Initial Hydration Research Articles

Experimental study on solid particle migration and production behaviors during marine natural gas hydrate dissociation by depressurization

Sand production is one of the main obstacles restricting gas extraction efficiency and safety from marine natural gas hydrate (NGH) reservoirs. Particle migration within the NGH reservoir dominates sand production behaviors, while their relationships were rarely reported, severely constrains quantitative evaluation of sand production risks. This paper reports the optical observations of solid particle migration and production from micrometer to mesoscopic scales conditioned to gravel packing during depressurization-induced NGH dissociation for the first time. Theoretical evolutionary modes of sand migration are established based on experimental observations, and its implications on field NGH are comprehensively discussed. Five particle migration regimes of local borehole failure, continuous collapse, wormhole expansion, extensive slow deformation, and pore-wall fluidization are proved to occur during depressurization. The types of particle migration regimes and their transmission modes during depressurization are predominantly determined by initial hydrate saturation. In contrast, the depressurization mainly dominates the transmission rate of the particle migration regimes. Furthermore, both the cumulative mass and the medium grain size of the produced sand decrease linearly with increasing initial methane hydrate (MH) saturation. Discontinuous gas bubble emission, expansion, and explosion during MH dissociation delay sand migration into the wellbore. At the same time, continuous water flow is a requirement for sand production during hydrate dissociation by depressurization. The experiments enlighten us that a constitutive model that can illustrate visible particle migration regimes and their transmission modes is urgently needed to bridge numerical simulation and field applications. Optimizing wellbore layout positions or special reservoir treatment shall be important for mitigating sand production tendency during NGH exploitation.

Assessment of water absorption characteristics for improved sesame (Sesamum indicum L.) varieties during hydration

AbstractThe water absorption characteristics of sesame varieties (GT‐3, GT‐4, GJT‐5, GT‐6, and TKG‐22) were studied during hydration at temperatures ranging 35–55°C. The Peleg model adequately defined the hydration behavior of sesame seed varieties at the 35°C, 45°C, and 55°C soaking temperatures with the comparable coefficient of determination (R2) and mean relative percentage deviation modulus (P). The Peleg rate constant K1 and the capacity constant K2 reduced significantly with the rise in hydration temperatures, suggesting corresponding increases in the initial hydration rate as well as the equilibrium moisture content in all the varieties tested. The Arrhenius equation was used to calculate the activation energy (Ea) of GT‐3, GT‐4, GJT‐5, GT‐6, and TKG‐22 sesame varieties and was noted to be 38.74, 33.37, 30.68, 37.85, and 33.23 kJ/mol, respectively. The enthalpy (H) was raised significantly with hydration temperature while entropy (ΔS) and released energy (ΔG) were found nonsignificant (p > 0.05).

Numerical Simulating the Influences of Hydrate Decomposition on Wellhead Stability

Natural gas hydrate reservoir has been identified as a new alternative energy resource which has characteristics of weak cementation, low reservoir strength and shallow overburden depth. Thus, the stability of subsea equipment and formation can be affected during the drilling process. To quantitatively assess the vertical displacement of the formation induced by hydrate decomposition and clearly identify the influence laws of various factors on wellhead stability, this study established a fully coupled thermo-hydro-mechanical-chemical (THMC) model by using ABAQUS software. The important factor that affects the wellhead stability is the decomposition range of hydrates. Based on this, the orthogonal experimental design method was utilized to analyze the influence laws of some factors on wellhead stability, including the thickness of hydrate formation, initial hydrate saturation, overburden depth of hydrate sediment, and mudline temperature. The results revealed that the decomposition of hydrate weakens the mechanical properties of the hydrate formation, thus leading to the compression of the hydrate formation, further causing the wellhead subsidence. When the duration of drilling operations was 24 h and no decomposition of natural gas hydrate occurs, the wellhead subsidence is recorded at 0.053 m, this value increases with an increase in drilling fluid temperature. The factors were listed in descending order as following, according to their significance of influences on wellhead stability: the thickness of hydrate formation, initial hydrate saturation, overburden depth of hydrate sediment, and mudline temperature. Among the above factors, statistical significance of the mudline temperature was less than 15% confidence level, suggesting that the effect of mudline temperature on wellhead stability is negligible. These findings not only confirm the influence of hydrate decomposition on wellhead stability, but also suggest important implications for the drilling of hydrate-bearing formation.

