Gas production by almond shell pyrolysis at high temperature

Abstract

The production of gases from almond shell pyrolysis at high nominal temperatures (700–900°C) is discussed, taking into consideration the gaseous products formed by the primary and secondary reactions respectively. Two types of experimental apparatus have been used: (a) an analytical Pyroprobe 100, where the primary reactions take place and in which the cracking of the primary tars evolved can be considered negligible; (b) a fluidized sand bed reactor, where the biomass is decomposed inside the sand bed and the tars formed are cracked in the upper part of the reactor over the sand bed. Both reactors have proved to be suitable for studying the primary and secondary pyrolysis reactions, respectively. The evolution of the primary hydrocarbons and primary carbon monoxide is suggested to take place by very temperature-sensitive mechanisms, whereby the other oxygenated compounds, carbon dioxide, water, acetic acid and methanol + formaldehyde, are formed by mechanisms involving depolymerizations. On considering the formation of the secondary products, correlations between the yields of carbon oxides and hydrogen as well as between methane and ethylene were observed.