Gas turbine for Micro-CHP system and heat recovery with a conventional steam boiler: Thermodynamic analysis

Abstract

The main objective of this paper is to demonstrate the advantages of using the micro gas turbine (MGT) exhaust gasses to substitute the air needed in the combustion camera, conventional steam boiler. It was evaluated the performance of the Capstone C30 gas turbine. Because the exhaust gasses from de MGT comes with a high air excess they can be used to feed the air needed in a conventional steam boiler. In this work was evaluated the effect that has the use of those gasses on the heat convection transfer coefficient in order to know the advantage or disadvantage using those gasses. A thermodynamic analysis model was developed to know the behavior of a conventional steam boiler when the exhaust gasses are used as air for the combustion process. It was gotten the operation parameters of the MGT which are: pressure ratio=3.2 and the temperature turbine inlet=1050°C. Derating coefficient of this turbine was calculated and it was estimated that for each 500 meters above sea level the generated power decrease 5.5% and when the temperature increase 5°C power decrease 3.9%. Meanwhile, when the exhaust gasses of the MGT are feeded to the steam boiler it could save about of 10% of fuel. Because MGT exhaust gasses are relatively poor in oxygen the mass flow feeded to the steam boiler is increased and then the flow regime is also increased. Whit these phenomena the convection heat transfer coefficient is higher than the conventional ones. In this work was found that this coefficient increased more than 12% respect to the original system.