123red
20 posts
TimePosted 18/04/2013 12:27:35
123red says

re how to increase C3S & reduce freelime in clinker

Further to Arthur's explanation of the mechanism of sulfate decomposition. When firing high proportions of low-volatile pet-coke with high % sulphur, even 5% O2 ex-kiln may not be sufficient with some firing systems. Despite the overall fuel/air ratio and the reasonable O2 level attained ex-kiln, the flame aerodynamics and fuel combustion process can sometimes produce pockets of kiln atmosphere close to the clinker bed that are sufficiently low in O2 for calcium sulfate to decompose, even when there are no signs of Fe reduction within clinker nodules. If this turns out to be the case for your kiln, then attention to the fuel preparation system, burner alignment and flame settings can still allow high output rates to be achieved when firing a high proportion of pet-coke.

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xxxx
237 posts
TimePosted 19/04/2013 07:32:54
xxxx says

re how to increase C3S & reduce freelime in clinker

DeaR 123Red

I do agree with your comments but when I have almost nil CO at kiln inlet,less SO3 (1.2-1.4%) in hot meal, 93-94% degree of calcination in hot meal , 0.8% SO3 in clinker , no coatings at kiln inlet etc.

All these suggests that the sulfur is not giving much problem nor combustion , than why free lime in clinker is 1.8 to 2.2% .

The flame momentum is around 1800 % m/s . Brit flame , clinker litre weight 1150-1250 etc.

All parameters are normal. What is the next clue to check for high free lime.

Now my idea is to increase the petcoke ratio in fuel from 80 to 90% & let us see the impact.

 

Please do reply

 

 

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123red
20 posts
TimePosted 19/04/2013 18:14:13
123red says

re how to increase C3S & reduce freelime in clinker

All very well, as you say. But my first inclination would be to reduce the proportion of petcoke and see what happens - on the other hand, you could increase it (as you propose) and see if matters get worse, or fail to improve.

One scenario that has been seen in some places is for the coarser particles of char from the coke (that are difficult to burn and have extremely low volatile content) to pass through the flame, be deposited on to the material bed uphill from the burning zone, and get mixed in. Then, if and when they emerge on the surface around the burning zone, they can combust by locally decomposing calcium sulfate and leave CaO as a reaction product.

Good luck.

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Arthur Harrisson
7 posts
TimePosted 21/04/2013 12:13:27

re how to increase C3S & reduce freelime in clinker

It may be helpful to look at an article on microscopy in the April edition of International Cement Review if you have access to this.  I strongly suspect that a microscopical examination by an expert would provide you with the cause of the high free lime and then you can address the most economical way of fixing it.

Rergards

Arthur

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