Re: Mineralised Clinker (Flourite)

chari:

There is method to determine Florine in lab. It is determine by

1. Convert all metal florine to metal sulphte by reacting with sulphuric acid.

2.The gaseous HF with react with SiO2 to get gaseous silicon tetra floride.

3.pass through water

4.silicon tetra floride will convert to florosilicic acid

5.Titrate against standard NaOH to get florine value.

 

Hello Chari,

This is a fairly old and complicated method which requires special apparatus, chemicals and conditions to work correctly. For example, the reagents must all be free of traces of moisture and even the apparatus itself must be totally dry.

HF is quite volatile and must be completely scrubbed from the resulting gases. Other acidic products such as SOx (from sulphur containing minerals) and NOx (from nitrates) must also be removed, not to mention hydrogen chloride.  HF can also attack the glass vessels, producing its own SiF4 independently of the sample.

So, these days, specific ion electrodes are the method of choice for most fluoride analysis because they are far simpler and easier.

 

Regards,

Ted.

 

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High dust cecirculation and high free lime in ouy kiln

Dear Ted, We request your help in solving our above subjected problem. At sanghi cement we are having 9500Mt/Day kiln where axial air is being maintained11500 and radial zero(0). The dust recirculation is so high that burning zone temperature could not be assessed (it is showing in the range 900 to 1050 degree centigrade).We are using high VM Indonation coal, our raw mix is having 1.1 to 1.2% SO3 and nearly 2.3%MgO, maintaining residue on 212mic is nearly 3%. Our clinker analysis is as under:- Loi 0.28% SiO2 20.54% Al2O3 5.53% Fe2O3 4.14% CaO 63.79% MgO 3.82% SO3 1.08% Cl- 0.028% LSF 96.61 SM 2.13 AM 1.33 F.CaO 2.8% Liq. 29.93 Please inform, what possible stapes we could take in arresting above subjected problems. Warm Regards, Rajiv Modgal G.M(Q.C) Sanghi industries limited

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Re: High dust cecirculation and high free lime in ouy kiln

Dear Mr Rajiv,

Based on the replies that you have sent so far and analyzing the same, it is recommended that immediately Fe2O3 in raw mix is brought down from the present level of 2.5 to around 2.0 +- 0.1 and compensate with clay gradually at raw meal VRM stage keeping CaO value at 41.2. Kiln must have stable operation ( no stoppages,).Do not do too many changes at a time.

Monitor

• shift wise Clinker Targets CaO (64.0 + - 0.5), Free CaO (below 2 %) and Fe2O3 (3.3 + -0.1);
  
• daily full analysis of clinker to know the moduli values and clinker compounds ;
  
• also sieve analysis of clinker to understand reduction in dustiness.

Kiln Operators should be taken in to confidence and note down

• their observations besides your own.
• Take the help of a competent process engineers who knows kiln,cooler operation.
• Fuel feed to precalciner may be required to increase depending upon the temperature profile and accordingly kiln fuel adjustment.
• Cooler operation is adjusted so that adequate secondary and tertiary air temperatures are maintained.
• Maintain adequate negative kiln hood draft value as per the process.
  

Also,

• record the physical properties of daily clinker for its strength ( 1D/3D/7D/28D) and compare for the improvement.

This should help you to some extent.However, there appears to be further scope to optimize raw mix composition

Pl.try out the above recommendations for 5 days(stable operation) collect all the data as mentioned above and see whether the problem of dusty clinker minimizes or not, what other benefits in clinker quality and kiln operation you get; and give me the feedback.

Pl.confirm.
 
Best Wishes

Bhaskar Agate
09096832830 (M)

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Re: High dust cecirculation and high free lime in ouy kiln

RAJIV MODGAL:

Dear Ted, We request your help in solving our above subjected problem. At sanghi cement we are having 9500Mt/Day kiln where axial air is being maintained11500 and radial zero(0). The dust recirculation is so high that burning zone temperature could not be assessed (it is showing in the range 900 to 1050 degree centigrade).We are using high VM Indonation coal, our raw mix is having 1.1 to 1.2% SO3 and nearly 2.3%MgO, maintaining residue on 212mic is nearly 3%. Our clinker analysis is as under:- Loi 0.28% SiO2 20.54% Al2O3 5.53% Fe2O3 4.14% CaO 63.79% MgO 3.82% SO3 1.08% Cl- 0.028% LSF 96.61 SM 2.13 AM 1.33 F.CaO 2.8% Liq. 29.93 Please inform, what possible stapes we could take in arresting above subjected problems. Warm Regards, Rajiv Modgal G.M(Q.C) Sanghi industries limited

Hello Rajiv,

With a raw meal SO3 content of 1.1 - 1.2 your clinker should have at least 1.8% SO3, if all of the sulphur is leaving the kiln yet your quoted clinker figure is the same as the raw meal. This is quite strange... unless you have a dust bypass?  What is the SO3 content of your coal?

Your quoted raw meal fineness of ~3% retained on 212um seems a bit high. Normally it is recommended to operate with a residue on 212um of <1%. What is your 90um residue? Do you use appreciable amounts of sand (quartz) as a silica corrective?

Chemically your raw meal appears of reasonable burnability.Your clinker liquid phase is a bit high, but that should not cause dusty clinker.

You may have reducing conditions in the kiln inlet. Do you know the SO3 content of your hot meal exiting the bottom cyclones and the kiln inlet gas O2 and/or CO content?

Also, what is your clinker K2O and Na2O content? If you have a high molar SO3/Alkali ratio, this could cause dusty conditions in the kiln.  Alkali sulphates also reduce the liquid phase viscosity and surface tension, both of which promote finer/dustier clinker.

Your clinker SO3 content is quite high, so depending on your molar SO3/Alkali ratio and whether or not you have any reducing conditions in the kiln inlet, you may have an excessive SO3 cycle. This can promote buildups/slabs forming in the kiln inlet/precalciner which fall into the kiln regularly, causing high free lime and dusty conditions as the unburnt buildups fall into the cooler. If this is the case you should see the clinker free lime spiking very high then returning to normal periodically... sometimes with a regular frequency of just a few hours.

To prevent this sort of sulphur-related buildup problem you need to ensure your kiln inlet O2 content is always >2% (or as high as is necessary to prevent CO formation)

Other factors that may influence the dustiness of the clinker are;-  poor raw meal burnability, kiln rotational speed too high, variable kiln feed LSF, variable raw meal fineness, variable fine coal feed rate, fineness or energy/ash content.

 Hope this helps....

Merry Christmas and best regards,

Ted.

 

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