CA1108410A

CA1108410A - Method for processing storage-battery lead scrap

Info

Publication number: CA1108410A
Application number: CA305,099A
Authority: CA
Inventors: Anatoly P. Sychev; Vladimir I. Maslov; Vladimir G. Kabachek; Igor M. Cherednik; Georgy V. Kim; Galina D. Sidorova; Valentin F. Larin; Ivan G. Vikharev; Raul S. Akhmetov; Vyacheslav P. Kuur; Georgy L. Moiseev
Original assignee: VSESOJUZNY NAUCHNO ISSLEDOVATELSKY GORNO- METALLURGICHESKY INSTITUT TSVETNYKH METALLOV
Current assignee: VSESOJUZNY NAUCHNO ISSLEDOVATELSKY GORNO- METALLURGICHESKY INSTITUT TSVETNYKH METALLOV
Priority date: 1978-06-08
Filing date: 1978-06-09
Publication date: 1981-09-08
Also published as: DE2825266A1; JPS5931188B2; FR2432052B1; ATA415878A; US4211557A; FR2432052A1; AT355650B; JPS559302A; DE2825266C2

Abstract

Abstract of the Disclosure According to the method of the invention, the storage-battery lead scrap is first subjected to crushing, with large chlorine-containing lead metallic parts and organic materials being separated therefrom. The remainder of the scrap is ground and then smelted in oxidizing atmosphere at a temperature of from 1300 to 1500 until an oxidizing melt is obtained where-upon the lead oxide contained therein is reduced to metallic lead.

Description

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BACKG~OUND OF TIIE INVENTION
;' ; 1. Field of the application The present invention relates to the production of secondary lead, and more particularly, to a method of processing scrap storage batteries formerly used in automobiles.
The invention finds most utility in the pyrometa-.
llurgical practice of lead smelting.

2. Description of the prior art ..
It is common practice to separate used storage batteries 10 (after two or three years of service life) into parts which ; con~ain large-size lumps of metallic lead, such as brldge-poles, gridplates and contact pintles, into the parts containing sulphate-oxide active mass of electrodes; into the cases formed of organic materials, such as ebonite, pitch and polyethylene and into chlorine-containing organic substances. The separation of storage batteries is carried out either manually or by re-sorting to sowing and grinding operations. After the chlorine-containing organic substances are separated, the parts of battery scrap containing lead or its compounds are subjected to smelting.
The above described method is ineffective and labour-consuming, since during dry separation of scrap the cases of such batteries undergo sowing, which can be either a manual or a mechanized operation, whereupon the contents are removed, dried the polyvinyl-chlorlde separators being disengaged by air separation, while antimonial lead and the active mass of electrodes are recovered from the residual mass.
FRG Pat. No. 1,533,129 describes a wet method of processing battery scrap which comprises the steps of crushing said scrap and its subsequent screening on two vibrating screens as it is concurrently sprayed with water.
The first of two screens is provided with a net formed with apertures of 60 to 80 mm in size, the second screen having .

a net with apertures of 3 to 5 mm in size. The top product fed . . .
to the first screen are separators from elastic polyvinyl-chloride, not easily crushed in crushing machines hy reason of their elasticity. After several additional operations the re-sidual lead is collected from these separators which are then discarded to waste.
T'ne undersize of the first screen, freed from the bulk mass of separators, is basically the sulphate-oxide part of the active mass of electrodes, crushed metallic lead and the cases formed of organic substances. The undersize ln question is fed to the second screen with the size of net apertures thereof ranging from 3 to 5 mm, where it is classified into two size fractions. Small-size fractions (active mass of electrodes and, partiall~t, lead and organic substances) are recovered as the finished product, whereas large-size fractions are delivered to a wheel separator into a heavy magnetic suspension where it is classified according to specific gravity into light fraction (fragments of cases) and heavy fraction ~metallic lead). There-after, both products are washed out on two screens from the . . .
residual suspension and are then fed to the end-produck bins; the suspension being passed to the magnetic separator ~or regenera-- tion.
Tihe above-described method, however, is relatively expensive and difficult to be carried into effect.
For example, the cases formed of organic substances are discarded to waste, since they tend to burn when placed into the melt of a melting apparatus, giving off carbon black and tar matter; causing the exhaust of gas from the melting apparatus, complicating the operation of dustcatchers and polluting the atmosphere with noxious gases. The weight of cases is from 20 to 25 percent by weight of the battery scrap.
It should be observed that up to 3 percent of lead is . .

