Burner Choking Issue in Furnace

qwasif
Posts: 3
Joined: Thu Apr 06, 2017 10:52 am

Burner Choking Issue in Furnace

Post by qwasif » Fri Nov 15, 2019 7:17 am

We have Side Wall furnace installed at our Haldor Topsoe Ammonia Plant. It has approx. 720 burners installed. We are currently facing frequent issue of burner choking due to dusty atmosphere.
Currently burner cleaning regime on daily basis is being followed in which burner is removed and cleaned through wire brushes. This process overall hampers efficiency of furnace and also additional men power is required.

Any better regime that is being followed in any of the furnaces installed on ammonia plant in the world to mitigate this issue?

gschulz
Posts: 10
Joined: Thu Apr 06, 2017 10:52 am

Re: Burner Choking Issue in Furnace

Post by gschulz » Tue Nov 19, 2019 5:46 pm

Dear Qwasif, the type of burner is very important.wWe have experience with Hamworthy (small holes at tip) and John Zink models (slits instead of holes). there are mesh supplements that can be put external to the aire intake that would filter the bigger particles, But if it is fine dust, you will have to consider the burner tip model, and look for options. We have idenfitied the prevalent wind direction and the wall that is impacted is having a higher frequency of cleaning. However all cleaning is based on measuring O2, CO, With a portable TESTO chromatograph, and only we there is no remanent air register to compensate for increased pressure drop at burner tip, while keeping the CO at low level ( ideally less than 1%), we remove the burner for cleaning. Best regards, Gaston Schulz

qwasif
Posts: 3
Joined: Thu Apr 06, 2017 10:52 am

Re: Burner Choking Issue in Furnace

Post by qwasif » Fri Dec 06, 2019 8:12 pm

Thanks Gschulz for your response.. We have the Hamworthy (small holes at the tip) burners installed at our furnace. We are also thinking of installing meshes supplements on our furnace, even we have done a test run as well and it remained quite successful. However the burner choking cant be completely eliminated even after installing the meshes.

I would request if you can elaborate a bit more on the following with your experiences.

1) Can you share any of the burner tip model change experience (like the John Zink model) if you guys have done at your furnace?
2) What is the size of meshes that are installed on your furnace? and the cleaning mechanism that is being followed at your site?
3) Can you further elaborate on the burner choking identification procedure because at our site we measure the burner velocities on the air register inlet. Wherever the burner velocity is less than our defined limit we ask our maintenance team to clean that specific burner.

Waiting for your kind response in this regard.

Thanks and Regards,
Qazi Wasif ud Din

gschulz
Posts: 10
Joined: Thu Apr 06, 2017 10:52 am

Re: Burner Choking Issue in Furnace

Post by gschulz » Wed Jan 29, 2020 8:15 pm

Dear Mr Qazi Wasif ud Din,

we operate simultaneously HW and JZ (dual fuel). In our experience HW last longer before requiring a clean up, mainly because they do not need, at same location, so much pressure drop at air intake (register) to control the air flow. Eventually allof them require cleaning...

We do not use external mesh, though. Most of the fouling is due to very fine dust and would no be retained there.

Measuring air intake speed is somehow difficult since the is is constantly fluctuating, but it is still used as one of the measurements to monitor performance, and identifiy which ones require cleaning.

In our experience we meaure directly the amount of CO slip at fluegas and ensure that it remains below 10ppm at most. If necesssary we open the air register a bit. if you have exhasuted all control reserve at the air register and still cannot achieve less than10 ppm CO, then we remove this burner for cleaning at once or light it off until it is cleaned.

However, when you do a complete survey of the burners, then is is relaltively simple to identify by comparison which are using more air regsiter to get the desired CO slippage and minimum O2 excess (typically we aim at 1-1.5%). those are to be programmed for cleaning.

Chocking is in my opinion, not only a consequence of burner fouling. low air intake mya also be due to improver dfraft profile at that row , which could be solved by adjusting the ID Fan damper, or eventually adjusting the whole fire profile.

