Mitsubishi Hitachi Power Systems Research Articles

Thermodynamic Analysis of Air-Blown Staged Gasification of Coal in a Flow

One of the ways to environmentally friendly use coal is an integrated gasification combined cycle. The most common oxidizing agent employed in gasification is oxygen. It is feasible to use air instead of oxygen to reduce the cost of generated electricity. The air gasification downsides can be reduced by using heated air and organizing a staged process. The paper is concerned with a thermodynamic analysis of the MHPS (Mitsubishi Hitachi Power Systems) air-blown staged gasifier. The analysis relies on an original approach that suggests investigating experimental data on a set of calculated ones. The experimental run nears the thermodynamic optimum, which coincides with the carbon boundary line. Cold gas efficiency can be increased from 78.6 to 81.5% by reducing the equivalence ratio. Thus, the temperature will decrease from 1 200 to 1 100 °C. The experimental run of the MHPS gasifier is not optimal thermodynamically, but it is probably optimal kinetically. The fact is that the rates of heterophase reactions decline near the carbon boundary, which leads to a sharp increase in fuel underburning and a decrease in efficiency. The experimental run is also located close to the region with the maximum thermal efficiency of the process, which is indicative of the high efficiency of converting air heat into chemical energy of producer gas.

Mitsubishi to work on CO2 to methanol

Three Mitsubishi companies are teaming up to research converting CO2 into methanol. Mitsubishi Hitachi Power Systems is leading the effort, joined by Mitsubishi Heavy Industries Engineering and Mit...

Study on Coal Syngas Applicability to SOFC Module

Solid oxide fuel cells (SOFCs) are expected to be applied to Integrated Coal Gasification Fuel Cell Combined Cycle (IGFC). However, most SOFC modules are designed with natural gas as fuel that means SOFC modules are cooled using the internal reforming reaction (endothermic reaction) of natural gas. In this research, a modified SOFC module manufactured by Mitsubishi Hitachi Power Systems, Ltd. (MHPS) was installed and power generation performance with assumed gas was verified. As a result, it was confirmed that the output of SOFC module was reduced by changing the fuel from natural gas to assumed coal gas. On the other hand, improvement of SOFC performance was possible by changing the operating conditions. In this paper, operation test results are introduced.

MHPS wins first order for integrated SOFC/gas turbine hybrid unit

Japanese power generation giant Mitsubishi Hitachi Power Systems (MHPS) has received the first order for its pressurised hybrid power generation system that integrates solid oxide fuel cell (SOFC) stacks with micro gas turbines (MGTs). This system, launched for the commercial and industrial market, is being installed in the Marunouchi Building in Tokyo.

MHPS launches new integrated SOFC-gas turbine hybrid system

In Japan, Mitsubishi Hitachi Power Systems Ltd (MHPS) has launched a new pressurised hybrid power generation system that integrates solid oxide fuel cell (SOFC) stacks with micro gas turbines (MGTs).

Techno-Economic Analysis of a Secondary Air Stripper Process

We present results of an initial techno-economic assessment on a post-combustion CO2 capture process developed by the Center for Applied Energy Research (CAER) at the University of Kentucky using Mitsubishi Hitachi Power Systems’ H3-1 aqueous amine solvent. The analysis is based on data collected at a 0.7 MWe pilot unit combined with laboratory data and process simulations. The process adds a secondary air stripper to a conventional solvent process, which increases the cyclic loading of the solvent in two ways. First, air strips additional CO2 from the solvent downstream of the conventional steam-heated thermal stripper. This extra stripping of CO2 reduces the lean loading entering the absorber. Second, the CO2-enriched air is then sent to the boiler for use as secondary air. This recycling of CO2 results in a higher concentration of CO2 in the flue gas sent to the absorber, and hence a higher rich loading of the solvent exiting the absorber.A process model was incorporated into a full-scale supercritical pulverized coal power plant model to determine the plant performance and heat and mass balances. The performance and heat and mass balance data were used to size equipment and develop cost estimates for capital and operating costs. Lifecycle costs were considered through a levelized cost of electricity (LCOE) assessment based on the capital cost estimate and modeled performance.The results of the simulations show that the CAER process yields a regeneration energy of 3.12 GJ/t CO2, a $53.05/t CO2 capture cost, and LCOE of $174.59/MWh. This compares to the U.S. Department of Energy's projected costs (Case 10) of regeneration energy of 3.58 GJ/t CO2, a $61.31/t CO2 capture cost, and LCOE of $189.59/MWh. For H3-1, the CAER process results in a regeneration energy of 2.62 GJ/tCO2 with a stripper pressure of 5.2bar, a capture cost of $46.93/t CO2, and an LCOE of $164.33/MWh.

