co*ke and How it’s Made
co*ke is a fuel used in the steelmaking process that is created by heating coal in the absence of air.
Myth: The process of co*ke manufacturing is very complex and cannot be understood by anyone other than a scientist or engineer.
Reality: The manufacturing of co*ke involves a number of different processes. An understanding of these processes helps to understand the nature of the air pollution problem. These processes can be broken down and explained in simple terms.
The manufacturing of co*ke has many associated environmental and air pollution concerns. co*ke manufacturing is present throughout the Allegheny County area and impacts communities throughout the county. However, it can bedifficult to find specific information about how the co*ke processand its impacts works.
co*ke is produced by heating coal at high temperatures, for long periods of time. This heating is called “thermal distillation” or “pyrolysis.” In order to produce co*ke that will be used in blast furnaces, coal is usually thermally distilled for 15 to 18 hours, but the process can take up to 36 hours. The temperature of the ovens ranges between 900 and 1100 degrees Celsius (1,650 and 2,000 degrees Fahrenheit).
The first step in co*ke production is the delivery of coal to co*ke oven facilities, which is usually done by barge or railway. The second step in co*ke production is to process the raw material, coal, into a consistency appropriate for co*ke oven batteries.To achieve this consistency, coal is pulverized in a crusher and, if necessary, mixed with water and oil to control the density of the pulverized coal mixture.
A basic diagram of the most common co*ke making process.
This pulverized coal mixture is introduced into co*ke ovens, or “charged,” by a “larry car.” The larry car is akin to a railcar that moves across a track that runs along the top of a co*ke oven battery. Each individual oven has a “charging port,” a door with a lid, that is removed when the larry car is positioned above the oven in order for the pulverized coal to be charged.
After the larry car has charged the coal into the co*ke oven, a leveler arm is activated to smooth the pile of coal that is now inside the co*ke oven. In order to allow the leveler to access the co*ke oven, a “chuck door” must be opened. This leveling process helps ensures that the co*ke oven gas (COG) produced by heating process will flow smoothly through the co*ke oven battery’s offtake system.
Once the leveling is complete, the charging port for each oven is sealed by a process called “luting.” The luting process involves pouring a wet clay mixture around the edges of each charging port. This clay helps prevent leaks (fugitive emissions) from the charging port lids during the thermal distillation co*king process.
Thermal distillation must be complete before the co*ke must be removed from the oven,by a process called “pushing.” If co*ke is pushed from ovens before thermal distillation is complete, it is called a “green push” that produces “green co*ke”, which results in higher benzene and HAP emissions. The pushing process involves a machine that uses a “ram” to guide the co*ke out of the oven. The ram guides the co*ke into a railroad car that is called the “quench car.”
This quench car transports the co*ke to the nearby quench tower, where the co*ke is showered with water to prevent the co*ke from igniting as it is exposed to open air.The quenched co*ke is then transported to a crushing and screening system. This system processes the co*ke into the proper size, so it can be used in blast furnace operations at steel mills.
