re Role of SR and AR

Hello COE,

The following links will help you understand the effect of varying the ratio of Al2O3 to Fe2O3 on liquid formation;-

http://resource.npl.co.uk/mtdata/glabar.pdf    (See page 22)

http://www.arthurharrisson.com/cement%20chemistry.html   (In particular the following paragraph;-  "In a situation where there is an AF ratio of 1.38, 2% MgO and 1.5% clinker SO₃ is it quite possible that the clinker may contain well over 30% liquid well before the burning zone.  In most instances this will not be acceptable in terms of coating tendency and potential ring formation within the kiln and a move away from the traditional optimum alumina to iron ratio will be necessary to optimise the kiln performance." )

To answer your other questions regarding AR and viscosity;-

The main issue with clinker balling and kiln rings is not liquid phase viscosity, but the sudden changes in liquid phase quantity due to fluctuations in AR around a value of 1.38 at the point in the kiln corresponding to ~1338oC. The amount of liquid phase present is at a maximum at this point and is also very sensitive to changes in AR, whereas the liquid phase viscosity is not increased significantly by just moving from AR = 1.35 to 1.5.  An extreme example of this is white cement clinker, where the AR of the clinker is very high (>10), yet this still produces a thin, stable coating with good particle size distribution and almost never results in clinker balling.

There also seems to be some differences of opinion between various researchers and authors on the subject of liquid phase viscosity and nodule formation.

In his book, "Cement Chemistry", Taylor claims that clinker nodulisation is favoured by low liquid viscosity. (p74)  However, many other authors and articles suggest quite the opposite. eg "Lea's Chemistry of Cement and Concrete", 4th Edition p65, states that "lower viscosity flux may lead to more dust being formed in the burning zone".

I agree with the view that, for a given burning temperature, high C3A clinkers tend to nodulize better than low C3A clinkers. However, better nodulisation is not the same as the excessive nodulisation experienced with clinker balling, which is almost invariably caused by too much liquid, too early in the kiln. In addition, if the quantity of liquid phase is also varying at this point (due to AR fluctuations around the 1.38 point),  this will only tend to further promote excessive nodulisation and clinker balling.

 

Regards,

Ted.

 

 

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re Role of SR and AR

Hello Archi,

I am guessing that the special reason you are referring to is the use of a high ash fuel or other AFR which is high in alumina.  Remember that it is the LSF, SR & AR in the clinker that is important to understand what may be happening in the burning zone, not the chemistry the kiln feed.

What is the full chemistry of your clinker? 

 

Regards,

Ted.

 

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re Role of SR and AR

Dear Mr Ted!

We didn’t change fuel and use AFR during that time.

Special reason is very simple, our quarry couldn’t exploit high AR clay, which we cannt change immediately.

Chemistry of clinker: SiO2 21.3, Al2O3 4.84, Fe2O3 3.96, CaO 65.03, MgO 3.29, Na2O 0, K2O 0.47, SO3 0.41, CaO free 1.26; LSF 96.01, SR 2.42, AR 1.26.

Sometime we make yellow soft core clinker while we maintance high oxygen in kilninlet (app 4%), and SO3 in hotmeal only 1.5%. I consider any relation between low AR and build-up piece at kilninlet and riser duct. Beside, we burnt yellow hard core clinker very easy.

1^st and 3^rd strengths of correlative clinker are 18 and 31 MPa.

If we must operate kiln with above clinker, how does it effect to refractory lining and later strength of clinker?

Best regard,

Archi

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re Role of SR and AR

Thanks a lot sir,

 Need following clarification.

Liquid pahse calculation has several formulas

at 1338 deg C  AR< 1.38 , LP = 8.5*Al2O3 - 5.22*Fe2O3 + MgO+K2O+Na2O

at 1338 deg C  AR> 1.38 , LP = 6.1*Fe2O3 + MgO+K2O+Na2O

Can you please explain how above formaula is derived?

As ferrite and aluminate both take part into the liquid formation why in 1st case why Fe2O3 is being subtracted and second case alumina is deleted?

at 1400 deg C  MgO<2% , LP = 2.95*Al2O3 + 2.2*Fe2O3 + MgO+K2O+Na2O

Why LP is calculated on two different temperature?

You can sent any literature in my email tushar.ghorai@acclimited.com

Regards

 

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