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Wednesday April 23rd 2014


Industrial Gases

Industrial Gases

While the gases that are now commonly referred to as ‘‘industrial,’’ namely oxygen, hydrogen, carbon dioxide, and nitrogen, were not fully understood until the nineteenth century, scientists in the twentieth century moved rapidly to utilize the knowledge. Driven largely by the demands of manufacturing industries in North America and Western Europe, rapid improvements in the technology of production and storage of industrial gases drove what has become a multibillion dolar business, valued at $34 billion in 2000. At the start of the twenty-first century, industrial gases underpin nearly every aspect of the global economy, from agriculture, welding, metal manufacturing and processing, refrigerants, enhanced oil recovery, food and beverage processing, electronic component manufacturing, to rocket propulsion. Oxygen for metal manufacturing is the largest volume market, with chemical processing and electronics using significant volumes of hydrogen and lower volumes of specialty gases such as argon. Until at least the fifteenth century, gases were thought of inclusively as ‘‘air,’’ part of the alchemical construction of the world. It was not until the seventeenth and eighteenth centuries that properties and characteristics unique to individual gases were recognized. Once one gas was finally isolated, a cavalcade of similar discoveries followed. In 1754, for example, English aristocrat and chemist Henry Cavendish ‘‘discovered’’ hydrogen, in 1756 English chemist Joseph Black discovered that carbon dioxide was a constituent of carbonate rocks, in 1772 Swede Carl Wilhelm Scheele discovered oxygen’s properties, Englishman Joseph Priestley isolated oxygen (which he called dephlogisticated air) by 1774, and by 1784, Frenchman Antoine Laurent Lavoisier came up with a method of decomposing water into constituent elements, which he named hydrogen and oxygen, by passing water vapor over hot charcoal. Lavoisier was one of the first quantitative chemists, and showed that water was composed of two-thirds hydrogen and one-third oxygen. These earliest discoveries highlighted the challenges ahead for harnessing the benefits of these gases: how to isolate and store them. Hydrogen, known for its ‘‘lighter than air’’ qualities as early as 1774, was first extracted from water using electrolysis by William Nicholson and Anthony Carlisle in 1800, but the high cost of electricity proved to make this an expensive method. As demand increased for hydrogen’s use in airships, from zeppelins to military observation balloons in the 1930s, more economic means of extraction appeared. Since the 1920s, hydrogen has been produced by liquefaction of natural gas, partial oxidation of heavy oil, or gasification of coal. Oxygen was first used in medicine (as an anesthetic or ventilator) and for ‘‘limelight,’’ a theatrical lighting method from burning oxygen and hydrogen together. Early oxygen-using equipment could function with low-purity oxygen in small amounts, acquired by using several different chemical and heating processes that would break the oxygen into molecules, which was then compressed and sold in cylinders. By 1902, a system of rectifying ‘‘liquid air’’ pioneered by German Carl von Linde produced oxygen up to 99 percent pure. In the early nineteenth century, nitrogen fertilizers were obtained from discoveries of immense bat guano deposits and caliche (nitrate-bearing rocks) in South America. As threats of famine loomed at the close of the nineteenth century, the need for agricultural fertilizers drove early production of nitrogen from the atmosphere. While ‘‘liquid air’’ contained nitrogen, it was difficult to separate from oxygen. Three solutions were developed in Europe: the cyanamide process (c.1900), which involved passing steam over certain carbides to form calcium cyanamide; the electric arc process (c.1903), which imitated lightning discharges to isolate nitrogen from air; and the Haber process, created by German Fritz Haber in 1904 and later developed into an industrial process by Carl Bosch, in which nitrogen is reacted with hydrogen to form ammonia. By the twentieth century, carbon dioxide was extracted from many natural sources, especially cracks in the earth’s crust due to volcanic activity, and as a byproduct of limekiln operations and synthetic ammonia production. Carbonic acid was used in bottled soft drinks, cooling, and in dry ice. Combined with sodium bicarbonate and ammonium sulfate it also created a foam, which deployed from a pressurized canister, became the fire extinguisher (carbon dioxide will not support combustion, and foam application ensures the gas does not quickly disperse).

