Explosives, hazards

Example 9.1 A process involves the use of benzene as a liquid under pressure. The temperature can be varied over a range. Compare the fire and explosion hazards of operating with a liquid process inventory of 1000 kmol at 100 and 150°C based on the theoretical combustion energy resulting from catastrophic failure of the equipment. The normal boiling point of benzene is 80°C, the latent heat of vaporization is 31,000 kJ kmol the specific heat capacity is 150 kJkmoh °C , and the heat of combustion is 3.2 x 10 kJkmok. ... 

When we consider sources of methane we have to add old methane methane that was formed millions of years ago but became trapped beneath the earth s surface to the new methane just de scribed Firedamp an explosion hazard to miners oc curs in layers of coal and is mostly methane Petroleum deposits formed by microbial decomposi tion of plant material under anaerobic conditions are always accompanied by pockets of natural gas which IS mostly methane... 

Heating triacetylboron at temperatures above its melting poiat, 123°C, causes a rearrangement to B20(0CCH2)4 (15). An explosive hazard is also generated by dissolving BF ia anhydride (see Boron compounds). 

When dispersed as a dust, adipic acid is subject to normal dust explosion hazards. See Table 3 for ignition properties of such dust—air mixtures. The material is an irritant, especially upon contact with the mucous membranes. Thus protective goggles or face shields should be worn when handling the material. Prolonged contact with the skin should also be avoided. Eye wash fountains, showers, and washing faciUties should be provided in work areas. However, MSDS Sheet400 (5) reports that no acute or chronic effects have been observed. 

Copolymerization is effected by suspension or emulsion techniques under such conditions that tetrafluoroethylene, but not ethylene, may homopolymerize. Bulk polymerization is not commercially feasible, because of heat-transfer limitations and explosion hazard of the comonomer mixture. Polymerizations typically take place below 100°C and 5 MPa (50 atm). Initiators include peroxides, redox systems (10), free-radical sources (11), and ionizing radiation (12). 

Checklists. A checklist is simply a detailed Hst of safety considerations. The purpose of this Hst is to provide a reminder to safety issues such as chemical reactivity, fire and explosion hazards, toxicity, and so forth. This type of checklist is used to determine hazards, and differs from a procedure checklist which is used to ensure that the correct procedure is followed. 

The Dow Fine and Explosion Index is a useful method for obtaining an estimate of the relative fine and explosion hazards associated with flammable and combustible chemicals. However, the technique is very procedure oriented, and there is the danger of the user becoming more involved with the procedure than the intent. 

Iron dust does present a moderate fire and explosion hazard when exposed to heat and flame. Although normally not very reactive, under certain circumstances iron can react with water to Hberate flammable hydrogen gas. 

Polymerizations of methacrylic acid and derivatives are very energetic (MAA, 66.1 kj/mol MMA, 57.5 kJ/mol = 13.7 kcal/mol). The potential for the rapid evolution of heat and generation of pressure presents an explosion hazard if the materials are stored ia closed or poorly vented containers. 

Physical Properties of Monomers. 1-Butene [106-98-9] is a colorless, flammable, noncorrosive gas its physical properties are fisted in Table 1, and its thermodynamic properties are available (16). Because 1-butene has a very low flash point, it poses a strong fire and explosion hazard. 

There are explosion hazards with phthahc anhydride, both as a dust or vapor in air and as a reactant. Table 11 presents explosion hazards resulting from phthahc anhydride dust or vapor (40,41). Preventative safeguards in handling sohd phthahc anhydride have been reported (15). Water, carbon dioxide, dry chemical, or foam may be used to extinguish the burning anhydride. Mixtures of phthahc anhydride with copper oxide, sodium nitrite, or nitric acid plus sulfuric acid above 80°C explode or react violently (39). 

Many plants outside of North America pfill or granulate a mixture of ammonium nitrate and calcium carbonate. Production of this mixture, often called calcium ammonium nitrate, essentially removes any explosion hazard. In many cases calcium nitrate recovered from acidulation of phosphate rock (see Phosphoric acid and the phosphates) is reacted with ammonia and carbon dioxide to give a calcium carbonate—ammonium nitrate mixture containing 21 to 26% nitrogen (23). 

