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Synergistic Effects of Hydrothermally Treating Coal-Biomass Blend

Saba, Akbar
http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1556223157880773

Abstract Details

2019, Master of Science (MS), Ohio University, Mechanical Engineering (Engineering and Technology).
Inorganic content in coal is high and co-firing coal with biomass at power plants to mitigate hazardous pollutants has been implemented at the expense of energy content and density partitioning. 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 and can serve as a viable upgrade to standard co-firing fuel. The main goal of this work was to evaluate the synergistic effects of miscanthus on coal during Co-HTC through two objectives: (1) Evaluate the solid biofuel properties of the Co-HTC hydrochar and characterize the inorganic content of the process liquid (2) Examine the process economics of scaled-up Co-HTC hydrochar production. Fuel quality was assessed for all hydrochars by evaluating mass yields, energy content, ultimate analysis, and proximate analysis. Calculation of combustion parameters showed experimental ignition and burnout indices of Co-HTC 260 °C hydrochar were 29.0% and 26.5 % lower than theoretical, non-interacting indices, respectively. Hydrochars shared the benefits of low sulfur and low ash content of miscanthus but maintaining higher energy content of coal. Hydrochars produced at 260 °C had energy contents as high as coal (27.3 ± 0.6 MJ kg-1) and 73% less ash content and 74% less sulfur than raw coal as a result of the more acidic environment produced by miscanthus decomposition. Furthermore, hydrochars were homogeneous as miscanthus-derived hydrochar was formed on coal surface according to SEM imaging and verified by the reduced pore width from nitrogen adsorption. A 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 and design 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 tonne for a 110 MWe. Sensitivity analysis indicates that this breakeven selling price could be as low as $106 per tonne for a higher capacity plant. In addition to plant size, the price of solid fuel is sensitive to the feedstock costs and hydrochar yield. Future directions of this research can incorporate gas and process liquid component identification and kinetics for better understanding of how intermediates and products evolve during treatment. Consideration for different feedstocks to co-treat, such as lower ranked coals and/or foodwaste, can help in cost reduction by reducing purchasing costs, however, additional batch studies would need to be required to evaluate the degree of synergistic effects.
Toufiq Reza (Advisor)
103 p.
Chemical Engineering; Energy; Mechanical Engineering
Hydrothermal treatment; biomass; coal; thermochemical conversion; hydrothermal carbonization; HTC; Co-HTC

Recommended Citations

Citations

  • Saba, A. (2019). Synergistic Effects of Hydrothermally Treating Coal-Biomass Blend [Master's thesis, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1556223157880773

    APA Style (7th edition)

  • Saba, Akbar. Synergistic Effects of Hydrothermally Treating Coal-Biomass Blend. 2019. Ohio University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1556223157880773.

    MLA Style (8th edition)

  • Saba, Akbar. "Synergistic Effects of Hydrothermally Treating Coal-Biomass Blend." Master's thesis, Ohio University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1556223157880773

    Chicago Manual of Style (17th edition)

ohiou1556223157880773
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This open access ETD is published by Ohio University and OhioLINK.