2 replies to this topic

[ashish_usct]

hello everybody !!

We are to make specification for a flare tip for ammonia plant which is to be designed for ammonia rich vapors burning.

Now I m in doubt whether to have internal refractory for the flare tip or not?? we have also talked to some reputed vendors each has its own opinion regarding the subject. some of them says refractory will fallout n it may clog gas seal . others say due to low burning tendency of ammonia the residence time for gas is kept high by keeping low velocity in tip that may result in some high temperature profile in tip which can deteriorate the tip material.
Pls not design temperature for the tip is (-) 33 to 150 degC.

So i m confused and need some expert opinion..

Thanks in advance!!!!

[ankur2061]

Ashish,

Refractory lined tips should be avoided as far as possible. This can be done by using exotic alloys for the flare tip such as Incoloy 800 instead of the conventional SS310 to extend flare tip life due to burn-back. Most vendors avoid using refractory lined tips because of many past precedents of the refractory lining getting detached and falling off.

However, if due to unavoidable circumstances refractory lining is a must then the refractory lining should be specified in the following manner:

a. Refractory Material Considerations
The refractory temperature range, stability, and cycling characteristics, its optimum thickness and castability, and its susceptibility to moisture.

b. Attachment Method
This may be based on 'bull horns', 'hexmesh' etc., with consideration given to the means of its installation, repair, and its potential for creating shear planes in the lining.

c. Refractory Reinforcement
This may be in the form of stainless steel needles, which act as "crack stoppers".

d. Refractory Repair
With certain refractories, the repair or replacement of a lining may be considered a specialist task.

e. Refractory Curing
Since most refractory material have been produced for burners, kilns and furnaces, some refractories require a carefully controlled curing and heatup procedure.

However with most lined tips warm air curing may be practical, though gradual heat-up is impossible. Therefore particular attention should be paid to this point at the development stage. Often the refractory requires sealing after curing. The instructions of the refractory manufacturer should be followed rigorously.

f. Storage
Refractory materials can be damaged if allowed to become wet before setting or if exposed to frost after setting.

Hope this information helps to decide whether to go for unlined or refractory lined tip.

Regards,
Ankur.

[JoeWong]

Ankur,
Good say.

Ashish,
Gas assisted flare is commonly used. Your concern is valid. However, SS310, Incoloy, etc as by Ankur is commonly used material for flare tip. Any concern with these materials ?

Concern with refractory is already highlighted by Ankur. Why not request vendor to provide references ? Request site visit or call and talk to the operator to get more real feedback.


When you said "Pls not design temperature for the tip is (-) 33 to 150 degC.". What is the meaning of this statement ? Temperature around flare tip is much higher than 150 degC especially during low flow. No doubt the flare may be intermittent and non continuous, how you determine the temperature ?