User:TOWN GAS

TOWN GAS Town gas is a combustible and toxic mixture comprising 50% hydrogen, 20-30% methane, 7-17% carbon monoxide, 3% carbon dioxide, 8% nitrogen and 2% hydrocarbons. Furthermore, town gas contains ammonia, sulphur, hydrocyanic acid, benzene and other substances. Sulphur (inthe form of strong-smelling chemical compounds) produces the characteristic " gas smell"; indeed, somtimes the smell is deliberately added to provide a warning in the event of the escape of gas. Detoxicated gas contains little or no carbon monoxide. It is distributed to the gas is rated in terms of its colorific value, i.e., the amount of heat that is producerd when one cubic foot of gas is burned with air. The calorific value ranges from 450 to 500 B.T.U. per cubic foot. Because of its carbon monoxide content, town gas is highly poisonous, and because of its content of combustible gases it is highly explosive when mixed with air. If several cubic yards of gas are allowed to escape into a room, an explosive mixture will be formed, which can be ignited even by a tiny electric spark, such as many, for instances, be caused by a door bell or a telephone ringing. Town gas is a fuel gas. The term "coal gas" is sometimes applied to it, denoting that it is produced mostly from coal. One way to produce this gas is to heat rough coal to a temperature of 1000 degree-1200 degree C, out of contact of air, in a chamber called a retort, which may be of the inclined type. In this process, up to about 500 cu. ft. of town gas can be produced from 100lb. of dry coal with a low ash content. Whatremains of the coal after extraction of the external application of heat, but is converted into gas by partial combustion with oxygen and chemical reaction with water vapour. The crude gas produce must be carefully purified: in particular, it is necessary to remove volatile sulphur and nitrogen compounds. In many cases the "water gas" or producer gas obtained in this way is used as an admixture to coal gas (up to 40% being added). Fuel gases from oil refeneries (wich gases are produced by gasification of petroleum) or natural gas are playing an increasingly important part in town gas supply. Despite its dangerous character, town gas is unlikely to be entirely superseded by electricity in the foreseeable future. Gas will be able to hold its own because of its relatively low cost and the convencience with which it can be distributed through pipes. At the same time, the large quantities of carbon dioxide and the by no means inconsiderable quantities of sulphur dioxide, which are formed in the combustion of gas, add to the pollution of the atmosphere of our towns. (coal gas in U.S.A)source Hutchinsons