumption, but its high capital investment makes it only economically viable for longer PBPs. The best scheme under either short or long PBP appeared to be SHRT. Since the conventional design and SHRT share close technical parameters, the former will benefit more when retrofitted into the latter when minimum process modifications are applied.

Performance Enhancement of Reactive Dividing Wall Column Based on Self-Heat Recuperation Technology

Reactive dividing wall column (RDWC) is a highly integrated configuration where reaction and separation take place in a single equipment simultaneously. In this study, three self-heat recuperative ...

Design and optimization of reactive distillation processes for synthesis of isopropanol based on self-heat recuperation technology

In this work, a conventional reactive distillation process (CRD) is designed for isopropanol synthesis. Furthermore, five processes based on self-heat recuperation technology (SHRT) are designed to improve energy-saving performance of CRD. And then heat exchanger network is introduced into two processes based on SHRT to reduce more energy consumption. Finally, a reactive dividing-wall column process (RDWC) is developed to compare with other processes in energy-saving performance. The result of comparison indicates that total annual cost (TAC), total energy consumption (TEC) and CO2 emissions of processes based on SHRT and RDWC are decreased effectively compared with CRD. The performance of process based on SHRT is better than that of RDWC. The RD-VR-HEN is the optimal process. Compared with CRD, RD-VR-HEN saves 34.72% of TAC, 63.16% of TEC and 55.04% of CO2 emissions. Compared with RDWC, TAC, TEC and CO2 emissions of RD-VR-HEN decreases by 13.80%, 54.05% and 44.62%, respectively.

Improving the performance of heterogeneous azeotropic distillation via self-heat recuperation technology

Azeotropic distillation is one of the most energy intensive processes and widely used to separate thermos-sensitive azeotropes. In this work, several heterogeneous azeotropic distillation processes based on the vapor recompression heat pump (VRHP) and self-heat recuperation technology (SHRT) are proposed to study the energy-saving performance. The results show that the heterogeneous azeotropic distillation process based on self-heat recuperation technology (HAD-SHRT) has better performance in economic and environment. In HAD-SHRT process, the sensible heat and latent heat of the vapor streams are recuperated and supplied to the reboilers. The remaining sensible heat is supplied to the preheaters through the heat exchanger network (HEN). Adding a preheater can reduce the duty of compressor by increasing the initial temperature of the stream. Compared with the conventional heterogeneous distillation process, the HAD-SHRT process can save 38.50% of TAC, 93.30% of CO2 emissions, and 80.92% of energy consumption. The thermodynamic efficiency can increase to 13.51%.

Energy-Efficient Design of Downstream Separation To Produce n-Butanol by Several Heat-Integrated Technologies

Biobutanol is a widely used biofuel, and it is traditionally produced mainly via the fermentation process of acetone–butanol–ethanol (ABE). However, separation of the ABE fermentation broth featuring a low concentration of n-butanol in the presence of butyric acid and acetic acid consumes considerable energy. For the sake of reducing the capital cost as well as the energy consumption greatly, a novel DWC-SHR process was proposed to achieve further energy saving through the combination of dividing wall column technology and the self-heat recuperation technology. Moreover, the heat exchanger network (HEN) can be applied to design the HEN of the DWC-SHR process. The DWC-SHR process can be compared with the base process as well as the heat-integrated processes (HI-A process and HI-B process) from the point of the energetic, economic, as well as environmental impact. The results illustrated that the DWC-SHR process can achieve 71.13%, 57.87%, and 47.79% savings of energy consumption compared to that of the bas...

Thermodynamic mechanism of self-heat recuperative heat circulation of vapour system

Self-Heat Recuperation Technology has recently been proved to be an effective method to cut the huge energy consumption in the chemical industry. In the present paper, the thermodynamic mechanism of the self-heat recuperative heat circulation of the vapour system without chemical reaction is studied in terms of exergy analysis using process module, temperature-entropy and energy conversion diagrams. The self-heat recuperative thermal vapour cycle process was modularized by combining four types of thermodynamic elementary process modules, namely isobaric heating and cooling process modules (heat receiver (HR) and heat transmitter (HT)) and isentropic compression and expansion process modules (work receiver (WR) and work transmitter (WT)), and a heat exchange process module (heat exchanger (HX)). In the four types of thermodynamic elementary process modules (HR, HT, WR, WT), both exergy and anergy are conserved. It is only in the heat exchange process module (HX) that exergy destruction takes place and the destructed exergy transforms into the same amount of anergy due to irreversibility of heat transfer. In the self-heat exchange process, the process fluid undergoes temperature change and phase transition. Therefore, the self-heat exchange process should be divided into three stages, namely the self-heat exchange of the liquid sensible heat, the self-heat exchange of the latent heat, the self-heat exchange of the vapour sensible heat. Correspondingly three HXs are necessary, and only in these three HXs do all the exergy destructions of the self-heat recuperative thermal vapour cycle process take place. The work provided as the minimum work required for the self-heat recuperative heat circulation of the vapour system by compressing the process fluid in the vapour phase through one WR, i.e. work input, equals the sum of the exergy required to compensate for the three exergy destructions of the three HXs and the exergy required to discard waste heat to the environment. The work input eventually converts to the waste heat, i.e. heat output, the exergy of which is the exergy required to discard the waste heat to the environment and the anergy of which results from the three exergy destructions of the three HXs.

