No. IX. TECHNOLOGY—PART VI. Concentration of the Juice. The concentration of the juice of the beet root to the point at which the sugar will most readily crystallize, is not effected in a single operation, but in two or three successive ones, separated by nitrations. This concentration or evaporation of the juice of the beet is effected in most modern factories by means of vacuum pans, which, if not identical, are analogous to the one described and illustrated by us in our last article. The theory of the vacuum pan is very simple, being based on the fact that the juice boils at a temperature of about 212 Fall, under the pressure of the atmosphere (15 lbs. to the square inch), and that as this pressure is relieved, so is the boiling point proportionately lowered. By causing a partial vacuum within the pans containing the liquid to be evaporated, the pressure is thus reduced below that of the atmosphere, and it becomes possible to boil the juice at temperatures much below 212 Fah. The heating being done by steam it will be seen that, if, for instance, we make use of waste or exhaust steam from the engine and " returns," which has a temperature of at least 212 Fah., for the boiling of the juice in the first pan with no vacuum at all, this steam will, after it has left this first pan, and although it has lost a portion of its original heat, still retain enough of it, say 190, when it has penetrated into the next pan, as will boil the juice in this second pan 5n a comparatively slight vacuum, and will, after having been used here, still retain heat enough, say 150 Fah., to boil the liquid in the third pan under the influence of a still more perfect vacuum. In our practice the concentration of the beet root juice is nearly always effected by means of exhaust steam, costing nothing, and in a series of pans with respectively increasing vacuums. The time it takes to bring the juice to a certain degree of concentration depends upon the temperature of this juico, on that of the steam used for boiling it, on the extent of heating surface, and on the degree of vacuum within the pans. An increased heating; surface, a more perfect vacuum, or hotter steam accelerates evaporation, and as a corollary, the larger the heating surface and the more perfect the vacuum t)ie less heat will be needed in the steam. The greater the; difference of temperature between that of the juice and that of the steam, the more rapid will be its transmission through the pipes or coils of the apparatus. The pressure in the last pan is reduced, that is, a partial vacuum formed, by injecting cold water into a condenser, which, through a wide pipe, is placed in direct communication with it. As at first, however, when the boiling is begun, the pans and heating spaces aro filled with air which the injection water will not condense, and which it is essential to draw off; this is done by means of an air pump communicating with the condenser. This pump, when subsequently the boiling is in full activity, is used for the purpose of extracting the spent steam and water of condensation, which preserves the vacuum within the pans. The injection cock must necessarily be closed while the pump is drawing the air out of the panst A vacuum must be caused, not only in the upper bodieg of tlie pns but also in the heating tr Bteam space, and the&e ftro &H connected foy this p#pft*a "with %h$ mMmmf % As soon as the juice begins to boil in the first pan, the vapor md steam drive the air out of the body of the first pan into; he second. As soon as the liquid in the body of the second begins to boil, its vapor and steam drive the air from the sec-md into the third body, and when, lastly, the third pan begins; o boil, its contained air, steam, and vapor are carried off directly into the condenser, and drawn out of it by the pump. The injection cock of the condenser must be slightly opened ust at the moment when the juice begins to boil, in pan No. [., or as soon as the steam from No. II. reaches the condenser;; his cock is then gradually opened wider and wider as the uico boils successively in pans Nos. II. and III., and is left wide open during the subsequent regular working of the whole apparatus. The air pump is also allowed to continue loing some amount of work through its cock being partially )pen. Although the three pans are in direct communication with ?ach other, and the condenser, a mean or average degree of vacuum is not produced through the whole apparatus, as night be supposed, but a different state of things exists in ?ach separate body; the most perfect vacuum taking place in; he last pan, while it is null o.r nearly so in the first. The jause of this difference is due to the variable spesd of evapor-ition in the three pans. If the " return" steam used for heating the pans has a :empefature of over 212 Fah. no vacuum is needed in the first body, as it'would cause the ebullition to be too violent md the contained liquid to " prime." If, however, the temperature of this steam be 212, or lower, a partial vacuum has ] :o be produced in the first body by means of a special pump icting on the second body. In practice the liquid in each of the three pans has a differ-3nt density, the thinnest being found in the first body, and ihe most concentrated in the last body. The process of evaporation is continuous through the whole system, the juice lowing constantly into the first pan while it runs out as 'clear sirup" from the last pan, whence it is received in a monte-jus, which forwards it to its further destination. The vacuum causes the flow of liquids from one pan into the other, and also draws it into the monte-jus. For this latter purpose this monte-jus is connected with the condenser by means of a special pipe or simply by uniting it to the vapor chamber of the third pan. The pump attached to the condenser for freeing it of steam and condensed water