Coke

The unqualified term "coke" usually refers to the product derived from low-=
ash and low-sulphur bituminous coal by a process called coking. A similar p=
roduct called petroleum coke, or pet coke, is obtained from crude oil in oi=
l refineries. Coke may also be formed naturally by geologic processes.[1]

Historical sources dating to the 4th century describe the production of cok=
e in ancient China.[2] The Chinese first used coke for heating and cooking =
no later than the 9th century.[citation needed] By the first decades of the=
 11th century, Chinese ironworkers in the Yellow River valley began to fuel=
 their furnaces with coke, solving their fuel problem in that tree-sparse r=
egion.[3]

coke
Download https://terpturpropki.blogspot.com/?zn=3D2wJ3Pf



China is the largest producer and exporter of coke today.[4] China produces=
 60% of the world's coke. Concerns about air pollution have motivated techn=
ological changes in the coke industry by elimination of outdated coking tec=
hnologies that are not energy-efficient.[5]

In 1589, a patent was granted to Thomas Proctor and William Peterson for ma=
king iron and steel and melting lead with "earth-coal, sea-coal, turf, and =
peat". The patent contains a distinct allusion to the preparation of coal b=
y "cooking". In 1590, a patent was granted to the Dean of York to "purify p=
it-coal and free it from its offensive smell".[6] In 1620, a patent was gra=
nted to a company composed of William St. John and other knights, mentionin=
g the use of coke in smelting ores and manufacturing metals. In 1627, a pat=
ent was granted to Sir John Hacket and Octavius de Strada for a method of r=
endering sea-coal and pit-coal as useful as charcoal for burning in houses,=
 without offence by smell or smoke.[7]

In 1709, Abraham Darby I established a coke-fired blast furnace to produce =
cast iron. Coke's superior crushing strength allowed blast furnaces to beco=
me taller and larger. The ensuing availability of inexpensive iron was one =
of the factors leading to the Industrial Revolution. Before this time, iron=
-making used large quantities of charcoal, produced by burning wood. As the=
 coppicing of forests became unable to meet the demand, the substitution of=
 coke for charcoal became common in Great Britain, and coke was manufacture=
d by burning coal in heaps on the ground so that only the outer layer burne=
d, leaving the interior of the pile in a carbonized state. In the late 18th=
 century, brick beehive ovens were developed, which allowed more control ov=
er the burning process.[9]

In 1768, John Wilkinson built a more practical oven for converting coal int=
o coke.[10] Wilkinson improved the process by building the coal heaps aroun=
d a low central chimney built of loose bricks and with openings for the com=
bustion gases to enter, resulting in a higher yield of better coke. With gr=
eater skill in the firing, covering and quenching of the heaps, yields were=
 increased from about 33% to 65% by the middle of the 19th century. The Sco=
ttish iron industry expanded rapidly in the second quarter of the 19th cent=
ury, through the adoption of the hot-blast process in its coalfields.[11]

In 1802, a battery of beehive ovens was set up near Sheffield, to coke the =
Silkstone coal seam for use in crucible steel melting. By 1870, there were =
14,000 beehive ovens in operation on the West Durham coalfields, producing =
4,000,000 long tons of coke per year. As a measure of the expansion of coke=
 making, the requirements of the iron industry in Britain were about 1,000,=
000 tons per year in the early 1850s, rising to about 7,000,000 tons by 188=
0. Of these, about 5,000,000 tons were produced in Durham county, 1,000,000=
 tons in the South Wales coalfield, and 1,000,000 tons in Yorkshire and Der=
byshire.[11]

In the first years of steam locomotives, coke was the normal fuel. This res=
ulted from an early piece of environmental legislation; any proposed locomo=
tive had to "consume its own smoke".[12] This was not technically possible =
to achieve until the firebox arch came into use, but burning coke, with its=
 low smoke emissions, was considered to meet the requirement. This rule was=
 quietly dropped, and cheaper coal became the normal fuel, as railways gain=
ed acceptance among the public. The smoke plume produced by a travelling lo=
comotive seems now to be a mark of a steam railway, and so preserved for po=
sterity.

So-called "gas works" produced coke by heating coal in enclosed chambers. T=
he flammable gas that was given off was stored in gas holders, to be used d=
omestically and industrially for cooking, heating and lighting. The gas was=
 commonly known as "town gas" since underground networks of pipes ran throu=
gh most towns. It was replaced by "natural gas" (initially from the North S=
ea oil and gas fields) in the decade after 1967.[citation needed] Other byp=
roducts of coke production included tar and ammonia, while the coke was use=
d instead of coal in cooking ranges and to provide heat in domestic premise=
s before the advent of central heating.

