Hello to everybody

ple to be answer me our plant was stopping many times for reason of preheater fan impeller coating formation because of this problem we are stopping plant 2 days for removing the coating. What are the reasons to form the coating.

Y.Ravi Kumar

UAE

The reason for fan impellor coating are connected with the process, i.e. the temperatures, amount of dust leaving the preheater, composition of that dust. There are various ways of coping with this problem from design of the fan and impellor to avoid coating, cleaning while operating or automatically balancing the fan to allow operations to continue despite the coating. 

Dr Michael Clark

Thank you my dear clark for your reply

But we stopping the fan due to heavy vibrations of fan bearings and motor.after cleaning the impellor again we starting the plant. i want more clarification of the  process composition. ple tell me

YRK

 

 

Dear YRK;

We are facing this problem from time to time and we know that the reason of this coating has close relation with the kiln outlet gas which passes through the Conditioning Tower (C.T). If you keep the setpoint of the C.T outlet gas temperature low more water from water spray nozzels will flow and you can count this as a reason of the coating. I beleive that you have problem in the C.T Water spary unit or in the outlet gas temperature.

best regard

You should restrict the PH outlet temperatures to less than 350 deg C at start up before feeding the kiln after a long stop.

During very short stops do not allow the PH outlet to go beyond 400 deg C

Some plants  inject 30 to 50  kgs of fine sand or clinker approx 4mm size in the down comer to reduce the speed of coating formation.

 

Hi

 Use of high sulphur fuel  encourages formation of cementious calcium sulphate which can form hard deposits on the ID fan blade. This is especially so if alkali sulphate ratio is off optimum range. In our plant I always associate use of high sulphur fuel with high Id fan vibration resulting largely from un even deposit on the fan blades. 

Most proven way to reduce ID fan vibration is to maintain the PH exit gas temperature about 200 deg.cent by water spraying in downcomer duct.If you are not able to control PH exit gas temperature around 200 degree cent. then best countermeasure is, whenever opportunity comes, clean the PH fan coating by "High Pressure water jet pump",you may clean the coating in less than 1 hour by the method.

There is a very good article on ID fan coating formation here:

http://cementamericas.com/mag/cement_solving_problem_buildup/ 

If nothing else can be done, active fan balancing technology can vastly increase the period between subsequent needed fan cleanings. For example of this technology:

http://www.concretemonthly.com/monthly/art.php?593

Best regards

Deal all

Ple to get your reply , that what is particle streamlines. As envisaged in above alticle by you i gone thru the Robinson take-on to coping the problem . He significantly gathered the problemestic information that was the root problem, but he has concened over to redisign the fan resonance with new expansion. Additionally hhe proposed to match the shape size of fan blade close to material streamlines to reduce the build-up problem.

Now what makes me to stem to understand is ;

What is

1) Matreial stream lines

2) Build-up problem

3) How this can patronage to overcome with the problem.

Looking for someone comments

cheers

rahul 

Hello

You dont pointed. Do you have a by-pass system. If no you should install it. Or enothe way to instal differential small chamber decrease temperature and preasure befor id fan. Enother way to check and move inlet of by-pass system.

If you already have manage it. please let me know how?

Best regards 

Mihail

 You are right. Bypass system between preheater and kiln will help in reducing the level of alkalies in preheater gases which in turn will reduce the recycling of free alkalies in preheater and coating of the same in Preheater fan and avoid Preheater cyclones jamming.

Best regards,

Sachin 

 

 

Dear Mr YRK,

Could you please tell us that are you interested to know the cause of the problem or countermeasure of the PH fan vibration problem?

Dear  Mihail

Couldnt avoid being curious to get your sense about bypass. This sounds that your intensive experience would favour us to get intensified benchmark with considerable foundation. My view is , i  havnt heard of  bypass b/w the preheater and kiln or perhabs it may be my lack of knowledge.

1) As spelled by you bypass may avoid alkalies being recycling of thereoff offsetting the chances of coating in Fan . Objectively what it does to make the system stay off the culprit of coating . Presumable as per our knowledge we gives the blast air to ID impeller to remove coating problem. But if thereis seperate concept like you highlighted , that would really be a constructive action to cope with this problemistic situation.

Looking your furthur reply

Thanks in anticipation

RAHUL  

We have the same problem as our raw materials are high in sulfur and we are now burning petcoke with 6% sulphur. However we have been using a method for some years which allows us to solve the problem in 1 hour.

Stop the kiln and IMEDIATLY open the Fan door and wash with cold water - use a (hose). The thermal shock will cause the build-up to SNAP rigth off the blades. Some people will try to convince you that the thermal shock will damage / deform the impeller - not true, we do this operation every month and the fan is always balanced.

Dear Mr.MFM,

Your reply support my answer which,I have already replied for the same query of Mr.YRK.My reply was as given under:

 "Most proven way to reduce ID fan vibration is to maintain the PH exit gas temperature about 200 deg.cent by water spraying in downcomer duct.If you are not able to control PH exit gas temperature around 200 degree cent. then best countermeasure is, whenever opportunity comes, clean the PH fan coating by "High Pressure water jet pump",you may clean the coating in less than 1 hour by the method.

" Regards,

R.M.Sahu