The caving in labour secured by the employment of triple-effect apparatus may be conveniently illuatrated by some actual figures obtained on two aimilar estatea, with syrup a.nd sugar of identical quality and value, and under equally able management. On the eatate using open batteriea and a single vacuum-pan, the labour (negro) was aa follows :-17 hands at centrifugals, 25 at batteriea, 4 at vacuum-pan and engine, 8 collecting fuel, 4 at ateam-boiler : total, 58,working 18 hours a day = 1044 bours of labour. The second used a juice-heater, defecating- and subsiding-tanks, a triple effect, and a vacuum-pay, and employed the following labour :-12 handa at centrifugala, 3 at triple-effect, 2 at vacuum-pan, 4 collecting fuel, 6 at ateam-boiler, 3 engineers, 4 at defecatora, 2 at scum-tanks, 2 at ayrup-tanks, 2 at molassea-tanks ; total, 40, working 13 hours a day = 520 hours of labour. Each factory turned out 13 tons of lat and 2nd argue per diem.
Figs. 1375-1378 show an arrangement by Manlove, Alliott, Fryer, & Co. In each pan, ia a vacuum above the boiling liquor—slight in the lst, better in the 2nd, and very complete in the 3rd. This ia attained by a vacuum-pump, driven direct by a ateam-engine, and aimilar to the vacuum pump of an ordinary vacuum-pan. The flow of the liquor through the three pans is continuous, no atop requiring to be made for the discharge. The vapour rising from the boiling liquor in the let passes through a " save-all" (which catchea any priming juice) into the ateam-drum of the 2nd, whence it is removed as condense-water after giving up its latent heat to boil the liquor around it. Similarly, the vapour from the liquor thus set boiling in the 2nd passea through a save-all into the steam-drum of the 3rd, whero in turn it condenses itself, parting with its latent heat to the liquor now in the 3rd stage of concentration. The vapour rising in the 3rd pan, being at so slight a tension aa to part with its latent beat only at a temperature too low for it to be further utilized, passes through a save-all to a oondenser, whence it rushes as condensc-water into the pump. Thus ahnost all the heat supplied to boil the liquor and evaporate its water is used again to repeat the operations to a further extent in the 2nd and 3rd pans, Hence the economy of fuel, as compared with ordinary steam evaporating-pans. The temperature of the liquor in the 1st pan is below that of the same liquor boiling in the open air ; it is reduced for the denser liquor in the 2nd pan, and still further for the mast concentrated liquor in the 3rd pan, in consequence of the progressive counpletoness of the vacuum.
Rillieux's Triple Apparatus.—Norbert Rillieux's improvements in triple-action apparatue, with the object of attaining a maximum useful effect, aro as follows : —The recipient for disobarge-steam (A, Fig. 1379) is provided with an equilibrium-valve C, which regulates tho maximum quantity of steam that can bo need. The first recipient being the steam-generator of the entire apparatus, and heated by the discharge-steam of all the engines, is also connected with tho disehargc-water from the coils of the boiling-pan D through the elaeek-valve a and pipes b. By this means, the small excess of steam that escapes with the water, assiste heating the first pan, while the combined condense-water from the coils and pan passes off through another pipe d e into a reservoir g fel. the feed-pump to the generators.
To effect boiling with double action, considerable preesnre is required in the first pan,—i-1 atmos., and even more, according to the size of the coils. The vacuum is very small in the aeon(' pan. The pressure is regulated by introducing into the feed-vcssel for the triple-action a sufficient quantity of direot steam, so that it does not interfere with the action of the apparatus. To maintain normal pressure in the flrst pan, special apparatus ie provided. If the boiling-pan is heated by direct steam at high pressure, the discharge is conveyed to the 1st evaporating-pan ; if eteam from the expansion-chamber is used, or escape-steam from the engines, the discharge from the boiling-pan is conveyed to the 2nd evaporating-pan; if steam from the let evaporating-pan is used for boiling, the dieeharge passes to the 3rd evaporating-pan, and thence to the condenser. In triple-action apparatus, the lst evaporating-pan is provided with two small auxiliary pans, one to evaporate the syrups that have been subjected to osmosis, the other for evapnrating the saline liquors, both being connected to the same condensing-column. Improvements are also made in the pumps for drawing off the condense-water from the 2nd and 3rd evaporating-pans. To obtain maximum effect from tbe apparatus, it is necessary to maintain a considerable vacuum in the last pan. The condensation is effected by bringing the steam into contact with very extended surfaces, over which water flowe in thin films, thus obtaining a very complete contact of the steam with the water. The steam from the safety-chamber is, as usual, subjected to a water-jet.