Heat generation in waste compactors 2

[chemicalseddon]

I am looking at whether the heat generated by compression within a waste compactor would be sufficient to reach the autoignition point of pentane used as a blowing agent in insulation board. The waste cut offs are compacted and whilst I suspect fires in the compactor are caused by compression heating of the pentane I need to prove this. I hated thermo at college - can anyone tell me how to go about calculating this? Is it as simple as PV=nRT?

 

[dcasto]

It's hard to believe, but yes you can generate enough heat to cause pentane to ignite, it's called a Diesel Cycle engine. Pentane would auto ignite in an engine at about 9 to 1 compression ratios. There are lots of factors that may be worth exploring for a solution as a way to inhibit the auto ignition.

A large chemical plant caught on fire in Europe in the '80s as a result of commisioning a pressure gauge in the plant. The operator purged the bordon tube gauge with nitrogen, so no air. As he purged a small amount of the gas in the line to also assur no air was introduced. He then opened the valve that let the gas at 800 psig into the gauge. The nitrogen compressed and its temperature went to above 800F and the gas started to decompose and auto-burn.

 

[25362]

The temperature rise by compression can be estimated by the adiabatic equation:

T_final = T_initial (P2/P1)^(n-1)/n​

n = Cp/Cv; for air ~ 1.4; for pentane is lower depending on P,T.

A rise in temperature may initiate spontaneous (exothermic)autooxidation eventually leading to autoignition of the impregnated insulation boards.