Development of High-efficiency Oxy-fuel IGCC System

As reported in GHGT-12, CRIEPI engaged in NEDO project to develop CO2 capture IGCC system, whose efficiency is more than 42%(HHV), as joint project with Kyushu University since 2008. In this system, exhaust gas is recirculated to gasifier and gas turbine combustor, just as oxy-fuel combustion boiler. In 2015, CRIEPI started 2nd phase 5 years’ NEDO project with assistance of Mitsubishi Heavy industries and Mitsubishi Hitachi Power Systems. In this phase, MHI uses 50TPD gasifier and 1/3 scaled GT combustion test stand to obtain data to design large scale plant. On the other hand, CRIEPI modify its 3TPD gasifier to clarify O2/CO2 gasification performance. In addition, hot gas clean-up system will be examined in above 2 gasifiers. CRIEPI install exhaust gas recirculation unit to clarify fundamental characteristics of semi-closed cycle gas turbine. This paper is to show the progress after GHGT-12 and whole picture of 2nd phase project by CRIEPI.

KM CDR ProcessTM Project Update and the New Novel Solvent Development

The Petra Nova Project will be the world's largest post combustion CO2 capture plant on coal fired flue gas once it begins operation expected in the 4th Quarter of 2016. The CO2 capture plant uses MHI's KM CDR ProcessTM which has been in development by Mitsubishi Heavy Industries, Ltd. (MHI) in collaboration with the Kansai Electric Power Co., Inc. (KEPCO) since 1990 and has been refined through the application of lessons learned from other commercial plants and R&D projects. MHI continues to improve its technology by focusing on developing more efficient systems and reducing CO2 capture costs. MHI demonstrated a 25 MW heat integration technology using (Mitsubishi Hitachi Power Systems Ltd.) MHPS's High Efficiency System (HES) with Southern Company Services. The project resulted in significant heat recovery and improvements in pollutant capture performance in the electrostatic precipitator (ESP). MHI also evaluated the performance of a new, novel solvent at a 2 tpd pilot test plant in Japan. The pilot test results show lower steam consumption, solvent degradation, and solvent emissions than those of KS-1TM solvent. MHI plans to continue developing the new solvent until it is ready for commercial deployment. Through R&D and through the collection of lessons learned from commercial plants, MHI is working towards reducing the cost and the environmental footprint of CO2 capture.

New Applications of SOFC-MGT Hybrid Power Generation System for Low-Carbon Society

SOFC and micro gas turbine (MGT) hybrid power generation system in Fig.1 (a) is expected as a solution for energy saving and less CO2 emission. High temperature pressure swing absorption (HT-PSA) in Fig.1 (b) is also expected as an efficient method for pure O2 production. Applying HT-PSA to the pressurized high-temperature cathode off-gas of SOFC-MGT hybrid system, we are able to obtain pure O2 more efficiently than the other conventional method. Using obtained O2 for anode off-gas oxidation, we can easily capture CO2, which leads to effective carbon-less or negative-carbon solution. Produced O2 are also useful for efficient gasification, which leads to CO2-capture IGFC system. In this study, we performed basic performance tests of SOFC-MGT and HT-PSA systems. Using these results, we also studied expecting performance and technical issues of proposed SOFC application systems. Acknowledgements This research is supported by The Japan Science and Technology Agency (JST) through its “Center of Innovation Science and Technology based Radical Innovation and Entrepreneurship Program (COI Program)" and Mitsubishi Hitachi Power Systems(MHPS) Co., Ltd. Figure 1

Degradation Analysis of SOFC Stack Performance: Investigation of Cathode Sulfur Poisoning Due to Contamination in Air

Central Research Institute of Electric power Industry (CRIEPI) has operated seven types of SOFC stacks, which are developed by MITSUBISHI HITACHI POWER SYSTEMS (MHPS), KYOCERA, TOTO, NGK SPARK PLUG (NTK), NGK INSULATORS (NGK), MURATA Manufacturing (Murata), and Denso in order to investigate their durability and find dominant degradation factor for each SOFC stacks under NEDO’s project. In the first half of period, remarkable feature of durability tests was large cathode degradation in KYOCERA’s, NGK’s, and Murata’s cells which were examined at CRIEPI site. Because sulfur was detected on their cathodes from post analyses done by AIST with SIMS, in the last half of period, these stacks were reexamined by adopting sophisticated chemical filter for SO2 removal. Results become more acceptable. On the other hands, SO2 concentration in air at CRIEPI site was less than 3 ppbv. The amount of sulfur detected on cathode is significantly larger than that of calculated sulfur from supplied air, another sulfur sources might be considered.

