Transient Three-Phase Transport and Dissociation Coupling in Air-Assisted Methane Hydrate Recovery

A transient numerical model is developed for air-assisted recovery of methane hydrate through a vertical pipe. The author’s earlier gas-lift approach is extended with conservative solid transport, separate solid momentum, transported particle number, liquid cooling and distinct air and methane budgets. A moving wet domain represents startup to an outlet above sea level. Air–water measurements assess the hydraulic submodel. Hydrate dissociation, shrinkage and cooling remain predictions conditional on closures requiring hydrate-specific validation. A Japan Sea temperature profile from World Ocean Atlas 2023 supplies the external thermal boundary. For a 500 m intake, a 2 m pipe and 13.2 Nm3 s−1 air injection at 300 m, predicted developed liquid delivery is approximately 38.5 m3 s−1, with 1069.4 kg s−1 of hydrate and 103.3 kg s−1 of methane gas. Dissociation increases liquid delivery by approximately 21.9% relative to the nonreactive case and cools the upper liquid by approximately 1.6 K. External stratification produces no appreciable delivery change in this configuration. Freezing-limited sensitivity, profile refinement checks and an explicitly assumed compressor work calculation qualify the thermal, numerical and engineering interpretation. The framework distinguishes startup, throughput and methane product form with explicit air and methane accounting.