Development of a hybrid catalytic combustor for a 1300°C class gas turbine

The hybrid catalytic combustor concept proposed by the authors has an advantage concerned with catalyst durability, because the catalyst is maintained below 1000°C even for application to 1300°C class gas turbines. A full-scale hybrid catalytic combustor has been designed for a 200 MW (1300°C) class gas turbine. The catalyst bed was 450 mm in diameter and consisted of a Pd/ alumina washcoat on a cordierite monolith. In experiments, the combustor has demonstrated the capability of meeting the NO_x emission level of SCR (selected catalytic reduction) during atmospheric pressure testing. To predict the catalyst performance at an elevated pressure, the characteristics of the catalyst were studied using a small scale reactor test, and a material property test using a DTA/TGA-Q.MASS system. The catalyst showed a higher activity in the oxidized state (PdO) than in the metallic state (Pd). This activity difference was governed by the equilibrium of the oxygen release from PdO in bulk. It was considered that oxidation rate of the metallic Pd in bulk was not so high and this caused self-oscillation for the Pd catalyst around the temperature of the oxygen release equilibrium. Even below the temperature of the oxygen release equilibrium, both surface and bulk (lattice) oxygen of the PdO was consumed by the methane oxidation reaction, and resulted in a lack of surface oxygen on the catalyst. This caused a reversible decrease in the catalyst activity during combustion testing, and indicated that the oxygen dissociation step was a rate limiting step in the catalytic combustion.     

Development of a catalytically assisted combustor for a gas turbine

A catalytically assisted low NO_x combustor has been developed which has the advantage of catalyst durability. This combustor is composed of a burner section and a premixed combustion section behind the burner section. The burner system consists of six catalytic combustor segments and six premixing nozzles, which are arranged alternately and in parallel. Fuel flow rate for the catalysts and the premixing nozzles are controlled independently. The catalytic combustion temperature is maintained under 1000°C, additional premixed gas is injected from the premixing nozzles into the catalytic combustion gas, and lean premixed combustion at 1300°C is carried out in the premixed combustion section. This system was designed to avoid catalytic deactivation at high temperature and thermal or mechanical shock fracture of the honeycomb monolith. In order to maintain the catalyst temperature under 1000°C, the combustion characteristics of catalysts at high pressure were investigated using a bench scale reactor and an improved catalyst was selected for the combustor test. A combustor for a 20 MW class multi-can type gas turbine was designed and tested under high pressure conditions using LNG fuel. Measurements of NO_x, CO and unburned hydrocarbon were made and other measurements were made to evaluate combustor performance under various combustion temperatures and pressures. As a result of the tests, it was proved that NO_x emission was lower than 10 ppm converted at 16% O₂, combustion efficiency was almost 100% at 1300°C of combustor outlet temperature and 13.5 ata of combustor inlet pressure.     

Test results of a catalytic combustor for a gas turbine

A catalytically assisted low NO_x combustor has been developed which has the advantage of catalyst durability. Combustion characteristics of catalysts at high pressure were investigated using a bench scale reactor and an improved catalyst was selected. A combustor for multi-can type gas turbine of 10 MW class was designed and tested at high-pressure conditions using liquefied natural gas (LNG) fuel. This combustor is composed of a burner system and a premixed combustion zone in a ceramic type liner. The burner system consists of catalytic combustor segments and premixing nozzles. Catalyst bed temperature is controlled under 1000°C, premixed gas is injected from the premixing nozzles to catalytic combustion gas and lean premixed combustion is carried out in the premixed combustion zone. As a result of the combustion tests, NO_x emission was lower than 5 ppm converted at 16% O₂ at a combustor outlet temperature of 1350°C and a combustor inlet pressure of 1.33 MPa.     

Test results of a catalytically assisted combustor for a gas turbine

A catalytically assisted ceramic combustor for a gas turbine was designed and tested to achieve low NO_x emissions. This combustor is composed of a burner and a ceramic liner. The burner consists of an annular preburner, six catalytic combustor segments and six premixing nozzles, which are arranged in parallel and alternately. In this combustor system, catalytic combustion temperature is controlled under 1000 °C, premixed gas is injected from the premixing nozzles to the catalytic combustion gas and lean premixed combustion over 1300 °C is carried out in the ceramic liner. This system was designed to avoid catalyst deactivation at high temperature and thermal shock fracture of the ceramic honeycomb monolith of the catalyst. A 1 MW class combustor was tested using LNG fuel. Firstly, NO_x emissions from the preburner were investigated under various pressure conditions. Secondly, two sets of honeycomb cell density catalysts and one set of thermally pretreated catalysts ware applied to the combustor, and combustion tests were carried out under various pressure conditions. As a result, it was found that the main source of NO_x was the preburner, and total NO_x emissions from the combustor were approximately 4 ppm (at 16% O₂) at an adiabatic combustion temperature of 1350 °C and combustor inlet pressure of 1.33 MPa.     

