Air After Treament

 

High Quality Compressed Air - Working with Beko Technologies

 

 
Oil Free Compressed Air 
 
Oil free compressed air means...well what exactly does it mean? The output of an oil free compressor perhaps or could be ISO 8753 specified with the possibility to specify something better than Class 1 for Hydrocarbons. Another possibility is the compressed air taken from a lubricated machine and then treated to become "technically oil free" compressed air. Many will have an opinion on which is the best way of doing this but there has been no definitive answer.

BEKO Technologies offer a new method of producing oil free compressed air, the BEKOKAT system which is based on the Catalytic Converter method. We are pleased to report that the first unit installed has now run for more than 1 year trouble free with zero maintenance costs. The unit is running in a food factory in North Yorkshire and the only incident was a site power outage requiring a resetting of thermal protection.

Let us take a look at the pros and cons of the different solutions.

1. Oil Free Compressor. There are many types and manufacturers offering customers choice of well proven machines. They are very reliable and up to 10 year service/ extended warranty packages are widely available. The initial capital cost of oil free compressors is high compared to lubricated types. Maintenance costs are usually spread over a 10 year period to mask the high cost of changing LP and HP air ends at around 40,000 hours

The writer having sold many units is convinced that there is no problem of screw or centrifugal types adding oil to the inspired air. However there could be a question mark over the quality of the air being drawn into the compressor. Normal urban/industrial ambient air contains approximately 150 million particles. More than 75% of these particles are below the pore size of the compressor inlet filter. Hydrocarbon content will vary but could be as high as 0.5 mg per cubic metre. Is the air leaving an oil free compressor located in Ellesmere Port or Grangemouth really 100% oil free? Only if it is subsequently treated to remove any contaminants. It is very common to see an oil free compressor installation with no further filtration downstream except to protect a dryer.

2. There is of course an option to use a standard lubricated compressor and use a series of coalescing filters and carbon filters to reach the specified quality. There will be a significant cost benefit in doing this for reasons already mentioned. The questions that need to be asked are firstly which filtration system or components are needed then how much cost will this involve? There will be pressure drops at each component stage of the filtration system and an annual or more frequent filter element change will be needed. A system with filtration to ISO 8573 Class 1 could easily exceed 1 bar in pressure drop from new increasing as the filter clogs. This equates to an increase in power which is easy to calculate and a number of filter and carbon elements that are known costs.

Also it should be borne in mind that the performance of filters is specified at 21 deg C and that to be achieving this temperature the air would be taken in at 11 deg C. So the performance of the filters is as specified during the winter months and some nights in the spring and autumn periods but how many compressor houses will be adequately ventilated and the air taken from outside? The performance graph of oil carry over versus temperature is logarithmic so it is important to be realistic about the temperature that the air will go on to the filters. Activated carbon filter life will be considerably lower than the other components and unless installed as a "carbon tower" rather than a filter can be prohibitively expensive because of short operating life.

3. BEKOKAT Catalytic Converter. The operating principle of the Catalytic converter is very simple, like the one in your car, which will together with heat break down long hydrocarbon chains into water and carbon dioxide. There is no need to worry about green credentials as we are talking about treating compressed with say 2 or 3 ppm of oil content. The advantages of the Catalytic Converter method are that the quality of the compressed air output is not dependent on the quality of air at the inlet. Routine maintenance costs are also very low. Some will have heard that there is a high energy input and possibly that there have been fires in the catalyst vessels. There is more than one brand on the market but the BEKO design ensures that the lifetime cost analysis is competitive against other systems and could be considered as the only way to be 100% sure that there are no hydrocarbons getting through the compressor or the treatment system. Beko design has a lower temperature and no direct contact between heaters and catalyst hence minimising any possible danger of fires in the catalyst. The BEKOKAT is very well suited to point of use applications where the quality of the air required is significantly higher than the normal factory air and the usual solution would be to buy a dedicated oil free compressor or a filtration system.

The disadvantages of catalytic converters are currently the range is not suitable for very large flows and BEKOKAT is not a low cost product. The maintenance is simple in that the catalyst will need to be changed at 20,000-30,000 hours. The best solution for users would be a maintenance contract with the cost of the catalyst amortised in a similar way to the type of contracts common to screw compressor amortise the air end change.

The object of this article is simply to point out that there is an option to arrive at high quality - 0.003mg/m3 using a simple catalyst and heater system. The third way!

There is now a third way of reaching high quality oil free compressed air.
 
(Article Courtesy of Beko Website)
 
 
 
 
 

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