Abstract
Co-Hydrothermal Carbonization (Co-HTC) is a thermochemical process, where coal and biomass were treated simultaneously in subcritical water, resulting in bulk-homogenous hydrochar that is carbon-rich and a hydrophobic solid fuel with combustion characteristics like coal. In this study, technoeconomic analysis of Co-HTC was performed for a scaled-up Co-HTC plant that produces fuel for 110 MWe coal-fired power plant using Clarion coal #4a and miscanthus as starting feedstocks. With precise mass and energy balance of the Co-HTC process, sizing of individual equipment was conducted based on various systems equations. Cost of electricity was calculated from estimated capital, manufacturing, and operating and maintenance costs. The breakeven selling price of Co-HTC hydrochar was $117 per ton for a 110 MWe. Sensitivity analysis indicates that this breakeven selling price could be as low as $106 per ton for a higher capacity plant. Besides plant size, the price of solid fuel is sensitive to the feedstock costs and hydrochar yield.
Highlights
Coal dependence has led to significant air pollution as the combustion of coal releases various air pollutants that are hazardous and toxic to the surrounding life and environment
In 2016, U.S coal combustion accounted for 26.3% of the CO2 produced from fossil fuel combustion and contributed to nearly 69% (CO2 equivalent basis) of the greenhouse gases produced from the electrical power generation sector [1]
It should be noted that the determination of the lower sensitivity bound (LSB) and higher sensitivity bound (HSB) are based on previously observed market fluctuations or when not available, a general overall change in the parameter was assumed (e.g., fixed capital investment (FCI))
Summary
Coal dependence has led to significant air pollution as the combustion of coal releases various air pollutants (trace metals, chlorine, greenhouse gases etc.) that are hazardous and toxic to the surrounding life and environment. Saba et al, observed hydrochar homogeneity and additional biomass degradation (via mass yield) catalyzed by Co-HTC with coal, resulting in lower pH media [23]; low pH would encourage more leaching of inorganic content and sulfur As expected, both studies found increased HHV of produced hydrochars than that of the blended and untreated feedstocks. For 1-ton rice husk conversion, HTC cost per MJ was $0.013 MJ−1 ($153 MWh−1 ), having 81% and 38% savings compared to fossil fuel oil costs and direct combustion of rice husks (when not incorporating capital costs into the HTC costs), respectively This cost is still 4.5 times more than the cost of Central Appalachian Coal at. Heat integration will be taken into consideration to reduce energy costs and to improve overall plant design
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