Numerical Study of Gas Mixing Effect on Block 3 and Block 4 Muara Tawar’s Gas Turbine Combustion Stability

Abstract

AbstractThe power plants managed by PT PJB UP Muara Tawar are peak load power plants with a regular start–stop operation. Blocks 3 and 4 operate gas turbines with Siemens V94.2’s type. Gas turbine fuel comes from three suppliers, namely Nusantara Regas (NR), Pertamina EP (PEP), and PGN with their specific compositions. Combustion stability is the key of operation, so it must be maintained from any disturbances. This aims of the study is to determine the stability of combustion with the parameters; lift off and blow off also analyzed the effect of excess air. This study uses a numerical simulation model with computational fluid dynamics (CFD) with non-premixed combustion model that carried out at 137 MW. The analysis shows that higher composition of fuel gas indicated by methane will decrease the lift off around 0.185 m, and the flame length became longer. The effect of excess air in combustion will lead to the increase in lift by adding more excess air around 0.21 m, and flame length became shorter. Excess air will increase maximum temperature but decreased gradually toward outlet. NOx emission mostly produced by high temperature as higher gas composition will tend to higher NOx production, and the addition of excess air will decrease NOx production as a result of lower temperature. The optimum energy based on outlet temperature is medium gas composition with 15% excess air and also will provide optimal combustion stability, efficiency, and NOx emission values.KeywordsNatural gasExcess airFlame stabilityLift offTemperatureNOx