Acetylene, discovered in 1836 and used in home and street lighting, was not produced industrially from calcium carbide until 1892. In 1901 Charles Picard and Edmond Fouche´ separately invented the oxyacetylene lamp, now widely used in arc welding, by combining acetylene with oxygen to produce an intense heat. Argon was used as an inert gas for electric lights, neon was used in lighted signs by 1913, and helium was used in balloons, dirigibles, welding, and medicine, and also mixed with oxygen for compression into cylinders for divers (the first practical compressed air diving apparatus was produced in 1925). After World War II, applications for industrial gases expanded, using combinations of the basic four with lesser-known gases, as with the oxyacetylene lamp. Because acetylene was highly volatile in its compressed (and saleable) form, several innovations in transportation of the gas became necessary, with acetylene transported in pressurized steel cylinders.

However it was the liquefaction of gases— bringing a gas to a liquid state by intense pressure followed by cooling expansion—that was critical to the transport and application of these gases. Building on compression technology invented in the late nineteenth century, the science of cryogenics was the major contribution to liquefying gases. The method of cryogenic separation or distillation developed by German Carl von Linde in 1895 for liquefied air, involved dropping the temperature of the air to below –140_C and increasing pressure to eight to ten times that of the atmosphere. As the liquid air is boiled, gases are boiled off at different boiling temperatures: vaporized nitrogen first, then argon, then oxygen. By 1908, all the gases had been separated using several different cryogenic machines, leading to a boost in the availability of these liquid gases, and increasing demand as subsequent uses for the gases developed. In the post-World War II years, oxygen was produced in large quantities, thanks to the Linde–Frankl process for liquefying air (developed in 1928–1929), which ultimately gave way in the 1960s to the molecular sieve or pressure swing adsorption—a method that removes carbon dioxide from air. The abundance of oxygen also contributed to great advances in medicine—namely anesthesia and respiratory support, as well as facilitating high-altitude flying.

The growth of industrial use of oxygen and acetylene meant that pressure vessels were needed for transportation and storage. One of the earliest storage devices for liquefied gas was a doublewalled vessel with a vacuum in the annular space, known as the ‘‘Dewar flask,’’ invented by Sir James Dewar in 1892. Building on this early technology, ultrahigh vacuum pumps, as well as aluminum and foil matting used as insulation, contributed to advances in the storage and transport of highly pressured gases. In 1930, the first vacuum-insulated trains and trucks carried refrigerated, liquefied gases in the U.S., and by the 1950s, pipelines carried gas—with the largest in France—transporting oxygen, nitrogen and hydrogen from several different plants. The first generation of compressed gas cylinders (1902–1930) used carbon steel cylinders. Problems with rupturing led to the development of quenched and tempered alloy steel cylinders. By the 1960s, oxygen was being used by steel manufacturers to enhance combustion in furnaces, and by the 1970s, nitrogen was widely employed as inert packaging for food preservation, as well as freeze-drying of food and heat treatment of metals. By the 1960s liquid hydrogen was used in rocket fuel and as a coolant for superconductors. By the 1980s, semiconductors were big customers for bulk industrial gases such as oxygen, argon, and hydrogen used as carrier gases for epitaxial growth, with specialist applications demanding higher quality gas (for example high-purity silane as a dopant, chlorine as an etchant). Cryosurgery using liquid nitrogen contributed to advances in medicine, including fertility treatments with frozen embryos, blood bank storage, and organ transplantation. Industries from the automotive industry to steel making rely heavily on industrial gases. Hydrogen is used to cool alternators in power plants, and high-pressure cylinder gases are used in hospitals, small welding businesses, and in fire extinguishers. Liquefied carbon dioxide is used for dry cleaning textiles and as an industrial solvent, for example degreasing machine parts, coffee and tea decaffei- nation, and extracting essential oils and medicinal compounds from plants. While cryogenic distillation is still the favored form of production for industrial gases, some industries have shifted to less expensive noncryogenic methods. Pressure swing adsorption, for example, pumps pressurized air into either a molecular sieve, or an adsorptive agent, which removes the ‘‘unwanted’’ gas from the air stream, leaving the desired gas behind (for example, removing carbon dioxide from air). While the end product is not as pure as cryogenic products, engineers are perfecting the method. Noncryogenic separation techniques such as pressure swing adsorption have made on-site production more affordable. On-site production, primarily of oxygen, reduces distribution costs for remote locations, and guarantees essential supply, for example for hospitals.

One of the byproducts of the expansive use of industrial gas is an increase in undesirable environmental pollutants—contributing to the ‘‘greenhouse effect’’ and an overabundance of nitrates from agriculture application. Subsequently, government controls worldwide have led the gas industry to revamp some of its distribution and application. Hydrogen is likely to be the gas of the future, employed in ‘‘green’’ fuel cell technology, and glass and steel manufacturers are reducing nitrous dioxide emissions by mixing oxygen with coal.

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