Transfer of powders into flammable solvents overview of explosion hazards and preventive measures: Fid-Bau Portal

Transfer of powders into flammable solvents overview of explosion hazards and preventive measures

Glor, Martin

This paper evaluates and analyses the explosion hazards associated with transfer operations of powders into large containers, hoppers and reactors, which may also contain flammable solvent vapours. The formation and characteristics of explosive atmospheres and the occurrence of process inherent ignition sources, such as static electricity are described. The most commonly applied preventive measures and technical equipment are outlined and discussed including their advantages and disadvantages. During transfer operations of powders into reactors, containers or agitators preloaded with flammable solvents many fires and explosions have occurred in the past in different branches of industry. Even in the absence of flammable gases or vapours, transfer operations may lead to fires and explosions, particularly if explosion sensitive powders (low MIE) are involved. Such operations are frequently still performed manually. As a consequence personnel are always affected in case a fire or explosion occurs. According to the present state of the art such transfer operations should nowadays always be performed in a socalled closed way into preinerted reactors or containers. Care must be taken that the required low degree of oxygen concentration is maintained during and after the transfer. As outlined above, the safety of most of these systems, which use gravity for transfer is far from absolute and depends on powder characteristics (bulk density, etc.) and process conditions. In the worst case, a process, which is considered safe for a specific activity can become unsafe in case one of the process parameters is changed and a new risk assessment has to be carried out. The PTS, however, as is does not use gravity and can eliminate the air comprised in the powder, is particularly safe and functions independently of the process parameters and powder characteristics. In view of the flexibility and frequent changes required of a production facility and due to the pressure on manufacturers for continuing process optimisation, it is important to select charging equipment that can guarantee full safety at all times, independently of the process parameters and powder characteristics.