Given the drawbacks of manual filtration systems, mining companies are prompted to look for alternative filtration techniques. And as an option, automatic self-cleaning filters offer a number of tangible economic advantages.
In the sphere of filtration, automatic self-cleaning filtration presents a sustainable cost saving avenue for mining companies. And this becomes clearer when considering the burdens that stressed mines are currently carrying – skyrocketing operating costs that are squeezing profit margins, against a backdrop of mounting compliance requirements from regulators. Decidedly, these conditions rule out manual filter media which have a myriad of associated challenges – rendering the adoption of alternative filtration mechanism a very plausible proposition.
Problems with manual filtration
Firstly, it has to be acknowledged that treatment systems based on the flow of material through filtration media components, like pressure filters, are critical in various processing applications. In the mining industry, for instance, they are utilised in the separation of solid products from slurry, washing the product to remove impurities, and then drying and discharging the product.
However, there is a downside to them, which can which can hinder the very process of filtration they are supposed to speed up. Kenneth Sutherland and George Chase, authors of ‘Filters and Filtration Handbook’, laments that the major problem is that industry overlooks the costs associated with the maintenance of filters. “When users purchase disposable media filters, they often fail to account for the overall costs such as the initial disposable filter purchase price plus the ongoing cost of tool maintenance and waste disposal.”
In this context, the problems with conventional filters can be categorised in three – loss of productivity due to downtime (loss of productivity), maintenance costs, as well as increased safety risks and emissions.
- Downtime (loss of productivity)
One of the biggest hindrances of disposable filtration media is the tendency to clog quickly, which necessitates frequent cleaning. The process of opening and closing of filter plate in order to remove clogged debris, as well as other related pertinent tasks, reduces the time that the filter is supposed to be running.
- Maintenance costs
Regular maintenance is another area that costs an arm and leg/does come cheap, as it is always an elaborate process. “In the maintenance of a single filter, the operator must remove separate parts, including the cover, compression seals, and seal plates and reassemble all parts with proper alignment to ensure good seals. In addition, there is a housekeeping cost for cleaning any spillage from disposable media,” Sutherland at al adds.
The picture gets all the more complex when one includes buying, maintaining and cleaning workers’ protective clothing for replacing filtration disposable media, as well as the extra time and labour required.
- Increased safety risks and emissions
With disposable media filter there is a high possibility of increased emissions, exposure of workers to potentially toxic chemicals pose safety risks, over and above, the potential cost of rupturing or overflowing.
In view of these drawbacks, mining companies are prompted to look for alternative filtration techniques. As an option, automatic self-cleaning filters offer a number of tangible economic advantages.
During a materials processing cycle, with an integral backwash system, automatic self-cleaning filters are able to remove suspended solids from pressurised liquid streams, and then remove filter cake completely from the screen surface within seconds. Effectively, this removes the need for the physical presence of operators, minimises frequently cleaning and servicing, ultimately, increasing filtration productivity, eliminates worker exposure to safety risks.
How automatic self-filtration system work
Eaton, a global OEM, describes how an automatic self-cleaning filter works, on its webpage. According to the OEM, a unique control system, which can be electrically or pneumatically operated, allows for automatic backwashing of the filter elements. This provides for backwashing cycle to be initiated either by pressure differential, by a timer, an external command or manually. For example, slurries entering at the filter inlet are allowed to pass freely through the tubular filter elements. This consists of inverted wedge that defines the size of suspended particles that should be retained.
When the filter is capacitated, water flow is restricted and the pressure differential between the inlet and outlet increases. By fitting a differential pressure switch, which is fed from both inlet and outlet pressures, the degree of dirt in the filter can be determined.
A micro switch energises the control system which automatically backwashes the filter elements. Backwash is achieved by simultaneously sealing the water inlet to the filter element and opening the top of the element to the backwash outlet. This causes a reversal of flow on the element being backwashed.
Ultimately, the control system causes the backwash operation to be carried out without personnel having to physically operate on the filtering technology.