BEET SUGAR IDUSTRY.

Marlborough Daily Times, Volume X, Issue 314, 25 May 1888, Page 3

BEET SUGAR IDUSTRY.

By J. Salatkay.

manufacturing PROCESS. —(Continued)

Saturation. —This is the first operation which the juice has to undergo in the purifying process. Its principle is based I upon the action of lime upon certain constituents of tho juice, which form, compounds with it, the latter being again precipitated by means of carbonic or sulphurous acid injections. The lime is added in the form of milk of lime of a certain density (for which purpose any waters containing more or less traces of sugar aro used, so that none of the latter is ° wasted), and the quantity required amounts to about 3 per cent of the worked-up beet root. The acids (carbonic or sulphurous) being gaseous, are injected either by means of pumps, or steam injectors, in quantities depending on the desired degree of neutrality of the juice. Formerly these operations used to be divided and performed in separate vessels (defacation and carbonation pans), but now-a-days only one set of vessels is employed for the combined operation, which shortly gets the name “saturation.” The pans (iron or copper) in use for this purpose now, are of a much smaller area than formerly, but they are much higher, which is rather essential, owing to the thick froth which forms during the operation. The latest method of purifying the juice by saturation is gone through in the following manner A quantity of milk of lime equal to 2£per cent of the roots is added to the juice, whereupon carbonic acid is injected until a neutrality of OT4 is reached, i. 0., when the juice contains but OT4 per cent of lime (first saturation). The contents of the pan is then forced through tho filter presses, which will receive our attention in a subsequent place. To tho clear juice resulting from these presses a quantity of milk of limo containg 0-5 per cent (of beet quantity) of lime is added, and by means of carbonic acid injections the liquid is neutralised to about 0-07 (second saturation), upon which it is again forced through the filter presses. The. clear juice is then subjected to the action of sulphurous acid until the alkalinity comes down to almost perfect neutrality (third saturation), when it is forced a third time through the filter presses.

The purifying element in the saturation process is tho lime, while the application of the said acids purposes only its removal from the juice, together with the compounds formed. The visible effects of -the saturation are very plain, for the brown juice leaving the diffusion battery, has now become beautifully clear and of an amber color. This is attributed to the following chemical changes : Nitrogenous substances are decomposed into ammonia, which evaporates ; organic acids are precipitated as calcium compounds ; magnesia, iron and phosphoric acids are also precipitated, while all other inorganic ingredients remain in solution. In the average, it may be stated, about 60 per cent of the non saccharine ingredients are removed out of the juice, the remaining undesirable compounds being chiefly those of sodium and potassium, whose presence is the main cause of molasses resulting in every factory in very large quantities ; up to date all efforts to eliminate these as well have been practically fruitless. Before leaving the saturation process, I may mention a quite recently introduced improvement, which so far has proved very successful in several factories that have adopted it. It consists of the application of strontium saccliarate at the second saturation instead of lime. This compound is easily produced in the factory by simply mixing strontia and molasses in certain proportions. There are said to be surprisingly good results in this method—viz : (1) the sugar in the molasses is regained ; (2) the juice consequently is more concentrated, which is a saving in evaporating expenses; and (3) the strontia can be easily reproduced from its carbonate and used over and over again for tbo same purpose. I believe (from reports received) that this strontia saturation will before be long extensively adopted. This mineral, owing to its saccharates being easily produced, and soluble under certain conditions only, has of late years been in great demand for sugar extraction from molassos ; fortunately very large deposits of it have been discovered in Westphalia and Sicily, and its price is no more a bar to its use for the said purpose in Europe. As auxiliary operations in connection with the saturation, tho lime, carbonic and sulphurous acids production must bo mentioned. This is all done in the factory, with which there is always connected a largo limekiln working. continuously, in which the calcination of limestone produces the lime and carbonic acid, tbe latter being either blown out by special blowors, or pumped out by pumps and forced into tho saturation pans, having previously passed through a “ scrubber,” which is similar to those at gasworks. The quantity of limestone required will of course depend upon it 3 quality, hut may bo put down to be about SS'OOlbs for each ton of beet roots worked up. In some countries carbonic acid is extracted from the gases escaping through the boiler house chimney ; such proceeding, however, should be resorted to only where wood is used for the boiler furnaces, which is the case in Russia. The sulphurous acid is produced by burning sulphur in enclosed furnaces into which compressed air is forced, and from which the gaseous acid escapes by this compression freely into the saturation pans.

Filter Presses. —The carbonic acid and sulphurous acid injections into the saturation pans have the purpose, as I mentioned above, of precipitating the lime together with the compounds formed. This precipitate, which is called (not very appropriately) the “ scum,” has to be separated from the juice, and for this object the “ filter presses” are employed. This apparatus consists of vertical, square, cast iron frames, covered with jute cloth; between these other solid frames with numerous vertical grooves are placed, and tho whole is tightened up by screws. The juice is forced within the cloth-covered frames under pressure, for which purpose pumps are employed in preference to the “montejus,” the clear juice passes through the cloth into the grooved frames whence it is conducted away for further treatment, while the scum is caught withi.i tho jute, where after prolonged work it getß pretty hard, and is henceforth called “scum cake.” Although great care :s taken to wash out as much saccharine matter as possible by hot water and Bteam, yet the scum cakes always contain certain quantities of sugar, which the manufacturer does not like to he wasted. He therefore employs a machine called the “ scum malaxator,” wherein the cakes are worked up to a thick liqqid mass, which is again forced throughafilterpress,theresultiug clear liquid being admixed to the juice at tho second saturation, while the cakes arc pressed and finally removed from the factory. Thero is always a ready sale for these cakes, as they are a vary valuable manure, which I took occasion to refer to previously, in tho chapter on the cultivation of the sugar beet. ‘‘ By the* sale of this ’ ’ (Stohman, a good authority on the beet sugar manufacture, says): “£fhe total expenses of the factory for lime and carbonic fjacid production should Vo I covered.”