Leady oxide reactivity

A comparison between the reactivity and productivity of the two leady oxide production processes is presented graphically in Figure 5.8. 

Leady oxide consists of lead oxide and free metallic lead. When produced by the ball mill method, the degree of oxidation of 65—75% is achieved, while the Barton process yields leady oxide powder with 70—80 wt% PbO content. When the leady oxide contains more than 30 wt% free lead, the material becomes very reactive. It is readily oxidized in humid air and the heat produced by this exothermic reaction may lead to combustion and damage the production equipment. Hence, effective control of the percent content of imoxidized lead in the leady oxide is very important, both during the production process and during the subsequent handling and storage of the 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... 

Reactivity of ball mill and barton pot leady oxides [21]. 

Most appropriate for determining the specific surface of powder materials of the above types is the adsorption method, or BET process. The average specific surface of leady oxide measured by BET is 0.7—1.4 m g for the Barton type and 2.4—2.8 m g for the ball mill type, respectively. It has been established that the BET surface area depends on the content of p-PbO in the leady oxide [21]. A maximum area is obtained at 15 wt% P-PbO level. It could be expected that the latter leady oxide would have the highest reactivity as well. The percent content of the P-PbO crystal modification can be controlled by varying the temperature of the Barton pot. Process temperature of about 450 °C yields the leady oxide with approximately 15 wt% P-PbO. 

Logarithmic plots of the particle size distribution by diameter for ball mill and Barton pot leady oxides are presented in Fig. 5.12 [22]. The two curves differ significantly, indicating considerably higher percentage of particles with diameters less than 1 pm in the ball mill oxide as compared to the Barton pot oxide. This particle size distribution is responsible for the higher reactivity and the acid absorption of ball mill leady oxide, as well as for its lower apparent density. 

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