Carbon dioxide explosion

Supercritical CO2 is used for carbon dioxide explosion pretreatment. CO2 is cheap, nontoxic, inflammable, and easy to extract after explosion (Taherzadeh and Karimi, 2008). Due to the release of carbon dioxide at high pressure, lignocelluloses are disturbed, which increases the surface area for further hydrolysis. Glucose release was observed to increase with increasing pressure and temperature of the carbon dioxide was applied in supercritical carbon dioxide explosion. However, using subcritical carbon dioxide results in opposite scenario. 

Carbon dioxide explosion is a pre-treatment process that uses supercritical carbon dioxide to break down the biomass structure. In aqueous solution, carbon dioxide forms carbonic acid which depolymerizes lignocellulosic materials. As a small molecule, carbon dioxide can penetrate into the pores of the biomass better than ammonia. When carbon dioxide explodes due to the change of pressure, it breaks the cellulosic structure. This process is usually operated under high pressure but low temperature to prevent monosaccharide degradation. But in comparison to steam explosion and ammonia explosion processes, the sugar recovery yield from this process is... 

Dong, M. and Walker, T.H. 2008. Characterization of high-pressure carbon dioxide explosion to enhance oil extraction from canola, J. Supercrit. Fluids 44 193-200. 

Zheng, Y.Z., Lin, H.M., Tsao, G.T., 1998. Pretreatment for cellulose hydrolysis by carbon dioxide explosion. Biotechnology Progress 14, 890—896. 

C2H3N. Colourless liquid with strong ammoniacal smell b.p. 56 C. Miscible with water and strongly basic. Prepared commercially from 2-aminoelhanol. Pure dry aziridine is comparatively stable but it polymerizes explosively in the presence of traces of water. Carbon dioxide is sufficiently acidic to promote polymerization. 

The chief danger and main source of error in a combustion is that of moving the Bunsen forward a little too rapidly and so causing much of the substance to burn very rapidly, so that a flash-back occurs. This usually causes an explosion wave to travel back along the tube towards the purification train, some carbon dioxide and water vapour being carried with it. If these reach the packing of the purification train they will, of course, be absorbed there and the results of the estimation will necessarily be low. 

Flash points and autoignition temperatures are given in Table 11. The vapor can travel along the ground to an ignition source. In the event of fire, foam, carbon dioxide, and dry chemical are preferred extinguishers. The lower and upper explosion limits are 1% and 7%. 

Tetrafluoroethylene undergoes addition reactions typical of an olefin. It bums in air to form carbon tetrafluoride, carbonyl fluoride, and carbon dioxide (24). Under controlled conditions, oxygenation produces an epoxide (25) or an explosive polymeric peroxide (24). Trifluorovinyl ethers,... 

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). 

Isophthahc acid dust forms explosive mixtures with air at certain concentrations. These concentrations and other information on burning and explosiveness of isophthahc acid dust clouds are given in Table 27 (40,41). Fires can be extinguished with dry chemical, carbon dioxide, water or water fog, or foam. 

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). 

At room temperature, Htde reaction occurs between carbon dioxide and sodium, but burning sodium reacts vigorously. Under controUed conditions, sodium formate or oxalate may be obtained (8,16). On impact, sodium is reported to react explosively with soHd carbon dioxide. In addition to the carbide-forrning reaction, carbon monoxide reacts with sodium at 250—340°C to yield sodium carbonyl, (NaCO) (39,40). Above 1100°C, the temperature of the DeviHe process, carbon monoxide and sodium do not react. Sodium reacts with nitrous oxide to form sodium oxide and bums in nitric oxide to form a mixture of nitrite and hyponitrite. At low temperature, Hquid nitrogen pentoxide reacts with sodium to produce nitrogen dioxide and sodium nitrate. 

Gas AntisolventRecrystallizations. A limitation to the RESS process can be the low solubihty in the supercritical fluid. This is especially evident in polymer—supercritical fluid systems. In a novel process, sometimes termed gas antisolvent (GAS), a compressed fluid such as CO2 can be rapidly added to a solution of a crystalline soHd dissolved in an organic solvent (114). Carbon dioxide and most organic solvents exhibit full miscibility, whereas in this case the soHd solutes had limited solubihty in CO2. Thus, CO2 acts as an antisolvent to precipitate soHd crystals. Using C02 s adjustable solvent strength, the particle size and size distribution of final crystals may be finely controlled. Examples of GAS studies include the formation of monodisperse particles (<1 fiva) of a difficult-to-comminute explosive (114) recrystallization of -carotene and acetaminophen (86) salt nucleation and growth in supercritical water (115) and a study of the molecular thermodynamics of the GAS crystallization process (21). 

Butylenes are not toxic. The effect of long-term exposure is not known, hence, they should be handled with care. Reference 96 Hsts air and water pollution factors and biological effects. They are volatile and asphyxiants. Care should be taken to avoid spills because they are extremely flammable. Physical handling requires adequate ventilation to prevent high concentrations of butylenes in the air. Explosive limits in air are 1.6 to 9.7% of butylenes. Their flash points range from —80 to —73° C. Their autoignition is around 324 to 465°C (Table 2). Water and carbon dioxide extinguishers can be used in case of fire. 

In addition to chemical synthesis and enhanced oil recovery, gaseous carbon dioxide is used in the carbonated beverage industry. Carbon dioxide gas under pressure is introduced into mbber and plastic mixes, and on pressure release a foamed product is produced. Carbon dioxide and inert gas mixtures rich in carbon dioxide are used to purge and fiH industrial equipment to prevent the formation of explosive gas mixtures. 

These can be converted to their sodium salts by precipitation below 30° with aqueous 25% NaOH. The salt is then decomposed by addition of solid (powder ) carbon dioxide and extract with low-boiling petroleum ether. The solvent should be removed under reduced pressure below 20°. The manipulation should be adequately shielded at all times to guard against EXPLOSIONS for the safety of the operator. 

Vapor Density (VD) — the mass per unit volume of a given vapor/gas relative to that of air. Thus, acetaldehyde with a vapor density of 1.5 is heavier than air and will accumulate in low spots, while acetylene with a vapor density of 0.9 is lighter than air and will rise and disperse. Heavy vapors present a particular hazard because of the way they accumulate if toxic they may poison workers if nontoxic they may displace air and cause suffocation by oxygen deficiency if flammable, once presented with an ignition source, they represent a fire or explosion hazard. Gases heavier than air include carbon dioxide, chlorine, hydrogen sulfide, and sulfur dioxide. 

Extinguishing Agents Dry chemical, carbon dioxide, water fog, chemical foam Fire Extinguishing Agents Not To Be Used None Special Hazards of Combustion Products Not pertinent Behavior in Fire Vapor from molten benzoic acid may form explosive mixture with air. Concentrated dust may form explosive mixture in air Ignition Temperature (deg. F) 1,063 Electrical Hazard Not pertinent Burning Rate Not pertinent. 

Fire Hazards - Flash Point (deg. F) 350 OC Flammable Limits in Air (%) Not pertinent Fire Extinguishing Agents Water, foam, dry chemical, or carbon dioxide Fire Extinguishing Agents Not To Be Used No data Special Hazards of Combustion Products No data Behavior in Fire Dust explosion is high probability Ignition Temperature No data Electrical Hazard No data Burning Rate Not pertinent. 

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