Frank, you don't get to monopolize discussions, how fascist and arrogant.
I think that's a bit harsh as it looks to me that the topic starter also has to be topic moderator on these forums. I'm sorry that you feel that way but, having started a topic, I would like to keep it on track. Even though you have some valid points, your contribution seemed to me to be completely off topic because thought I was clear that this discussion was about fueling with CNG and LNG. If you were to start your own discussion about using ethanol/methanol from natural gas, I would only add a reply if I had something useful to contribute.
Yeah Frank, I see your discussion is going real well, just like a lot of other so called discussions on here. Did you know ethanol can be synthesized using natural gas and it can be put into 10 million vehicles now without modification? Did you know that synthetic gasoline can be made from methanol that can be made from natural gas? Probably not because you want to keep the discussion confined to the same old topic that has been rehashed for more than two years on here.
As I mentioned earlier, I think you have some valid points. My understanding was that the "Products and Ideas" section was to let everyone know about a product or an idea and often this doesn't involve a lot of discussion. I wasn't expecting to get a lot of replies because I think the 2 articles referenced above are reasonably well researched. I was hoping that, if anyone was thinking about trying CNG or LNG, the information provided would be a useful starting point.
I don't understand why you are so reluctant to start your own discussion but here we are. So ... now that we are talking about ethanol/methanol in this discussion, do you have a plan for the marketplace acceptance of ethanol/methanol from natural gas?
Hi Frank: I think you are doing a good job of communicating. Well referenced and perhaps even reality. I doubt that natural gas can be converted to ethanol or methanol at a competitive price, so no profit, unless government gets envolved, which I agree rarely works well. Methanol has some problems when used in most existing vehicles. SJC starts his own discussion even less often than I and most others here, so keep up the good work.
It appears to me that the USA agency in charge of approving CNG conversions is being obstructive, but we can hardly expect government to do anything well, so we are reasonable to assume the government is guilty unless they can prove their inocense. Apparently they are too arrogent to even attempt to show they are promoting CNG.
Have you any detals on using LNG to power vehicles? Neil
I'm wondering what the truck does with the boil off from the LNG, if the next departure is delayed?
I don't think it is prudent to inject LNG into the hot cylinder, so how do we insure sufficient boil off to climb a long steep hill. Obvously there can be a CNG tank to store boil off, but that makes the system more complicated and thus more costly to repair. Possibly the truck driver could sometimes sell CNG to private CNG car owners? Refilling the CNG to 1000 psi might insure the car will make it to a regular CNG filling station which might be 20 or more miles away.
It appears the LGN filling station also has significant CNG that they can sell from their boil off. Neil
LNG isn't used directly in the engine because the fuel system supplies natural gas vapor to the engine. In the case of the Westport HD GX engine, the liquid fuel is first pumped to 4500 psi and then vaporized to 100°F. Single-Line fill systems typically use an "economizer" to remove vapor from the tank but it is not clear from Westport's product information if their LNG pump can handle a mix of liquid and vapor. I suspect that Cummins-Wesport's ISL-G engine uses an economizer to remove fuel tank vapor. However, boil-off from the fuel tank is a very real LNG Issue . The best solution is to keep the heat leaking into the tank at a minimum, which will minimize any vapor blow-off. Some tanks (like those made by Cryogenic Fuels) can be on standby for about 12 days before this becomes an issue. It is important to keep the tank temperature as cold as possible (ie, near -245°F) and not artificially add heat to raise the pressure in the tank. Using a Two-Line fill system, it is possible to subcool the tank contents to -245°F during refueling and then pressurize the tank to the pressure required by the fuel delivery system.
Any fleet with LNG vehicles should be aware of the cryogenic nature of the fuel and have procedures in place to ensure that the vehicles are in continuous use, thereby ensuring that the fuel never has a chance to overheat. For fleets with vehicles that have the potential to be parked for indefinite periods, it makes more sense to have diesel-LNG dual fuel vehicles rather than LNG-only vehicles because all of the LNG may be completely consumed in the tank prior to storage without any restart issues.
At the refueling station, natural gas vapor is often vented to allow the tank to be filled. Two-Line fill systems are designed to use the venting process to remove heat from the fuel tanks by subcooling the tank contents see Joule-Thomson Effect). Since CNG requires a lot of energy to compress pipeline natural gas, it is much more energy-efficient to pressurize LNG to 3000 or 3600 psig and then vaporize it. It probably makes more sense to use the vent gas at the station to run a stationary engine for power generation or co-generation.
Thank you Frank for that detailed answer. It appears that what we call natural gas is really vapor, even at 100 degrees f. Since the truck fuel system is safe at 4500 psi, it appears the trucker can fill a car CNG tank to 3500 psi, perhaps even if the truck tank is 99% full. Assuming the proper hoses and adapters are available. If the driver has to wait and he is bored, he may be willing to fill cars at only slightly over his cost. The cars may be willing to pay a sizable premium to avoid a long trip to a regular CNG station or wear out their Phill which may use a dollar worth of his electricity, and take 8 hours.
If the LNG is at -245F, it should be practical to repeatedly bubble the vapor, into the liquid, so as to get a very low vapor pressure in the cyrogenic tank, which wil make filling easy without venting, either the truck tank, or the filling station tank. My hand book shows -164 c = -263 f for the boiling point of methane, so impurities and/or considerable pressure is needed to increase the boiling point to -245, unless I am confused. How much pressure can the cyrogenic tank tolerate safely? Please correct and embellish. Neil