# C243 – TP-15 2007 Vapour Pressure Calculation for NGLs

## Description

This calculates the equilibrium vapour pressure of natural gas liquids based on their relative density and process temperature.

## References

API MPMS 11.2.5/GPA Technical Publication TP-15 – A Simplified Vapor Pressure Correlation for Commercial NGLs September 2007

Kelton calculation reference C243

FLOCALC calculation reference F058

KIMS calculation reference K198

## Options

### Method

- New

- Modified

Choose option based on which method you wish to employ. The modified method requires the vapour pressure at 100°F as an input.

## Constants

Gas coefficients

C = 443°F

D = 543°F

Table 1: Parameters for vapour pressure correlation

Range | A_{0} |
A_{1} |
A_{2} |
B_{0} |
B_{1} |
B_{2} |
---|---|---|---|---|---|---|

0.35 ≤ γ60 < 0.45 | 17.5297 | -24.604 | 24.373 | -6567.6 | 19322 | -24693.3 |

0.45 ≤ γ60 < 0.49 | 7.9907 | 7.562 | 0 | 1895.5 | -10596.9 | 0 |

0.49 ≤ γ60 < 0.51 | -6.4747 | 37.083 | 0 | 12038 | -31296.5 | 0 |

0.51 ≤ γ60 < 0.56 | 11.5454 | 1.749 | 0 | 1378.8 | -10396.1 | 0 |

0.56 ≤ γ60 < 0.585 | 6.4827 | 10.79 | 0 | 3721.5 | -14579.5 | 0 |

0.585 ≤ γ60 < 0.625 | 6.5412 | 10.69 | 0 | 6514.5 | -19353.9 | 0 |

0.625 ≤ γ60 ≤ 0.676 | 20.8537 | -12.21 | 0 | -6765.6 | 1894.3 | 0 |

## Calculation

### Vapour Pressure

The equilibrium vapour pressure is calculated by:

#### New Method

#### Modified Method

Where | ||
---|---|---|

T | = | Process temperature |

P_{100} |
= | Vapour pressure at 100°F |

A | = | Coefficient based on Table 1 “A_{x}” parameters and relative density |

B | = | Coefficient based on Table 1 “B_{x}” parameters and relative density |

C | = | Gas coefficient C |