Abstract

Efficient utilization of ventilation air methane (VAM) as well as improving the energy efficiency of de-carbonization oxy-coal combustion power plants are intensively studied for achieving energy savings and greenhouse gas (GHG) emission control. Here, an improved VAM-coal hybrid power generation system, which integrates a VAM-based hot air power cycle with a de-carbonization oxy-coal combustion circulating fluid bed (CFB) power plant was proposed. In the proposed system, part of the boiler flue gas was bypassed to feed the VAM auto-oxidation, and the whole VAM oxidation heat was efficiently utilized to drive a hot air power cycle. Meanwhile, the turbine exhaust air was utilized to heat the feed/condensed water within the regenerative heating trains in a cascade way, which was in turn beneficial to de-carbonization oxy-coal combustion plant. The mass and energy balance of the proposed system were determined using the simulation process. The thermodynamic benefits, economic viability and the environmental impacts were discussed. Results showed that energy efficiency of the proposed system reached 27.1% with the energy saving ratio at 0.9%. The cost of electricity (COE) was $118.15/MWh with the specific CO2 emission as low as 17.46 kg CO2/MWh.

Highlights

  • Global warming has observably affected the natural environment and human activities, making it urgent to decouple greenhouse gas (GHG) emissions from energy-related economic growth

  • A typical 600 MW electric power plant with the live/reheat steam of 16.67/3.41 MPa and 538.0/538.0 ◦ C is selected here, which comprises of a high-pressure turbine (HPT), an intermediate-pressure turbine (IPT), and a low-pressure turbine (LPT)

  • Thermodynamic performance of the proposed system is compared with the reference systems in Table 8, with the following observations: (1) 58.90 kg/s of boiler flue gas is bypassed to catalytic flow reversal reactor (CFRR)

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Summary

Introduction

Global warming has observably affected the natural environment and human activities, making it urgent to decouple greenhouse gas (GHG) emissions from energy-related economic growth. Considering the temperature of the VAM oxidation and the boiler flue gas at the cyclones (800–900 ◦ C) [16], it seems that the boiler flue gas has the potential to serve as a suitable heat source for sustaining the VAM oxidation, and simultaneously, the cold-end energy released from the VAM utilization process can be efficiently utilized in the host oxy-coal combustion power plant. Against this backdrop, in this work an innovative VAM-based hot air power cycle integrated with a de-carbonization oxy-coal combustion power plant was proposed, to efficiently utilize the VAM caloric value for power generation and increase the overall power generating efficiency by cascade utilization of the cold-end energies from both the CFB boiler and hot air power cycle. Ratio on the energy/temperature distributions and system performance were discussed

System Proposal
De-Carbonization Oxy-Coal Combustion CFB Boiler with Bypass Flue Arrangement
VAM-Based Hot Air Power Cycle
Steam Cycle and Cold-End Energies Recovery
Reference Systems Description
System Simulation
Criteria for Thermodynamic Evaluation
Criteria for Economic Evaluation
GHG Mitigation Effects
Thermodynamic Performance
Economic Viability and Environmental Impact
Sensitivity Analysis
VAM Compression Ratio
Conclusions
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