Recovery of fines in air laid papermaking

In an air laid papermaking machine apparatus having a moving forming wire, multiple distributors supplying a mixture of fibers in air to the forming wire, at least one suction box beneath the forming wire to draw off the air from under the wire and draw away any fines passing through the forming wire, and a separator receiving the fines and air from the suction box which includes a plurality of separation units, each of which separates the fines from the air carrying the fines and collects the fines until the separation units are controlled to individually discharge the fines into hoppers, the improvement comprising:

• selectively openable manifold conduit damper valves, each connected to the bottom of one of the hoppers, normally blocking the flow of air and fines therethrough, each damper valve being responsive to a control signal to open and allow the contents from the hoppers of the separation units to pass therethrough;
• transfer conduits connected to receive fines passed through the manifold conduit damper valves, the conduits being arranged in a manifold configuration which converges to a collection conduit;
• a transport fan connected to the collection conduit to provide a continuous suction draw on the collection conduit and thereby on the other manifold conduits;
• an outlet conduit, connected to receive the air and fines mixed therewith from the transport fan, which extends to the papermaking machine and is connected to a selected distributor of the papermaking machine which is located at a position downstream of the position at which fiber stock is first laid on the forming wire, whereby the fines delivered back to the papermaking machine will tend to be held on the surface of a mat of fibers already laid on the forming wire rather than passing through the forming wire.

An improved air laid papermaking process comprising the steps of:

• (a) air laying fresh fibers on a moving forming wire of a papermaking machine;
• (b) applying a suction draw to the bottom of the forming wire to draw the fines away from the forming wire;
• (c) carrying the fines and suction air away from the papermaking machine;
• (d) separating the fines from the suction air and collecting the fines in a plurality of separation units;
• (e) discharging the collected fines from the separation units one at a time;
• (f) conveying the discharge fines mixed with air away from the separation units back to the papermaking machine;
• (g) mixing the discharged fines with fresh fiber stock;
• (h) laying the mixture of fresh fiber stock and discharged fines carried in air on the forming wire at a position downstream in the direction of forming wire travel from the position where fresh fiber stock is first laid on the forming wire.