Is LNG Fuel a good idea?

The next generation (some are being built now) of cruise ships will utilize Liquified Natural Gas (LNG) as their primary fuel. While there are some good reasons to use LNG (its clean and plentiful) we have a concern. LNG is potentially very explosive and cruise ships will carry hundreds of tons. Is this a good idea? Should thousands of passengers and crew be sitting on top of all this volatile gas? What do you think?

Hank

LNG, LPG and propane are all very similar. These products are in our lives every day- most of us have it piped to our homes, some even have tanks sitting in our yards. The construction standards for storage like this are pretty high, and storing in a liquified state makes it safer.

That being said, these gases are highly flammable. Yes, there is some risk, but, really, you could say the same thing about the gasoline in your car, and it's tank (and the tank trucks it is transported in) is far weaker than the tank propane is stored and transported in. Yes, I know there aren't any cruise ships powered by gasoline.

What I am saying is there is risk in virtually everything we do. LPG storage has risks, but they are smaller than other chemical risks in our society. I would take propane over gasoline in most situations. Diesel (on many ships for cleaner burning abilities) is somewhat safer than gasoline, but not risk free.

Sorry...30+ years of firefighter and hazardous materials...

The technology exists - many smaller applications of LNG fueled vehicles are common. Still, the idea of a cruise ship so powered conjures up images of the Hindenburg.

LNG, LPG and propane are all very similar. These products are in our lives every day- most of us have it piped to our homes, some even have tanks sitting in our yards. The construction standards for storage like this are pretty high, and storing in a liquified state makes it safer.

 

That being said, these gases are highly flammable. Yes, there is some risk, but, really, you could say the same thing about the gasoline in your car, and it's tank (and the tank trucks it is transported in) is far weaker than the tank propane is stored and transported in. Yes, I know there aren't any cruise ships powered by gasoline.

 

What I am saying is there is risk in virtually everything we do. LPG storage has risks, but they are smaller than other chemical risks in our society. I would take propane over gasoline in most situations. Diesel (on many ships for cleaner burning abilities) is somewhat safer than gasoline, but not risk free.

 

Sorry...30+ years of firefighter and hazardous materials...

Plus 1.

Basically, it would take a "bomb" to turn LNG storage on a ship into a "bomb." USCG training requirements for LNG certified officers on ships entering the US adds to the safety quotient.

That said, if one wants to discuss the future of cruise ship propulsion, keep an eye on current R&D of "miniaturized" rotary kiln technology running on waste. It has already caught the eye of the US Army.

LNG carrying ships, that carry tens of thousands of tons of LNG at a time have been around for 40 years, and there has never been a single fire or explosion on them. Liquid LNG is not explosive. LNG vapor is only explosive when in a confined space, and only when in a narrow band of 5-15% when mixed with air. Too high a concentration of LNG vapor, and it will not explode, nor even be flammable.

I would have to check the most recent class requirements for LNG powered passenger vessels, but due to the limited amount of storage tank space onboard, they will be using reliquifaction equipment to take the "boil off gas" (that LNG that evaporates as it warms up) and turns it back into cold liquid. I think that class also requires nitrogen to "inert" the tanks (replacing the air above the LNG liquid level in the tank with pure nitrogen), and when a flammable substance is in an inert atmosphere, it cannot burn or explode.

The area where the LNG fuel is most susceptible to fire is at the diesel engine, where it has been gasified, and under pressure, and a leak could contact a hot surface on the engine and catch fire. But, then again, even residual fuel oil, the current fuel of choice, if at room temperature and atmospheric pressure, could be heated with a blow-torch and not catch fire, will be highly flammable when sent to the diesel, as it is now heated to 240*C, and under 100 psi of pressure, so a leak onto a hot surface will also cause a fire (Carnival Triumph and Splendor).

I think LNG is a safe fuel to use, I just think there will be significant bottlenecks in the supply infrastructure for the foreseeable future, and that the cruise lines are jumping onto the bandwagon a little too hard, and may find themselves with ships stuck in port waiting on LNG supply.

I was hoping ChengKP would jump-in here with his expertise :). In my younger days, when playing volunteer firefighter, I had a nasty experience dealing with a blown pressurized tank (very large tank) of LNG. We now see more and more city buses running on LNG (they usually store the LNG in tanks on the top of the bus). I guess the good news is that you can never have an "oil spill" with LNG :).

