537 posts
Re: Pet Coke
Dastgir:
It means that free lime be on higher side, if we use Pet coke?
Hello Gulam,
Only if there is not enough K2O and Na2O to form alkali sulphates. Alkali sulphates form their own separate liquid phase which is immicible with the silicate phases.
Therefore, if you have a molar balance of alkali to sulphate, you will prevent excess SO3 dissolving in the C2S which, in turn, will prevent the retardation of C2S reaction with CaO to form C3S.
Regards,
Ted.
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108 posts
537 posts
Re: Pet Coke
How much gypsum consumption is generally encountered for nominal setting times, if the plant is utilising 100 % pet coke.
Hello Gulam,
It depends on the molar Alkali/SO3 ratio of the plant's raw material and petcoke inputs, which determine the quantity of water-soluble sulphates available.
When Alk/SO3 > 1.1 almost all of the SO3 is present as alkali sulphates.
When 0.9 > Alk/SO3 < 1.1 the SO3 is predominately present as a mixture of alkali sulphates and calcium langbeinite (K2SO4.2CaSO4)
When Alk/SO3 < 0.9 the SO3 is present as a mixture of alkali sulphates, calcium langbeinite and possibly anhydrite (if the O2 level in the burning zone is high enough). Any SO3 in excess of that required to form the sulphates will form a solid solution with the silicate phases (mainly belite), up to about 2% w/w of the total silicates.
Alkali sulphates and calcium langbeinite are rapidly soluble in water and therefore can contribute to cement set control. However the SO3 in the silicate phases is not readily soluble and therefore not available for set control.
To make matters even more complicated, there is some evidence that the amount of C3A formed in the clinker is reduced by high clinker SO3 levels. See;-
http://www.hindawi.com/journals/ijac/2010/102146.html
This will also tend to reduce the amount of gypsum required.
So, the amount of gypsum required for set control when using petcoke (or any high-SO3 alternative fuel) will be different for each plant and will require plant or laboratory trials to determine the exact optimum.
Perhaps some participants in this forum who are presently firing 100% petcoke would like to share their practical experiences regarding optimum cement gypsum levels for their clinker.
Regards,
Ted.
108 posts