Performance of Gas-Steam Combined Cycle Cogeneration Units Influenced by Heating Network Terminal Steam Parameters

The determination of source-side extracted heating parameters is of great significance to the economic operation of cogeneration systems. This paper investigated the coupling performance of a cogeneration heating and power system multidimensionally based on the operating characteristics of the cogeneration units, the hydraulic and thermodynamic characteristics of the heating network, and the energy loads. Taking a steam network supported by a gas-steam combined cycle cogeneration system as the research case, the interaction effect among the source-side prime movers, the heating networks, and the terminal demand thermal parameters were investigated based on the designed values, the plant testing data, and the validated simulation. The operating map softhe gas-steam combined cycle cogeneration units were obtained using THERMOFLEX, and the minimum source-side steam parameters of the steam network were solved using an inverse solution procedure based on the hydro-thermodynamic coupling model. The cogeneration operating maps indicate that the available operating domain considerably narrows with the rise of the extraction steam pressure and flow rate. The heating network inverse solution demonstrates that the source-side steam pressure and temperature can be optimized from the originally designed 1.11 MPa and 238.8°C to 1.074 MPa and 191.15°C, respectively. Under the operating strategy with the minimum source-side heating parameters, the power peak regulation depth remarkably increases to 18.30% whereas the comprehensive thermal efficiency decreases. The operation under the minimum source-side heating steam parameters can be superior to the originally designed one in the economy at a higher price of the heating steam. At a fuel price of $0.38/kg and the power to fuel price of 0.18 kg/(kW·h), the critical price ratio of heating steam to fuel is 119.1 kg/t. The influence of the power-fuel price ratio on the economic deviation appears relatively weak. © 2024, Tech Science Press. All rights reserved.