Turbines power from

The gas turbine power plant which has revolutioni2ed aviation derives basically from the steam turbine adapted to a different working fluid. The difference is cmcial with respect to fuel because steam can be generated by any heat source, whereas the gas turbine requires a fuel that efficiently produces a very hot gas stream and is also compatible with the turbine itself. The hot gas stream results from converting chemical energy in fuel directly and continuously by combustion in compressed air. It is expanded in a turbine to produce useful work in the form of jet thmst or shaft power. 

The gasifier for the 250 MW IGCC project in The Netherlands, scheduled to begin operation in 1993, is a 55 MW gas turbine with the balance of the power from a steam turbine. An AustraHan coal is to be used, and sulfur removal is expected to be 98.5% (95). 

Coal is fed as a paste containing 25 wt % water, and sorbent is fed diy by a lock-hopper system with pneumatic conveying. The top size of each feedstock is 3 mm in). The latent heat lost evaporating the water fed with the paste is compensated by increased gas turbine power output resulting from the increased flue-gas mass flow rate. For the 80-MWe unit, there are six coal feed points (one per 4.5 m" [48 ft"]) and four sorbent feed points (one per 6.7 m" [72 ft"]), all entering beneath the tube bank along one wall. The bed depth is... 

In the area of performance, the steam turbine power plants have an efficiency of about 35%, as compared to combined cycle power plants, which have an efficiency of about 55%. Newer Gas Turbine technology will make combined cycle efficiencies range between 60-65%. As a rule of thumb a 1% increase in efficiency could mean that 3.3% more capital can be invested. However one must be careful that the increase in efficiency does not lead to a decrease in availability. From 1996-2000 we have seen a growth in efficiency of about 10% and a loss in availability of about 10%. This trend must be turned around since many analysis show that a 1% drop in the availability needs about 2-3% increase in efficiency to offset that loss. 

The cooling of the inter-stage compressor air by injecting water is also another very effective way for getting more power from the gas turbine. The problem in most units is that there is no convenient place to inject the water. The gas turbines would require substantial modification to install such a system. Care would have to be taken that any modification would not affect the integrity of the system. This type of a system is very effective in units where there is a low and high-pressure compressor, providing a very convenient place to inject the water. This type of compressor are mostly available in aeroderivative units. 

Vaporized fuel oil gas behaves very elosely to natural gas beeause it provides high performanee with a minimum reduetion of eomponent life. About 40% of the turbine power installed operates on liquid fuels. Liquid fuels ean vary from light volatile naphtha through kerosene to the heavy viseous residuals. The elasses of liquid fuels and their requirements are shown in Table 12-1. 

Accumulators can be used to help stabilize the lube system against pressure transients such as that from the turbine power operator during a large correction. For a sizing rule of thumb, the system pressure should not vary by more than 10%, while the turbine servo travels full stroke in a one second interval. The role of accumulators for pump switching was covered earlier in the section on Startup Control. 

The accident resulted from a routine safety test of some electrical control equipment at the start of a normal reactor shutdown for routine maintenance. The test was to determine the ability to continue to draw electrical power from a turbine generator during the first minute of coast-down following a station blackout. In a blackout, the reactor automatically scrams and diesel generators start to assume load (about 1 minute required). 

Fig. 1.2 shows a gas turbine power plant operating on a closed circuit. The dotted chain control surface (F) surrounds a cyclic gas turbine power plant (or cyclic heat engine) through which air or gas circulates, and the combustion chamber is located within the second open control surface (Z). Heat (2b is transferred from Z to Y, and heat (2a is rejected from Y. The two control volumes form a complete power plant. 

The heat supply to the cyclic gas turbine power plant of Fig. 1.2 comes from the control surface Z. Within this second control surface, a steady-flow heating device is supplied with reactants (fuel and air) and it discharges the products of combustion. We may define a second efficiency for the heating device (or boiler) efficiency. 

The first equation may be applied to a control volume CV surrounding a gas turbine power plant, receiving reactants at state Rg = Ro and discharging products at state Py = P4. As for the combustion process, we may subtract the steady flow availability function for the equilibrium product state (Gpo) from each side of Eq. (2.47) to give... 

Lozza, G. and Chie.sa, P. (2001), Natural gas decarboni.sation to reduce COi emi.ssion from combined cycle—Part II steam-methane reforming, ASME J. Engng Gas Turbines Power 124(1), 89-95. 

In general, a gas turbine CHP plant may not exaetly mateh the eleetrieity and heat demands. A plant with a recuperator may meet the heat load (Qu)cg = but not the power load (Wgg < Wd= 1) so extra power from the grid is required (Wc) as illustrated in Fig. 9.4. Following a procedure similar to that given in Section 9.2.3 it may be shown [ 1 ] that the performance parameters for the total plant are then... 

The electrical and heat analysis, as discussed in Section 15.3, will show the relationship between power and heat and how this varies over time. It may be necessary to use steam bypass and stations or dump condenser, as discussed in Section 15.2. The uses of dump condensers for meeting part-load requirement is inefficient and should be avoided. It is more acceptable to reduce turbine power output accordingly and import or top-up from an alternative supply. 

Power recovery trains recover energy from the flue gas. The FCC starts to resemble a large jet engine air is compressed into a combustion zone and expanded across a turbine. Power recovery increases the efficiency of the unit but adds one more mechanical device to an already long list. Since they are too big to bypass, power trains need to be as reliable as the rest of the unit. 

The isentropic power from a steam turbine can be related to the maximum shaft power through the overall turbine efficiency ... 

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