Liquified Methane

[voltech444]

I am doing some research that requires small amounts of liquified methane (<50L) I need a tank I can transport by truck to my closet LNG fueling station to refill. The only tanks that are available for LNG are for class 8 commercial trucks as fuel tanks to run the truck on LNG. So they are much more expensive and currently only available in the whole kit to convert each truck. I only need the tank and fittings, I've reached out to the company (blu fuels) and I'm awaiting response to know if I can buy pieces of the kit individually. If I cannot I am looking at some cheaper possible alternatives.

One idea I've thought of is to convert a N2 cryogenic tank to LNG. I found one other thread on another forum on this topic but unfortunately it didn't have much information. They said it should work. I would still need to the correct fittings to refuel but those are available.

What other modifications would be required to convert a N2 tank to LNG? Is it technically feasible? Practical?

I appreciate any input on this topic. This is not my area of expertise yet, I am learning more about these LNG systems there is just not as much information readily available like for CNG systems. In order to carry out this experiment I need LNG but my budget is restricted to less than $10k so I'm trying to find a solution.

Thank you for looking!

 

[voltech444]

BTW here is the truck fuel tank:

The Blu V2 LNG Fuel Delivery System, a 160-diesel-gallon equivalent twin-tank package, has a list price of $18,000 after a $7,000 rebate for fueling at Blu’s network of 24 LNG stations across the country.

Website:

http://www.blulng.com/lng-solutions

 

[LittleInch]

I can't see why a liquid N2 tank wouldn't work. The difference is how do you deal worth the boil off gas as you transport it??. All such systems work at very low pressure but need to vent if you're not using gas.

Otherwise I can't see any serious issues, but the venting is your key problem. You could very easily create am explosive atmosphere if your not careful whereas as N2 whilst an asphhxiant won't blow up.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[saplanti]

As I understand the automotive applications, not exactly but almost the same as the LPG bottles. Methane liquefies under pressure, and I guess, this is the one you are after. I do not think you want liquefied methane at atmospheric pressure.

 

[EmmanuelTop]

You should verify the requirements against NFPA 59A, "Production, Storage, and Handling of Liquefied Natural Gas (LNG)". The most recent version can be accessed by signing in at NFPA 59A

The 2006 version is available on the internet: NFPA 59A (2006)

The major difference between N2 and LNG is that the latter is flammable which imposes additional safety features.


Dejan IVANOVIC
Process Engineer, MSChE

 

[voltech444]

Thank you all for your input it is greatly appreciated!

I am reading about the cryogenic tanks I am considering using, I will post the specs for them and the valves tomorrow. I will share the information I get from Blu Fuels; I've also reached out to some other people inside the LNG industry and i am awaiting response.

 

[voltech444]

Hey all just thought I would explain a little more what my research is. It's pretty simple really; im doing bench testing with a prototype engine. I've written about this engine on physics forums a few years ago. It's called a reverse uniflow 2 stroke diesel engine. It utilizes a turbocharger and supercharger for maximum power density and efficiency. I am using LNG because because of it's cryogenic properties, it will cool compressed air coming from the turbo compressor which allows higher levels of boost with less heat. This engine also utilizes water injection to further cool compressed air without the need for an intercooler. It is possible to do some of the testing without LNG and just using gaseous methane; however for the best results I need LNG.

 

[EmmanuelTop]

Then you might also be interested in NFPA 57a or 2002 PDF version at NFPA 57A 2002


Dejan IVANOVIC
Process Engineer, MSChE

 

[voltech444]

Here are 2 tanks I am considering purchasing; they are both LN2 dewars but they already have the plumbing needed to convert to LNG.

1.) Liquid Nitrogen Dewar, 25 liter, Taylor-Wharton brand, Model 25 LD. Nice used condition. No damage. Comes with plywood dog house shown, and roll around stand. Shipping depends on whether or not buyer wants the plywood box. So for now, it's shown as Local Pickup. Will Ship. Thanks for looking.

2.) This CFI Cryofab Liquid Nitrogen UN 1977 Dewar Non-Magnetic 11/99 appears to be in fair cosmetic condition with signs of wear and previous use.

I really lack the knowledge and equipment to test this piece properly and so it is being sold as-is.

Unpacked dims are 20*20*41.

I attached 2 pdf files with the specs for the fill and vent valve. I've also included pictures of the tanks and valves. Here is the website:

Link

The more I research this the more I realize it is definitely possible. The main requirement is to get a LN2 tank that already has fittings, valves, and gauges on it. They are a little harder to find but they are definitely out there. I will hopefully be purchasing a tank this week. I can then know if I need my fill/vent valves to be in english or metric; both are available from Macro Tech.

Thank you all again for your help, it took me longer to get these specs up here so I apologize for the delay. I will definitely give updates of my progress and take lots of pics to show what I am doing. I'm sure I'll have some other questions.

