Date of Award

Spring 5-10-2019

Level of Access

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Peter Van Walsum

Second Committee Member

M. Clayton Wheeler

Third Committee Member

Adriaan Van Heiningen

Abstract

Levulinic acid (LA) is a platform chemical and it can be upgraded to various products like bio-oil. The acid hydrolysis of cellulose is a widely researched pathway to make LA. However, investments to produce LA commercially can be subjected to risks due to feedstock price volatility and high processing costs. Such risks can be reduced by expanding the feedstock portfolio to produce LA from feedstock beyond wood and improving the energy efficiency of the process. One little investigated feedstock for production of LA is macro algae (seaweed). Seaweed is potentially attractive because it has low content of lignin or 5 carbon carbohydrates, which complicate production of LA. In this study, we investigated the production of LA from sugar kelp (Brown Seaweed) via two-stage and three stage sulfuric acid hydrolysis in a batch process. The highest of yield of levulinic acid for two stage hydrolysis was noted as 30.11 mol% (theoretical yield on available glucan) obtained at 200 °C with 120 min retention time. Three stage hydrolysis produces around 28 mol% at 200 °C with 80 min retention time with 4 (% wt) H2SO4. LA can be upgraded to bio-oil using the Thermal Deoxygenation (TDO) pathway. The production of TDO oil from woody biomass derived LA is found to be an energy intensive process. So, energy integration is helpful to minimize overall energy consumption of the renewable fuel production, which eventually reduces the cost of fuel production. We performed energy integration analysis of the combined AHDH and TDO process using the pinch analysis methodology to determine potential energy savings. The combined AHDH and TDO pathway includes: evaporation loads, condensation heat duties, exothermic reaction duties and more efficient use of utility systems. The energy integration analysis is divided into three major tasks: (i) selection of matches, (ii) minimum utility cost estimation, and (iii) determining minimum cost of heat exchanger network. The calculation of the Pinch Point done by theoretical and graphical methods yielded 107 °C and 97 °C for hot and cold streams, respectively. The energy savings of the combined AHDH and TDO pathway to make renewable fuel was evaluated by using data collected from Aspen Plus. The potential energy saving was calculated to be 94.40 MW, which is around 59% of total steam demand. The installation cost of heat exchangers with energy integration is found to be higher, but only moderately so, compared to the process of without energy integration. Overall the total cost savings is estimated to be around 50% reduction of combined utility and capital costs for the heat exchanger network. This improves the overall economic performance of combined AHDH and TDO pathway to make renewable fuel. Thus, the prime objective of energy integration was achieved by increasing process to process heat transfer and by reducing extra utility loads.

Share