CHLORINATION MACHINERY.—The chlorination barrel used at the Golden Reward Chlorina tion Works. Deadwood. S. D., the methods employed at which represent the best American practice in barrel chlorination, is thus described by Mr. John E. Rothwell in the Engineering and111ining Journal, vol. li, 105, NG: The chlorination barrel used in these works is made to serve at the same time as the washing and leaching vessel, by placing a supporting diaphragm to form the chord of an are of the circle of the barrel. The diaphragm, or filter as it is called, is made up of corrugated plates, and perforated with holes every 4 or 6 in. square. These plates are supported on segments which are bolted to the shell of the barrel ; on top of the corrugated plates is placed the filtering medium, an open-woven asbestos cloth. Over this is placed an open grating, and the whole is held in place by cross-pieces, the ends of which rest under straps bolted to the inside shell; in this way, while the whole is rigidly held in place, it is very easily and quickly removed when the changing of the asbestos cloth becomes necessary. Two valves on each end of the barrel above and below the filter are for the inlet and outlet of the wash-water and solution, respectively. The barrel is charged by first filling the space under the filter with water, which at the same time is allowed to pass through the filtering medium and wash it ; then the required quantity of water is put in above the filter. There are now two methods of charging the pulp and the chemicals (lime chloride and sulphuric acid). In one, the lime is so placed in the ore charge in the hopper over the barrel that it goes in with the ore and is completely buried with it ; the acid can then be added with very little danger of generating any gas before the plate on the charging hole can be put on and securely fastened. The other way, which seems to be still better, is to pour the acid first ,into the water, through which it sinks in a mass to the bottom and does not mix ; the ore is then let in, and the lime added the last. The chances of wasting any gas are much less than in the first method. On the first revolution of the barrel the gas is immediately liberated, and creates considerable pressure. After the chlorination is complete the barrel is stopped. so
that the filter assumes a horizontal position ; the hose is attached to one of the outlet pipes and conducts the solution to the reservoir tank. A hose is also attached to the inlet pipe and water is pumped in under pressure, and the leaching commences. The air in the top part of the barrel is compressed and forms an elastic cushion, which gives the wash-water perfect freedom to circulate evenly over the whole surface of the charge, and wash every portion of it thoroughly and with the smallest quantity of water possible. The length of time required to do the leaching varies with the leaching quality of the ore treated—charges having been leached in 40 min. with a pressure of from 30 lbs. to 40 lbs. per sq. in. With higher pressures the time can 1w materially shortened. In order to facilitate the leaching of charges carrying an excess of slimes, a valve placed in the head of the barrel, on a level with the surface of the pulp, is opened just after the barrel is stopped, and the dust and slime which remain in suspension are run off into an outside washing filter-press, where it can be treated separately.
The tailings are discharged into a ear which will hold the whole charge of ore and water, and then run out ; or, if water is abundant, they are discharged into a sluice and washed away.
The amount of water required for leaching is about 120 gals. per ton inure than the quantity used in the barrel for chlorination, which is about 100 gals. per ton. In order to get a concentrated solution for after-treatment, to reduce the amount of solution to be treated, and to save water, a tank is placed above the barrel, and when the richest of the solution and wash-water has run into the reservoir tank the discharge hose is connected with the pipe leading to the upper tank, and the washing is finished into it. The solution collected in this way is used in the next following charge in the barrel ; the quantity of solution to be precipitated is thus reduced to about 120 gals. per ton of ore treated. One man and a helper are able to take care of three barrels—that is, to look after the charging, leaching, and dis charging. If the tailings are sluiced out, they can also attend to it ; but where they have to be trammed out, one more man is necessary.