 

[voltech444]

CFI Cryofab Liquid Nitrogen UN 1977 Dewar Non-Magnetic 11/99:

LIQUID NITROGEN DEWAR TAYLOR-WHARTON 25 LD:

Valves:

 

[voltech444]

I attached a pdf for the fill valve on my last post; and for the vent valve on this one. I'm guessing there's probably a better way to get this on here but here it is.

 

[LittleInch]

voltech,

I'm not qualified to say whether these second hand units are good enough for your use, but the key to me is doing something that means you aren't leaking explosive gas into a confined space. A little bit of N2, whilst it can be lethal in certain places if it pushes all the O2 out, won't explode - methane can.

Hence the design pressure of those containers is critical as any rise above the design pressure requires venting. If this pressure is quite low, then it won't take much of a rise in temperature to start venting when you're transporting or storing it as opposed to using the LNG.

Clearly all the connections and piping need to be suitable for cryogenic temperatures and insulated for personnel protection and to avoid lots of ice on small bore piping.

Be careful.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[voltech444]

I've been researching pipes/valves that are suitable for cryogenic liquids. From what I can tell, the pipes/fittings/valves/gauges on that cryofab tank are designed to work with LN2, so they should also work with LNG. My plan is to testablish the tank by filling it with LN2 and checking for leaks, and monitoring the boil off gas rate to make sure it's in spec. I will also do tests in the truck to see how the motion affects the boil off rate. If everything is in spec and no leaks are detected, I can drain the LN2, leaving only N2 gas inside which will be safe for filling with LNG.

One possibility for the vent gas is to run the vent tube to the engines intake manifold. Since I'm only transporting a small amount of LNG it shouldn't be producing a lot of gas, so it shouldn't choke off the engine. I wish I had a diesel-powered truck because the methane would actually increase the MPG. I'm trying to do some calculations to know roughly how much gas will be vented and if it will affect engine performance.

 

[voltech444]

One other thing, the tank will be transported in an open pick up truck bed and stored outside not in a confined space.

 

[LittleInch]

That sounds like a good plan. You won't have much boil off if the tank is any good, but outside and a free vent is the best idea. Just make an outside shed for it at your lab / garage.

Did you find out what the max pressure in the tank was?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[voltech444]

I'm still trying to find the specs for the tank, I'll post it when I find them. I'm assuming the inner tank lining is stainless steel, once I get the specs I should know; anyone have any insight on this? I've looked at a chart that shows the psi required to hold LNG at a given temperature. If I remember correctly it can be as low as 4 psi up to 200-300 psi; lower the pressure, lower the temperature. From my understanding this basically means that at a lower pressure the boil off gas rate increases. I plan on working at a lower pressure because of safety. I'm studying what the lowest pressure with lowest boil off ratio is.

 

[stookeyfpe]

Before you go deeper into this you should stop and review NFPA 52, Vehicular Natural Gas Fuel Systems Code. Your selected fueling connections don't comply with the standard and your selected containers have issues.

Good luck

 

[voltech444]

Thank you for that, i'm reviewing the NFPA 52, lot's of information to digest. The main issues with the tanks is they were not originally built for this purpose. If I can't make the tank and connections up to code, or at least close to it, I won't go forward with this project until I know my system is good. I talked to a customer service rep from my closest LNG fueling station, Clean Energy, the station is open to the public 24/7, all that is needed is a CC. I was a little surprised, there is nobody to check and make sure your system is up to code, or any applications or inspections that are needed. My tank will be transported in a personal vehicle not a commercial one, does it still have to comply to the same standards because it is being transported across the highway? I'm trying to get some more answers on these questions. Unfortunately I haven't received any responses from a few of the companies I reached out to that specialize in LNG fuel systems. I'll keep updates here, i'm hopefully ordering the cryofab tank this week because they accepted my offer.

 

[voltech444]

I wanted to post this link to a thread talking about this same issue:
Link

I wanted to note in regards to that thread that LNG does not contain mercaptans. This is why a methane detection monitor is required for vehicles using LNG.

 

[saplanti]

I guess you need to determine the available LNG temperature and pressure from the refueling station first. Is the LNG in the cryogenic temperature with atmospheric pressure or at saturation temperature (for discussion say close to zero degree Celcius) and corresponding pressure. Then go for the required equipment probably in accordance with NFPA 52 as given above.

If you are refueling the bottle under pressure you cannot use an equipment with cryogenic temperature and atmospheric pressure. You need to sort out the process that you are going to follow. Without the process diagram you will hit the wall. Your process diagram should provide adequate equipment that the filling station will accept. Second; how and at what condition you are going to introduce the fuel into the engine? Liquid phase or gas phase? I would assume it is the gas phase at certain conditions. In case you have liquid cryogenic fluid how are you going to produce the gas, and at what condition? What kind of equipment do you need for the conversion to gas? How fast do you need to produce the gas, what the flow rate would be at what condition?

There are many question to answer. If you cannot answer some of those yourself no one would be able to answer your questions adequately. We can give our guesswork only. In the links that you provided Montemayor explains the terminology and the constraints that you need to consider as well.

If you are not able to get the answers yourself, I suggest you consider a consultant to do the job for you.