Byproducts recovered and processing performed to produce useful chemicals from coal. fuel metering legs provided the smallest error. Water Electrolysis, In: Jürgen Garche, Editor-in-Chief, Encyclopedia of Electrochemical Power Sources, (Amsterdam, Elsevier), Pages 394-413. Testing on the flow Woodward flow rig allowed a high degree of confidence to be achieved in the system as it gave the opportunity to test the valves under conditions representative of engine operation. Can-annular combustors can be of the straight-through or reverse-flow design. Fuel to both the primary and secondary nozzles. The center nozzle allowed to extend its turndown well beyond the older design. The design is such that the pressure ratio across the fuel system is minimized as much as possible. Emission levels for operation on liquid fuel are below 42 ppmv, at full load, with a modest water-to-fuel ratio of 0.8. Air distribution in a typical diffusion combustor. General emission performance of a lean premix burner. Steam from syngas processing is not shown. Schematic diagram of a circulating fluidized-bed boiler. This is achieved by controlling the flow in each combustor can till the spectrums obtained from each combustor can match. The main fuel, approximately 97% of the total, is injected into the air stream immediately downstream of the swirler at the inlet to the premixing chamber. This in some cases has been problematic leading to flash-back-type problems. Figure 21.13. The LP fuel injector is much larger because it contains the fuel/air premixing chamber and the quantity of air being mixed is large, approximately 50–60% of the combustion air flow. A simplified pressure-volume (P-V) and temperature-entropy (T-S). The amount of cooling air required becomes an important consideration in low-Btu gas applications, since most of the air is used up in the primary zone and little is left for film cooling. 2.23. The trend now is to an evolution towards the can-annular burners. They are also required to shift to the safe state in less than 100 milliseconds. If necessary, lean–lean mode can be operated throughout the entire load range of the turbine. Boyce, in Combined Cycle Systems for Near-Zero Emission Power Generation, 2012. The MHI DLN combustion system does not require fuel staging for maintaining the fuel-to-air ratio, as is the case of the previous combustor design systems outlined in this chapter. A cross section of a DLN fuel nozzle. The secondary and tertiary are each ignited by their respective upstream stage. The uniformity of the combustor outlet profile affects the useful level of turbine inlet temperature, since the average gas temperature is limited bythe peak gas temperature. Fuel is directed to the primary, secondary, and tertiary fuel nozzles. The most commonly used type of combustor is the fully annular combustor, the others being tubular and tuboannular combustor. Figure 21.12. Burner staging is achieved, as shown in Figure 10-53, by splitting the premix gas fuel system into two groups: A rich main burner group, which is operated in a fuel-rich and stable mode. 2.15. h2 = enthalpy leaving the compressor section, h3 = enthalpy entering the turbine section. A quaternary fuel manifold is located on the circumference of the combustion casing to bring the remaining fuel flow to casing injection pegs located radially around the casing. 10, 1826-1837. The annular designs are used on European frame type gas turbines. Each GE DLN combustor system has a single burning zone formed by the combustor liner and the face of the cap. Combustion completeness affects fuel consumption directly, since the heating value of any unburned fuel is not used to increase the turbine inlet temperature. The following are the major design challenges associated with very lean combustors: First, care must be taken to ensure that the flame is stable at the design operating point. This mode is necessary to extinguish the flame in the primary zone, before fuel is reintroduced into what becomes the primary premixing zone. The prompt mechanism predominates at low temperatures under fuel-rich conditions, whereas the thermal mechanism becomes important at temperatures above 2732°F (1500°C). This mode of operation is achieved at and near the combustion reference temperature design point. There are two types of combustion in combustors: dry low NOx (DLN) or dry low emission (DLE) combustion. The air bypass valve is also used to prevent flame-out, combustion oscillations, and flash-backs that can be induced by changes in the GT total airflow resulting from IGV position changes. A lean-staged burner group, which can be operated below the flame stability limit and is used to control the gas turbine load at part load. The micro gas turbine is d esigned to function using biogas as fuel. Reasons for auto-ignition could be classified as follows: Long fuel auto-ignition delay time assumed, Variations in fuel composition reducing auto-ignition delay time, Fuel residence time incorrectly calculated. The minimum load for premixed operation is set by the combustion reference temperature and IGV position. As a result, industrial combustors tend to be much larger than aero-derived gas turbine combustors. Del. The PM1 manifold fuels the center nozzle, the PM2 manifold fuels the two outer nozzles located at the cross-fire tubes, and the PM3 manifold fuels the remaining three outer nozzles. Source: Santoleri, Joseph J. The six-fuel nozzle design is the advanced DLN-2 combustor by GE, which was designed to lower NOx output to as low as nine ppm. In the thermal mechanism, NO is formed by the oxidation of molecular nitrogen through the following reactions: As can be seen from the above equations, NOx is primarily formed through high-temperature reaction between nitrogen (N) and oxygen (O2) from the air. Another method is to deliberately dump air overboard prior to or directly from the combustion section of the engine. At this temperature, the volume of nitric oxide in the combustion gas is about 0.01%. Correlation between adiabatic flame temperature and NOx emission. [4–3]. The aerodynamics downstream of the swirl-based flame stabilizers depend on the ratio of D/d (this is A1/A30.5) for swirlers in cylindrical combustors, and on (A1/A3)0.5 if it is a swirler in an annular combustor. The percentage of primary fuel flow is modulated throughout the range of operation as a function of combustion reference temperature. Materials and the Environment (Second Edition), (Boston, Butterworth-Heinemann). Cross-section of a tubular combustor. It extends up to the upper compression ring of the piston. 2.16. If the combustor does not feature variable geometry, then it is necessary to turn on the fuel in stages as the engine power is increased. Figure 21.16. The mixing of the fuel and the air to produce a uniform fuel/ air ratio at the exit of the mixing tube is often achieved by the interaction of flows. Thermal mass flow meters were not used because the high time constant of the device would not allow adequate dynamic control of the fuel system.