Application of catalytic combustion to a 1.5 MW industrial gas turbine

A catalytic combustor is described for a 1.5 MW gas turbine engine. The catalyst temperature is limited and the high combustor outlet temperatures required by the turbine are generated downstream of the catalyst. The combustor design places a low NO_x preburner upstream of the catalyst and uses this preburner to achieve optimum catalyst operation by providing the desired catalyst inlet temperature. The combustor system employs the catalyst during engine acceleration and loading. The catalyst design has been tested on a sub-scale rig under full pressure and flow conditions simulating turbine operation over the entire operating range including acceleration and loading. The design should achieve emissions at full load operation of <3 ppm NO_x and <10 ppm CO and UHC. Low emissions operation is expected over the 75–100% load range. In addition, long-term sub-scale rig test results are reported at simulated full load operating conditions including cyclic operation and full load trips.     

Achieving ultra low emissions in a commercial 1.4 MW gas turbine utilizing catalytic combustion

The drive to achieve low emissions from gas turbines has been an ongoing challenge for over 30 years with the reduction of NO_x levels representing the most difficult issue. Catalytic combustion represents the technological approach that can achieve the lowest level of NO_x, in the range of 3 ppm and lower depending on the combustion system design. The program to develop a catalytic combustion technology that can achieve ultra low levels of NO_x, CO and unburned hydrocarbons (UHCs), applicable to a wide range of gas turbine systems and with long term durability is described. The technological approach is to combust only a portion of the fuel within the catalyst with the remaining fuel combusted downstream of the catalyst allowing the catalyst to operate at a low temperature and thus obtaining good long term catalyst durability. This catalytic combustion approach is then applied to a 1.4 MW gas turbine to demonstrate feasibility and to obtain real field experience and to identify issues and areas needing further work. The success of this demonstration lead to a commercial combustor design. This combustor and the final commercial package is described and the performance specifications discussed.     

Advanced technology catalytic combustor for high temperature ground power gas turbine applications

We report results from a lean burn ultra-low emission catalytic combustor. In a sub-scale rig, atmospheric testing with methane demonstrated NO_x<3, CO<5, and UHC<1 ppm, with stable combustion at inlet temperatures of 400–500°C (750–1020°F) and combustor discharge temperatures of 1150–1540°C (2100–2800°F). Catalyst temperatures were held well below metal substrate material limits, while combustor discharge temperatures of up to 1540°C (2800°F) were achieved.     

Development of a low NOx catalytic combustor for a gas turbine

Catalytic combustion is an advanced combustion technology and is effective as a NO_x control for a 1300°C class gas turbine for power generation, but the catalyst reliability at high temperatures is still insufficient. To overcome this difficulty, catalytic combustors combined with premixed combustion were designed. In this concept, it is possible to obtain combustion gas at a temperature of 1300°C while keeping the catalyst bed temperature below 1000°C. Catalyst segments are arranged alternately with premixing nozzles for the mixing of catalytic combustion gas and fresh premixture. An air bypass valve was fitted to this combustor for extending the range of stable combustion. As a result of the atmospheric combustion tests, NO_x emission was lower than 5 ppm, combustion efficiency was almost 100%, and high combustion efficiency was obtained in the range of 900–1300°C of the combustor exit gas temperature. A full-pressure combustion test is planned to prove the combustor performance.     

Numerical simulation of the two-dimensional flow in high pressure catalytic combustor for gas turbine

The objective of this paper is modeling the mechanism of high pressure and high temperature catalytic oxidation of natural gas, or methane. The model is two-dimensional steady-state, and includes axial and radial convection and diffusion of mass, momentum and energy, as well as homogeneous (gas phase) and heterogeneous (gas surface) single step irreversible chemical reactions within a catalyst channel. Experimental investigations were also made of natural gas, or methane combustion in the presence of Mn-substituted hexaaluminate catalysts. Axial profiles of catalyst wall temperature, and gas temperature and gas composition for a range of gas turbine combustor operating conditions have been obtained for comparison with and development of a computer model of catalytic combustion. Numerical calculation results for atmospheric pressure agree well with experimental data. The calculations have been extended for high pressure (10 atm) operating conditions of gas turbine.     

