Key points
TL;DR: Fixed vs Mobile Industrial Filtration
Activated carbon filtration is key for purifying air and water emissions. Fixed filters are generally cheaper upfront for lower flow rates but involve costly downtime, safety risks during carbon replacement, and inflexible sizing.
Mobile filters, while less conventional, offer greater safety by allowing off-site emptying, quicker filter exchanges (around 30 minutes), and high adaptability to changing flow rates or stricter emission limits.
Mobile units support modular setups and can be combined in series for improved performance. Companies like DESOTEC provide full-service mobile filtration solutions that reduce investment costs and promote sustainable carbon reactivation.
Activated carbon filtration is one of the best available technologies (BAT) for purifying both air and water emissions in Industrial Filtration. Of course, there are many factors to consider when choosing the most suitable filter for a specific industrial application. In this article, youāll learn more on the comparison between fixed and mobile units.
Fixed industrial filters
In general, fixed filters tend to be more cost-effective than their mobile counterparts for lower flow rates (<20,000 m3/h). However, relying on fixed facilities implies a series of challenges:
- Higher cost: Buying a fixed unit implies a greater upfront investment (i.e., capital expenditure (CAPEX)). On top of this, companies have to consider operational expenditure (OPEX) too. Specifically, once saturated, the spent carbon needs to be vacuum extracted and the filter to be refilled with fresh carbon. This is likely to take two workers several hours or even multiple days, a costly downtime that many canāt afford. Not to mention the financial onus of scaffolding, personal protective equipment (PPE) & training to protect workers during the process, etc.
- Safety issues: Aside from being an economic burden, replacing a fixed filter on site also poses safety risk. To begin with, operators will have to handle dust and hazardous waste. Additionally, the emptying of fixed filters by non-experts without taking appropriate safety precautions increases the fire risk from hotspots. The latter are areas of the filter bed reaching higher temperatures and potentially catching fire.
- Waste disposal: Getting rid of the spent carbon in a safe manner can be another sticky situation. Before an authorised and competent third party collects it, companies will have to store it on-site. That means arranging safety training, paperwork and obtaining environmental permits (i.e., more expenses). Furthermore, not all disposal routes are created equal. Although the current regulation allows firms to go for incineration in some cases, future legislation will push them to comply with more sustainable waste treatments.
- Lack of flexibility: An incorrectly dimensioned fixed filter cannot be fixed. Also, a change of purification needs over time will mean buying an extra unit or even downsizing your installation setup; this is not feasible with fixed filters, apart from changing it altogether.
No Filter
For the sake of transparency, it is worth mentioning Regenerative Thermal Oxidisers (RTOs) as a non-filtration technology. Pursuing this route makes more sense than industrial filtration when treating high volumes of polluted emissions, therefore avoiding the problem of frequent exchanges.
On the other hand, RTOs are not an efficient solution for discontinuous operations (e.g., batch production in the pharma sector), as they burn gas even when there is no flow requiring treatment.
“Mobile filters can be emptied off-site, preventing operators from exposure to hazardous waste and ensuring safe disposal by professionals.”
Although RTOsā efficiency may be higher in other cases, these units still require a hefty initial investment. Plus, companies will frequently need a temporary backup solution (e.g., activated carbon mobile filter) during their long-lasting yet compulsory maintenance.
Mobile filters
Although being less conventional, mobile filters have increased their market share globally over the last years. Their flexibility means that these mobile installations can overcome fixed filtersā limitations. Here are some of the advantages brought by this technology:
Higher safety
Unlike for fixed filters, mobile units can be emptied off-site. This prevents operators from being exposed to hazardous waste. Moreover, the spent carbon can be safely handled and treated by professionals at a dedicated facility, thus aligning disposal with waste treatment best practices.
Minimal disruption
Besides being safer, the exchange process of mobile filters is quicker as well (takes about 30 minutes). This avoids the revenue loss due to the lengthy fixed filter replacement. Furthermore, after being taken back, the exhausted filter will be checked, thus not wasting any production time for maintenance purposes.
