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Engineering ToolBox > Propane Butane Mix Evaporation Pressure
It is common to distribute a mixture of propane (C3H8) and butane (C4H10) (LPG) for combustion purposes.
Propane is more suited to colder environments since it evaporates at -44oF (-42oC) at atmospheric pressure. Butane evaporates at 33oF (-0.5 oC) at atmospheric pressure.
The vapor pressure of a mixture of the two products can be found in the table below:
| Vapor Pressure (psig) | ||||||
| Mixture | Propane (C3H8) (%) | 100 | 70 | 50 | 30 | 0 |
| Butane (C4H10) (%) | 0 | 30 | 50 | 70 | 100 | |
| Temperature (oF) | -44 | 0 | 0 | 0 | 0 | 0 |
| -30 | 6.8 | 0 | 0 | 0 | 0 | |
| -20 | 11.5 | 4.7 | 0 | 0 | 0 | |
| -10 | 17.5 | 9 | 3.5 | 0 | 0 | |
| 0 | 24.5 | 15 | 7.6 | 2.3 | 0 | |
| 10 | 34 | 20.5 | 12.3 | 5.9 | 0 | |
| 20 | 42 | 28 | 17.8 | 10.2 | 0 | |
| 30 | 53 | 36.5 | 24.5 | 15.4 | 0 | |
| 40 | 65 | 46 | 32.4 | 21.5 | 3.1 | |
| 50 | 78 | 56 | 41 | 28.5 | 6.9 | |
| 60 | 93 | 68 | 50 | 36.5 | 11.5 | |
| 70 | 110 | 82 | 61 | 45 | 17 | |
| 80 | 128 | 96 | 74 | 54 | 23 | |
| 90 | 150 | 114 | 88 | 66 | 30 | |
| 100 | 177 | 134 | 104 | 79 | 38 | |
| 110 | 204 | 158 | 122 | 93 | 47 | |
Note that the evaporation temperature is not the only parameter that influence on the evaporation of the propane butane mixture. The evaporation requires heat and if the heat transfer to the liquid gas is limited the liquid will be under cooled and the evaporation reduced. Larger consumes requires in general heat exchangers fueled with hot water, electric heater or combustion of the propane butane mix itself. Smaller amounts of consumption requires containers with efficient heat transfer. By example composite container provides less heat transfer compared with steel containers.