Development of the Three-Tower Chemical Looping Coal Combustion Technology

To protect the environment changing, coal combustion must reduce its CO2 emission by capture and storage. Chemical looping is a potentially high technology for coal combustion with CO2 capture efficiently. A chemical-looping-combustion system, using circulating fluidized bed witch consist two main reactors, a fuel reactor and an air reactor. An oxygen carrier, typically a metal oxide, is employed to transfer oxygen from the air reactor to the fuel reactor, and circulates between these two reactors.During 2012-2014, JCOAL, MHPS (Mitsubishi Hitachi Power Systems (2012-2013 Babcock-Hitachi)) and IAE(The Institute of Applied Energy) have a project funded by NEDO (New Energy and Industrial Technology Development Organization) to surveyed chemical looping technology development in the world, studied market needs of chemical looping combustion, investigated carrier costs and reactivity, etc., in order to reduce CO2 separation recovery cost to 2,500 yen/ton of CO2 or less. A small-scale reactor was used to study the behaviors of the direct reaction of coal with an oxygen carrier. It was found that the coal conversion efficiency increases with increasing iron level in the carrier, that the volume of unreacted CO gas increases when oxygen use in the carrier exceeds the range of Fe2O3 --> Fe3O4, and that there is no notable surface melting that could obstruct particle circulation at 950̊C or less.A basic model of the CLC process was produced using the AspenPlus software and used to analyze the process under the conditions of a 250MWth plant. It found that the volume of circulating CLC carrier is roughly the same as the circulation of CFBC medium, and that inner desulfurization and ultra-low NOX combustion are possible.Using the results of research and process analysis, a three-tower chemical looping coal combustion technology that consists primarily of an air reactor (AR), coal reactor (CR), and volatiles reactor (VR) was selected, and an conceptual design was produced for the reactor configuration and technical parameters.

Degradation Analysis of SOFC Stack Performance: Investigation of Cathode Sulfur Poisoning Due to Contamination in Air

Central Research Institute of Electric power Industry (CRIEPI) has tested on seven types of SOFC stacks, which are developed by MITSUBISHI HITACHI POWER SYSTEMS (MHPS), KYOCERA, TOTO, NGK SPARK PLUG, NGK INSULATORS, MURATA, and Denso in order to reveal their durability and find dominant degradation factor for each SOFC stacks under NEDO’s project. Large degradation behaviors arising from SO2 in air have been observed in our site for the stacks of Kyocera’s, TOTO’s, NGK’s, and Murata’s. Therefore, the stacks were reexamined by adopting sophisticated chemical filter for SO2 removal, and a concentration of the sulfur in supplied air was measured. As results, acceptable degradation data have been obtained under the operation with chemical filter. Moreover, it was found that organic sulfur compound such as dimethyl sulfide almost comes through the physical filter and fed to their stack. In this study, we report our recent results on the durability and the change of degradation behaviors with chemical filter.

Mitsubishi Hitachi hybrid SOFC-MGTs in trials at Toyota, NGK

Mitsubishi Hitachi Power Systems (MHPS) is trialing 250 kW pressurised hybrid power generation systems that combine a tubular solid oxide fuel cell with a micro gas turbine (MGT), at two industrial plants in Japan. Automaker Toyota Motor Corporation has begun trial operations of a system at its Motomachi Plant in Toyota City, while NGK Spark Plug Co is now operating a system at its Komaki Factory, both in Aichi Prefecture, near Nagoya.

