Assessment of Hot Gas Cleanup Technologies in Coal-Fired Gas Turbines

This paper reviews the status of in situ gas stream cleanup technologies which are an integral part of the direct coal-fired gas turbine systems being developed through the U.S. Department of Energy (DOE), Morgantown Energy Technology Center (METC). The technical discussion focuses on the proof-of-concept systems under development in the DOE/METC Advanced Coal-Fueled Gas Turbine Systems (ACFGTS) program initiated in 1986. In this program, Solar Turbines Inc., the Allison Gas Turbine Division of General Motors Corporation, and Westinghouse Electric Corporation have completed bench-scale tests of integrated combustion and hot gas cleanup systems in preparation for full-size subsystem tests. All these projects include the development of cleanup systems for contaminants resulting from the combustion of coal. These systems will both control emissions of pollutants and protect the turbine gas path from fouling, erosion, and corrosion. The bench-scale tests have demonstrated efficient combustion of coal-water slurries (CWS) and dry coal in high-pressure, short residence-time combustors. The tests have also yielded promising results in the abatement of nitrogen oxides (NOx) and volatile alkali and in the removal of ash and sulfur species from the hot gas streams.

Active Control Application to a Model Gas Turbine Combustor

Closed-loop feedback control, developed in a axisymmetric can combustor, is demonstrated in a model can combustor with discrete wall jets. The study represents the initial steps toward the application of feedback control technology to practical gas turbine combustion systems. For the present application, the radiative flux from soot particulate is used as an indication of combustor performance, and nozzle atomizing air is selected as the input parameter. A measurement of radiative flux at the exit plane of the combustor is conveyed to a control computer which invokes an optimization algorithm to determine changes in the dome region necessary to minimize the radiative flux from soot. The results demonstrate the utility and potential of active control for maintaining optimal performance in real-time.

Potential Applications of Structural Ceramic Composites in Gas Turbines

A Babcock and Wilcox - Solar Turbines Team has completed a program to assess the potential for structural ceramic composites in turbines for direct coal-fired or coal gasification environments. A review is made of the existing processes in direct coal firing, pressurized fluid bed combustors, and coal gasification combined cycle systems. Material requirements in these areas were also discussed. The program examined the state-of-the-art in ceramic composite materials. Utilization of ceramic composites in the turbine rotor blades and nozzle vanes would provide the most benefit. A research program designed to introduce ceramic composite components to these turbines was recommended.

Evaluation of a Catalytic Combustor in a Gas Turbine-Generator Unit

As a final step of the Catalytic Combustor Development Program, a catalytic combustor developed was tested in a 150-kW gas turbine-generator unit. A digital control system was developed to improve its controllability for a transient operation, and a 200-hr continuous operation test was performed to asses the durability of the catalyst. During the test, an excellent performance of the control system was verified, and a very high combustion efficiency of more than 99% and a ultra-low NOx level of less than 5.6 ppm (at 15% O2) were achieved at a 150-kW generator output. In addition, the combustion efficiency has been maintained at over 98% for 200 hours of operation. However, the catalyst exposed to 200 hours of operation showed signs of deactivation.

A Study of Isothermal Flow Past a Confined Bluff Body

The paper describes a preliminary assessment of a TEACH-based mathematical model, known as TURCOM, for isothermal flow past a confined bluff-body. The assessment is based on comparisons of numerical predictions with the experimental data. Laser Doppler Velocimetry (LDV) and gas analysis were used to measure radial profiles of axial velocity and CO2 concentration. Laser sheet illumination was employed to study the gross features of the flow. Depending on the jet velocity ratio, two or three recirculation zones and two well-defined stagnation points along the centerline were predicted. Agreement between the predictions and experimental data were reasonably good, but the axial location of the fuel stagnation point was under-estimated when compared with the LDV data. Flow visualization indicated vortex shedding off the edges of the bluff body, an unsteady flow phenomenon that neither TURCOM prediction nor LDV measurements could identify.

