FR2501182A1 - PROCESS FOR PREPARING LEAD-CONTAINING OXIDE FOR LEAD-ACID BATTERIES - Google Patents

Abstract

IN THIS PROCESS, MELTED LEAD IS INTRODUCED IN A REACTION CONTAINER, DISPERSIONED IN DROPS OF MELTED LEAD, PARTIALLY OXIDIZED THE LEAD DROPS CONTAINED IN THE REACTION TANK BY CONTACT WITH A CURRENT OF AIR CONTAINING WATER UNDER FORM ATOMIZED AT A PH INCLUDED BETWEEN APPROXIMATELY 8 AND ABOUT 12, THE OXIDIZED LEAD DROPS IS EXTRACTED FROM THE REACTION CONTAINER, IN A CURRENT OF AIR, THEN THE OXIDIZED LEAD DROPS ARE COLLECTED. THUS OBTAINED BY A CONVENIENT PROCESS, AN IMPROVED PRODUCT CONSISTING OF LEAD-CONTAINING OXIDE.

Description

The present invention relates to the manufacture

  lead-containing oxide cation for example for use in preparing lead acid battery-active materials, and more particularly relates to an improved process and product.

  Active ingredients of lead-acid batteries

  acid are prepared, as known, from a mixture of lead and lead oxide in the form of finely divided particles of lead oxide having

  IO a residual core of lead. There are two main processes

  currently used commercially. The first uses a pulper in which blocks of solid plorab are ground by autousure in a drum

  rotating steel. The resulting lead powder is

  It is then oxidized by air, and the powder is then extracted from the drum, either by air or through sieves. The powder is then classified in a general way, and the large particles are recycled to undergo a new grinding, while the particles

  small dimensions are collected for use.

  In the second process, molten lead is introduced into a reaction vessel, for example in a

  Barton tank, and stirred by means of a rotary pallet.

  This turns the molten lead into droplets and exposes

  a large surface area to air entering in order to oxidize

  tion. The powder is discharged from the reaction vessel by a stream of air and then it is classified or further milled. It is generally considered that

  the use of reaction vessels has advantages

  compared to the crushers from the point of view of a

  decrease in investment and operating costs

  per unit of lead oxide produced. Typically,

  the material produced has a different particle shape

  the result of the use of crushers, ie a spherical shape, in opposition to a sheet-like or relatively flat form, and has a slightly higher proportion of lead oxide. However,

  processes that use the reaction vessels

  to be more difficult to control, compared to the crushers, with regard to the possibility of producing

  oxide having a uniform quality.

  Thus, in a reaction vessel type process, the temperature is essentially controlled by

  the rate of introduction of lead into the reaction vessel

  tion. The air flow as well as the passage time in the reaction vessel determine the amount of free lead in the product as well as the average particle size. Despite efforts to obtain a temperature

  satisfactory order, it is sometimes difficult to

  to avoid unwanted "hot spots" in

  localized regions, which may affect

  For example, the homogeneity of the product may lead to an increased proportion of orthorhombic lead oxide. In addition, although longer run times than normal times may reduce to some extent the average particle size of the product,

  may result in a low lead content.

  Typically, it is desired to maintain a lead content

  approximately 18 to 25% by weight to avoid obtaining

  exothermic characteristics which are too weak and which hinder the continuation of the treatment, for example the curing of the pulp of active material using such constituted products

  of oxide containing lead for lead-acid batteries.

  It has been suggested to add water to a reaction vessel to improve the manufacture of the oxide containing duplomb.However, according to the knowledge of

  Applicant, these efforts have been affected by the risks

  explosion and counter-blast. More particular--

  It seems that these difficulties result from the training

  moist oxide which clings to the reaction vessel

  and then falls back into this container, causing an expansion of water vapor or a similar phenomenon which then rejects the oxide containing lead out of the reaction vessel, in the immediate environment. In short,

  According to the Applicant's knowledge, previous efforts

  made to use water injection in lead-containing oxide forming processes have been

  singularly devoid of success.

  In addition, it has been suggested to incorporate various additives into the lead-acid battery active materials to improve various characteristics. Examples of proposed materials are various lead compounds such as Pb (O) 2, PbO.H 2 O and Pb (CO 3) 2. In addition, it has been proposed to add to the batteries various metal sulphates such as sodium or potassium sulphates of different

  ways, to achieve many goals.

  In addition, the request of the United States

  No. 242,010 filed March 9, 1981 in the names of Mao and I5 al. discloses an improved method and apparatus for

  produce oxide containing plonb. Advances are

  by injecting ordered quantities

  water in atomized form in the reaction vessel.

  Thus, the purpose of the invention is to provide a

  more convenient method for producing the oxide containing.

Lead.

  The invention also aims to provide a

  oxide containing lead characterized by a medium

  do relatively small particles ..

  Another object of the invention is to provide an oxy-

  containing a plcab characterized by a relative proportion of

  increased tetragonal lead oxide compared with the

  orthorhombic lead oxide content, this in comparison

  conventional oxy-containing oxides produced in the reaction vessels. The invention also aims to

  to provide an oxide containing ploab characterized by

  relatively high acid absorption properties.

