Liquid Propane vs Vapor Propane

[Stephen Booth]

Just found this new version of the site and forum, good work. Best Christmas and New Year Greetings from Jakarta.

I am just doing some cost calculations with our Diamond Jet 2700 with both the hybrid and air cooled attachments.

Propane Fuel
We have the flow meter DJF tables with the flows ranging from approximately 62 NLPM (air cooled set up) up to 72 NLPM (hybrid set up)



My question is how to calculate the estimated consumption of the Propane as a gas?



We buy the propane in Cylinders that weigh 45kg each cylinder, which according to our vender the ratio is 1 kg equals 1.9 liter propane, however I am assuming this is propane liquid. How can we calculate the amount of gas at DJ operating pressures to be consumed by the DJ 2700 based on the 45 kg bottle of propane.



The goal is a cost estimate of the process costs.

I expect that one liter liquid propane would produce about 200+ liters of vapour propane at the temperatures and pressures of the operation of the equipment.

Any guidelines

[Gordon]

Hi Stephen

to the Surface Engineering Forum.

Taking the density of propane gas to be 1.83 kg/cubic metre which I think is based on 25 C at atmospheric pressure.

This should give you 546 l/kg @ 25C

Measuring in NLPM, I believe is based on 0 C @ 1 atm.

Correcting using Charles Law V1/T1 = V2/T2 where V = volume (m3 ) T = absolute temperature (K)

We get around 500 l/kg (0 C, 1 atm or NL normal litres)

Hope that helps

[Stephen Booth]

Thanks Gordon, that number seems about right to me. From a USA Website, that is supplying Propane to households, they indicate the liquid to vapor conversion factor at 1:270 which sound reasonable.

On a similar subject, we found that the 45kg tanks of Propane were freezing the lines, regulators and indeed even the flowmeters when the tanks were in the 100% full condition. We were using 3 tanks. We swapped out one full tank (out of the three) with a 1/2 full tank, allowed the sistem to normalize, and the freezing went away. Maybe caused by the full tanks drawing off liquid propane as well as vapor into the lines, the vapor evaporate in the lines, cooling and freezing?? Sound about right.

Thank much for the help.

Hi Stephen

to the Surface Engineering Forum.

Taking the density of propane gas to be 1.83 kg/cubic metre which I think is based on 25 C at atmospheric pressure.

This should give you 546 l/kg @ 25C

Measuring in NLPM, I believe is based on 0 C @ 1 atm.

Correcting using Charles Law V1/T1 = V2/T2 where V = volume (m3 ) T = absolute temperature (K)

We get around 500 l/kg (0 C, 1 atm or NL normal litres)

Hope that helps

[Stephen Booth]

Here is some more information from a vendor

Please find our data below:

Vapor Density (kg/m3)
1 atm abs 280 mmH20 0.4 bar
28oC 30oC 32oC 28oC 30oC 32oC 28oC 30oC 32oC
Propane 1.784 1.773 1.761 1.833 1.821 1.809 2.489 2.472 2.456
Iso-Butane 2.352 2.337 2.321 2.416 2.384 2.384 3.227 3.259 3.238
N-Butane

Regarding these data, you can calculate Propane or LPG (mix Propane & Butane) Vapor actually base on press
ure and temperature your machine.

For example, assume DJ-2700 consumption 72 NLPM and running at condition 28 oC & 1 atm abs.
If we use Propane Pure (99.7%) qty 45 kg, we get 25.22 m3 or equal with 25,224 litre. The machine can operate up to 350 minute.
If we use LPG mix (60% Propane, 40 % Butane) we have Vapor Density 1.97 kg/m3. For qty LPG 50 kg (as usual) we get 25.38 m3 or equal with 25,380 litre. The Machine can operate up to 352.5 minute.
Note : LPG Price more cheaper than Propane Price.

