Chemically Recuperated Gas Turbine Research Articles

Suitability Evaluation of Steam-Reforming Catalyst for DME-Fueled Chemically Recuperated Gas Turbine System

Dimethyl ether (DME), which is attracting attention as an alternative fuel for versatile use, has been tried to apply to the Chemically Recuperated Gas Turbine (CRGT), since DME steam-reforming that occurs at temperatures below 350°C with endothermic reaction is suitable for chemical heat recovery and leads to enhancement of power generation efficiency and power output. One of important concerns for the DME-fueled CRGT is related to catalyst reactions in the heat recovery reformer that is a key component of the system because exothermic reactions such as methanation and CO shift disturb the chemical heat recovery. Almost 30 kinds of precious metal-based catalyst were screened using the pressurized reformer to find the most suitable candidate for the CRGT from the viewpoint of LHV increase of the reformed gas. The selected candidate of catalyst was also tested with various temperature, steam/DME molar ratios (S/DME) and pressures. The result indicated that T= 450°C and S/DME = 3.5 was an appropriate condition for the reasons of the balance between endothermic and exothermic reaction rates and carbon deposition. The catalyst was also available for the pressure range up to 2.1 MPa in a MW class GT system without significant decrease of chemical heat recovery.

Performance evaluation of chemically recuperated gas turbine (CRGT) power plants fuelled by di-methyl-ether (DME)

This paper reports a performance analysis on CRGT power plants fuelled by DME, which is a potentially attractive fuel for gas turbines. The study also includes a performance comparison of simple cycle gas turbines fuelled by natural gas, DME and methanol. The study shows that, owing to the exhaust heat recovery carried out through DME pre-heating and vaporization before combustion, the efficiency of the DME fuelled turbine improves by about 1 point, without any significant change in power output. Thermochemical recuperation in DME fuelled turbines allows to achieve a significant performance improvement. For the highest water/DME molar ratio allowed by the minimum temperature difference here assumed, the power output of the CRGT plant is 44% higher than that of the reference plant, with a corresponding 54% efficiency (versus 41% of the reference unit) and a 8% decrease of the specific CO 2 emissions.

A Study on Principal Component for Chemically Recuperated Gas Turbine with Natural Gas Steam Reforming (1st Report, System Characteristics of CRGT and Design of Reformer)

Small-and-medium-sized gas turbines widely spread for distributed power and combined heat and power. However, most of their generating efficiencies are less than 35% because of simple cycle. Chemically recuperated gas turbine (CRGT) is an advanced cycle, which recovers exhaust heat by endothermic reaction converting fuel into hydrogen-rich gas, and several papers report that CRGT would be effective to improve generating efficiency of the simple cycle GT in feasibility study. Also, the CRGT using methanol steam reforming has been demonstrated, but the components and system operation has not been assessed technically in case of natural gas. In order to realize the CRGT with natural gas steam reforming, we applied the CR system to a commercial 4 MW simple cycle GT and surveyed effects of several parameters on the static mass and heat balance. On the basis of typical mass and heat balance, we also designed a heat recovery reformer by numerical analysis considering mass and heat transfer and chemical reaction.

B304 Development of Components for Chemically Recuperated Gas Turbine with Natural Gas Steam-Reforming

Small and medium size gas turbines are widely used for distributed power and combined heat and power. However, most have power generation efficiency of less than 35% because of the simple cycle. A chemically recuperated gas turbine (CRGT) has an advanced cycle, which recovers exhaust heat by endothermic reaction converting fuel into hydrogen-rich gas. Several papers report that the results of feasibility studies indicate CRGT would be effective for improving power generation efficiency of the simple cycle GT. Also, the CRGT using methanol steam reforming has been demonstrated, but the components and system operation have not been assessed technically in the case of natural gas. In order to realize the CRGT with natural gas steam reforming, we applied the CR system to a commercial 4MW simple cycle GT and examined the static mass and heat balance by process simulator. We designed a reformer consisting of tube bundles by numerical analysis, which considered mass and heat transfer and chemical reaction in the catalyst bed and clarified the master plan figure of the heat recovery system. Also, the reformer was structurally analyzed using FEM and the stresses due to internal pressure, gravity and temperature distribution were calculated and the stresses in the cross section under severe condition were evaluated with ASME code. This paper presents the results and discussions of these studies.

