Title

Non-Catalytic Co-Gasification of Sub-Bituminous Coal and Biomass

Author

Guevara Che Nyendu

Date of Award:

5-2015

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biological and Irrigation Engineering

Advisor/Chair:

Foster A. Agblevor

Abstract

Fluidization characteristics and co-gasification of pulverized sub-bituminous coal, hybrid poplar wood, corn stover, switchgrass, and their mixtures were investigated. Co-gasification studies were performed over temperature range from 700°C to 900°C in different media (N₂, CO₂, steam) using a bubbling fluidized bed reactor.

In fluidization experiments, pressure drop (ΔP) observed for coal-biomass mixtures was higher than those of single coal and biomass bed materials in the complete fluidization regime. There was no systematic trend observed for minimum fluidization velocity (U_mf) with increasing biomass content. However, porosity at minimum fluidization (ε_mf) increased with increasing biomass content. Channeling effects were observed in biomass bed materials and coal bed with 40 wt.% and 50 wt.% biomass content at low gas flowrates. The effect of coal pressure overshoot reduced with increasing biomass content.

Co-gasification of coal and corn stover mixtures showed minor interactions. Synergetic effects were observed with 10 wt.% corn stover. Coal mixed with corn stover formed agglomerates during co-gasification experiments and the effect was severe with increase in corn stover content and at 900°C. Syngas (H₂ + CO) concentrations obtained using CO₂ as cogasification medium were higher (~78 vol.% at 700°C, ~87 vol.% at 800°C, ~93 vol.% at 900°C) than those obtained with N₂ medium (~60 vol.% at 700°C, ~65 vol.% at 800°C, ~75 vol.% at 900°C).

Experiments involving co-gasification of coal with poplar showed no synergetic effects. Experimental yields were identical to predicted yield. However, synergetic effects were observed on H₂ production when steam was used as the co-gasification medium. Additionally, the presence of steam increased H₂/CO ratio up to 2.5 with 10 wt.% hybrid poplar content. Overall, char and tar yields decreased with increasing temperature and increasing biomass content, which led to increase in product gas.

Recommended Citation

Nyendu, Guevara Che, "Non-Catalytic Co-Gasification of Sub-Bituminous Coal and Biomass" (2015). All Graduate Theses and Dissertations. 4233.
https://digitalcommons.usu.edu/etd/4233