being at the same time employed to suck air, is for this reason called the " wet air pump." This pump cannot be-too carefully constructed, and must be powerful in its action, so as to preclude all possibility of the rising of the water of condensation into the pans by its accumulation in greater quantities than can be drawn off in a given time. In many newly-erected sugar factories the " wet pump " is now entirely done away with, and the water of condensation disposed of by another appliance. For this purpose the condenser is placed at such a hight that the pipe for the egress of the water of condensation can be made to run down from a hight of from say 36 to 38 feet, while its lower extremity plunges into a small basin of water. This contrivance is connected with the upper portion of the condenser where a " dry air pump" needing very much less power than the " wet air pump," produces a partial vacuum. The water cannot rise in the pipe above the basin to a hight of more than 32 feet without overflowing, as it is balanced at this hight by the weight of the atmosphere; it forms, in fact, a real water barometer in which the water rises only to a hight determined by the extent of the vacuum caused by the injection water in the condenser, but which can never exceed 32 feet. This is a simple, cheap, and efficient contrivance, which we highly commend to both sugar manufacturers and refiners. The triple-effect pans have latterly been, to a considerable extent, replaced by " double-effect" pans, heated by exhaust steam alone, and are found to work satisfactorily. Their heating surface is calculated at one square foot for every 100 Lbs. of beet root worked up per day, so that it would require 1,500 square feet of heating tube surface for the pans of a 150,000 lbs. per diem factory. The modern arrangements for obtaining tight joints and for allowing the cleaning of the pipes, have, thanks to rubber plugs and rings, been much improved on in recent times. Without entering into lengthy details, which could only find their place in a complete treatise on the manufacture of sugar, we cannot possibly describe the many dispositions which have been given to the bodies of vacuum pans (which are often horizontal instead of upright, as we have shown them in Robert's arrangement)' nor can we either indicate the variations in the form and construction of condensers and of their pumps. We advise persons who might wish to establish a beet root sugar factory to have their vacuum pans and necessary apparatus made by only a first-class manufacturer of beet root sugar apparatus, one whose reputation and business depends entirely on his keeping pace with all the most recent improvements. Several such firms in Europe have acquired in this connection a world-wide celebrity, and some of them have agents in this city, from whom all desired information can easily be obtained. As a general rule, in practice, the " return " steam is admitted into the first body of the vacuum pan with a temperature of about 220 Fah., into the second with a temperature of about 172 Fah., and into the third with a temperature of about 154 Fah. The heating surface in square feet needed for the concentration of the liquids in vacuum pans is calculated on the basis of from 15 to 30 lbs* of water evaporated by every square loots Xhe"first" m "dew tops" tm cmtef the p&fiimiitt advantages, the pipes and internal coatings of the heating apparatus must be kept bright, clean, , 1 free from scale. If violent " priming " takes place, whicli I Ft 1 constantly watched for, a small quantity of melted gi ase is run on to the upper surface of the boiling liquid, through small grease cocks, this allays the tendency to foam. Grease must be used as sparingly as possible, as it interferes materially at a later period, with both the action of the bone black in the filters and the " boiling down " of the sirups. The sirups marking 24 to 28 Baume are collected into the monte-jus, and are from thence conveyed to the reservoirs of the filters, and from these through the bone black in the filters, in a manner we sliall describe in our next article. It is then ready to be taken to a second vacuum apparatus, single, double, or triple, where it is further concentrated to a consistency, which is generally indicated by a density of from 40 to 42 of Baume's areometer. The less dense are the concentrated second sirups after boiling down, the larger will be the grain produced from them; and on the contrary, the denser these " second sirups" the smaller and finer will be the size of the grains or crystals of sugar subsequently produced from them. In order to obtain large and even-sized, regular-shaped crystals the boiling in the second vacuum apparatus must be carried on slowly and quietly. The right degree of concentration is practically known to a good sugar boiler by the " thread " test. This consists in taking up between the thumb and fore finger a small quantity of sirup and drawing it out as a thread by spreading the fingers. The length this thread attains before breaking, and the " hook " it makes at its broken ends allow of his judging very accurately when the sirup has reached the desired consistency. From the boiling pans the second sirups are taken to vats, tanks, or "crystallizers," where the sugar is left to deposit itself in a solid form, which afterwards allows of its being freed from the surrounding liquid molasses. The specifications for the evaporating and boiling department of a beet root sugar factory working 150,000 lbs. of beet per day, would be as follows : 1. A triple effect copper vacuum pan. with condenser and all fixtures complete, and. 1,200 feet of heating surface, sufficient for the working of 160,000 lbs. of beets per day. Cost, $4,800. 2. One horizontal wet air pump, with its special 10-horse power engine. Cost, $1,460. 