kiln inlet coating

Hi Armankhan,

I can answer your first question;-

Kiln Inlet buildups are normally due to an increase in recirculation of one or more of the volatile components within the kiln/preheater system. ie alkalis, sulphur or chloride.

The usual culprit is sulphur, whose volatility is strongly influenced by the O2 content at the kiln inlet. If insufficient O2 is present in the kiln gases at this point, the following reaction cannot completely take place;- 

2 K2O(g) + 2 SO2(g) + O2(g) --> 2 K2SO4(s). 

Alkali sulphates are far less volatile than alkali oxides and chlorides. So, if this reaction is impeded, SO3 recirculation will increase suddenly and dramatically, causing buildups and possibly even rings at the kiln inlet.  Lack of sufficient oxygen at the kiln inlet could be caused by either insufficent secondary air flow or poor combustion in the main burner flame.

Of course an increase in alkalis, chloride or sulphur inputs to the kiln (ie in raw materials or AFRs) can also cause buildups and rings in the kiln inlet area, particularly if the SO3/(K2O + Na2O) molar ratio is not in balance (~1.0).

Also hard burning can increase the recirculation of alkalis, sulphur and chloride as well, by increasing the evaporation rate of these components in the burning zone. The burning zone temperature and kiln inlet temperature should be carefully controlled to minimise this.

I will leave your other two questions re Polysius kilns to one of the process engineering experts...

Regards,

Ted.

thanks sir alot