No. V. Technology. Part II. THE PRESS ROOM. Before proceeding with the description of the treatment of the beet root juice after it has left the hydraulic presses, we shall dwell for a few minutes upon some very important, although apparently trivial details, which, for the sake of clearness only, we omitted in our previous article. Work in a beet root sugar factory being continuous through the day and night, without interruption, it is essential that at least twice during every twenty-four hours, the whole of the press room, with all that portion of the included apparatus which comes into immediate contact with the juice, should be most thorougMy cleaned and purified. This is best done at midday and at midnight, when a stoppage of half an hour will generally suffice. The material used for this purpose is water in large quantity, to which a small amount of slaked lime has been added in order to render it alkaline. Not only must the whole of the stone or marble floor of the press room be thus thoroughly scoured with hard brooms, but also the press tables and their guides, the monte-jus, the reservoir for juice, and all other utensils. The sheet-iron trays must also be scrubbed with a hard brush in hot lime water, in an iron tank, at least twice a week. The above precautions are absolutely necessary in order to prevent the occurrence of fermentation of the juice, one of the accidents most to be dreaded during the whole process of manufacturing sugar from beets. When once fermentation has taken a foothold in the works, it is generally found to maintain itself there with aggravating persistency, being constantly propagated anew, through minute particles of ferment, remaining in nooks and corners, where they can hardly be destroyed by any amount of labor. Instances are on record where the manufacture of sugar has had to be interrupted for whole weeks from this cause alone. Cold weather being unfavorable to fermentation, it seldom proves troublesome during the winter, but without necessary precautions, it is certain to be of frequent occurrence during autumn and spring, when the temperature is higher. This same cause precludes the possibility of profitably manufacturing beet root sugar during the summer months, which would otherwise be practicable in our Southern States, where two crops of beets can be raised during the year. For the same reason also, the press room must never be artificially heated to over 60 Fah., which will bo sufficient to keep the workmen comfortably warm if they wear, as they should, winter clothing and water-tight boots. In some localities in Europe, where labor is cheap, the pulp is pressed a second time in hempen sacks, after having been sprinkled with water, but in the United States, we believe that it will prove more profitable to lose 1, or even 2 per cent of sugar (which will be [transformed into fat in the animals fed on the refuse pulp) than to incur the expense of this second pressing. Beet root, pulp will keep for months in trenches, which are best lined with brickwork, the pulp being compressed into them by means of a rammer, and then covered with straw and a thick coat of earth. It undergoes a partial fermentation after a period of a few weeks, which only tends to make it more palatable to farm stock. It is fed to cattle, sheep, etc., mixed in various proportions with bran, cut straw, wheat chaff, meal, oilcake, or some other nutritious substance. In order to prevent long-continued use from rendering it distasteful to the animals, it is generally found advantageous to slightly salt it by sprinkling with salt and water at the time of serving it. Some of the mixtures which are considered the best for the feeding of live stock in Europe, are the following, every twenty-four hours For fattening an ox: 50 lbs. well pressed pulp, 12 lbs. hay, 3 lbs. oil cake. For fattening a wether : 8 lbs. pressed pulp, lb. dry fodder. For feeding a ewe : 2-1 lbs. pressed pulp, $- lb. of dry fodder. The proportions of these mixtures may, however, be varied by intelligent raisers of domestic animals so as to suit their exigencies. THE WOOLEN SACKS. The pulp sacks have to be made of a lax, wide-meshed tissue, the wool having to be twisted and coarse. The part of the fleece generally considered of lowest value for weaving into cloth, is, for our particular purpose, the best, as it is cheapest, most durable, and not so liable to shrinkage, as is wool of fine quality. The sacks must be washed as often as they become soiled or " greasy." This is done by means of a sack-washing machine driven by power, of which many kinds are in use, the simplest of which is a revolving gridiron cylinder, with a central rotating arm-bearing axle. The water used in all cases must be boiling hot, and contain a certain amount of lime (milk of lime), potash, or soda, in order to detach all fatty or slimy adherent particles. The ammonical waters from the evaporating apparatus may also be advantageously employed for this washing of sacks. Immediately after leaving the washing machine, the sacks are to be rinsed in clear cold water. In ordinary winter weather a set of sacks in actual service, will need only one washing and rinsing every six hours, bat if any appearances of fermentation are manifest in the press room, or if the temperature of the air be high, they will need more frequent manipulation. After the rinsing, the sacks are hung up to drip and dry, or the water is pressed out of them by placing them in sets of from five to ten between sheet-iron trays under a hy-; draulic press. If the washing and rinsing have been properly performed, the sacks will have no peculiar odor, and will not feel slimy