Gas Turbine Power Plant Possibilities With a Nuclear Heat Source: Closed and Open Cycles

With the capability of burning a variety of fossil fuels, giving high thermal efficiency, and operating with low emissions, the gas turbine is becoming a major prime-mover for a wide spectrum of applications. Almost three decades ago two experimental projects were undertaken in which gas turbines were actually operated with heat from nuclear reactors. In retrospect, these systems were ahead of their time in terms of technology readiness, and prospects of the practical coupling of a gas turbine with a nuclear heat source towards the realization of a high efficiency, pollutant free, dry-cooled power plant has remained a long-term goal, which has been periodically studied in the last twenty years. Technology advancements in both high temperature gas-cooled reactors, and gas turbines now make the concept of a nuclear gas turbine plant realizable. Two possible plant concepts are highlighted in this paper, (1) a direct cycle system involving the integration of a closed-cycle helium gas turbine with a modular high temperature gas cooled reactor (MHTGR), and (2) the utilization of a conventional and proven combined cycle gas turbine, again with the MHTGR, but now involving the use of secondary (helium) and tertiary (air) loops. The open cycle system is more equipment intensive and places demanding requirements on the very high temperature heat exchangers, but has the merit of being able to utilize a conventional combined cycle turbo-generator set. In this paper both power plant concepts are put into perspective in terms of categorizing the most suitable applications, highlighting their major features and characteristics, and identifying the technology requirements. The author would like to dedicate this paper to the late Professor Karl Bammert who actively supported deployment of the closed-cycle gas turbine for several decades with a variety of heat sources including fossil, solar, and nuclear systems.

Experimental Evaluation of a Low Emissions, Variable Geometry, Small Gas Turbine Combustor

The results of an on-engine evaluation of an ultra-low NOx, natural gas-fired combustor for a 200 kW gas turbine are presented. The combustor evaluated used lean-premixed combustion to reduce NOx emissions and variable geometry to extend the range over which low emissions were obtained. Test results showed that ultra-low NOx emissions could be achieved from full load down to approximately 50% load through the combination of lean-premixed combustion and variable primary zone airflow.

MS3002 Advanced Tech Upgrade Application and Operating Experience

Modernization of MS3002 gas turbines produced by GE from 1951 to 1973 has been accomplished with the application of advanced technology components in a redesigned turbine hot section. Texas Eastern installed the first modernization package in 1986 and now have 10 units in service totalling more than 135,000 operating hours. This paper presents the user’s motivation to refurbish 30 year old gas turbines, including details of the uprate installation and subsequent operating experience. Specifics of the advanced technology components in these units are provided including their impact on unit performance and reliability.

Natural Gas Compressor Station Noise Abatement Systems

In recent years urban residential growth has created a serious encroachment problem to all industrial complexes including natural gas compressor stations. Union Gas Ltd. has recently been involved in the design of an acoustically treated compressor station. Noise emanating from a station into the environment outside the property perimeter is caused by mechanical equipment in operation and gas flowing through piping and valves. Noise generated from a turbine station varies in power level and frequency. The noises, varying from the high frequency startling type to the low frequency throbbing type, create a number of problems for surrounding residential homes. This paper describes the Parkway Compressor Station located near Toronto, Ontario, Canada at which various items of mechanical equipment were identified and acoustically treated with satisfactory results.

Coal Mineral Matter Transformation During Combustion and its Implications for Gas Turbine Blade Erosion

The transformation of mineral matter during combustion and the characteristics of the ash formed are important from the standpoint of coal fired gas turbine operation. Using a novel FT-IR technique and EDX analysis, these mineral matter transformations are investigated when the coal is burnt in a one-dimensional pulverized coal-dust-air flame. The role of clays, pyrite, quartz, potassium and other compounds in the ash are discussed with particular reference to deposit buildup and erosion of gas turbine blades.