Thune's Process.—Mr. A. L. Thune, of Christiana, U.S.A., has recently patented an apparatus for disintegrating wood, which consists of a grinding apparatus connected to a turbine. In this arrangement the grindstone, fixed on a shaft, is worked by a turbine, and the wood, which is used in small blocks, is pressed against the stone by means of a series of hydraulic presses. The fine pulp is afterwards made into thick sheets by means of a board-machine, the pulp, mixed with water, passing down a shoot into a vat beneath, in which is a revolving cylinder covered with wire-cloth, which in its revolution carries with it a certain quantity of pulp in a continuous sheet; this is taken on to an endless travelling belt by means of a small couch-roll, and passes on to a pair of rolls, round the upper one of which the sheet becomes wound, and is removed when sufficiently thick.
[CHAPTER VIII.]
TREATMENT OF VARIOUS FIBRES.
Treatment of Straw.—Bentley and Jackson's Boiler.—Boiling the Straw.—Bertrams' Edge-runner.—M. A. C. Mellier's Process.—Manilla, Jute, etc.—Waste Paper.—Boiling Waste Paper.—Ryan's Process for Treating Waste Paper.
Treatment of Straw.—As a paper-making material, the employment of straw is of very early date, a patent for producing paper from straw having been taken out by Matthias Koops as far back as 1801. The material, however, was used in its unbleached state, and formed a very ugly paper. White paper was not obtained from straw until 1841, but no really practical method of treating this material was devised until about ten years later, in France, when MM. Coupier and Mellier introduced a process which, with subsequent modifications, has been extensively adopted. A great advance in the manufacture of paper from straw has since been effected by the introduction of various boilers, specially constructed for boiling the material at high pressures, and for keeping the alkaline liquors freely circulated amongst the fibre during the progress of the boiling. These boilers are of different forms—being either cylindrical or spherical—and are preferably of the revolving type, which causes the caustic ley employed in the boiling to become uniformly mixed with the fibre. Sometimes the vomiting boilers described elsewhere are used by paper-makers in preference to those referred to.
Bentley and Jackson's Boiler.—This boiler, a representation of which is shown in Fig. 18, is 7 feet in diameter, 18 feet long on the cylindrical surface, with hemispherical ends of Martin-Siemens steel plate 7/16 inch thick in the shell, and ½ inch thick in the ends. It is double riveted in the longitudinal seams, has two manholes 3 × 2, forged out of solid steel plate. Inside are two perforated lifting plates or shelves, each 1 foot wide, ¼ inch thick, the full length of the shell, and secured to the ends by strong angle-irons; it is supported on two turned cast-iron trunnions. These boilers are tested by hydraulic pressure to 120 lbs. per square inch.
Fig. 18.