Degradation Analysis of SOFC Stack Performance-Durability Test and Verification of Improved SOFCs-

Central Research Institute of Electric power Industry (CRIEPI) has operated six types of SOFC stacks, which are developed by MITSUBISHI HITACHI POWER SYSTEMS (MHPS), KYOCERA, TOTO, NGK SPARK PLUG (NTK), NGK INSULATORS (NGK), and MURATA Manufacturing (Murata), in order to investigate their durability and find dominant degradation factor for each SOFC stacks under NEDO’s project. The MHPS’s stack which was operated until 18,000 hours, showed better stability and no further degradation factor has been identified. On the other hand, peculiar behaviors of cathode overvoltage degradation have been observed in some stacks at CRIEPI site. From post analyses, sulfur was detected on their cathode in some stacks. The large cathode degradation therefore seems to be caused by the sulfur impurity in air despite SO2 concentration in the suppling air is less than 2 ppbv. Therefore, the stacks which have been observed peculiar behavior were reexamined by adopting sophisticated chemical filter for SO2 removal, and acceptable data have been obtained.

Degradation Analysis of SOFC Stack Performance-Durability Test and Verification of Improved SOFCs-

Central Research Institute of Electric power Industry (CRIEPI) has operated six types of SOFC stacks, which are developed by MITSUBISHI HITACHI POWER SYSTEMS (MHPS), KYOCERA, TOTO, NGK SPARK PLUG, NGK INSULATORS, and MURATA, to reveal their durability and find dominant degradation factor for each SOFC stack under NEDO’s project. The target of this NEDO durability project is set at 0.11%/1,000hr. In order to evaluate a performance degradation of the SOFC quantitatively and in order to quantify a performance change with time, the performance factor analysis method is required. We have been developed the electrode polarization models which is able to express SOFC performance factors such as Nernst loss (ηne), anode polarization (ηa), cathode polarization (ηc), and internal resistance IR drop (ηiR) with high prediction accuracy for six types of SOFCs. This gives us enable to make detail comparison among different type of SOFCs with the same performance analysis method inside the NEDO project. The MHPS’s stack which was operated until 16,000 hours, showed better stability and no further degradation factor has been identified. On the other hand, peculiar degradation behaviors arising from some impurities in air have been observed in our test for the stacks of Kyocera’s, TOTO’s, NTK’s, NGK’s, and Murata’s. For example, performance test exibited a rapid voltage drop within initial operation period for flattened tubular segment-in-series stack. The factor of this rapid voltage drop was increment of cathode overvoltage from a performance factor analysis result. One of possible reason for the negative effect to cathode overvoltage is sulfur contamination in the supply air from air compressor or thermal insulating foam on furnace. In this study, we report our recent activities on the durability and the dominant performance factors, and the peculiar degradation behaviors.

Numerical investigation of firing concepts for a flexible Greek lignite-fired power plant

In the present work the behavior of a lignite boiler under both full and partial load conditions is investigated by means of CFD modeling. The simulated furnace is that of the Megalopolis Unit IV, a 300MWe power plant operated by Public Power Corporation S.A. (PPC) and located in Peloponnese, Southern Greece. Due to the extremely low quality lignite utilized in the particular power plant, a special system for dried lignite dust separation from vapors — composing of a) an additional vapor ESPs – partial vapor discharge and b) a dry lignite dust recirculation and firing system, is designed and operated in the particular boiler. Hence, pre-dried lignite is continuously used as the additional supporting fuel, through a special feeding, dosing and firing system along with separation and vapor discharge.Scope of the present work is the evaluation and optimization of different firing modes for the decrease of minimum load operation lower than 40%. The numerical analysis is focused on the induced flue gas flow field characteristics, associated with average exhibited temperature, main gas species concentrations, wall heat flux and particle burnout. The boundary conditions for partial load operation are provided by Mitsubishi Hitachi Power Systems Europe (MHPSE) and the basic design data of the furnace are provided by PPC S.A. In total, eight operating conditions are investigated corresponding to five boiler thermal loads, thus covering a wide range of thermal load operation. Furthermore, the boiler performance under different air and fuel distributions among the burners is also examined, in order to identify useful trends regarding the optimum conditions, under which a stable and safe furnace operation for very low load operation (less than 40%) can be assured. The CFD results are compared against design values provided by MHPSE. Finally, conclusions concerning the furnace membrane wall erosion and accretion rates under various operating configurations are derived, providing useful information about potential operating issues that could be expected, if the examined firing cases were applied. Finally, the case of a thermal load equal to 40% is of interest, for which a stable pulverized lignite flame can be achieved when two mills instead of three are operating.