lost with the discarded batteries. The material of the separators, containing organic substances and chlorine, constitu-tes only 2 percent of the total weight of the battery scrap.
- The material in question is discarded to waste because chlorine tends to form lead chlorides during smelting. The recovery of lead from these chlorides presents great technological difficulties. Moreover, the presence of chlorlne brings about vigorous corrosion of gas- and dust-collecting systems. It is common practice to carry out the pyrometallurgical processing of separated battery scrap in shaft furnaces jointly with sin-ter obtained from crudes, or else said scrap can be used as an ; additive to the charge of ore fed thereto at the stage of sintering accompanied by the reduction smelting of the sinter in the shaft furnace.
There is also known preliminary sintering of battery scrap followed by subsequent smelting thereof in the shaft furnace.
However, the method of treating battery scrap in shaft furnaces invariably leads to substantial loss in lead, as well as to an ap~r~ciable consumption of co~e.
Polish Pat. No. 54, 183 teaches a method of processing battery scrap, which is in a way advantageous over the methods described herein above. According to this method, the operating process is effected in the presence of a reducing agent and soda a,il (Na2CO3). The reaction proceeds as follows:
PbSo~ + 2C = Pbs + 2CO2 PbS + Na2CO3 + CO = Pb + Na2S + 2CO2 Since lead sulphate is the hardest part of the battery scrap to yield to treatment, it is therefore this part that dictates the operating technique to be applied.
The process is carried out in drum-type furnaces or electric furnaces at a temperature ranging from 900 to 1100C.

liowever, the method of the patent referred to above requires considerable consumption of a reducing agent, such as coal or coke, an appreciable input of power (fuel or electric power) needed for setting up a working temperature, as well as the consumption of comparatively large amount of scarce soda ash (Na;~C03)-Another serious disadvantage of the above-described method lies in a low degree of decomposition of lead sulphate, whicll does not exceed 28 percent.
The principal consumption of lead (about 40 per cent) is as the metal and peroxide in storage batteries used mainly for the automobile industry. In view of the fact that the service life of storage batteries is not more than two or three years, the amount of secondary lead in need of processing increases with every year. Hence the necessity arises for an economically profitable and effective method of processing storage battery lead scrap, with a view of making the most of its constituent parts.
` SUMMAR~- OF TE~: INVENTION
2~ The principal object of the invention is to provide a method for treating storage-battery lead scrap, which will permit initial material to be effectively treated and the yield of -the finished product to be raised as compared to the known method used for similar purposes.
Another important object of the invention is to reduce the consumption of expensive fluxing materials ~ilized in the process of txeatment of the initial material.
Still another no less important object of the invention is to reduce the consumption of power used in the course of treatment of battery scrap.
Yet another object of the invention is to improve working and health conditions for service personnel by preventing - . : .

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pollution of the environment while carrying out the method.
: These and other objects and features of the invention are accompllshed by the provision of a method for processing storage-battery lead scrap, comprising the steps of crushing said scrap, separating large-size metallic lead parts and chlorine containing organic substances from the sulphate-oxide part of said scrap containing lead compounds, and ~rom the storage-battery cases formed of organic substances, subsequent smelting and reducing the lead compounds to metallic lead, and also subjecting to smelting large-size lead metallic parts, wherein according to the invention, prior to smelting, said sulphate-oxide part oE the scrap and the storage-battery cases undergo grinding to be thereafter jointly smelted in an oxidizing atmosphere at a temperature of 1300 to 1500Cuntil an oxidizing melt is obtained whereupon lead oxide is reduced to metallic lead.
The crushing of scrap makes it possible to carry out further mechanized separation thereof into parts.
The separation of the lead metallic parts ma~es it possible to avoid lead losses in the process of heating the remainder of th2 scrap, and to preserve its high-quality composition as to the content of antimony therein.
The grinding of the sulphate-oxide part of the storage-battery scrap and of the battery cases formed of organic materials free from chlorine permits the rate of smelting of the first part and burning of the second part to be stepped up.
This enhances the efficiency of the process and creates the possibility for effecting flash smelting, makes it possible to intensify the process of heating and subsequent decomposition of the sulphate-oxide part of the storage-battery scrap~
The above-indicated range of temperatures at which the process of smelting proceeds permits the intensive and effectiv~

