Where is the coal in the cement kiln?

Walk into the modern cement factory and you will see a magnificent rotating beast, the cement rotary kiln.

The rotary kiln production line

runs day and night, swallowing yellowish raw meal powder and spitting out the gray clinker used to build the world. The "source of energy" that drives all this is coal. Have you ever thought about the

coal yard

: where does the coal that is ground into pulverized coal and sprayed into the kiln go? Is it like the briquettes at home, with only a pile of cinders left after burning?

The answer may surprise you!

Coal, almost completely "disappeared"

The core area of the cement kiln in the coal mill production workshop

is the rotary kiln firing zone, which is the key link of clinker calcination, and the temperature is usually stable at 1400-1450 ℃. Here, the journey of coal is an intense and thorough "self-sacrifice", which mainly "evaporates" in two ways.

1. Energy transformation: from "black ore" to "invisible power"

, which is the most important and direct destination of coal. The coal is pulverized into pulverized coal by the coal mill. Part of the pulverized coal is injected into the rotary kiln through the kiln head burner, and the other part of the pulverized coal is injected into the decomposition furnace through the decomposition furnace burner. The pulverized coal reacts with the preheated air and ignites instantaneously, resulting in a violent oxidation reaction (combustion). This process is essentially the conversion of chemical energy into thermal energy.

Coal burns

carbon and hydrogen, the main combustible components in coal, combines with oxygen to produce carbon dioxide and water vapor, and releases the heat necessary to maintain the whole cement production process. It is this heat that makes the raw material decompose and melt, and finally forms the cement clinker mineral with hydraulicity.

Therefore, the vast majority of coal has turned into invisible heat flow and become the "soul" driving the cement burning reaction.

2. Material Fusion: The "Skeleton"

of Cement If burning and releasing energy is the "duty" of coal, then the next role is its unexpected "cross-border performance". When

coal is burned, it does leave behind a very small amount of solid residue, which we usually call coal ash. However, in the high temperature environment of the cement kiln, the coal ash will not be discharged separately like garbage. On the contrary, it is "captured" by the high-temperature raw meal and directly participates in the mineral formation reaction of cement clinker. The main chemical components of

coal ash are silica, alumina, ferric oxide and so on, which are the key components needed to prepare cement raw materials. Therefore, the coal ash is uniformly blended into the liquid phase of the cement clinker and becomes a part of the cement clinker.

You can think of it as: not only does the coal burn itself to provide the "flame", but also the last "ashes" are turned into the "skeleton" of cement. What is left of the

"missing" coal?

Now we can answer the original question: Where is the coal in the cement kiln?

1) Most of the carbon dioxide and water vapor are discharged into the atmosphere through the chimney.

2) a small portion → a component of the cement clinker that is permanently solidified in the cement product. Coal in

cement kiln has completed a magnificent transformation from "energy" to "material". It burns itself, providing the "divine power" to create the cement; the ashes it leaves behind melt into the "body" of the cement. The mission of Conch Cement is to make this transformation more efficient, more green, low-carbon and environmentally friendly, while creating future living space for mankind, to protect our green mountains and rivers.