I want to know if some factor of conversion exists for a cement kiln of two stages converted to oven of lime (without use of the tower). For example, if the cement kiln production is 1000 Tn/day, which would be the lime kiln production?
lalbatros
As a quick guess, I would be inclined to say that the calcination rate would be the same, that is the same quantity of CaCO3 should be calcined. However there are reasons for some difference too.
- Removing the tower would imply that the preheating should occur in the rotary kiln.
- The absence of clinkerisation would change the total heat balance too.
- The burning temperature could also be lower (1000°C instead of 1450°C)
- What about the cooler?
I would be tempted by some 1-D simulation.
Indeed, what really doesn't change is the rotatry kiln and its behaviour as a heat exchanger !
To do this, more info would be needed, like the dimensions of the kiln or a detailled heat and mass balance.
Note further that the bottleneck might lie in the heat exchange as well as in other aspects like gas velocity and dust entrainement. For example, assuming the gas flow cannot be increased, then based on CO2 production and fuel consumption (say 5.5 GJ/t for lime) you could scale from clinker to lime. (I got 65% in a rough estimate)
That's a nice subject you are considering.
I hope you will enjoy!
Ted Krapkat
Hi,
We did this exercise in 2004 when we converted our old 125t/h, single string cyclone preheater kiln into a 36t/h lime kiln. However, the Metso limestone preheater was sized for a specific lime market volume, not the actual maximum possible capacity of the kiln, which is estimated at about 80t/h.
The old cyclone preheater tower was removed and a new limestone preheater was installed. This utilises the waste heat from the burning zone to pre-heat the incoming limestone pebbles (10-40mm) to about 900-1000C. Actually approximately 50-70% of the calcination happens in the preheater.
The burning zone temperature is usually about 1150-1200C and we use a low-ash pulverised coal as fuel. We also used the same cooler.
To answer the original question as to the scaling factor, our experience is that with the correctly-sized limestone preheater, you should be able to achieve at least 60% of the old clinker production rate.
http://www.cemaust.com.au/files/Mission%20Accomplished.pdf
Hope that info helps,
Ted.
gabriela.guzzo@lomanegra.com.ar
According to our experience, you can achieve aprox. 70-75 % of clinker production
Regards