. ~ 6 transition of lead sulphates into lead oxide. The presence of an oxidizing atmosphere allows for efficient burning of materials formed of organic substances, for example, tne storage-battery cases. Lead oxide contained in the resultant oxidizing melt can be easily reduced to metallic lead. In addition, the melt and slag formed in the process of smelting can be used for melting large-si~e metallic lead parts of the battery scrap.
The scrap material is preferably ground prior to smelting to a size of minus 10 mm. This will enable a rapid rate of heating a charge, vigorous burnlng of the parts from organic substances, as well as intensive decomposition and smelting of the sulphate-oxide part of the battery scrap. The finely crushed part of the battery scrap is preferably subjected to flash smelting.
This will permit heat exchange and mass exchange to be intensified in the process of smelting.
The temperature of the smelting process is preferably maintained within a requisite range by burning the crushed cases of scrap batteries from organic substances, thereby reducing consum~tion of fuel used in the process of smeltingv As a result, the consumption of fuel or electric power required to enable efficient smelting is substantially decreased.
The oxidizing atmosphere necessary for the process of smelting is provlded by preferable utilization of oxygen and/or air. This will intensify the process of burning of the battery cases formed of organic substances, whereby the process of - decomposition of lead sulphate will be stepped up and the amount of effluent gases will be reduced.
It is advantageous that large-size metallic lead parts separated after the crushing operation be melted in the oxidizing melt resultant from the smelting of the finely crushed part of the storage-battery scrap. This will allow the smelting o metallic lead to be effected in the oxidizing melt formed in the process of smelting of the finely crushed portion of the battery scrap.
The invention will be further descri~ed with reference to illustrative Examples and Test Results.
Scrap batteries are initially crushed to facilitate the separation of large-size lead metallic parts, such as contact pintles, bridge-poles and gridplates, as well as materials (separators) containing organic substances with chlorine. The remainder sulphate-oxide part of the scrap containing lead compounds is ground jointly wi~h the battery cases formed of organic substances free from chlorine to a size of minus 10 mm.
Next, the ground battery scrap is subjected to smelting run at ; a temperature of 1300 to 1500C in an oxidizing atmosphere until an oxidizing melt is obtained which contains lead oxide. Since the crushed scrap material contains not less than 10 per cent by - weight of combustible materials, such as chlorine-free organic substances, their burning in an oxidizing atmosphere is accom-panied by the liberation of heat used for the smelting of sulphate-oxide compounds of lead. ~ir or oxygen are normally used to create oxidizing atmosphere, though a mixture thereof is likewise suitable for the purpose. In theprocess of smelting lead sulphate is decomposed, the reaction proceediny as follows:
PbSO4 ~ PbO + SO3. The decomposition of lead sulphate is effected at a rapid rate and practically completely (more than 90 per cent~. Lead oxides together with undecomposed residual lead sulphate and other constituents of the battery scrap, such as silicate cotton, form at a given temperatur~ a fluid melt which contains lead oxide. Next, lead oxide is reduced to metallic lead, for example, under the effect of carbon.
The large-size lead metallic parts separated after the crushing of scrap batteries can be melted separately in the oxidizing melt resultant from the smelting of the crushed .~. ~

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portion of scrap. By grinding the parts of the battery scrap, it becomes possible to conduct flash smelting thereof.
; The requisite tempera-ture for smelting the sulphate-oxide portion of the scrap is achieved by burning the finely - crushed battery cases formed of organic substances. Such utilization of the battery cases allows autogeneous smeltiny to be carried out, thereby substantially reducing tlle consu~ption of fuel~ such as carbon-containing dust, natural gas or liquid fuel. Combustion gases contain gaseous oxides which present no .
difficulty during clèaning of technological gases.
Example 1 The storage-battery scrap was used, containing 72.3 wt.
~ of lead, 6.2 wt. % of sulphate sulphur, 10 wt. % of the storage battery cases, admixtures being the balance. -Upon separation from the crushed battery scrap of the riI;econtaining organic substances and after disengaginglarge-size lead metallic parts therefrom, the sulphate-oxide portion of said scrap and battery cases were ground to a size of minus 10 mm to enable joint flash smelting thereof. The ~{~/r ~
smelting operation was thereafter carried out in ~he-~e~ under ~<
laboratory conditions for a period of 4 min. and at a temperature ; of 1~00C. After reducing lead oxide to metallic lead by the use of carbon, the recovery of said metallic lead was as high as 92 per cent (without taking into account sublimates obtained during smelting).
- Example 2 In accordance with the method of the invention the storage-battery scrap was crushed, the injurious constituents were removed therefrom, and large-size lead metallic parts were separated out. The remainder wasground to a size of minus 5mm.
The scrap in question contained, in per cent by weight: lead.

