Abstract
An improved heating system integrated with waste pressure utilization (WPU) for combined heat and power (CHP) cogeneration was proposed. The new heating system efficiently utilized the excess pressure of the extraction heating steam to drive the WPU turbine and generator for producing electricity, achieving higher energy efficiency and lower fuel consumption of the CHP unit. The results of the detailed thermodynamic analysis showed that applying the proposed concept in a typical 300 MW coal-fired CHP unit could reduce the standard coal consumption rate by 9.84 g/(kW·h), with a thermal efficiency improvement of 1.97% (absolute value). Compared to that of the original heating process, the energy efficiency of the proposed process decreased by 0.55% (absolute value), but its exergy efficiency increased dramatically by 17.97% (absolute value), which meant that the proposed configuration could make better use of the steam energy and contribute to the better performance of the CHP unit. As the unit generation load and supply and return-water temperatures declined and the unit heating load rose, the WPU system would generate more electricity and its energy-saving benefit would be enhanced. This work provides a promising approach to further advance the CHP technology and district heating systems.
Highlights
Combined heat and power (CHP) as a cogeneration system can produce power and heat at the same time, which has the advantages of energy cascade utilization, significant flexibility, and high efficiency [1,2,3,4]
The overall efficiency of combined heat and power (CHP) is from 60% to 80%, which is much higher than the 40% average efficiency of typical coal-burning power plants [13,14]
The results implied that the power generation thermal generation thermal efficiency of the unit had risen from 48.62% to 50.59%, because of the waste pressure utilization (WPU)
Summary
Combined heat and power (CHP) as a cogeneration system can produce power and heat at the same time, which has the advantages of energy cascade utilization, significant flexibility, and high efficiency [1,2,3,4]. In China, the capacity of installed CHP units has reached 300 million kilowatt since 2016, accounting for about 30% of the total thermal power capacity [12]. The overall efficiency of CHP is from 60% to 80%, which is much higher than the 40% average efficiency of typical coal-burning power plants [13,14]. There is still huge energy-saving potential in CHP units, such as the waste, heat, and pressure of the heating systems, which can possibly be utilized by process optimization. It is essential to recover the waste energy of CHP and promote its energy efficiency
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