Selective delamination of wood chips

Claim 1

A selective delamination process for producing a high yield, uniform pulp having reduced pulp screen rejects, which comprises: a. conveying a mill-wood chip stream to a primary means for separating by size the chip stream into respective first and second fractions on the basis of a chip thickness of about one-fourth inch, said first fraction consisting of wood chips having a thickness equal to or greater than about one-fourth inch and being retained by said primary separation means, and said second fraction consisting of wood chips having a thickness of less than about one-fourth inch; b. conveying said first chip fraction to a means for reducing the size of said first chip fraction without imparting substantial compressive forces thereto and without substantial reduction in the fiber length of the chips in said first wood chip fraction; c. conveying said reduced chip fraction to a secondary means for separating by size said reduced chip fraction into respective oversized and through-put chip fractions, the oversized chip fraction consisting of wood chips having a thickness equal to or greater than about one-fourth inch and being retained by said secondary separation means and said through-put fraction consisting of wood chips having a thickness of less than about one-fourth inch, said through-put fraction being more susceptible to liquor penetration during pulping than chips having a larger thickness; d. reconveying said oversized chip fraction to said reducing means for further reduction of said oversized chips and reconveying said reduced chips produced thereby to said secondary separation means; e. selectively delaminating said through-put fraction, at a substantially high through-put rate, by feeding same to a compression means; and f. pulping said second chip fraction and said selectively delaminated fraction, respectively to produce wood pulp.