gas evaporator question

[prairietapper]

Hi everyone. I hope I am not asking a question that has been asked 1000 times before. I did try to use the sites search feature to find what I am after but have had no luck. so if someone can provide a link or other good input either are highly appreciated! In the past I converted a oil fired 2x4 with drop flues to natural gas. the arch has a ramp that starts about 1/3 of the way to the back of the flue pan. I am not at all happy with the boil I am getting. Oh I can throw enough heat at it.. that is not the problem. the problem is getting it even across the run of pan. the burner I am using is from a small grain dryer. I am seriously considering building a new arch but would like to see how the inside is laid out on natural gas on new evaps. are they using a big burner or pipes like on a finisher ? again any help would be greatly appreciated. I love the money saved in season over fuel oil. but I am not happy with the rates I can get with out scorching somewhere. I did warp the pan a touch from uneven heat. but it is still serviceable. I am not sure it will take another screw up like that one lol again I am thankful for any input you can give me.

[maple flats]

When firing on either propane or natural gas, tube burners are best, but large burners like on a turkey fryer will work. In either case, the burner should be about 7-8" below the pan. That will work good on the flat pan, but with the drop flues, you will want the burner that much lower so it is also at the 7-8" below the pan. When using either gas, it would be far simpler to have a raised flue set-up.
If you make your own tube burner, have 2 different heights and only have the gas holes under the appropriate pans. If building your own, you still need factory gas valves with air mixing adjustments to get the right flame, plus you must have the right size gas orifice, those two gases are at different pressures.

[prairietapper]

Thank you Maple flats. that meshes with what my experimentation has led me to think would be best.
if the flames are all orientated up to the pan. and not horizontal is there any real reason to use fire brick in the bottom and sides? or would ceramic blanket to hold the heat in be enough?

[upsmapleman]

Not sure how you boiled with oil. Did you have a gun of sorts. Natural gas guns work similar to a oil gun. Not sure you would find something small enough for a 2x4 unless you used a home heating gun.

[prairietapper]

yes it used a fuel oil gun from a large residential boiler. the gas burner I switched to is also a gun of sorts

[maple flats]

They don't normally use brick in gas fired units, more often use ceramic blanket or ridged ceramic insulation. Some will however use brick. The main thing is to minimize the heat loss to get more heat to the pans.

[mellondome]

Gas doesnt need fire brick. Fire brick is only needed with wood because wood will tear up blanket. I use ng for my 2x6. I use torch/torpedo style burners.

New gas arches use burners that are converted oil burners. They are fired from the back side so that the flame starts at the front of the pan. The same arch as oil burners.

Not sure what you have for burners in your arch, but you will need an autodamper in your stack.

[prairietapper]

thank you for the input folks!