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The Paris Agreement on greenhouse gas management and reduction is now 1-year old, and it looks like it is causing a potential growth industry … waste gas management.

And … to meet the targets of the Paris Agreement, it looks like flaring will not be good enough. More processing will probably be needed.

The concepts of waste gas management will probably be the same as waste management, and follow the same hierarchy (prevention, minimisation, reuse, recycling, energy recovery, and disposal). But should they?

Prevention is an obvious desired outcome, but … outside of managing fugitive emissions (which is itself a big task) the only path to prevention that easily presents itself is a pre-treatment of some kind. And pre-treatment is often chemical process intensive – not a good option for simple industries.

Minimisation is a lesser form of prevention that focuses on efficiency instead of completion. Again, I think the path to minimisation is very similar to the path to prevention.

And that brings us to reuse, recycling, and energy recovery. All three of these require one thing … collection. And gas collection is never easy for two reasons:

  • The thing that helps us in solid and liquid waste collection – gravity – does not really help us in gas waste collection
  • The piping for gas waste collection is probably expensive (very low pressure driving forces, very low gas densities, very large pipe diameters).

The most common gas waste collection system is a flare, and the idea of doing more with a flare system is inherently expensive with (using previous thinking) minimal benefit. This combination of high cost and low benefit has often resulted in gas waste being processed minimally before being released to the environment (translation – we burn it).

Now, burning of hydrocarbon gases does reduce our greenhouse gas footprint compared to not burning them, but if we are going to meet the targets of the Paris Agreement, the reduction is probably not enough.

The issue of collection got me thinking … and I am starting to think that a combination of venturi type ejectors and the current fuel gas system could help reduce waste gas.

Now, some of you are probably thinking that venturi type ejectors are not very efficient. And you are correct. But … consider this:

  • Fuel gas is usually delivered at pressure (gas mains pressure) before being reduced to burner pressure or engine pressure (almost atmospheric pressure). <NOTE: this is not applicable to combustion gas turbines>
  • We have to reduce the pressure of the gas anyway, so efficiency tends to become a non-issue when we do not care – the current efficiency of the pressure drop in a simple Joule-Thomson type valve is 0% (zero benefit extracted).

This pressure drop could be used as the motive force to collect waste gases around the plant, for blending into the fuel system. The resulting mixture would be combusted (which is possibly currently done in a flare system ) but with the benefit of energy recovery that is not easily available from a flare system. If the waste gas has some other value, this would concentrate the “value” into one stream in a relatively centralised location, making value adding processing easier. A fuel gas conditioning system could be expanded to be both fuel gas conditioning and waste recovery.

So … while we are still burning the waste gas, we are getting some benefit from it, as opposed to the no benefit of flaring. And getting the benefit is the extra nudge we will probably need to help meet the Paris Agreement.

One big pushback on waste gas processing is the technology required. Consider pre-treatment of coal for CO2 minimisation – it turns a simple coal fired power station into a complex chemical plant. Waste gas management will need to be simple, but provide a positive impact per the Paris Agreement.

Another big pushback is simply a lack of perceived benefit. Waste gas processing will require incremental investment (people understand the cost of investing in a flare system, with negligible benefit for their investment) with what benefit? The Paris Agreement is a target, and government (or someone) needs to provide a mechanism to make it happen, be it economic or legislative.

Any further discussion / analysis of waste gas processing will probably require more information about the specifics of the waste gas, but … the idea of using fuel gas and venturi type ejectors are simple and do not make major changes to existing facilities. And … by centralising as an end of pipe concept, it makes outsourcing treatment easier.

I think the Paris Agreement will see an increased use of venturi like ejectors.