1. Field of the Invention
This invention relates to the recovery of metallic lead from scrap lead-acid batteries such as those which are discarded from automobiles. More particularly, the present invention provides for the smelting of unbroken scrap batteries in a blast furnace of such unique design that the separation and recovery of the lead and lead-bearing materials can be accomplished economically and yet meet all pollution requirements for both air and water.
2. Disclosure Statement
The substantial cost of lead and the problems of disposal of waste lead makes recovery of lead from scrap batteries of significant economical importance. Worldwide, millions of tons of scrap batteries are produced annually. Consequently, the lead industry could save hundreds of millions of dollars per annum if a dependable lead recovery process existed.
Hitherto, it has been necessary to remove the battery case which is constructed from rubber, plastic or asphaltic material from the battery by one means or another, before attempting to recover the lead contained within the battery. Typically, such decasing processes included draining the acid from the battery, breaking the remaining unit as a whole, and then hand sorting the casing material from the lead containing materials. Breaking batteries by hand is a dangerous job inasmuch as unavoidable splashes of lead sulphate sludge on clothes, hands and face invariably result. The acid which is drained from the battery has been previously emptied into the earth, poured down the drain or stored, which presents unacceptable environmental problems. Mechanized procedures for crushing the batteries and separating the casing materials from the lead-containing materials require heavy equipment, a lengthy operation, and are necessarily very expensive. Furthermore, the methods of removing the casing from the battery produces a toxic lead contaminated case material which, if discarded, poses a substantial health hazard. Processes for recovery of lead from waste batteries are disclosed in U.S. Pat. Nos. 3,393,876 and 4,118,219, issued to M. E. Elmore, which attempt to improve on prior recovery processes involving separating the battery case from the lead-containing battery components. These patents utilize a crushing step and a flotation step for separation of the battery components.
It has been proposed to recover lead from scrap batteries by burning the battery cases and utilizing the heat so released to melt the metallic lead components of the batteries. Previous attempts, however, have proven unsuccessful because the battery cases are made principally of organic materials and their burning results in the production of excessive smoke and a highly polluted atmosphere. In an attempt to solve this problem, U.S. Pat. No. 2,826,490, issued to Newmann, discloses utilizing the excess heat formed by the combustible materials in the battery cases to melt the contained metallic lead and maintain the collected molten lead in a liquid state until conveyed to suitable molds or otherwise disposed of. This patent utilizes a furnace construction adapted to receive discarded and drained storage batteries and provides a combustion chamber with means therein to project turbulent air onto the battery cases as they burn. The batteries are supported on a grate or rail structure through which the melted lead drips onto a collecting pan. U.S. Pat. No. 4,058,396 mentions that prior art processes have employed introducing complete batteries into a furnace and removing the molten lead, while employing an after-burner to burn off volatile organic products from the battery cases and separators. The patentee states that such a process produces hazardous by-products and therefore proposes to recover lead from batteries by contacting comminuted batteries with a molten alkali metal salt.
A need, therefore, exists for recovering lead from scrap batteries in a cost effective manner which minimizes environmental pollution hazards and the formation of toxic waste.