Combined cycle power plants steam turbine

Figure A1.3 Photo of combined cycle power plant steam turbine with open cover (courtesy and copyright of MHI). Single-cylinder reheat turbines are used.

As of the mid-1990s, many older conventional steam plants have been converted to combined cycle. The old boiler is removed and replaced by a combustion turbine and heat recovery steam generator. Although the cycle efficiency is not as high as completely new plants, substantial capital cost is avoided by the modification and reuse of existing steam turbine and auxiHary equipment. In many combined cycle power plants, steam is injected into the combustors of the combustion turbine to lower peak flame temperatures and consequendy lower NO. ... 

The Fossil Power Plants of the 1990s and into the early part of the new millennium will be the Combined Cycle Power Plants, with the gas turbine as being the centerpiece of the plant. It is estimated that between 1997-2006 there will be an addition of 147.7 GW of power. These plants have replaced the large Steam Turbine Plants, which were the main fossil power plants through the 1980s. The Combined Cycle Power Plant is not new in concept, since some have been in operation since the midl950s. These plants came into their own with the new high capacity and efficiency gas turbines. 

The new marketplace of energy conversion will have many new and novel concepts in combined cycle power plants. Figure 1-1 shows the heat rates of these plants, present and future, and Figure 1-2 shows the efficiencies of the same plants. The plants referenced are the Simple Cycle Gas Turbine (SCGT) with firing temperatures of 2400 °F (1315 °C), Recuperative Gas Turbine (RGT), the Steam Turbine Plant (ST), the Combined Cycle Power Plant (CCPP), and the Advanced Combined Cycle Power Plants (ACCP) such as combined cycle power plants using Advanced Gas Turbine Cycles, and finally the ITybrid Power Plants (HPP). 

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. 

Simple Cycle Gas Regenerative Gas Steam Turbine Combined Cycle Power Advanced Gas Turbine Hybrid Power Plant... 

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. 

The code provides for the testing of gas turbines supplied with gaseous or liquid fuels (or solid fuels converted to liquid or gas prior to entrance to the gas turbine). Test of gas turbines with water or steam injection for emission control and/or power augmentation are included. The tests can be applied to gas turbines in combined-cycle power plants or with other heat recovery systems. 

Steam is passed through a number of tubes embedded in the nozzle or blades of the turbine. In many cases, the steam is bled from after the HP Steam Turbine of a combined cycle power plant and returned after cooling the gas turbine blades, where the steam gets heated in the process to the IP steam turbine. This is a very effective cooling scheme and keeps the blade metal temperature below 1250 °F (649 °C). 

Boyce, M.P., Performance Characteristics of a Steam Turbine in a Combined Cycle Power Plant, Proceedings of the 6th EPRI Steam Turbine Generator/ Workshop, August 1999. 

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)... 

Combined-Cycle Power Plant - A power plant that uses two thermodynamic cycles to achieve higher overall system efficiency e.g. the heat from a gas-fired combustion turbine is used to generate steam for heating or to operate a steam turbine to generate additional electricity. 

The electric power industry uses three types of fossil fuel power plants coal-fired steam, gas turbine, and combined cycle power plants. The most common and widely used is the pulverized coal-fired steam power plant. Fuel oil can be used in place of... 

Electricity Price 0.0977 /kWh Ecoinvent 3, electricity production, natural gas, combined cycle power plant. Comment for electricity produced in steam turbine... 

Figure 13.8 Layout of the integrated gasification combined cycle power plant with CO2 capture through hydrogen membranes with two different permeate pressures high pressure for feeding the gas turbine and ambient pressure for the postfiring of the heat recovery steam generator.

Similarly to turbocharged internal combustion engines and to large-scale steam turbines within combined cycle power plants, MCFCs also can be integrated with turbines. 

Kehlhofer, Rolf, et al. Combined-Cycle Gas and Steam Turbine Power Plants. 3d ed. Tulsa, Okla. Penn Well, 2009. Application of gas turbine as part of cutting-edge powergeneration technology. Presents concepts, components, applications, operations of these plants. Each chapter has illustrative figures. Peng, William W. Fundamentals of Turbomachinery. Hoboken, N.J. John Wiley Sons, 2008. Chapter 8 discusses gas turbines and covers thermodynamics, design, efficiency, and performance, as well as applications illustrated. 

In a combined cycle power plant (CCPP), or combined cycle gas turbine (CCGT) plant, a gas turbine generator produces electricity and the waste heat is used to make steam for generating additional electricity via a steam turbine this last step enhances the efficiency for electricity generation to about 60%, because the temperature difference between the input and output heat levels is higher leading to an increase in the Carnot efficiency. Most modem power plants in Europe and in North America are of this type. 

A Comparison of Steam-Injected Gas Turbine and Combined-Cycle Power Plants Technology Assessment. Palo Alto, California Electric Power Research Institute, June 30, 1989. GS-6415s. 

Combined-cycle power plant (combination of Brayton gas-turbine cycle [fuel = natural gas or liquefied natural gas combustion product parameters at the gas-turbine inlet Tin 1650°C] and Rankine steam turbine cycle [steam parameters at the turbine inlet = 620°C (r = 374°C ]). Up to 62... 

---