Process gases from the production of high density ammonium nitrate (HDAN), ammonium nitrate (AN) based fertilisers (and explosives grade low density ammonium nitrate) are contaminated to differing degrees by soluble or insoluble solids and ammonia (NH3), which then require gas scrubbing or gas filtering equipment installed to prevent harmful emissions to the atmosphere.
Fibre-bed technology has been used for decades and with Brownian diffusion type designs emissions of AN and NH3 from prilling towers can be minimised. A key requirement for using fibre-bed candle filters is that there are no insoluble elements in the exit air, which would block the filters. Fibre-bed candle filters using P.T.F.E. media can sometimes also be used to treat the vapour from AN neutralisers, capturing AN particles and NH3.
Where there are insoluble solids present, for example calcium ammonium nitrate production and emissions from granulators and dryers, then there are various designs of gas scrubbing equipment that can be implemented, to achieve legally required atmospheric emission limits, while being as maintenance-friendly as possible. To improve operational performance and to minimise down-time and cleaning, optimised packing materials for vertical and cross-flow fume scrubbers, deliver longer life and better results. Solid particles and ammonia fumes can also be handled without risk of blocking using the Begg Cousland ‘Becoflex™’ rotary brush technology, which is a highly efficient and low energy package system, that requires significantly less liquid than most other wet scrubbers.
There is no single technology that is right for all the processes, locations and environmental emission limits worldwide. This paper will review and give examples of these issues, solutions and results.