Apparatus for reclaiming lead and other metals

A reactor for reclaiming lead and other metals from scrap batteries which includes two reaction chambers with the upper end of one chamber having a scrap feeding mechanism and at least one burner to melt lead and other metals and ignite organic materials. The chambers are interconnected at their low points for gravity flow of molten metal into a sump. The other reaction chamber is connected with an exhaust system and provided with baffles to retain gases for a predetermined time. The sump includes a tap for slag and a siphon discharge for molten lead. Also, air or oxygen may be introduced into the reaction chambers and/or the sump.

FIELD OF THE INVENTION 
This invention relates to the recovery of metals from articles containing 
metals in combination with combustible materials, but more particularly to 
a method for the recovery of lead and other valuable metals from discarded 
lead acid storage batteries. 
DESCRIPTION OF THE PRIOR ART 
Lead acid storage batteries are generally composed of plates or electrodes 
in which the electrochemically active paste of lead compounds is supported 
by grids of lead or lead alloy metal. Anodes and cathodes are insulated 
from each other by means of non-metallic separators and the structure is 
immersed in a sulphuric acid electrolyte contained in an outer case of 
plastic or hard rubber. Also contained in the cases are current collectors 
in the form of lead alloy conductors, interconnecting groups of anodes and 
groups of cathodes, respectively. Discarded batteries are generally 
considered valuable only for their content of lead and alloy metals, but 
it has become possible also to recover some plastic values from batteries 
contained in such casings. 
In order to recover the metal values only or to recover both metal and 
plastic values, it has hitherto been necessary to separate the two types 
of material from each other. The separation can be effected by manual 
breaking and sorting or by mechanized separation processes such as 
sink-float or wind separation as described for instance in U.S. Pat. No. 
4,118,219 and several other patents. 
Following separation, the plastic fraction must be carefully rinsed to 
remove all lead containing material while the lead containing fraction or 
fractions can be treated hydrometallurgically and electrolytically to 
recover the metal. Such procedures are described in U.S. Pat. Nos. 
3,883,348, 4,107,007, 4,118,219 and 4,229,271. More commonly the lead 
bearing fractions have been treated by pyrometallurgical processes in 
reverberatory or blast furnaces followed by thermometallurgical refining 
to recover the metals in usable form. The furnaces themselves are well 
known in the art, but several improvements have been patented as 
exemplified by U.S. Pat. Nos. 4,102,676 and 4,115,109. 
Whether smelting or hydrometallurgical routes are followed in the recovery 
of the metals, it has hitherto been necessary to separate the organic 
materials wholly or in part from the metal bearing fractions. It would be 
highly desirable to bypass the mechanical separation, because it makes it 
necessary either to deposit lead containing waste materials, or to clean 
such materials very carefully for depositing or for reuse, and hence 
causes handling and treating large amounts of waste water contaminated 
with lead and other heavy metals. In addition, the separation process, 
whether manual or mechanical, involves a very real work hazard for its 
operators. Although not materially different from the hazards of other 
lead industry work, this hazard would be completely eliminated if the 
separation step could be bypassed. 
U.S. Pat. No. 2,826,490 represents an attempt to bypass the separation step 
by teaching a battery reclaiming method in which old drained batteries are 
treated in a special furnace that utilizes the heat of combustion from the 
organic materials, notably the battery cases, to melt the metallic lead 
parts in the batteries. However, the temperature and furnace conditions 
are such that the non-metallic lead compounds such as oxides and sulphate 
that are present in very considerable quantity in discarded batteries, 
become thoroughly dried and appear as a very fine, powdery dross or ash 
after the process. This is not desirable from the point of view of 
hygiene. Operation of the process further requires the batteries to be fed 
one by one to the furnace preferably in an upside down position, making 
the process less amenable to mass production. 
In copending U.S. patent application, Ser. No. 195,435, there is disclosed 
a method of smelting whole, drained batteries in a blast furnace without 
any previous step of separation other than draining the acid. The method 
uses a very wide blast furnace combined with a large afterburner and 
several other features to deal with the combustion of organic material, 
while at the same time performing a complete smelting and reduction of the 
lead and lead compounds present in the batteries. Due to the nature of the 
blast furnace the process must be operated continuously on a large scale, 
and furthermore the heat of combustion of the battery cases can only be 
partially utilized so that the process has a comparatively high overall 
energy consumption. 
SUMMARY OF THE INVENTION 
An object of the present invention is to smelt whole, drained batteries 
with maximum utilization of the heat of combustion of the battery cases, 
in a process that can be operated on both small and large scale, while at 
the same time overcoming the aforementioned difficulties in the prior art. 
According to the invention, a special reactor is used, into which drained 
batteries are fed continuously or intermittently, and where such a 
temperature is maintained that the volatile organic materials in the 
battery cases immediately are gasified and ignited. During a retention 
time in the reactor of not less than 1.5 seconds the gaseous fraction 
undergoes complete combustion, delivering most of their heat of combustion 
to the reactor walls and to the solid and liquid charge material contained 
therein. The hot gas leaving the reactor basically consists of carbon 
dioxide, water vapor and excess air or nitrogen, but it also contains lead 
fumes and entrained dust. The gas must be purified by conventional means 
and the collected dust recycled in the process. 
