544 / 2019-01-16 20:25:54

Novel Heating Design Using Multiple Stages of Low-Pressure Extraction Steam in Coal-Fired Combined Heat and Power Unit

combined heat and power; heating system; extraction steam; heat regenerative system; thermodynamic analysis

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Combined heat and power (CHP) can provide multiple products (power and heat) efficiently and environmentally friendly, which is an attractive approach for energy conversion and utilization. As a result of this application, the efficiency of energy production can be increased. And under the right conditions, a CHP system can reduce the harmful emissions resulting from power production, causing less greenhouse gases to be released than a reference system where power and heat are produced separately. In a regular CHP unit, the district heat is provided by the extraction steam obtained from the intermediate-pressure turbine, resulting in serious exergy destruction and low exergy efficiency of the heating process subsequently.
In this study, an innovative heating design for coal-fired CHP units was proposed, which employs the multiple stages of low-pressure extraction steam drawn from the low-pressure turbine to heat the supply water of the primary heat network. A detailed thermodynamic analysis of the reformative configuration was conducted, which can examine the performance of the new concept and reveal its energy-saving mechanism. The results showed that the proposed scheme could contribute to a power output enhancement of 5.4 MW. Resulting from the suggested modification, the total system efficiency of the CHP unit is raised from 43.24% to 43.70%, while the effective electric efficiency is promoted from 41.33% to 41.81%.