Hybrid coal-fired power plants with CO ₂ capture: A technical and economic evaluation based on computational simulations

Pulverized coal-fired (PC) power plants are the major technology used to generate electricity for power generation around the world. These processes are generally considered to make a significant contribution to global climate change since they have high CO ₂ emissions, with the exception of those coal-fired power plants that employ CO ₂ capture and storage (CCS) technology. With regard to coal-fired power plants, two main options for capturing CO ₂ from flue gases can be adopted, namely post-combustion and oxy-fuel combustion systems. The former technology option separates CO ₂ from the flue gas generated by the combustion of coal with air. For chemical absorption, generally a solvent such as MEA is used. However, there is a serious concern about the energy consumption required for regeneration of the solvent MEA. Oxy-fuel combustion systems, on the other hand, involve separating the oxygen from air and then burning the coal in a mixture of pure oxygen and recycled flue gas. This approach reduces the amount of flue gas substantially and simplifies the separation process due to the absence of nitrogen and argon in the stream. However there are some drawbacks in connection with some components, such as air separation units (ASU), which require high capital and operating costs and are energy intensive. A new idea was proposed by Zanganeh et al. [1]. This was a hybrid of oxy-combustion and post-combustion capture and would use air with O ₂ enrichment. Such PC power stations would use an ASU plant to obtain O ₂ enrichment and would still require the CO ₂ purification and compression processes. The ASU plant would be smaller than for oxy-fuel and the CO ₂ purification and compression systems would be smaller than for air-firing. This paper is to evaluate the proposed process technically and economically based on detailed simulation. The hybrid coal-fired power plant with CO ₂ capture system has the potential advantage of reducing energy consumption and costs. To explore the advantages and disadvantages of the hybrid process with CO ₂ capture, a comparative analysis of the supercritical PC power plant is carried out. The technical design and the mass and energy balances are implemented by using the ECLIPSE simulation package.