In a process for converting lingnocellulosic 
biomass to 
ethanol, the improvement of obtaining higher fermentable soluble 
sugar yields by 
drying acid impregnated 
biomass particles, comprising: a) feeding moist 
lignocellulosic biomass into an acid impregnator to render it acid-soaked and draining the acid-soaked 
biomass to about 30% to 35% by weight solids; b) 
dewatering the acid-soaked biomass by 
drying or 
centrifugation to prevent compaction of the biomass and arrive at about 40% to 60% by weight solids; c) subjecting the acid-impregnated biomass to a first-stage 
hydrolysis reactor at a temperature of from 130° C. to 220° C. and discharging formed 
hydrolysate into a flash tank at about 120° C. to 140° C. to hydrolyze most of the remaining soluble oligosaccharides to monomeric sugars, and flashing remaining 
hydrolysate to a second flash tank at a lower temperature than the first flash tank-the second flash tank serving as a feed 
surge tank for a counter-current extractor; d) washing the 
hydrolysate, adjusting the pH of the 
sugar extract to about 5, and recovering more than 95% of the soluble sugars in the first-stage hydrolysate 
slurry by a counter-current extractor; e) subjecting remaining washed-first stage solids of pretreated biomass to a second-stage acid and 
metal salt impregnator and 
dewatering by 
drying or 
centrifugation to prevent compaction of biomass to arrive at 40% to 60% by weight solids; f) subjecting the acid and 
metal salt-impregnated biomass to a second-stage 
hydrolysis reactor at a temperature from 190° C. to 240° C. and discharging formed hydrolysate into a flash tank, at about 120° C. to 140° C. to hydrolyze most of the remaining soluble oligosaccharides to monomeric sugars and flashing remaining hydrolysate to a second flash tank at a lower temperature than the first flash tank, the second flash tank serving as a feed 
surge tank for second-stage fementors; g) cooling pH-adjusted extract from the counter-current extractor, feeding the extract to a first-stage fermentor and 
air sparging the first-stage fermentor at a rate sufficient to promote enough 
yeast growth to compensate for loss through second-stage fermentors; h) pH adjusting second-stage hydrolysate 
slurry to 4.5, cooling the 
slurry and adding it into the top of the first fermentor of a two-fermentor 
train in the second stage fermentors, pumping broth from the bottom of the first stage fermentors to the second stage fermentors while the 
yeast is in the 
growth phase for a period sufficient to consume over 95% of fermentable sugars; and i) recovering 
ethanol.