prakashmukho

Three methods of preventing hydrate formation in pipelines and processing facilities are commonly used in our industry. These are:
1) Maintain the T & P of the system outside of the hydrate formation region.
2) Dehydrate the gas to remove the water.
3) Inhibit hydrate formation with chemical inhibitors.

Option 3 is commonly used when it is impractical or uneconomic to install dehydration facilities, typically glycol dehydration. There are a number of chemicals used to inhibit hydrate formation, but generally fall into one of two types: equilibrium (sometimes called thermodynamic) inhibitors or kinetic inhibitors. Equilibrium inhibitors lower the equilibrium hydrate formation point and include polar chemicals such as alcohols, glycols and salts. Kinetic inhibitors (often referred to as Low Dosage Hydrate Inhibitors, LDHIs) do not change the equilibrium hydrate formation condition but instead modify the rate at which hydrates form or the ability of hydrate crystals to agglomerate into a plug that could block flow.

The most commonly used equilibrium inhibitors used in the upstream and midstream sectors of the oil and gas business are: monoethylene or diethylene glycol (MEG or DEG) and methanol. In general, glycols are more commonly used in systems requiring continuous inhibition. The glycol is typically recovered, regenerated and recirculated. Methanol is more commonly used in systems that do not require continuous inhibition, i.e. systems only requiring inhibition during cold weather or upset conditions. In addition, methanol is not commonly recovered and reused. This is due to the difficulty of separation of the methanol from water. There are obviously exceptions to this, methanol is used as a continuous inhibitor in a few offshore installations and in a handful of gas processing facilities. Another significant disadvantage of methanol relative to glycol is the high methanol losses to both the liquid hydrocarbon and vapor phase.

The purpose of this thread is to discuss various hand calculation/BRE-Promax VLE data/HYSYS evaluation for methanol-hydrocarbon systems and to decide for correctness in correlations that we may used to estimate methanol losses to the vapor phase.