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Optimization of heat source side technical scheme of combined heat and water system based on a coal-fired power plant


Recovering the waste heat (WH) of a power plant can conserve energy and reduce emissions. Scholars have proposed utilizing the WH of power plants in a combined heat and water (CHW) system, which is considered an economical, energy-saving, and environment-friendly way to integrate water and heat supply into long-distance transportation in urban areas of northern China. However, to date, a detailed design of the case on the heat source side of the CHW has not been developed. Therefore, in this study, the heat source side of a CHW system was divided into two cases: a single-generator set and a double-generator set, and both cases were optimized. The parameters of a multi-effect desalination (MED) process were examined; the optimal number of evaporation stages during the MED process was 12, and the optimal heat source temperature during the first stage was 70 °C. Then, by matching the extraction and exhaust steam flows, the WH of the exhaust steam in the heating season was finally utilized. Further, under each case optimal conditions, energy, exergy, and cost were analyzed. The results showed that the exergy efficiency in the heating season for each case was approximately 50%, whereas that in the non-heating season was approximately 3.5%. The economy and water quality of the single-generator case were better than those of the double-generator case. However, the absorption heat pump required in the single-generator case is difficult to realize because it operates under two working conditions.

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absorber in AHP


absorption heat pump


condenser in AHP


combined heat and water


combined heat and power


concentrated seawater


desalinated water


evaporator in AHP

E-i :

i-th effect evaporator of MED device


feed seawater


generator in AHP


heat exchanger


intermediate-pressure cylinder


low-pressure cylinder


multi-effect desalination


reverse osmosis




waste heat

YR-i :

i-th preheater of MED device


annual total cost (100 million yuan)


coefficient of performance


annual operation cost of total electricity consumed (100 million yuan)

E DW :

exergy of freshwater (kW)

E in :

sum of the exergy input to the system (kW)

E out :

sum of the exergy output from the system to the external environment (kW)

ΔE :

sum of all exergy losses of the system (kW)


gained output ratio

G z :

total annual freshwater output (10000 t)


enthalpy of fluid entering or leaving the i-th effect of MED (kJ/kg)


initial investment


annual operation cost of RO membrane replacement (100 million yuan)


annual operating cost of pretreatment drugs (100 million yuan)


flow of fluid entering or leaving the i-th effect of MED (t/h)

Q z :

the total heat supply in the heating season (10000 GJ)


annual reduced generation (kWh)

S z :

total heat transfer area of the system (10000 m2)

s :

heat transfer area/unit DW (m2/t)


annual electricity consumption of the water pumps and other equipment (kWh)


mass concentration of fluid entering or leaving the i-th effect of MED (%)

σ :

exergy efficiency (%)


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This work was supported by the 13th Five-Year National Key Technology R&D Program of China (No. 2019YFE0193200) and the Natural Science Foundation of China (No. 51521005).

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Correspondence to Jianjun Xia.

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Yang, X., Liu, Z., Chen, J. et al. Optimization of heat source side technical scheme of combined heat and water system based on a coal-fired power plant. Build. Simul. 15, 1455–1473 (2022).

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  • waste heat of power plant
  • combined heat and water
  • seawater desalination
  • optimal case
  • thermal economic analysis