Dec., 1 9 1 2
T H E JOL-R-VAL OF I S D L - S T R I A L A I Y D E-\-GIAYEERIA\-G C H E - U I S T R Y .
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CURRENT INDUSTRIAL NEWS B Y IT. A . H A M O R .
“VITREOSIL” I N THE NITRIC ACID INDUSTRY. “Vitreosi1” has not been so extensively used in the manufacture of nitric acid as in the sulphuric acid industry. T~~~is attributable to the difficulties encountered in manipulating molten quartz and to the fact that retorts, receivers, etc,, used in the manufacture of nitric acid are larger than could be made until recently. However, smaller forms of apparatus intended for such a purpose, as conduits and still-heads for the Valentiner apparatus, still-heads for the Guttmann system, and built-up pipe ranges and condensers, have been on the market for some time, and recently “vitreosil” denitrating towers have been announced. “Vitreosil” denitrating towers are a n improvement over those of earthenmare, as they allow the use of superheated
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steam; as is well-known, stoneware has the disadvantage of liability to break through temperature changes. The whole apparatus illustrated herewith is constructed of “vitreosil.” The usual size of the tower TI is 2 5 0 in diameter and 2 2 9 0 mm. in height, and it consists of three tubes, each about 760 mm. in length. When a tower of this size is heated with steam a t 2o0° C.,and the nitric acid present amounts to j per Cent., 8 tons of mixed acids ma? be denitrated Per 24 hours. The superheated steam enters through a tube in the center of the base, and the tube is so formed that the steam can only move upwards. The nitric acid vapors are conducted from the upper part of the tower T, to an air-condenser which is composed of five “vitreosil” condensation vessels (\’) O f 75 liters content. The exit gases are led into a n e n d - t o w r (scrubber) T, which is Packed with Pieces of quartz. The whole is DEVELOPMENT O F THE SULPHITE INDUSTRY. In a recent lecture before the A4ustro-HungarianCellulose and Paper-Stuff Association, a n interesting resume of the beginnings and progress of the sulphite pulp industry was given by E . Spiro, from which the following is extracted by Paper, 9, No. 7, 2.5.
B. Tilghmann, of America, took out an English patent in 1866 for a process of obtaining cellulose from wood. The essential feature of his method was boiling the lvood with solutions of bisulphites of the alkalies or alkaline earths. Tilgh-
mann’s Patent was a failure, and it was not till more than ten Years later that Mitscherlich, Kellner, and Ekman put the manupulp On a basis. facture Of The manufacture of sulphite pulps consists of four stages: I. The preparation O f the wood. 2. The preparation Of the ‘yes. 3. The 4. The breaking up of the boiled wood, and the rinsing, sorting fibers. and drying Of the In the time of Mitscherlich the knots were drilled out and the wood then cut up with circular s a w into lengths of about a n inch and a quarter. This procedure had several disadvantages. I t 15-as expensive and tedious, and, like every other process involving the use of the circular saw, very dangerous to the work people. Accidents 71-ere constantly occurring. -4gain, the thick discs of wood required long boiling in very strong lye. Against all this, hoTvever, we have the fact that the cellulose obtained was stronger than has since been got by more modern processes. The sawdust was boiled up with the discs for economy’s sake, and inevitably contained portions of the knots. These impurities caused numerous dark specks in the finished pulp. Dark specks also often appeared in the pulp for another reason: the high temperature prevailing during the boiling under a pressure of several atmospheres, reached the interior of the discs before the lye and actually charred the still dry wood. Cutting the discs thinner was, of course, a remedy, but involved the expenditure of more money and time in the sawmill. Ritter, Kellner, Ekman, Flodquist, and Francke used revolving chopping machines, and so reduced the waste that it could be neglected and did not have to be boiled up with the lye. When the sawmill was used, so much sawdust was produced that it was imperative to work it into cellulose as well as the discs. Kellner was the first to see that the wood had to be divided into smaller pieces. Hence he originated the application of a grinding process to the chips. His grinding apparatus consisted of a series of conical cast-iron grinders revolving on a vertical axle. These grinders were ribbed, as was the interior of the chamber in x5-hichthey revolved, The chamber was, of course, provided with a hopper above for feeding in the chips and with an outlet belolv for the ground The TT.OOd divided in this mill parallel to the direction of the fiber, and the previous remoyal of the knots a nlatter of fact, supposed to be avoided, the the case, The grinding broke up the knots so small that the impurities TT-ere Jyidely distributed through the pulp. H e was, therefore, obliged to return to the This he did of removing the knots before grinding, xT-ith special machines, very small circular revolving a t a very higil speed, ~t the sa,71e time, he found that a specially constructed chopping TyaS necessary to get pieces small enough to be properly ground in the mill. The use of this machinery was found to entail considerable danger to the workmen. with its attendant consequences of actions for damages and demands for higher wages. Hence the introduction of the centrifugal mill with a n axle armed bv steel spikes revolving in a chamber from the inner nalls of which similar spikes project. Even 11 ith the mills it was impossible to prevent the occurrence of knot debris in the pulp, and this had to be sorted out by perforated drums, similar to those used for sorting broken stone. These imperfections have led to the
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