Patent ID: 6899791

Claim:
A method for producing thermo-mechanical pulp in a primary disc refiner from lignocellulose fiber-containing chip feed material comprising the steps of: first conditioning said fiber containing feed material while conveyed through a first chamber having an environment of saturated steam at an elevated pressure in the range of about 10-25 psig to produce conditioned feed material; conveying and compressing the conditioned feed material through a second chamber having an environment of saturated steam at elevated pressure in the range of about 10-25 psig to produce a pretreated material having destructured fibers without significant breakage across grain boundaries; preheating the pretreated material in a third chamber in an environment of saturated steam at a pressure above 75 psig and above the glass transition temperature of the lignin in the material, for a period of time less than 30 seconds; conveying the pre-heated material to the inlet of a primary disc refiner operating at a pressure above 75 psig and a temperature above the glass transition temperature of the lignin; and refining the material at a disc speed of rotation that is greater than 1500 rpm for a double disc refiner or greater than 1800 rpm for a single disc refiner.