Kneader Prethickener

September 19, 1997

In 1997 Vincent was awarded a contract for a Model VP-16 screw press that was used in an important pulp & paper application. The order was received from Thermo Black Clawson, the leading American supplier of paper mill machinery. The press is for Papelera Aragua, their client in Cagua, Venezuela.

The application was at a deinking mill that recycled ONP (old news print). Once hydrapulped, the newspaper must be scrubbed to remove ink from the cellulose fibers. This is achieved in a Thermo Black Clawson machine known as a Kneader. In the Kneader the fibers are rubbed against one another in order to separate the ink.


The Kneader requires a furnish with 25% to 30% solids. This is pre-thickened from a flow with 2% concentration by the Vincent screw press. The installation processes 30 MTPD (metric tons of air dry solids per day). The freeness varies considerably, from 150 to 500 csf (Canadian standard freeness).

The Vincent interrupted screw negates the need for a variable frequency drive. This press design uses interruptions in the screw flights with stationary resistor teeth inserted in the gaps. The resulting agitation allows the press to operate consistetly, without co-rotation, over wide ranges of both throughput and feed consistency. The use of an air cylinder actuated discharge cone allows production of press cake of steady solids content.

This job is important to Vincent because it is a step into yet another pulp & paper application: thickening pulp for both wet storage and baling purposes. Frequently there is a need for storage between pulping operations and the paper making machine. Water must be removed, without damaging the fibers, to reduce the storage bulk to a manageable volume. We have one small press operating in this capacity at a Georgia-Pacific mill, so we have confidence our larger presses can do the job.

Issue 67