Smokeless fuels

Low Temperature Carbonization. Lower temperature carbonization of lump coal at ca 700°C, primarily used for production of soHd smokeless fuel, gives a quantitatively and quaUtatively different yield of sofld, Hquid, and gaseous products than does the high temperature processes. 

Although a number of low temperature processes have been studied, only a few have been used commercially. These have been limited in the types of coal that are acceptable, and the by-products are less valuable than those obtained from high temperature processing. The Disco process is used in the United States to supply a limited amount of fuel to meet requirements of smoke ordinances. The British CoaUte and Rexco processes produced substantial amounts of domestic smokeless fuel. Development of fluid-bed methods of carbonizing finer coal at ca 400°C has been studied in the United Kingdom. A reactive char is briquetted without a binder to produce a premium open-fire smokeless fuel. 

The production of coke involves the heating of coal in the absence of air, called the carbonization or destructive distillation of coal. Carbonization, besides its main purpose of production of coke, also results in a coproduct called coke oven gas from which various liquid products such as tar, benzol, naphthalene, phenol, and anthracene are separated. There are two main types of carbonization based on the temperature to which the coal is heated in the absence of air. One type is low-temperature carbonization (LTC) the other is high-temperature carbonisation (HTC). Some features of LTC and HTC are listed in Table 1.28. The LTC Process is mainly carried out to manufacture domestic smokeless fuel. This presentation, however, concentrates on the HTC process by which metallurgical coke is produced. 

Anthracite. Anthracite is a hard, black, shiny form of coal that contains virtually no moisture and very low volatile content. Because of this, it bums with little or no smoke and is sold as a "smokeless fuel. In general, coals only approach anthracite composition where bituminous coal seams have been compressed further by local crustal movements. Anthracites can have energy contents up to about 32 MJ/kg, depending on the ash content. 

BC Earliest known use of carbon is by the Egyptians. Charcoal was used to make bronze and as a smokeless fuel for home fires. 

Devolatilized fuel smokeless fuel coke that has been reheated to remove all of the volatile material. 

Charcoal was a valued commodity in antiquity. The ancient Egyptians used the volatile product of hardwood distillation, pyroligneous acid, for embalming. Before synthetic organic chemistry became well established, destructive hardwood distillation provided several important industrial chemicals, among these were acetone, acetic acid, and methanol (still often referred to as wood alcohol). Charcoal is a fine, smokeless fuel, prized for its smokeless nature and used extensively for outdoor cooking. Acetone was originally made by the dry distillation of calcium acetate made from wood-derived acetic acid, but better, cheaper sources are also available. 

Coal pyrolysis is a very old technique (dating back to the eighteenth century), based on relatively inelegant technology. Most pyrolysis systems in use in the late 1800s and early 1900s were in Europe and had as their objective the production of smokeless fuel (char) for domestic use. However, within a short time it was realized that the coal tar fraction contained valuable chemical products. However, as inexpensive petroleum appeared on the scene, interest in coal byproducts faded. A detailed review has been published.29... 

Staatsmijnen-Otto Also known as the Pieters process, after the inventor, H.A.J. Pieters. A process for removing hydrogen sulfide from coal gas by scrubbing with an aqueous solution containing a suspension of iron cyanide complexes known as iron blue. The product is elemental sulfur, which separates as a froth and is purified by heating with water in an autoclave. Staatsmijnen is a Dutch producer of smokeless fuels, which has also given its name to a briquetting process. 

Processes subject to Integrated Pollution Control, Chief inspectors guidance Note Series 2 (S2), Fuel production and Combustion Sector. S2 1.07 Carbonisation and Associated Processes Smokeless Fuel, Activated Carbon and Carbon Black Manufacture, London HMSO, September 1995, ISBN 0-11-753177-4, UK. 

On an average high-temperature coke oven tar contains 0.4-0.6% phenol, 0.8-1% cresols, 0.2-0.5% xylenols. In the United Kingdom, cresols have been traditionally produced from low-temperature coal tars obtained in the production of smokeless fuels. The key player has been Coalite Chemicals. Similarly, in Germany Rutgers VFT AG has developed excellence in coal tar chemistry and has been producing cresylic acids and 3,5-xylenols for years. CdF Chimie in... 

W. Pietsch, Briquetting of coal (Can an ancient technology be modified for the production of environmentally safer smokeless fuels ). Proc. 21st Biennial Conf of IBA, New Orleans, LA (1989), 303-320. 

New Applications of Roller Presses Charcoal, Smokeless Fuel, Formed Coke, Coal-Based Solid Compliance Fuels... 

Smokeless fuel was expected to become again a consumer product with all its new requirements, especially excellent physical quality and pleasing appearance. The latter motivated one producer in the UK to dip the briquettes into a special gold bronze die during curing to eliminate the dirty black coal look . 

Mixing different raw materials, additives, and binders, agglomerating the blend, and subjecting the product to different post-treatment methods to achieve special properties is known as material engineering. Industrial wastes can be included in such raw materials and additives can produce, for example, a fluxed feed for metallurgical operations, secondary raw materials with predetermined alloying ingredients, or smokeless fuels (Sections 6.8, 6.9, and 6.10). 

In many parts of the world, considerable success has been achieved in the abatement of atmospheric pollution. Action taken in the UK provides a good example. In the 1950s, cities were badly polluted with smoke from coal burnt on open domestic fires. It was customary to burn soft, bituminous coal and in winter the air became heavy with aromatic hydrocarbons and soot particles. This led to pernicious smogs (smoke-laden fogs) and many elderly people died from chest infections. In 1956, the Clean Air Act banned the burning of soft coal on open fires smokeless fuel e.g., anthracite) and closed stoves were introduced. This, together with widespread use of gas for fires and central heating, had a dramatic remedial effect on urban air quality. 

Carbonization is the destructive distillation of organic substances in the absence of air accompanied by the production of carbon and liquid and gaseous products. The coke produced by carbonization of coal is used in the iron and steel industry and as a domestic smokeless fuel. 

Char from the low-temperature (ca. 650°C [1200°F]) carbonization of coal is not a widely used material at the present time mainly because the production of chemical raw materials and smokeless fuel (char) was rendered somewhat uneconomical by the development of the petrochemical industry. 

The production of smokeless fuel briquettes, both for domestic and industrial use, from bituminous coal using a binder is an old art and there are several commercial processes available (Franke, 1930 Haake and Meyer, 1930 Rhys Jones, 1963 Schinzel, 1981 Perlack et al., 1986). But the increasing use of petroleum, gas, and electricity for heating purposes and the reduction in the number of individual heating plants have caused a reduction in the use of coal briquettes. In spite of this, and contradictory as it may seem, the increased use of petroleum has been of some value to the briquetting industry. During the last 20 years the intense competition from petroleum products, as well as an increase in demand by consumers for briquette quality, led to automation of the production of briquettes and a continuous improvement in quality. 

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