Flashing losses in refineries

[barqueiroenmarte]

Dear all,

I am preparing an initial report describing the emissions due to storage tanks (crude, intermediate products, final products) in refineries. I am considering working and standing losses and I am looking for information about flashing losses but everything I find regards to Exploration and Production (not refining). Are those losses usually negligible in refineries or must be considered in some situations? Any information?

Thank you.

 

[ash9144]

I assume since you mention storage tanks that you are referring to breathing losses. Which is normal vapor loss from a tank during the course of a day. And no these are not negligible.

In order to determine a number you need to evaluate each vessel or at least type of vessel and determine the vent system it has. The type of vent will greatly influence the amount to atmosphere. For instance a vacuum tank should have no emissions from breathing whereas a tank open to atmosphere would lose whatever evaporated from the liquid.

Sorry no easy way out.

 

[mbeychok]

barqueiroenmarte:

Are you aware of the publication by the U.S.A. Environmental Protection Agency (U.S.A. EPA) known as "AP 42, Compilation of Air Pollutant Emission Factors"? Chapter 7 of Volume 1 of that publication is entitled "Liquid Storage Tanks" and includes the methods for calculating the vapor emissions from all types of tanks. The U.S.A. EPA also makes available a downloadable software program called "Tanks" which does the calculations for you.

Read this Wikipedia article to learn more:

http://en.wikipedia.org/wiki/AP_42_Compilation_of_Air_Pollutant_Emission_Factors

The "References" section of the above article has links to the online AP 42 publication as well as to the Tanks program.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[barqueiroenmarte]

Thank you for your help. For flashing losses I refer to the losses which occur when a hydrocarbon goes from a higher to a lower pressure. I attach a link to a web explaining that:

http://www.deq.state.ok.us/factsheets/air/CalculationLosses.pdf

Do they happen at refineries?

Regards

 

[bimr]

mbeychok has already provided you with the answer to your general question. You may either obtain the information from the suggested sources or take an air pollution control course at your local university.

Air emissions from refineries are regulated by the EPA and much work has been done over the years to limit the emissions to the environment. There are not any uncontrolled flashing emissions. Emissions are typically vented to an air pollution control system that greatly reduce the amount of material discharged to the environment. The materials captured by the air pollution control system may be recycled back to the process.


Here is another source of information:

http://www.socma.com/Issues/issues/air.htm

 

[mbeychok]

barqueiroenmarte:

There are dozens and dozens of closed systems in a refinery wherein a saturated liquid is reduced in pressure and which then results in partial evaporation (called "flashing") of the liquid. But such operations are all in closed systems and are part of a process operation. There are no "losses" or emissions from such closed systems.

Flashing does not occur in storage tanks unless a liquid stored at high pressure accidentally escapes into the ambient atmosphere through a leak. For example, if an LPG tank or a liqufied ammonia tank or a liquified chlorine tank has a leak. But that isn't a normal operational emission ... it is an accidental release.

If you want to learn more, read this article:

http://en.wikipedia.org/wiki/Flash_evaporation

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[owg]

barqueiroenmarte:
In a refinery we do not intentionally have any flashing losses. You have restricted your question to storage tanks so I think you need only estimate breathing and working losses from storage tanks. Flashing from refinery storage tanks can be assumed to be neglibible.

HAZOP at

http://www.curryhydrocarbons.ca

 

[techv]

Well, emissions are normally limited to working and breathing losses. But, after reading Barqueiroenmarte's posting (the link), learnt that flasing losses also estimated in some cases. There is a graph with pressure (psig) and production (bbl/day)to to decide whether to estimate the flash losses. BTW, I do have a question here. What exactly this pressure is?? Is it delata-P between source pressure and storage tank pressure?

Regards

 

[dcasto]

The Beggs Vasquess (sic)(BV) excel based equation will give a middle of the road answer on ther mount of losses. A detailed process analysis will give a more detailed result.

 

[drvadose]

DCasto gives you the answer we have been using in several air districts in California. Generally, the EPA Tanks4 (now in version 4.09 as of this writing) accounts for breathing (standing) losses and working losses. It has a capability for flashing losses, but using it is not preferred by a few local agencies. I don't know why and I've not done any comparisons myself.

Instead, I use the BV method to estimate flashing for both air permitting and for annual SARA Tier I/II reporting (and we have California AB2588 reporting requirements to meet as well).