Freezing point of eutectic NaCl brine is -21 C. How is the freezing point temperature effected by presence of organic compounds like methane, ethane and propane and compounds like H2S and CO2? At high pressures of around 800 bars, H2S solubility in water is as high as 3-4 mole percentage. Is the freezing point temperature of eutectic NaCl brine saturated with H2S at around 800 bars pressure around -26 C?
H2S and CO2 make acidic ions that lower the freezing point a predictable way. Methane, ethane, and propane make low temperature hydrates with water in LPG that freeze in ways that hinder operations. But in mostly water brine solution the light components accumulate in the surface film and are not good predictors of freezing point.
Freezing point depression is the lowering of the equilibrium freezing or melting temperature by solutes in the liquid phase. Solutes in the liquid phase also raise the equilibrium boiling temperature. Pressure also affects freezing temperature (a little) and boiling temperatures (a lot). H2S and CO2 make acidic ions that lower the freezing point a predictable way. The methane which eventually ends up trapped as hydrate compounds comes from microorganisms that produce methane as a byproduct of consuming buried detrital organic materials. The amount and rate of hydrate accumulation is determined by the methane supply.
The five components that you mention are hydrate formers, so it is more likely that you will from hydrate than ice (depending on your initial salt concentration, so hydrate, then halites as you used up the water), if you are working at low pressure and not forming hydrates, then H2S and CO2 will have a slight lowering effect on the effect on the freezing point. It is negligible for the mentioned HCs as their solubility is too low to affect significantly the water activity.
- Badges
- Science topic
- Similar topics
- Engineering
- Petroleum Engineering