  The invention also provides a process for preparing lead-containing oxide with improved efficiency and, more specifically, a lead-containing oxide process which provides higher production rates than in the processes. conventional

  using reaction vessels.

  Other features and benefits of

  the invention will become apparent during the description which

  to follow, given solely as a non-limitative example

  tative and with reference to the appended drawing, in which the single figure is a schematic view of a setting installation

  of the process according to the invention.

  Although the invention may be variously modified and in the form of various variants, the preferred embodiment will be described in detail below. However, it should be understood that the invention is not intended to be limited to the specific form of implementation that is described. For example,

  although the invention is described in connection with the

  As a reaction vessel, it will be understood that it also applies to the use of other types of reaction vessels used in the reaction vessel.

  oxide production containing lead.

  As noted above, the demand

  above mentioned in the name of Mao et al describes a

  Convenient method for obtaining improved lead-oxide-containing products, wherein controlled quantities of water in atomized form are fed into the reaction vessel. Introducing water in this manner and in such amounts eliminates the risk of explosion and blast while leading to improved products. In accordance with the present invention, the advantages of this method of preparation are preserved while obtaining further important improvements by regulating

  the pH of the added water between about 8 and about 12.

  Referring now to the drawing, there are provided means for introducing molten lead into a reaction vessel. For this purpose, these means comprise a salmon feed device 10 which introduces lead into a crucible 12 equipped with an exhaust vent 14. The molten lead that is produced is

  then transported by means of a pump 16, through

  mediates an inclined channel 18, in a Barton tank 20.

2501 182

  Alternatively, and more typically, the molten lead can be introduced into the Barton tank by gravity using

  air as a displacement agent, as known.

  The Barton tank comprises means for dispersing

  the lead is melted in. droplets, the droplets

  are then partially oxidized by air

  trating. Typically, as shown, the Barton vessel is equipped with a rotary vane 22 driven by a

  motor 24. Ambient air to oxidize drips

  IO lead pellets are sucked into the tank through an inlet duct 26. The resulting product leaves the vessel Barton

by an outlet duct 28.

  The conditions that can be used in Barton vats from the trade can vary widely. On principle, the amount of air drawn into the vessel must be more than sufficient to effect oxidation.

  lead and as a carrier medium for trans-

  carry the oxidised lead droplets in the

  tif of collection or classification that is used. As an example of the parameters, it is possible to introduce in a Barton tank about 725 to 1000 or 1050 kg of molten lead per hour, with an air flow of about 42 to 70 m 3 per minute. According to the present invention, there are provided means for introducing water in atomized form at the same time.

  time that the air entering the tank Barton, in quan-

  specificities and at a pH of about 8 to

  approximately 12. For this purpose, water is provided by a

  this not shown, through a rotameter 30 and a conventional pneumatic spray nozzle 32 which is disposed inside the air intake duct 26. Further details concerning the addition of water are described in the application aforementioned American name Mao et al. The desired pH can be obtained by adding to

  water of sodium or potassium hydroxide, using

  any suitable device, for example a conventional displacement pump (not shown). Of course, the amounts required depend on the pH of the untreated water, which is typically about 5 or 6. It will be understood that although it is preferred to use sodium hydroxide or

  potassium, any other material may be used

  provided that this does not lead to the presence of

  materials which would significantly affect adversely

  the further processing of the oxide containing

  lead, the performance of the resulting batteries.

  It has been found that the addition of water at such a controlled pH improves the production rate per unit weight of lead, compared to conventional processes, by the weight gain, beyond what is achieved by the method described in the aforementioned US application in the name of Mao et al, while retaining the advantages of this method I5 relating to the procedure and the product obtained. Thus, it is expected that the increase in lead-based oxy-lead production per kilogram of lead will lead to

significant savings.

  Typically, the product consisting of oxidizing

  lead is exited through the outlet conduit 28 and is collected by any suitable device. CONMe

  illustrated, this device can, appropriately, include

  a separation chamber 34, a cyclone of precipita-

  36 and a filter bag 38. From each of these

  devices, the product may be transported by

  screw carrier 40 for storage, shipping, etc. The flow of air through the installation can be provided by a fan 42 which sucks ambient air to enter the tank Barton and then do it

  cross the facility, as known.

  The excessively large particles obtained in the collection device, in particular in the chamber of

  separation, where at least half of the product is

  collected, can be recycled to the reaction vessel, if desired. Moreover, if it is desired to further reduce the average particle size of the lead-containing oxide, this can be achieved by means of

  hammer mill or the like, as is often the case

  wind in commercial practice. However, as we

  As will be discussed in more detail below, the plorb-containing oxide products produced by the present invention typically have a mean average particle size.

relatively small.

