Gas Hydrate Formation In Presence Research Articles

Thermodynamic modeling of methane hydrate formation in the presence of imidazolium-based ionic liquids using two-step hydrate formation theory and CPA EoS

In this study, thermodynamic modeling is performed to predict the P-T equilibrium conditions of methane gas hydrate formation in presence of ionic liquids. The imidazolium-based ionic liquids including [EMIM][HSO4], [EMIM][EtSO4], [BMIM][BF4], [OH-EMIM][BF4], [BMIM][Cl] and [BMIM][Br] are modeled through two-step hydrate formation theory of Chen and Guo coupled with CPA EoS for calculating the fugacities of species in liquid and gas phase. The CPA pure component parameters for ionic liquids and also the majority of binary interaction parameters are adjusted using the liquid density and binary VLE data, respectively. The thermodynamic modeling is carried out in the presence of 0.1 weight fractions of all the studied imidazolium based ionic liquids. Moreover, the effect of three various concentrations of [BMIM][BF4] on the P-T equilibrium diagram of methane hydrate are predicted at 0.1, 0.15 and 0.20 weight fractions of this ionic liquid. The results indicate that the CPA EoS can satisfactorily model the phase behavior of aqueous solutions of imidazolium based ionic liquids considering 2B scheme for the association term. In addition, the results indicate good predictions of the proposed model for methane hydrate equilibrium conditions in the presence of imidazolium-based studied ionic liquids including concentration changes such that the absolute average deviations of methane hydrate formation pressures is obtained below 4.2%.

Semicompletion time of carbon dioxide uptake in the process of gas hydrate formation in presence and absence of SDS and silver nanoparticles

ABSTRACTCarbon dioxide emission to the atmosphere is one of the main causes of the current global warming. Therefore, capturing this greenhouse gas is very important. The effect of sodium dodecyl sulfate (SDS) and silver nanoparticles on semicompletion time (t95%) of carbon dioxide uptake in the process of gas hydrate formation is investigated in this communication. The tests were performed at temperatures of 273.65 and 275.65 K and initial pressures of 2 and 3 MPa in a 460 cm3 stirred batch reactor. Experimental measurements show that utilization of SDS and silver nanoparticles decreases the semicompletion time of carbon dioxide uptake considerably. The addition of SDS with concentration of 500 ppm and silver nanoparticles with concentration of 45 μM at p = 2 MPa and T = 275.65 K, respectively, decreases the semicompletion time of carbon dioxide uptake 136.09% and 152.88%, compared to pure water. Investigating the effect of temperature on the amount of t95% in the presence and absence of tested additives shows that this kinetic parameter decreases by increasing the temperature from 273.65 to 275.65 K.

Thermodynamic modeling of gas hydrate formation in presence of thermodynamic inhibitors with a new association equation of state

Formation of hydrate crystal particles has been one of the major difficulties facing gas industry in the generation, transmission, and processing that causes blockage of pipelines and equipment resulting in decreases of level of safety and immunity Which necessitating proper methods to prevent hydrate formation. One of the most common treatments are injection of chemical inhibitors. Keeping excessive cost of hydrate remediation and inhibition in mind, using a reliable predictive model is the key step of designing a natural gas transmission operation.In this paper the van der Waals and Platteeuw (vdW-P) model was coupled with Dehaghani et al.'s association equation of state (DA-EOS) for prediction of equilibrium temperature of methane hydrate in presence of methanol (MeOH), ethanol (EtOH), and mono-ethylene glycol (MEG) as thermodynamic inhibitors. To increase the calculation accuracy, the mole fraction of components in the liquid and gas phases were obtained using the results of flash algorithm calculations. In addition, effect of gas dissolution in aqueous phase was considered by Henry's law and water activity coefficient calculation was performed based on φ- φ approach. Additionally, the binary components interaction coefficients in the system, was considered as a linear function of temperature.To evaluate the capability of DA-EOS, the prediction of methane hydrate phase behavior in presence and absence of inhibitors was compared with the experimental data and also the prediction of Peng-Robinson EOS (PR-EOS). In addition, a comparison was made between DA-EOS and Elliott–Suresh–Donohue uation of State (ESD-EOS) to gain insight of performance of present model. The prediction of DA-EOS and ESD-EOS was close to each other. DA-EOS proved to be effective in representing self-association between water and cross-association between water-inhibitor components in the case of hydrate solution. Also, it was concluded that performance of vdW-P model strongly depends on reliability of EOS used for calculation of fugacity coefficient.

