3 replies to this topic

[vinay]

Dear Friends,

We have a low pressure Hydrocarbon (propylene) vent in our plant (used for venting leaked gases from compressor packings) which is elevated at ~ 5 mtr height, though steam is put at the the vent we have observed that the ground concentration of Propylene is significant ( some time 25% of LEL) & it creates a lot of smell in that area apart from creating an hazardous situation at high venting rates.

Does anyone has any experience in these kinds of stacks design or couuld tell me Which code/site to refer for such application ?

Regards,

Vinay

[mbeychok]

Vinay:

You should not be venting propylene (which is considerably heavier than air and very flammable) to the atmosphere in your plant under any circumstances!!

If your plant has an emergency relief/flare system, I strongly suggest that you route that propylene into that flare system. If you have no such flare system, then I suggest you install a flare into which you can route the propylene. If you do not route that vent to a flare, sooner or later you will have a disaster on your hands.

[vinay]

Dear Mr. Milton,

Thanks for your reply on the subject. I agree with you that Propylene by principal should not be vented to atmosphere, However with our compressor type it is not posssible to vent it to flare as the compressor crank case can not handle the back pressure of flare & upgrading the compressor is very expensive.

Regarding the disaster point of view , please note that the vent flow is moderate (~200 Kg/hr) & the concentration of propylene in it is very low as well (~ 5- 10 Kg/hr) , morever we are putting steam to disperse off the gases (its a different issue that we can still smell the propylene at ground with our vent stack height). Is there any way to calculate the stack height so that ground concentration becomes small enough no to cause any considerable proble of odour/LEL ?

Regards,
Vinay

[mbeychok]

Vinay:

You say that the vent flow is 200 kg/hr and it contains 5-10 kg/hr of propylene. What is the remaining 190-195 kg/hr? Is it some other hydrocarbons? Since you say that it has an odor, I suspect that the remainder must include some hydrogen sulfide or some mercaptans ... is that correct? Have you got a complete component analysis of the vent gas?