Fig. 75. Fig. 76. Fig. 77.
Fig. 78. Fig. 79. Fig. 80.
The evaporating cylinders are mounted upon a framework Y, supported upon columns X X, or other suitable supports. The apparatus is shown arranged as quadruple effect, with four connected cylinders, but multiple effect apparatus may be constructed with an increased number of cylinders up to ten or twelve. The heating cylinders B1 B2 B3 B4, containing the evaporating tubes or coils, are preferably arranged in the same horizontal plane, and are provided at the discharge ends of the evaporating coils with separating chambers, A1 A2 A3 A4, of enlarged diameter, and at the supply ends of the coils with the coils with return bend ends, C1 C2 C3 C4. From each separating chamber, A1, A2, valve pipe D1 D2 D3 leads into the shell of the next heating cylinder, as B2, B3, B4, and vapour pipe D4 leads from the last separator A4 to the condenser H, and the vacuum pump H1. A cylindrical catch-all chamber E1, E2, E3, E4, is connected in each vapour pipe between each separator and each successive heating cylinder, as shown in Figs. 66, 67, and 68, and in detail in Fig. 75. Gauge glass and liquid receiving chambers, G1, G2, G3, G4, connect with the bottom of each separating chamber for receiving the liquid as it is separated from the vapour, and a gauge glass g is applied to each of such chambers. Liquid discharge and transfer pipes t, t1, having valves h, h1, as best shown in Figs. 66, 68, and 72, lead respectively from chambers G1, G2, of the first and second effect to the manifold feed pipes leading into the cylinders B3, B4, of the third and fourth effect for the purpose hereafter described. The main steam supply pipe F, having a safety valve f and stop valve f1, Figs. 66, 67, and 68, connects with the heating cylinder B1 of the first effect. The evaporating tubes 1, 2, 3, 4, 5, are expanded or otherwise secured in the tube sheets d and e″ at opposite ends of the cylinders, and are properly connected at the ends in sets of five to form coils. The outer rear return-bend head C1 C2, etc., are provided on their insides with numerous short intersecting partition plates c, forming single and double cells, properly arranged for connecting the evaporating tubes in sets of five, as shown in Figs. 75, 76, 77.
Fig. 81. Fig. 82.
The heads are pierced with holes c′ for connecting the liquid supply pipes M of the manifolds L. The inner return-bend head T in the separating chambers are formed like heads C1 C2, etc., with intersecting partition plates x, and are provided with discharge openings t″ for every fifth tube, as shown in Fig. 69. Tube sheet d is made of considerably larger diameter than cylinders B1 B2, etc., and acts as a vibrating diaphragm, to accommodate the expansion and contraction of the tubes. The separating chambers may be constructed with dash plates b b, two or more in number, having openings g′ g′ alternately upon opposite sides for the passage of vapour, and opening a′ at the bottom for the passage of liquid, as shown in Fig. 80. Here a tube sheet z is provided near the openings of the evaporating tubes, and in such sheet are set numerous small horizontal tubes n, which discharge against a vertical arresting plate b′ set near their open ends. Water and solid matter are impelled against the plate and thereby arrested and caused to flow down to the bottom of the chamber. The liquid feed apparatus consists of a supply tank K, stand-pipe J, feed box K1, double pump I, manifold L, and connecting pipes and valves. The liquid to be evaporated flows from tank K, through pipe k, to stand-pipe J and box K1, the flow being constant and uniform, and of the desired quantity, by means of a valve k′ having a lever handle r′ which is connected by a cord or chain passing over a pulley j with float q in stand-pipe J. The valve opening in pipe k being properly adjusted by means of the float, etc., the liquid is admitted to the stand-pipe J while the column of liquid is automatically maintained at any desired height and pressure regardless of the quantity in the supply tank, by means of the float q, which, as it rises, tends to close valve k′, and as it falls, to open the valve. From the bottom of the stand-pipe J, nozzle j′ discharges a constant and uniform stream of liquid into feed box K1. The suction pipe I″ of pump I extends into box K1, where it terminates in a turned-down nozzle provided with valve i having a lever handle and float z. As a given amount of liquid is constantly running into the box, should the pump run too fast the float lowers, partially closing the valve and lessening the amount of liquid drawn at each stroke of the pump, and preventing air from being drawn in, since the end of the suction pipe is always sealed by the liquid. The liquid is forced by pump I into the manifolds L, from which it flows through the contracted ducts l into the enlarged feed pipes m, as shown in Figs. 73 and 74. Ducts l are of about one-half inch diameter, and the upper and lower sections thereof are connected by a union coupling, one portion of which l′ has a reducer with opening one-quarter inch diameter, more or less, according to the amount of liquid it is desired to feed.
