Page:EB1911 - Volume 26.djvu/57

Rh The use of multiple-effect evaporation made it possible to raise  the steam for all the work required to be done in a well-equipped   factory, making crystals, under skilful management,   by means of the bagasse alone proceeding from the   canes ground, without the aid of other fuel. The bagasse  so used is now commonly taken straight from the cane   mill to furnaces specially designed, for burning it, in its moist   state and without previous drying, and delivering the hot gases   from it to suitable boilers, such as those of the multitubular type   or of the water-tube type. The value of fresh bagasse, or as it  is often called “green” bagasse, as fuel varies with the kind of   canes from which it comes, with their treatment in the mill, and   with the skill used in firing; but it may be stated broadly that   1 lb of fresh bagasse will produce from 1&half; lb to 2&frac14; lb of steam,   according to the conditions. The use of preparing rolls with corrugations, to crush and equalize  the feed of canes to the mill, or to the first of a series of mills, has    become general. The Krajewski crusher has two such  steel rolls, with V-shaped corrugations extending longitudinally   across them. These rolls run at a speed  about 30% greater than the speed of the first mill, to which they   deliver the canes well crushed and flattened, forming a close mat of   pieces of cane 5 to 6 in. long, so that the subsequent grinding can  be carried on without the stoppages occasioned by the mill choking   with a heavy and irregular feed. The crusher is preferably driven  by an independent engine, but with suitable gearing it can be driven   by the mill engine. The Krajewski crusher was invented some years  ago by a Polish engineer resident in Cuba, who took out a patent   for it and gave it his name. The patent has expired. The increase  in the output for a given time obtained by the use of the Krajewski   crusher has been estimated at 20 to 25% and varies with the quality   of the canes; while the yield of juice or extraction is increased by   1 or 2%. The process of continuous defecation which was introduced into  Cuba from Santo Domingo about 1900 had by 1910 borne the   test of some ten years’ use with notable success. The  Hatton defector, which is employed for working it,   has been already described, but it may be mentioned   that the regulation of the admission of steam is now simplified   and secured by a patent thermostat&mdash;a self-acting apparatus   in which the unequal expansion of different metals by heat actuates,   through compressed air, a diaphragm which controls the steam   stop valve&mdash;and by this means a constant temperature of 210° F.   (93.3° C.) is maintained in the juice within the defector during   the whole time it is at work. Earthy matter and other matter precipitated and fallen on the  copper double bottom may be dislodged by a slowly revolving   scraper&mdash;say every twelve hours&mdash;and ejected through the bottom   discharge cock; and thus the heating surface of the copper bottom   will be kept in full efficiency. With ordinary care on the part of  the men in charge Hatton defectors will work continuously   for several days and nights, and the number required to deal with   a given volume of juice is half the number of ordinary defectors   of equal capacity which would do the same work; for it must be   borne in mind that an ordinary double-bottomed defector takes   two hours to deliver its charge and be in readiness to receive a   fresh charge, i.e. 20 minutes for filling and washing out after emptying;   60 minutes for heating up and subsiding; and 40 minutes   for drawing off the defecated juice, without agitating it. Apart  from increased yield in sugar of good quality, we may sum up the   advantages procurable from the use of Hatton defectors as follows:   cold liming; heating gently to the temperature required to coagulate   the albumen and not beyond it, whereby disturbance would ensue;   the continuous separation of the scums; the gradual drying of the   scums so as to make them ready for the fields, without carrying   away juice or requiring treatment in filter presses; and the continuous   supply of hot defecated juice to the evaporators, without   the use of subsiding tanks or eliminators; and, finally, the saving   in expenditure on plant, such as filter presses, &c., and wages. Beetroot Sugar Manufacture.&mdash;The sugar beet is a cultivated  variety of Beta maritima (nat. ord. Chenopodiaceae), other   varieties of which, under the name of mangold or mangel-wurzel,   are grown as feeding roots for cattle. About 1760 the Berlin apothecary Marggraff obtained in his  laboratory, by means of alcohol, 6.2% of sugar from a white   variety of beet and 4.5% from a red variety. At the present  day, thanks to the careful study of many years, the improvements   of cultivation, the careful selection of seed and suitable   manuring, especially with nitrate of soda, the average beet   worked up contains 7% of fibre and 93% of juice, and yields   in Germany 12–70%, and in France 11.6% of its weight in sugar. In Great Britain in 1910 the cultivation of beet for sugar was  being seriously undertaken in Essex, as the result of careful   consideration during