Optimization of chemical consumption in biomass delignification

A process to perform a controlled exothermic delignification of biomass, said process comprising the steps of:

• providing a system comprising at least a first vessel and a second vessel;
• providing biomass comprising lignin, hemicellulose and cellulose fibers into said first vessel;
• providing an aqueous acidic composition comprising a sulfuric acid component;
• providing a modifier component;
• providing a peroxide component;
• exposing said biomass to said sulfuric acid component, modifier and peroxide components, creating a reaction mass;
• mixing said reaction mass;
• allowing said sulfuric acid, modifier and peroxide components to come into contact with said reaction mass for a period of time sufficient to a delignification reaction to occur and remove a pre-determined amount of said lignin from said reaction mass;
• wherein said pre-determined amount is assessed by testing a first kappa number, with a first suitable apparatus, of the reaction mass when said first kappa number of said reaction mass is reached a first treated biomass is formed, the first treated biomass is transferred to said second vessel;
• allowing the temperature of the first treated biomass to increase during the residence time of said first treated biomass in said second vessel;
• allowing said sulfuric acid component and peroxide component to continue said delignification reaction at a second temperature and remove a second pre-determined amount of said lignin from said first treated biomass;
• wherein said second pre-determined amount is assessed by testing a second kappa number, with a second suitable apparatus, of the first treated biomass, when said second kappa number of said first treated biomass is reached a second treated biomass is formed, the second treated biomass is then removed from said second vessel;
• optionally, a washing step is employed to separate a resulting liquid portion comprising said lignin and hemicellulose from a solid portion containing the cellulose extracted from the second treated biomass, said washing step thereby forming a washed biomass.