4 replies to this topic

[Daniel C]

I am currently working on an emissions abatement project that will  involve extracting vapor streams of Volatile Organic Compounds from various tanks and sending them to a Regenerative Thermal Oxidizer (RTO) for incineration before discharge into the atmosphere. The tanks/vessels will be inerted with nitrogen and the excess waste vapor fumes will vent into the pipe headers and sucked to RTO by fans. 

 

My concept design incorporates the use of  standard Nitrogen Padding & Depadding Valves, Flame/Detonation Arresters, Oxygen Analyzers / LEL Detectors, Pressure-Vacuum Reliefs, Explosion Reliefs etc. I would welcome any advice on anything else I should consider in the project. 

 

How best can I predict the maximum volumetric flows and the Nitrogen and VOC components concentrations on the main header prior to the RTO.

Attached Files

•  VOC Abatement Drawing2.pdf   115.42KB   67 downloads

[AlertO]

Hi daniel

Your venting system is air free, right?
If no, you may need to check the LEL of individual header to ensure the vapour mixture is at lower than LEL. Normally RTO vendor will provide only one senser at the RTO inlet.
Just would like to share the idea. Have a good day.

[Daniel C]

Thanks AlertO

Yes the desire is to operate with no O2 or at O2 concentration lower than the LOC of the vapors. As such I am looking at having an O2 Analyser to monitor the vapor collection header prior to the RTO.

[Art Montemayor]

Daniel,

 

You’ve got a problem - in fact, you’ve got various problems:

• You don’t furnish us with a detailed P&ID.  Consequently, we can’t tell how you intend to operate and control your venting process.
• You intend to “oxidize” (or incinerate) your VOCs, but you are inerting your VOC sources.  So, where is the required oxygen going to come from?  You need a stoichiometric rate of oxygen in order to carry out your proposed oxidation (and in a steady-state, I presume) so you must furnish the required O₂ or your RTO package must furnish it.  Either way, how do you intend to compensate for the inert N₂ that is combined with the VOC fuel?  Inerting mitigates the oxidation; oxygen causes oxidation.  One is fighting the other, and you don’t have a means of knowing how much nitrogen is mixed with your VOC fuel - so you don’t know how the inert nitrogen is going to affect your oxidation process in the RTO.  And you intend to operate the RTO at steady-state, around the clock?
• How do you intend to trigger the VOC feed to the RTO?  Will excess pressure at the source do it?

Normally, I would simply extract the VOC from the tank(s) with a blower and feed fumes to the oxidizer, with an excess amount of oxygen fed at the RTO burner.  Does this present problems or a hazard to you?  Not having a detailed process description (other than a simple block diagram) I can’t speculate further.

[Daniel C]

Thank you very much x 10E^6 Art Montemayor for your valid observations and discussion points you have pointed out.

 

Firstly, the P&ID was not presented at the time of posting as we were still finalizing conceptualizing the solution before coming up with a P&ID. I can safely say we have firmed on the idea of nitrogen inerting the process vessels. Safety has been our number one priority in deciding on this. We would the process upstream of the RTO to be immune to any risk of fire or explosion emanating from the RTO. We do not want to have a readily flammable gas stream in the vent header system all the time. The waste gas stream will be diluted with excess air within the battery limits of the RTO. The RTO is to operate round the clock. Fan(s) will drive the waste gas in the piping to the RTO.