NG Jet Burner Flame Color

[gbrewing]

I test fired my new brewing system and have an issue I need help resolving. The system has a 23 tip jet burner for the Boil Kettle. The burner runs on natural gas. Prior to this, I had a 23 jet propane burner so I am somewhat familiar with how they operate.

I recently split my main gas line coming to the house and branched off with a 1" line from my main meter to my shop. The gas engineer told me I should have adequate gas supply for the burner and my has water heater (which is also in the shop) The plumbing inside the shop for the inside line is 1/2" with 1/2" valves which are full port. The quick connectors are also true 1/2".

I test fired the burner tonight with a flame height I was comfortable with. (not nearly full open). The temperature of the water started at 82 degrees and rose to 100 degrees in 10 minutes. It was 20 gallons of water. (Not sure what the BTU rating for this would show)

When I started the burner, the burner flames were nice and blue with a little bit yellow. It wasn't leaving a carbon behind on the kettle. After about 6 - 8 minutes, the burner flames turned more yellow than blue and I noticed carbon on the bottom of the kettle.

It is my understanding that a burner that is yellow in color will leave a black carbon residue due to the incorrect mixture of oxygen into the flame but I am uncertain how to resolve this issue.

Could it be based on not having enough makeup air for the burner? The only other appliance that could have turned on during this time frame was the gas water heater to the house. It is not on the same line but feeds at the split. My gas water heater in the shop was on vacation mode at the time and not actively heating.

I opened the gas valve wider and was able to get a more "jet" type of a flame which was blue in color. It was a very aggressive burn and more than I wanted to use.

My thought for fixing the issue would be to limiting the actual jets in the burner by plugging several with the appropriate size plugs. I do, however, need enough btu's to boil up to 42 gallons.

Thoughts?

 

[microbusbrewery]

How about a pic of your setup? My initial thought is you may have an issue venting combustion gases, so it's essentially starving for air. But that's just a guess without seeing what it looks like.

 

[gbrewing]

How about a pic of your setup? My initial thought is you may have an issue venting combustion gases, so it's essentially starving for air. But that's just a guess without seeing what it looks like.

Your explanation makes very good sense based on how I have my new setup. I used to brew with converted kegs and a completely different stand. The converted kegs have the "skirt" around the bottom which include vents on all four sides.

My new stand is essentially 1 1/2" square tube which the kettle sits directly on top of. The boil kettle is a Blichmann boilermaker. After looking at it, it sits rather flat on the stand and doesn't allow the gasses to flow up around the sides. The gasses hit the bottom and would be forced to "reflect" back down over 1 1/2" steel prior to flowing out the side. After your explanation, it almost sounds like the gasses are not escaping as they should and could be causing the "starvation" of air.

I think a simple solution would be to weld on some 1" steel in various areas to create "blocks" for the kettle to rest on. This would allow better venting of the exhaust gasses.

 

[microbusbrewery]

Yep, that's an issue I ran into on mine as well. I test-fired without the kettle and I had nice blue flames with a touch of yellow. Once I added the kettle I got a lot of yellow and some soot. I welded on 1/2" diameter round rod to lift the kettle off the frame a bit, and that solved the issue.

 

[gbrewing]

I placed the blocks under the kettle as a "sample" for venting. It seems to keep the flame in better shape. I am now a bit concerned I may have the burner a bit low for the kettle. What was your distance from the tip of the burner to the base of the kettle?

 

[Bobby_M]

No, you have the distance about right. One of the reasons those burners get fouled up and orange is that your spent gases (CO) build up around the base of the burner tips which is where the oxygen comes in for the burn. I haven't experimented with this next theory, but I believe that a putting a sheet metal ring around your burner base, just under the burner itself, extending down about 4" would help by pulling fresh air into a column that would push spent gases out of the way. It's a chimney effect basically. Worth a shot with some aluminum foil.