Hank

I was hoping ChengKP would jump-in here with his expertise :). In my younger days, when playing volunteer firefighter, I had a nasty experience dealing with a blown pressurized tank (very large tank) of LNG. We now see more and more city buses running on LNG (they usually store the LNG in tanks on the top of the bus). I guess the good news is that you can never have an "oil spill" with LNG :).

 

Hank

Big, big difference between a pressurized tank of LNG (or probably LPG), or a bus' fuel tank, and an LNG tank on a ship. The tanks on ships are insulated (surrounded by vacuum, so essentially a thermos bottle) so that the LNG is kept as close to -260*F as possible (LNG's condensing temperature at atmospheric pressure). The tanks are also not maintained under great pressure like the tanks on your grill are, they are only at about 3 psi. Pressurized tanks, like grill tanks or bus fuel tanks, use high pressure to maintain the LNG as a liquid instead of temperature (higher the pressure, the higher the boiling/condensing temperature). When the pressure rises above this, the liquifaction equipment will draw off the vapor, cool it back down and reinsert it into the tank as cold liquid. The tanks also have relief valves, so that if the pressure rises too fast for the liquifaction equipment to handle, the excess vapor pressure is vented. The boil off vapor is also taken to be used by the ship's engines, so venting is an extremely rare case. And I did check, and the tanks need to be inerted to carry LNG.

And even a large pressurized tank of an inert gas like nitrogen, when heated will explode due to rising pressure.

LNG carrying ships, that carry tens of thousands of tons of LNG at a time have been around for 40 years, and there has never been a single fire or explosion on them. Liquid LNG is not explosive. LNG vapor is only explosive when in a confined space, and only when in a narrow band of 5-15% when mixed with air. Too high a concentration of LNG vapor, and it will not explode, nor even be flammable.

 

I would have to check the most recent class requirements for LNG powered passenger vessels, but due to the limited amount of storage tank space onboard, they will be using reliquifaction equipment to take the "boil off gas" (that LNG that evaporates as it warms up) and turns it back into cold liquid. I think that class also requires nitrogen to "inert" the tanks (replacing the air above the LNG liquid level in the tank with pure nitrogen), and when a flammable substance is in an inert atmosphere, it cannot burn or explode.

 

The area where the LNG fuel is most susceptible to fire is at the diesel engine, where it has been gasified, and under pressure, and a leak could contact a hot surface on the engine and catch fire. But, then again, even residual fuel oil, the current fuel of choice, if at room temperature and atmospheric pressure, could be heated with a blow-torch and not catch fire, will be highly flammable when sent to the diesel, as it is now heated to 240*C, and under 100 psi of pressure, so a leak onto a hot surface will also cause a fire (Carnival Triumph and Splendor).

 

I think LNG is a safe fuel to use, I just think there will be significant bottlenecks in the supply infrastructure for the foreseeable future, and that the cruise lines are jumping onto the bandwagon a little too hard, and may find themselves with ships stuck in port waiting on LNG supply.

Thanks again for sharing your knowledge and expertise

Big, big difference between a pressurized tank of LNG (or probably LPG), or a bus' fuel tank, and an LNG tank on a ship. The tanks on ships are insulated (surrounded by vacuum, so essentially a thermos bottle) so that the LNG is kept as close to -260*F as possible (LNG's condensing temperature at atmospheric pressure). The tanks are also not maintained under great pressure like the tanks on your grill are, they are only at about 3 psi. Pressurized tanks, like grill tanks or bus fuel tanks, use high pressure to maintain the LNG as a liquid instead of temperature (higher the pressure, the higher the boiling/condensing temperature). When the pressure rises above this, the liquifaction equipment will draw off the vapor, cool it back down and reinsert it into the tank as cold liquid. The tanks also have relief valves, so that if the pressure rises too fast for the liquifaction equipment to handle, the excess vapor pressure is vented. The boil off vapor is also taken to be used by the ship's engines, so venting is an extremely rare case. And I did check, and the tanks need to be inerted to carry LNG.

 

And even a large pressurized tank of an inert gas like nitrogen, when heated will explode due to rising pressure.

What you are talking about here is a BLEVE- Boiling Liquid Expanding Vapor Explosion. The additional benefit I mention in my post of storing LNG is a liquid state is that the tank can take a lot of heat in the liquid space, and not fail. I didn't know the tank in a ship would have such insulation, which is almost a cryogenic state(cryogenic is stored below vapor temp, and below -300F)..further enhancing it's safety. More votes for the possibility of powering ships in a fairly safe manner.

