Hydrocarbon Explosion

John A. Davenport, Prevent Vapor Cloud Explosions, Hydrocarbon Processing (March 1977), pp. 205-214 and Orville M. Slye, Loss Prevention Fundamentals for Process Industry, Paper presented at AICHE Loss Prevention Symposium, New Orleans, LA, March 6-10,1988. 

Constructed wetlands are commercially available through a number of vendors and have been used to treat water contaminated with acid mine drainage, explosives, hydrocarbons, chlorinated solvents, phenols, agricnltnral wastes, and sewage. The RIMS2000 database discusses constructed wetlands for the treatment of acid mine drainage in summary number T0179. 

The PG7 rocket is known to contain the following black powder, a mix containing RDX explosive, hydrocarbon wax and an orange dye, PETN explosive, a mercury fulminate primer containing zirconium (see particles... 

DMM is highly flammable in the presence of strong oxidizing agents. Elevated temperatures cause decomposition into explosive hydrocarbon gases. 

Phytoremediation is the use of plants and trees to clean up metals, pesticides, solvents, explosive hydrocarbons, PAHs and leachates at contaminated sites. 

EXPLOSION and FIRE CONCERNS Dimethyl and diethyl mercury are easily flammable when exposed to heat or flame contact with strong oxidizing agents, such as chlorine, may cause fires and explosions decomposition to flammable and explosive hydrocarbon gases will occur at elevated temperatures toxic gases and vapors, such as toxic mercury fumes and carbon monoxide, may be released in a fire use carbon dioxide, dry chemical, or foam for firefighting purposes. 

There have been no signiflcant catalyst advances for methane ammoxidation since the disclosure of the Pt/Rh catalyst by Andrussow in the 1930s (112). Advances in the technology have been in the areas of process operability process safety, especially pertaining to handling of potentially flammable and explosive hydrocarbon/oxygen gas mixtures and in product recovery and ammonia recycle. Because of its many years of safe and dependable operation and its use of low cost natural gas feedstock, the Andrussow process remains the dominant technology for the commercial manufacture of HCN. 

Hydrocarbons generally have very low electrical conductivities and manipulation of these fluids creates electrostatic charges that can result in fire or explosions. This problem is encountered with gasoline and kerosene. 

An additional useful test is to distil the acid or its sodium salt with soda lime. Heat 0.5 g. of the acid or its sodium salt with 0 2 g. of soda lime in an ignition tube to make certain that there is no explosion. Then grind together 0-5 g. of the acid with 3 g. of soda hme, place the mixture in a Pyrex test-tube and cover it with an equal bulk of soda hme. Fit a wide dehvery tube dipping into an empty test-tube. Clamp the tube near the mouth. Heat the soda lime first and then the mixture gradually to a dull-red heat. Examine the product this may consist of aromatic hydrocarbons or derivatives, e.g., phenol from sahcyUc acid, anisole from anisic acid, toluene from toluic acid, etc. 

This reaction has often reached explosive proportions in the laboratory. Several methods were devised for controlling it between 1940 and 1965. For fluorination of hydrocarbons of low (1—6 carbon atoms) molecular weight at room temperature or below by these methods, yields as high as 80% of perfluorinated products were reported together with partially fluorinated species (9—11). However, fluorination reactions in that eta involving elemental fluorine with complex hydrocarbons at elevated temperatures led to appreciable cleavage of the carbon—carbon bonds and the yields invariably were only a few percent. 

Aluminum bromide and chloride are equally active catalysts, whereas boron trifluoride is considerably less active probably because of its limited solubiUty in aromatic hydrocarbons. The perchloryl aromatics are interesting compounds but must be handled with care because of their explosive nature and sensitivity to mechanical shock and local overheating. 

Properties of the principal hydrocarbons found in commercial hexane are shown in Table 9. The flash point of / -hexane is —21.7 °C and the autoignition temperature is 225°C. The explosive limits of hexane vapor in air are 1.1—7.5%. Above 2°C the equiUbrium mixture of hexane and air above the Hquid is too rich to fall within these limits (42). 

Centrifugal separators are used in many modem processes to rapidly separate the hydrocarbon and used acid phases. Rapid separation greatly reduces the amounts of nitrated materials in the plant at any given time. After an explosion in a TNT plant (16), decanters (or gravity separators) were replaced with centrifugal separators. In addition, rapid separation allows the hydrocarbon phase to be quickly processed for removal of the dissolved nitric acid, NO, etc. These dissolved materials lead to undesired side reactions. The organic phase generally contains some unreacted hydrocarbons in addition to the nitrated product. 

Control Room. The control room location can be critical to the efficient operation of a faciHty. One prime concern is to locate it the maximum distance from the most ha2ardous units. These units are usually the units where LPG or other flammables, eg, hydrocarbons that are heavier than air, can be released and accumulate at grade level. Deadly explosions can occur if a pump seal on a light-ends system fails and the heavier-than-air hydrocarbons coUect and are ignited by a flammable source. Also, the sulfur recovery unit area should be kept at a healthy distance away as an upset can cause deadly fumes to accumulate. 

A central location where instmment leads are short is preferred. In modem faciHties with distributed control systems, all units are controUed from a central control room with few operators. Only a few roving operators are available to spot trouble. It is desirable to deep process equipment a minimum of 8 m away from the control room. Any equipment and hydrocarbon-containing equipment should be separated by at least 15 m if possible. Most control rooms are designed with blastproof constmction and have emergency backup power and air conditioning. The room is pressuri2ed to prevent infusion of outside air that may have hydrocarbon content in the explosive range. 

The regulation Hsts 137 toxic and reactive substances and a threshold quantity for each. The regulation also appHes to flammable Hquids and gases in quantities of 10,000 lb or more (>4.5 metric tons), except hydrocarbon fuels and Hquids stored in unpressuri2ed, ambient temperature tanks, as weU as to the manufacture of any quantities of explosives (see Exlosives and propellants) and pyrotechnics (qv). 

Propylene is a colorless gas under normal conditions, has anesthetic properties at high concentrations, and can cause asphyxiation. It does not irritate the eyes and its odor is characteristic of olefins. Propjiene is a flammable gas under normal atmospheric conditions. Vapor-cloud formation from Hquid or vapor leaks is the main ha2ard that can lead to explosion. The autoignition temperature is 731 K in air and 696 K in oxygen (80). Evaporation of Hquid propylene can cause skin bums. Propylene also reacts vigorously with oxidising materials. Under unusual conditions, eg, 96.8 MPa (995 atm) and 600 K, it explodes. It reacts violentiy with NO2, N2O4, and N2O (81). Explosions have been reported when Hquid propylene contacts water at 315—348 K (82). Table 8 shows the ratio TJTp where is the initial water temperature, and T is the superheat limit temperature of the hydrocarbon. 

Mixing cellulose esters in nonpolar hydrocarbons, such as toluene or xylene, may result in static electricity buildup that can cause a flash fire or explosion. When adding cellulose esters to any flammable Hquid, an inert gas atmosphere should be maintained within the vessel (132). This risk may be reduced by the use of conductive solvents in combination with the hydrocarbon or by use of an antistatic additive. Protective clothing and devices should be provided. 

Fig. 2. Slow oxidation, spontaneous ignition, and explosion as a function of pressure and temperature variations in hydrocarbon mixtures (1).

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