flue gas water spray dryer 1

[coatingking]

We have a challenge to build a 15'dia by 60' flue gas chamber of steel(?) and provide a liner (refractory) perhaps ceramic ( or cast in place) to handle a variety of waste products (gases and particulate at the top 2400F and cooling by water spray to 500F at the bottom.

 

[Montemayor]

coatingking (Materials):

Congratulations. Do you have a specific problem or question(s)?

Art Montemayor
Spring, TX

 

[coatingking]

Thanks Montemayor, you're a God. The problem in case you have figured it out is that the shell or the steel chamber is corroding rapidly due to the high heat,water/steam saturation, and various chemicals in the flue gases along with the brine content of the water spray.

 

[Montemayor]

coatingking (Materials):

First, allow me to congratulate you once more on this unique challenge – and then follow through with my sincere empathy for the hard work ahead. You’ve assumed correctly that I may have some suggestions that will make your work go forward faster or, hopefully, with success. I’ve been in similar, if not equal, pickles. I’ve built and applied flue gas cooler-scrubbers in the field – with success. However, my units didn’t approach yours in size. My units were 7 feet in diameter x 20 feet tall and cooled 500 – 600 oF flue gases. Like you, what I had to replace was a disastrous design that merely utilized carbon steel construction.

What you are undertaking is going to entail a lot of common sense, emphasis on detail, and hard work. Allow me to enumerate the various points:

1) Carbon steel is not going to cut it as wetted process material, so forget it. However, you may have to rely on it for external, non-wetted, structural material. You will have to ensure that it bears the stress, but yet is free to expand and contract at the relative high and low temperatures. This is an exercise in detailed and horse-sense engineering.

2) Try to employ a ceramic, acid-proof, and sealable core material for the internal, wetted walls. I’m assuming you are dealing with an essentially atmospheric flue gas stream. In other words, you only have a few inches of water column pressure and you don’t have to furnish hoop stress or design for internal pressure.

3) Flash your internal, ceramic walls liberally. In other words, the seams of the upper parts should over-lap the lower parts. Try hard to use as large pieces as you can for the internal walls – ideally the internal walls would be cylindrical sections, one on top of another. But, of course, with your 15 ft diameter this may not be feasible. By all means, try to keep the amount of internal seams on the ceramic portion down to as small a figure as you can. Consult with professional ceramic factories and fabricators. They are the ones who can be your guardian angel on this type of project.

4) You will require to have a structural expert on your team to develop and/or contract out the method of physically supporting the large and heavy 60 ft height of internal material that has to remain integral and sealed while going from cold to hot and then back again during startups and shutdowns. Liberal and unique expansion methods/joints will have to be incorporated not only on the towers (both ceramic internal and steel external) but also on all connected piping, ladders, accessories and structural components.

5) Seismic and wind loading: you’re going to have Hell to bargain with if you’re in seismic country and all I can say on this point is go with God and pray that you can hire/contract a mechanical genius that will get you safely out of this quandary.

6) The internals of the tower will have to be impervious, ceramic brick work that is stacked, but free to expand and support itself. You may have to contract special forms cast for you. Your 2,400 oF is mystifying and very demanding at the top. Are you cooling/scrubbing in a downward, co-current manner? This is very important because it sets the sequence and the correct way to allow for the inevitable expansion requirements.

7) You surely must allow for yearly maintenance and repairs. What this means is that you must build into your design a credible, safe, and efficient manner of getting into the tower for inspection and, ultimately, for packing removal (Yikes!)

8) You must consider the possibility of the tower getting plugged with solids deposited from the cooling water used for scrubbing. That may mean that you will require a closed, circulation water system with large cooling requirements.

9) Any H2S, O2, or other acid gases in the flue will eventually get absorbed or entrained in the cooling water being recirculated and will be potential corrosion agents – especially at the elevated temperatures.

10) If your tower is going to be operating year-round, you will be required to monitor the annulus space between the internal, wetted wall and the external steel wall for leakage. One way to do this is to impose a positive-pressure, N2 blanket in the annulus.

Well, the above is all that I have for now, but not all that will be required to resolve. I think you are better aware of this “challenge” than anyone on this Forum. Certainly, you have more vested interest in it. I’ll close for now, try to recollect more important points from my experience, and let others on this Forum contribute what they can. Hopefully, someone has done this very application already.


Art Montemayor
Spring, TX