[Gordon]

Hi Stephen

Basically, you need to know the mass of gas in your cylinder and the density of the gas under conditions of use to estimate consumption. Obviously, gas density is dependent on conditions of temperature and pressure. Unfortunately, gas suppliers don't always state the conditions for their gas density or use different temperatures like 25, 20, 15 C or 70, 60 F. If you are using gas flow parameters in NLPM for calculations (which is not necessarily the same as your direct flow meter tube reading, look in process manual for flowmeter reading vs SLPM or NLPM) the gas density value needs to be under conditions of 0 C and 1 atm for your calculations. You only need to consider ambient conditions when first establishing the true flow in NLPM.

Lets take your gas density figure of 1.97 kg/m3, without conditions it is not very helpful. If we say for example conditions are 25C @ 1.0132 bar (1 atm) then we can roughly correct this for 0C @ 1.0132 bar (1 atm) conditions using V1/T1 = V2/T2 where V = volume (m3 ) T = absolute temperature (K)

1 kg of gas with density 1.97 kg/m3 @25C, 1atm will yield 0.508 m3
0C = 273.15K, 25C = 297.15K
V1/T1 = V2/T2 or V2 = V1.T2/T1
V2 = 0.508 x 273.15 / 298.15 = 0.465 m3 for 1 kg gas @ 0C, 1 atm
So corrected density will be 2.15 kg/m3

Changing from propane to a propane/butane mix you may need to consider the different calorific, oxygen requirement and flame temperature differences. This could impact on process and coating quality and may require parameter/coating optimisation.

Propane does suffer problems with drawing liquid or condensation in pipework/flow meters and poor flow stability due to changes in temperature. Warming cylinders/pipework or much better using vaporisers is the best solution to this problem.
http://www.tssea.co.uk/pdf_files/coating...r-2003.PDF

Hope that helps

[Stephen Booth]

Gordon,

Thank you very much for the reply, it is indeed helpful, and answers many questions that I have. The TSSEA Publication was also very helpful.

Thank you very much.

Stephen Booth
Teknokraft Asia
stephen.booth@teknokraft.com

Hi Stephen

Basically, you need to know the mass of gas in your cylinder and the density of the gas under conditions of use to estimate consumption. Obviously, gas density is dependent on conditions of temperature and pressure. Unfortunately, gas suppliers don't always state the conditions for their gas density or use different temperatures like 25, 20, 15 C or 70, 60 F. If you are using gas flow parameters in NLPM for calculations (which is not necessarily the same as your direct flow meter tube reading, look in process manual for flowmeter reading vs SLPM or NLPM) the gas density value needs to be under conditions of 0 C and 1 atm for your calculations. You only need to consider ambient conditions when first establishing the true flow in NLPM.

Lets take your gas density figure of 1.97 kg/m3, without conditions it is not very helpful. If we say for example conditions are 25C @ 1.0132 bar (1 atm) then we can roughly correct this for 0C @ 1.0132 bar (1 atm) conditions using V1/T1 = V2/T2 where V = volume (m3 ) T = absolute temperature (K)

1 kg of gas with density 1.97 kg/m3 @25C, 1atm will yield 0.508 m3
0C = 273.15K, 25C = 297.15K
V1/T1 = V2/T2 or V2 = V1.T2/T1
V2 = 0.508 x 273.15 / 298.15 = 0.465 m3 for 1 kg gas @ 0C, 1 atm
So corrected density will be 2.15 kg/m3

Changing from propane to a propane/butane mix you may need to consider the different calorific, oxygen requirement and flame temperature differences. This could impact on process and coating quality and may require parameter/coating optimisation.

Propane does suffer problems with drawing liquid or condensation in pipework/flow meters and poor flow stability due to changes in temperature. Warming cylinders/pipework or much better using vaporisers is the best solution to this problem.
http://www.tssea.co.uk/pdf_files/coating...r-2003.PDF

Hope that helps

[jeffsays163]

Hi, Steven, great to see you here! This is Jeff, you know who I am, as we meet almost each year. Same as you, I just joined this Forum in Dec. 2007, quite helpful and enjoyable here isn't it?

