Solid-liquid separation is a critical step in battery recycling, particularly in hydrometallurgical processes where leached metals must be recovered from slurry or solution. The efficiency of this step directly impacts the yield of valuable materials like lithium and cobalt, as well as operational costs. Key technologies for solid-liquid separation in battery recycling include filter presses, centrifuges, and vacuum filters, each with distinct advantages and limitations in performance, cost, and chemical compatibility.
**Filter Presses in Battery Recycling**
Filter presses are widely used in battery recycling due to their high solids capture efficiency and ability to handle large volumes. They operate by applying pressure to a slurry, forcing the liquid (filtrate) through filter cloths while retaining solids (cake) in the chambers.
For lithium and cobalt recovery, filter presses achieve high metal recovery rates, often exceeding 95% for cobalt and 90% for lithium when optimized. The cake moisture content typically ranges between 20% and 30%, depending on the feed material and press configuration. Lower moisture content reduces downstream drying costs but may require higher pressure or longer cycle times.
Filter presses are chemically compatible with acidic and alkaline environments common in battery leaching, though cloth selection is critical. Polypropylene cloths resist sulfuric acid, while PTFE-coated materials are needed for highly corrosive conditions.
CAPEX for filter presses varies with size and automation level. A semi-automated unit may cost $50,000 to $200,000, while fully automated systems exceed $500,000. OPEX is moderate, with energy consumption around 5-10 kWh per ton of slurry and maintenance focused on cloth replacement and hydraulic system upkeep.
**Centrifuges in Battery Recycling**
Centrifuges use rotational force to separate solids from liquids, offering faster processing times than filter presses. Decanter centrifuges are common in battery recycling, capable of continuous operation with high throughput.
Centrifuges achieve comparable metal recovery rates to filter presses, with cobalt recovery at 93-97% and lithium at 88-92%. However, cake moisture content is higher, typically 30-40%, due to the inability to apply high pressure. This increases drying costs but may be offset by lower cycle times.
Chemical compatibility is similar to filter presses, with stainless steel or Hastelloy construction resisting corrosion. However, abrasive particles in battery black mass can accelerate wear, increasing maintenance costs.
CAPEX for decanter centrifuges ranges from $100,000 to $500,000, depending on size and materials. OPEX is higher due to energy consumption (15-25 kWh per ton) and frequent maintenance of rotating parts.
**Performance Comparison**
The choice between filter presses and centrifuges depends on priorities:
- **Metal Recovery**: Both technologies achieve high recovery, but filter presses slightly outperform centrifuges for lithium.
- **Cake Moisture**: Filter presses produce drier cakes, reducing downstream energy use.
- **Throughput**: Centrifuges process slurry faster, favoring high-volume operations.
- **Chemical Compatibility**: Both handle battery recycling conditions, but centrifuges face higher wear from abrasives.
**Vendor Landscape**
Key vendors for filter presses include:
- Andritz: Offers automated systems for battery recycling.
- Evoqua Water Technologies: Provides high-pressure models for metal recovery.
- Micronics Engineered Filtration Group: Specializes in corrosion-resistant designs.
Leading centrifuge suppliers include:
- GEA Group: Supplies decanter centrifuges for battery black mass.
- Alfa Laval: Offers high-speed models for fine particle separation.
- Flottweg: Focuses on energy-efficient designs.
**Economic Considerations**
Filter presses have lower OPEX but higher labor requirements for cake discharge. Centrifuges automate cake removal but consume more energy. For medium-scale recyclers, filter presses often present a better balance of cost and performance. Large-scale facilities may prefer centrifuges for continuous operation despite higher energy costs.
In summary, solid-liquid separation is pivotal in battery recycling, with filter presses and centrifuges serving as the primary technologies. Filter presses excel in moisture reduction and metal recovery, while centrifuges offer speed and automation. The optimal choice depends on scale, material characteristics, and economic priorities.