Steam gas turbines

Therefore, merely reducing coal use will not he sufficient to satisfy the Protocol. Any plan to comply with the Protocol needs to assume substitution, first by non-combustion energy sources—that is by renewables or nuclear energy—and second by natural gas. This would have to be accompanied by achievement of far greater efficiencies in energy production (for example by introduction of far more fuel-efficient steam gas turbines, driven by natural gas) and by more efficient use of energy. 

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... 

Increase compressor speed. Electrical motors are seldom oversized. So, capacity and/or head increase (< 10%) may require a new, bigger motor. Compared with electric motors, steam/gas turbines have more design margin and may not require replacement Compressor cleaning... 

Install critical pumps/compressors in pairs (with one in operation and another on standby). Install electric motor for the first pump/compressor, and consider an alternative driver such as steam/gas turbines and diesel engines... 

For a combined heat and power (CH P) system for a one-family house, an optimum configuration with respect to cost effectiveness was determined by Schmid and Wiinning [16]. The fuel cell system was shown to provide about 70% of the average annual heat demand of the house, while peaks in demand were buffered by a conventional burner with an efficiency of 95%. The relative energy savings P of the fuel processor/fuel cell system over a centralised power supply with conventional steam gas turbines (SGT) was calculated as follows ... 

Figure10.4 Primary energy savings ofacombined heat and power (CHP) system fora one-famiiy house compared with conventional power production (T)ei = 40%) and the steam gas turbine process (riel = 55%) upper lines correspond to an overall efficiency of the CHP system of 90%, lower lines to 80% [16].

A more complex utility is combined heat and power (or cogeneration). Here, the heat rejected hy a heat engine such as a steam turbine, gas turbine, or diesel engine is used as the hot utility. 

Now let us take a closer look at the two most commonly used heat engines (steam and gas turbines) to see whether they achieve this efficiency in practice. To make a quantitative assessment of any combined heat and power scheme, the grand composite curve should be used and the heat engine exhaust treated like any other utility. 

Different utility options such as furnaces, gas turbines, and different steam levels can be assessed more easily and with greater confidence knowing the capital cost implications for the heat exchanger network. 

The principal sources of utility waste are associated with hot utilities (including cogeneration) and cold utilities. Furnaces, steam boilers, gas turbines, and diesel engines all produce waste as gaseous c bustion products. These combustion products contain carbon... 

Reducing products of combustion from furnaces, steam boilers, and gas turbines by making the process more energy efficient through improved heat recovery. 

The hot gases from the combustor, temperature controlled to 980°C by excess air, are expanded through the gas turbine, driving the air compressor and generating electricity. Sensible heat in the gas turbine exhaust is recovered in a waste heat boiler by generating steam for additional electrical power production. 

After burning, the sensible heat in the products of combustion can then be converted into steam that can be used for external work or can be converted directly into energy to drive a shaft, eg, in a gas turbine. In fact, the combustion process actually represents a means of achieving the complete oxidation of... 

In apphcation to electric utihty power generation, MHD is combined with steam (qv) power generation, as shown in Figure 2. The MHD generator is used as a topping unit to the steam bottoming plant. From a thermodynamic point of view, the system is a combined cycle. The MHD generator operates in a Brayton cycle, similar to a gas turbine the steam plant operates in a conventional Rankine cycle (11). 

Eig. 8. Cost of electricity (COE) comparison where represents capital charges, Hoperation and maintenance charges, and D fuel charges for the reference cycles. A, steam, light water reactor (LWR), uranium B, steam, conventional furnace, scmbber coal C, gas turbine combined cycle, semiclean hquid D, gas turbine, semiclean Hquid, and advanced cycles E, steam atmospheric fluidized bed, coal E, gas turbine (water-cooled) combined low heating value (LHV) gas G, open cycle MHD coal H, steam, pressurized fluidized bed, coal I, closed cycle helium gas turbine, atmospheric fluidized bed (AEB), coal J, metal vapor topping cycle, pressurized fluidized bed (PEB), coal K, gas turbine (water-cooled) combined, semiclean Hquid L, gas turbine... 

New units can be ordered having dry, low NO burners that can reduce NO emissions below 25 ppm on gaseous fuels in many cases, without back-end flue-gas cleanup or front-end controls, such as steam or water injection which can reduce efficiency. Similar in concept to low NO burners used in boilers, dry low NO gas turbine burners aim to reduce peak combustion temperatures through staged combustion and/or improved fuel—air mixing. 

Limitations in the material of constmction make it difficult to use the high temperature potential of fuel hiUy. This restriction has led to the insertion of gas turbines into power generation steam cycles and even to the use of gas turbines in preheating air for ethylene-cracking furnaces. 

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. 

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