Process air technology

I. Process-air systems in the foodstuffs/drinks industry

Avoiding contamination and creating uniformly constant manufacturing conditions

For the foodstuffs and drinks industry, the process-air preparation frequently represents an integral component part of the foodstuffs manufacturing process. In this case, it often involves high air purity which is generated with high-quality air filters. Every form of pollution should be avoided, as well as contamination through microbiologically-relevant organisms. Only this way the high purity requirements on foodstuff can be met. Process air is also required in order to achieve very constant manufacturing conditions, for example with heat treatments or drying processes. High-tempered airflows are required in milk powder manufacture, in order to generate a very fine milk powder in the turbulent-flow process from finely sprayed milk droplets.

Kalthoff air filters are non-hazardous to foodstuffs

Even if the food comes into direct contact with the filter, any release of impairing substances, regardless of what they are, must be excluded. Also no hazard to the quality of the foodstuffs may be present in the case of failure of individual components.

Kalthoff air filters from synthetic composite nonwovens do not have any “shedding effect”, therefore no fibre break or fibre blow-off occurs, as it is the case with glass-fibre papers. The filters are thermally bonded and suitable for the FDA-conforming and GMP-conforming production of foodstuffs. Even if air filters are used in food manufacture for the processing of process air and do not come in direct contact with foodstuffs, no hazard arises from them.

Outside of the manufacturing process

Also outside of manufacturing processes, conditioned, filtered process air plays an important role. To be mentioned here are e.g. packaging processes which occur under constant pure inert atmosphere. Also the generation of PET bottles, the filling procedures and the pneumatic transport of bottles are implemented with the aid of filtered process air. High-quality air filters are always to be found at essential locations within the food industry.

Filter types used in the food industry:

Fine dust bag-type filtersMULTIFOLD Pocket Filter TCC 85 – TCC 98
Fine dust panel filtersPanel Filter RELIM
Fine dust compact filtersCompact Filter RELIM VRK


II. Process-air systems in power generation

In traditional power generation with power stations, large volumes of cleaned combustion air are required. After mixing with the respective fuel, a controlled combustion process occurs, which drives the generation of electrical energy, generally over turbines.

Avoiding “fouling” in turbines by the employment of air filters

Turbines are technically-complex, sensitive systems which are highly stressed thermally, mechanically and chemically. Air filters eliminate disturbing contamination and thus prevent the deposition of substances on the turbine blades. The feared “fouling” not only reduces turbine efficiency, but can involve expensive maintenance work or, on a long-term basis, can even result in damage or failure of the process. Filters must filter highly-efficiently here, they must guarantee long-term operating times, be mechanically extremely stress tolerant and be provided with high safety margins in total. It must be reliably excluded that stress damages occur to the filter during operation, even under the severe action of moisture. Charging tests, such as burst pressure tests, are a suitable way to qualify air filters.

To air purity in 3-filter stages

The filtration process in gas turbines progresses in a 3-stage process. In the first filter stage (coalescer), very coarse aerosols and moisture droplets are removed. Coarse dust filter cells, as well as coarse dust bag-type filters are to be used for this purpose. Following this, medium dusts are removed. Finally the end-filtration occurs to achieve the required supply-air quality. Here a development to increasingly higher purities up to HEPA level can be determined. Therefore multi-sided sealed compact filters are used, which achieve particularly high filter surfaces through the use of a V-shaped structure.

Filter types used in power generation:

1. Filter stage
Coarse dust panel filtersPanel Filter WU
Coarse dust bag-type filtersMULTIFOLD Pocket Filter T/TQ 35
2. Filter stage
Medium dust bag-type filtersMULTIFOLD Pocket Filter TC/TCQ 60 – TCC 65
3. Filter stage
Fine dust compact filtersCompact Filter RELIM VRK BLUE LINE
HEPA filtersHEPA-Filter Cell


III. Process-air systems in coating technology

Under the term coating technology processes are summarised, where the application of additional layers results in new surfaces with required characteristics. In case of paint-application and coating processes, air filters are required both in the supply-airflow as well as in the exhaust-airflow.

Air supply filter for optimum paint-coating results

In order to generate optically-smooth and technically high-quality, undisturbed surfaces, a particle-pure supply air must be provided. However, a uniform, turbulence-free paint application is also to be provided at the same time. For this purpose, paint particles are atomised very finely and scattered in a uniform, laminar air stream with defined velocity and direction. The designs and quality of the air filters are a decisive factor in the flow progress between the supply and removal volume flow. If these conditions can be held constant for as long as possible, optimum paint-coating results are the result. The employment of coarse and fine dust bag-type filters, as well as filter pads as ceiling filters can contribute to this.

Exhaust air filters remove surplus paint contents (overspray) and maintain the air-exhaust systems paint-free and functional. Adsorptive-acting filter types remove solvent residues or volatile component parts. For this, exhaust-air bag-type filters are used (see special filter types), as well as filter pads. For the solvent removal, there also exists the possibility to use activated carbon filters.

Air filters used in coating technology:

Air-supply filtration
Coarse dust bag-type filtersMULTIFOLD Pocket Filter T/TQ 35
Fine dust bag-type filtersMULTIFOLD Pocket FilterTCC 85- TCC 98
Filter padsFilter Media CC 600 G
Filter Media CC 600 GC 85/95
Exhaust-air filtration
Filter padsFilter Media GLASS GREEN
Special filter typesDry Paint Arrestor TSW
Activated-carbon unit
Activated-carbon filtersActivated Carbon Catridge AVPC