DONALDSON MEMBRANES FINDS FERTILE SOLUTION FOR INTERNATIONAL CHEMICAL PLANT 1

The production process involves a spray dryer which produces extremely fine dust – so fine that the conventional polyester glazed filter-bags originally installed had a lifetime of just one to two weeks.

After that, emissions of the dust became high and were easily detected, as they were red in colour and thus visible. In addition the pressure drop was so high that the bags had to be replaced too often, causing frequent delays in the production process, which was costly both in terms of downtime and capital outlay for replacement bags.

However the main concern was the environmental impact of the emissions. With legislation regarding pollution becoming increasingly more stringent the company was in danger of being forced to cease production altogether if they did not significantly reduce the emissions.

The baghouse has 170 bags and a surface filtration area of around 400m2. The company urgently needed a solution which was cost-effective but would also ensure longer life and, most importantly, near zero emissions.

Following a thorough inspection of the plant process, Donaldson Membranes recommended #8005 Tetratex High Efficiency Polyester Felt and the results have

been even better than anticipated.

“The original bags had an average lifetime of only one week whilst the new filter media has a lifetime of up to four months,” said Donaldson Membranes Sales Manager Jordi Ezquerro.

“The bags manufactured from Donaldson Membranes’ filter media have been performing for a year now, with three replacements, no problems with pressure drop and, most critically, virtually no emissions to the atmosphere. We are now ready to supply the fourth bag replacement with this material and the company is delighted with the results.”

Donaldson Membranes supplies four efficiency levels of Tetratex membranes:

Tetratex Release; Tetratex; Tetratex High Efficiency Membrane and Tetratex

Ultra High Efficiency Membrane.

Each membrane can make significant contributions to emission control in industries where atmospheric emissions are subject to strict regulation by legislation. The membranes can offer near zero emissions and exceptional dust cake release,

whilst also allowing for higher airflow rates at reduced constant pressure drop.

During the production process it is possible that expensive ingredients can be lost, breaching health & safety laws and becoming costly in terms of the actual product lost. Therefore, it is imperative that the filter media employed is capable of retaining vital ingredients and removing toxins without restricting airflow.

Expanded PTFE membranes have a microporous structure and hydrophobic characteristics. They are comprised of millions of randomly connected fibres, which are smaller than can be seen by the naked eye. These membranes are extremely water repellent whilst allowing air and moisture vapour to pass through. The result is an extraordinarily hydrophobic and breathable membrane.

In addition, the extreme chemical inertness of PTFE (polytetrafluoroethylene) allows Tetratex membranes to be used in many chemical processes where other materials are unsatisfactory. They are dimensionally and chemically stable in almost any environment ranging from –270ºC to 260ºC, making it eminently suitable for processes, which involve extremes of temperature.

In the case of the fertilizer application discussed here the results speak for themselves. #8005 Tetratex High Efficiency Polyester Felt has improved media life by a factor of 20 with a reduced pressure drop and virtually no emissions – all at a price, which is not prohibitive either. Thereby allowing the company to increase profits through reduced downtime and less capital expenditure.

Above all, environmentally, the investment has proved a huge success and the company can continue to operate with no fear of penalties or, even worse, being closed down.

Clearly, for applications employing fabric filter media, the best available control technology for the capture of fine and difficult particulate is recognised as ePTFE membranes.