Leady oxide manufacture

Leady oxide manufacture. Pure lead ingots are subjected to simultaneous grinding and surface oxidation (ball-mill method) or are melted and oxidized in humidified air (Barton pot method). A 60—80% oxidized lead powder (leady oxide) is obtained with a corresponding particle size distribution. 

Especially important for proper operation of the battery are the impurities contained in the metal used for leady oxide manufacture. Lead for the battery industry is derived from ores mined in different parts of the world (primary lead) or is obtained by recycling of used up batteries that have reached their end of fife (secondary lead). The recycling process is very often performed at the battery manufacturers facilities. Purity standards have been adopted for the lead to be used for leady oxide production. These standards specify different maximum allowable amounts of impurities for flooded and valve-regulated lead-acid battery applications. Table 5.2 presents typical purity specifications for lead for making leady oxide for flooded batteries. 

Leady oxides with fiat particles are generally preferred because of their higher surface area as compared to spherical particles. Thus, many leady oxide manufacturers subject the Barton leady oxide to additional grinding in hammer mills. 

Leady oxide manufacture is potentially very hazardous. It is therefore vital to take adequate measures to minimise, or even eliminate altogether, possible lead dust emissions out to the working environment and thus exposure of the personnel which would cause health problems. This is achieved by the use of a closed (isolated) leady oxide production equipment and transport pipes from the storage silos to the paste mixing unit. Special attention should be paid to file manufacture of tubular battery plates. Until recently, tubular plates were filled with a dry mixture of leady oxide and red lead powders. 

Globe Union, Balox leady oxide manufacturing equipment, 1980. 

Over 95% of failed lead—acid batteries are recycled in these pools, yielding secondary lead which is re-used for the manufacture of new lead—acid batteries. The secondary lead is purified to a degree, allowing its utilization in the production of leady oxide and lead alloys. A certain amount of primary lead extracted from lead ores is also added to the lead pool and used in the manufacture of leady oxide. Thanks to the high percentage of recycled secondary lead and the simple technology of manufacture, the lead—acid battery is the cheapest chemical power source available. 

As a rule, national battery standards stipulate only Pb purity grade of 99.99% without specifying the type and amount of allowable impurities. The specific infiuence of additives to and impurities in lead alloys has been in the focus of attention of many researchers [6—12]. Table 4.3 summarises tbe maximum allowable impurity levels for both primary and secondary lead for battery use [10]. Secondary lead comes from recycling batteries after purification. Lead of the purity grade presented in Table 4.3 can be used for the manufacture of leady oxide and lead alloys for both positive and negative grids. 

In the production practice, interrelated variation of the different process parameters is applied to obtain the desired leady oxide powder quality. When the leady oxide powder is too coarse to he used directly in battery manufacture, it is subjected to further grinding in a mill. 

About 75% of the total leady oxide production is realised by the Barton pot method. To bring the Barton pot process into operation at the desired reaction temperatures requires some 30 min each day. The required power for oxide manufacture is approximately 65 kW per ton of leady oxide. 

This characteristic gives useful information about the quality, and more precisely the reactivity of the leady oxide used for the manufacture of battery plates. Water absorption is determined by adding water, under constant stirring, to a sample of 100 g of leady oxide, until a paste of a given consistency is obtained. The quantity of absorbed liquid serves as a measure of the water absorption of the oxide. The typical value of H2O absorption is between 7 and 13.7 mL... 

After its manufacture, leady oxide is stored in silos, but it should be used soon for battery manufacture, because its composition changes and some of its properties may deteriorate if it is... 

The obtained a-PbO particles are of median diameter of 0.530 pm [26]. Karami and collaborators [27] conducted the chemical reactions in the presence of ultrasonic waves (sono-chemical method) with the aim to reduce the size of the resultant particles. Under these conditions, a-PbO particles of 20—40 nm particle size are obtained. The thus synthesised PbO powder is used for the manufacture of positive plates for small laboratory test cells. Commercial negative plates are used as counter-electrodes. The test cells are set to cycling along with analogous cells assembled with commercial plates prepared with ball mill leady oxide. Figure 5.16 presents the obtained cycling test results for the two types of cells. 

There are literature data reporting of the praetiee of some battery manufacturers to introduce these additives into the paste through the leady oxide, hy using lead powders containing certain amounts of these hinders [31,32], Thus for example, the maximum allowable content of Bi in the lead for LO production is up to 0.05%. 

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