In the US, the first use of coke in an iron furnace occurred around 1817 at=
 Isaac Meason's Plumsock puddling furnace and rolling mill in Fayette Count=
y, Pennsylvania.[13] In the late 19th century, the coalfields of western Pe=
nnsylvania provided a rich source of raw material for coking. In 1885, the =
Rochester and Pittsburgh Coal and Iron Company[14] constructed the world's =
longest string of coke ovens in Walston, Pennsylvania, with 475 ovens over =
a length of 2 km (1.25 miles). Their output reached 22,000 tons per month. =
The Minersville Coke Ovens in Huntingdon County, Pennsylvania, were listed =
on the National Register of Historic Places in 1991.[15]



Between 1870 and 1905, the number of beehive ovens in the US increased from=
 approximately 200 to nearly 31,000, which produced nearly 18,000,000 tons =
of coke in the Pittsburgh area alone.[16] One observer boasted that if load=
ed into a train, "the year's production would make up a train so long that =
the engine in front of it would go to San Francisco and come back to Connel=
lsville before the caboose had gotten started out of the Connellsville yard=
s!" The number of beehive ovens in Pittsburgh peaked in 1910 at almost 48,0=
00.[17]

Although it made a top-quality fuel, coking poisoned the surrounding landsc=
ape. After 1900, the serious environmental damage of beehive coking attract=
ed national notice, although the damage had plagued the district for decade=
s. "The smoke and gas from some ovens destroy all vegetation around the sma=
ll mining communities", noted W. J. Lauck of the U.S. Immigration Commissio=
n in 1911.[18] Passing through the region on train, University of Wisconsin=
 president Charles Van Hise saw "long rows of beehive ovens from which flam=
e is bursting and dense clouds of smoke issuing, making the sky dark. By ni=
ght the scene is rendered indescribably vivid by these numerous burning pit=
s. The beehive ovens make the entire region of coke manufacture one of dull=
ed sky: cheerless and unhealthful."[18]

Bituminous coal must meet a set of criteria for use as coking coal, determi=
ned by particular coal assay techniques. These include moisture content, as=
h content, sulphur content, volatile content, tar, and plasticity. This ble=
nding is targeted at producing a coke of appropriate strength (generally me=
asured by coke strength after reaction), while losing an appropriate amount=
 of mass. Other blending considerations include ensuring the coke doesn't s=
well too much during production and destroy the coke oven through excessive=
 wall pressures.

The "hearth" process of coke-making, using lump coal, was akin to that of c=
harcoal-burning; instead of a heap of prepared wood, covered with twigs, le=
aves and earth, there was a heap of coals, covered with coke dust. The hear=
th process continued to be used in many areas during the first half of the =
19th century, but two events greatly lessened its importance. These were th=
e invention of the hot blast in iron-smelting and the introduction of the b=
eehive coke oven. The use of a blast of hot air, instead of cold air, in th=
e smelting furnace was first introduced by Neilson in Scotland in 1828.[11]=
The hearth process of making coke from coal is a very lengthy process.[cita=
tion needed]

A fire brick chamber shaped like a dome is used, commonly known as a beehiv=
e oven. It is typically 4 meters (13.1 ft) wide and 2.5 meters (8.2 ft) hig=
h. The roof has a hole for charging the coal or other kindling from the top=
. The discharging hole is provided in the circumference of the lower part o=
f the wall. In a coke oven battery, a number of ovens are built in a row wi=
th common walls between neighboring ovens. A battery consisted of a great m=
any ovens, sometimes hundreds, in a row.[23]

Coal is introduced from the top to produce an even layer of about 60 to 90 =
centimeters (24 to 35 in) deep. Air is supplied initially to ignite the coa=
l. Carbonization starts and produces volatile matter, which burns inside th=
e partially closed side door. Carbonization proceeds from top to bottom and=
 is completed in two to three days. Heat is supplied by the burning volatil=
e matter so no by-products are recovered. The exhaust gases are allowed to =
escape to the atmosphere. The hot coke is quenched with water and discharge=
d, manually through the side door. The walls and roof retain enough heat to=
 initiate carbonization of the next charge.

When coal was burned in a coke oven, the impurities of the coal not already=
 driven off as gases accumulated to form slag, which was effectively a cong=
lomeration of the removed impurities. Since it was not the desired coke pro=
duct, slag was initially nothing more than an unwanted by-product and was d=
iscarded. Later, however, it was found to have many beneficial uses and has=
 since been used as an ingredient in brick-making, mixed cement, granule-co=
vered shingles, and even as a fertilizer.[24]

People can be exposed to coke oven emissions in the workplace by inhalation=
, skin contact, or eye contact. The Occupational Safety and Health Administ=
ration (OSHA) has set the legal limit for coke oven emissions exposure in t=
he workplace as 0.150 mg/m3 benzene-soluble fraction over an eight-hour wor=
kday. The National Institute for Occupational Safety and Health (NIOSH) has=
 set a recommended exposure limit (REL) of 0.2 mg/m3 benzene-soluble fracti=
on over an eight-hour workday.[25]
 eebf2c3492