Show AN electrical precipitate DRYER by G H of possible interest to operators of cyanide plants may be a description of a precipitate drying pan that was devised at wonder nevada conditions there were such that the use of fuel either wood coal or oil made this operation expensive and as usual it was generally a tedious one the equipment originally furnished was a double muffle oil fired furnace the muffles being of such size that pans 30 inches by 36 inches could be placed therein the difficulty was that if a sufficient heat was carried to dry the product rapidly the iron muffles burned out after some ten or twelve runs and also even at this heat the drying process was unsatisfactorily slow A man had to be in attendance almost constantly to watch the burner and to rabble the precipitate in the pans As a normal cleanup clean up totaled about 2000 pounds of product and the best work that could be done was to dry approximately pounds per shift it can readily be understood that the method was expensive the next plan tried was to remodel the fire box of the furnace to burn wood of which there was a considerable quantity in the way of scrap lying around at the same time the muffles were moved and several coils of pipe placed lengthwise through the furnace the idea being to force a blast of air through these coils and lead the resulting warm air beneath the perforated bottom of a pan 4 inches by 10 inches by 8 inches deep the warm air escaping through the perforations and thence through the precipitate effected the drying about ns rapidly as when the duffes were used with the advantage that less attention was required to fire the furnace and rabble the material in the pan but with the disadvantage that power was required to furnish the blast after a few campaigns it was found that the supply of scrap on the ground was rapidly being depleted and that such accumulation as could be reckoned on from cyanide boxes and packing cases would not meet the demand with cordwood at 12 requiring splitting before using and oil at 11 cents per gallon it became evident that electricity at 1 13 1 3 cents per kilowatt hour could be used to advantage As finally perfected the dryer completely locally made consisted simply of a pan 4 feet by 10 feet by 8 inches deep set on a brick foundation about 12 inches high and grouted so that no heat would escape except through the precipitate in the recess below the pan eight resistance coils were placed to furnish the heat these coils were made from secondhand second hand 1 inch pipe around which was placed a wrapping of asbestos mill board 1 16 inch thick as an insulator and over this was wound with a i 14 inch spacing no 16 steel wire of this latter there was a plentiful supply of scrap left over from winding the th oliver filters the winding was done by placing the covered pipe in the lathe and by keeping a little tension on the wire and using the feed screw of the inthe IE the for spacing a neat job resulted four of these coils connected in series formed a group and all were placed in the recess under the pan each group of four being connected to a volt alternating circuit with a simple 2 pole single throw knife switch to start or stop operations the device was found to work perfectly and fitted into the scheme of operations to a nicety since three days were consumed in cleaning up the zinc boxes it was possible to start melting the morning following the finish of this operation the plan worked as follows the solution and precipitate from two boxes were run into the vacuum bottomed tanks and by morning the solution would be removed and the precipitate dried down to about 15 per cent moisture this partly dried material was transferred to the pan and the current turned on by the time the next batch of material was ready in the tanks the following morning the preceding lot would be dried down to about 4 per cent moisture which was about right to prevent dusting this operation was carried on without any special attention whatever and with a power consumption averaging about 6 cents per hour the drying seemed to be particularly favorable to the later process of melting the precipitate and it was possible to produce a bar of bullion in two hours from a faber du faure furnace and in fact this rate of production was maintained although occasionally a bar of this size was made in one and three quarters hours whereas with the other methods of drying from three to four hours were required the dryer was a pronounced success being simple compact and economical |