We are a 7200 tpd kiln with coal as the main fuel and sometimes use about 5-10 % natural gas depending on the availability of gas.While we are running the kiln with normal operation ,recently oneday we noticed that the kiln torque started reducing and the burning zone temp increasing from 1350*C to 1500*C.The cooler first grate pressure increased to 130- 140 from the normal 90-to 100.On seeing the brightness of the kiln we reduced the fuel and reduced the torque from the normal 70 to 80 kw to 40 to 50.kw.However the kiln operation was very disturbed with the secondary air temp flutuating to too high or too low level.Under such circumstances how best to stabilise the kiln.When the clinker chemical analysis report came after about 2 hrs its noticed that the clinker HM has come down from the normal 2.13 to 2.06,and LSF from 93% to 90.Is it the main cause for the disturbance in operation.Is it possible to lower the torque to further low level in case of such low material.According to our experience if we the torque go below certain level at whatever low the material is, the kiln disturbes heavily.Kindly suggest
Kiln operation suggestion.
This sounds like a severe “push” by the kiln. Essentially the material emptied out from the kiln into the cooler at a faster rate than normal. That explains the reduction in the torque and the increase in the cooler under-grate pressure. This might have resulted from the change in the alumina modulus and a change in the flux characteristics, although the effects you describe are severe. Reducing the fuel was certainly a good response as the empty kiln would have less material needing the thermal input from the fuel. An alternative control response at the beginning of such a “push” would be to slow the rotational speed of the kiln.
Dr Michael Clark.
for sure it looks that the flux nature has changed in kiln feed, most probably the AM would have increased. however for this easy burnable material you can desrease fule input, but i think that the increase in burning zone temperature at the same fule rate is much due to the clarity in your burning zone, because of higher AM.
you may also get higher liter weights(with higher free lime comparably), and cooler undergrate pressure will also increase, your kiln will become very sharpe i,e: soon it will disturb and increasing coal(by .5t) will pick-it-up quickly.if so is the condition try to increase get back in preveous chemistry.
untill your chemistry is back to normal, try to operate kiln with slightly lower rpm, and don't be much confused with BZ.temp.to reduce torque further,be carefull in cooler operation,increase first cooler fan flow. try to operate as smooth as possible with modified parameters.
In general I am agree with Dr Clark and Bilal. It is clear that meal in the case become more burnable. You must define what is the main reason of that. If there is no change in raw meal characteristic, I think it may be connected with fuel ash content decrease (or maybe chemical compound change) .
I think you must increase the grate speed of the cooler, and stabilaze the secondary air temperature and quantity. This must reduse the cooler first grate pressure. You can try to add the meal feed too. But each change you must perform separately and observe what happens.
Is there any coating pieces with clinker in the transporter ? I want to mention that kiln torque can reduse when coating are collapsing too.
For more detailed answer, It will be fine if you bring Alumina Ratio, kiln cool end temperature, cooler chain transporter motor load change, clinker grain size change or some other data, connected with the case.
With best regards David Babayan