Environmentally friendly gas

29-11-2018 | Posted by Joaquín Martí

Practically all the world, perhaps with the notable exception of President Trump, is concerned with CO₂ emissions from burning hydrocarbons and their effect on climate. After all, rational human beings are motivated by scientific truths, not by alternative truths and post-truths.

But it is rather hard to dispense with fossil fuels, let alone to do it quickly. In the meantime, a more environmentally friendly use would certainly be welcome. And natural gas (methane) can contribute to this goal.

Methane burns at fairly high temperature. This allows running a power plant and using its exhaust heat to drive a steam plant. This is what happens in a combined-cycle plant, in which we cheat the laws of thermodynamics to extract more energy than we could in a single-cycle plant. In round numbers, a modern combined-cycle plant gets 60% versus the 40% produced by a single-cycle plant. In other words, we generate 50% more energy per ton of discharged CO₂.

Natural gas can be transported by gaslines or, taking advantage of the 600-fold decrease in volume, in liquid form by means of cryogenic tankers since keeping methane liquefied at atmospheric pressure requires temperatures of about 165ºC below zero. Both export and import terminals must be provided with storage tanks for loading/unloading the tankers, and that is where Principia has been very active.

Starting in 1986, Principia has worked on over 70 projects of LNG tanks. They are spread over North and South America, Asia from the Middle East to India and the Far East, Africa and, of course, Europe.

We have contributed the complete design of the outer tank in around 30 tanks, ranging in size from 20,000 to 200,000 m³. And we have provided other services, particularly calculations for extreme loads, for the rest of the tanks.

Where would we be without simulation? Absolutely nowhere. During the design earthquakes, not only the structural responses of the inner and outer tanks need to be established, the liquefied gas is there with its impulsive and convective components.And minor and major leaks must be postulated, with large thermal gradients, cracking of the concrete and all sorts of non-linear behaviour.

And one must consider external fires, missile impacts, explosive pressures from a hydrocarbon cloud, etc. In several cases we even had to analyse impacts from various kinds of aircraft with different speeds and incidence angles.

There is practically no industry or technical field that has not been strongly affected by simulation. But in the case of storage tanks for liquefied natural gas, they would have simply been impossible without it, at least with anything near the level of safety that we demand from them.

And this makes it possible to operate combined-cycle plants with their lower carbon footprint, no matter what the alternative truths and post-truths say about it.