API 12L Treater

[engpes]

I have a 2.1 MMBTU/HR Duty (net) API 12L Treater that has the stack temperature that is getting too hot (950 F). The unit consists of (2) burners (natural draft - 1.05 MMBTU/HR each) mounted to (2) "U" type 18" firetubes.

I have (2) dual pass 18" OD firetubes (see attached sketch), with a total area of about 226 ft^2. I am calculating the heat flux through these tubes to be 2,100,000 BTU/HR / 226 FT^2 = 9,292 BTU/HR/FT^2, which is well below the API 12L allowable (10,000 - 12,000).

The unit is being tested with stagnant water at the moment (not flowing oil) and the medium temperature is rising quickly, but the stack is getting too hot. The burners are running at nearly 100%.

My question is this:

1.) Are my heat flux calculations adequate?

2.) Should the initial test medium be brought up to temperature slower before turning the unit online?

Thank you in advance!

 

[SNORGY]

Have you done a calculation on the fuel side to see how much fuel is being burned and what is the heating value of that fuel?

Maybe the problem is as simple as a BMS setting or a regulator set point.

 

[dcasto]

So where is all that steam going that you are making and then uncovering the tubes causing a loss of heat transfer