several years. The pioneer experiments  on Lord Denbigh’s estates at Newnham Paddox, in   Warwickshire, in 1900, had produced excellent results, both in   respect of the weight of the beets per acre and of the saccharine   value and purity of the juice. The average weight per acre  was over 25&half; tons, and the mean percentage of pure sugar in the   juice exceeded 15&half;. The roots were grown under exactly the  same cultivation and conditions as a crop of mangel-wurzel&mdash;that   is to say, they had the ordinary cultivation and manuring   of the usual root crops. The weight per acre, the saccharine  contents of the juice, and the quotient of purity compared   favourably with the best results obtained in Germany or France,   and with those achieved by the Suffolk farmers, who between   1868 and 1872 supplied Mr Duncan’s beetroot sugar factory at   Lavenham; for the weight of their roots rarely reached 15 tons   per acre, and the percentage of sugar in the juice appears to have   varied between 10 and 12. On the best-equipped and most  skilfully managed cane sugar estates, where the climate is   favourable for maturing the cane, a similar return is obtained. Therefore, roughly speaking, one ton of beetroot may be considered  to-day as of the same value as one ton of canes; the   value of the refuse chips in one case, as food for cattle, being   put against the value of the refuse bagasse, as fuel, in the other. Before beetroot had been brought to its present state of perfection,  and while the factories for its manipulation were worked   with hydraulic presses for squeezing the juice out of the pulp   produced in the raperies, the cane sugar planter in the West   Indies could easily hold his own, notwithstanding the artifcial   competition created and maintained by sugar bounties. But  the degree of perfection attained in the cultivation of the roots   and their subsequent manipulation entirely altered this situation   and brought about the crisis in the sugar trade referred   to in connexion with the bounties (see History below) and   dealt with in the Brussels convention of 1902.

In beetroot sugar manufacture the operations are washing,  slicing, diffusing, saturating, sulphuring, evaporation, concentration   and curing. Slicing.&mdash;The roots are brought from the fields by carts, canals  and railways. They are weighed and then dumped into a washing  machine, consisting of a large horizontal cage, submerged in water,   in which revolves a horizontal shaft carrying arms. The arms are  set in a spiral form, so that in revolving they not only stir the   roots, causing them to rub against each other, but also force them   forward from the receiving end of the cage to the other end. Here  they are discharged (washed and freed from any adherent soil)   into an elevator, which carries them up to the top of the building   and delivers them into a hopper feeding the slicer. Slicers used  to be constructed with iron disks about 33 to 40 in. diameter,  which were fitted with knives and made 140 to 150 revolutions   per minute, under the hopper which received the roots. This  hopper was divided into two parts by vertical division plates,   against the bottom edge of which the knives in the disk forced   the roots and sliced and pulped them. Such machines were good  enough when the juice was expelled from the small and, so to   speak, chopped slices and pulp by means of hydraulic presses. But hydraulic presses have now been abandoned, for the juice is  universally obtained by diffusion, and the small slicers have gone   out of use, because the large amount of pulp they produced in   proportion to slices is not suitable for the diffusion process, in   which evenly cut slices are required, which resent a much greater   surface with far less resistance to the diffusion water. Instead  of the small slicers, machines made on the same principle, but   with disks 7 ft. and upwards in diameter, are used. Knives are  arranged around their circumference in such a way that the hopper   feeding them presents an annular opening to the disk, say 7 ft. outside diameter and 5 ft. inside, with the necessarily division plates  for the knives to cut against, and instead of making 140 to 150   revolutions the disks revolve only 60 to 70 times per minute. Such a slicer is capable of efficiently slicing 300,000 kilos of roots  in twenty-four hours, the knives being changed four times in that   period, or oftener if required, for it is necessary to change them   the moment the slices show by their rough appearance that the   knives are losing their cutting edges. Diffusion.&mdash;The diffusion cells are closed, vertical, cylindrical  vessels, holding generally 60 hectolitres, or 1320 gallons, and are   arranged in batteries of 12 to 14. Sometimes the cells are erected  in a circle, so that the spout below the slicing machine revolving   above them with a corresponding radius can discharge the slices   into the centre of any of the cells. In other factories the cells  are arranged in lines and are charged from the slicer by suitable   telescopic pipes or other convenient means. A circular disposition  of the cells facilitates charging by the use of a pipe rotating above   them, but it renders the disposal of the hot spent slices somewhat