Exergy Recuperation Research Articles

A separate-type autothermal CH4 dry reforming system with exergy recuperation

Currently, CO2 conversion and utilization have become a key to mitigate the global warming. In this study, a novel separate-type autothermal dry reforming of methane (S-ATDRM) system is proposed and simulated, in which the methane dry reforming combined with methane partial oxidation is performed in a circulating fluidized bed with exergy recuperation to eliminate the negative effect of the products of CH4 partial oxidation on the DRM reaction and further improve the CO2 conversion efficiency. The results demonstrate that this S-ATDRM system can achieve an exergy efficiency of 84.7 %, and about 1055.7 kW of exergy can be recuperated from the process for crude syngas cooling and reapplied for pre-heating of feedstocks of CO2, O2 and CH4. It is found that the largest exergy destruction in this system occurs in the partial oxidation reactor, which occupies ca. 45.6 % of the whole exergy loss. Comparing with the conventional ATDRM system, although the exergy of S-ATDRM system is decreased by approximately 0.3 %, the CO2 conversion is substantially increased by about 11.3 %.

1-2 A novel biomass IGFC system with exergy recuperation for high efficiency power generation

1-2 A novel biomass IGFC system with exergy recuperation for high efficiency power generation

Energy and exergy efficiencies as design criteria for grain dryers

ABSTRACTWe devised a novel methodology for optimizing cereal grain dryers grounded on the transient spatial–temporal first and second laws of thermodynamics and associated balance equations. Model equations were solved using a special time-adaptive radial basis function. Comprehensive sensitivity tests show the quantitative effects of initial moisture content, air velocity, and drying air temperature on the temporal profiles of outlet air temperature and moisture content and temporally integrated energy and exergy efficiencies. Drying temperature is the most efficacious parameter in the drying range of 50–90°C. Finally, selected examples show optimized dryer operation points under unrestrained and restrained conditions. Second law efficiency is well suited for expressing drying performance, portraying time, noble energy expenditure, and intrinsic sustainability. Three decision tables, based on simulation results, can be used to define dryer design under normal technical choice. First law efficiency and the specific moisture extraction rate are concepts more adequate for designing in-bin low-temperature dryers. Second law efficiency is indicated when exergy recuperation is at stake: higher drying temperatures, shorter drying times, recirculation drying, and other processes.

CO2 Separation Process Using Circulating Fluidized Bed Based on Exergy Recuperation

In this paper, an innovative energy saving CO2 separation process using chemical absorption was proposed from an energy saving point of view. In this process, metal oxide particles were selected as absorbents, which do not require separation energy of liquid/gas. These particles were fluidized by feed gas mixture for increasing segregation effect in the bed and heat transfer rate from chemical reaction to a heat pump system. Heat of absorption was recuperated and supplied as heat of thermal decomposition through a heat pump system based on the principle of exergy recuperation. In addition, some of the heat was circulated with the absorbents. The energy saving performance of the proposed process was evaluated by simulations.

High-temperature latent heat storage technology to utilize exergy of solar heat and industrial exhaust heat

Latent heat storage (LHS) using phase change materials is quite attractive for utilization of the exergy of solar energy and industrial exhaust heat because of its high-heat storage capacity, heat storage and supply at constant temperature, and repeatable utilization without degradation. In this article, general LHS technology is outlined, and then recent advances in the uses of LHS for high-temperature applications (over 100 °C) are discussed, with respect to each type of phase change material (e.g., sugar alcohol, molten salt, and alloy). The prospects of future LHS systems are discussed from a principle of exergy recuperation. In addition, the technologies to minimize exergy loss in the future LHS system are discussed on the basis of the thermodynamic analysis by ‘thermodynamic compass’. Copyright © 2016 John Wiley & Sons, Ltd.

Microencapsulation of metal-based phase change material for high-temperature thermal energy storage.

Latent heat storage using alloys as phase change materials (PCMs) is an attractive option for high-temperature thermal energy storage. Encapsulation of these PCMs is essential for their successful use. However, so far, technology for producing microencapsulated PCMs (MEPCMs) that can be used above 500°C has not been established. Therefore, in this study, we developed Al-Si alloy microsphere MEPCMs covered by α-Al2O3 shells. The MEPCM was prepared in two steps: (1) the formation of an AlOOH shell on the PCM particles using a boehmite treatment, and (2) heat-oxidation treatment in an O2 atmosphere to form a stable α-Al2O3 shell. The MEPCM presented a melting point of 573°C and latent heat of 247 J g−1. The cycling performance showed good durability. These results indicated the possibility of using MEPCM at high temperatures. The MEPCM developed in this study has great promise in future energy and chemical processes, such as exergy recuperation and process intensification.

Development of Innovative Methanol Synthesis Process Based on Self-Heat Recuperation

In recent years, the demand for methanol will continue increasing. As well as other chemical processes, many methanol synthesis processes have reactant recycle system with product separation due to the low conversion ratio of the reactor. For this product separation from reactant recycle stream, a gas-liquid separator or distillation process has often been used. However, this gas-liquid separator and distillation processes are well known as an energy intensive process. Thus, many chemical engineers and investigators have been managing to produce a catalyst which achieves high conversion from reactant to production in the reactor for whole process optimization. In contrast, authors have developed self-heat recuperation technology based on exergy recuperation, in which whole process heat is utilized without any additional heat, leading to the reduction of energy requirement in several chemical processes. In this research, we developed an innovative integrated process design method based on self-heat recuperation for methanol synthesis process from energy saving point of view.