Greater flexibility
Designed as components of a modular system, mobile filters can adapt to customersā needs or process condition variations.
For instance, if the flow to be treated reduces over time, you can:
- Remove a mobile filter if there were several or
- Replace a mobile filter by a smaller one.
On the other hand, when the volume to be treated increases (e.g. expansion of a chemical plant), more mobile filters can be added in parallel to equally distribute the flow over multiple mobile units.
In a situation where more stringent emission limits are to be met, adding one or more mobile filter units in series would be the most efficient solution. A single filter may no longer be adequate to comply with new regulations.
Therefore, instead of replacing the filter with a larger one, adding a second mobile unit for polishing could be a cost-effective way to extend the bed length. In particular, a lead-lag configuration can optimise the carbon consumption of two mobile filters in series.
Based on this rotating system, the second unit starts functioning only when the first filter is fully saturated. The saturated filter is then replaced by a new one, placed in second position.
Mobile filtersā adaptability is also given by their versatile functionality. In particular, these units can either work as standalone or together with other technologies as a pretreatment or downstream step (i.e., polishing).
Finally, dealing with mobile units makes it easier to measure their performance at dedicated labs off site and fine tune their efficiency.
“Fixed filters require costly downtime for carbon replacement, while mobile filters enable quick exchanges in about 30 minutes.”
A Case for Mobile Filters for Industrial Filtration
An Italian company recovers and recycles plastic boxes, mainly from the food industry. Their washing and recycling processes result in wastewater that contains a high level of COD (around 600 mg/L). Although the legal limit was 500 mg/L, the firm wanted to go down to 200 mg/L. They used to achieve their target COD reduction thanks to activated carbon fixed filters.
However, after increasing their production in 2019, those units were no longer able to cope with that demanding purification goal. Thatās when they reached out to DESOTEC whose engineers inspected the customerās filters and found that they were being clogged by suspended solids (SS) in the wastewater. Therefore, DESOTEC specialists put in place a 2-stage filtering process. This entails:
- Replacing the fixed filters with sand units to remove suspended solids from the wastewater;
- Installing an activated carbon mobile filter to remove COD.
The solution proved to be effective and was operational within just a few weeks of DESOTECās first site visit.
DESOTECās answer
To solve the starting riddle, DESOTEC has developed a full-service mobile industrial filtration solution based on activated carbon, assisting companies throughout the purification cycle (from pilot test to safe disposal or reactivation). Choosing a purification solution that suits a specific industrial application is not an easy task.
Aside from helping customers make the best decision, DESOTEC experts offer round-the-clock support and troubleshooting. Available for rental, DESOTEC mobile activated carbon filters allow firms to slash their initial investments. In addition to this, the full service solution provided includes an advanced process to reactivate the spent carbon at DESOTEC facilities, thus enabling a circular approach.
FAQs: Industrial Filtration ā Fixed or Mobile?
What are the main drawbacks of fixed filters?
High upfront cost, costly downtime during carbon replacement, safety risks for operators, inflexible sizing and challenging waste disposal
How do mobile filters improve safety?
They can be emptied off-site by professionals, reducing operator exposure to hazardous waste and ensuring safe disposal
Are mobile filters more flexible than fixed ones?
Yes, mobile filters can be added or removed based on flow changes and arranged in series or parallel to meet evolving process needs
How long does it take to exchange a mobile filter?
About 30 minutes, significantly reducing production downtime compared to fixed filter replacement
What industries benefit from mobile filtration solutions?
Industries with variable flow rates or stringent emission regulations, such as chemical processing and recycling operations
Can mobile filters be combined with other technologies?
Yes, they can operate standalone or as pretreatment or polishing steps with other systems
How does DESOTEC support mobile filtration users?
By offering rental options, full-cycle service including pilot testing, troubleshooting and carbon reactivation for sustainable filtration