When you measure CO and O2 you are dealing with the key parameters of combustion. your main concern is safety: avoidance of falme impingement and post combustion. Air flow is an indirect measurement, surely necessary, but most probably insufficient. I recommend that you try a TESTO portable chromatograph. It is not so expensive and very easy to use.

best regards,

Gaston Schulz

PKS1964
Posts: 14
Joined: Thu May 17, 2018 3:52 pm
Contact:

Re: Burner Choking Issue in Furnace

Post by PKS1964 » Sat Jun 06, 2020 3:48 am

Friends Hi,
We are also facing frequent chocking of burner tip, The chocked material is white in colour, some time it hard also. Have you analyse deposit material, what is the source of deposit.
What is the net hydrogen and NH3 going to reformer as fuel. This is one possibility that NH3 mixed with CO2 present in gas formed carbamate and depsoit on tips.
Regd
Prabhat

bedmonds
Posts: 26
Joined: Thu Apr 06, 2017 10:52 am
Contact:

Re: Burner Choking Issue in Furnace

Post by bedmonds » Sat Jun 06, 2020 12:39 pm

Hi,
Temperature is a key factor. As an example, with 1% CO2 in mixed fuel at 3 bar(g) the NH3 content at which carbamate is stable is roughly:
25 deg C 1.7% NH3
40 deg C 7.1% NH3
55 deg C 30 % NH3
If the fuel is preheated with a steam heater for convection bank coil it would seem that carbamte formation is unlikely. An interesting problem and hopefully others will have some thoughts.

PKS1964
Posts: 14
Joined: Thu May 17, 2018 3:52 pm
Contact:

Re: Burner Choking Issue in Furnace

Post by PKS1964 » Tue Jun 09, 2020 4:11 am

Hi,
In our plant we are also using Urea plant MP section gas to reformer as fuel that have ammonia < 0.4%. Other source of ammonia is off gas coming from recovery section. That also have ammonia < 1%.
Temperature of fuel (Combination of NG fuel+ Surplus gas+ Off gas+ PGRU tail gas) that is going to reformer is @ 85 to 90 degc.
Is it possible of carbamate formation at 85 degc fuel gas.?

bedmonds
Posts: 26
Joined: Thu Apr 06, 2017 10:52 am
Contact:

Re: Burner Choking Issue in Furnace

Post by bedmonds » Tue Jun 09, 2020 12:17 pm

Hi, At least by my method, which could be wrong, I have, for 5 bar fuel gas and 1% NH3, to have stable carbamate CO2 in gas is:

20 deg 0.8%CO2
30 deg 2.7%CO2
40 deg 35 %CO2
So I don't think carbamate is an issue however ammonium carbamate is a salt and ammonia and CO2 can also make ammonium varbonate and ammonium bicarbonate. I have the phase diagram somewhere and will see if I can finds it. An interesting problem.

PKS1964
Posts: 14
Joined: Thu May 17, 2018 3:52 pm
Contact:

Re: Burner Choking Issue in Furnace

Post by PKS1964 » Fri Jun 12, 2020 10:51 am

Dear Bedmonds,
I have detail workout on this reformer tip chocking by white material.
My gas composition
1- NG 13000 Nm3
2- Surplus gas ( Syn gas, excess gas send to reformer) this have rich H2 @ 73%,
3- Off gas, flow is 17000 Nm3 @ H2 33% Ammonia 0.2%
4- PGRU Tail gas that have almost inerts and few % of H2
If calculate total H2% it is around 47%, In view of this CO2 ( which is coming from NG) is almost very less %
With this combination what is the reason for burner tip chocking and why white material appear.
We also did lab analysis they not confirm Carbamate.
Is there is any possibility of silica/ Alumina deposit which is presence in refectory.

Somalanka8
Posts: 1
Joined: Mon Jun 15, 2020 2:48 pm
Contact:

Re: Burner Choking Issue in Furnace

Post by Somalanka8 » Mon Jun 15, 2020 2:55 pm

PGRU tail ga will be joined by adsorbers regeneration gas. So material slippage chance is there from adsorbers while regeneration time. so please check for silica and alumina..

Post Reply