Exergy Analysis of a Biomass Co-Firing Based Pulverized Coal Power Generation System

Abstract

Results are reported of an exergy analysis of a biomass co-firing-based power generation system. A simulation is performed for a typical pulverized coal-fired steam cycle system by considering four biomass fuels (chicken litter, refuse derived fuel, rice husk, and sawdust) and two coals (bituminous coal and lignite) to investigate the effect of biomass co-firing on the system performance. Inlet and outlet exergy flows, exergy losses, and exergy efficiencies of the boiler and the plant are determined for various fuel combinations and the two cases considered at different co-firing conditions. The results show that the exergy efficiencies of both the boiler and the overall plant decrease with increasing biomass content in the fuel blend. The greatest decrease in exergy efficiency occurs for sawdust blends, while exergy efficiency decreases the least for chicken litter blends at all co-firing ratios and for both cases considered. For case 1 (fixed fuel flow rate), the plant exergy efficiency decreases from 33.82% to 32.94% and 33.39%, respectively, for the blends of bituminous coal/sawdust and bituminous coal/chicken litter, and from 32.22% to 31.54% and 32.03%, respectively, for the blends of lignite/sawdust and lignite/chicken litter when co-firing ratio increases from 0% to 30%. For case 2 (fixed heat input to steam cycle), the plant exergy efficiency declines to 32.50%, 33.05%, 31.45%, and 31.97%, respectively, for the blends of bituminous coal/sawdust, bituminous coal/chicken litter, lignite/sawdust, and lignite/chicken litter when coal flow decreases to 0.7 kg/sec.

Exergy Analysis of Solid Fuel-Fired Heat and Power Plants: A Review

“…Co-firing also gives higher exergy efficiency than the biomass-based plant. However, co-firing of biomass in the existing coal-fired plant decreases the boiler and overall exergy efficiency due to increased moisture content in the biomass, which reduces the furnace exit gas temperature [83]. Moreover, it increases corrosion and ash deposition in the system, and if co-utilization of biomass fuel in coal-fired plant is not carefully designed, it will involve risk of power outages [80].…”

“…However, the exergy losses due to irreversibility from biomass co-firing are larger than for coal-based power plants. This irrervisibility has led to decreases in the exergy efficiencies of both the boiler and the overall co-combustion plant [83]: the gas exiting the furnace has a lower temperature due to a reduction in the exergy input to the plant. Applying biomass co-firing to a fluidized bed shows that the velocity of the fluidized bed does not influence the exergy efficiency [84].…”

Optimization models to integrate production and transportation planning for biomass co-firing in coal-fired power plants

“…Works by Li Paudel (2013) study the economic feasibility of co-firing. Ruhul-Kabir and Kumar (2012) conduct a life cycle energy and environmental performance analysis of co-firing different types of biomass since the efficiency of co-firing process depends on the specific chemical content and properties of the biomass used in co-combustion (Mehmood et al 2014). O'Mahoney et al (2013) and Wils et al (2012) use a cost-benefit analysis to show that governmental incentives are necessary for making co-firing an attractive investment option.…”

“…Based upon our review of the literature, we contend that most current research has involved elucidating the technological aspects of co-firing processes (Li et al 2012, Tumuluru et al 2012 and the techno-economic and feasibility analysis (Dong et al 2010, Ruhul-Kabir and Kumar 2012, Steer et al 2013, Goerndt et al 2013b, Paudel 2013, Mehmood et al 2014). Very little research has been undertaken to estimate the transportation costs of delivering biomass to power plants (Roni et al 2014).…”

Sustainable Coal Supply Chain Management Using Exergy Analysis and Genetic Algorithm

“…With such an increasingly competitive coal industry, it is highly required to develop efficient methods to minimize the overall cost for the sustainable coal supply chain management (mining, transportation, and power plant), while meeting required environmental standards and regulations [8]. Considering environmental risks and impacts of the coal mining, the performance of the whole process is one of the major concerns for the involved parties [9]. In addition to the economic costs of coal supply chain (e.g., miners, washing plants, transporters, and power plants), there are other costs related to environmental impacts and pollutions which should be taken into account within the total operational costs of the system [8].…”