Which explosion protection concepts are relevant for fertiliser and crop protection formulations?
Explosion protection concepts must be designed individually for each formulation and each process. Not every powder is combustible or explosible. The basis is a hazard assessment, an explosion protection document and sound substance data, for example minimum ignition energy, ignition temperature, maximum explosion pressure and KSt value. With solvent-containing formulations, flash point, explosion limits and possible hybrid dust-gas atmospheres must also be assessed.
The governing references are in particular the ATEX directives 1999/92/EG and 2014/34/EU, the German Hazardous Substances Ordinance, the Industrial Safety Regulation and TRGS 720 ff. The protection concept follows three stages: avoid an explosible atmosphere, prevent effective ignition sources and limit the possible consequences of an explosion.
Primary explosion protection reduces dust release and hazardous dust deposits or limits the concentration of combustible solvent vapours. Inerting can be worthwhile in closed machines where the oxygen concentration is kept permanently and reliably below the product-specific limiting oxygen concentration. It requires suitable measurement, control and interlock technology as well as an assessment of the risk of asphyxiation.
Where an explosible atmosphere cannot be reliably excluded, secondary explosion protection prevents effective ignition sources. This includes zone classification, suitable ATEX equipment, earthing and equipotential bonding, protection against electrostatic charging and the limitation of hot surfaces and mechanically generated sparks. Zones 20, 21 and 22 apply to dusts, and zones 0, 1 and 2 to gases and vapours.
Constructional explosion protection limits the consequences of an explosion. Depending on the risk, explosion-pressure-shock-resistant construction, pressure relief, explosion suppression and explosion decoupling may be considered. With toxic crop protection active ingredients, it must be examined with particular care whether pressure relief to the outside is permissible or whether, for example, suppression, decoupling or a pressure-shock-resistant design is more suitable.
Fertilisers containing ammonium nitrate must be considered separately. Here the focus is not necessarily on classical dust explosions but on thermal decomposition, the oxidising effect and hazardous reactions in the event of contamination or fire. Heat sources, impurities and joint storage with combustible or incompatible substances must be avoided.
An effective explosion protection concept therefore combines substance testing, a zone concept, technical protective measures, suitable operating instructions, maintenance and regular updating of the hazard assessment.
How amixon® implements explosion protection for dust-explosible powders
The right explosion protection begins with the design of the mixing technology. It is not only organic fertilisers that can form explosible dusts. Mixtures and formulated products can also be critical. What matters is the actual dust characteristics: KSt value (explosion severity), Pmax (maximum explosion pressure), minimum ignition energy (MIE), limiting oxygen concentration (LOC).
amixon® supplies suitable mixing systems for this purpose. The machines are consistently designed for ATEX Zone 20. This provides a high level of safety in the mixing chamber, even with changing products.
The mixers operate at low speed. The mechanical energy input remains low. Ignition sources such as friction and impact sparks are thereby reduced. At the same time the particle structure is protected.
The systems are of closed and dust-tight design. Dust escape is thus prevented. This markedly reduces the risk of secondary explosions. On request the machines are designed to be pressure- and vacuum-resistant.
Inerting is possible. Oxygen is displaced in a targeted way. Explosible atmospheres are thus avoided. Several process steps can be combined in one apparatus. Transfer operations are eliminated.
amixon® designs project-specifically on the basis of the URS and real substance data. The design is traceable and reliable. Trials in the pilot plant deliver sound results under real conditions.
amixon® thus stands out as a suitable manufacturer for the safe processing of dust-explosible products. The solutions are technically well-founded, proven in practice and designed for a high level of process reliability.