Heyl & Patterson Blog

The Roles of Coal and Coke in Steelmaking

Posted by H&P Blog on Wed, Jul 16, 2014 @ 09:30 AM

Steel MillSince 1875, the United States has been one of the world's main steel producers.  Steel has been an important factor in the American economy for over 100 years, providing jobs to many generations of American families, and it continues to be a booming industry today.  Production of steel takes place in two different ways.  One method uses integrated smelting involving a blast furnace, followed by a basic oxygen furnace, and the other involves an electric arc furnace.

Steel production is dependent upon coal and coke in steelmaking.  Metallurgical coke, or met coke, is manufactured from blends of bituminous coal in a heated distillation process resulting in a non-melting carbon.  Coke is made by one of two processes: by-product or non-recovery, also known as heat recovery.

In by-product coke making, impurities are driven off the coal in order to leave nearly pure carbon.  This is done by heating the coal at about 1800-3600 degrees Fahrenheit in large slot ovens which are connected by a shared heat source.  The ovens are devoid of any oxygen in order to drive off other compounds and leave a purer form of coal.  When the coal is "coked", it softens and turns into a liquid.  When the coked coal resolidifies, it becomes a small and porous lump that is cooled in either air or water.  The gases that are produced in the coking process are sent off to a by-product plant, where they are collected for reuse.  It is for this reason that the process is called "by-product" coke making.  After the coke has cooled, it is ready to go to the blast furnace or it can be stored and shipped to steel mills. 

In non-recovery or heat recovery coke making, ovens are stacked in a "beehive" form.  The ovens are heated from the top, and air is fed through the bottom for combustion through chambers located in the oven wall.  The waste gases are not sent to recovery plants, so this process is known as "non-recovery" coke making.  In other instances, the excess heat and gas are sent through a waste recovery boiler where the heat and gas is converted to steam in order to create power.  This type of coke making is then called "heat recovery" coke making.

Once in the blast furnace, the quality of the coke comes into play.  Iron is combined with steel and flux.  The coke plays a main role in driving off the impurities of the steel when it is being created within the blast furnace.  The steel, flux and iron melts in the oven and impurities are driven off, resulting in liquid steel.  Higher quality coke results in higher quality steel. 

Rotary Coal DumperAnother well-known process of steel making is completed with an electric arc furnace.  Unlike a blast furnace, an electric arc furnace uses no iron in steel making.  Coke and coal are not required during this process, as it uses electricity instead.

Coke is often produced away from the steel mills, and is often delivered via railway.  It is the job of rotary railcar dumpers made by Heyl & Patterson to get the coke quickly and safely out of the car and deposited at the steel mill.  Railcar dumpers tip an entire car upside down in order to dump out all of its contents.

Coke is sometimes considered to be a "dirty cargo" by many companies, which is anything comprised of crude oil or any type of heavy, viscous petroleum products.  Any type of cargo known to stick to the interior of railcars and other types of shipping containers is known as "dirty."  Although coke is not a viscous or heavy petroleum product, it is a chore to remove from surfaces.  As a result, railcars that carry coke are destined to always carry coke.

For more information on Heyl & Patterson equipment for the transfer of coked coal and other materials from rail, click here:

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Tags: coal handling, coke, railcar dumpers