Barton pot process

It has been reported that silver decreases the rate of oxidation of lead, particularly in the Barton-pot process [25], by up to 10%. In the active materials, silver increases oxygen evolution (at the positive plate) more than it does to hydrogen evolution (at the negative plate). The promotion of gassing by silver, however, does not appear to be as serious a problem as was once thought, at least for materials with silver contents up to 0.01 wt.% [25]. 

The influence of some of the Barton pot process parameters on the structure and properties of the obtained leady oxide can be summarised as follows ... 

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. 

The specific surface of leady oxide is determined by both particle size and shape. The leady oxide powder produced by the Barton pot process consists of spherical particles. So, in order to... 

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. 

Table 5.7 Typical properties and composition of the effluent gas stream from lead oxide ball mill and Barton pot processes [ 1 ].

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 Barton pot process (also called the Barton-like process) is a process that melts lead ingots and feeds them into a vessel or pot. The molten lead is rapidly stirred and atomized into very small droplets via a rotating paddle in proximity to the bottom of the vessel. The droplets of molten lead are then oxidized by oxygen in the air to produce an oxide coating around the droplet. Figure 7.7 shows a flowchart for the Barton pot process. 

The lead oxidation process is exothermic and the generated heat is essential for sustaining a continuous reaction as more lead is introduced. The process temperature is critical for determining the degree of oxidation and crystal morphology of the lead oxide. The Barton pot process typically produces a product containing lead oxide with 15% to 30% free lead, which exists as the core of the lead oxide spherically shaped particles. Figure 7.8 shows a Barton pot. 

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. 

Both the methods (Barton pot and ball-mill) produced partially oxidised lead oxide containing between 20% and 40% free lead. Hence, this oxide was called leady oxide . The production time of this oxide was reduced substantially, which gave a strong impetus to the development of the lead—acid battery industry after 1926. Nowadays, these two processes are still the dominating methods for leady oxide production. 

After the above brief description of the two methods of leady oxide production the question arises logically as to which of the two processes is better. Table 5.1 compares the characteristics of the leady oxides produced by the Barton pot and ball mill processes [17]. 

Latest Advances in the Development of Barton Pot and ball mill Leady Oxide Processes... 

Lead Oxide Characteristics of the Products of the Barton Pot and Ball Mill Processes... 

Table 7.1 lists the lead oxide characteristics produced by the Barton pot and Ball mill processes. 

Another process, the Barton process, is based on molten lead. The core of such a device is the "Barton reactor", a heated pot that is partly filled with molten lead. It is continuously refilled by a fine stream of molten lead. Fine droplets of lead are produced by a fast rotating paddle that is partly immersed under the surface of the molten lead within the "Barton reactor". The surface of each droplet is transformed by oxidation into a shell of PbO by an airstream that simultaneously carries away the oxidized particles if they are small enough otherwise, they fall back into the melt and the process is repeated. Thus the airstream acts as a classifier for particle size. 

In 1898, George Barton patented a new process where molten lead was rapidly stirred and atomised into small droplets, which were then carried away and oxidised by a humidified air stream drawn through die pot. The resulting oxide was passed through a series of cyclone classifiers where the larger particles were separated and returned back to the reaction pot for further processing, while the fine powder was collected in silos (drums or hoppers). 

Audran and colleagues described two syntheses of furanosesqui-terpene natural products employing similar synthetic pathways, culminating in the use of the Barton-McCombie deoxygenation as a key step. The ester unit in bicyclic lactones 65 and 66 is used to set stereochemistry of the C-2 center. After further elaboration, the ester stereocontrol element is then reductively cleaved and cyanated to yield the diols 67 and 68, from 65 and 66, respectively. Then, in a one-pot, two-step process, activation and double deoxygenation was performed to yield reduced compounds 69 and 70, which are the intermediates in the synthesis of (-i-)-ricciocarpin A (71) and (+)-ancistrofuran (72), respectively. 

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