Re: Alk / SO3 ratio

Hello Bandari,

thx for ur reply and clarification ,

your clarification of Alk - sulfate ratio equation based on that the Cl is very  low and can be neglected - so you build your explanation that the balance will be only between Alk and SO3 - Am I true ?   

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Re: Alk / SO3 ratio

Electron1539 & Bandari,

Remember of course that all these formulas assume completely oxidising conditions in the kiln. You can have perfectly optimised SO3/Alk (even a deficiency of SO3) and still get frequent SO3-based deposits and buildups in the preheater, precalciner and/or smokebox due to reducing conditions caused insufficent oxygen in the back end of the kiln.

 Regards,

Ted,

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Re: Alk / SO3 ratio

Dear Mr.Ted Krapkat,

Thanks for your information shared.Could you also please tell that at what condition spurrite (2C2S.CaCO3) formed and how to avoid the formation of spurrite?

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Re: Alk / SO3 ratio

Raj Sahu:

Dear Mr.Ted Krapkat,

Thanks for your information shared.Could you also please tell that at what condition spurrite (2C2S.CaCO3) formed and how to avoid the formation of spurrite?

Hi Raj,

Carbonate Spurrite is formed by reaction of  CO2, with freshly formed free lime and C2S, or sometimes even through recarbonation of C2S. Unlike CaCO3, spurrite is stable up to temperatures of 910 deg C (ie 60 -70 deg C higher than CaCO3)

Spurrite buildups form whenever the partial pressure of CO2 is high enough to invert the calcining reaction. In coarsely ground, silica-rich raw mixes, which are heated below 910 deg C for an extended period, the free lime does not have sufficient time to react with silica, therefore increasing the chances for spurrite deposits.

Buildups and rings cause by Spurrite formation are hard, layered and, at first glance,  often exhibit the same chemistry as regular clinker. However XRD or Differential Thermal Analysis and Thermogravimetric Analysis can easily identify Spurrite.

Spurrite generally forms fibrous particles which tend to interlock, in a process which promotes and strengthens rings and buildups. Spurrite is often found in the interior of meal rings, rather than on the surface, which indicates that this interlocking process is acting to strengthen already-deposited material.

Spurrite formation can be reduced or eliminated by ensuring that the raw meal fineness is sufficient to enable rapid reaction of freshly-formed free lime with silica to form C2S at temperatures above 910 deg C.

Regards,

Ted.

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