An Experimental Study Of Hybrid Explosive Dust Gas Air Mixtures

Explosion hazards involving mixtures of different states of aggregation continue to occur in facilities where dusts, gases or solvents are handled or processed. In order to prevent or mitigate the risk associated with these mixtures, more knowledge of the explosion behavior of hybrid mixtures is required. The aim of this study is to undertake an extensive investigation on the explosion phenomenon of hybrid mixtures to obtain insight into the driving mechanisms and the explosion features affecting the course of hybrid mixture explosions. This was accomplished by performing an extensive experimental and theoretical investigation on the various explosion parameters such as: minimum ignition temperature, minimum ignition energy, limiting oxygen concentration, lower explosion limits and explosion severity. Mixtures of twenty combustible dusts ranging from food substances, metals, plastics, natural products, fuels and artificial materials; three gases; and six solvents were used to carry out this study. Three different standard equipments: the 20-liter sphere (for testing lower explosion limits, limiting oxygen concentration and explosion severity), the modified Hartmann apparatus (for testing minimum ignition energy) and the modified Godbert–Greenwald (GG) furnace (for testing minimum ignition temperature) were used. The test protocols were in accordance with the European standard procedures for dust testing for each parameter. However, modifications were made on each equipment in order to test the explosion properties of gases, solvents, and hybrid mixtures. The experimental results demonstrated a significant decrease of the minimum ignition temperature, minimum ignition energy and limiting oxygen concentration of gas or solvent and increase in the likelihood of explosion when a small amount of dust, which was either below the minimum explosion concentration or not ignitable by itself, was mixed with gas or solvent and vice versa. For example, methane with minimum ignition temperature of 600 °C decreased to 530 °C when 30 g/m3 of toner dust, which is 50 % below its minimum explosible concentration was, added. A similar explosion behavior was observed for minimum ignition energy and limiting oxygen concentration. Furthermore, it was generally observed that the addition of a non-explosible concentration of flammable gas or spray to a dust-air mixture increases the maximum explosion pressure to some extent and significantly increases the maximum rate of pressure rise of the dust mixture, even though the added concentrations of gases or vapor are below its lower explosion limit. Finally, it could be said that, one cannot rely on the explosion properties of a single substance to ensure full protection of an equipment or a process if substances with different states of aggregate are present.

Damaging accidental explosions are a continuous threat to industry. Categories for such explosions include combustible dust explosions; reactive gas explosions, both confined and unconfined; hybrid explosions involving both gases and dusts; bursts of pressure vessels and piping; and liquid propellant explosions. This book evaluates the physical processes and resulting blast effects for these types of explosions. Special attention is given to reactive gas explosions, both confined and unconfined. This latter class of explosion has occurred all too frequently in refineries and petrochemical complexes, and is also one of the most difficult to predict and evaluate. Much recent work on this topic is reviewed and summarized. This is the only publication of its kind, to date, that offers such a thorough coverage of these types of industrial explosions. [p] Each class of explosion source is reviewed separately, first discussing fundamentals, then presenting methods of analysis and testing, and finally giving curves or equations to predict effects of the particular class of explosion. An extensive bibliography is included together with tables of pertinent properties of explosive materials. The text also includes many figures, equations, tables and a keyword index. The book is intended for researchers in the field of characterizing and mitigating industrial explosions. It will also be of interest to engineers, scientists, and insurers involved in processes.

In all the diverse industries-from food and agriculture to plastics- where combustibledust exists, the possibility of an explosion looms as an ever-present threat. Gathering awealth of practical , theoretical , and experimental data, this important work provides a‘state-of-the-art study of the Development and Control of Dust Explosions, promotingimproved control over such hazards.Comprehensive in scope, this single-source reference presents invaluable guidelines for awide variety of planning and operational activities , including calcu lation of explosionpressure and vent area required to minimize explosion damage . . . the development ofmathematical mode ls used in the evaluation of explosion phenomena . .. determinationof the effect of numerous factors on explosion development ... and control and preventionof the ignition of dust by eliminating the fines in a product.With this outstanding book, industrial, safety , mechanical , manufacturing, loss prevention, fire protection, and chemical engineers; as well as plant managers, operators, anddesigners ; and all other specialists concerned with the possibility of dust exp losions nowhave an authoritative reference. The book also serves as the basis for further research inthis important field. In addition , the unique range of data included makes th is volumeideal for in-house training programs, professional seminars, and college-level coursesstudying explosion safety and safety engineering .