to the touch. In order to protect the sacks and save the pulp during the operation of pressing, it is necessary to fold them the length of their anterior quarter; thus: After this, the thickness of the pulp must be equalized by means of four or five strokes given with a short wooden roller. The sacks are laid on the trays with the folded part upward. Practiced workmen spread the pulp with the hand without a roller. The folding and equalizing of the pulp are effected on a small, but heavy side table provided for this special purpose and placed near the presses. It is important that the sacks should be well shaken out when the pulp is dropped out of them, and that no pulp be left lurking in the lower corners, to effect which it is best to turn them inside out every time they are washed. The sacks used for the scums (of which we shall have more to say in a future article) are washed, and rinsed in the same manner as the pulp sacks, at least twice in twenty-four hours. It is better to do it thrice than twice. This item, " sacks," is one of considerable importance, as may be judged from the fact, that a factory working 150,000 pounds of beets per day, will send to the washing machine no less than 900 to 1,000 sacks every six hours. Each of these sacks has to be overhauled after rinsing, and the torn or injured ones sent to the darning room, where a number of operatives are kept constantly employed repairing damages. Even with the greatest care taken to keep the pulping drum in right order, and also to seeing that the presses do not rise too fast, the wear and tear in sacks during a campaign are always such as must be taken into account in all calculations of cost of production of beet root sugar. The price of sacks varies in Europe from 50 to 75 cents, so that we may estimate the first cost of a full set of them, for a 500-acre factory, at no less than $2,000. The sheet-iron trays are about one line in thickness, and are made 1-J inches broader than the intercalated sacks, so as to avoid protrusion of these last during the operation of pressing out the juice. The angles of these trays must be rounded off, so as to avoid injury to those who have to handle them. About 4,000 trays suffice for an establishment such as we have taken for an example, and would cost $1,000. The price of a good Back-washing machine and connections is $110. Total, in gold, for sacks, trays, and washing machine, $3,110. DEFECATION OF THE JUICE. After the beet root has been washed, pulped, and submitted to the action of the hydraulic presses (or to that of any other method of juice extraction), the liquid product is, as we have previously stated, collected in a special reservoir. If the best root juics consisted simply in sugar and water, the further processes of manufacture would be simple in the extreme, as boiling down or concentration would give us, in one operation, crystallizable sugar ; but, as we have shown in Art. II., the sap of the beet root exhibits a long array of contained soluble substances and impurities, all of which have to be eliminated during the subsequent treatment of the juice, necessitating the aid of chemical science in addition to the use of mechanical means. The various substances to be removed from the beet root juice may practically be divided into two classes; first, those which can be removed before crystallization of the sugar; and second, those which cannot. The first class of these bodies is, by our modern processes, in a great measure eliminated by the combined action of heat and the use of lime, the operation being known as the " defecation" of the juice. During defecation, a certain portion of the sugar combines with some of the lime used, forming a particular body the saccharate of lime. From this saccharate of lime the sugar has to be freed again in order not to be lost by the action of carbonic acid gas, which, having a greater afiinity for the lime, combines with it, forming insoluble carbonate of lime, while it liberates the combined sugar, which is then ready for further treatment. This last process is called the " carlonatation " of the juice. We shall now proceed to exhibit in as practical a manner as we can, the ordinary, most simple, and most generally practiced processes of defecation and of carbonatation, and shall follow them, by a summary of the more recent improvements proposed by Perier-Possoz and by Jelinek, the first of these, consisting in a series of successive defecations and carbonata-tions, and the second in making both of these operations simultaneous. Defecation is operated in a batch of open circular, round-bottomed pans, known as defecating pans, of which Fig. 1 is a section. A is the bottom of the pan. B is an outer steam-tight jacket, or false bottom. C Is a steam valve through which steam is admitted, between A and B, in quantities to suit the exigencies of the moment. D is the outlet for condensed water and superfluous steam which is returned to the "return boilers." The small cock, shown in the cut, on the right of the false bottom, is for regulating the egress and ingress of air between the double bottom and also for favoring the com- plete evacuation o f the steam. E] E i s a syphon tube, furnished with necessaryjeocks and stops, through which the clear juice is drawn off after being defecated. In many factories, instead of this tube, E E, an orifice closed by a wide-mouthed cock at the bottom of the pans, and opening into a wide funnel, is preferred. Through this funnel the clear juice is at first run off, and is followed by the scums formed during defecation, each of these products being conveyed to different departments of the works to be further