  As briefly mentioned above, the lead-containing oxide produced in accordance with the invention has characteristics which, in some respects, are very different from those obtained in conventional methods using a reaction vessel. Of course, it will be understood that the particular parameters of the process

  used can significantly alter the characteristics of

  Specific properties of the lead-containing oxide product which is actually obtained. However, in a typical manner, the oxide containing lead obtained according to the invention

  usually has a relative particle size

  lower than that obtained in conventional processes. As an illustrative example, the

  particle size of products made of oxidizing

  The amount of lead obtained in accordance with the present invention can vary from about 1.5 microns to about 17 microns (before any treatment in a hammer mill or the like). Of

  In addition, products made of oxides containing lead

  According to the invention, the present invention tends to have reduced amounts of orthorhombic lead oxide relative to that obtained in the conventional preparation process.

  of oxide containing lead in a Barton tank.

  The lead-containing oxide of the invention also exhibits somewhat less acidic absorption characteristics than conventional products. Although this is speculation, it is possible that at least at some stage in the process the oxide containing

  lead produced using the process of the invention

  low amounts of other compounds, for example about 1/2 to 1% by weight, or even more, of Pb (OH) 2. In fact, the controlled pH is believed to increase the weight gains obtained during the process compared to what is achieved using untreated water (i.e., unadjusted pH). ), probably by increasing the amount of Pb (OH) 2 or other compounds obtained. Whatever the mechanism, it appears that one obtains a

  increased efficiency of the oxide, may be due to the

  increased characteristics of acid absorption.

  The ploEb-containing oxide of the present invention can be used to conventionally prepare active ingredient pastes without the need to change the formulation or processing techniques. Similarly, dough-coated grids intended to constitute both positive and negative electrodes can then be converted into active ingredients by any of the

currently known techniques.

  Moreover, when using the products

  With the lead-containing oxide of the invention to prepare active ingredients for lead-acid batteries, no adverse effects were found. In fact, for a

  certain reason, the use of the invention results in

  a somewhat increased efficiency of the oxide in the sense that the reserve capacity of the batteries using this lead-containing oxide proves to be slightly increased compared to the reserve capacities obtained with active substances made from oxide containing ploeb produced by conventional methods using a container

of reaction.

  The following example is illustrative only

  of the invention and is not intended to limit its scope.

  Example To illustrate the performances obtained thanks to

  In the present invention, the cells of

  sai incorporating active materials made from the oxide containing ploib according to the invention, and these

  cells were compared to an equi-

  active ingredient pellet made from lead-containing oxide obtained by a conventional method using -w

a reaction vessel.

  Two cells using oxide were made

  containing lead obtained by introducing

  water in atomized form in a Barton vessel as generally illustrated in the accompanying drawing, the amount of water being about one and one half percent by weight based on the weight of molten lead fed, the pH being adjusted to 8 by addition of sodium hydroxide. By way of comparison, a cell was made in which the active ingredients were prepared using a similar product consisting of an oxide containing

  of a Barton tank process, except that

  no addition of water was used. Each cell has

  six positive electrodes and seven negative electrodes. Cha-

  I5 that electrode grid is coated with about the same

  amount of active ingredient pulp, and coated grids

  kills are similarly hardened. The cells are then assembled and subjected to the same technique of production. Each cell was then subjected to a charge-discharge regime for thirty-two cycles. In the discharge regime, the discharge current was 20 A, until a breaking voltage of 1.75 V was reached. In the charging regime, a recharge was performed to obtain about 110 to about 115% of capacity in

  amps-hours lost in the discharge regime.

  The table below shows the time in minutes

  which has elapsed before obtaining the voltage of

  pure. Number of Cycles Control Cell Test Cells

1 2 3

1 142 146 144

2,151 153,155

3 160 163 167

4,171 173,175

176 174 179

6 174 179 181

7 179 182 184

8,180 186,188

9 179 182 184

10 179 183 186

11,177 183,185

12 172 177 179

13,171 176,178

14 167 178 180

IO 15 173 180 182

16,167 173,177

17,157 167,169

18,162 167,170

19,159 165,169

I5 20 155 162 167

21 163 170 176

22,159 165,171

23,165 167,174

24,158 162,170

25 153 155 161

26,149 152,159

27,153 159,165

28,149 155,163

29,147 151,159

30 145 149 153

31 160 162 165

32,165 167,172

  As can be seen in this table, the

  performance of the test cells using the

  the lead according to the invention have a homogeneous

  gene performance somewhat improved.

  Thus, as we have seen, the present invention

  provides an improved process for the preparation of

  lead. The product obtained is also characterized by improved properties, for example properties

improved absoption of acid.

Claims (2)

- CLAIMS -   A process for the preparation of lead-containing oxide for use in producing lead-acid battery active materials, characterized in that   molten lead is introduced into a reaction vessel   the molten lead is dispersed in droplets, the lead droplets contained in the   reaction vessel by contact with an air stream containing   water in atomized form at a pH between   about 8 and about 12, the reaction vessel is   in the air stream, lead droplets   oxidized, then collect the oxidized lead droplets.   2. The process of claim 1, wherein   in that the pH is maintained by adding to the water a hydroxide consisting of sodium hydroxide,   Potassium hydroxide or mixtures of these hydroxides.