Combined cycle plant

J. N. Chapman and N. R. Johanson, "Design Considerations for a Class of 600 MWe MHD Steam Combined Cycle Plants," 28th Intersociety Energy Conversion Engineering Conference, Adanta, Ga., Aug. 1993. 

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... 

In a combined cycle plant, high steam pressures do not necessarily convert to a high thermal efficiency for a combined cycle power plant. Expanding the steam at higher steam pressure causes an increase in the moisture content at the exit of the steam turbine. The increase in moisture content creates major erosion and corrosion problems in the later stages of the turbine. A limit is set at about 10% (90% steam quality) moisture content. 

Fig. 7.2. Combined cycle plant with heat loss between bigber and lower plants.

The integrated coal gasification combined cycle plant (IGCC)... 

Fig. 8.1 shows a diagram of a chemical absorption process described by Chiesa and Consonni [1], for removal of CO2 from the exhaust of a natural gas-fired combined cycle plant (in op>en or semi-closed versions). The process is favoured by low temp>erature which increases the CO2 solubility, and ensures that the gas is free of contaminants which would impair the solvent properties. 

Includes combined cycle plant (CCP) and combined heat and power plant (CHP or cogeneration plant). 

Rating combustion gases from combined cycle plants to use in vegetable crops in greenhouses, in applications in irrigation pipes to prevent clogging and to balance the pH in nutrient solutions. 

Hydrogen as well as syngas may also be used to power a combined cycle plant. The plant output can be adjusted to generate more power or more hydrogen as needed. 

The combustion gases that leave the gas turbine still have a great deal of heat that can be utilized [2,3]. The combined cycle plant does not discard the... 

Power generation plants such as the steam plant, the gas turbine plant, and combined cycle plants require the combustion of a fossil fuel. Now, combustion is a chemical reaction of fuel with an oxidant (usually oxygen), and it makes sense to examine the combustion process more closely and analyze its thermodynamic efficiency. This means that we will examine the furnace/combustor of Figures 9.8, 9.10, and 9.12. We will examine coal and gas combustion at the level needed for thermodynamic analysis, after discussing some commonly used coal combustion processes. 

The combined cycle and the combined cycle cogeneration plant showed that waste heat could be put to good use, thus generating less lost work. The process conditions used in the analysis of the combined cycle plant were chosen for illustrative purposes and were arbitrary. In practice, the conditions are generally chosen to increase power output (see, e.g., Chapter 5). 

Existing capture technologies, however, are not cost-effective when considered in the context of sequestering C02 from power plants. Most power plants and other large point sources use air-fired combustors, a process that exhausts C02 diluted with nitrogen and excess air. Flue gas from coal-fired power plants contains 10%-12% C02 by volume, while flue gas from natural gas combined cycle plants contains only 3%-6% C02. For effective carbon sequestration, the C02 in these exhaust gases must be separated and concentrated. 

In China and other less industrialized nations, industrial energy efficiency could be substantially improved. Chinese buildings require twice the energy as do buildings in similar climates in Europe or the United States. The efficiency of their power plants is 40% below the efficiency of combined-cycle plants in the United States. Their steel industry requires 20%, their cement 45%, and ethylene producers require 60% more energy than the international average. For these reasons, state-of-the-art optimization and energy conservation techniques (the topic of Chapter 2) alone can make a big difference. 

In a combined-cycle power plant, electricity is produced by two turbines, a gas and a steam turbine. The term combined cycle comes from the fact that the combustion gas turbine operates according to the Brayton cycle and the steam system operates according to the Rankine cycle. As shown in Figure 2.115, the dual-shaft combined-cycle plant consists of a gas turbine (GT)... 

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