Masters Theses

Date of Award

8-2017

Degree Type

Thesis

Degree Name

Master of Science

Major

Chemical Engineering

Major Professor

Abhijeet Borole

Committee Members

Robert M. Counce, Sankar V. Raghavan, Paul D. Frymier

Abstract

Biomass conversion to hydrocarbon fuels requires significant amounts of hydrogen. Fossil resources typically supply hydrogen via steam reforming. A new technology called microbial electrolysis cells (MECs) has emerged which can generate hydrogen from organic sources and biomass. The thermochemical route to fuels via pyrolysis generates bio-oil aqueous phase (BOAP) which can be used to make hydrogen. A process engineering and economic analysis of this technology was conducted for application in biorefineries of the future. Steam methane reforming, bio-oil separation and microbial electrolysis unit operations were simulated in Aspen Plus to derive the mass and energy balance for conversion of biomass. A process scheme using MEC to generate hydrogen, while minimizing use of natural gas was developed. A process design developed by Pacific Northwest National Laboratory was used as baseline biorefinery flowsheet. The results show that hydrogen production at a rate of 1,723 lb/hr can be derived using 19.5 % of the bio-oil as the substrate BOAP, while eliminating the need for natural gas. A two-step quench system allows separation of an aqueous stream containing about 23,000 lb/hr of organic substrate, sufficient for hydrogen generation, besides that generated from off-gas, so as to meet the total biorefinery hydrogen needs. The techno-economic analysis (TEA) showed that hydrogen can be generated for a minimum hydrogen selling price of $ 3.35/kg-H₂. The results of this study show that hydrogen can be practically derived from an aqueous soluble bio-oil stream, while majority of the bio-oil is used for hydrocarbon production, using a wholly biomass-sourced hydrogen. This alternative has potential to reduce greenhouse gas emissions from the biorefinery.

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