Production of coke

Volatile constituents of the coal – including water, coal-gas, and coal-tar – are driven off by baking in an airless furnace or oven (kiln) at temperatures as high as 2,000 °C (3,600 °F) but usually around 1000 – 1100 °C (1832 – 2012 °F).

This fuses together the fixed carbon and residual (остаточный) ash. Most modern facilities have "by-product" coking ovens. Today, the volatile hydrocarbons are mainly used, after purification, in a separate combustion process to generate energy. Non by-product coking furnaces or coke furnaces (ovens) burn the hydrocarbon gases produced by the coke-making process to drive the carbonization process.

Bituminous coal must meet a set of criteria for use as coking coal, determined by particular coal assay techniques (методы химического анализа структуры). These include moisture content, ash content, sulfur content, volatile content, tar, and plasticity. This blending is targeted at producing a coke of appropriate strength (generally measured by coke strength after reaction (CSR), while losing an appropriate amount of mass. Other blending considerations include ensuring the coke doesn't swell too much during production and destroy the coke oven through excessive wall pressures.

1. The greater the volatile matter in coal, the more by-product can be produced. It is generally considered that levels of 26-29% of volatile matter in the coal blend are good for coking purposes. Thus different types of coal are proportionally blended to reach acceptable levels of volatility before the coking process begins.

Natural coke is formed when a coal seam is intersected by a volcanic intrusion. These intrusions heat the surrounding coal in an anoxic atmosphere producing coke in a zone (usually several meters) around the intrusion. However, the coke is of wildly varying strength and ash content and is generally considered unsalable except in some cases as a thermal product. As it has lost its volatile matter, it has lost the ability to be coked again.

The "hearth" process of coke-making, using lump coal (кусковой уголь), was akin to that of charcoal-burning; instead of a heap of prepared wood, covered with twigs, leaves and earth, there was a heap of coals, covered with coke dust. The hearth 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 the invention of the hot blast in iron-smelting (плавление чугуна) and the introduction of the beehive coke oven. The use of a blast of hot air, instead of cold air, in the smelting furnace was first introduced by Neilson in Scotland in the year 1828. The hearth process of making coke from coal is a very lengthy process.

Beehive coke oven is a fire brick chamber shaped like a dome is used, commonly known as a beehive oven. It is typically between 4 meters wide and 2.5 meters high. The roof has a hole for charging the coal or other kindling from the top. The discharging hole (выпускное, разгрузочное отверстие) is provided in the circumference of the lower part of the wall. In a coke oven battery, a number of ovens are built in a row with common walls between neighboring ovens. A battery consisted of a great many ovens, sometimes hundreds of ovens, in a row.

Coal is introduced from the top to produce an even layer of about 60 to 90 centimeters deep. Air is supplied initially to ignite the coal. Carbonization starts and produces volatile matter, which burns inside the partially closed side door. Carbonization proceeds from top to bottom and is completed in two to three days. Heat is supplied by the burning volatile 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 discharged, 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 conglomeration of the removed impurities. Since it was not the desired coke product, slag was initially nothing more than an unwanted by-product and was discarded. Later, however, it was found to have many beneficial uses and has since been used as an ingredient in brick-making, mixed cement, granule-covered shingles, and even as a fertilizer.

type of coke-making	processes
natural
by-product coke making
"hearth" process

Task 5. Translate from Russian to English

Наиболее важные свойства кокса – это наличие серы и золы. Кокс с меньшим содержанием этих компонентов высоко ценится на рынке. Еще один важный показатель – индекс дробления (test crush index), который означает (convey) прочность кокса во время транспортировке в домны (blast furnace). Нельзя позволять хорошо дробящемуся коксу быть в домнах, т.к. он затруднит передвижение газа сквозь загрузку железа и кокса. Индекс прочности кокса после реакции (Coke Strength after Reaction (CSR)) означает способность кокса противостоять суровым условиям (violent conditions) внутри домен до превращения в тонкие частицы (fine particles).

К концу процесса коксования содержание воды в коксе практически рано нулю. Пористая структура кокса поглощает некоторое количество воды, обычно 3-6%, от его массы. На современных предприятиях используется передовые способы охлаждения кокса с использованием гашения воздухом вместо воды.

http://www.flatheadmemo.com/north_fork_coal/Coal/News/coke.html

Task 6. Read the text and say what coke can be used for

Coke is used as a fuel and as a reducing agent in smelting iron ore in a blast furnace. The carbon monoxide produced by its combustion reduces iron oxide (hematite) in the production of the iron product.

Since smoke-producing constituents are driven off during the coking of coal, coke forms a desirable fuel for stoves and furnaces in which conditions are not suitable for the complete burning of bituminous coal itself. Coke may be combusted producing little or no smoke, while bituminous coal would produce much smoke.

Discovered by accident to have superior heat shielding properties when combined with other materials, coke was one of the materials used in the heat shielding on NASA's Apollo program space vehicles. In its final form, this material was called AVCOAT 5026-39. This material has been used most recently as the heat shielding on the Mars Pathfinder vehicle. Although not used for modern day space shuttles, NASA had been planning to utilize coke and other materials for the heat shield for its next generation space craft, named Orion, before that project's cancellation.

Coke was widely used as a substitute for coal in domestic heating following the creation of smokeless zones in the United Kingdom.

Highland Park distillery in Orkney roasted malt barley for use in their Scotch whisky in kilns burning a mixture of coke and peat.

Coke may also be used to make synthesis gas, a mixture of carbon monoxide and hydrogen.

Task 7. Listen to the lecture on coke-making and write out all the problems mentioned

coke-making lecture http://www.youtube.com/watch?v=zrVFkmEsYNg