Experimental study and thermodynamic modeling of CO2 gas hydrate formation in presence of zinc oxide nanoparticles

The effect of synthesized zinc oxide (ZnO) nanoparticles was investigated on the kinetic and thermodynamic equilibrium conditions of CO2 hydrate formation. The amount of the gas consumption was measured and compared for the four sample fluids: pure water, aqueous solution of sodium dodecyl sulfate (SDS), water-based ZnO-nanofluid and water-based ZnO-nanofluid in the presence of SDS (0.001 mass fraction). The time of hydrate growth decreased and the amount of the storage gas enhanced in the presence of nanoparticles. Moreover, the nanoparticles size effect besides the CO2 solubility enhancement in ZnO-nanofluid led to the reduction of water activity, so that the equilibrium curve of hydrate formation was shifted to higher pressures. A new correlation for Henry’s law constant was obtained using CO2-solubility data in ZnO-nanofluid. Finally using this correlation, the water activity was calculated through the Chen–Guo approach to propose a thermodynamic method for prediction of the equilibrium hydrate formation conditions in the presence of the nanoparticles.

Experimental investigation of induction time for double gas hydrate formation in the simultaneous presence of the PVP and l-Tyrosine as kinetic inhibitors in a mini flow loop apparatus

The main objective of the present work is experimental investigation of induction time for double gas hydrate formation in the presence or absence of kinetic inhibitors in a mini flow loop apparatus. For this purpose, a laboratory mini flow loop apparatus is designed and built up to measure the induction time for binary mixtures during gas hydrate formation when a gaseous mixture (such as 70% C1–30% C3, 30% C1–70% C3, 70% C1–30% i-C4 and 30% C1–70% i-C4) is contacted with water in the absence or presence of dissolved inhibitor, such as poly vinylpyrrolidone (PVP) and l-tyrosine under suitable temperature and pressure conditions. In each experiment, water blend saturated with gas mixture is circulated up to a required pressure. Pressure is maintained at a constant value during experimental runs by means of the required gas mixture make-up. In this work, induction time is investigated for of double gas hydrate formation in vitro in the presence of the PVP and l-Tyrosine alone and their simultaneous presence as kinetic inhibitors in a mini flow loop apparatus at various concentrations. The results show that the simultaneous addition of PVP and l-tyrosine increases the induction time of gas hydrate formation several times more than that without using the inhibitor. Indeed, the addition of the small value of l-tyrosine to PVP, the induction time being longer than when PVP is as a kinetic inhibitor only, because the l-tyrosine is stronger than the PVP as an inhibitor.

Enhancement of the performance of modified starch as a kinetic hydrate inhibitor in the presence of polyoxides for simple gas hydrate formation in a flow mini-loop apparatus

The main objective of the present work is the enhancement of the performance of modified starch as a kinetic inhibitor in the presence of polyoxides such as ethylene oxide (PEO) and polypropylene oxide (PPO) for simple gas hydrate formation in a flow mini-loop apparatus. Polyoxides such as PEO and PPO are high molecular weight polymers that are not kinetic inhibitors by themselves. For this investigation, a laboratory flow mini-loop apparatus was set up to measure the induction time and rate of gas hydrate formation when a hydrate forming substance (such as C1, C3, CO2 and i-C4) is contacted with water containing dissolved inhibitor in the presence or absence of polyoxides under suitable temperature and pressure conditions. In each experiment, water containing inhibitor blend saturated with pure gas is circulated up to a required pressure. Pressure is maintained at a constant value during experimental runs by means of required gas make-up. The effect of PEO and PPO on induction time and gas consumption during hydrate formation is investigated in the presence or absence of modified starch as a kinetic inhibitor. The results showed that the induction time is prolonged in the presence of PPO compared to the inhibitor alone. The efficiency of PPO is higher than the PEO, because, the induction time for simple gas hydrate formation in presence of PPO is greater than by using the PEO in presence of kinetic hydrate inhibitors.Also, the results show, that the gas consumption in the presence of modified starch is lower that in the absence of this inhibitor for all experiments. Moreover, the inhibition effect is clearly seen as well as the synergism between the inhibitor and PEO or PPO and this effect is higher in the presence of PPO.