Innovative Methanol Synthesis Process by Using Exergy Recuperative Pressure and Heat Circulation Modules

The demand for methanol will continue increasing methanol is attractive as fuel applications and chemicals. To reduce energy requirements for the methanol synthesis, it is necessary to investigate a whole process and to retrofit it with energy saving processes. Recently, the authors developed a self-heat recuperation technology (SHR) for saving energy and developed the exergy recuperative pressure and heat circulation modules to expand SHR to the pressure recovery. In this paper, the feasibility of applying exergy recuperative pressure and heat circulation modules to the methanol synthesis process was investigated and an innovative process for methanol synthesis process was developed from the energy saving point of view. By installing exergy recuperative pressure and heat circulation modules to the methanol synthesis process, the energy consumption of the process can be greatly reduced.

A novel energy-saving pressure swing distillation process based on self-heat recuperation technology

Pressure-swing distillation (PSD) is widely used to separate pressure-sensitive azeotropes. In the PSD process, the bottom stream is heated by hot utility in reboiler and the vapor stream is condensed by cold utility in condenser. Consequently, most of the heat supplied to reboiler is wasted in condenser. Self-heat recuperation technology is applied to achieve a novel energy-saving SHR-PSD process. In the SHR-PSD process, two compressors are used to improve the energy levels of two overhead streams so that the heat of the streams discharged from the compressors can be used to heat reboilers for both columns, and the sensible heat can be used to heat feed streams. Additionally, the heat exchanger network is used to optimize the heat integration of the SHR-PSD process. The proposed SHR-PSD process is compared with PSD process and full heat-integrated PSD (FHIPSD) process in terms of the energetic, economic and environmental performance. The results revealed that SHR-PSD process reduces energy consumption by 72.39% and 53.06% compared with the PSD and FHIPSD respectively, and the total annual cost is reduced by 36.65% and 5.18% compared to that of the PSD and FHIPSD, respectively. Moreover, this SHR-PSD process leads to lower CO2 emissions and improve thermodynamic efficiency.

Design and energy evaluation of a stand-alone copper-chlorine (Cu-Cl) thermochemical cycle system for trigeneration of electricity, hydrogen, and oxygen

In this article, a new stand-alone Cu-Cl cycle system (SACuCl) for trigeneration of electricity, hydrogen, and oxygen using a combination of a specific combined heat and power (CHP) unit and a 2-step Cu-Cl cycle using a CuCl/HCl electrolyzer is presented. Based on the self-heat recuperation technology for the CHP unit and the heat integration of the Cu-Cl cycle unit, the power efficiency of the SACuCl for 5 prescribed scenarios (case studies) is predicted to achieve about 48% at least. The SACuCl uses the technologies of the dry reforming of methane and the oxy-fuel combustion to achieve a relatively high CO2 concentration in the flue gas, and CO2 emissions for power generation could be almost restricted by 0.418 kg/kWh. From the aspect of the electricity required for hydrogen production, it is verified that the 2-step Cu-Cl cycle system is superior to the conventional water electrolyzer because the CHP process supplies the heat/electricity for Cu-Cl thermochemical reactions and a thermoelectric generator is connected to the exhaust gas for recovering the power consumption from the compressor and the CuCl/HCl electrolyzer. Finally, the heat exchanger network and the pinch technology are employed to determine the optimum heat recovery of the Cu-Cl cycle. In case 5 analyzed for the SACuCl, the electricity required for the heat-integrated 2-step Cu-Cl cycle is predicted to dramatically decrease from 4.39 to 0.452 kWh/m3 H2 and the cycle energy efficiency could be obviously increased from 23.77 to 31.97%.

Innovative freeze-drying process based on self-heat recuperation technology

Freeze drying is a drying technology that removes water from a target by sublimation of ice to vapor. Drying at low temperature and pressure (below the triple point) results in fewer physical and chemical changes to the dried products compared with the changes observed when using other drying technologies, leading to producing a high quality product. However, the weak point of freeze-drying technology is its large energy consumption. It is therefore necessary to reduce the energy required for the freeze-drying process and the energy costs of production so that this technology can be extended to the drying of other products. In this paper, a new energy-saving freeze-drying process based on the concept of self-heat recuperation technology was proposed. The energy required for the proposed process was compared with a conventional technique using a commercial process simulator. From the simulation results, more than 80% of the energy required for drying can be saved by using the proposed process.

Novel acid gas removal process based on self-heat recuperation technology

Chemical absorption is the most common technology used in the acid gas removal unit (AGRU) for treating natural gas. On the other hand, the regenerator requiring large amounts of energy needed for the latent heat of a phase change makes this an energy intensive process. In this study, several distillation columns with a modified heat circulation module based on self-heat recuperation technology were proposed to enhance the energy efficiency of the AGRU. This innovative self-heat recuperation technology circulates the latent and sensible heat in the thermal process. All simulations were conducted using ASPEN HYSYS V8.6, while KG-TOWER® software was employed to size all the columns. The results showed that the proposed modified configuration can save up 62.5% and 45.9% in terms of the reboiler duty and operating cost, respectively, compared to a conventional AGRU. This brought a saving of 38.0% in terms of the total annual cost. The results also indicated that the carbon emissions could be saved up to 45.4%. The proposed process can be employed to both close-boiling mixtures and wide-boiling mixtures. In addition, a sensitive analysis of the utility costs on the performance of the suggested AGRU configuration were investigated. The retrofit an existing acid gas removal process was performed to enhance both the energy efficiency and capacity.