The catch-all chambers E1 E2, etc., Figs. 66, 78, and 79, are provided each at its inlet end e, with tube sheet o extending across its diameter a short distance in front of the opening of vapour pipe D1, and in such sheet are fixed numerous longitudinal tubes p extending to near the opposite head e′, so that vapours carrying watery or solid particles are impelled against the head and arrested. Liquid and solid matter, arrested in the catch-all chambers, flow through pipes v v′ v″ down into the fluid transfer pipe t t′ (Figs. 67, 68, and 72), and thence into the evaporating coils and through pipe v‴ directly to the tail pump W, Fig. 67. By use of the catch-all chambers the most frothy liquids can he readily and economically managed. A liquid transfer pipe s, having a valve h″, leads directly from receiving chamber G3 of the third effect to the separating chamber A4 of the fourth effect, the latent heat being carried off in the vapours drawn by the vacuum pump H1 into the chamber H, and the finished liquid of both effects is drawn off through pipe w by one and the same tail pipe pump W. The water of condensation accumulating in the heating cylinders B1 B2, etc., is transferred from one to the other through connecting pipes u u′ u″ having valves y, shown in Figs. 66, 67, and 68; and finally from cylinder B4 through pipe u‴ directly into condenser H. The specification of the patent, which those interested will do well to consult, next describes the operation of the apparatus.
American System of Soda Recovery.—Mr. Congdon gives an exhaustive description[33] of the method of recovering soda in the United States, from whose interesting paper we extract the following:—The spent liquors are delivered to the Yaryan evaporator from the pans at a density of 6° to 7° B. at 130° F. Here they are concentrated to 34° to 42° at 140° F. At this density they are fed into furnaces of a reverberatory type, where they are burnt to a cherry-red heat; and the ash then raked out. This ash, which averages 50 per cent. of soda, is weighed in iron barrows on suitable scales, and wheeled into the leaching-room for lixiviation. The system of leaching, as it is termed in the States, is conducted as follows:—Iron tanks are used, with suitable piping, that allows pumping from one tank to another, and also to pump from any one of them up to the causticising tanks in the alkali-room. There is also a water-line by which water may be pumped into any of the tanks, and there is a spout used in washing away the black ash sludge. The leaching-tanks have false bottoms of 2in. by 2in. stuff, placed crosswise, over which is a layer of gravel, on which lies a layer of straw, by which the liquor is filtered. The gravel is removed every few days, and the straw with every charge. When one of the tanks is filled with black ash, it is "wet down" with the stored liquor (the strongest of the stored weak liquors), and also with the strongest weak liquors from the tanks, and with weak liquors obtained from these tanks by pumping water upon them and keeping them full. This is all pumped up to the causticising-tank until the strength is reduced to 2° or 1½° B. The remaining liquor is then drained into a tank known as the "clear-liquor" tank, owing to there being no black ash in it. The liquor from the next weakest pan is then pumped upon the pan containing the black ash, and the next weakest liquor pumped upon this. The weaker pans are then in succession pumped upon the stronger, and the water pumped upon these, and thus a very perfect washing is obtained. The sludge left behind is nothing but charcoal, with a slight trace of carbonate of soda. Mr. Congdon illustrates the above system thus. The tanks stand as follows:—