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Steam is purged into flares for somkeless operation. Steam also reduces the radiation from the flare flame. But can I purge nitrogen instead of steam. Cost of nitrogen is anytime higher than steam but lets say I have abundant of nitrogen and the availability of steam is limited then in this case can nitrogen be purged or not.
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Purging In Flare Systems
Started by Firoz Raja, Apr 25 2006 06:51 AM
4 replies to this topic
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#2
Guest_Profe_*
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Posted 25 April 2006 - 11:54 AM
Hi Firoz Raja
The next are a few tips for your Flare system.
Smokeless burning and chemistries.
1. Major factors for smokeless operation:
A. Securing a combination of carbon with another element
B. Significantly upgrading the H/C ratio by weight.
2. Chemistries:
If carbon can be made to combine with oxygen as either CO or CO2, the carbon cannot be seen and thus produce no smoke.
CH4 + H2O = CO + 3H2
CH4 + 2H2O = CO2 + 4H2
C + 2H2O = CO2+ 2H2
All reactions are endothermic.
3. Smoke suppression methods
a. Steam injection (your case)
b. High pressure gas injection.
c. Low pressure air
d. Internal energized flare.
4. Steam injection type
Steam requirements are from 0.2 to 0.4 pounds of steam per pound of hydrocarbon
Designed smokeless for relieving rates that may be expected.
Smokeless operation for refinery emergency is not usually designed for smokeless operation because of high steam flow necessary.
5. Tendency to produce black smoke in flare burning of Hydrocarbons as influenced by the H/C ratio by weight of the flared gases where there is no suppression of smoking.
6. Steam flow can be obtained from the manufacturers of the flare tip or can be estimated from the following equation:
Lbs steam= lbs HC* [0.68 - 10.8/mw]
Smokeless operation can be expected only for reasonable flows which may occur for long periods.
If your Flare was designed to use steam for smokeless burning, You would be try the steam flow until find the optimal steam consumption in normal operation of your flare system.
I hope to be useful to you.
The next are a few tips for your Flare system.
Smokeless burning and chemistries.
1. Major factors for smokeless operation:
A. Securing a combination of carbon with another element
B. Significantly upgrading the H/C ratio by weight.
2. Chemistries:
If carbon can be made to combine with oxygen as either CO or CO2, the carbon cannot be seen and thus produce no smoke.
CH4 + H2O = CO + 3H2
CH4 + 2H2O = CO2 + 4H2
C + 2H2O = CO2+ 2H2
All reactions are endothermic.
3. Smoke suppression methods
a. Steam injection (your case)
b. High pressure gas injection.
c. Low pressure air
d. Internal energized flare.
4. Steam injection type
Steam requirements are from 0.2 to 0.4 pounds of steam per pound of hydrocarbon
Designed smokeless for relieving rates that may be expected.
Smokeless operation for refinery emergency is not usually designed for smokeless operation because of high steam flow necessary.
5. Tendency to produce black smoke in flare burning of Hydrocarbons as influenced by the H/C ratio by weight of the flared gases where there is no suppression of smoking.
6. Steam flow can be obtained from the manufacturers of the flare tip or can be estimated from the following equation:
Lbs steam= lbs HC* [0.68 - 10.8/mw]
Smokeless operation can be expected only for reasonable flows which may occur for long periods.
If your Flare was designed to use steam for smokeless burning, You would be try the steam flow until find the optimal steam consumption in normal operation of your flare system.
I hope to be useful to you.
#3
Guest_Profe_*
Guest_Profe_*
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Posted 27 April 2006 - 05:05 PM
Hi Firoz Raja
More about Smokeless Flares
A flame is referred to as being luminous when incandescent carbon particles are present in it. When these particles cool, they form smoke. Several theories have been presented to explain the formation of smoke, but none has been fully established. However, it has been observed that smoke formation mainly occurs in fuel-rich systems where a low hydrogen-atom concentration suppresses the smoke.
Prevention of smoke in flares is normally accomplished in three different ways:
1. By the addition of steam.
2. By making a pre-mix of fuel and air before combustion so as to provide sufficient oxygen for efficient combustion (which is always done in fired boilers and furnaces).