3. One iron vacuum pan, boarded with wood, triple coil pipes, with heating surface of 200 feet and capacity of 250 cubic feet, with cast-iron condenser. Cost, $2,200. 4. One horizontal wet air pump, with its special 6-horse power engine. Cost, $1,040. 5. Two iron coolers, each of a capacity of 750 gallons. Cost, $320. 6. Four reservoirs, each of a capacity of 1,000 gallons, and one montejus of a capacity of 50 cubic feet. Cost, $250. Total cost, in gold, of the concentration and boiling department of a 500-acrebeet root sugar factory. Cost, $10,070. The filtration department of this same establishment would comprise: 1. Seven filters, 15 feet high, double-bottomed, with syphon tubes, copper pipes, juice, and water cocks, etc. Cost, $2,000. .2. An " organ " set of pipes and cocks for distribution of juice, sirup, water, and steam. Cost, $350. 3. A triple gutter above and one single gutter below. Cost, $250, 4. Two feed reservoirs, each of a capacity of 750 gallons, with their cocks* etc, CoBt, $110. 5. Three reservoirs, each of a capacity of 230 gallons. Cost, $200. Total cost of the filtering department, in gold, $2,910. Commercial Value and Purity of Coal Gas. The commercial value and purity of coal gas depend: 1. On its illuminating power. 2. On its freedom, to a certain extent, from ammonia. 3. On its freedom from sulphureted hydrogen. 4. On its freedom, to a certain extent, from sulphur in any form other than sulphureted hydrogen. 5. On its freedom from carbonic acid. Illuminating Power.—It appears from documentary evidence that in the very early days of gas lighting the construction of burners was well considered, and the conditions necessary for the production of the best effect thoroughly understood, but in spite of the reiterated teachings of competent men, burners of erroneous construction have during many years been pro duced in great numbers. Forty-three years ago, Christison and Turner published a statement of their experiments, the conclusions deducible from which the author of this paper has summarized as follows: 1. That up to a certain maximum consumption for each burner, the light increases in. a much greater ratio than the consumption of gas. 2. That for each burner there is a certain size of flame which is most economical—a corollary of the first proposition. 3. That in argand burners the size of the holes and their distance from each other are of the utmost importance The holes should be So near to each other that the flame unites at itsiase. For, gas Sp. gr. 550 to 650, the holes should be l-32d inch diameter and about 12-100ths of an inch apart. For gas of a higher gravity, the holes should be l-50thinch diameter. 4. That the size of the central aperture of an argand exercised an important influence on the amount of light yielded. & Thatth gre&tot amount of light is obtained wtai tlic fi&f&a become* tidwftb. yefiow sMiS Sea* to tine poiht ** 6. That the glass chimney should be proportioned to the size of the burner and the consumption desired. 7. That consumers, generally, cannot burn the gas in such manner as to produce the best effect, on account of the liability of the flames to smoke. These propositions really comprise all that is known respecting the principles which should govern the construction of gas burners. The sixth proposition is impracticable of application. Narrow chimneys are apt to become partly fused and opaque, they are liable to frequent breakage, and flames inclosed in narrow chimneys are apt to smoke on the least disturbance. Among the teachers on the subject of gas burners may be mentioned Clegg, Peckstone, Alex. Wright, Lewis Thompson, Dr. Letheby, and Henry Bannister. Alex. Wright stated that of burners equally suited for the gas, and consuming it at the same rate, the most advantageous is the argand, next the bat-wing, and then the fislitail. That the larger the quantity of gas properly consumed in a given time from a burner, the greater is the light given per cubic foot. That the best result s arisa with a well formed but flagging flame, and the worst with an irregular, wire-drawn flame. Lewis Thompson said in 1851, every burner has (1st) a certain fixed amount of gas which it will consume to advantage; and (2d) gives its maximum effect where the flame is on the point of smoking. That the quantity of light is greatest with the argand, and the intensity with the fish-tail. Poor or common coal gas should issue more gently than rich or cannel coal gas, and from burners with larger holes than those for tlie latter gas. The yellow-tinged flame, the flagging flame, and the gentle current, all mean the same thing—viz., low pressure; and MM. Dumas, Kegnault, Andouin, and Berard, have established as a general law " that the greatest illuminating power is obtained with low pressures, and the maximum light with pressures, equal to *07fHo -12 of an inch head of water." They further state that batwing burners of the same diameter, burning the same quantity of gas, yield more light when the slits are wide —l-36th of an inch gave them the best results. The diameter of the burner should be proportioned to ths desired rate of consumption, but is less important than the width of slit. That single jet burners are very disadvantageous. That a fishtail is not much superior to two single jets, with holes of the same diameter, if the holes be very small. That the fishtail is generally inferior to the batwing. That argand burners, of almost the same appearance, many require" to burn double the quantity of gas to give the same quantity of light, which is dependant upon, 1st, the width of the jet holes or slit; 2d, on the number of holes; 3d, on' the actual and relative dimensions of the apertures by which air gains access to the interior and exterior parts of the flame; 4th, on the hight of the chimney.—Mechanics' Magazine.
This article was originally published with the title "Beet Root Sugar"