Indian Patent Application Number: 6367/CHENP/2013 As Amended on 29 July 2019 – Clear Copy
WE CLAIM:
1. A method for producing a sugar liquid, said method comprising the step of filtering a cellulose-derived sugar liquid through one or more separation membranes selected from the group consisting of ultrafiltration membranes, nanofiltration membranes and reverse osmosis membranes, characterized in that the method comprises the step of washing the separation membrane(s) after the filtration with warm water at a temperature of not less than 50°C, and said warm water comprises one or more low-molecular-weight aromatic compounds selected from the group consisting of HMF, furfural, coumaric acid, ferulic acid, coumaramide, ferulamide and vanillin at a total concentration within the range of from 50 to 10000 ppm.
2. The method for producing a sugar liquid as claimed in claim 1, wherein said warm water is a filtrate obtained by passing a cellulose-derived sugar liquid through a nanofiltration membrane(s) and/or reverse osmosis membrane(s).
3. The method for producing a sugar liquid as claimed in claim 1 or 2, wherein the temperature of said warm water is within the range of 75 to 90°C.
4. The method for producing a sugar liquid as claimed in any one of claims 1 to 3, wherein said cellulose-derived sugar liquid is a cellulose-derived sugar liquid filtered through a microfiltration membrane(s).
5. The method for producing a sugar liquid as claimed in any one of claims 1 to 4, wherein the pH of said warm water is within the range of 9 to 12.
6. The method for producing a sugar liquid as claimed in any one of claims 1 to 5, wherein said separation membrane(s) is/are washed by cross-flow filtration of said warm water through the separation membrane(s).
7. The method for producing a sugar liquid as claimed in claim 6, wherein the linear velocity of said warm water on the membrane surface is 5 to 50 cm/s.