Pulp Thickeners at Weyerhaeuser’s Sulfite Pulp Mill, Longview, Wash.
A StaffilndustruCoUaborative Report
e e e
WILLIAM Q. HULL Associate Editor in collaboration with
I
R. E. BAKER
C . E. ROGERS
Weyerhaeuser Timber Co., Longview, Wash.
The Babcock & Wilcox Co.,Alliance, Ohio
N THE world’s first sulfite pulp mill, constructed by the
Swedish chemist, C. D. Ekman, a t Bergvik, Sweden, in 1874, magnesium bisulfite was used for a period of time as a base for the preparation of the cooking acid (1). As the process developed and came into general use, however, limestone was almost universally adopted because of its widespread availability and low cost. I n relatively recent years magnesia-base pulping has again received serious consideration and the first full-scale commercial plant utilizing the process is in operation. The sulfite process is second only to kraft as a source of chemical wood pulp; production by the sulfite process in the United States in 1950 was approximately 3,000,000 tons (Table I). Its origin is generally attributed to the efforts of Tilghman, who was granted a patent in 1876 entitled, “Treating Vegetable Substances for Making Paper Pulp” (IO). Tilghman originally proposed lead-lined, cylindrical vessels as digesters and numerous
mechanical difficulties resulted. Ekman, presumably unaware of the Tilghman patents, equipped his mill with small rotating digesters heated indirectly by means of steam jackets. During this same period, A. Mitscherlich developed a process in Germany using horizontal, stationary cylindrical digesterti, indirectly heated by coiIs of lead pipe, in the place of Ekman’s rotating vessels, and Eugene Ritter and Carl Kellner, in Austria, operated mills in which steam was admitted directly into the cooking vessel. The first Rulfite mill in the United States, built by Charles 5. Wheelwright in East Providence, R. I., was based on Ekman’s work. A few years later, in 1887, the first Mitscherlich mill in this country was constructed in Alpena, Mich. Today, chemical pulp is made by three basic processes-kraft, sulfite, and soda. I n earlier reports in this series, the history and manufacture of kraft pulp and paper were described in detail, and a comparison of process and product characteristics of the three 2424
November 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY -~
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TRADE GLOSSARY
Total sulfur dioxide : Total SO2, determined by titration aacording to TAPPJ Standard T-604m1 expressed as per cent total SO2 Free sulfur dioxide (“available” SO2): Sum of actual free,S02 plus one half the SO2 combined as bisulfite, determined by titration according to TAPPI Standard T-604m1 expressed aa per cent free SO2 Combined sulfur dioxide (“nonavailablo” SOZ): SO2 combined with base as monosulfite, determined by difference of free SO2 and total SOz, expressed as per cent combined SO2 Sulfur dioxide: SO2 as made by burning sulfur or pyrit
