Food grade compressed air for herbs and spices production

In principle, there are three imported dangers when using compressed air in the food sector: moisture, contamination and oil. As soon as air is compressed the concentration of dirt particles will increase with no less than 700%. Because sucked in air always contains dust and other particles (sometimes even chemicals) this phenomenon must be taken into account seriously. Besides that, moisture in combination with raised temperatures is an ideal culture medium for bacteria. So drying the compressed air well after the compression is a second point of attention. For this, cool dryers or adsorption dryers can be used. Then there is the lubricant/coolant that is used with oil lubricated and oil injected compressors and what has to be filtered out. To circumvent this, oil-free screw compressors can be used, but that means losing some of the energetic efficiency. These have a higher energetic efficiency than oil-free compressors without water injection and as added advantage that the dirt particles in the sucked in air are flushed out partly by the injected water. The investment is a little higher however, but it is the way to go for critical compressed air applications, because of the dirt particles that are always present in the sucked in air. It is always advisable to place a filter system after the compressor, to remove residual moisture, dirt and oil particles from the compressed air. For very critical situations there are active carbon filters that eliminate the last oil particles and sterile filters, that remove bacteria from the compressed air. For every situation a solution can be created that is tailored in multiple aspects.

René de Vries, head of the technical department, explains which production steps we encounter with this well-known manufacturer. “We process herbs and spices from various countries all over the world here. The first step is a steam treatment under high pressure, a technique Euroma developed itself. This will decontaminate spices in a natural way instead of, which was usual until then, treating the products with ethylene oxide or gamma radiation. After the steam treatment, depending on the desired end product, follow treatments such as grinding, weighing, mixing and packing. Whether or not mixed with other ingredients.

“During the production, we also look very critically at the energy and environmental impacts of applied processes," René de Vries mentions. "We follow, among other things, the guidelines as established by the British Compressed Air Society (BCAS) and the British Retail Consortium (BRC). Some quite old compressors were installed which were actually working fine, but the power was not distributed optimally. This could be more effective and especially more energy efficient. We also suffered from moisture in the pipeline. Although it did not reach the products, it contributed to a higher moisture level in the factory. With renewal of the compressed air system we wanted to solve that too. We asked a number of suppliers to make an offer for a completely new compressor installation. ALUP Kompressoren finally became the winner, and they also presented an interesting service proposition."

"We have measured the compressed air usage very detailed during a week," says Ron Snoeren, Sales Engineer at ALUP Kompressoren. “We looked at the average consumption, but also especially at the peak consumption. Because the latter determines the maximum capacity that should be supplied. Partly you have to solve this with larger compressors, but when the spikes do not last too long, you can also do very well with buffer tanks. Because there is some distance between the production buildings (with a pipeline under the road), we have advised to place a buffer tank in both places. For the compressors we have chosen as far as capacity allocation for 3 x 37 kW. This in the form of two Largo's with a fixed compressor speed and an Allegro of which the compressor speed is demand-driven with a frequency controller. This way you can almost run the compressors all the time in their "ideal range". Furthermore now there is some redundancy so this installation is very reliable and during servicing of the compressors compressed air will always be available.

Moisture is taboo in the food sector. It was decided after consultation with Euroma’s department of quality to achieve an as low as possible dew point. That is only possible with an adsorption unit, so the choice was easy. Then to be sure that the air was clean and odourless, an activated carbon adsorber was placed after the adsorption unit, resulting in dry, odourless, clean and also completely oil-free compressed air.

Of the Total Cost of Ownership of a compressed air installation the energy costs are as much as 75%. The remaining 25% are the costs for purchase and maintenance. Through monitoring, leakage management and system optimization, in many cases the compressed air related energy consumption can be considerably reduced.

A second and very important saving opportunity is leakage management. With detecting compressed air leaks and repairing them, and then monitoring the pipeline, often realizes several dozen per cents of energy savings. Leak detection is simple and it is therefore incomprehensible that in many factories this is done too little.

When the system is dimensioned well and technically OK, one can go on optimizing. Think of lowering the working pressure in small steps. Every bar pressure reduction means 7% lower costs for energy. Besides that, heat recovery is an excellent way to gain more return from the installation. “In our aim for durability an energy-conscious compressed air installation fits perfectly of course,” according to René de Vries. “Together with an installation company we made a Total Cost of Ownership (TCO) calculation with as starting point energy recovery by means of heat exchangers on all three compressors. These exchangers are included in the oil cooling circuit and thus take the heat from the oil. With this recovered heat first we wanted to heat water as pre-phase for the production of steam, but it proved to be more lucrative to heat an adjacent warehouse with it. During the total lifetime of the installation this will bring us significant savings in the form of a lower gas bill. The total investment (hardware and installation costs) of the new air heater in the storehouse is thus fully recovered in the foreseeable future."