Battery Breaking and Separation

Primary breaking is either by hammer mill or by spiked rolls in combination with a knife shredder. Batteries are handled by front end loader into a hopper with apron feeder discharging onto a conveyor and into the primary breaker. Breakage releases the dilute sulfuric add electrolyte and equipment must be constructed of stainless steel and be fully enclosed to contain add spray and fine particulates. If crushing rolls are used the discharged material is wet screened to separate fines and electrolyte, and the coarse material is passed under a magnet to remove any tramp steel and is then processed in the knife shredder. 

The material crushed to around -50 mm is passed over a vibrating screen with a flow of water to wash out fine paste material. The screen underflow passes to a settler where the pastes are settled out and the overflow is recirculated over the screen or discarded to either acid reclaim or to neutralisation and disposal. 

The primary screen oversize consists of grid metal, separator plastics and case plastics. It is fed to a water fiUed tank where the polypropylene case material floats and is collected and washed. The remainder of the material is extracted from the bottom of the tanks by drag or screw conveyor and is passed to a hydrodynamic separator or elutriating column where an upward flow of water separates out plastic material as overflow from metallic lead, which sinks to the base of the column and is extracted by drag or screw conveyor. 

Coarse materials are dewatered and washed on fine mesh screens and stockpiled for further processing. Metallics may simply be melted in a pot or standard lead kettle or can be melted in a short rotary furnace, with some collection of a htharge slag to separate antimony and arsenic and produce a soft lead. Separator plastics are usually disposed of in landfill but polypropylene is thoroughly washed, and extruded as pellets for sale to battery manufacturers for new case production. 

Fig 10.2 - Generalised flow sheet of battery breaking and separation. 

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A number of proprietary battery breaking systems are available, in particular those offered by MA Industries and the CX System from Engitec-Tonolli. The sequence of operations for battery breaking and separation is shown in Figure 10.2. 

Capital costs will be of the order of US 15 million for battery handling, breaking and separation, and US 10 million for the smelting furnace and ancillaries. The total cost of US 25 million represents US 715/t of batteries per annum or US 1315/t of lead per annum. 

The Bergsoe process, in use at Bolidens 40000tpy Landskrona plant since 1976, provides a possible solution to environmental and technical problems related to battery breaking and waste material separation and disposal. In this process, feed preparation and smelting operations are effectively integrated. 

Battery breaking technologies use wet classification to separate the components of cmshed batteries. Before cmshing, the sulfuric acid is drained from the batteries. The sulfuric acid is collected and stored for use at a later stage in the process, or it may be upgraded by a solvent extraction process for reuse in battery acid. 

The first major battery-breaking step is the dismantling or breaking of the battery to gain access to the lead units. There are numerous ways to do this, but the most common approach is via a hammer mill or roller crushers. The fragmented product is fed to a sink/float or hydrodynamic separator where the fractions are sorted. In the basic sink/float cell, the plastic fractions are floated off and removed to the plastics recovery section whilst the lead-bearing portions of metallics and compounds sink to the bottom and are removed via conveyors or other means, for further... 

Separators must have a longtime chemical and mechanical stability in the battery environment. They must be sufficiently elastic so as not to break down in the course of battery assembling and be shockproof. In addition, they must be inexpensive, simple in manufacture, with reproducible properties in large-scale production. An ideal separator must introduce only a minimum resistance to ionic current. The conductance attenuation coefficient varies from 1.1 to 1.6 for simple spacers and from 2 to 8 for porous and ultra porous varieties, reaching 15 only in exceptional cases. Depending on the battery type and function, separators either fill the whole electrode gap or only a part of it. In the latter case electrode surface is in free contact with the free liquid electrolyte, which is sometimes essential for sheet-shaped separators to have several rips in order to ensure a gap between them and the electrodes. 

For high-volume automotive-type batteries, the fabrication process was substantially modified with the introduction of the PE separator and its two unique properties flexibility and weldability. Unlike previous separators, the PE separator could be wound onto a roll and could be completely wrapped around the plate without breaking and cracking. Additionally, the PE separator was weldable unto itself either by sonic, mechanical, or heat welding. These two properties opened up the opportunity for further assembly optimization of which the equipment suppliers soon advanced the technology to meet the need [34]. The assanbly equipment automatically wraps a separator around the bottom of the PE separator and then mechanically seals the sides to create a three-sided pocket around the plate. This pocket minimizes the potential for bottom and side shorts. 

A prismatic battery of larger capacity can be assembled from one or more stacked bicells, whose current collector tabs are welded inside the packaging and thus present only a single metal foil feed-through tab connected to each of the two multi-plate electrodes. To facilitate multi-plate battery assembly and alignment, individual bicells may be Z-folded to prevent electrodes and current collectors from breaking at the fold line they may also be eonneeted by common current collector(s), separator(s), electrode layer(s), ete. 

The most modem battery breaking systems use very sophisticated battery separation circuits, which minimise waste emissions and allow treatment and recovery of a range of components. In the Tonolli CX System (developed by Engitec Impianti SpA), the sequence of operations is as follows ... 

Battery breaking by hammer mill followed by screening, which separates the battery paste and acid from the grid metal and other battery components. 

Modern secondary plants take in whole ULAB batteries and break them in a mechanical hammer-mill. The broken battery pieces are usually gravity separated in a series of water-filled tanks with slow-moving classifier belts to promote the capture of the battery paste. In this way, battery electrolyte is contained within the recycling process, and the acidic component can then be treated in one of the five ways [10] ... 

Subsequently, the cells are subjected to a number of mechanical steps, possibly in the absence of water or oxygen, which would break the cathode compounds apart. Next, techniques that exploit differences in electronic conductivity, density or other properties are used to separate the cell components. It is unclear how the PVDF binder separation from the active materials, which may prove to be a significant barrier for this process, occurs. Cathode materials can be reused in batteries after some relithiation. Careful segregation by chemistry of the process feed will be required to insure product purity and value. 

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