Development of a high-temperature combustion catalyst system and prototype catalytic combustor turbine test results

A new combustion catalyst system for gas turbines composed of high-temperature durable ceramic catalysts made of fine manganese-substituted hexaaluminate particles and noble metal-carrying cordierite honeycomb catalysts has been developed. A 160 kW prototype catalytic combustor turbine rigged with a 220 mm in diameter catalyst system was constructed and tested including a continuous 215-hour operation and repeated sudden stops. The results showed practical combustion performance with ultra-low NO_x emissions less than 40 ppm (converted to 0% oxygen) and the feasibility of long term catalyst durability.     

Application concepts and evaluation of small-scale catalytic combustors for natural gas

Basic application concepts of catalytic combustion are roughly classified into three types, and the development of catalysts, combustion performance and applicability are stated. On the diffusive catalytic combustion method, completeness of methane combustion and its reaction mechanism have been demonstrated by detailed combustion analysis of the burner and reaction kinetics. On the adiabatic lean premixed catalytic combustion method, applicability of a high-temperature catalyst system based on Mn-substituted hexaaluminate monolithic honeycomb to a 1.5 MW gas turbine combustor has been investigated through pressurized combustion tests and prototype engine-rig tests. As a result, a good outlook of the basic technical problems to overcome including the catalyst durability and the combustor control method was obtained, but another problem was that of the combustor capacity. In view of the progress of the non-catalytic lean premixed combustion method, it was concluded that a hybrid catalytic combustion method limiting catalytic combustion to the low-temperature range in this concept might become efficient in the future, but that it would depend on the development of efficient catalysts initiating their activity at about 350°C and having durability at 1000°C.     

Catalytic combustion system for a 10 MW class power generation gas turbine

In early 2000, GE Energy launched a program to develop a catalytic combustion system for one of its small power generation gas turbines, the GE10-1 engine. The target was to release to the market a new combustor able to guarantee NO_x emissions lower than 2.5 ppmvd (referred to 15 vol.% O₂). Today, a full-scale engine test campaign has been completed, during which measured NO_x emissions were as low as 1 ppmvd in the 90–100% load range.

The article is aimed to illustrate the developed technology and the results obtained. The combustion system's configuration is briefly described, focusing on the XONON^® catalyst module installed. Reported data show combustion system's performances, mainly in terms of pollutant emissions and operability. Perspectives for future development of such combustion system are outlined.     

Emissions and wall temperatures for lean prevaporized premixed gas turbine combustor

Experimental studies are carried out for investigating emission and wall temperature for traditional gas turbine combustor converted to lean premixed prevaporized (LPP) combustor. Vortex chamber, air preheating system, flat flame burner and inlet temperature control system are designed. Vortex chamber was maintained at the main air inlet port for controlling secondary air flow rate and wall temperature. Kerosene/air mixture temperature at exit from burner and entering combustion chamber was kept constant at 650 K for all runs. Special considerations were given for measuring NO_X, UHC, CO, local A/F ratio, flame temperature, exhaust gases temperature and wall temperature. For swirl and non swirl cases, secondary air ratio and primary zone air/fuel ratio were varied. The different operating parameters affecting flame temperature through it is affecting on local A/F ratio which is the main parameter for controlling flame temperature, emissions and walls temperatures. Flat flame burner and vortex chamber are useful tools for reducing emission and controlling walls temperatures. The inner liner wall temperatures are more affected by primary zone equivalence ratio while the outer liner wall temperatures are more affected by secondary air flow rate. Semi empirical correlations for NO_X, UHC and CO concentrations, exhaust gases temperature and maximum inner liner wall temperature are carried out. Good agreement between the measured and the calculated results are obtained. The present results are useful for further development of the traditional gas turbine combustor converted to LPP combustor.     

Engineering prediction of soot concentration in the primary zone of the gas turbine combustor

The trends towards using heavier fuel oil in the gas turbine engine will increase the soot formation rate in the primary zone, which increases flame radiation and impairs flame tube durability. Therefore, devising a method to determine quantitiatively the soot concentration is of paramount importance, as it helps in combustor design and pollution control. The method proposed adopts the Schmidt technique for radiation measurements together with soot formation and oxidation models. The soot concentration predictions from this method have been compared with those calculated from measurements of radiation in the primary zone and exhaust smoke at the combustor exit. Favourable comparison was achieved, especially under full load conditions.     

