Estimating REACTION Rates for Relief Device
Estimating REACTION Rates for Relief Device
(OP)
I am interested in the various methods you all use to obtain reaction rates for sizing relief devices; particularly what general methods can be applied that result in safely over-sizing a valve if physical properties are limited and testing is not immediately available (similar to the way API allows the sizing of a tank based on HEXANE in the absence of detailed physical properties).
The methods I have used include:
1. Actual test lab data
2. Using theorectical heat of reaction
3. OTHERS????????????? RULE OF THUMB FOR SAFE OVER-SIZING????
The methods I have used include:
1. Actual test lab data
2. Using theorectical heat of reaction
3. OTHERS????????????? RULE OF THUMB FOR SAFE OVER-SIZING????
The more you learn, the less you are certain of.





RE: Estimating REACTION Rates for Relief Device
Sizing a relief device is to prevent any dangerous event from occurring. Therefore process design of the equipment and process operating limits have to be considered.
There are 2 sides of a coin
One is to give, one is to take
Give until it hurts with a smile
RE: Estimating REACTION Rates for Relief Device
The more you learn, the less you are certain of.
RE: Estimating REACTION Rates for Relief Device
I see what you want to do. You want to size the relief so that your vessels are covered for a general runaway reaction. I don't know of anyone who has figured that one out. It would be nice. The DIERS group (Design institute for emergency relief systems) has a book called Emergency Relief System Design Using Diers Technology. They have done a lot of work on relief systems for runaway reactions. They reccomend lab data and have a piece of equipment that they put your sample in to get the parameters needed for thier sizing calcs. (They have software too) You may be able to read their book and incorporate it into what you are doing. I think we got thier book from AICHE online.
Good Luck hope this helps some.
RE: Estimating REACTION Rates for Relief Device
The more you learn, the less you are certain of.
RE: Estimating REACTION Rates for Relief Device
Where in API does it allow you to use hexane? What about chemicals that contain hydrocarbon fractions? Can or should you use the lightest components or the heaviest or an average?
Thanks!
RE: Estimating REACTION Rates for Relief Device
The more you learn, the less you are certain of.
RE: Estimating REACTION Rates for Relief Device
Assuming we are talking about API tanks exposed to fire without reaction as a possibility in addition to fire exposure: If you have the physical data (latent heats, etc.) on the components of a liquid mixture you should determine the combined physical properties if they do not separate prior to reaching the relieving pressure . If you have high boilers that will boil off before you reach the set pressure, then you need to treat this separately and determine the required release rate for each fraction coming off as a vapor. I also try to estimate the length of time that a release will occurr for a specific fraction. This is important to know for reacting to the dispersion of vapor that may occur if not separately treated and also for evaluating the release versus the expected response time for corrective action by humans. I hope I interpreted your question correctly.
The more you learn, the less you are certain of.
RE: Estimating REACTION Rates for Relief Device
I have seen a lot of work on sizing relief devices for a "dump" system in a HNO3/Organic Process. Most of the work I am familiar with was done with Mathcad, but I also know this person used Mathematica also. Don't know if has published it or not.
www.efunda.com for Mathematica
www.mathsoft.com for Mathcad