Patent ID: 8709203

Claim:
A process for producing NCC comprising: acid hydrolysis of bleached wood pulp; recovering NCC from said hydrolysis; recovering an aqueous waste liquor from said hydrolysis, said aqueous waste liquor containing acid and sugars derived from said hydrolysis of bleached wood pulp, said sugars comprising a monomeric sugar fraction and an oligomeric sugar fraction; separating said aqueous waste liquor into discrete fractions of aqueous acid, monomeric sugars and oligomeric sugars with a pair of discrete membranes; said separating comprising: a) i) contacting said liquor with a first side of a nanomembrane of said pair selective for the passage of the inorganic acid; ii) recovering an aqueous permeate containing said inorganic acid at a second side of said nanomembrane opposed to said first side and recovering said sugars in a non-permeate of said nanomembrane at said first side; said aqueous permeate having a residual content of sugars in a ratio of less than 0.8%, by weight of sugars to acid; and iii) contacting said non-permeate with a first side of a membrane of said pair selective for said monomeric sugar fraction, recovering an aqueous permeate containing said monomeric sugar fraction at a second side of said membrane opposed to said first side, and recovering said oligomeric sugar fraction as a non-permeate of said membrane at said first side of said membrane; or b) i) contacting said liquor with a first side of a membrane of said pair selective for the passage of said acid and said monomeric sugar fraction; ii) recovering a permeate comprising said acid and said monomeric sugar fraction at a second side of said membrane opposed to said first side; and recovering said oligomeric sugar fraction as a non-permeate at said first side of said membrane; and iii) contacting said permeate comprising said acid and said monomeric sugar fraction with a first side of a nanomembrane of said pair selective for the passage of the inorganic acid; and recovering an aqueous permeate containing said inorganic acid at a second side of said membrane opposed to said first side, said aqueous permeate having a residual content of sugars in a ratio of less than 0.8%, by weight of sugars to acid; concentrating said aqueous permeate containing said inorganic acid and residual sugars from said nanomembrane, without precipitation of sugars or fouling during said concentrating, to an aqueous acid solution having a concentration of acid of 50% to 70%, by weight for acid hydrolysis of bleached wood pulp in NCC production, and recycling said aqueous acid solution as an acid supply to said acid hydrolysis for NCC production.