Abstract
Biomass energy and especially biofuels produced by biomass gasification are clean and renewable options for power plants. Also, on hot days the performance of gas turbines decreases substantially, a problem that can be mitigated by fog cooling. In the present paper, a biomass-integrated fogging steam injected gas turbine cycle is analyzed with energy and exergy methods. It is observed that (1) increasing the compressor pressure ratio raises the air flow rate in the plant but reduces the biomass flow rate; (2) increasing the gas turbine inlet temperature decreases the air and biomass flow rates; (3) increasing the compressor pressure ratio raises the energy and exergy efficiencies, especially at lower pressure ratios; (4) increasing the gas turbine inlet temperature raises both efficiencies; and (5) overspray increases the energy efficiency and net cycle power slightly. The gas turbine exhibits the highest exergy efficiency of the cycle components and the combustor the lowest. A comparison of the cycle with similar cycles fired by natural gas and differently configured cycles fueled by biomass shows that the cycle with natural gas firing has an energy efficiency 18 percentage points above the biomass fired cycle, and that steam injection increases the energy efficiency about five percentage points relative to the cycle without steam injection. Also, the influence of steam injection on energy efficiency is more significant than fog cooling.
Highlights
The performance of a gas turbine, output power and energy efficiency, is significantly affected by ambient temperature
The mass and energy balance equations for the all components are summarized by Table 2, but we describe the exergy equations below due to their significance
The variations with compressor pressure ratio of the biomass and air mass flow rates are shown in Figure 2a for the biomass integrated fogging steam injected gas turbine (BIFSTIG) plant
Summary
The performance of a gas turbine, output power and energy efficiency, is significantly affected by ambient temperature. A percentage of the water (often ~2%) remains in a liquid phase (i.e., as overspray) and enters the compressor for evaporation there This method includes a series of high pressure reciprocating pumps providing demineralized water to an array of fogging nozzles located after the air filter elements. The most advantageous among the available systems is difficult to determine and usually depends on ambient conditions (e.g., ambient air temperature and relative humidity) and design parameters (e.g., air flow rate to gas turbine, power output ratio and number of hours per day in which additional power is needed). The use of fogging along with steam injection in a gas turbine reduces the inlet air temperature [8]. The results are expected to have practical application, since the considered cycle is used for supplying the energy in villages and small towns, especially in tropical locations
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