Dynamic Simulations of the Humidification Tower for An Advanced Humid Air Turbine System

Abstract

The gas turbine system known as AHAT (Advanced Humid Air Turbine) has been drawing attention. AHAT employs a humidification tower to increase the air mass flow at the compressor outlet. A dynamic simulator of an AHAT plant was developed to determine the control method of the system. This paper outlines the dynamic simulator which is based on simultaneous differential equations considering heat and mass equilibrium of humid air, feed water and turbine exhaust gas. Physical values calculated using the simulator were compared to operational values obtained from trial operations of the 4MW-class AHAT pilot plant. The calculation errors of the humidification tower model, a main component of this simulator, were 0.60% for air outlet mass flow and 0.73% for air outlet absolute humidity. The developed simulator was then applied to determine the feed water control method for the humidification tower startup operation. Increasing absolute humidity affected fluctuations of the automatically controlled fuel flow rate. These fluctuations were influenced by water feeding rate, and were estimated to decrease from 59% to 58% when starting humidification in 4 minutes and to decrease from 59 % to 52% in 2 minutes.