DEAR TED
IS THERE ANY GOOD IMPACT WHEN WE USE LIGNITE AS A FUEL INSTEAD OF OTHER SOLID FUELS WITH LOW ASH CONTENT.
AS I HAVE SEEN ON NET THAT FLYASH FROM LIGNITE GIVES LIME IN THE RANGE OF 20%.
IF IT IS 20% THAN THIS FLYASH CAN BE USED AS A SOURCE OF LIME IN RAW MIX.
PLEASE EXPLAIN ME IN DETAIL.
THANKS
SIDDHANT
Hello Siddhant,
Sorry, I need you to clarify your question a little more.
Which do you mean;-
1. Adding flyash containing high CaO to the raw mix, as an alternative raw material, or
2. The effect on the raw mix of burning a coal whose ash contains high CaO?
Regards,
Ted.
DEAR TED
WELL I WANT TO KNOW ABOUT BOTH THE POINTS.
ALSO WHAT IS THE IMPACT ON PPC PRODUCTION WHEN WE USE LIGNITE FLYASH OR OTHER
THANKS
SIDDHANT
Hello Siddhant,
Adding flyash containing high CaO as an alternative raw material can have the following benefits;-
1. Lowering production costs. - If the flyash is cheaper than the clay or marl from your own quarry, or if you have a deficiency of clay or marl.
2. Increased production rates. - If your raw mill rate has reached its maximum capacity and your kiln will still accept more kiln feed, you can add flyash to the preheater with the raw meal and boost production rates. The raw mix chemistry must be adjusted in advance to allow for this added flyash, and a redundant system of dosing the flyash needs to be available to keep the kiln feed chemistry constant if one of the dosing units fails. 10-15% flyash may be added with the raw mix in this way.
There should not be much effect on clinker quality as long as the raw mix design is adjusted to compensate for the ash quantity and chemistry. However, due to the high CaO content of the ash, adjusting the raw mix in this way would result in a reduction in limestone requirements from the quarry. Whether this reduction is significant or not would depend on how much ash was being added, as well as the amount of CaO in the ash.
The benefits of using a coal which has high CaO flyash are not as great as adding the flyash directly to the raw mix. This is because the amount of flyash you can add is limited by the %ash in the coal, and how much coal you need to use. Typically this represents less than 2% of the raw mix.
The impact of using high CaO flyash (ie Class C ash) in cement is likely to improve the strength development of the PPC due in part to the pozzolanic reaction, but more so since high CaO ashes contain increased quantities of calcium silicates and aluminates, (identical to those found in clinker), which give cement made with these ashes a degree of self-cementing properties resulting in increased strength compared to PPC produced from flyash with low CaO content.
Regards,
Ted.