HIGHLY ENERGY EFFICIENT DEWATERING OF TAILINGS AND CONCENTRATE PRODUCTS DOWN TO 8% W/W MOISTURE

Mechanically, the filter is quite simplistic. It uses a single geardrive and electric motor to rotate the ceramic segments through the slurry basin. Vacuum and capillary forces attract solid particles to the surface of the membrane to form a filter-cake, and, upon further rotation, pull free filtrate from the filter-cake prior to discharge. It operates as a continuous system. This simplifies process and general arrangement diagrams, and minimizes downstream bulk-handling solutions sized for the maximum throughput of the plant.

Slurry Basin and Frame – Built entirely in 304 stainless steel, the slurry basin’s unibody fabrication allows an even and consistent distribution of the filter’s operation load. The basin holds and discharges the slurry when prompted by the unit’s PLC. It measures and controls the volume in the basin through a level sensor linked to the input slurry feed valve. The basin is the main frame of the filter and suspended the drum for rotation.

Drum – Also built entirely in 304 stainless steel, the drum is supported by two bearings on either end. The drum is connected to the vacuum system through distribution valves on either end which determine the point of cake-formation, dehydration, backwash and their ratio. Vacuum lines run down the length of the drum which connect through rubber tubing to each ceramic segment.

Ceramic Segments – Each alumina-ceramic segment is custom manufactured with a special membrane to define the rate of filtration, permeability and pore density and size. These variables are established in a typical testwork campaign, prior to project implementation. Fired in a kiln, the composure of the ceramic allows capillary tubes to form. These are the main route for water to transmit through the membrane. Each segment is installed independently to ensure maximum operating time and minimal maintenance.

Backwash System – On every disc rotation, the ceramic segments undergo a pressurized water backwash. This water, after under-going pre-filtration, enters the drum through the distribution valve, fills the internal cavity of the segments, and saturates the capillary tubes from the inside out. By designing this process correctly, plate permeability and performance can be maintained throughout a process shift of the filter.

Acid/Ultrasound System – On an intermittent basis, the filter undergoes a deep-cleaning cycle that combines a dilute solution of nitric acid and ultrasonic energy. Upon discharge of slurry, the basin is filled with process water. Using the same process of the (water) backwash, an automatically diluted stream of 1% HNO3 (nitric acid) saturates the segments, and dissolves any solid particles that have precipitated out of solution and have blinded the capillary tubes. Ultrasonic energy is transmitted into the basin through external generators and direct at the plate surface by transducers installed between the discs.

Discharge Scrapers – To discharge the filter-cake from the surface of the ceramic segments, the disc travels between two scrapers set at a distance between 0.5 – 1.0 mm. By removing typical “cake-blow” functions present on conventional cloth, drum filters, CECMS has removed another dependency, utility connection and operating cost.

Power Consumption Savings

Ceramic membrane technology requires a much smaller vacuum pump (per m2 of filtration surface area) than conventional cloth membranes. By utilizing pores that are between 0.75 – 3.0 microns, no air can transmit through the membrane, only water. This means that the system can generate a high operating vacuum pressure (-0.95 kPag) with a much smaller rate of flow in measured in m3/h/m2.

The result is up to an 85% reduction in energy consumption compared to conventional cloth disc, drum, and belt filters, and plate and frame pressure filters (both membrane and recessed chamber). In areas where energy costs are an issue, especially at remote projects where power is generated through diesel, this can be of substantial economic value.

High Quality Filtrate Recovery

Ceramic membrane technology allows for highly effective retention of fine and ultrafine solid particles to produce ultra-clear filtrate. In many cases, replacing cloth membranes with ceramic on the same material can produce a 99% reduction in total suspended solids, 99% reduction in turbidity (measured in NTU), and a 20% reduction in total dissolved solids in a filtrate stream. This quality improvement reduces flowsheet complexity through removal of secondary clarification processes, and allows for direct re-use in flotation and leaching circuits to off-set fresh process water consumption.

The Largest Ceramic Filter Available

CECMS manufactures the CX12-204 filter, the largest ceramic filter ever built and installed in North America.

The large filtration surface (204m2) area per unit, allows for:

1. Higher filtration capacity per unit
2. Simplification of process and general arrangement diagrams
3. Smaller equipment footprint, and lower civil/structural costs
4. Economies of scale for larger filtration plants
5. Lower project OpEx (USD$/tonne filtered)
6. Lower project CapEx (USD$/tonne filtered)