By the way, I am meeting the same problem when installing my new bought DJ2700, on its propane. Here is very cold so the propane is even liquidized in the flowmeter on the DJC panel. When each time I ignite it with Hydrogen, it light up, with beautiful diamond, then in about 3 - 4 second, it flameout, each time the same. It's really puzzling me, and I always think it has something to do with the propane. Do you have some advices? Maybe somewhere else I should try? Thank you!

See you in this Year!

Jeff.

Gordon,

Thank you very much for the reply, it is indeed helpful, and answers many questions that I have. The TSSEA Publication was also very helpful.

Thank you very much.

Stephen Booth
Teknokraft Asia
stephen.booth@teknokraft.com

Hi Stephen

Basically, you need to know the mass of gas in your cylinder and the density of the gas under conditions of use to estimate consumption. Obviously, gas density is dependent on conditions of temperature and pressure. Unfortunately, gas suppliers don't always state the conditions for their gas density or use different temperatures like 25, 20, 15 C or 70, 60 F. If you are using gas flow parameters in NLPM for calculations (which is not necessarily the same as your direct flow meter tube reading, look in process manual for flowmeter reading vs SLPM or NLPM) the gas density value needs to be under conditions of 0 C and 1 atm for your calculations. You only need to consider ambient conditions when first establishing the true flow in NLPM.

Lets take your gas density figure of 1.97 kg/m3, without conditions it is not very helpful. If we say for example conditions are 25C @ 1.0132 bar (1 atm) then we can roughly correct this for 0C @ 1.0132 bar (1 atm) conditions using V1/T1 = V2/T2 where V = volume (m3 ) T = absolute temperature (K)

1 kg of gas with density 1.97 kg/m3 @25C, 1atm will yield 0.508 m3
0C = 273.15K, 25C = 297.15K
V1/T1 = V2/T2 or V2 = V1.T2/T1
V2 = 0.508 x 273.15 / 298.15 = 0.465 m3 for 1 kg gas @ 0C, 1 atm
So corrected density will be 2.15 kg/m3

Changing from propane to a propane/butane mix you may need to consider the different calorific, oxygen requirement and flame temperature differences. This could impact on process and coating quality and may require parameter/coating optimisation.

Propane does suffer problems with drawing liquid or condensation in pipework/flow meters and poor flow stability due to changes in temperature. Warming cylinders/pipework or much better using vaporisers is the best solution to this problem.
http://www.tssea.co.uk/pdf_files/coating...r-2003.PDF

Hope that helps

[ycwbycwb]

Jeff, are you using heating belt or vaporizer for your DJ?

[jeffsays163]

Hi, ycwbycwb, thank you very much, its such a difficult name though. Now I have finally solved this problem! The causes combined the magnetic valves (those for controlling the ignition etc.), CPU frame and flame detector faults. Before working it out, the DJ2700 had been put away for one year. so its not hard to imagine so many problems it had. My experience is after purchasing a machine, we's better use it, otherwise it will turn bad and losing the warranty. By the way, im using heating belt. Does it make differences? Thank you!

[ycwbycwb]

Hi, Jeff,

In cold days, the heating belt will help me to get enough and stable propane with only one tank.
With vaporizer I can use liquid propane with one hose put at the bottom of the tank.

BR,
ycwbycwb

Hi, ycwbycwb, thank you very much, its such a difficult name though. Now I have finally solved this problem! The causes combined the magnetic valves (those for controlling the ignition etc.), CPU frame and flame detector faults. Before working it out, the DJ2700 had been put away for one year. so its not hard to imagine so many problems it had. My experience is after purchasing a machine, we's better use it, otherwise it will turn bad and losing the warranty. By the way, im using heating belt. Does it make differences? Thank you!

[Stephen Booth]

Hi Jeff, indeed great forum. Glad to hear your got your problem with the DJ 2700 worked out. The heating belts are great items, and will help alot.

[jeffsays163]

Thank you stephen.

[domsmith]

Liquid propane and Vapor propane are two different things. Vapor propane is reasonable than liquid propane. As liquid propane is used in households.
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