Watervliet's NSSC Recovery
L. J. SCHEID, Director of Manufacturing
Watervliet Paper Company
Watervliet,  Michigan
R. CAREAGA, Engineer
The Babcock and Wilcox Company
New York, New York
INTRODUCTION
The successful operation of this first commercial installation of a Mead
neutral sulphite semi-chemical recovery process at the Watervliet Paper Company has opened new horizons for NSSC pulping. It has proved that the NSSC
pulping process can be economically carried on without stream pollution or
capacity limitations resulting from integration with Kraft cooking.
The Mead Recovery Process was originally developed by the Mead Corporation and piloted at their Sylva, N.C. Mill. (1) When the pilot plant indicated that the process was economically feasible, the Watervliet Paper
Company decided to be first to erect a full mill-size installation (50 tons per
day NSSC pulp). The second such installation, sized for 250 tons of unbleached
corrugating medium production, is currently being started up at Mead Corporation's Heald Division in Lynchburg, Virginia.
PROCESS AND  EQUIPMENT DESCRIPTION
Watervliet is engaged in the production of bleached NSSC pulp for use in
their line of coated papers. The cycle employed consists of cooking aspen
chips in rotary digesters and passing them first through an Anderson extractor
and then an expeller, from which the pressed chips are fed into a refiner to
give unbleached NSSC pulp. The blowdown liquor from the digester is combined with the liquor from the extractor and evaporated from 10-12 per cent
to 33 per cent solids in a triple effect, forced-circulationSwenson evaporator.
The strong black liquor is fed into a venturi scrubber evaporator where it
serves as a scrubbing medium for removing saltcake from the furnace gases,
and is further evaporated to 65 per cent solids. The high thermal absorption
in the venturi (a gas temperature differential of 900 F) allows for low inlet
solids liquor from a smaller bank of evaporators at a lower initial cost. After
going through the venturi, the liquor is burned in a Babcock & Wilcox Kraft
furnace of convential type except that the boiler bank and heat traps have
been omitted.
The ability of a venturi type scrubber to handle 1,100 F gas without fire
hazard permits the use of a smelter type unit which, although producing less
stream, burns thesmall (3,100 lb solids per hr) quantities of liquor more economically, since a venturi used in this manner eliminates the need for expensive boiler bank and heat trap surface (along with surface cleaning costs) and
at the same time serves as an evaporator and chemical recovery device.
The smelt from the furnace is dissolved in a conventional Kraft dissolving
tank, while the concentration of the liquor is held between five and six normal.    It is then put through a single compartment Dorr clarifier with the ac-
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