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Nitrogen Reduction by Advanced Adsorbers Also Successful in Thermal Waste Treatment

A technology based on natural materials converts nitrogen oxide emissions into basic materials for fertilizers. Now this technology is being tested for the first time on a large scale for thermal waste treatment.

At its core is an adsorber developed by Krajete GmbH, which is already being used successfully in the automotive and mining industries and for cleaning city air. This has now been adapted to the requirements of thermal waste disposal and a test in real operation is imminent. This was preceded by extensive, successful laboratory tests of the zeolite-based adsorber, which can make an important contribution to the circular economy.

Thermal waste treatment not only produces valuable energy, but also emission gases such as nitrogen oxides. In most cases, these are captured using complex filter or catalytic methods whose effectiveness is optimized for high pollutant emissions. A zeolite-based process from Krajete GmbH works more simply and also at low pollutant concentrations. Against the background of steadily decreasing legal limits, the technology has now also been optimized for waste management and can thus be evaluated in the real operation of a waste disposal plant. Another advantage of the technology that makes it interesting for the circular economy: the bound nitrogen oxide can be easily recovered and simply converted into agricultural fertilizer.

Potential Beats Problem

"We specialize in converting problematic emissions as completely as possible into valuable basic materials through natural processes," explains Dr. Alexander Krajete, CEO of Krajete GmbH. "Our adsorber technology therefore binds NOx even at low pollutant concentrations below 1,000 ppm and additionally allows its recovery, concentration and simple further processing into nitrogenous fertilizer. This is how we leverage the natural potential of the gas. What was a pollutant yesterday will be the basis of valuable materials tomorrow."

Attention was drawn to the adsorber technology in the Netherlands, where nitrogen oxide emissions are a massive problem and Krajete GmbH has already been active for several years.

The principle of Krajete technology is the physical binding of nitrogen oxides to a specially prepared zeolite matrix. From this, the filtered-out gases can be recovered cost-effectively and easily in concentrated form. "And best of all," says Dr. Krajete, "the zeolite remains undamaged in the process and can be reused. It's a sustainable principle that turns exhaust gases into valuable materials."

Almost NOx-Thing Escapes

To ensure successful use in a large-scale plant, the adsorber material was extensively tested in the laboratory beforehand. In some cases, gas was even used, which was captured directly at chimneys of waste incineration plants and transported over 1,000 km to the headquarters of Krajete GmbH in Austria. Says Dr. Krajete: "We were able to show that our adsorber removes 99 percent of the nitrogen oxides from the gases - even at the low concentrations of less than 1,000 ppm mentioned above."

Following the successful laboratory studies, Krajete GmbH worked out a design for the construction and installation of a "slip-stream adsorber" that can be easily installed in existing plants for the thermal recycling of waste. Long-term data will then be collected in real operation and further scaling will be assessed. "What we're also interested in here," explains Dr. Krajete, "are other pollutants like sulfur dioxide and heavy metals. We already know that these are also bound by the adsorbent material, but too little about the extent to which this occurs." Another aspect of a long-term study will then be the lifetime of the adsorber material in real-world operation.

Against the backdrop of falling NOx emission limits, the increased interest in the cost-effective and simple Krajete technology is understandable. The interest shown by the waste management industry - following successful start-ups in the automotive and mining industries as well as for cleaning urban air - also demonstrates the high flexibility of this technology to meet the requirements of a wide range of industries.

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