The Steam Power Plant

The steam power plant is a large-scale heat engine in wliich the woridng fluid (H2O) is in steady-state flow successively tlirough a pump, a boiler, a turbine, and a condenser in a cyclic process (Sec. 5.2). The working fluid is separated from the heat source, and heat is transferred across a phy sical boundary. In a fossil-fuel-firedplant the combustiongases are separatedfrom the steam by boiler-tube walls. 

The internal-combustion engine is another fomi of heat engine, wherein high temperatures are attained by conversion of the chemical energy of a fuel directly into internal energy within the work-producing device. Examples are Otto and Diesel engines and the gas turbine.  

This chapter is devoted to the analysis of several coimnon heat-engine cycles. 

Clearly, i) increases as Th increases and as Tc decreases. Although the efficiencies of practical heat engines are lowered by irreversibilities, it is still true that tlieir efficiencies are increased when the average temperature at wliich heat is absorbed is increased and when the average temperature at which heat is rejected is decreased. 

The processes tlrat occur as tire working fluid flows around the cycle of Fig. 8.1 are represented by lines on tire TS diagram of Fig. 8.2. The sequence of lines shown coirfomrs to a Carnot cycle. Step 1 - 2 is tire vaporization process taking place in the boiler, wherein saturated liquid water absorbs heat at tire constant temperahire Th, and produces saturated vapor. Step 2 3 is a reversible, adiabatic expansion of saturated vapor into the two-phase 

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Natural gas is the fuel of choice wherever it is available because of its clean burning and its competitive pricing as seen in Figure 1-30. Prices for Uranium, the fuel of nuclear power stations, and coal, the fuel of the steam power plants, have been stable over the years and have been the lowest. Environmental, safety concerns, high initial cost, and the long time from planning to production has hurt the nuclear and steam power industries. Whenever oil or natural gas is the fuel of choice, gas turbines and combined cycle plants are the power plant of choice as they convert the fuel into electricity very... 

The steam power plant should become another site for an exciting project enabling a 2-fold reduction in the degree of flue gas cleaning while cutting the electric power consumption by a factor of 2 to 3. The new process that applies pulsed voltage to the precipitation filters has been successfully introduced at several other plants in Ukraine. 

The second application of availability analysis is used to evaluate the nature and magnitude of thermodynamic irreversibilities in a methane reformer plant coupled to a high-temperature nuclear reactor. It is shown that a combination of thermal histograms and availability concepts are helpful not only in evaluating the net impact of irreversibilities in various chemical process steps on the steam power plant, but, more importantly, 1n suggesting process modifications that could improve the overall efficiency by avoiding unnecessary entropy production. 

The total plant of this process can be divided into three plants The nuclear heat production plant. Figure 2, the brown coal hydrogasification plant. Figure 3, and the steam power plant, Figure 2. 

Figure 2. Simplified flow diagram of the nuclear heat production plant and the steam power plant. For the hydrogasification plant see Figure 3.

More commonly, utility plants (e.g., the steam power plant and cooling-water system) are considered separately from the rest of the process. This is shown schematically in Figure 9.4, where the process is divided into three systems. The benzene-mixed xylenes plant is sufficiently complex that it is advisable to divide it into a reaction section and a separation section, as shown in Figure 9.5. Any individual operation in the process - for example, fractionator C-2 - can be the system and everything else the surroundings. Finally, a portion of a single operation can be the system - for example, one tray in fractionator C-2. 

The first two actions are for nuclear shutdown purposes, while isolation of the steam generator (i.e. closure of the feedwater and live-steam valves) separates the reactor plant from the steam power plant. 

Except for coal-fired power plants, the steam power plant process is also used for the direct or indirect power generation from other fuels. In principle, this process forms the thermodynamic basis for power generation from nuclear fuels or biomass... 

Say we wish to convert a fossil-fuel, nuclear, or solar energy source into net electrical power. To accompftsh this task, we can use a Rankine cycle. The Rankine cycle is an idealized vapor power system that contains the major components foimd in more detailed, practical steam power plants. While hydroelectric and wind are possible alternative sources, the steam power plant is presently the dominant producer of electrical power. 

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