Threshold limit values for the components of cemented carbides and tool steels are given in Table 14 (176). There is generally no fire or explosion hazard involved with tool steels, cemented carbides, or other tool materials. Fires can be handled as metal fires, eg, with Type D fire extinguishers. Most constituents of tool materials do not polymerize. 

Finely divided barium is susceptible to rapid, violent combination with atmospheric oxygen. Therefore, in powdered form it must be considered pyrophoric and very dangerous to handle in the presence of air or other oxidising gases. Barium powder must be stored under dry argon or helium to avoid the possibihty of violent explosions. Massive pieces of barium, however, oxidize relatively slowly and present no explosion hazard if kept dry. 

Manufacturers of benzene are requited by federal law to pubHsh Material Safety Data Sheets (MSDS) that describe in detail the procedures for its safe handling. Benzene is classified as a flammable Hquid and should be stored away from any potential source of ignition. Fine and explosion hazard data for benzene are shown (91). 

Bromates represent a potential fire and explosion hazard if heated, subjected to shock, or acidified. They should not be allowed to contact reactive organic matter, including paper and wood. Industrial quantities are packed in fiber dmms with polyethylene liners or in metal dmms. Laboratory quantities are supphed in glass bottles. For shipment, a yellow oxidizer label is required under DOT regulations. 

Calcium metal and most calcium compounds are nontoxic. In massive pieces the metal does not spontaneously bum in air. Calcium can be touched with dry bare hands without harm. Care must be taken, however, to avoid contact with water owing to the exothermic Hberation of hydrogen and the resulting explosion hazard. Calcium must always be kept dry and preferably sealed in the shipping containers. 

Compressed air or hydrauHcally driven reciprocating piston or rotary exciters are sometimes used in short conveyors. They are particularly useflil where explosion hazards limit the use of electrical drives. 

The electrochemical process industries are confronted with a wide range of hazards. These include electrical hazards, various explosion hazards, and the hazards associated with exposure to reactive chemicals. 

Explosion Hazards. The electrolysis of aqueous solutions often lead to the formation of gaseous products at both the anode and cathode. Examples are hydrogen and chlorine from electrolysis of NaCl solutions and hydrogen and oxygen from electrolysis of water. The electrode reactions. 

A concentration of 35,000 ppm in air produces unconsciousness in 30—40 minutes. This concentration also constitutes a serious fire and explosion hazard, and should not be permitted to exist under any circumstance. Any person exposed to ethyl ether vapor of any appreciable concentration should be prompdy removed from the area. Recovery from exposure to sublethal concentrations is rapid and generally complete. Except in emergencies, and then only with appropriate protective equipment, no one should enter an area containing ether vapor until the concentration has been found safe by measurement with a combustible-gas indicator. 

Explosibility and Fire Control. As in the case of many other reactive chemicals, the fire and explosion hazards of ethylene oxide are system-dependent. Each system should be evaluated for its particular hazards including start-up, shut-down, and failure modes. Storage of more than a threshold quantity of 5000 lb (- 2300 kg) of the material makes ethylene oxide subject to the provisions of OSHA 29 CER 1910 for "Highly Hazardous Chemicals." Table 15 summarizes relevant fire and explosion data for ethylene oxide, which are at standard temperature and pressure (STP) conditions except where otherwise noted. 

Table 15. Fire and Explosion Hazard Evaluation Data...

In selec ting the machines of choice, the use of specific speed and diameter best describe the flow. Figure 10-67 shows the characteristics of the three types of compressors. Other considerations in chemical plant service such as problems with gases which may be corrosive or have abrasive solids in suspension must be dealt with. Gases at elevated temperatures may create a potential explosion hazard, while air at the same temperatures may be handled qmte normally minute amounts of lubricating oil or water may contaminate the process gas and so may not be permissible, and for continuous-process use, a high degree of equipment rehability is required, since frequent shutdowns for inspec tion or maintenance cannot be tolerated. 

Pneumatic and hydraulic vibrating conveyors have as their greatest asset ehmination of explosion hazards. If pressurized air, water, or oil is available, they can be extremely practical since their drive design is relatively simple and pressure-control valves can be used to vaiy capacity either manually or automatically. 

Explosion hazard when treating combustible gases and/or collecting combustible particulates... 

Concentrations of some dusts in the collector ( 50 g/m ) forming a possible fire or explosion hazard if a spark or flame is admitted by accident possibihty of fabrics burning if readily oxidizable dust is being collected... 

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