Hiromi Koizumi

Performance of a Multiple-Injection Dry Low NOx Combustor With Hydrogen-Rich Syngas Fuels

An oxygen-blown integrated coal gasification combined cycle (IGCC) plant with precombustion carbon dioxide capture and storage (CCS) is one of the most promising means of zero-emission generation of power from coal. In an IGCC plant with CCS, hydrogen-rich syngas with a wide variation of hydrogen contents is supplied to a gas turbine. Such hydrogen-rich syngas poses a great challenge to a low NOx combustor based on premixed combustion technology, because its high flame speed, low ignition energy, and broad flammability limits can cause flashback and/or autoignition. On the contrary, a diffusion combustor suffers from the high flame temperature of syngas and the resulting high NOx emission. The authors applied a “multi-injection burner” concept to a preliminary burner for hydrogen-rich syngas simulating that from IGCC with CCS. In a preliminary experiment under atmospheric pressure, the multi-injection burner worked without any flashback or any blowout. A prototype multicluster combustor based on the results of that preliminary study was made to be a dry low NOx combustor for hydrogen-rich syngas of IGCC with CCS. It was tested in experiments, which were carried out under medium pressure (0.6 MPa) using test fuels simulating syngas from IGCC with a 0% carbon capture rate, a 30% carbon capture rate, and a 50% carbon capture rate. The test fuels contained hydrogen, methane, and nitrogen, and had a hydrogen content ranging from 40% to 65%.The following conclusions were drawn from the test results: (1) the tested combustor allows the stable combustion of fuels simulating 0%, 30%, and 50% CCS, (2) a convex perforated plate swirler is effective to suppress combustion oscillation, which allows NOx emissions to be less than 10 ppm through the variation of fuel simulating 0%, 30%, and 50% CCS, (3) the extended stable combustion region and enhanced entrainment and mixing due to the convex perforated plate improves the cooling of the combustor liner metal to be less than the liner metal temperature criterion.

Development of Low NOx Combustion Technology in Medium-Btu Fueled 1300°C-Class Gas Turbine Combustor in an Integrated Coal Gasification Combined Cycle

The development of integrated coal gasification combined cycle (IGCC) systems ensures higher thermal efficiency and environmentally sound options for supplying future coal utilizing power generation needs. The Japanese government and electric power industries in Japan promoted research and development of an IGCC system using an air-blown entrained-flow coal gasifier. On the other hand, Europe and the United States are now developing the oxygen-blown IGCC demonstration plants. Gasified coal fuel produced in an oxygen-blown entrained-flow coal gasifier has a calorific value of 8-13 MJ/m 3 which is only 1/5-1/2 that of natural gas. However, the flame temperature of medium-Btu gasified coal fuel is higher than that of natural gas and so NO x production from nitrogen fixation is expected to increase significantly. In the oxygen-blown IGCC, a surplus nitrogen produced in the air-separation unit (ASU) is premixed with gasified coal fuel (medium-Btu fuel) and injected into the combustor, to reduce thermal-NO x production and to recover the power used for the ASU. In this case, the power to compress nitrogen increases. Low NO x emission technology which is capable of decreasing the power to compress nitrogen is a significant advance in gas turbine development with an oxygen-blown IGCC system. Analyses confirmed that the thermal efficiency of the plant improved by approximately 0.3% (absolute) by means of nitrogen direct injection into the combustor, compared with a case where nitrogen is premixed with gasified coal fuel before injection into the combustor. In this study, based on the fundamental test results using a small diffusion burner and a model combustor, we designed the combustor in which the nitrogen injection nozzles arranged on the burner were combined with the lean combustion technique for low-NO x emission. In this way, we could reduce the high-temperature region, where originated the thermal-NO x production, near the burner positively. And then, a combustor with a swirling nitrogen injection function used for a gas turbine, was designed and constructed, and its performance was evaluated under pressurized conditions of actual operations using a simulated gasified coal fuel. From the combustion test results, the thermal-NO x emission decreased under 11 ppm (corrected at 16% O 2 ), combustion efficiency was higher than 99.9% at any gas turbine load. Moreover, there was different effects of pressure on thermal-NO x . emission in medium-Btu fuel fired combustor from the case of a natural gas fired combustor.

