How safe is Liquefied Natural Gas?

By: Matt Wood


A liquefied natural gas demonstration involving, smouldering biscuits, a traumatised gold fish and a guy in a lab coat holding a lit cigarette. Matt Wood attended Evol LNG’s safety demonstration in Melbourne recently and found that the liquid gas is more stable than you think

How safe is Liquefied Natural Gas?
Liquefied Natural Gas is actually quite safe

When I was invited to attend a liquefied natural gas (LNG) demonstration called ‘Busting Myths’ I got all excited. I had visions of a couple of bespectacled idiots; one wearing a beret, blowing stuff up. I thought, "How cool is that!?"

Instead I was confronted with a steaming crucible of vaporising gas which was sitting on a lectern at a Melbourne venue, and there were no wacky one-liners from a couple of goofballs.

The purpose of the myth-busting demonstration however, was the antithesis of blowing stuff up; it was actually to demonstrate the stable and benign qualities of LNG. In short it’s actually very hard to blow up.

Achiever

Mention the words natural gas and most of us think of domestic heating, cooking and hot water. Given these uses it’s not surprising that natural gas has a reputation for being highly flammable and in the wrong circumstances, downright volatile. This is true to a point, except when talking about LNG which has been cryogenically frozen to -161C, shrinking its volume by 600 times, until it liquefies. In fact, it’s the liquefaction that helps give LNG its stability.

This is where the ‘Myth Buster’ himself steps in. Peter Micciche is the Superintendent of the Conoco Phillips Kenai LNG facility in Alaska. He is also an advanced LNG fire fighting specialist and holds certification in pipeline safety management and specialises in infrastructure management.

Micciche sits on the Coast Guard Maritime Security Committee; he’s also Mayor of the Alaskan city of Soldotna and operates a salmon fishing operation. Disappointingly, none of this involves blowing stuff up. My opinion is that Micciche’s business card should just read "Does a lot".

Micciche was in Australia at the invitation of Wesfarmers-backed company Evol LNG and was holding a series of demonstrations to highlight just how misunderstood and how safe LNG can be.

Sure, we media types have had a part to play in LNG’s image problem. After all, it’s pretty seductive to be able to label an overturned LNG tanker as a "potential fireball of devastating proportions".

It’s even harder to pass up the opportunity to measure the extent of potential devastation in Hiroshima terms.

The fact of the matter is that LNG, unlike other gasses, doesn’t blow up that easily.

The accelerant in the gas vapour is methane and it has a very narrow band of flammability when it’s in the atmosphere. Its flashpoint is much higher than diesel or other petroleum-based fuels. And when it comes into contact with the atmosphere it turns into vapour which dissipates very quickly.

LNG Safety Concerns

To illustrate the point, Micciche brought up a picture of a bulk prismatic LNG vessel called the Gaz Fountain. The vessel was in the Persian Gulf during the first Gulf War when it was struck by no less than three rockets. The resulting explosions damaged the ship, but didn’t detonate the cargo and the vessel was able to continue its voyage and discharge its cargo before being repaired. A new one on me was the revelation that the ocean-going LNG vessel actually runs on its own cargo, using the vapour given off by the stored LNG to fire the boilers.

Another pertinent image was that of a prime mover that had been involved in safety tests in the United States. The truck was set on fire with two full LNG tanks on board; for a period of 20 minutes at 540C. The intensity of the blaze reduced the vehicle to not much more than a puddle of molten metal. However, the double-skinned LNG tanks did not explode, not only that, the tanks were apparently removed re-skinned and put back into service on another vehicle.

You may well be wondering what the hell all this has to do with trucking and transport but both the viability and popularity of LNG as a transport fuel is growing globally, including in the US.

In fact the US recently announced its intention to become energy self-sufficient by 2022, hence the massive upswing in gas refuelling infrastructure across the country. LNG does have a lot of attractive qualities going for it; it’s cheap, it’s clean, Australia has bucket loads of the stuff and, according to Peter Micciche, it’s safe.

Systems query

To get an internal combustion engine to run on LNG there has to be another fuel with a lower flashpoint in the mixture as well, in answer to this there have been some interesting applications devised for heavy-duty LNG engines, both in the past and in recent times. LNG’s cousin compressed natural gas (CNG) can muddy the issue as the two are sometimes confused. It should be noted however, CNG takes up a lot more storage space as it’s in a compressed gas form a,nd because of that tends to be a little more volatile than the cooled liquid gas.

To date the most popular application has been to use a dual fuel system that runs on anywhere between 45 and 65 percent gas with the rest of the fuel mixture being made up of diesel. The advantage of a dual fuel system is that if the vehicle runs out of gas it will revert to running solely on diesel until it’s refuelled. Another advantage is that a dual fuel system can easily be removed at the end of a vehicle’s ‘first life’ and potentially bolted onto a new vehicle.

The outgoing vehicle can then be reassigned to lighter duties within the company or sold. Evol LNG has already launched their V5000HD dual fuel system for heavy-duty trucks.Evol _1

Another option is to use a high pressure direct injection (HPDI) set-up such as the Westport HD550 engine, by using the Westport the gas to diesel substitution rate climbs to 90-95 percent with diesel fuel only really used as a ‘liquid spark plug’ to ignite the gas vapour in the combustion chamber.

The downside of LNG is that if it warms up it turns to vapour. In a heavy vehicle, this means that a parked LNG-powered truck will lose most of the gas in its tanks if it’s parked for too long.

This doesn’t necessarily mean that the idea of heavy transport using LNG as a fuel is redundant. Plenty of large operators use shuttle trucks on round the clock changeovers, especially on the eastern seaboard.

These trucks don’t usually sit for longer than a couple of hours at a time and are covering the sort of mileage that maximises the economic benefits of using LNG.

Play time

Given that LNG can be cheap, clean and offers no performance loss, just how safe is it? Some care is needed when handling it as due to the fact that it’s so cold it can burn skin. However, Micciche’s demonstration included dipping carbon steel into his pot of LNG. This made the steel brittle and easy to break and, in a first for me, a man in a lab coat gave me a rose, albeit a smouldering, brittle LNG-covered rose which fell to bits when touched. I suppose I could read something into that.

Micciche went on to say that "one of the myths about LNG is that it’s the most dangerous of all the hydro carbons". He then set fire to it to demonstrate how slowly the flame propagates. He then poured it onto the floor. It sizzled and then died out. Again nothing blew up.

The whole point was to show that the fuel part of LNG is actually the methane vapour it gives off. When it hits the atmosphere it dissipates so quickly that it’s very unlikely to ignite. According to Micciche, the stoichiometric (air/gas) ratio required to cause a methane explosion could only really occur if the gas was trapped inside a building.

Things got a bit more exciting when Micciche dipped a lit cigarette into the LNG container – but it went out. Finally he dipped some biscuits into the liquid and gave them to audience members to munch on. This resulted in some interesting face pulling but no injuries. Personally I would’ve liked to see him do the Tim Tam trick, but that may have been too much.

Evol LNG recently opened an LNG refuelling station in the Victorian town of Wodonga and Evol Business Manager, Nick Rea confirmed that plans are afoot to roll out more refuelling infrastructure in New South Wales and Western Australia. The Evol’s east coast plan, short-term, is to open up the Hume Highway to LNG-powered vehicles. According to Rea, "we are targeting long distance heavy transport; these are the roles that stand to gain the most from using LNG and our dual fuel system".

Nothing may have blown up, but I still came away knowing more about LNG and its properties, as well as keeping all my fingers, toes and eyebrows.

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