Operational optimization on large‐scale combined heat and power units with low‐pressure cylinder near‐zero output

• Published in: Energy science & engineering Vol. 11; no. 6; pp. 2081 - 2095
• Main Authors: Wang, Zijie, Gu, Yujiong, Zhao, Ziliang, Lu, Shuyin
• Format: Journal Article
• Language: English
• Published: London John Wiley & Sons, Inc 01.06.2023; Wiley
• Subjects: Carbon dioxide; carbon dioxide emissions; Coal; Cogeneration; combined heat and power; Consumption; Cylinders; economic operational range; Energy efficiency; Exergy; Flexibility; Heat; Heat exchange; Low pressure; low‐pressure cylinder near‐zero output (LP‐ZO); Mathematical models; operational optimization; Optimization; Particle swarm optimization; Power plants; Renewable energy; Software; Thermodynamics; China
• ISSN: 2050-0505; 2050-0505
• DOI: 10.1002/ese3.1439

Many power plants have been transformed and operated using low‐pressure cylinder near‐zero output (LP‐ZO) technology in China to make way for or provide necessary guarantees for renewable energy power generation. This research focuses on utilizing numerical simulation tools to improve the operational economy of units with LP‐ZO. The LP‐ZO thermodynamic and energy‐consumption model of a reference plant is established, and the momentum particle swarm optimization method is used to optimize the unit operations. Moreover, a model to determine the economic operational range of the combined heat and power plant with LP‐ZO is proposed. The results show that the LP‐ZO mode operations of the unit can reduce the minimum peak shaving rate and improve the flexibility of operations. The energy efficiency of the LP‐ZO mode is increased due to the recovery of a significant portion of the cold source losses. However, the irreversible exergy loss caused by large temperature difference heat exchange reduces the exergy efficiency of the unit. After operational optimization, the reference plant can save approximately 68.15 t d−1 of coal and reduce carbon dioxide emissions by about 27 t tce−1 d−1. This study provides an operating approach to the CHP plant with LP‐ZO unit in enhancing flexibility and economy. To analytically improve the operational economy of units with low‐pressure cylinder near‐zero output, the energy consumption model is developed to obtain the energy consumption distribution of a reference power plant. Based on the energy consumption of the units, the momentum particle swarm optimization method is used to optimize the unit operations. The coal consumption and carbon dioxide emissions of the reference plant can be reduced by approximately 68.15 and 27 tons a day, respectively.