Review of the Interactions between Conventional Cementitious Materials and Heavy Metal Ions in Stabilization/Solidification Processing.

In the past few decades, solidification/stabilization (S/S) technology has been put forward for the purpose of improving soil strength and inhibiting contaminant migration in the remediation of heavy metal-contaminated sites. Cement, lime, and fly ash are among the most common and effective binders to treat contaminated soils. During S/S processing, the main interactions that are responsible for improving the soil's behaviors can be summarized as gelification, self-hardening, and aggregation. Currently, precipitation, incorporation, and substitution have been commonly accepted as the predominant immobilization mechanisms for heavy metal ions and have been directly verified by some micro-testing techniques. While replacement of Ca2+/Si4+ in the cementitious products and physical encapsulation remain controversial, which is proposed dependent on the indirect results. Lead and zinc can retard both the initial and final setting times of cement hydration, while chromium can accelerate the initial cement hydration. Though cadmium can shorten the initial setting time, further cement hydration will be inhibited. While for mercury, the interference impact is closely associated with its adapted anion. It should be pointed out that obtaining a better understanding of the remediation mechanism involved in S/S processing will contribute to facilitating technical improvement, further extension, and application.

Navigating nutrition and hydration care in the adult patient with short bowel syndrome.

Attending diligently to the nutrition and hydration needs of patients with short bowel syndrome (SBS) is a key tenet of their care, both postoperatively and in the years that follow. For, without each, patients are left to themselves to navigate the nutrition consequences of SBS, including malnutrition, nutrient deficiencies, renal compromise, osteoporosis, fatigue, depression, and impaired quality of life. The intent of this review is to discuss the initial nutrition assessment, oral diet, hydration, and home nutrition support for the patient with SBS.

Nature of the physicochemical process in water photolysis uncovered by a computer simulation.

In this work, we investigate the physicochemical process of water photolysis to bridge physical and chemical processes by a newly developed first-principles calculation code. The deceleration, thermalization, delocalization, and initial hydration of the extremely low-energy electrons ejected by water photolysis are sequentially tracked in the condensed phase. We show herein the calculated results for these sequential phenomena during 300fs. Our results indicate that the mechanisms heavily depend on the intermolecular vibration and rotation modes peculiar to water and the momentum transfer between the electrons and the water medium. We suggest that using our results for the delocalized electron distribution will reproduce successive chemical reactions measured by photolysis experiments using a chemical reaction code. We expect our approach to become a powerful technique for various scientific fields related to water photolysis and radiolysis.

Investigation of initial hydration and rehydration of geosynthetic clay liners from sandy subgrades via X-ray computed tomography images

The hydraulic conductivity of geosynthetic clay liners (GCLs) widely used as barrier systems considerably depends on their hydration status after the initial hydration of virgin GCLs and the rehydration of desiccated GCLs. Free hydration tests were performed on virgin and desiccated GCLs over sandy subgrades to compare their hydration level. In addition, high-resolution micro-X-ray computed tomography (CT) images of both GCLs and sandy subgrades with different gravimetric water content (i.e. 15%, 20%, and 25%) after the initial hydration were analyzed for better insights. The results show significant influences of subgrade water content on moisture content and thickness of virgin GCLs. Water loss of sandy subgrades and the time interval necessary for reaching a steady state of desiccated GCLs during rehydration was greater and longer than virgin GCLs during initial hydration. X-ray CT images verified a dense distribution of bentonite particles, macropores, and minor desiccation cracks that existed in poorly-hydrated GCLs over unsaturated sand. On the other hand, the completely saturated sandy subgrade facilitated the hydration of GCLs, leaving a lot of macropores in the sand. The relationship between water distribution and the frequency of macropore generation observed in the upper contact zone of sandy subgrades was also indicated via these X-ray CT images.

SDS-promoted methane hydrate growth in presence of a superhydrophobic substrate

As one of the most efficient promoters for methane hydrate formation, SDS (sodium dodecyl sulfate) works mainly by causing the hydrates to grow upwards along the reactor sidewall. In this work, super-hydrophobic surface was constructed and adopted for methane hydrate formation, in the aim of revealing the promotion mechanism of SDS. Morphological observations showed that SDS led to violent fluctuation at the gas/liquid interface, which represented the unstable state of the gas/liquid interface during the initial hydrate growth process and reached stable via morphology transformation, either upward growth or outward diffusion, leading to the surface growth of methane hydrates. In-situ Raman Spectra revealed that the fluctuation structure was the combination of water, hydrate mass with cages minorly occupied by methane molecules, and methane hydrates; and with the continuation of the fluctuation phenomenon, the water percentage decreased, the hydrate mass increased and then transformed to methane hydrates gradually.

Structure and thermodynamics of water adsorption in NU-1500-Cr

Metal-organic frameworks (MOFs) are a class of materials with diverse chemical and structural properties, and have been shown to effectively adsorb various types of guest molecules. The mechanism of water adsorption in NU-1500-Cr, a high-performance atmospheric water harvesting MOF, is investigated using a combination of molecular dynamics simulations and infrared spectroscopy. Calculations of thermodynamic and dynamical properties of water as a function of relative humidity allow for following the adsorption process from the initial hydration stage to complete filling of the MOF pores. Initial hydration begins at the water molecules that saturate the open Cr3+ sites of the framework, which is then followed by the formation of water chains that extend along the channels connecting the hexagonal pores of the framework. Water present in these channels gradually coalesces and fills the hexagonal pores sequentially after the channels are completely hydrated. The development of hydrogen-bond networks inside the MOF pores as a function of relative humidity is characterized at the molecular level using experimental and computational infrared spectroscopy. A detailed analysis of the OH-stretch vibrational band indicates that the low-frequency tail stems from strongly polarized hydrogen-bonded water molecules, suggesting the presence of some structural disorder in the experimental samples. Strategies for designing efficient water harvesting MOFs are also proposed based on the mechanism of water adsorption in NU-1500-Cr.

Co-deposition characteristics of hydrates and sands in gas-salty water-sands flow system

The study of hydrate flow assurance is critical for the efficient and safe development of natural gas hydrates. The natural gas produced by the dissociation of hydrate may re-hydrate in the gathering pipeline, and even lead to the blockage of the gathering pipeline. However, the co-deposition mechanism of the Micron-sized Sand Particles(MSPs) produced in the exploitation, and natural gas hydrate particles during pipeline transportation is still unclear. Therefore, the hydrates and MSPs slurry flow law and co-deposition mechanism are studied by horizontal high-pressure flow loop experiments. A new method to calculate the thickness of the deposition layer for water-dominant systems is proposed. Then, based on the variation of deposition layer thickness, the solid deposition process and flow behaviors are discussed in the pure water system, the salt-containing system, the sand-containing system, and the salt-sand coexistence system, respectively. The results show that the hydrate-MSPs co-deposition process is divided into five stages in the salt-sand coexistence system: the initial deposition stage, hydrate formation and adhesion on the pipe wall stage, rapid deposition stage, deposition layer sloughing stage, and stable deposition stage. And the hydrate-MSPs co-deposits in various stages are characterized by the Hydrate Aggregates Deposition Rate, the Hydrate Aggregates Deposition Layer Thickness, and the particle Chord Length Distribution. The influence of sand particle concentration and initial flow velocity on the hydrate-MSPs co-deposition process in the salt-sand coexistence system is also explored. In addition, the interaction between particles in the deposition process is revealed by Particle Vision and Measurement. The findings of this work provide insights into the solid deposition process in the salt-sand coexistence system, which is beneficial for flow assurance in natural gas hydrate production.

Coupling Amino Acid with THF for the Synergistic Promotion of CO2 Hydrate Micro Kinetics: Implication for Hydrate-Based CO2 Sequestration

CO2 capture and sequestration are broadly recognized as the most effective technology for reducing CO2 emissions and mitigating global climate change. In this regard, hydrate-based CO2 sequestration (HBCS) has been proposed as an effective method for long-term safe and stable CO2 sequestration. It is a promising technology for reducing the concentration of CO2 in the atmosphere and achieving carbon neutrality. However, one major challenge related to HBCS technology is the lack of understanding of how to improve the formation kinetics of CO2 hydrate effectively. Herein, in this study, we identified the synergistic promotion effect on CO2 hydrate formation when a low-dose thermodynamic promoter (tetrahydrofuran, THF) is coupled with an environment-friendly kinetic promoter (l-methionine, l-Met). Based on the kinetic experiments and the morphological observation, 0.6 mol % THF coupled with 0.1 wt %l-Met yields the optimal CO2 gas uptake. In situ Raman spectra reveal the mechanism of the observed two-step growth behavior at the molecular level, where low-dose THF promotes the initial CO2-THF sII hydrate nucleation and growth in the solution and l-Met promotes the subsequent CO2 sI hydrate growth along the surface of the reactor. Our study unveils the underlying synergistic mechanism when thermodynamic and kinetic promoters are coupled for CO2 hydrate formation. The results provide guidance for the identification and use of novel bio-friendly thermodynamic and kinetic promoters and are beneficial to a series of sustainable hydrate-based technologies when fast CO2 formation is required.

Effect of Residual Water in Sediments on the CO2-CH4 Replacement Process

CO2 replacement is a promising method of gas hydrate recovery. However, the influence of residual water in the replacement process and selections of a suitable mining area remain uncertain. To better understand this method, we examined the influence of the particle size and initial hydrate saturation on the replacement process while using the same amount of residual free water. The results showed that during the replacement process, two stages of rapid reaction and slow reaction occurred, which were manifested by the speed of pressure change in the reactor. The CO2 sequestration ratio decreased with the increase in sediment particle size and increased with the increase in initial hydrate saturation. During the replacement process, two reactions occurred: CH4 was replaced by CO2 and CO2 hydrate was formed, and the replacement amount and recovery efficiency of CH4 increased with a decrease in sediment particle size. When the sediment particle size was less than 166 μm, the CH4 recovery efficiency was significantly affected by the particle size. The replacement amount of CH4 increased with the increase in initial hydrate saturation, and the recovery efficiency decreased. This study provides a basis for selecting suitable hydrate-accumulation areas for on-site mining.

Influence of MgAl-LDHs/TiO2 composites on the mechanical and photocatalytic properties of cement pastes and recycled aggregates

To study the effects of MgAl-LDHs/TiO2 on the properties of cement paste and recycled aggregates, MgAl-LDO (MgAl-LDHs calcined products) and TiO2 were mixed during the reconstruction of MgAl-LDHs laminates based on the memory effects of layered double hydroxides (LDHs), and then MgAl-LDHs/TiO2 was synthesized. The performance changes were characterized with hydration heat tests, the microscopic morphologies of the hydration products, and the physical and mechanical properties of the cement paste. The effect of the MgAl-LDHs/TiO2 on the multi-interfacial transition zone (ITZ, the interface between the old paste and new paste) of the recycled aggregates was characterised with the micromorphology, meso-mechanical properties, and element diffusion behaviour. The photocatalytic activity of MgAl-LDHs/TiO2 loaded on recycled aggregate was evaluated with the degradation of methylene blue under sunlight. The results showed that the addition of MgAl-LDHs/TiO2 promoted the initial hydration of ordinary Portland cement (OPC) and induced and promoted the growth and formation of crystalline cement hydration products. The initial setting time and final setting time were shortened, and the compressive strength of the hardened paste was improved when MgAl-LDHs/TiO2 was added to the cement paste. The MgAl-LDHs/TiO2 compacted the recycled aggregates and improved the structural properties of the ITZ. The MgAl-LDHs/TiO2 altered diffusion within the ITZ. The total efficiency for the degradation of methylene blue by the 5–10 mm MgAl-LDHs/TiO2 loaded on recycled aggregate reached 82.2% after 80 min under simulated sunlight.

Hydration characteristics, hydration products and microstructure of reactive powder concrete

Reactive Powder Concrete (RPC) is a new type of cementitious materials with a complex hydration mechanism, and active admixtures greatly influence the hydration reaction, formation of hydration products, and evolution of microstructure. In order to comprehensively study the quantitative effects of active admixtures contents, namely silica fume, slag and fly ash, on hydration characteristics, hydration products, and microstructure of RPCs, tests of workability, setting time, electrical conductivity, bound water and mechanical properties were conducted. Furthermore, a series of properties including morphology and micro-structure characteristics of RPCs were analyzed by thermogravimetric (TG) analysis, X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), mercury intrusion porosimetry (MIP), Brunauer-Emmet-Teller (BET), and scanning electron microscope (SEM). The results indicate that the initial hydration reaction rate of RPCs is reduced by partly replacing cement with active admixtures. The pozzolanic effect created by the active admixtures enhances hydration and improves RPC's compressive and flexural strength. RPCs made of cement-silica fume mixture exhibit the best macroscopic properties. The adoption of silica fume promotes the production of C–S–H gel during hydration and exerts pozzolanic and crystal nucleation effects to promote cement hydration. RPCs made of pure cement exhibit 15.3% porosity after 28 days of hydration, with the largest proportion of less harmful pores in the microstructure. The porosity is reduced to 5.2% when cement is partially replaced with silica fume, and the microstructure is dominated by harmless pores. When replacement of silica fume is kept at 25%, using slag powder or fly ash substitute part of cement also reduces the number of less harmful pores. It is beneficial to add slag powder to increase the number of gel pores, whereas fly ash reduces the number of gel pores. The investigation presented in this paper would contribute to the production of low cost and environmentally-friendly RPCs, and accelerate the wider applications of ultra-high performance concrete (UHPC) in engineering structures.

Probing Local Environments of Oxygen Vacancies Responsible for Hydration in Sc-Doped Barium Zirconates at Elevated Temperatures: In Situ X-ray Absorption Spectroscopy, Thermogravimetry, and Active Learning Ab Initio Replica Exchange Monte Carlo Simulations

Proton-conducting oxides, specifically heavily Sc-doped barium zirconate perovskite, have attracted attention as electrolytes for intermediate-temperature protonic ceramic fuel cells because of their high proton conductivity and high chemical stability against carbon dioxide in that temperature regime. Hydration is a key reaction for incorporating protons by filling oxygen vacancies, VO, with hydroxyl groups and activating proton conduction in the perovskite. However, probing the local environment of oxygen vacancies responsible for hydration is challenging because the behavior depends on the temperature and water partial pressure, which necessitates in situ observations and calculations of the local environments at elevated temperatures. To obtain such information, we combined in situ X-ray absorption spectroscopy (XAS) for both the Sc and Zr K-edges, thermogravimetry, X-ray diffractometry, and active learning ab initio replica exchange Monte Carlo (RXMC) simulations in undoped and 20–40 at % Sc-doped barium zirconates at and below 800 °C. The presence of oxygen vacancies adjacent to Sc and Zr in the dehydrated samples and the hydration of these oxygen vacancies under a wet atmosphere were probed by in situ XAS for Sc and Zr pre-edges at elevated temperatures. Here, the microscopic hydration linearly responds to the macroscopic degree of hydration. RXMC sampling further supports the presence of Sc-VO-Zr and Sc-VO-Sc environments. An initial hydration occurs in the Sc-VO-Zr environment at and above 600 °C, but the Sc-VO-Sc environment contribution is greater at higher degrees of hydration. The Zr-Vo-Zr environment is the least abundant among them for the whole temperature range examined and thus has a negligible impact.

THMC Fully Coupled Model of Natural Gas Hydrate under Damage Effect and Parameter Sensitivity Analysis

In order to study the influence of damage on the gas production of natural gas hydrate, a multi-physical field theoretical model considering damage effect and coupling thermal-hydraulic-mechanical-chemical (THMC) was established by theoretical analysis and numerical simulation. The THMC model establishes the relationship between the elastic modulus of hydrate sediment and hydrate saturation during the whole process of hydrate decomposition. The THC (thermal-hydraulic-chemical) and THMC fully coupled models not considering or considering the damage effect were compared and analyzed, and the reliability of the THMC fully coupled model was verified. On this basis, the deformation, permeability and damage of hydrate sediments under different initial hydrate saturations and different depressurization amplitudes, as well as the hydrate gas production rate and cumulative gas production, are analyzed. The results showed that higher initial hydrate saturation inhibited the development of damage, maintained stable gas production and increased cumulative gas production. Larger depressurization promoted damage and increased cumulative gas production, but it was easy to cause stability problems.

Utilization of Gasification Coarse Slag Powder as Cement Partial Replacement: Hydration Kinetics Characteristics, Microstructure and Hardening Properties.

Coal gasification coarse slag (GFS) is a byproduct of coal gasification technology, which contains abundant amorphous aluminosilicate minerals. GFS has low carbon content, and its ground powder has potential pozzolanic activity, which can be used as a supplementary cementitious material (SCM) for cement. Herein, GFS-blended cement was studied in terms of ion dissolution characteristics, initial hydration kinetics, hydration reaction process, microstructure evolution process, and the development of the mechanical strength of their paste and mortar. Enhanced alkalinity and elevated temperature could increase the pozzolanic activity of GFS powder. The specific surface area of GFS powder and its content did not change the reaction mechanism of cement. The hydration process was divided into three stages: crystal nucleation and growth (NG), phase boundary reaction (I), and diffusion reaction (D). A higher specific surface area of the GFS powder could improve the chemical kinetic process of the cement system. The degree of reaction of GFS powder and blended cement had a positive correlation. A low GFS powder content (10%) with a high specific surface area (463 m2/kg) showed the best activation in cement as well as improving the late mechanical properties of cement. The results show GFS powder with low carbon content has the application value as SCM.

First-principle insights of initial hydration behavior affected by copper impurity in alite phase based on static and molecular dynamics calculations

Copper tailings have been used as a raw material for cement clinker production. The Cu element can enter into the cement phase and change its hydration behavior. In this study, the influence of Cu-doping on the structure and hydration characteristics of alite phase (tricalcium silicate, C3S) are disclosed by combining the density functional theory (DFT)-based static and molecular dynamics calculations. In the static simulation, local Oi atoms move closer to doped Cu atom with Cu–O distance of 1.84–1.93 Å and forms Cu-Oi bonds, resulting the decrease of surface electrophilic reactivity. A single water molecule exhibits lower adsorption energies (0.92–2.12 eV) on the Cu-doped C3S surface than on the pure C3S surface (0.62–1.69 eV), as the chemical bonds of Ca-OW and HW-OS were weakened. Further ab-initial molecular dynamics (AIMD) simulations cover the shortcomings of static calculations and obtain new discoveries: (a) Cu-doping promotes hydroxylation of C3S surface and stabilizes fluctuation of dissociated proton. (b) Ca-OW bond concentration is raised after Cu-doping, whereas the constraint effect of the C3S surface on OW is weakened. (c) Cu-doping accelerates the diffusion of Oi into water layer by ∼2 Å within 13 ps, facilitating the dissolution of clinker. These findings contribute in several ways to our understanding of the hydration properties of Cu-doping C3S and provide theoretical support for the sustainable and greener development of the construction industry.

User Experience in Cosmetics: Perception Analysis Regarding the Use of an Anti-Aging Moisturizer

One of the most important characteristics of aging skin is dehydration, which is why the use of moisturizing products is very important, especially with increasing age. Thus, the user’s experience when using a product is interesting for the companies to develop specific cosmetics not only considering the physiological needs of each skin, but also according to the preference of a group if there is any. For this, a moisturizer was developed, containing an antioxidant active, ascorbyl tetraisopalmitate, whose sensory characteristics were evaluated by 33 Brazilian women between 30 and 60 years old. The results showed that the formulation was well accepted by all subjects, regardless of their age group, initial hydration, or the presence of visible signs of skin aging. It is suggested that the presence of the active ingredient in different concentrations caused a different perception of the formula for specific attributes such as the aqueous residue, film formation, and the feelings of oiliness and stickiness to the skin after application. These results suggest that the perception of the sensory characteristics of the product was more related to the nature and proportion of the compounds than to the age of the subjects.

The role of iron in cement hydration process: From perspective of chemical admixture

The post-peak decelerating hydration progress plays a significant role for concrete technology to assure durability of concrete. The effect of chemical admixture on cement hydration, hydration products, pore structure and moisture diffusion process are conducted by various experiments and the controlling factor on deceleration period of cement hydration and the effect of iron ion on microstructure are revealed. When the chemical admixture is added into cement paste, more ferrite phase is consumed and the iron dissolved in the pore solution modifies the initial hydration product layer and accelerate the hydration process, causing more C-S-H gel generated and denser microstructure. In addition, it is also proved that single diffusion control factor occurs at 80 h for the later deceleration period of cement hydration.