Plates lead oxides

PIa.tes, Plates are the part of the cell that ultimately become the battery electrodes. The plates consist of an electrically conductive grid pasted with a lead oxide—lead sulfate paste which is the precursor to the electrode active materials which participate in the electrochemical charge—discharge reactions. 

Paste Mixing. The active materials for both positive and negative plates are made from the identical base materials. Lead oxide, fibers, water, and a dilute solution of sulfuric acid are combined in an agitated batch mixer or reactor to form a pastelike mixture of lead sulfates, the normal, tribasic, and tetrabasic sulfates, plus PbO, water, and free lead. The positive and negative pastes differ only in additives to the base mixture. Organic expanders, barium sulfate [7727-43-7] BaSO carbon, and occasionally mineral oil are added to the negative paste. Red lead [1314-41 -6] or minium, Pb O, is sometimes added to the positive mix. The paste for both electrodes is characterized by cube weight or density, penetration, and raw plate density. 

The tubular positive plate uses rigid, porous fiber glass tubes covered with a perforated plastic foil as the active material retainer (Fig. 2). Dry lead oxide, PbO, and red lead, Pb O, are typically shaken into the tubes which are threaded over the grid spines. The open end is then sealed by a polyethylene bar. Patents describe a procedure for making a type of tube for the tubular positive plate (90) and a method for filling tubular plates of lead—acid batteries (91). Tubular positive plates are pickled by soaking in a sulfate solution and are then cured. Some proceed directiy to formation and do not requite the curing procedure. 

Lead Oxides Leady litharge containing 25 to 30 percent free lead is required for storage-batteiy plates. It is processed on Raymond Imp mills. They have the ability to produce litharge that has a desired low density of 1.1 to 1.3 ff/cm (18 to 22 g/iu ). A 56-kW (75-hp) unit produces 860 kg/h (1900 Ib/h) of materialhaving this density. 

The cast grids are made into battery anode and cathode plates by the application of a lead oxide paste of 70 percent lead oxide (PbO) and 30 percent metallic lead. Lead ingots are tumbled in a ball mill with airproducing lead oxide and fine lead dust (referred to as leady oxide ). Leady oxide particulates are entrained in the mill exhaust air, which is treated sequentially by a cyclone separator and fabric filter. The used fabric filter bags are shipped to a RCRA-permitled commercially operated ha2ardous waste landfill located in Colorado. The leady oxide production process does not produce wastewater. 

Sulfuric acid is added to the assembled batteries and the plates are formed within the batteries by applying electric voltage. The formation process oxidizes the lead oxide in the positive plates to lead peroxide and reduces the lead oxide in the negative plates to metallic lead. The charging process produces an acid mist that contains small amounts of lead particulate, which is released without emission controls. 

Your facility processes lead oxide as a reactant in the formation process, where the lead oxide in the positive battery plates is oxidized to lead peroxide. 

The production of tubular positive plates is in principle similar to that of pasted plates. A number of manufacturers use the same gray oxide as the basic filling substance. Sometimes the share or red lead or minium (Pb304) is increased above 25 or even to 100wt.%. The latter is more economic when the manufacturer runs his own minium plant then the expense of the chemical oxidation of lead oxide (PbO) to minium (Pb304) may be compensated by reduced formation cost. Furthermore, curing is not required, because of the high oxidation state, and the battery starts with full capacity when formed. 

Different methods are in use for plate filling. The material can be filled as a powder with the aid of vibrators. Other techniques use a slurry of lead oxide or even a paste, as described above [27]. 

The drying of negative plates is not possible without precautions, because of the tendency to spontaneous oxidation. This oxidation reaction is much ac-celerated by water, and the active material of a moist negative electrode is spon-taneously converted into lead oxide when exposed to air. When, on the other hand, the charged plate is dry, a thin layer of oxide covers the surface of the active material, and prevents... 

The hrst working lead cell, manufactured in 1859 by a French scientist, Gaston Plante, consisted of two lead plates separated by a strip of cloth, coiled, and inserted into a jar with sulfuric acid. A surface layer of lead dioxide was produced by electrochemical reactions in the first charge cycle. Later developments led to electrodes made by pasting a mass of lead oxides and sulfuric oxide into grids of lead-antimony alloy. 

Curing is the process of exposing plates pasted positive and negative to a regime of (a) controlled time (minimum 32h), (b) temperature (30-35°C), and (c) relative humidity (>90%). This process converts the free lead into lead oxide, using oxygen from the surrounding air. The plates are allowed to cure for a minimum of 32 h. Care is also taken to ensure that the maximum temperature of the plate does not exceed 60°C. The cured plates are then parted. 

Procedure Spread 25 grams of lead monoxide in a thin layer on an iron or aluminum plate 2-4 mm. thick. Either use the variety of lead oxide which has not been fused and is known under the name of massicot, or use lead carbonate, which on being heated yields a very pure and finely divided lead monoxide. Heat the lead oxide over a ring burner so adjusted that the flames do not quite touch the metal plate. The plate must be kept just below a perceptible red heat. Continue the heating for 6 hours or more and turn over the powder frequently with an iron spatula. When the change is complete, the product is dark brown when hot, a bright scarlet-red when partly cooled, and a somewhat less brilliant red when entirely cold. 

Each galvanic cell in a lead-acid battery has two electrodes—one made of a lead(lV) oxide (Pb02) plate and the other of spongy lead metal, as Figure 17.17 shows. In each cell, lead metal is oxidized as lead(lV) oxide is reduced. The lead metal is oxidized to Pb ions as it releases two electrons at the anode. The Pb ions in lead oxide gain two electrons, forming Pb ions at the cathode. The Pb ions combine with S04 ions from the dissociated sulfuric acid in the electrolyte solution to form lead(ll) sulfate at each electrode. Thus, the net reaction that takes place when a lead-acid battery is discharged results in the formation of lead sulfate at both of the electrodes. 

Even the reactions in the lead accumulator can be interpreted with the help of oxidation numbers (see Fig. 8.5). If, in the model of the accumulator, two lead plates are dipped into 20% sulfuric acid solution and electrolyzed by the voltage of about 5 V, one of the lead plates is covered with a dark layer of lead oxide (see E8.10). If the transformer is taken away and one joins both plates with a voltmeter, the voltage of 2 V will be measured (see E8.10). The following equilibrium exists if a pure lead plate and a lead oxide plate are separately dipped into 20% sulfuric acid solution (see Fig. 8.5) ... 

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