Experimental Investigation of Natural Gas Components During Gas Hydrate Formation in Presence or Absence of the L-Tyrosine as a Kinetic Inhibitor in a Flow Mini-loop Apparatus

Hydrates are crystalline compounds similar to ice, with guest molecules like methane and ethane trapped inside cavities or cages formed by the hydrogen bounded framework of water molecules. These solid compounds give rise to problems in the natural gas oil industry because they can plug pipelines and process equipments. Low dosage hydrate inhibitors are a recently developed hydrate control technology, which can be more cost-effective than traditional practices such as methanol and glycols. The main objective of the present work is to experimentally investigate simple gas hydrate formation with or without the presence of kinetic inhibitors in a flow mini-loop apparatus. For this purpose, a laboratory flow mini-loop apparatus was set up to measure the induction time and gas consumption rate during gas hydrate formation when a hydrate forming substance such as methane, ethane, propane, carbon dioxide and iso- butane is contacted with water in the absence or presence of dissolved inhibitor at various concentration under suitable temperature and pressure conditions. In each experiment, a water blend saturated with pure gas is circulated up to a required pressure. Pressure is maintained at a constant value during experimental runs by means of the required gas make-up. The effect of pressure on gas consumption during hydrate formation is investigated with or without the presence of PVP (polyvinylpyrrolidone) and L-tyrosine as kinetic inhibitors at various concentrations. The experimental results show that increasing the pressure of the system, causes to increase the experimental gas consumption and decrease the induction time. Also, the extent of gas hydrate formation at a given time is clearly less in the presence of the inhibitors. Moreover, when comparing the gas consumption during the hydrate formation for simple gas hydrate formation in presence of PVP and L-tyrosine inhibitors, it is seen that the gas consumption in presence of L-tyrosine is lower than that of PVP for all experiments.

Intensification of the performance of kinetic inhibitors in the presence of polyethylene oxide and polypropylene oxide for simple gas hydrate formation in a flow mini-loop apparatus

The main objective of the present work is enhancement of the performance of gas hydrate kinetic inhibitors in the presence of polyethylene oxide (PEO) and polypropylene oxide (PPO) for simple gas hydrate formation in a flow mini-loop apparatus. PEO and PPO are high molecular weight polymers that are not kinetic inhibitors by their self. For this investigation, a laboratory flow mini-loop apparatus was set up to measure the induction time and rate of gas hydrate formation when a hydrate-forming substance (such as C1, C3, CO 2 and i-C4) is contacted with water containing dissolved inhibitor in presence or absence of PEO or PPO under suitable temperature and pressure conditions. In each experiment, water containing inhibitors blend saturated with pure gas is circulated up to a required pressure. Pressure is maintained at a constant value during experimental runs by means of required gas make-up. The effect of PEO and PPO on induction time and gas consumption during hydrate formation is investigated in the presence or absence of PVP (polyvinylpyrrolidone) and l-tyrosine as kinetic inhibitors. Results were shown that the induction time is prolonged in the presence of PEO or PPO compared to the inhibitor only. Inclusion of PPO into a kinetic hydrate inhibitor solution shows a higher enhancement in its inhibiting performance compare to PEO. Thus, the induction time for simple gas hydrate formation in presence of kinetic hydrate inhibitor with PPO is higher, compare to kinetic hydrate inhibitor with PEO.