Performance of Multiple-Injection Dry Low-NOx Combustors on Hydrogen-Rich Syngas Fuel in an IGCC Pilot Plant

The successful development of coal-based integrated gasification combined cycle (IGCC) technology requires gas turbines capable of achieving the dry low nitrogen oxides (NOx) combustion of hydrogen-rich syngas fuels for low emissions and high plant efficiency. Mitsubishi Hitachi Power Systems, Ltd. (MHPS) has been developing a “multiple-injection burner” to achieve the dry low-NOx (DLN) combustion of hydrogen-rich syngas fuels. The purposes of this paper are to present the test results of a multican combustor equipped with multiple-injection burners in an IGCC pilot plant, and evaluate combustor performance by focusing on the effects of flame shapes. The syngas fuel produced in the plant contained approximately 50% carbon monoxide, 20% hydrogen, and 20% nitrogen by volume. In the tests, the combustor with slenderer flames achieved lower NOx emissions of 10.9 ppm (at 15% oxygen), reduced combustor liner and burner plate metal temperatures, and lowered combustion efficiency at the maximum gas turbine load. The test results showed that the slenderer flames were more effective in reducing NOx emissions and liner/burner plate metal temperatures. A comparison with the diffusion-flame combustor demonstrated that the multiple-injection combustors achieved the dry low-NOx combustion of the syngas fuel in the plant.

Recent Progress of SOFC Combined Cycle System with Segmented-in-Series Tubular Type Cell Stack at MHPS

Mitsubishi Hitachi Power Systems, Ltd. (MHPS) is one of the first companies to focus on the potential of the Solid Oxide Fuel Cells (SOFC) as a component of large-scale power plant and has promoted segmented-in-series tubular type cell, the module and the system development since the 1980s. We are developing for commercialization of an SOFC-micro gas turbine (MGT) system from several hundred to several MW class. Recently prototype of a 250 kw class SOFC-MGT hybrid system was operated at Tokyo Gas Senju Techno Station. This system was very stable without voltage degradation at the rated for 4,100 hours. At the same time, we have started the development of fundamental technologies for realization of SOFC-Gas Turbine (GT)-Steam Turbine (ST) triple combined cycle system that aims to achieve more than 70% of power generation efficiency. We report the recent progress of the SOFC-micro gas turbine (MGT) hybrid system and development of triple combined cycle system.

Recent Progress of SOFC Combined Cycle System with Segmented-in-Series Tubular Type Cell Stack at MHPS

Solid oxide fuel cell (SOFC) triple combined cycle system, integrated with gas turbine (GT) and steam turbine (ST), is an ultimate fossil fuel electric power generation system with very high efficiency. Mitsubishi Hitachi Power Systems, Ltd. (MHPS) has been developing for commercialization of an SOFC-micro gas turbine (MGT) system from several hundred kW to several MW class. Recently prototype of a 250 kW class SOFC-MGT hybrid system was operated at Tokyo Gas Senju Techno Station. This system was stable without voltage degradation under operating 4,100 hours. At the same time, we have started the development of fundamental technologies for realization of SOFC-Gas Turbine (GT)-Steam Turbine (ST) triple combined cycle system that aims to achieve more than 70% of power generation efficiency. In this paper, recent progress of the SOFC-micro gas turbine (MGT) hybrid system and development of triple combined cycle system are described.

Performance Degradation Analysis of Different Type SOFCs

Long term durability tests of six different type SOFCs, which have been developed by Mitsubishi Hitachi Power Systems (MHPS), Kyocera, TOTO, NGK SPARK PLUG (NTK), NGK INSULATORS (NGK), and Murata Manufacturing (Murata) have been started under the New Energy and Industrial Technology Development Organization (NEDO) project from FY2013. 2012 model of the Kyocera’s stack which was operated until 10,000 hours, showed stability compared with 2008 model. The voltage decay rate was 0.2%/1000hr. The dominant degradation factors of this stack were IR drop and cathode overvoltage. 2012 model of the NTK’s stack showed that it has an initial voltage drop up to 1,000 hours and the degradation factors were IR drop and cathode overvoltage. The voltage decay rate was 0.6%/1000hr including thermal cycling. The stacks of MHPS’s, TOTO’s, NGK’s, and Murata’s were still in the middle of durability test. In this study, we report our recent activities toward the durability and the dominant performance factors, such as IR drop and overvoltage of anode and cathode, for the six types of SOFCs.