Iron ore slurry filtering solutions

Iron ore is ground to finer particle sizes through different grinding systems. Large grinding mills using grinding ball media are one of the most common and particularly in pelletizing plants where finer particle size are required for the pelletizing process. Those large mills operate either with water mixed in with the ore – called wet grinding – or without water - dry grinding.

A fair amount of water is used in the wet grinding process.  The material exiting the mills is in form of slurry with water content typically ranging from 30 to 50 %.  The surplus of water should be removed prior to the balling process through dewatering equipment given that pelletizing requires a much lower moisture content (from 8 to 10 % for most plants).

We find few de-watering technologies in the industry, but slurry filtering through vacuum disc filters is still the main equipment seen in pelletizing operations and particularly in Canada, USA, Mexico, Brazil, Chile, Russia, Ukraine, etc.


How does a vacuum disc filter works? 



Metal 7’s vacuum disc filter

Metal 7 manufactures rotating disc filtration systems for mineral processing. They are produced according to the client’s specific needs in order to obtain a filter cake that meets the highest standards in production.

The filters were designed in close collaboration with end users to reduce maintenance and maximise equipment utility. They make it possible to achieve high production standards without having to increase the vacuum’s capacity or the plant’s needs in energy.

Different filter configurations are offered depending on the number of discs and their diameter. The most common filter in the iron ore industry includes 12 discs, 9 feet in diameter, therefore a 1290.20 sq. ft. filtration space (120 m, or 120 sectors of 1 m).

The advantages of Metal 7’s vacuum disc filters


Optional features are available including

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In pelletizing plants that operate with wet grinding to reduce the particle size of the ore prior to the balling/pelletizing process, it is necessary to dewater the slurry exiting the grinding mills to lower the moisture content in the ore. The pelletizing of iron ore normally requires from 8% to 10 % moisture depending on the ore characteristics.

Vacuum disc filters are the main equipment used in the pelletizing industry for the dewatering of the slurry.

However, they consume a lot of , primarily related to the operation of the large vacuum pumps required for the operation of the disc filter. Furthermore, they are also considered to be maintenance intensive equipment. No surprises there, since they are in constant rotation and they are exposed to a very abrasive material, the iron ore.

The challenge in the design of a filter is related with its availability (no unplanned shutdowns and low maintenance), its higher productivity and its energy efficiency. It also has to provide the end user with the lowest moisture content in line with the pelletizing requirement and consistency in this moisture level.

Lots of suppliers of vacuum disc filters are active on the market.  But very few could combine reasonable tonnage per hour, energy efficiency, adequate and consistent moisture and low maintenance.  Even fewer could maintain their performance after even few weeks of operation.  


Metal 7 designed its own vacuum disc filter with:

•    Improved air flow with more tonnage out of the filter for same filtering area.  
•    Increased sealing of the assembly.  Any vacuum or snap blow air loss has a negative impact on the productivity of the filter;

•    Better lubrication of the rotating parts;

•    More robust and resistant parts = longer life and higher filter availability;

•    Significantly easier to maintain compared with the other filters on the market;

•    Almost no variation in the moisture content with time and at different regime of operation.  


Two main options are offered:

A-    The vacuum disc filter with its basic package;
B-    The vacuum disc filter with the high performance package.


With both packages the customer gets the standard Metal 7’ vacuum disc filter providing higher tonnage thanks to the optimal air flow and the increased filtering area.

However, with the high performance package, the vacuum disc filter is delivered with extra features improving further the sealing (sealing of the lubricated area and of the vacuum/snap blow air components).  It also comes with parts manufactured with special materials to extend the life of the components, their performance in service over a longer period of time and the availability of the filter.


Furthermore, optional features are available including:

-    An automatic system for the cleaning of the filter cake chutes without having to stop the filter;
-    Innovative design of protective guards around the filter;
-    Automatic lubrication system;
-    Instrumentation (slurry level, etc.);
-    Etc.


The filters are available in different sizes and capacity according to the requirements of the customer (different options in capacity, filtering area, disc diameter, number of disc, etc. are possible).


-    Higher tonnage for same filtering surface: We have seen improvements in production of up to 40 %, by converting to Metal 7’s filters, without increases in the vacuum requirement.

-    Lower OPEX:  

a-    Lower maintenance: Components last longer thanks to the strategic use of better material.  Better air flow contributes in lowering wear by erosion in critical elements of the filter, like in the filtrate tube;

b-    Lower power consumption: Metal 7 larger filters provide higher tonnage without requiring more vacuum. The ratio of energy per ton produced with the filter is better.

-    Reliable equipment: Filtering equipment availability is increased and even more so with the high performance package offered as an option;

-    Reasonable CAPEX investment:  The filter design is versatile and design is adapted to the client’s need.  Replacing existing filters by Metal 7’s is not a challenge.

-    Consistency in the filter cake moisture content: Negligible variation of the moisture content. For instance, in changing to Metal 7’s filters, one of its customers saw a variation of only 0.1 % in the moisture content in the whole range of RPM they operate. This variation was of 1.0 % (10 times greater) with the former well-known filters they previously used.

Vacuum disc filter family

Two packages are offered with the vacuum disc filters :

The main filter features are the same with both packages.  The filters come with the...

Metal 7, a partnership that lasts

Metal 7 is one of Canada's biggest players in the metallic and ceramic coating field. Thanks to its leading expertise, the company stands out from its competitors by proposing extremely sophisticated, high-performance solutions. This competitive edge allows the company to thrive on the international market. The products manufactured in its workshops are used in nearly fifty plants in 20 countries, on all five continents. Metal 7 exports over 70% of its annual production outside Canada.

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