Sizing a SRV for a ClO2 Heater

[pianoman1]

I'm designing a system to heat Chlorine Dioxide with hot washer effluent at a local paper mill. The heater is an all-titanium shell and tube heat exchanger, effluent on the tube side, ClO2 on the shell side. We'll be heating ClO2 to about 115F, which is near the safe limit before it 'dis-associates'.

To protect the shell (225 psig MAWP), I can easily account for liquid flow through the safety relief valve, the pumps dead-head at ~200 psig. I'm curious about how to size for two other possibilities - external fire and 'dis-association'. External fire of the 'pool fire' type is unlikely - this is a washer building with very little flammable stored or construction materials. But auto-reactivity might be another problem. I'm mechanical and remember enough Chem Engr to be dangerous. Is there a way of determining potential reactivity and/or vapor generation rates at a given temperature and then determine the vapor that would need to be relieved to keep the vessel within MAWP? Am I even on the right track? The max temperature the ClO2 would see, minus a fire, would be 160F. I understand it starts to get very unstable at about 125F.

Thanks for any feedback.

 

[cloa]

Isn't it ClO2 in solution since ClO2 gas has strong tendency to explode (over 30% in air) ? If so what concentration?

http://www.eng-tips.com/threadminder.cfm?pid=1529

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[pianoman1]

It is 11 g/l ClO2 in solution. My understanding is that above about 125F, chlorine gas begins to off-gas in an exothermic and sometimes violent reaction. My questions are - is that true, and if so, how do I predict the rate at which it happens so I can size a relief valve to accomodate it.

 

[cloa]

This information on CLO2 is relevant.

http://www.archpatent.com/patents/2683651

http://www.eng-tips.com/threadminder.cfm?pid=1529

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[pianoman1]

cloa - thanks for your response, although that applies, it doesn't directly answer the question. Any other help? Thanks.