State of the art on reactor designs for solar gasification of carbonaceous feedstock M. Puig-Arnavat a,⇑ , E.A. Tora b , J.C. Bruno c , A. Coronas c a Chemical and Biochemical Engineering Department, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark b Chemical Engineering & Pilot Plant Department, Engineering Division, National Research Centre, El-Buhoos St., 12311 Dokki, Cairo, Egypt c Mechanical Engineering Department, Universitat Rovira i Virgili, Avda Paı ¨sos Catalans 26, 43007 Tarragona, Spain Received 9 April 2013; received in revised form 31 July 2013; accepted 2 August 2013 Available online 30 August 2013 Communicated by: Associate Editor Michael Epstein Abstract The association of concentrated solar energy and biomass gasification has often been suggested as an interesting alternative to con- ventional autothermal processes where a significant portion of the biomass has to be used for heat generation to drive endothermic reac- tions. It is a clean process able to produce high quality synthesis gas with a higher output per unit of feedstock and that allows for the chemical storage of solar energy in the form of a readily transportable fuel, among other advantages. The present paper describes the latest advances in solar thermochemical reactors for gasification of carbonaceous feedstocks. This work is categorized in this paper into patents and research/journal papers. Ó 2013 Elsevier Ltd. All rights reserved. Keywords: Solar reactor; Biomass; Gasification; Carbonaceous materials; Syngas 1. Introduction Nowadays, renewable energy sources are in the spotlight due to the increasing awareness and concern about the depletion of fossil fuels, energy dependency, and global cli- mate change. The use of biomass presents significant envi- ronmental benefits. It is widely available, CO 2 -neutral, allows continuous power production and synthesis of dif- ferent products. Among existing biomass conversion tech- nologies, biomass gasification offers high conversion efficiency and the possibility to handle different bio-feed- stocks for a wide variety of applications (heat, electricity, chemicals and transport fuels). Biomass gasification is a thermochemical process that converts, through partial oxi- dation at high temperatures, solid biomass into fuel gas, small quantities of char, ash and several condensable com- pounds (tars and oils). Gasification and pyrolysis are the thermochemical pro- cesses for biomass conversion that have been mostly associ- ated with solar energy during the last 30 years (Gregg et al., 1980a,b; Antal et al., 1983; Mathur et al., 1983; Perkins et al., 2008; Melchior et al., 2009; Martinek et al., 2012; Kalinci et al., 2013). Biomass gasification is globally an endothermic thermochemical conversion process and the heat required is usually supplied in situ by several exother- mic steps. In autothermal gasifiers, fed by air or O 2 , a large amount of the biomass feedstock is combusted to supply high-temperature process heat for the endothermic gasifica- tion reactions. This amount ranges between 5% and 25%, considering hot gas efficiency, and around 25–35% for cold gas efficiency. Piatkowski et al. (2009) considered that an autothermal coal gasifier running with bituminous coal requires at least 35% of the introduced coal mass to power the gasification reaction. Hebecker et al. (2005) estimated a 0038-092X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.solener.2013.08.001 ⇑ Corresponding author. Tel.: +45 21128120. E-mail address: mpar@kt.dtu.dk (M. Puig-Arnavat). www.elsevier.com/locate/solener Available online at www.sciencedirect.com ScienceDirect Solar Energy 97 (2013) 67–84