Clinker is a generic name given to waste from industrial processes, particularly those that involve

smelting Smelting is a process of applying heat and a chemical reducing agent to an ore to extract a desired base metal product. It is a form of extractive metallurgy that is used to obtain many metals such as iron-making, iron, copper extraction, copper ...

metals,

welding Welding is a fabrication (metal), fabrication process that joins materials, usually metals or thermoplastics, primarily by using high temperature to melting, melt the parts together and allow them to cool, causing Fusion welding, fusion. Co ...

, burning fossil fuels and use of a

blacksmith A blacksmith is a metalsmith who creates objects primarily from wrought iron or steel, but sometimes from #Other metals, other metals, by forging the metal, using tools to hammer, bend, and cut (cf. tinsmith). Blacksmiths produce objects such ...

's forge, which commonly causes a large buildup of clinker around the tuyere. Clinker often forms a loose, dark deposit consisting of waste materials such as coke,

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...

, slag, charcoal, and grit. Clinker often has a glassy look to it, usually because of the formation of molten

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...

compounds during processing. Clinker generally is much denser than coke, and, unlike coke, generally contains too little carbon to be of any value as fuel. It is also applied to the byproduct of combustion and heating by those who use anthracite or lignite coal-fired

boiler A boiler is a closed vessel in which fluid (generally water) is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, centra ...

s. Clinkers can occur naturally, for example in underground deposits of coal that have been altered by heat from coal-seam fires and nearby molten

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

; volcanic clinkers are jagged pieces of

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

that look similar to industrial clinker.

Etymology

"Clinker" is from Dutch, and was originally used in English to describe clinker bricks. The term was later applied to hard residue, due to its similar appearance.

Uses

Clinker often is reused as a cheap material for paving

footpath A footpath (also pedestrian way, walking trail, nature trail) is a type of thoroughfare that is intended for use only by pedestrians and not other forms of traffic such as Motor vehicle, motorized vehicles, bicycles and horseback, horses. They ...

s. It is laid and rolled, and forms a hard path with a rough surface that presents less risk of slipping than most loose materials. In sufficient thickness such a layer drains well and is valuable for controlling muddiness. However, if laid without sufficient adhesive, it needs frequent rolling and addition of more clinker to maintain the path in good condition if it is subject to heavy foot traffic. In

sewage treatment Sewage treatment is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable to discharge to the surrounding environment or an intended reuse application, thereby preventing water p ...

works, the foul water is first screened to remove floating debris. Then it is sedimented to remove insoluble particles. After this, it is sprayed over a filter bed of clinker. Aerobic microbes soon grow in hollows in the clinker, where they kill harmful anaerobic bacteria in the water and remove much of the offensive organic waste. Historically, clinker from coal-burning

steamship A steamship, often referred to as a steamer, is a type of steam-powered vessel, typically ocean-faring and seaworthy, that is propelled by one or more steam engines that typically move (turn) propellers or paddlewheels. The first steamships ...

s simply was discarded overboard, leaving detectable trails on the

seabed The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as seabeds. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

of some prominent steamship routes. As such, the deposits have proven to be of biological, historical and archaeological interest. Naturally occurring clinkers exist. For example, in the Powder River Basin is covered by clinkers from coal-seam fires, ''i.e.'', "baked, welded and molded rocks formed by the natural burning of coal beds."

References

{{DEFAULTSORT:Clinker (Waste) Metallurgical by-products Waste

Etymology

Uses

See also

References