And yes, ANY tank under pressure can fail, whether the contents are flammable or not.

While LNG or dual fuel engines are just being introduced to cruise ships, the concept has been around for many years. Small river ferries outside Vancouver were converted back in the late 80's/early 90's. As Chengkp75 mentioned LNG carriers have safely carried thousands of tons of LNG since the 1970's.

Is LNG explosive - when stored in the liquid form absolutely no; however, the gas, like all hydrocarbons is explosive at certain concentrations, which vary by product. When dealing with gases, the explosive range is bounded by the Lower Explosive Limit (LEL) & Upper Explosive Limit (UEL). LNG has a relatively extensive explosive range as the LEL is 5% & UEL is 15%, the gasoline equivalents (from memory) are about 1% & 7%. On tankers we continuously monitored the concentration to ensure it remained outside the explosive range.

My last ship (Cruise/Ferry) has recently gone through a major conversion to LNG. It is considered as dual fuel, with LNG as the primary and diesel as a secondary, to aid combustion. The fuel tank is highly insulated (as described by Chengkp75) and is considered as a Deep Tank, as it is located in a Void Space. Basically, none of the tank is part of the ship's hull.

I believe the LNG expansion ratio for liquid to gas is 600:1, so they also installed a large diameter vent (18" - 24" dia), which heads up to the open decks, well above the funnel & main mast. In addition to boil-off from the bunker tank they also have venting capability from the fuel supply lines, which are also insulated. If the engine speed is significantly reduced the liquid fuel in the line would boil-off, so must be vented.

The safety systems included are extensive, both in the engine control room and Bridge. So, am I comfortable sailing on a duel fuel ship - yes. Personally, LNG has more risk factors than diesel or HO, but the risks are well mitigated, as are the risks of using other fuels.

Plus 1.

Basically, it would take a "bomb" to turn LNG storage on a ship into a "bomb." USCG training requirements for LNG certified officers on ships entering the US adds to the safety quotient.

That said, if one wants to discuss the future of cruise ship propulsion, keep an eye on current R&D of "miniaturized" rotary kiln technology running on waste. It has already caught the eye of the US Army.

In case there's any engineers out there who may be interested:

http://www.awmanenychapter.wildapricot.org/resources/Documents/Presentations/150422-AWMA-GasificationOfMSW.pdf

The jury is still out on feasibility -all things considered. But syngas production using custom designed rotary kilns are not unworkable and could eventually be ideal for ships (literally, running in their own waste).

In case there's any engineers out there who may be interested:

http://www.awmanenychapter.wildapricot.org/resources/Documents/Presentations/150422-AWMA-GasificationOfMSW.pdf

 

The jury is still out on feasibility -all things considered. But syngas production using custom designed rotary kilns are not unworkable and could eventually be ideal for ships (literally, running in their own waste).

Interesting thought, though I don't know how they expanded from a stationary test facility to envisioning use on cruise ships. Just did a quick review of the article, and here's my take:

How does the rotary kiln react to motion, i.e. rolling and pitching of the burning waste bed?

High heating value of generated gas is about 1/7th that of natural gas, so not real efficient energy source.

Two tons of waste a day to power a 60 kw generator, still using 50% diesel. Now, taking a cruise ship's waste stream (solid waste like paper/cardboard, food waste dried from the pulper system, and waste dried from the waste water plant, notice they only allow a 28% moisture rate) (I notice they limit plastics to about 12%), my estimate is (admittedly off the top of my head, never thought about it before) around 8 lbs/person/day (based on adaption of some land based data from US), that comes, on the Oasis, to be about 35 tons/day, or enough to generate about 1/2 a megawatt. The ship can generate 97 megawatts, so this is an infinitesimal amount of power.

The installation still requires an exhaust gas scrubber, so no savings there, as LNG does not require a scrubber.

I was thinking that this system would not react well to rapid load changes, much like coal fired steam ships, where the system cannot anticipate changes in vessel speeds while maneuvering and you over or under feed the coal (long burn time, like the kiln here), but then I realized that this is producing 0.5% of the power, so it wouldn't matter to load fluctuations.

Not sure if the "fuel savings" of this relatively small amount of energy would offset the cost and the "real estate" inside the ship that would be required.

Thinking long term - way out there, to the point where the Earth’s fossil fuel supply is exhausted; there is a fair likelihood that hydrogen will be the portable fuel of the future. The only by-product of combustion is water, it can be produced from water with electricity - which may ultimately be wind, tide or solar-produced.

