Chihiro Fushimi

Novel Drying Process Based on Self-Heat Recuperation Technology

Significant amounts of energy are used in the conventional methods for drying wet carbonaceous materials such as biomass, low-rank coals, sludge, and manure, because the latent heat for evaporating water is large. An innovative drying process, based on self-heat recuperation technology that recovers not only latent heat but also sensible heat, was developed to save drying energy. Water contained in a wet sample is heated to its boiling point, and the resulting steam is superheated. The superheated steam is compressed to provide a temperature difference for heat exchange. The condensation heat of the compressed steam is exchanged with the evaporation heat of the water from the wet sample. The sensible heat of the compressed steam is utilized to raise the temperature of both evaporated steam (superheating) and water contained in the wet sample (preheating). In addition, the sensible heat of the dried sample is recovered by gas to improve the overall energy efficiency. The amount of energy required for the proposed system was determined using a commercial process simulation tool, PRO/II (v. 8.1, Invensys plc, London, UK). The proposed drying process based on self-heat recuperation was found to drastically reduce the energy consumption to 13.7% of the energy consumption of the conventional drying process with heat recovery.

Steam gasification characteristics of coal with rapid heating

Time profiles of weight change of coal samples and the evolution of low molecular weight gases (H2, CH4, CO and CO2) in both steam gasification and pyrolysis of Yallourn brown coal and Taiheiyo subbituminous coal were measured using a thermobalance reactor with a micro GC and a mass spectrometer, in order to examine the reaction mechanism of steam gasification with rapid heating (100 K s−1). It was found that, in the case of slow heating, steam reacted with metaplast and promoted the evolution of tar above 623 K and that a water shift reaction took place above 873 K. Steam gasification of produced char occurred above 1023 K, increasing the evolution of CO, CO2 and H2. When the heating rate was high, steam reforming of volatile matter and steam gasification of metaplast took place parallel to metaplast formation and condensation. The char produced by pyrolysis was almost completely gasified and converted into H2 and CO2 by steam. The chemical energy of coal was mainly converted into hydrogen energy and the gasification efficiency was slightly increased by rapid heating (i.e. 100 K s−1).

Exergy recuperative CO2 gas separation in pre-combustion capture

The integrated coal gasification combined cycle (IGCC) can achieve higher power generation efficiency than conventional pulverized coal combustion power plants. However, a CO2 capture process prevents improving power generation efficiency of IGCC, because CO2 separation from gas mixtures requires huge amounts of energy. Therefore, in this study, we analyzed the CO2 separation process in the pre-combustion capture process using a process simulator (PRO/II) in the steady state, and proposed a new process using a modularity based on self-heat recuperation (SHR) technology to decrease energy consumption. Pre-combustion capture was applied in the IGCC plant, which involved coal gasification and CO-shift conversion with CO2 capture. The results show that the energy consumption for the CO2 separation process using SHR was decreased by two-thirds. This means that the power generation efficiency can be improved by SHR compared with conventional IGCC with a CO2 capture process.

Simplification and Energy Saving of Drying Process Based on Self-Heat Recuperation Technology

A simplified drying process based on self-heat recuperation (SHR), which can further reduce energy consumption compared to previous SHR drying processes, is proposed. The specific energy consumption (SEC) of the SHR drying process was evaluated at various air flow rates and compared with a mechanical vapor recompression (MVR) drying process with superheated steam. The results show that the SEC of SHR can be reduced from 474 to 147 kJ (kg-H2O evaporated)−1 by removing heat exchangers for preheating. The SEC of the simplified SHR process was only 1/16 of a conventional drying process with heat recovery and 3/5 of an MVR process. Exergy transfer of the process was also analyzed and summarized as exergy flow diagrams.

Energy Saving Technology

This chapter introduces the conventional and latest energy saving technologies for process systems, especially for use in oil refineries and petrochemical plants. One of the most famous energy saving technologies for these processes is a well-known heat recovery technology that uses pinch technology. The hot and cold stream lines can be moved horizontally within the temperature limits in the temperature-heat diagram. Process systems are designed based on this graphical analysis. In contrast, in the latest energy saving technology termed self-heat recuperation technology, the hot stream line is shifted vertically by using the adiabatic compression of the hot stream in the temperature-heat diagram. Thus, the whole process heat can be recirculated into the process without any heat addition, leading to further energy saving in the process systems. In addition, process design methodology based on self-heat recuperation and the overall energy efficiency of the designed process are illustrated using simple thermal and distillation process examples.

