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Energy Analysis of Cascade Heating with High Back-Pressure Large-Scale Steam Turbine

1
Key Laboratory of Condition Monitoring and Control for Power Plant Equipment (North China Electric Power University), Ministry of Education, Beijing 102206, China
2
School of Energy and Power Engineering, Lanzhou University of Technology, Lanzhou 730050, China
*
Author to whom correspondence should be addressed.
Energies 2018, 11(1), 119; https://doi.org/10.3390/en11010119
Received: 17 November 2017 / Revised: 27 December 2017 / Accepted: 31 December 2017 / Published: 3 January 2018
(This article belongs to the Section Electrical Power and Energy System)
To reduce the exergy loss that is caused by the high-grade extraction steam of traditional heating mode of combined heat and power (CHP) generating unit, a high back-pressure cascade heating technology for two jointly constructed large-scale steam turbine power generating units is proposed. The Unit 1 makes full use of the exhaust steam heat from high back-pressure turbine, and the Unit 2 uses the original heating mode of extracting steam condensation, which significantly reduces the flow rate of high-grade extraction steam. The typical 2 × 350 MW supercritical CHP units in northern China were selected as object. The boundary conditions for heating were determined based on the actual climatic conditions and heating demands. A model to analyze the performance of the high back-pressure cascade heating supply units for off-design operating conditions was developed. The load distributions between high back-pressure exhaust steam direct supply and extraction steam heating supply were described under various conditions, based on which, the heating efficiency of the CHP units with the high back-pressure cascade heating system was analyzed. The design heating load and maximum heating supply load were determined as well. The results indicate that the average coal consumption rate during the heating season is 205.46 g/kWh for the design heating load after the retrofit, which is about 51.99 g/kWh lower than that of the traditional heating mode. The coal consumption rate of 199.07 g/kWh can be achieved for the maximum heating load. Significant energy saving and CO2 emission reduction are obtained. View Full-Text
Keywords: combined heat and power generation; high back-pressure; district heating; cascade utilization of waste heat combined heat and power generation; high back-pressure; district heating; cascade utilization of waste heat
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Ge, Z.; Zhang, F.; Sun, S.; He, J.; Du, X. Energy Analysis of Cascade Heating with High Back-Pressure Large-Scale Steam Turbine. Energies 2018, 11, 119.

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