Membrane systems for CO2 capture and their integration with gas turbine plants

The capture and sequestration of the CO2 emitted from fossil-fuelled power plants is gaining widespread interest for controlling anthropogenic emissions of greenhouse gases. Among technology options for CO2 capture, membrane-based gas separation systems are noteworthy owing to their low energy requirements, promising technology evolution and effective integration with power plants. This paper presents a mathematical model for membrane-based separation systems that is able to cover the most significant membrane types and configurations. This model has been integrated in a general simulation method for analysing and optimizing advanced energy conversion systems. Performance of these simulation tools is demonstrated by evaluating the influence of different operating conditions on the behaviour of pre-and post-combustion separation units, based on metallic or polymeric membranes. Finally, the feasibility of integrating a metallic membrane system into a chemically recuperated gas turbine (CRGT) power plant is explored, obtaining encouraging results for CO2 capture.

Development of Chemically Recuperated Micro Gas Turbine

Micro gas turbines (MGTs) are subject to certain problems, notably low thermal efficiency of the system and high emission including NOx. The chemically recuperated gas turbine (CRGT) system introduced in this paper is one of the most promising solutions to these problems. The CRGT system we propose uses an endothermic reaction of methane steam reforming for heat recovery. It is usually thought that the reaction of methane steam reforming does not occur sufficiently to recover heat at the temperature of turbine exhaust, but we confirmed sufficient reaction occurred at such low temperature and that applications of the chemical recuperation system to some commercial MGTs are effective for increasing the efficiency.

Thermodynamic analysis of chemically recuperated gas turbines

Significant research effort is currently centred on developing advanced aero-derivative gas turbine systems for electric power generation applications, in particular for intermediate duty operation. Compared to industrial gas turbines, aero-derivatives offer high simple cycle efficiency, a quick and frequent start capability without significant maintenance cost penalty. A key element for high system performance (efficiency and power output) is the development of improved heat recovery systems, leading to advanced cycles such as the STeam Injected Gas Turbine (STIG) cycle, Humid Air Turbine (HAT) cycle or the Chemically Recuperated Gas Turbine (CRGT) cycle. In this paper the chronology of development of this last technology and a detailed description of our research program “Thermodynamic analysis of chemically recuperated gas turbines” is presented. A comparative study of the performance potentials of CRGT cycles and the other advanced cycles for design and off-design mode is presented. The analysis method accounts for turbine blade cooling requirements, which have a decisive impact on cycle performance. Exergy calculations are included in the analysis method. Research perspectives for this technology are suggested.

Modular approach to analysis of chemically recuperated gas turbine cycles

Current research programmes such as the CAGT programme investigate the opportunity for advanced power generation cycles based on state-of-the-art aeroderivative gas turbine technology. Such cycles would be primarily aimed at intermediate duty applications. Compared to industrial gas turbines, aeroderivatives offer high simple cycle efficiency, and the capability to start quickly and frequently without a significant maintenance cost penalty. A key element for high system performance is the development of improved heat recovery systems, leading to advanced cycles such as the humid air turbine (HAT) cycle, the chemically recuperated gas turbine (CRGT) cycle and the Kalina combined cycle. When used in combination with advanced technologies and components, screening studies conducted by research programmes such as the CAGT programme predict that such advanced cycles could theoretically lead to net cycle efficiencies exceeding 60%. In this paper, the authors present the application of the modular approach to cycle simulation and performance predictions of CRGT cycles. The paper first presents the modular simulation code concept and the main characteristics of CRGT cycles. The paper next discusses the development of the methane–steam reformer unit model used for the simulations. The modular code is then used to compute performance characteristics of a simple CRGT cycle and a reheat CRGT cycle, both based on the General Electric LM6000 aeroderivative gas turbine.

Design issues and performance of a chemically recuperated aeroderivative gas turbine

A number of innovative gas turbine cycles have been proposed lately, including the humid air turbine (HAT) and the chemically recuperated gas turbine (CRGT). The potential of the CRGT cycle lies in the ability to generate power with a high efficiency and ultra-low NOx emissions. Much of the research work published on the CRGT cycle is restricted to an analysis of the thermodynamic potential of the cycle. However, little work has been devoted to discussion of some of the relevant design and operation issues of such cycles. In this paper, part-load performance characteristics are presented for a CRGT cycle based on an aeroderivative gas turbine engine adapted for chemical recuperation. The paper also includes discussion of some of the design issues for the methane-steam reformer component of the cycle. The results of this study show that large heat exchange surface areas and catalyst volumes are necessary to ensure sufficient methane conversion in the methane steam reformer section of the cycle. The paper also shows that a chemically recuperated aeroderivative gas turbine has similar part-load performance characteristics compared with the corresponding steam-injected gas turbine (STIG) cycle.