(49a) Chemical Explosion Isolation For Small Contained Vessels

Particle size reduction equipment are used in many branches of the process industries, such as food, chemical, pharmaceutical and energy. According to statistics, they are among the most likely places for a dust deflagration to occur. Within this equipment, a dust cloud comprising fine particles is continuously present and mechanical impacts from moving parts represent a highly credible ignition scenario.

An ongoing debate is whether or not small enclosures need to be equipped with explosion protection measures. Because particle size reduction equipment typically exhibit a fairly strong design (explosion pressure resistance up to several bar) and comprise inlets and outlets which act like pressure relief area, it is a common belief that venting or suppression are not necessary. However, no experimental data can be found in the open literature to confirm this expectation. Also, the possibility for the explosion to propagate into linked process equipment through the inlets and outlets has not been addressed, so the need for explosion isolation remains unclear.

An experimental investigation was hence carried out to address these issues. Dust deflagrations were performed in a small vessel capable of withstanding high pressures. Several configurations were tested, varying dust type, dust concentration, and pipe length (inlet and outlet). Chemical isolation effectiveness was also examined for such high reduced pressure applications. Dust was injected inside the pipes to promote flame propagation and create challenging conditions. Application limits, specifically focusing on installation distance, were studied. The effect of chemical isolation upon downstream pipeline pressure was also investigated.