3. By distribution of the flow of raw gases through a number of small burners.
Among these methods, the addition of steam is most commonly used to produce a smokeless flare for economy and superior performance. In steam addition, the raw gas is preheated before it enters the combustion zone of the flame. If the temperature is high enough, cracking of the hydrocarbons may occur. This produces free hydrogen and carbon. When the cracked hydrocarbons travel to the combustion zone, hydrogen reacts much faster than carbon. Unless the carbon particles are burned away, they cool down and form smoke. Consequently, in order to prevent smoke, either the hydrogen atom concentration must be decreased to ensure uniform burning of both hydrogen and carbon or enough oxygen must be provided for complete combustion.
There are several theories as to the chemistry of smokeless flares using steam. One of them assumes that the steam separates the hydrocarbon molecules, thereby minimizing polymerization reactions, and forms oxygen compounds that burn at a reduced rate and temperature so as to prevent cracking.
Another theory claims that steam reacts with carbon particles forming carbon monoxide, carbon dioxide, and hydrogen, thereby removing thee carbon which forms smoke after cooling.
Bibliography:
Banerjee, K. “Flare gas systems pocket handbook” p. 12-13. 1985 by GuIf Publishing Company, Houston, Texas.
I hope to be useful to you.
Fausto
More about Smokeless Flares
A flame is referred to as being luminous when incandescent carbon particles are present in it. When these particles cool, they form smoke. Several theories have been presented to explain the formation of smoke, but none has been fully established. However, it has been observed that smoke formation mainly occurs in fuel-rich systems where a low hydrogen-atom concentration suppresses the smoke.
Prevention of smoke in flares is normally accomplished in three different ways:
1. By the addition of steam.
2. By making a pre-mix of fuel and air before combustion so as to provide sufficient oxygen for efficient combustion (which is always done in fired boilers and furnaces).
3. By distribution of the flow of raw gases through a number of small burners.
Among these methods, the addition of steam is most commonly used to produce a smokeless flare for economy and superior performance. In steam addition, the raw gas is preheated before it enters the combustion zone of the flame. If the temperature is high enough, cracking of the hydrocarbons may occur. This produces free hydrogen and carbon. When the cracked hydrocarbons travel to the combustion zone, hydrogen reacts much faster than carbon. Unless the carbon particles are burned away, they cool down and form smoke. Consequently, in order to prevent smoke, either the hydrogen atom concentration must be decreased to ensure uniform burning of both hydrogen and carbon or enough oxygen must be provided for complete combustion.
There are several theories as to the chemistry of smokeless flares using steam. One of them assumes that the steam separates the hydrocarbon molecules, thereby minimizing polymerization reactions, and forms oxygen compounds that burn at a reduced rate and temperature so as to prevent cracking.
Another theory claims that steam reacts with carbon particles forming carbon monoxide, carbon dioxide, and hydrogen, thereby removing thee carbon which forms smoke after cooling.
Bibliography:
Banerjee, K. “Flare gas systems pocket handbook” p. 12-13. 1985 by GuIf Publishing Company, Houston, Texas.
I hope to be useful to you.
Fausto
#4
Firoz Raja
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- 15 posts
Junior Member
Posted 02 May 2006 - 01:01 AM
Dear Mr Fausto,
Thank you very much for your kind reply. Your inputs indeed are very much informative and helpful to me.
Thanks again.
Firoz
Thank you very much for your kind reply. Your inputs indeed are very much informative and helpful to me.
Thanks again.
Firoz
#5
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- guestGuests
- 0 posts
Posted 06 June 2008 - 07:02 PM
Hi everybody,I have to improve an existing smokeless system (which use ultrasonic transmitter, pressure/temperature for mass flow with molecular weight outpout) on steam control. The existing one is not reliable. In the future it will become more complex: two branch going one one header, each brach having its own flowmeter (same setup as mentionned above). I'll use the Lbs steam= lbs HC* [0.68 - 10.8/mw] but I think that adding an remote temperature reading (like JZ ZOOM) in cascade on steam flow controller will be the best option.Any ideas?
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