combustion pressure

[nuche1973]

Greetings,
I have posted this question in the mechanical engineers' forum. However, I'd feel that it may be more applicable here since it is product specific. What is the maximum combustible pressure for gum arabic? I am checking a design of a dust collector and gum arabic is the product collected. The collector is to meet NFPA 69 standards, which is the origin of the question. Any information, vaules, or leads will be greatly appreciated. Thanks.

 

[Bribyk]

Check out NFPA 68.

 

[nuche1973]

Bribyk,
I assume that you are referring to Table T.B. 1.2.4 Hazard Classes of Dust Deflagrations, correct?

 

[Bribyk]

I don't have it in front of me right now but it should have the info needed to approximate gum arabic's deflagration properties based on flame speed, etc...

 

[nuche1973]

Thanks for the lead. I appreciate it.

 

[Bribyk]

I had a quick look and didn't see gum arabic in NFPA 68's appendix tables. I'd still recommend you get a copy of it though. The highest peak combustion pressure for a non-metal dust in NFPA 68 is 10.8 barg (most are 8-10 barg). It looks like you may have to keep looking for a reference or get your dust tested.

 

[owg]

Gum Arabic combustion characteristics are listed on my 1978 copy of NFPA 68, page 68-41, Appendix E, Table E-1, Combustion Characteristics of Various Dusts.

For gum arabic the following are listed. This only applies to a dust passing through a No 200 US Standard size sieve at a concentration of 0.50 oz per cu ft, see Bureau of Mines R.I. 5624 (1960)

Ignition temp of dust cloud 500 deg C
Min spark for ignition 100 joules
Min explosive conc. 0.060 oz/cu ft
Max explosion pressure 84 psig
Max rate of pressure 1500 psi/sec
Dust Classification ST-1

HAZOP at

http://www.curryhydrocarbons.ca

 

[Compositepro]

I did calculations many years ago when I was involved in chemical plant process safety. For most hydrocarbons max combustion pressure is at stoichiometric proportions with air and the max pressure will be close to 150 psi (10 bar, or actually 10 times initial pressure). This assumes adiabatic conditions, moles of reactants versus moles of reaction products. The nitrogen in air is a big factor in the limit.

However, shock waves could cause higher local pressures.

 

[nuche1973]

Alright, thanks guys...had to did out my chemistry book to translate I appreciate the information.