Phosgen Cylinder
Phosgene (carbon dioxide dichloride, carbon oxychloride, carbonyl chloride) is a colourless, extremely toxic and suffocating gas with a smell of musty hay (the chemical formula is COCl2). It is about 3.5 times heavier than air and accumulates in low places. It is well soluble in glacial acetic acid, toluene, chloroform, benzene, alcohol and other organic solvents. At temperatures above 200°C it decomposes into chlorine and carbon monoxide. Phosgene is liquefied at room temperature under pressure, or at a temperature of +8.2°C, converting to a colorless liquid, and freezes at a temperature of -118.0°C. The industrial method of producing phosgene is based on heating carbon monoxide and chlorine in the presence of coal. In laboratory conditions, it is obtained by oxidation of chloroform with oxygen under the influence of light or by mild heating of a mixture of freon-10 and sulphuric anhydride. Phosgene is also formed in the combustion of some chlorine-containing freons.
APPLICATION:< / strong>< / strong>< / p>< / p> • in organic synthesis for the production of polycarbonates, production of urea and its derivatives, production of various dyes; • in the isolation of anhydrous metal chlorides; • as a raw material for the production of some medications, pesticides and solvents. Requirements for transportation, storage and use of cylinders for liquid phosgene are established by the Federal standards and regulations in the field of industrial safety "Regulations of industrial safety for hazardous facilities using equipment operating under excessive pressure", fire safety standards, as well as other laws and regulations and international agreements in force on the territory of the Russian Federation.
Cylinders are not hazardous cargo until they are taken into use, but in any case they should be transported in conditions that exclude mechanical damage. Cylinders with liquid phosgene shall be transported by rail, water and road (in exceptional cases, by air) in accordance with the cargo carriage regulations applicable to the given mode of transport. Cylinders with liquid phosgene should be transported in an upright position in special crates. Cylinders may be transported in a horizontal position with a stack height of not more than half the height of the wagon wall or side wall of the car body. All cylinders must be stacked with their caps (valves) facing the same direction and have gaskets between the cylinders. Cylinders may be transported in railroad cars without crates in an upright position if they are equipped with safety rings and if the railroad cars are loaded tightly so that they cannot move (fall). When transporting cylinders with liquid phosgene by road, the speed of the vehicle is set in accordance with the prescribing traffic signs and specific road conditions, but not more than 60 km/h. When transporting small-volume cylinders with phosgene, they must be packed in wooden crates, the weight of the cargo in each crate must not exceed 65 kg. Crates of two or more cargo places are transported by rail in unit-load devices on pallets. Cylinders must be transported with plugs on the fittings and caps screwed on.
Cylinders designed for storage and transportation of liquid phosgene must not be used for storage and transportation of other gases, and it is prohibited to perform any operations that may contaminate their internal surface and degrade the physical and chemical properties of the gas. It is forbidden to make any modifications to the cylinder bodies using welding or mechanical tools, which can lead to damage to the integrity or appearance of defects that degrade the technical characteristics of the cylinders. When using cylinders for liquid phosgene it is not allowed to install them in the places of people passage, movement of goods and passage of vehicles. Cylinders designed for storage and transportation of liquid phosgene are filled at the rate of 1.25 kg of gas per 1 dm3 of the cylinder capacity. The maximum permissible concentration of phosgene in the air of the working area of production facilities is 0.5 mg/m3. Individual perception threshold is 4.4 mg/m3. A concentration of 5 mg/m3 at an exposure time of 10 minutes is considered minimal hazardous. In 50 % of cases, inhalation of 100 mg/m3 for one hour, 300 mg/m3 for 15 minutes, 400 mg/m3 for 5 minutes and 5000 mg/m3 for 2-3 seconds will cause death. Work with phosgene must be carried out with the use of personal protective equipment against chemical factors of the skin, eyes and respiratory organs. It is not allowed to work with phosgene without personal protective equipment. For respiratory protection against gaseous phosgene vapors, industrial filter masks of B or BKF brand are used if the volume fraction of phosgene in the air does not exceed 0.5 % and the volume fraction of oxygen is at least 18 %. Oxygen breathing apparatuses such as KIP-8, RVL-1, IP-4 or ADI-GS, ASV-2 must be used for concentrations higher than those specified. Gaseous phosgene withdrawal from the cylinder (without a siphon) should be carried out with a vertical or inclined position of the cylinder, in which case the valve is in the upper position (the angle of inclination is not more than 15°). Liquid phosgene withdrawal is carried out at an inclined position of the cylinder - valve downwards. The withdrawal of liquid phosgene from cylinders should be carried out by the phosgene's own chlorine pressure. When filling cylinders with phosgene, the mass of gas in the filled cylinder should not exceed 1,250 kg per 1 dm3 of the cylinder capacity. The residual pressure in the emptied cylinder must be at least 0.05 MPa (0.5 kgf/cm2).
Cylinders filled with liquid phosgene are stored in special warehouses in freestanding aboveground or semi-underground buildings. Warehouses of liquid phosgene must be located in lower locations in relation to other nearby buildings and structures and predominantly on the leeward side of the prevailing wind directions relative to the location of the nearest settlements. The placement of cylinders with liquid phosgene in the warehouse must exclude the possibility of their falling or moving and provide free access to the shut-off valves (valves in horizontal storage should be located in the direction of the passageway). When stacked horizontally, phosgene cylinders are placed in one row near the walls and in two rows in the passageways. The height of the stack should not exceed five tiers. Cylinders may be stored on racks, but the top row of cylinders should not be higher than 1.5 m from floor level. When laying vertically, no more than two rows of cylinders should be placed at the walls; there should be four in the passageways. Cylinders should be stored with plugs on the fittings and caps screwed on.