66.7; sulphate sulphur, 6.3; battery cases formed of organic g ~

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substances, 15.
-', The smelting was carried out in the flame zone wi-th ~, simultaneous supply of oxygen and at a temperature of 1320C
without consuming fuel usually employed in the process of - smelting, since the smelting temperature was maintained within a preset range by burning crushed battery cases formed of organic substances free from chlorine. Technical-grade oxygen including 92% 2~ used to set up an oxidizing atmosphere, was supplied at the flow rate of 260 Nm /hr, and at the production rate of 1000 kg/hr depending upon the charge fed. The preseparated large-size lead metallic parts underwent smelting in the oxidi~ing melt resultant from the melting of the finely crushed portion,of - the battery scrap. The reduction of lead oxide to metallic lead , was effected by using coke-breeze charged on the surface of bath '-' in an electric furnace at the rate of the 30 kg per hour.
Upon completion of the lead oxide reduction to metallic lead, the loss of lead carried out with waste slag was only ~~' 0.18 per cent by weight of the total quantity of lead contained in the processed scrap.
' 20 Example 3 , The storage-battery scrap to be processed contained 66.5 wt. % lead, 6.2 wt. % sulphate sulphur, and battery cases 15 wt. %.
After being ground to a size of minus 2 mm, tlle scrap material underwent smelting in the flame zone as the air-oxygen mixture was concurrently fed to set up a reducing at-mosphere. In the course of smelting an oxidizing melt was formed which contained lead oxide and having slag on its surface.
Large-size metallic lead parts separated from the battery scrap prior to its grinding were fed to the oxidizing melt. To enable reduction of lead oxide to metallic lead, co]~e was fed onto the surface of the melt. The reduction was conducted in the electro-~p 10 -thermic furnace. The production rate, depending upon the quantity of charge fed, was 1000 kg per hour, the consumption of coke used in the electric furnace to produce a reducing reaction was 30 kg per hour, and the flow rate of technical-grade oxygen (con-taining 92% 2) was 260 Nm /Hr.
The smelting was thus carried out in an autogeneous manner, i.e. without the use of fuel, with the temperature in the working space of the furnace being 1360C.
After lead oxide was reduced to metallic lead, the loss of lead discarded with waste slag was only 0.15 per cent by weight of the total quantity of lead contained in the processed scrap.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for reprocessing lead storage-battery scrap comprising: crushing said scrap; separating large-size metallic lead parts from said crushed scrap; separating chlorine-containing organic substances from said crushed scrap; grinding a sulphate-oxide portion of said scrap, containing lead compounds, and battery cases formed of organic substances free from chlorine; subjecting the finely ground part of the scrap to smelting in an oxidizing atmosphere at a temperature of 1300 to 1500°C until an oxidizing melt having a slag layer is obtained which contains lead oxide; reducing said lead oxide to metallic lead; and melting said large-size metallic lead parts separated after crushing separately or under the layer of slag in the oxidizing melt from the smelting of the finely ground portion of the storage battery scrap.

2. A method as claimed in claim 1, wherein the sulphate-oxide portion of the scrap and the battery cases are ground to a size of minus 10 mm before smelting.

3. A method as claimed in claim 1 wherein the storage battery scrap is subjected after grinding to flash smelting.

g. A method as claimed in claim 1 wherein the smelting temperature is maintained within a preset range by utilizing the heat from the burning of finely crushed battery cases formed of organic substances, thereby reducing the consumption of fuel required for the smelting process.

5. A method as claimed in claim 1,2 or 3 wherein the oxidizing atmosphere required for smelting is created by supplying oxygen and air.

6. A method as claimed in claim 1, 2 or 3 wherein said large-size lead metallic parts separated after crushing are melted under the layer of slag in the oxidizing melt from the smelting of the finely crushed portion of the storage-battery scrap.