separately treated. These latter pans are easier cleaned than the first, but the syphon pans furnish a larger amount of clear juice. The capacity of defecating pans varies according to the quantity of j uice worked up in twenty-four hours, but seldom exceeds five or six for the largest works. While defecation is proceeding in some of the pans, others are being cleaned or being filled or emptied in regular methodical order and sequence. The defecating pans being placed on a higher floor than that of the press room (so as to be above the head of the filters), the juice has to be raised from the low'er reservoir to the upper edge of the defecating pans, over which it is discharged through special pipes. The old plan of pumping up the juice has been replaced in all modern sugar works by the cleanly, simple, and rapid process of steam pressure applied directly to the upper surface of the juice contained in a closed vessel. This is done in an iron boiler, the liquor being conveyed at regular stated intervals of time from the juice reservoir to this boiler, and from the boiler to the defecating pans. This upright boiler is called a monte-jus (literally, mount juice). As quite a number of monte-jus are used in all beet root sugar factories, during subsequent operations as well as the present one, we will here give a general description of a monte-jus, which will apply to all. A monte-jus must be constructed of strong boiler plate, well riveted, and be sunk into the ground into a cylindrical well-drained brick cistern (the brick work of which must be joined with hydraulic cement, so as to keep out water, and be situated at some little distance from contact with the boiler). The top of the monte-jus alone is allowed to project above the floor of the building. In our Fig. 2, A is the pipe through which the juice is admitted from the reservoir of the presses into the monte-jus ; B is a small cock for ingress and egress of air and evacuation of steam ; C is the pipe for admitting steam, its orifice being bent upward so as to cause the entering steam to strike the inner surface of the boiler head; E is the pipe for conveying the return steam to the boilers; F is the manhole door for cleaning out the montejus; D is the pipe through which the liquid is forced from the monte-jus to the level above, the moment steam is admitted through C, when E and B must be closed. Every indicated pressure of one atmosphere, or 14*7 lbs., will rapidly raise the juice through a hight of 30 feet. Monte-jus are often furnished with a steam gage, safety valve, and a float, indicating the hight of the contained liquid. As soon as a defecating pan has been filled from the monte-jus with raw juice to nine-tenths of its capacity, steam is admitted between the double bottom by opening the valve C (Fig. 1) to its utmost extent. The juice is rapidly heated until it reaches temperature of from 174 to 185 Fah,, a fact which practiced workmen appreciate without a thermometer by merely dipping their fingers into it, and by the aspect of the numerous minute particles of coagulated albumen whiGh are present in it. This temperature is just bearable to the hands without scalding. At this moment, milk of lime, prepared from very pure lime, is poured into the warm juice, and well stirred into it. Steam is allowed to continue entering the space between the double bottom with full force, until a layer of scum of the thickness of a finger has formed on the surface of the juice, when the valve must be closed little by little, but in such a gradual manner that just as ebullition declares itself in the liquid the steam must have been cut off to one-quarter of its original quantity. This last portion of steam is itself to be suddenly suppressed, as soon as ebullition and consequent termination of defecation indicated by a sudden irruption of clear juice on the upper surface of the scums, have manifested themselves. The defecating operator must always be a man of experience, as much is left to his empirical judgment. The signs by whieh a favorably-progressing defecation are ; known, are as follows: 1. The scums must gradually form at the surface of the juice, in large flakes of a greenish-brown color. 2. These flakes must unite into a thick layer in which large crevices form, through which the limpid juice below is discernible. If the scums are of a yellow color and look thin, or if ebullition takes place at too early a period, some unnatural alteration in the juice must have taken place, either through heating or putrefaction consequent, on the thawing of the beet root, or through the action of fermentation brought on by impure water left in the reservoir or in the monte-jus, or lastly, by the use of imperfectly worked sacks. In our next article, we shall give an account of the mode of preparing the milk of lime used in defecation, and the manner of "dosing" it to the juice. We shall also attempt to give a general idea of the rationale of defecation, and proceed to explain the necessity for carbonatation and the mode of effecting it. The estimate and valuation in gold for the defecating department of a factory for working 150,000 lbs. of beet root every twenty-four hours, is as follows: Three copper defecating pans, with cast-iron false bottoms, with all their special fixtures, cocks, valves, etc., same capacity as monte-jus. Cost, $1,320. Copper feed pipe, with three cocks for juice, and iron pipe with three cocks for water for washing out pans. Cost, 100. Total, for a defecating department of a 500-acre factory, $1,420.
This article was originally published with the title "Beet Root Sugar" in Scientific American 20, 17, 261-262 (April 1869)