As the organic materials evaporate and burn, the lead compounds contained 
as paste and sludge in the batteries are reduced and smelted to form 
molten lead. At the same time the metallic lead or lead alloy present as 
grids etc. melts and mixes with the lead reduced from compounds. The 
bottom of the reactor can either be shaped as a sump or well to receive 
the molten metals, or it can be connected through a metal outlet to a 
forehearth receiving the molten metal. By controlling the atmosphere in 
the lowest part of the reactor or in the forehearth, and by blowing air, 
oxygen, or oxygen-enriched air onto the surface of the molten metal bath, 
continuous softening of the lead can be obtained by preferential oxidation 
of the antimony present as an alloy constituent. Together with some lead 
oxide the antimony oxide forms a liquid antimony-rich slag that also 
dissolves such inorganic and non-metallic impurities that may have been 
present in the original batteries. The liquid slag can be tapped 
intermittently for later recovery of its metal contents in conventional 
metallurgical furnaces. 
The softened lead is tapped from the bottom of the reactor or forehearth, 
either intermittently or continuously via a siphon arrangement. In 
contrast with the blast furnace the reactor of this invention does not 
need to be constantly filled with charge material, fuel and fluxes, and 
the process can be operated in short or long periods or campaigns as 
required. 
In one embodiment of the invention the reactor consists of two 
interconnected chambers, both lined with suitable refractory material to 
withstand the temperatures involved. The first chamber is horizontal or 
inclined at an angle of not more than 45.degree.. Batteries are fed into 
this chamber via an airlock in the upper part which is also provided with 
oil or gas burners to preheat the reactor and to ignite organic materials 
in the feed. The lower part of the chamber forms a sump or well, that 
contains the molten lead and can be provided with a siphon tap system for 
lead. The lower part is also provided with means for blowing air or oxygen 
onto the molten metal bath. 
The second chamber extends upwards from the lower part of the first chamber 
and is in direct connection therewith. The interior, refractory lined 
walls of the second chamber may be provided with baffles that introduce a 
turbulent gas flow to assist mixing and complete combustion of the gases. 
The far end of the second chamber is connected to a conventional gas 
purification plant through which the combustion gases are exhausted and 
emitted to the atmosphere. 
These together with other objects and advantages which will become 
subsequently apparent reside in the details of construction and operation 
as more fully hereinafter described and claimed, reference being had to 
the accompanying drawings forming a part hereof, wherein like numerals 
refer to like parts throughout.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring in more detail to the drawings the reactor in FIG. 1 comprises 
two reaction chambers 10, 12 that are interconnected in the lower part of 
the reactor. The upper part of chamber 10 is connected to an airlock 
feeding mechanism 14 and the upper part of chamber 12 to the exhaust flue 
16. The reactor as a whole is lined with suitable refractory material 18 
to withstand the temperatures and contact with the gases, feed stock 
material, molten metal and slag. The upper part of chamber 10 is provided 
with one or several burners 20, 22 directed towards the feed stock 24 that 
is fed into the reactor via airlock 14. The interior wall of chamber 12 
may be provided with several baffles 26 made from suitable refractory 
material. As the organic material in the incoming feed stock 24 is ignited 
by burners 20, 22 or by already burning materials in the reactor, the 
lead-containing materials are heated and reduced to form molten lead 28 
that flows down to the bottom of chamber 10, forming a sump or well of 
molten lead 30. The atmosphere in the lowest part 32 of chamber 10 can be 
controlled by blowing gases such as oxygen or oxygen-enriched air through 
tuyeres or nozzles 34 onto the surface of the metal sump 30. Molten lead 
is finally tapped through siphon 36 into a suitable receptacle 38. 
Referring to FIG. 2, tuyeres 34 can also be arranged in the sides of the 
reactors just above the surface of the molten material, and a tap-hole 40 
allows slag to be tapped intermittently into a suitable receptacle 42. 
Referring to FIG. 3, only the lower part of chambers 10' and 12' is shown 
in this illustration with their refractory linings 18'. In this reactor 
the molten lead and slag 28' flows into a forehearth 44 in which tuyeres 
34' can be arranged in the roof or in the side walls. The molten lead 
forms a sump or well of molten lead 30' and is tapped from the bottom via 
a siphon 36' into a suitable receptacle 38'. The forehearth is equipped 
with an additional burner 46 for preheating, and as only illustrated in 
FIG. 4, with a taphole 48 through which slag can be tapped into a 
receptacle 50. 
The foregoing is considered as illustrative only of the principles of the 
invention. Further, since numerous modifications and changes will readily 
occur to those skilled in the art, it is not desired to limit the 
invention to the exact construction and operation shown and described, and 
accordingly, all suitable modifications and equivalents may be resorted 
to, falling within the scope of the invention.