Ball mill process lead oxidation using

In a patent of 1926, G. Shimadzu described an adaptation of the ball-mill process used for grinding ores, pigments, etc., by using lead balls tumbling against one another in a mill. The friction created sufficient heat to oxidise the outside surface of the lead balls and the obtained oxide layer fell off continuously in the form of dust. An air flow of a definite speed and humidity carries away the oxide dust through inbuilt screens to separate the coarser fractions and return them to the mill. The fine lead oxide particles were collected in storage silos. 

Lead oxide is the main component of the active material for both the positive and negative electrodes. Lead oxide is made by oxidizing lead by using either the Barton pot process or the Ball mill process. 

The oxide exiting either the Barton or ball mill reactor is conveyed by an air stream to separating equipment, ie, settling tank, cyclone, and baghouse, after which it is stored in large hoppers or dmmmed for use in paste mixing. Purity of the lead feed stock is extremely critical because minute quantities of some impurities can either accelerate or slow the oxidation reaction markedly. Detailed discussions of the oxide-making process and product are contained in references 55—57. 

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. 

Particles of lead dioxide in lead monoxide, such as those formed in a ball-mill, can be formed by treating the oxide with ozone before paste mixing [49]. The use of persulfate [50-53] and peroxides [54] to effect the partial conversion of lead oxide in the paste to lead dioxide has also been proposed. A proprietary process for treating the surfaces of unformed plates with ozone gas produced a thin coating of lead dioxide, which enhanced formation [55,56]. Much lower quantities of lead dioxide are needed with this approach than when red lead is added to the plate, and the normal battery paste mix can be used. Dipping or spraying the plate with a persulfate solution has also been adopted to oxidize the surface PbO to conductive Pb02 [57]. 

The dependence of the phase transformation temperature and sequence on the mill type, milling media, time, acceleration is analyzed in this chapter for a few samples of transition aluminas and their mixtures. Mechanical treatment carried out in the high-powerful planetary ball mills developed at the Institute of Solid State Chemistry SB RAS. Since it is known [10] that mechanical activation with and without elimination of heat leads to essentially different processes in the powder under activation, experiments were carried out with the oxides under investigation using mills both with and without aquatic cooling. 

Lead is used to make the active materials as well as the grids. The lead must be highly refined (usually virgin or primary lead) to preclude contamination of the battery. It is described as corroding-grade lead in ASTM specification B29." Lead is oxidized by either of two processes—the Barton pot or the ball mill. In the Barton pot process, a fine stream of molten lead is swept around inside a heated pot-shaped vessel, and oxygen from the air reacts with fine droplets or particles to produce an oxide coating around each droplet. Typical Barton pot oxides contain 15 to 30% free lead, which usually exists as the core of each fine leady oxide spherically shaped particle. Barton pots are available in a variety of sizes up to 1000 kg/h output. 

---