Rapid High Temperature Solar Thermal Biomass Gasification in a Prototype Cavity Reactor

Abstract

High temperature biomass gasification has been performed in a prototype concentrated solar reactor. Gasification of biomass at high temperatures has many advantages compared with historical methods of producing fuels. Enhancements in overall conversion, product composition ratios, and tar reduction are achievable at temperatures greater than 1000°C. Furthermore, the utilization of concentrated solar energy to drive these reactions eliminates the need to consume a portion of the product stream for heating and some of the solar energy is stored as chemical energy in the product stream. Experiments to determine the effects of temperature, gas flow rate, and feed type were conducted at the high flux solar furnace at the National Renewable Energy Laboratory, Golden, CO. These experiments were conducted in a reflective cavity multitube prototype reactor. Biomass type was found to be the only significant factor within a 95% confidence interval. Biomass conversion as high as 68% was achieved on sun. Construction and design considerations of the prototype reactor are discussed as well as initial performance results.

High temperature thermochemical processing of biomass and methane for high conversion and selectivity to H2-enriched syngas

“…The products of combustion, then, do not degrade the value of the product syngas. This is exemplified in, but not limited to, solarthermal reactor systems, operating at high temperatures while avoiding emissions from combustion reactions [37]. Since allothermal designs would require more energy input per mass of feedstock processed, concentrating solar radiation may negate this extra energy penalty and potentially allow for a net-zero lifecycle emissions for the primary conversion reactor.…”

“…Allothermal designs offer simpler operation based on blending of three reactants where external energy is converted directly to chemical energy via endothermic steam-reforming and steam-gasification reactions [35][36][37]. The products of combustion, then, do not degrade the value of the product syngas.…”

“…Receivers have been designed and operated in particle-flow configurations under simulated and 'on-sun' conditions specifically for metal oxide dissociation or water splitting [38][39][40], methane decomposition [41][42][43], and steam-gasification of carbon [35,[44][45][46][47]. Reactor designs are dichotomized into categorizations where the reacting media is either directly or indirectly irradiated, the latter employing absorbers to transfer heat conductively such as in the case of a multiple tubular reactor where the absorbers are opaque and composed of a refractory material able to withstand high temperatures and large temperature gradients [37]. In the presence of oxidizers such as steam, the absorbers are typically formed from sintered silicon carbide or alumina and exhibit maximum long-term operating temperatures around 1923 K. Unfortunately, there are limited instances of solarthermal operation above 1600 K for the purpose of gasifying carbonaceous feedstock [48].…”

Estudo da utilização de concentradores solares para o processo de gaseificação de biomassa - concepção de um reator químico solar.

“…Figura 2.12 -Processos de produção de combustíveis solares (Steinfeld e Meier, 2004 Figura 2.14 -Gaseificador de leito fixo de Gregg et al (1980) Figura 2.15 -Gaseificador de leito fixo de Taylor et al (1983) Figura 2.16 -Gaseificador de leito fluidizado de Taylor et al (1983) Kodama et al (2002) Figura 2.20 -Gaseificador de leito fixo de Piatkowski et al (2009 Melchior et al (2009 Lichty et al (2010 de Chen et al (2010) 53 Figura 2.24 -Gaseificador de leito fluidizado de Kodama et al (2010) (Trommer et al, 2005 de Godinez et al, 2012 Luz et al (2015) e de Nio et al (2013) (Luz et al (2015) (Luz et al,2015 (Trommer et al, 2005) Analisando a Tabela 1.1, conclui-se que o uso da energia solar concentrada potencialmente mais que dobra a geração de energia elétrica a partir de uma quantidade específica de biomassa e apresenta uma redução de 14,7% nas emissões específicas de CO 2 . Assim, espera-se comprovar benefícios da gaseificação de biomassa similares aos resultados da Tabela 1.1, obtidos da gaseificação do coque de petróleo.…”

“…Apesar do vórtice constante dos reagentes, nota-se que não há nenhum material que ajude a promover a absorção da radiação; neste caso, as próprias partículas de material carbonáceo recebem esta energia, o que implica em ineficiência. Lichty et al (2010) Este reator consiste em tubos simples que possuem uma seção transversal de altíssima temperatura, em que o choque térmico causa a rápida gaseificação da biomassa. Nota-se um potencial para a utilização em escala comercial deste tipo de equipamento devido a sua simplicidade de operação.…”