537 posts
Re: brown core in clinker
1. Your Alkali/Sulphur balance, which determines whether you have sufficient alkalis to offset the extra SO3. Which is the Alkali/Sulfur balance must be? What is the relation between it? Is there any formula? What kind of material we can use to increase Alkali?
dry process: Ted Krapkat:
As applied to hotmeal, the alkali/sulphur balance is the molar ratio between alkalis, chloride and sulphur given by the equation;-
[K2O/94.2 +Na2O/62.0-Cl/71.0] / [SO3/80.1]
This value should be >1.0 and ideally 1.1-1.2.
NOTE: It is very important that you calculate the alkali/sulphur ratio on the hotmeal under good, steady kiln conditions, over a period without upsets and without significant reducing conditions in the kiln inlet, because these conditions will give a falsely low and misleading alkali/sulphur ratio.
If the average alkali/sulphur ratio of your hotmeal is less than 1, you have not enough alkalis to counteract the SO3 in your mix and the excess SO3 is likely to cause problems even without any reducing conditions present in the kiln inlet. These problems would of course become increasingly worse the lower the alkali/sulphur ratio becomes.
Normally you would increase the alkali/sulphur ratio by reducing the SO3 input, however if you are forced to use a high SO3 fuel, as in your case, you would have to increase the alkalis by using a suitable raw material, preferably from the quarry.
2. The kiln inlet O2, which determines whether the extra sulphur will be converted to the less volatile alkali sulphates (SO4), rather than the problematic SO3. What is the relation of conversion from SO3 to SO4 according to inlet kiln O2 concentration? Is there any models or formulas which describe it? If we have less O2 that mean we will have more SO3 than SO4, isn't it? How we can determine the optimum kiln inlet O2, only increase it and watching what will happen? dry process: Ted Krapkat:
There are no practical models or formulas, you only need to have just enough oxygen to eliminate (or optimally minimize) CO in the kiln inlet.
Normally this requires at least 2% O2. But, if your flame is in bad shape or some other problem is causing bad burning conditions and you are producing excessive amounts of CO in the kiln inlet, you may need to increase the O2 to as much as 4 or 5% and see if you get an improvement.
However increasing kiln inlet O2 is just a temporary fix and you should investigate what is causing the reducing conditions in the first place. It could be a damaged or malfunctioning burner, high fine coal residues, fluctuations in coal quality/quantity fed to the burner or one of many other fuel/air related causes.
Also, hand-held digital infrared cameras for identifying the areas where slabs are building up can be obrained from a company called FLIR... more info can be found here;- Hand-held digital infrared cameras use for determining outside cyclone, kiln and so on temperature and if in any place where all other parts should have the same temperature it will have less temperature that means there we have buildups and we must install there blast point. Isn't it? dry process: Ted Krapkat:
Yes, essentially that is correct. But you have to perform many infrared surveys over several weeks, noting the kiln conditions at the time and carefully analysing the results. Then, if you see a pattern of regular buildup formation and release in a particular spot, you can then decide to install a blast point.
Regards,
Ted.
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5 posts
Re: brown core in clinker
Can be that liquid phase impact on Fe2+ or free lime formation. I mean density, quantity, composition? If yes – how we can change/ led or calculate it?
Can be also the reason of Fe2+ formation that flame shape is too wide (or it straight point at clinker) and that's why it very close to clinker what is the case of less O2 over the clinker and also to high temperature? If there is true we will have to change the flame shape or burner position, isn't it? We use Unitherm burner.
Regards,
Vladimir
537 posts
Re: brown core in clinker
Can be that liquid phase impact on Fe2+ or free lime formation. I mean density, quantity, composition? If yes – how we can change/ led or calculate it?
In the case of Fe+2, I doubt that very much. Formation of Fe+2 is a REDOX reaction, so the amount and properties of the liquid phase are far less important than the amount of excess oxygen present to ensure complete combustion of the fuel.
However in the case of free lime, liquid phase is required to facilitate the reaction of dissolved CaO with C2S to produce C3S, so the amount of liquid phase and its properties can of course influence the rate of this reaction and therefore the quantity of free lime remaining in a given time.
dry process:
Yes. Flame shape and inclination are very important. In the burning zone, heat is best transferred from the flame to the clinker bed by radiant heat, not direct contact of the clinker with the flame itself. If the flame is in direct contact with the clinker bed, there can be localised reducing conditions inside the flame that can strongly promote the formation of Fe+2 in the clinker. In fact, this technique is sometimes purposefully used in the manufacture of white cement clinker and is called "Bleaching". This procedure involves directing a second, separate flame onto the bed of clinker close to the kiln exit to reduce Fe+3 to Fe+2, to help lighten the color of the resultant cement.
The flame shape needs to be short and sharp for maximum effect and the inclination of the burner close to the axis of the kiln.
Regards,
Ted.
85 posts
Re: brown core in clinker
Sir,
How to check whether the clinker made is of Fe+2 or Fe+3.?We noticed that in kiln operation when we have a strong burning zone temp then the O2 % at kiln inlet also in good ratio .And sometimes On seeing the high burning zone temp if we try to reduce the fuel we noticed not able to control the kiln operation because the kiln torque is already on the min range with high burning zone temp and cooler temp frequently getting disturbed.Whats your suggestion pl.?