This study deals with the optimization of the pulverized coal fired power plant based on the design parameters and the overall performance of the generated power from the plant. The model developed was based on the concepts of coal combustion, energy balances, enthalpy changes, entropy changes, heat transfer and mass transfer of the steam power cycle. It was found from the study that the overall performance of the power plant depends mainly on the main steam, reheated steam, steam pressures from the turbines, turbine efficiency, boiler efficiency, air from the preheater, excess air %, moisture in the coal. The net efficiency obtained using the developed model is 42.11%.
1.1 Power generation from coal
The most efficient way of generating electricity is from Coal. Coal has been one of the most abundant fossil fuel used for generating the electricity worldwide (IEA, 2010). A typical diagram of the utilization of coal as the primary resource in U.S has been given in the figure 1.1. The demand for the coal has been increasing day by day when compared to the other fossil fuels like Oil and Natural gas. According to International energy agency (IEA), by the year 2030 the coal consumption rate will be more than 6000 million tons of carbon equivalent and across the globe 42% of electricity supply mainly comes from the coal power plants. Apparently about 28% of carbon dioxide is emitted in the process of generating 42% of electricity (IEA, 2010). There is a rapid change in the atmosphere with the release of CO2 from the power plants leading to Global warming. As reported by Canada’s electricity generation by fuel type (CEA, 2010), coal emits approximately 1 tonne of CO2 by burning and generating 1 megawatt of electricity.
In the present world, there are many technologies from which electricity can be generated from the Coal. The technologies are Fluidized bed power plant (FB), Integrated Gasification Combined Cycle power plant (IGCC) and Pulverized coal power plant (PC). Fluidized bed combustion has two types Circulating Fluidized power plant (CFB) and Pressurized Fluidized bed power plants (PFB). The CFB is basically operated by the coal combustion in the presence of limestone where the electricity is mainly produced by the steam cycle. Limestone reduces the amount of SO2 being emitted from the process.
Figure 1.1 Fuel share in U.S Electric power industry in the year 2009 (Source: U.S Energy Information Administration, form E1A-923)
The residues from the combustion of coal are small particles of limestone, unburnt coal and ash. These entire residues are recirculated to the boiler again by using cyclones. PFB is almost same as the CFB just that the combustor in the pressurized fluidized bed power plants operates at a high pressure from 1 MPa to 1.5 MPa. PFB has the ability to burn even the low-grade fuel (Podolski, 1983). The IGCC process involves the production of syngas from the coal combustion. The syngas drives the gas turbines and the heat liberated from the gas turbines passes into the steam cycle to generate the electricity. Pulverized coal (PC) power plant is of great concern due to the relative attribution to carbon dioxide per MW (megawatt) of power production (Weijin et al). Powdered coal is used as the fuel for the Pulverized coal process to produce the thermal energy. This thermal energy is used to drive the turbine to produce the electricity.
Considering some of the energy losses inside the power plant like Frictional losses, loss due to the flue gas, loss due to the unburnt gas heating value, loss due to the unburnt fuel heating value, Condenser heat loss. All these energy losses accounts for the reduced efficiency of any power plant. Increasing the steam parameters,