Eiichi Koda

System Analysis of IGFC With Exergy Recuperation Utilizing Low-Grade Coal

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]. The Japanese project of the Strategic Technical Platform for Clean Coal Technology (STEP-CCT) aims a target efficiency of 65% (HHV) with exergy recuperation. We have been analyzing the processes of the exergy recuperated Integrated Coal Gasification Combined Cycle (IGCC) and the Advanced IGCC (A-IGCC) [3] which is expected to be realized in 2040. Previous studies have indicated a limitation of the quantity of high temperature steam in the case of auto-thermal reactions with the fluidized bed coal gasifier in the A-IGCC, in particular for TIT 1500 °C class gas turbine. The Advanced IGFC (A-IGFC) system can reduce the exergy loss resulting from combustion, and its ‘exergy recuperation’ is appealing. The waste heat exhausted from the fuel cells is recycled to the gasifier for steam reforming in an endothermic reaction with a low exergy loss and a high cold gas efficiency. Our current study focuses on the optimization of the unit configurations of the A-IGFC including gasifier, compressor, solid oxide fuel cell (SOFC), combustor, gas turbine, heat recovery steam generator (HRSG), and steam turbine. The process simulator HYSYS®.Plant (Aspen technology Inc.) is employed in order to express the gasifier, the SOFC and the other units. The optimum construction over the whole system by numerical simulation was examined for higher energy utilization efficiency. Under ideal conditions using bituminous coal, we verified the power generation efficiency to be 64.5% (HHV). However, utilizing low-grade coals, i.e., lignite and sub-bituminous coal, is deemed an important future energy resource to compensate for a decreasing supply of good-quality bituminous coal. For these low-grade coals, the power generation efficiency was as high as 53.6% (HHV) under the following conditions: Gasifier inlet: coal 23.6 Kg/s (667 MJ/s), steam 16.44 kg/s; Reactor reforming gas: 30.0, 8.7, 2.0, 0.8, 0.3, 0.05, 0.24, 0.14, 0.1 and 5.5 kg/s for CO, CO2 , H2 , CH4 , C2 H4 , C2 H6 , C3 H6 , HCN, N2 and H2 O respectively. The projected power outputs with this system were, SOFC: 214 MW; Gas turbine: 318 MW; Steam turbine: 86 MW.Copyright

Development of general-purpose software to analyze the steady state of power generation systems

Abstract It is important to improve the power generation efficiency of thermal power generation while promoting the location of nuclear power generation to reduce discharge of carbon dioxide from the power generation plants. Software, which effectively examines the performance of the power generation system of various configurations, can contribute to the development of a highly effective, excellent in environmental thermal power generation systems. For this purpose, authors developed a new method to calculate the steady state of power generation systems, such as heat and mass balance, efficiencies, etc. This method is very flexible in calculation condition setting. Then we developed a general-purpose software by which the steady state behavior of the power generation system is analyzed easily.

Energy Flow of Advanced IGCC With CO2 Capture Option

Conventional IGCC (integrated gasification combined cycle) employs a cascaded energy flow with a high efficiency, yet it is difficult to achieve over 50% HHV (higher heating value). The current study proposes an alternative model of exergy recuperated Advanced IGCC (A-IGCC) to achieve higher plant efficiency by applying an autothermal reaction in the gasifier. This requires an additional heat supply from the gas turbine exhaust and the steam extracted from the steam turbine. System and performance analyses were studied on base IGCC and A-IGCC cases incorporating the heat (exergy) recuperation concept with an air-blown twin circulating fluidized bed gasifier for the gasification of sub-bituminous coal, both with and without the post combustion carbon dioxide (CO2 ) capture option. A-IGCC could deliver sufficient energy in the gasifier to the gas turbine without losing heat as resulted in IGCC. Chemical absorption methods using monoethanolamine (MEA) and methyldiethanolamine (MDEA) were selected as a CO2 absorbent. A-IGCC demonstrated a significantly higher system efficiency (51%) than IGCC (43%) without CO2 separation, provided the gas purification was at high temperature. The thermal efficiency penalty by CO2 capture was −8% using MDEA (56% absorption) and −11% using MEA (90% absorption).Copyright

MCFC-GT Hybrid System Aiming at 70% Thermal Efficiency

The thermal efficiency improvement of fossil power generation is important to reduce both CO2 emission and power generating cost. To date, 60% (LHV) has been achieved with ACC (A dvanced C ombined C ycle) and a calculation result of 70% (LHV) or more has been reported for SOFC-GT hybrid. Then, we examined the thermal efficiency improvement considering the features of the gas turbine and the fuel cell, and designed the epoch-making cycle. By markedly improving the single-cell voltage of MCFC using oxygen as an oxidant, and having adopted a semiclosed cycle configuration in which gas turbine exhaust heat is effectively used almost completely, this cycle not only enables us to obtain an ultrahigh efficiency, but also can facilitate CO2 recovery. First, the thermal efficiency of a 300MW-class power plant using this cycle was examined, and it was confirmed that a net efficiency of 70% (HHV) or more was possible. Then, a 1MW-class system that can be realized in the near future is examined. As a result, it has been understood that it is promising as a small power supply, too. In this paper, the concept and basic configuration of this cycle were explained, and the detailed configuration and the thermal efficiency calculation results for both the 300MW-class system and the 1MW-class system are described.Copyright

Conceptual Design and Cooling Blade Development of 1700 °C-Class High-Temperature Gas Turbine

This paper describes the conceptual design and cooling blade development of a 1700 °C-class high-temperature gas turbine in the ACRO-GT-2000 (Advanced Carbon Dioxide Recovery System of Closed-Cycle Gas Turbine Aiming 2000K) project. In the ACRO-GT closed cycle power plant system, the thermal efficiency aimed at is more than 60% of higher heating value of fuel (HHV). Because of the high thermal efficiency requirement, the 1700 °C-class high-temperature gas turbine must be designed with the minimum amount of cooling and seal steam consumption. The hybrid cooling scheme, which is a combination of closed loop internal cooling and film ejection cooling, was chosen from among several cooling schemes. The elemental experiments and numerical studies, such as those on blade surface heat transfer, internal cooling channel heat transfer and pressure loss and rotor coolant passage distribution flow phenomena, were conducted and the results were applied to the conceptual design advancement. As a result, the cooling steam consumption in the first stage nozzle and blade was reduced by about 40% compared with the previous design that was performed in the WE-NET (World Energy Network) Phase-I.Copyright

Study on the High Efficiency Closed Cycle Gas Turbine System

In WE-NET project Phase I Program, the power generation system with more than 60%(HHV) thermal efficiency had been designed. However, because this system must be fueled by pure hydrogen, commercialization of this system in early stage is thought to be difficult. Therefore, the new project, in which the natural gas fueled system is targeted, has been started since FY1999. In this project, the power generation efficiency is aimed to be 60%(HHV) or higher, with turbine inlet maximum temperature of 1973K. In this report, the feature of the target system is explained at first. Then, the sensitivities of many parameters are examined in detail.© 2001 ASME