Active carbon filtering explained
– by Albert de Boer – 07/05/21
Sometimes conditions are so extreme that even the best high-efficiency filters are not up to the job. Think, for instance, about extraction operations on offshore platforms or dredgers where gasses released during the process can be dangerous for crew health.
However, not all gases are toxic – as sometimes we are talking about the kinds of strong smells that come out of a galley. We have an ideal solution for that kind of situation in the form of active carbon.
Imagine a square plate with a surface area of 500 m².
How many toxic particles do you think could stick to its surface?
Then consider that one gram of active carbon has the equivalent filtering surface of 500 m² or even more.
How does active carbon work?
Active carbon is more or less the same as the charcoal used in barbecues, but it is only activated for filtering after it has been given a special treatment. Then, charcoal or carbon has a natural affinity to absorb or capture organic pollutants. The treatment is done by superheating it with steam or some other means and with that, cleansed of gases and impurities.
This process forms little pores and pockets. The inside of an activated piece of carbon is like a complex cavernous system on the micro scale, with immense surface areas in which to absorb and trap toxic particles. Depending on its quality, carbon can have an internal surface area ranging from 500 to 2000 m²/g. That’s the equivalent of a football pitch compressed into the size of a teaspoon.
The carbon atoms attract and hold chemical particles from vapour, air or liquid streams, cleansing them of unwanted chemicals and odours.
Activated carbon is often used in HVAC installations for air filtering within galleys as it greatly neutralises the odours released from cooking. Carbon filters are available in different forms, ranging from bag filters to plate filters and cylinder boxes.
Although extremely effective, activated carbon has its limits. Once the carbon is saturated, it must be disposed of or regenerated for reuse. How long it takes for the filter to be saturated depends on the quality and size of the filter and the amount of pollution. Depending on how often it is used the filter will last from a couple of weeks to several months.
H2S filtering systems
In extreme conditions like offshore platforms, various quantities of toxic gases can be released from within the earth’s crust over a short period of time. Special H2S filtering systems have been developed to protect the crew from poisonous gas sulphide. These ingenious installations make use of overpressure and different filtering stages of which active carbon is one of them. A more detailed description can be found in the H2S filtration system brochure which you can download here.
More extreme filtering solutions
Global dredging and salvaging operations are a speciality which can become even more complex when faced with relics from the two world wars. Bombs and shells are often found during dredging activities. Some contain lethal toxic gases from which the crew needs to be protected and we also have a suitable filter solution for these extreme conditions.
Curious about the best option for your project? Contact one of our engineers to explore the many possibilities.