System modeling of exergy recuperated IGCC system with pre- and post-combustion CO2 capture

This paper describes a novel advanced integrated gasification combined cycle (A-IGCC) for heat integration technology with carbon dioxide (CO2) capture. The feature of this system is an exergy recuperation in which the exhaust heat from the gas turbine and the steam are used as gasifying agents, providing higher cold gas efficiency. A-IGCC can achieve higher plant thermal efficiency with much less energy/exergy loss compared to a conventional IGCC. Two CO2 capture options, (i) pre-combustion by a mixture of dimethyl ethers of polyethylene glycol (DEPG) and (ii) post-combustion by monoethanolamine (MEA), were assessed to compare the total plant performance and necessary technologies for future implementation. A-IGCC maintained a higher plant performance than IGCC, delivering sufficient energy in the gasifier for the autothermal reaction. A higher efficiency was obtained in IGCC with pre-combustion capture, with a thermal efficiency of 33.2% compared to 43% without capture. In A-IGCC, however, the higher efficiency was obtained with post-combustion capture, with a thermal efficiency of 38.5% compared to 50.6% without capture. Adding a CO2 removal unit with 81 mol% CO2 absorption imposed the plant efficiency loss of 9.9–15.2%. The surplus heat at lower temperature was left unused when pre-combustion capture was used for the A-IGCC plant model, which resulted in a large reduction in plant efficiency.

E214 バイオマスガス化発電のエクセルギー再生による高効率化(OS-14:環境・エネルギーシステムのスマート化)

E214 バイオマスガス化発電のエクセルギー再生による高効率化(OS-14:環境・エネルギーシステムのスマート化)

Performance Evaluation of Solid Oxide Fuel Cell for Exergy Recuperation of Exhaust Heat by Electrochemical Partial Oxidation

Performance Evaluation of Solid Oxide Fuel Cell for Exergy Recuperation of Exhaust Heat by Electrochemical Partial Oxidation

C114 マイクロチューブ型SOFCを用いたメタンの電気化学的部分酸化による中低温排熱のエクセルギー再生 : 中低温で高性能なSOFC作製方法の確立(OS5 水素・燃料電池)

C114 マイクロチューブ型SOFCを用いたメタンの電気化学的部分酸化による中低温排熱のエクセルギー再生 : 中低温で高性能なSOFC作製方法の確立(OS5 水素・燃料電池)

Exergy Recuperative CO2 Gas Separation in Post-Combustion Capture

Exergy recuperation is applied to CO2 gas separation processes with chemical absorption for post-combustion capture. The heat of the exothermic absorption reaction in the absorber and the heat of steam condensation in the condenser of the stripper are recuperated and circulated to reuse for regeneration of solution and vaporization of water under CO2 stripping using exergy recuperation technology. We evaluated the amount of energy consumption of the exergy recuperative process in comparison with the conventional CO2 gas separation process by using a commercial process simulator (PRO/II, Invensys). The simulation results show that the energy consumption of the exergy recuperative CO2 gas separation process can be decreased to 30% of that of the conventional self-heat recovery process.

G103 円筒型SOFCを用いたメタンの電気化学的部分酸化による排熱のエクセルギー再生 : 数値計算による熱取込量と発電性能の定量化(OS5 水素・燃料電池)

G103 円筒型SOFCを用いたメタンの電気化学的部分酸化による排熱のエクセルギー再生 : 数値計算による熱取込量と発電性能の定量化(OS5 水素・燃料電池)

High-density circulating fluidized bed gasifier for advanced IGCC/IGFC—Advantages and challenges

Coal-fired Integrated Gasification Combined Cycle (IGCC) and Integrated coal Gasification Fuel-cell Combined cycle (IGFC) are being developed as high-efficiency electric power generation technology. However, the highest theoretical gross thermal efficiency of the conventional IGCC/IGFC is still below 52%. In order to obtain higher power generation efficiency, an advanced IGCC (A-IGCC) or advanced IGFC (A-IGFC) system making use of the exergy recuperation concept by recycling waste heat from gas turbine or fuel cells for steam gasification of coal and biomass was proposed in our laboratory. Corresponding to this system, a novel high-density triple-bed combined circulating fluidized bed (TBCFB) gasifier, composed of a downer pyrolyzer, a bubbling fluidized bed char gasifier, and a riser combustor, was proposed to replace traditional gasifiers such as the entrained flow bed gasifier. The new system is expected to more effectively utilize the waste heat from gas turbines or fuel cells and the heat produced by the combustion of the unreacted char in the riser combustor for pyrolysis and gasification of coal and biomass. In this short review, the advantages and future challenges in the development of high-density TBCFB gasifier are presented and discussed.

C204 電気化学的部分酸化による排熱のエクセルギー再生に関する調査研究(OS4 省エネルギー・小型分散電源・コジェネ技術)

C204 電気化学的部分酸化による排熱のエクセルギー再生に関する調査研究(OS4 省エネルギー・小型分散電源・コジェネ技術)

OS7-3 A-IGCCプロセスの検討 : 水蒸気による炭素転換率がシステム性能に与える影響(OS7 高温・高効率発電・エネルギー貯蔵技術,分散と集中の共存)

The final purpose of this study is the investigation of the ability to increase the system efficiency by introducing the chemical exergy recuperation for the integrated system of a low temperature gasifier of coal and a gas-turbine or SOFC. In this paper, for the discussion of theoretical optimum point, the system performances were calculated under the several conditions of the carbon conversion ratio with steam.