Exploration of the effect of process variables on the production of high-value fuel gas from glucose via supercritical water gasification Doug Hendry b , Chandrasekar Venkitasamy a , Nikolas Wilkinson a , William Jacoby a,b,⇑ a Biological Engineering Department, University of Missouri, Columbia, MO, USA b Chemical Engineering Department, University of Missouri, Columbia, MO, USA article info Article history: Received 14 July 2010 Received in revised form 26 October 2010 Accepted 1 November 2010 Available online 9 November 2010 Keywords: Glucose Gasification Supercritical water Hydrogen High-pressure equilibrium phase separator abstract A new continuous supercritical water gasification reactor was designed to investigate glucose gasification in supercritical water at high temperatures and low residence times. A 2 3 full factorial experiment was performed to determine the effects of feed concentration, temperature, and residence time on glucose gasification. The temperature levels (750 °C and 800 °C) were higher than ever used, while the residence times (4 and 6.5 s) were shorter than ever used in previous supercritical water gasification studies. The reactor proved capable of attaining higher gasification rates than previously shown with high efficiencies and yields. In addition, the glucose gasification reaction was modeled by estimating activation energy and reaction order of glucose gasification in supercritical water. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Biomass and other carbonaceous materials are converted into smaller molecules at high temperature. In the presence of oxygen, conventional combustion occurs forming carbon dioxide (CO 2 ), water vapor and releasing energy. Pyrolysis and gasification are the most well known alternative thermochemical conversion pro- cesses. However, the same problems that were documented by Chen et al. (1997) and Brage et al. (2000) plague gasification and pyrolysis plants to this day. Several companies have developed var- ious pressure gasification technologies on the demonstration or pi- lot scale (Enerkem, 2010); however, despite years of research, gasification processes are not practiced profitably and reliably any- where in the world (Kruse, 2008). Thermochemical conversion of biomass in supercritical water is a very promising process with a completely different set of problems (Goodwin and Rorrer, 2008). Water is present in all living biomass and dilutes the energy–density of harvested biomass. Removing water from bio- mass requires energy. Therefore, it makes sense to process biomass in water. Unlike conventional pyrolysis and gasification methods, supercritical water (SCW) can be used to gasify biomass without the expensive and energy-intensive step of drying the feedstock (Schmieder et al., 2000). Supercritical water gasification (SCWG) may be superior to gas- ification in air because SCW is a good solvent that creates a homo- geneous solution preventing charring. Supercritical water (SCW) is infinitely miscible in oxygen and air and is a good media for exo- thermic combustion. In the presence of oxygen, biomass undergoes a process called SCW Oxidation (SCWO). Bermejo and Cocero (2006) described SCWO as well as its industrial development and applica- tions. This characteristic highlights the potential for an integrated process in which the heat released by oxidation reactions is con- sumed by endothermic gasification reactions as proposed by Hong and Spritzer (2002) among others. Modell et al. (1978) described the conversion of solid or liquid organics to high energy gas in SCW with an energetically favorable reaction. Modell (1982) de- scribed a method to convert organic fuels or waste materials into useful energy for power generation and/or process heat. For most biomass, burning about one fourth to one third of the mass provides enough energy to gasify the remainder (Venkitasamy et al., 2010). There have also been several studies on downstream processing of gasification products (Sricharoenchaikul, 2009; Yanagida et al., 2009). However, the focus of this report is on endothermic gasification reaction of biomass model compounds to produce fuel gases. In the absence of oxygen, biomass model compounds and other carbonaceous materials gasify in SCW to form mixtures of molec- ular hydrogen (H 2 ), methane (CH 4 ), CO 2 , small amounts of carbon monoxide (CO), ethane (C 2 H 6 ) and water vapor. In this work, water is removed from the permanent vapors in a high-pressure, equilib- rium phase separator leaving a very dry (and valuable) mixture of H 2 , CH 4 , CO 2 , and CO. This mixture has many potential uses mostly because of the high energy density of H 2 and CH 4 (Johnston et al., 2005). On a mass basis, the high heating values of H 2 and CH 4 at 0960-8524/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2010.11.003 ⇑ Corresponding author. Address: 236 Agricultural Engr. Bldg., University of Missouri, Columbia, MO 65211, USA. Tel.: +1 573 882 0456; fax: +1 573 884 5650. E-mail address: jacoby@missouri.edu (W. Jacoby). Bioresource Technology 102 (2011) 3480–3487 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech