Tritiated water removal method based on hydrate formation using heavy water as co-precipitant

Nakamura, Satoshi; Awata, Toshihiro; Kiyokawa, Hitoshi; Ito, Haruki; Ohmura, Ryo

doi:10.1016/j.cej.2023.142979

Cited by 13 publications

(3 citation statements)

References 21 publications

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“…16 Most recently, a novel tritiated water separation method using hydrate was proposed. Nakamura et al, 17 they reported the first ideas by contacting tritiated water with an HFC-134a + D 2 O hydrate substrate, which reduced the tritium concentration in tritium-containing water from 4.77 × 10 5 Bq/kg to 1.55 × 10 3 Bq/kg. Their work reported that the hydrate-based process achieves ultralow tritium concentrations in the order of 10 3 Bq/kg, which any well-established separation method such as cryogenic distillation 18 and catalytic exchange 19 has not reached.…”

Section: Introductionmentioning

confidence: 99%

“…In the hydrate-based process, tritium is concentrated on the surface of the D 2 O hydrate substrate because of the coprecipitation reaction of T 2 O and D 2 O; therefore, the dynamic characteristics of D 2 O-based hydrate with various guest compounds, regardless of HFCs or other greener guests, need to be clarified to develop an efficient process for substrate formation. The process is composed of the following three steps: (i) hydrate formation from the D 2 O and guest compound, (ii) transportation of the hydrate slurry, and (iii) dewatering of the slurry to remove the residual water.…”

Section: Introductionmentioning

confidence: 99%

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Crystal Growth of Clathrate Hydrate Formed with Carbon Dioxide and Deuterium Oxide: Implications for Hydrate-based Tritium Separation

Maruyama,

Dogi,

Ohmura

2024

Energy Fuels

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Tritium separation technology is a key method for treating contaminated water from nuclear power plants. Recently, a novel tritium separation method using deuterium oxide (D 2 O)based clathrate hydrate has attracted attention because it can reduce the tritium concentration in contaminated water from 4.77 × 10 5 Bq/kg to 1.55 × 10 3 Bq/kg. In this hydrate-based tritium separation method, tritium is concentrated on the surface of a D 2 O-based hydrate substrate. The mechanistic characteristics and formation kinetics of D 2 O-based hydrates need to be clarified to develop an efficient process for substrate formation. This study contributes to the process design by revealing the crystal growth of the CO 2 + D 2 O hydrate. The crystal growth behavior of the hydrate formed in the CO 2 + D 2 O system was experimentally observed under different subcooling temperatures (ΔT sub ) at 3.0 MPa. At all ΔT sub , hydrate crystals were formed at the gas−liquid interface and extended along the interface. After the interface was covered, hydrate crystals grew in the liquid phase. The variation in the morphology of CO 2 + D 2 O hydrate depended on ΔT sub . At ΔT sub = 1.6 K, polygonal crystals with side lengths of 0.2−0.6 mm were formed. At ΔT sub = 2.7 K, columnar crystals with a length of 1−2 mm were formed. At ΔT sub ≥ 3.3 K, dendritic crystals were formed. With an increase in ΔT sub , the size of the dendritic branches increased. The crystal growth dynamics and morphological tendency of the CO 2 + D 2 O hydrate were comparable to those of the CO 2 + H 2 O hydrate at fixed ΔT sub . Detailed theoretical discussions on the obtained results of surface kinetics, mass transfer, and heat transfer during hydrate formation from H 2 O and D 2 O were provided, considering the chemical potential, viscosity, and heat transfer of the liquids.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Crystal Growth of Clathrate Hydrate Formed with Carbon Dioxide and Deuterium Oxide: Implications for Hydrate-based Tritium Separation

Maruyama,

Dogi,

Ohmura

2024

Energy Fuels

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“…There are several novel applications utilizing carbon dioxide hydrate such as carbon capture [13], salt manufacture [4][5][6] and carbonated solid foods [7,8]. Tritium water concentration through hydrate formation is an emerging technology that utilizes another unique property of hydrates; host compounds selectivity [9]. To determine an operation condition on these hydrate-based technologies, it is necessary to know the pressure and temperature conditions at which hydrates are formed and decomposed.…”

Section: Introductionmentioning

confidence: 99%

Renewed Measurements of Carbon Dioxide Hydrate Phase Equilibrium

Ito

Gibo

Shiraishi

et al. 2023

Preprint

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This paper investigates phase equilibrium conditions in the carbon dioxide hydrate forming system. Carbon dioxide hydrate can be utilized for carbon capture, salt manufacture, carbonated solid foods and tritium water concentration, so the phase equilibrium conditions have been substantially reported so far. However, the data from previous studies were inconsistent with each other, such as there is a difference of 1.0 K in the phase equilibrium temperature at 2 MPa. In this study, the newly three-phase (water rich liquid + hydrate + carbon dioxide rich vapor) equilibrium conditions in the carbon dioxide hydrate forming system were measured at twenty different temperature conditions within the range of (271.9-282.7) K in the two different laboratories. The six pairs of three-phase equilibrium condition data measured under equivalent pressure conditions were consistent within mutual uncertainties. The internal consistency of the data measured in this study was evaluated by the Clausius-Clapeyron equation. The data measured in this study existed within the uncertainty range of the data from several previous studies.

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