Effects of Multiple-Injection-Burner Configurations on Combustion Characteristics for Dry Low-NOx Combustion of Hydrogen-Rich Fuels

The successful combination of coal-based integrated gasification combined cycle (IGCC) technology with carbon dioxide (CO2 ) capture and storage (CCS) requires gas turbines that can achieve dry low-NOx combustion of hydrogen-rich syngas with a wide range of hydrogen concentrations for lower emissions and higher plant efficiency. The authors have been developing a “multiple-injection burner” to achieve dry low-NOx combustion of such hydrogen-rich fuels. The purpose of this paper is to experimentally investigate the combustion characteristics of a multiple-injection burner with a convex perforated plate in order to determine its effectiveness in suppressing combustion oscillation. The experiments were conducted at atmospheric pressure. Three kinds of fuel with hydrogen concentrations ranging from 40 to 84% were tested. The temperature of the combustion gas at the burner exit was 1775 K. The experimental results show that the convex burner was effective in suppressing combustion oscillation: it achieved stable low-NOx emissions of less than 10 ppm for all the test fuels. These findings demonstrate that the convex burner can achieve stable low-NOx combustion of hydrogen-rich fuels with a wide range of hydrogen concentrations by suppressing combustion oscillation.Copyright

Applicability of a Multiple-Injection Burner to Dry Low-NOx Combustion of Hydrogen-Rich Fuels

To demonstrate the applicability of a “multiple-injection burner” to dry low-NOx combustion of hydrogen-rich fuels, the combustion characteristics of a burner were experimentally investigated. The experimental results show that a burner with a flame lift-off length of 5 mm and a fuel-injection-hole diameter of 1.5 mm achieves low NOx concentration of less than 6 ppm for hydrogen-rich fuels with a wide range of hydrogen concentrations. This finding demonstrates that the burner achieves dry low-NOx combustion of these hydrogen-rich fuels without need for any modification of the burner’s configuration. Moreover, it was found that fuel distribution, fuel composition, flame lift-off length, and fuel-jet velocity have significant effects on the burners’ combustion characteristics.Copyright

Robust Design of the Coaxial Jet Cluster Nozzle Burner for DME (Dimethyl Ether) Fuel

DME (dimethyl ether) is currently attracting worldwide attention due to its potential as a clean fuel. But, DME has a low auto-ignition temperature and a higher combustion velocity compared with other power generation gas fuels (LNG, LPG). Therefore, in the case of lean-premixed design to limit the formation of NOx in the burning zone, a shorter premixing length than that for natural gas is required. In this research, the main objective is the development of a low NOx emission and high efficiency combustion system that is suited to quick and uniform mixing between the air and gaseous DME. A coaxial jet cluster nozzle burner configuration is proposed as the low NOx combustion system, and 18 different configuration burners are designed and tested by the robust design. Based on the analysis of test results, the optimized configuration of a coaxial jet nozzle burner is selected.Copyright

Development of Low NOx Combustion Technology in Medium-Btu Fueled 1300 °C-Class Gas Turbine Combustor in IGCC

The development of integrated coal gasification combined cycle (IGCC) systems ensures higher thermal efficiency and environmentally sound options for supplying future coal utilizing power generation needs. The Japanese government and electric power industries in Japan promoted research and development of an IGCC system using an air-blown entrained-flow coal gasifier. On the other hand, Europe and the United States are now developing the oxygen-blown IGCC demonstration plants.Gasified coal fuel produced in an oxygen-blown entrained-flow coal gasifier, has a calorific value of 8–13MJ/m3 which is only 1/5–1/3 that of natural gas. However, the flame temperature of medium-Btu gasified coal fuel is higher than that of natural gas and so NOx production from nitrogen fixation is expected to increase significantly. In the oxygen-blown IGCC, a surplus nitrogen produced in the air-separation unit (ASU) is premixed with gasified coal fuel (medium-Btu fuel) and injected into the combustor, to reduce thermal-NOx production and to recover the power used for the ASU. In this case, the power to compress nitrogen increases. Low NOx emission technology which is capable of decreasing the power to compress nitrogen is a significant advance in gas turbine development with an oxygen-blown IGCC system. Analyses confirmed that the thermal efficiency of the plant improved by approximately 0.3 percent (absolute) by means of nitrogen direct injection into the combustor, compared with a case where nitrogen is premixed with gasified coal fuel before injection into the combustor.In this study, based on the fundamental test results using a small diffusion burner and a model combustor, we designed the combustor in which the nitrogen injection nozzles arranged on the burner were combined with the lean combustion technique for low-NOx emission. In this way, we could reduce the high temperature region, where originated the thermal-NOx production, near the burner positively. And then, a combustor with a swirling nitrogen injection function used for a gas turbine, was designed and constructed, and its performance was evaluated under pressurized conditions of actual operations using a simulated gasified coal fuel. From the combustion test results, the thermal-NOx emission decreased under 11ppm (corrected at 16% O2), combustion efficiency was higher than 99.9% at any gas turbine load. Moreover, there was different effects of pressure on thermal-NOx emission in medium-Btu fuel fired combustor from the case of natural gas fired combustor.Copyright

