NGV Pressure at 200Bar

At low pressure you won't be able to store much gas....it's as simple as that.

At 200 bar you can get 200 times more into your tank than you can at 1bar.
(Actually it's probably even more as it becomes liquid...but let's keep it simple)

Del

It's so as to store enough mass in such a small volume to provide sufficient range before recharging becomes due.

Dear dkwarner,

Thank you very much of your very good explaination,I hv noticed some Natural gas station with delivered pressure at 250Bar ,some at 180Bar at higher pressure i will get more storage of CNG.

Pls advise me how to calculate the compressed volume in my 65Liter tank at 200Bar and 250Bar respectively.

Thank you in advance

Since methane is essentially an ideal gas at or near room temperature, it behaves according to the standard gas equation:PV=nRT, or P₁V₁=P₂V₂.

That is to say that the volume of a given amount of gas is inversely proportional to the pressure. The amount of gas that occupies 1 liter of volume at 1 Bar will occupy 1/200 of a liter at 200 Bar and 1/250 of a liter at 250 Bar.

In other words, multiply the volume of your tank in liters by the pressure in Bar, and you have the atmospheric pressure volume of the gas in the tank: 65*200=13,000 liters; 65*250=16,250 liters.

Why 'inversely proportional', its direct proportional as you have done in your calcs.

Quoting my previous post: "... volume of a given amount of gas is inversely proportional to the pressure" (Underlining added just now)

For a given amount (number of molecules, or weight) of gas, as you increase the pressure, the volume goes down. That is an inverse proportion.

For a given volume of tank, the amount (number of molecules, or weight) of gas held by the tank is directly proportional to the pressure. That is a direct proportion.

Dear dkwarner,

Thank you very much of your explaination.

Regards

Dear dkwarner,

Thank you for your very good explaination,here with i have another question maybe is out of NGV natural gas but it also related to Natural gas - meter reading .

In my working place we were using natural gas for combustion purpose , i hv noticed that the metering unit in Nm³ / hr with pressure at 0.6 Bar , so the actual meter reading unit must by multiply by what formula , can you explode little more about this topic ?

Thank you very much in advance

Again, if the temperatures are allowed to become equal, the gas law becomes P₁V₁=P₂V₂, which can be rewritten as V₂=V₁*P₁/P₂. You can use any units you like for both pressure and volume, since the units cancel, but the pressure values must be absolute pressures, not gauge pressures. Since 0.6 Bar would be a partial vacuum if it were an absolute pressure, I have to assume it is a gauge pressure, so the absolute pressure would be 1.6 Bar.

Thus V₂=V₁*1.6/1, so the volume of gas after expanding and warming to the original temperature will be 1.6 times the original volume.

Presumably, Nm³ / hr means Normal m³ / hr, or m³ / hr at normal (1 Bar) pressure. The meter should have been designed/calibrated to automatically include that calculation, so the value it indicates is presumably already a corrected value.

Again, I'm assuming that Nm3 means Normal cubic meters, or cubic meters at STP (Standard Temperature and Pressure, 20°C@1 bar). A liter is also a cubic decimeter, so there are 1000 liters in 1 cubic meter.

Then 600 Nm3=600,000 liters. If you allow the gas to expand so the pressure drops from 200 bar to 1 bar, there will be considerable cooling, so heat will have to be added to bring it back up to the original temperature. Once the heat has been added, the volume will have increased by a factor of 200, so you now have 600,000 * 200 = 120,000,000 liters of gas. That is also 120,000 m³.

Natural gas is mostly methane, and has a density at STP of about 0.7 kg/m³, so your 120,000 m³ of gas will have a mass of about 84,000 kg, or 84 metric tons.