Читать книгу Lead Smelting and Refining, With Some Notes on Lead Mining онлайн

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Drop charge 7 a.m. Begin firing down 12 a.m. Begin tapping 1 p.m. Rake out slag 2 p.m. Begin tapping 2.30 p.m. Drop charge 3 p.m. Begin firing down 8 p.m. Begin tapping 9 p.m. Rake out slag 10 p.m. Begin tapping 10.30 p.m. Drop charge 11.00 p.m. Begin firing down 4 a.m. Begin tapping 5 a.m. Rake out slag 6 a.m. Begin tapping 6.30 a.m.

The hearths were composed of about 8 in. of gray slag beaten down solidly on a basin of brick, which rested on a filling of clay, rammed solid. The hearth was patched if necessary after the drawing of each charge.

The system of smelting was analogous to that which was practiced in Wales rather than to the Silesian, the charges being worked off quickly, and with the aim of making a high extraction of lead directly and a gray slag of comparatively low content in lead. The average furnace charge was 3500 lb. At the beginning of the reaction period about 85 to 100 lb. of crushed fluorspar was thrown into the furnace and mixed well with the charge. The furnace doors were then closed tightly and the temperature raised, the grate having previously been cleaned. At the first tapping about 1200 lb. of lead would be obtained. A small quantity of chips and bark was thrown into the lead in the kettle, which was then poled for a few minutes, skimmed, and ladled into molds, the pigs weighing 80 lb. The skimmings and dross were put back into the furnace. The pig lead was sold as “ordinary soft Missouri.” The gray slag was raked out of the furnace, at the end of the operation, into a barrow, by which it was wheeled to a pile outside of the building. Shipments of the slag were made to other smelters from time to time, 95 per cent. of its lead content being paid for when its assay was over 40 per cent., and 90 per cent. when lower.