Combustion Characteristics of a Multiple-Injection Combustor for Dry Low-NOx Combustion of Hydrogen-Rich Fuels Under Medium Pressure

An oxygen-blown integrated coal gasification combined cycle (IGCC) plant with pre-combustion carbon dioxide capture and storage (CCS) is one of the most promising means of zero-emission generation of power from coal. In an IGCC plant with CCS, hydrogen-rich syngas with a wide variation of hydrogen contents is supplied to a gas turbine. Such hydrogen-rich syngas poses a great challenge to a low NOx combustor based on premixed combustion technology, because its high flame speed, low ignition energy, and broad flammability limits can cause flashback and / or auto-ignition. On the other hand, a diffusion combustor suffers from the high flame temperature of syngas and the resulting high NOx emission. The authors applied a “multi-injection burner” (cluster burner) concept to a preliminary burner for hydrogen-rich syngas simulating that from IGCC with CCS. In a preliminary experiment under atmospheric pressure, the multi-injection burner worked without any flashback or any blowout. A prototype multi-cluster combustor based on the results of that preliminary study was made to be a dry low NOx combustor for hydrogen-rich syngas of IGCC with CCS. It was tested in experiments, which were carried out under medium pressure (0.6MPa) using test fuels simulating syngas from IGCC with a 0% carbon capture rate, a 30% carbon capture rate and a 50% carbon capture rate. The test fuels contained hydrogen, methane and nitrogen, and had hydrogen content ranging from 40% to 65%. The following conclusions were drawn from the test results: (1) The tested combustor allows stable combustion of fuels simulating 0%, 30%, and 50% CCS. (2) A convex perforated plate swirler is effective to suppress combustion oscillation, which allows NOx emissions to be less than 10ppm through the variation of fuel simulating 0%, 30% and 50% CCS.Copyright

Effects of Fuel-Nozzle Configurations on Particulate-Matter Emissions From a Model Gas Turbine Combustor

The present paper describes particulate-matter (PM) emissions from a model gas turbine combustor at atmospheric pressure, focusing on the effects fuel-nozzle configurations have on PM emissions. In this experiment, three types of fuel nozzles were employed: standard, annular, and multi-type. The annular and multi-type were designed as low-PM-emission fuel nozzles, based on our preliminary experimental results using the standard nozzle. Gas oil and fuel oil containing 0.2 wt% of carbon residue were used as the test fuels. The PM concentrations and particle-size distributions were measured with an electrical low-pressure impactor. The experimental results revealed that the PM concentrations for the annular and multi-type were dramatically reduced compared with that for the standard nozzle, demonstrating their PM-reducing effect. We found that the high-concentration regions seemed to be formed by soot aggregation, from the spatial-profile measurements of PM emissions from gas oil combustion. The high-concentration regions for the low-PM-emission fuel nozzles were located further upstream and they were on a smaller scale than that for the standard nozzle. This suggests that their PM-reducing effect may be due to their upstream location and the smaller-scale of their high-concentration regions.Copyright

The Effect of Impurities in Fuel Grade Dimethyl-Ether on Combustion Characteristics

In order to investigate the effect of impurities contained in fuel grade dimethyl-ether on combustion characteristics, laminar burning velocity tests and diffusion flame combustor tests were carried out with various contents of impurities in fuel grade dimethyl-ether (with about 0–9wt% methanol and 0–10wt% moisture). From the laminar burning velocity tests, it was found that the burning velocity of fuel grade dimethyl-ether was slightly slower than that of high purity dimethyl-ether and it was faster than that of methane. This indicates that fuel grade dimethyl-ether has a high potential of flash back, like high purity dimethyl-ether. Moreover, the diffusion flame combustor tests showed that NOx emission decreased when the impurities contained in fuel grade dimethyl-ether were increased, however CO emissions were almost constant, irrespective of the content of impurities. Further, by comparing NOx emissions with various contents of impurities in fuel grade dimethyl-ether, it was clear that NOx emissions could be estimated from the adiabatic flame temperature. From these results, a lot of valuable data regarding impurities content has been obtained, which will assist in the development of a gas turbine combustor for fuel grade dimethyl-ether.Copyright