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.     

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.     

提高热效,降低污染的催化燃烧法

传统的火焰燃烧法热利用率不高，且伴随着产生相当数量的ＮＯＸ。催化助燃烧技术利用催化剂点燃和保持气相反应，确保燃料完全燃烧，提高热效率；又因稳定地调节火焰温度，减少ＮＯＸ的排放量，减少了空气污染，具有相当实用价值。研究活性组分和优质载体是实现催化燃烧的关键因素。     

Catalytic combustion over platinum group catalysts: fuel-lean versus fuel-rich operation

Performance data are presented for methane oxidation on alumina-supported Pd, Pt, and Rh catalysts under both fuel-rich and fuel-lean conditions. Catalyst activity was measured in a micro-scale isothermal reactor at temperatures between 300 and 800 °C. Non-isothermal (near adiabatic) temperature and reaction data were obtained in a full-length (non-differential) sub-scale reactor operating at high pressure (0.9 MPa) and constant inlet temperature, simulating actual reactor operation in catalytic combustion applications.

Under fuel-lean conditions, Pd catalyst was the most active, although deactivation occurred above 650 °C, with reactivation upon cooling. Rh catalyst also deactivated above 750 °C, but did not reactivate. Pt catalyst was active above 600 °C. Fuel-lean reaction products were CO₂ and H₂O for all three catalysts.

The same catalysts tested under fuel-rich conditions demonstrated much higher activity. In addition, a ‘lightoff’ temperature was found (between 450 and 600 °C), where a stepwise increase in reaction rate was observed. Following ‘lightoff’ partial oxidation products (CO, H₂) appeared in the mixture, and their concentration increased with increasing temperature. All three catalysts exhibited this behavior.

High-pressure (0.9 MPa) sub-scale reactor and combustor data are shown, demonstrating the benefits of fuel-rich operation over the catalyst for ultra-low emissions combustion.     

Catalytic combustion technology to achieve ultra low NOx, emissions: Catalyst design and performance characteristics

A catalytic combustion system has been developed which feeds full fuel and air to the catalyst but avoids exposure of the catalyst to the high temperatures responsible for deactivation and thermal shock fracture of the supporting substrate. The combustion process is initiated by the catalyst and is completed by homogeneous combustion in the post catalyst region where the highest temperatures are obtained. Catalysts have been demonstrated that operate at inlet temperatures as low as 320°C at 11 atm total pressure and conditions typical of high performance industrial gas turbines. The ignition temperature is shown to correlate with the specific catalytic activity of the washcoat layer over a rather broad range of activities. A reaction model has been developed that can predict ignition behavior from the measured catalytic activity.     

Catalytic combustion: from reaction mechanism to commercial applications

The present commercial applications of catalytic combustion are briefly reviewed. Difficulties still hinder the commercial development of this type of combustion as an NO_x control technique. The problems are addressed by both academia and industry. The relevant activities of Gaz de France and GASTEC, both involved in several projects supported by the European Union, are described.     

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.     

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.     

A reactor network model for predicting NOx emissions in gas turbines

The numerical prediction of NOx emissions from gas turbines is addressed in this paper. Generated from Computational Fluid Dynamics (CFD), a Reactor Network (RN) is defined to model the NOx formation with a detailed chemistry. An optimized procedure is proposed to split the reactive flow field into homogeneous zones considered as Perfectly Stirred Reactors (PSR). Once connected together, they result in a Chemical Reactor Network (CRN) that yields a detailed composition regarding species and temperature in the combustion chamber. Sensitivity studies are then performed to estimate the influence of air humidity and gas turbine load on NOx predictions. The NOx emissions predicted are in good agreement with the measured data in terms of levels and trends for the case studied (a gas turbine flame tube fed with natural gas and functioning at a pressure of 15 bar). Finally, the RN methodology has shown to be efficient estimating accurately NOx emissions with a short response time (few minutes) and small CPU requirements.     

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.     

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.     

降低NOX污染的净化处理法

燃烧等带来的ＮＯＸ是酸雨的主要来源。高温催化燃烧可抑制ＮＯＸ的生成；选择催化 法（ＳＣＲ）为消除ＮＯＸ的成熟技术，是处理煤电厂烟道气的必要措施；烟道气循环法和低ＮＯＸ燃烧器法简单实用；在氧气存在下烃类化合物对ＮＯＸ还原法较符合工业尾气的实际条件，因而是个活跃的研究领域。     

Modeling and simulation of a smart catalytic converter combining NOx storage, ammonia production and SCR

Dynamic simulation of the smart catalytic converter, proposed by Daimler AG, is presented. The smart catalytic converter combines NOx storage, on-board ammonia production and selective catalytic reduction (SCR) and functions in a dual-mode operation, alternating between lean burn and rich burn. It relies on intrinsic dynamic operation and synchronization of all units and its development demands a reliable dynamic simulator. A platform capable of simulating the dynamic behavior of multiple-unit aftertreatment system was developed based on COMSOL package. Predictive kinetic models were developed for NOx storage unit that includes ammonia formation function and for NH₃-SCR unit. Using these kinetic models, two-unit smart catalytic converter was simulated on the developed simulator. The results of the simulator were validated using two-unit experimental data. The simulator was also employed to control and optimize the performance of smart catalytic converter. It was shown that the simulator is vital for optimization of lean and rich periods in order to ensure stable lean–rich cycles.     

Bubble Column Reactors and Fischer-Tropsch Synthesis

Three-phase slurry bubble column reactors have been used extensively in a number of chemical, petrochemical, and biochemical process engineering applications. For the success of these operations and their large scale industrial exploitation, it is essential that their transport and chemical characteristics be adequately understood on a mechanistic basis so that appropriate design criteria and optimum operating conditions can be established. It is the purpose of this review to present such available knowledge in relation to chemical catalytic operations. The mass transfer characteristics, catalytic activity, and mixing patterns of different phases necessitate a detailed understanding of the hydrodynamic behavior and catalyst dispersion in slurry bubble column reactors. The current status of these aspects is presented, discussed, and assessed in this review. Chemical and biochemical reactions are exothermic in nature and hence efficient heat removal devices must be installed in the reactor to preserve its isothermal behavior and chemical catalytic activity by avoiding temperature runaway. Extensive work recently conducted from this heat transfer viewpoint is reviewed and appraised. The bubble dynamics, and slurry mixing and movement characteristics of such baffled bubble columns are significantly different from those of unbaffled bubble columns. Very limited information is available on baffled bubble column operations and this is reviewed and critically examined. An important application of the slurry bubble column is in the synthesis of fuel gases on suspended catalyst particle surface to produce chemicals. One such example is the Fischer-Tropsch synthesis of hydrogen and carbon monoxide in what is referred to as indirect coal liquefaction technology. Pilot plant efforts of this nature and their successes are briefly mentioned. Mathematical details and models developed from time to time to characterize catalytic bubble column operations are briefly described and discussed. In the context of available information and its integration presented here, the specific needs for future experimental and theoretical research work are pointed out.