The transmission storage and combustion systems are likely to evolve from LNG systems: making LNG a step to the distant future as well as a nearer term solution.

Today's Florida Today:

The world's largest cruise line will be basing its largest ship at Port Canaveral, starting in 2020.

Canaveral Cruise Line's plan to base its still-to-be-built ship at Port Canaveral will help boost tourism on the Space Coast and solidify the area as a leader in the cruise industry.

The ship will have a capacity of 5,286 passengers, based on double-occupancy of its cabins, and a maximum capacity of 6,500. It is likely to have an onboard crew of about 2,000.

It will be the first North American-based cruise ship to be powered by liquefied natural gas.

Cruise Terminal 3 will be Port Canaveral's largest construction project ever, with an estimated cost of $150 million, including the terminal, parking garage, berth improvements and roadways.

The terminal is scheduled to open in mid-2020.

Construction of the 180,000-ton cruise ship is scheduled to begin in November, with the official steel-cutting ceremony at the Meyer-Werft shipyard in Turku, Finland.

Interesting thought, though I don't know how they expanded from a stationary test facility to envisioning use on cruise ships. Just did a quick review of the article, and here's my take:

 

 

 

How does the rotary kiln react to motion, i.e. rolling and pitching of the burning waste bed?

 

 

 

High heating value of generated gas is about 1/7th that of natural gas, so not real efficient energy source.

 

 

 

Two tons of waste a day to power a 60 kw generator, still using 50% diesel. Now, taking a cruise ship's waste stream (solid waste like paper/cardboard, food waste dried from the pulper system, and waste dried from the waste water plant, notice they only allow a 28% moisture rate) (I notice they limit plastics to about 12%), my estimate is (admittedly off the top of my head, never thought about it before) around 8 lbs/person/day (based on adaption of some land based data from US), that comes, on the Oasis, to be about 35 tons/day, or enough to generate about 1/2 a megawatt. The ship can generate 97 megawatts, so this is an infinitesimal amount of power.

 

 

 

The installation still requires an exhaust gas scrubber, so no savings there, as LNG does not require a scrubber.

 

 

 

I was thinking that this system would not react well to rapid load changes, much like coal fired steam ships, where the system cannot anticipate changes in vessel speeds while maneuvering and you over or under feed the coal (long burn time, like the kiln here), but then I realized that this is producing 0.5% of the power, so it wouldn't matter to load fluctuations.

 

 

 

Not sure if the "fuel savings" of this relatively small amount of energy would offset the cost and the "real estate" inside the ship that would be required.

US Army funded the study at SUNY Cobleskill - looking at a potential solution for waste removal that could be made "portable" for field operations. Like LNG et al., rotary kilns to handle waste/make syngas have been in use for years. But application/modification/etc is the challenging frontier.

Today's Florida Today:

 

The world's largest cruise line will be basing its largest ship at Port Canaveral, starting in 2020.

Canaveral Cruise Line's plan to base its still-to-be-built ship at Port Canaveral will help boost tourism on the Space Coast and solidify the area as a leader in the cruise industry.

The ship will have a capacity of 5,286 passengers, based on double-occupancy of its cabins, and a maximum capacity of 6,500. It is likely to have an onboard crew of about 2,000.

It will be the first North American-based cruise ship to be powered by liquefied natural gas.

 

 

Cruise Terminal 3 will be Port Canaveral's largest construction project ever, with an estimated cost of $150 million, including the terminal, parking garage, berth improvements and roadways.

The terminal is scheduled to open in mid-2020.

Construction of the 180,000-ton cruise ship is scheduled to begin in November, with the official steel-cutting ceremony at the Meyer-Werft shipyard in Turku, Finland.

Any information on how they plan to bunker?

My last command, which now runs on LPG, has experienced a few issues with bunkering. All fuel comes aboard at night from road tankers. Full "B-trains" of diesel (35,000 litres) gravity dropped in about 40 mins, so we could easily take 2 trucks and still leave the GY engineers time for maintenance. Each of the LPG tankers are taking almost 3 times the discharge time, which is severely cutting into the engineers maintenance.

Do you know if they will bunker from shore tanks or bring bunker tenders alongside. I also wonder what the transfer rate is for LPG compared to HO/diesel.

I've been wondering the same thing

LNG is not handled at the port today .... that is, PC is not a transfer port for this commodity.