Development of a catalytic combustor with heat exchanger

Catalytic combustion is thought to be a considerable improvement on the traditional one under specific conditions. Due to its special features, catalytic combustion has two strong points compared to flame: no NO_x emission and high reaction efficiency. However, the preheating process of catalytic combustion is an obstacle that deteriorates profitability in operation. So the HTHE (High Temperature Heat Exchanger) is adapted to the system to reinforce the preheating process, and we show that the catalytic combustion is maintained steadily without exceptional heat injection. As a result, the stability on the catalytic surface is the most important operational factor. To achieve it, both mixture gas property and temperature distribution should be controlled.     

Development of a catalytic burner with Pd/NiO catalysts

A catalytic burner was studied which can be used as a heater operated at medium temperature. The catalytic combustion was initiated by an igniter which was placed on the exit surface of the catalyst layer. Noble metal catalysts (Pd/NiO) which were supported on alumina washcoated honeycomb were used, whose maximum heat-resisting temperature is about 900°C. The optimal operating conditions for stable catalytic combustion were obtained by means of analyzing the catalytic combustion region, the temperature distribution, and the combustion efficiency.     

Combustion performance test of a new fuel DME to adapt to a gas turbine for power generation

Recently, DME (dimethyl ether, CH₃OCH₃) has attracted a great deal of attention as an alternative fuel owing to its easy transportation and cleanliness. This study was conducted to verify the combustion performance and to identify potential problems when DME is fueled to a gas turbine. Combustion tests were conducted by comparing DME with methane, which is a major component of natural gas, in terms of combustion instability, NO_x and CO emissions, and the outlet temperature of the combustion chamber. The results of the performance tests show that DME combustion is very clean but hard to control. The CO emission level of DME is lower than that of methane, while the NO_x emission level of DME is as low as that of methane. When firing DME, the pressure fluctuation in the combustion chamber caused by combustion instability is lower than that occasioned when firing methane. From the results of the outlet temperature of combustor we have ascertained that DME combustion is more likely to flash back than methane combustion and this property should be considered when operating a gas turbine and retrofitting a burner.     

Combustion of waste trap grease oil in gas turbine generator

The possibility of using waste trap grease in electric power generation is explored in this study. The performance and emissions of both diesel and waste trap grease oils were tested in a gas turbine generator at comparable operating conditions. The fuel system of the gas turbine was modified for dual fuel capability with a diversion valve and a heat exchanger with exhaust for elevating the temperature of trap grease. The viscosity of trap grease was measured as a function of temperature and it was determined that the trap grease oil should be heated up to nearly 80 °C in order to approach the viscosity of diesel fuel such that satisfactory injector atomization can be achieved. The heating values of the diesel and trap grease were measured using an oxygen bomb calorimeter to facilitate the calculations of engine performance on an energy input basis. The results showed that the trap grease exhibits less NO_x emission for high generator loads compared to diesel, whereas CO and CO₂ emissions are slightly to significantly higher than those of diesel as load decreases. The results of the performance and emissions testing indicate that trap grease can be satisfactorily used for power generation.     

Catalytic combustion concept for gas turbines

Catalytic combustion for gas turbines was investigated, based on a partial catalytic combustion section followed by a homogeneous combustion zone. A pressurized test rig (<25 bar) was built to test the influence of various parameters on this concept using Pd and Pt catalysts.

The pressure influence on the apparent catalytic reaction rate was of the order 0.4, assuming that the reaction kinetics could be described by a power rate function which was of first order with respect to methane. Pd catalysts showed a pressure-dependent temperature for the transition of the active PdO to the much less active Pd. Combining Pd and Pt within one catalyst resulted in a considerably lower transition temperature.

Homogeneous combustion reactions set on from 650°C, depending on the methane concentration, pressure and flow. With inlet temperatures above 800°C the homogeneous combustion always started. At outlet temperatures below 1050°C high CO concentrations could be measured. At higher temperatures the CO, CH₄ and NO_x concentrations were lower than 5 ppm. During several experiments total conversion of CH₄ and CO was observed.     

天然气催化燃烧在燃气轮机和锅炉中的应用

综述了天然气催化燃烧技术在燃气轮机和热水锅炉中的应用和研究现状及其发展方向,介绍了几种不同形式的催化燃烧器和一些典型的设计实例,指出催化燃烧技术仍存在的问题。