Apparatus and process for producing wood pulp in a pressurized wood grinder

Apparatus for producing wood pulp from wood, comprising:

• a pressurized housing, sealed for enabling said housing to be pressurized above atmosphere;
• means for pressurizing said housing;
• a wood grinder in said housing for grinding wood fed against said grinder into wood pulp;
• wood feed means for feeding wood to said grinder;
• water delivery means for delivering water to the zone in said housing where said grinder is grinding wood;
• a wood pulp collector placed for collecting pulp ground by said grinder;
• water removal means connected to said pulp collector for receiving pulp from said pulp collector and for removing water from the pulp received;
• a water return line from said water removal means to said water delivery means for delivering water removed from the pulp to said water delivery means;
• means for also pressurizing said pulp collector and said water removal means above atmosphere, whereby the water in and removed from the wood pulp and passed through said water return line may remain always above atmospheric pressure.