However Waste Management trucks for the county are mostly LNG fueled so there must be a storage facility somewhere in the area.

I suspect something like this will happen

http://gcaptain.com/conrad-delivers-first-lng-bunker-barge-built-in-north-america/

The barge is designed and engineered by Bristol Harbor Group. It is 232 feet in length and features a single 2,200m3 liquified natural gas (LNG) tank equipped with MARK III Flex cargo containment technology, from the French engineering and technology company GTT (Gaztransport & Technigaz).

Thanks, impressive looking barge.

The last I heard, Carnival had contracted with Shell to provide the bunkering, and Shell was building the bunker barge. My guess is that for the moment, since there isn't an export facility in FLL, that the barge will use the Crowley facility in Jacksonville. Not sure how much excess capacity the facility will have after Crowley's container ships get their bunkers there. Tote is using road trucks with a custom built pumping skid, both in Miami and Seattle for their LNG ships. Yes, we could bunker diesel or residual fuel at 200-300 mt/hour, doing road trucks of LNG would be very time consuming, not to mention the down time between trucks if there is traffic, loading delays, etc, etc.

I don't believe the ferries use cryogenic tanks, but pressure tanks on deck, am I right? That can speed up the loading process if your pumping skid works well. When loading to cryogenic tanks, you first have to spray liquid into the tank to start the cool down process, otherwise the tank will shatter. They have to cool the tanks to about -220*F (-140*C) before loading can commence. Not sure after that what the transfer rate would be.

And that barge, which holds 2200m3 of LNG is designed for a container ship that holds 1800m3 of LNG, to power a measly 22Mw main engine. Assuming that the new Carnival ships will be in the 60-80Mw range, and with a longer itinerary than the Tote vessels, they will need a barge 3-4 times as large, or barges at various ports around the Caribbean to refuel, as they are planning on doing with the new Aida ships in Europe.

certainly suggests they won't be using trucks ......

the lack of infrastructure is one of the things that has made me wonder about widespread LNG use ....

Same deal as hydrogen fuel cells in cars which work well but there's no wide infrastructure for refueling. No one builds cars cuz there's no fueling system and no one expands the fueling system cuz there's no cars/demand. Electric is a somewhat different issue for cars cuz altho there may not have been 'charging station' there WAS electricity ... just the plug was missing ....

I'll be watching for further news on this .... the port is just down the road.

.

 

Not sure if the "fuel savings" of this relatively small amount of energy would offset the cost and the "real estate" inside the ship that would be required.

From what you say, it sounds like they would do better with sails....;p

Yeah, I've always thought this would be a chicken and egg situation. And Carnival blinked and made their commitment to Shell, with a good sweetener in it, I'm sure. Logistics for this is difficult in Europe, and they have a lot of LNG export facilities over there, way more than we do. I think that after about the first cruise to keep the hype up, they will start going to blended operation, only using a percentage of LNG until the infrastructure ramps up to meet demand.

hmmm

are you saying the ships are tanked for both LNG and "regular" fuels ..... and run on one or the other or a mix .....

this is an aspect I'd not considered or seen in the discussions of LNG fueled ships .......

do my local WM trucks touting LNG fuel, actually run on diesel???? with just an LNG kicker?

hmmm

 

are you saying the ships are tanked for both LNG and "regular" fuels ..... and run on one or the other or a mix .....

 

this is an aspect I'd not considered or seen in the discussions of LNG fueled ships .......

 

do my local WM trucks touting LNG fuel, actually run on diesel???? with just an LNG kicker?

Trucks and buses typically run on straight LNG, but this requires a spark plug for ignition.

Almost all marine diesels that are LNG capable are "dual fuel" and can run on LNG, diesel, or residual fuel (and some can even run on crude oil), and the mixture between liquid fuel and gaseous fuel is infinitely variable between 0% gas to about 98% gas without requiring a spark ignition. This is one reason I think the ships will get away with limited bunkering facilities, is that once outside the US ECA, they will switch from LNG to diesel or residual fuel that still meets the emissions requirements outside an ECA. It takes about 3 times the volume of LNG to produce the same energy as diesel or residual fuel, so I've never been convinced of where they intend to store all this LNG if they intend on running on straight LNG.

The auto-ignition temperature of diesel or residual fuel is around 250*C (temperature at which it will burn without a flame or spark present), while natural gas is around 530*C. So, a little diesel in the fuel mixture when sprayed into the hot air in the diesel's cylinders, will provide the "spark" to start the natural gas burning.