Session: Raymond Viskanta Memorial Symposium-06: Thermal Management and Phase Change

Paper Number: 106685

106685 - Intensification of Mass and Heat Transfer for Hydrates-Based Gigascale Seabed Sequestration of Carbon Dioxide 

Significant carbon sequestration capacity (up to 10 Gigatons/yr) will be needed by 2050 to limit the Earth’s temperature rise to < 1.5 ºC. Currently, geologic injection of CO₂ (depleted oil-gas reservoirs, saline aquifers) is the only mature technology, which can be deployed at industrial scales. However injection has significant limitations with respect to available geology (globally), CO₂ leakage and area footprint of injection projects. CO₂ hydrates provide an alternative option for carbon sequestration on the seabed. CO₂ hydrates are ice-like crystalline solids which form under medium pressure and low temperature conditions from water (cage of host molecules) and gas or liquid (guest molecule). Stable CO₂ hydrates form at ~0 ̊C, and at moderate pressures (~500 psi) from a mixture of CO₂ and water. Prevalence of such conditions on the seabed makes it a very attractive location for gigascale CO₂ sequestration. From a technical standpoint, success of this concept requires rapid synthesis of CO₂ hydrates and sealing them (to prevent dissociation) for long-term sequestration (> 1000 yrs).

A significant technological barrier to any application involving hydrates has always been the sluggish rate of formation of hydrates, which can be attributed to thermodynamic and kinetics-related limitations. Hydrates are notorious for their slow formation (nucleation and growth) under artificial synthesis. However, via appropriate intensification of mass and heat transfer, very high hydrate formation rates can be achieved. This paper will overview recent efforts in my group which uncover multiple techniques to speed up hydrate formation by one-two orders of magnitude. These techniques intensify the mass and heat transfer associated with hydrate formation and include gas bubble sparging, electronucleation, use of metal catalysts, and high thermal conductivity foams. Multiple innovations can be combined to speed up CO₂ hydrate formation by >30 times state of art (Sequestration rate> 800 gm CO₂/hr/liter (reactor volume)). First-principles-based modeling will be discussed to study the impact of process parameters on key parameters (formation rate, water-to-hydrate conversion efficiency) associated with hydrate formation. This study will also briefly outline various approaches for sealing CO₂ hydrates and discuss location mapping of potential storage sites.

Presenting Author: Vaibhav Bahadur The University of Texas at Austin