Analysis of IGFC With Exergy Recuperation and Carbon Dioxide Separation Unit

Integrated Coal Gasification Fuel Cell Combined Cycle (IGFC) is expected to be the most efficient power generation system in coal fired power generation systems [1,2]. However, more energy efficient power generation system has to be developed to decrease CO2 emission in the middle and long term. Thus, the authors have proposed Advanced Integrated Coal Gasification Combined Cycle (A-IGCC) and Advanced IGFC (A-IGFC) systems, which utilize exhaust heat from solid oxide fuel cells (SOFC) and / or a gas turbine as a heat source of gasification (exergy recuperation) [3]. Previously A-IGCC [4] and A-IGFC [5] without CO2 capture option were analyzed with the process simulator HYSYS®.Plant (Aspen technology Inc.) to calculate thermal efficiencies of the proposed systems. Then IGCC and A-IGCC with CO2 capture option [6, 7] were analyzed with Amine process simulator AMSIM(DBR), a module in PRO/II® (Invensys Process Systems Japan, Inc) combined with HYSYS®.Plant model. It shows in the results of thermal efficiency with CO2 capture option that the penalty of A-IGCC case is larger than that of IGCC case, indicating somewhat scope for increase of exergy recuperation in A-IGCC case [6]. This study deals in the analyses of A-IGFC with CO2 separation unit.Copyright

Advanced Integrated Coal Gasification Combined Cycle: Current Status of Development

Advanced integrated coal gasification combined cycle (A-IGCC) and integrated coal gasification fuel cell combined cycle (A-IGFC), which recuperate the exhaust heat from gas turbine and solid oxide fuel cells as heat source of endothermic gasification technology, are promising technologies because higher thermal efficiency is expected than that of conventional coal-fired power generation systems. In this article, the authors introduce current status of the system design and thermal efficiency analyses of the A-IGCC/IGFC systems, and a novel triple-bed combined circulating fluidized-bed (TBCFB) gasifier for the A-IGCC/IGFC systems. The challenges of the A-IGCC/IGFC systems and TBCFB gasifier are also introduced.

Design methodology of absorption process (use of MEA absorbent) based on self-heat recuperation technology

A chemical absorption process is the most commercially used process for CO2 separation in flue gases. However, the process needs a huge amount of energy to strip CO2 in a stripper. To overcome this problem, a new gas separation process using chemical absorption method based on self-heat recuperation technology is proposed in this study for energy saving. In this process, the regeneration energy of absorbent is provided from the exhausted heat of absorber and stripper by using a compressor and heat exchangers. The process is divided into two modules (absorber and stripper), in which the internal heat circulation is maximized. Then, the process is reconstructed by combining these modules. We evaluated the amount of energy consumption of the process as compared with the conventional gas separation process for CO2 by using a commercial process simulator (PRO/II). From the simulation results, energy consumption of the proposed process decreased to one-third at that of conventional heat recovery process. Thus, the proposed process based on self-heat recuperation technology is a very promising process for energy saving of gas separation.

Gas Separation Section

In this chapter, self-heat recuperation technology (SHRT) is applied in gas separation processes, which are (1) cryogenic air separation and (2) CO2 chemical absorption processes. (1) The energy consumption of cryogenic air separation based on self-heat recuperation (SHR) can be reduced by 40 % compared with a conventional process. In the proposed process, not only the latent heat but also the sensible heat of the process stream is circulated in the process. Furthermore, the pressure in the column can be reduced compared with the high pressure part of a conventional cryogenic air separation process. (2) The energy consumption of a CO2 chemical absorption process based on SHR can be reduced by 70 % compared with the conventional process. In the proposed process, the heat of the exothermic absorption reaction in the absorber and the heat of the steam condensation in the condenser of the stripper are recuperated and circulated for reuse for regeneration of absorbent solution and vaporization in water during CO2 stripping.

Application of a Dielectric Barrier Discharge Reactor for Diesel PM Removal

An uneven DBD reactor driven by a pulse power supply for diesel particulate matter (PM) removal has been characterized using a diesel engine. The relations between energy injection, PM removal, space velocity and pressure loss are given.