The art of producing caustic soda and chlorine gas to satisfy the great diversity of its uses, and its ever increasing consumption in the industrial arts, has demanded the attention of the best talent in the chemical and electrochemical field. Innumerable attempts have been made for producing these products strictly along chemical lines; that process being the most successful where the cost of raw material was the least, or where the by-products could be reclaimed in a manner profitable.
FIG. 1 - Engine Room
America, unhampered by the more obsolete methods followed in Europe, and with its unlimited resources for producing cheap power, was ripe for the introduction of electrochemical methods to enlarge and improve upon the general chemical industry.
FIG. 2 - Switchboard
Therefore, it was not long before this country was industriously pushing to a conclusion the most effective system pertaining to cheapening the cost sufficiently to compete with foreign trade. Consequently, there have been developed several systems for the production of caustic soda and chlorine gas by the electrolysis of sodium chloride.
Naturally, the most successful is the one where the economy of maintenance and operation, in conjunction with high efficiency, has proven beyond the skepticism of the investor the true facts of its merits. Such a process as this is illustrated herewith in a plant installed by the McDonald Electrolytic Co. for the New York & Pennsylvania Co. at their paper mill at Johnsonburg, PA. This plant has been in operation for over one year, and has a daily capacity of 16 tons of bleaching powder and 7 tons of caustic soda.
Figs. 1 and 2 represent the engine room and switchboard. The walls and floors are of tile, and the exposed iron work is coated with white enamel. The generating units are direct-current, compound-wound generators, constructed so that each will operate without sparking at a voltage varying from 180 to 270, and capable of supplying 2,000 amps, to the cell sets arranged in series-multiple.
FIG. 3 - Cell Room on Second Floor
These generators are directly connected to vertical, cross-compound condensing engines, with a rating of 750 hp at 100 pounds steam pressure at the throttle. The exhaust of these engines is conducted to a condenser. The switchboard is so constructed as to operate the individual cell units independently, their regulation being governed by a separate ammeter to each unit. The auxiliary machinery, such as a motor-generator set for lighting 200 16-c.p. incandescent lamps, and a 100-hp. motor for driving the agitators in the bleach liquor tanks, derive their power from the main units.
Figs. 3 and 4 illustrate the cell rooms, Fig. 3 shows the second floor, containing 250 cells and the chlorination towers, to which the chlorine gas is delivered under a slight suction. Fig. 4 shows the third floor, upon which are located 350 cells. All of these cells are connected up in series-multiple of 50, and so connected at the switchboard as to be interchangeable.
FIG. 4 - Cell Room on Third Floor
On the first floor are located the bleach liquor tanks, with a combined capacity of 72,000 gallons of bleach liquor. There are also located at this point the brine mixing and storage tanks. The plant, as a whole, is constructed so as to facilitate its operation with as small an amount of labor as possible. The brine solution is supplied to the cells automatically, and the products resulting from its decomposition are handled without undue expense.
The chlorine gas upon delivery to the chlorination towers is immediately taken up by the milk of lime, and after repeated circulations is brought up to the required per cent of available chlorine, whereupon" it is delivered to its point of consumption by the aid of a system of piping and rotary pumps. The caustic soda leaves the cell at a density of 15° B. and is delivered to an Ordway evaporator, illustrated in Fig. 5, located in an adjoining building.
FIG. 5 - Ordway Evaporator
The evaporator receiving the solution at 15° 5 pounds steam pressure concentrates it to 45° and during this operation the salt is practically eliminated. By the introduction of this evaporator there is furnished the connecting link to a most complete system for producing a finished product from the raw material.
It has been found by the New York & Pennsylvania Co. that the repairs and replacements on the complete plant, have been abnormally low, and I am told that their cells have been in operation over eight months without being disturbed, and, when finally taken apart, the replacement of the anodes was the only requirement. The results produced by this plant have attracted chemists both in this country and abroad, especially as many tests as to its efficiency have substantiated the claims set forth by its makers.
BY J.R Crocker
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