초록
In this work, a novel laboratory-scale direct steam-injection apparatus (DSIA) was developed to overcome the main drawback of the conventional batch-driven lab rigs, namely the long time needed to heat fiber slurry from room to reaction temperatures greater than 150<SUP>o</SUP>C. The novel apparatus mainly consisted of three units: (i) a mechanically-stirred bioreactor where saturated steam at 5-30bar can be injected; (ii) an automatic on-off valve to flash suddenly the reaction medium after a prefixed reaction time; (iii) a cyclone separator to recover the reacted slurry. This system was tested using 0.75dm<SUP>3</SUP> of an aqueous solution of H<SUB>2</SUB>SO<SUB>4</SUB> (0.5%, v/v) enriched with 50kgm<SUP>-3</SUP> of either commercial particles of Avicel<SUP>(</SUP>R) and Larch xylan or 0.5mm sieved particles of Tamarix jordanis. Each slurry was heated to about 200<SUP>o</SUP>C by injecting steam at 28bar for 90s. The process efficiency was assessed by comparing the dissolution degree of suspended solid (Y<SUB>S</SUB>), as well as xylose (Y<SUB>X</SUB>), glucose (Y<SUB>G</SUB>), and furfural (Y<SUB>F</SUB>) yields, with those obtained in a conventional steam autoclave at 130<SUP>o</SUP>C for 30 or 60min. Treatment of T. jordanis particles in DSIA resulted in Y<SUB>S</SUB> and Y<SUB>G</SUB> values quite similar to those obtained in the steam autoclave at 130<SUP>o</SUP>C for 60min, but in a less efficient hemicellulose solubilization. A limited occurrence of pentose degradation products was observed in both equipments, suggesting that hydrolysis predominated over degradation reactions. The susceptibility of the residual solid fractions from DSIA treatment to a conventional 120h long cellulolytic treatment using an enzyme loading of 5.4FPUg<SUP>-1</SUP> was markedly higher than that of samples hydrolysed in the steam autoclave, their corresponding glucose yields being equal to 0.94 and 0.22g per gram of initial cellulose, respectively. Thus, T. jordanis resulted to be a valuable source of sugars for bioethanol production as proved by preliminary tests in the novel lab rig developed here.