What Does Thermodynamic Hydrate Inhibitor (THI) Mean?
A thermodynamic hydrate inhibitor (THI) is a chemical substance used to balance the reactions between hydrocarbons and water that result in the formation of crystalline compounds. Thermodynamic hydrate inhibitors do this by shifting the crystalline equilibrium curve in a direction that lowers the reaction temperature to a level that impedes compound formation. Crystalline build-up in pipelines is reduced when a thermodynamic hydrate inhibitor is used as an additive.
Corrosionpedia Explains Thermodynamic Hydrate Inhibitor (THI)
Two main thermodynamic hydrate inhibitors are commonly used: methanol and monoethylene glycol (MEG).
A thermodynamic inhibitor is sensitive to changes in subsystem cooling. Therefore, the rate that an inhibitor is injected into a system must correlate to temperature changes within the system. In the case of methanol, ideal operating conditions are about 0.5°C (33°F). A methanol injection of 40% by volume in an aqueous phase is required to prevent hydrate crystalline formation.