A New Generalized Empirical Correlation for Predicting Methane Hydrate Equilibrium Conditions in Pure Water

Abstract

This work contributes to a new generalized empirical correlation for predicting methane (CH 4 ) hydrate equilibrium conditions in pure water. Unlike the conventional thermodynamic approach that involves complex reckoning, the proposed empirical equation is developed by regressing 215 experimental data points from the literature and validating with 45 data points for predicting methane hydrate equilibrium conditions in pure water. The new correlation is proposed for a temperature and pressure range of 273.2−303.48 K and 2.63−72.26 MPa, respectively. The accuracy and performance of the proposed correlation is quantitatively evaluated using statistical error analysis. The proposed correlation was able to estimate CH 4 hydrate equilibrium conditions satisfactorily with an R 2 of 0.99987. The overall error analysis for the proposed correlation shows fair agreement with the experimental data reported within the literature. Concurrently, the new correlation showed better performance in predicting equilibrium conditions compared to those calculated by other empirical correlations available in the literature within the investigated range. In addition, the proposed empirical equation is also checked to evaluate its efficacy in fitting each set of experimental binary/ternary methane hydrates (BTMH) and binary hydrogen hydrates (BHH) for an accurate representation of equilibrium data over a wide range of composition, pressure, and temperature conditions. A maximum percentage deviation of 0.58% and 0.24% was observed between experimental and calculated equilibrium conditions for BTMH and BHH, respectively.

Experimental investigation of methane hydrate formation in the presence of metallic packing

“…Natural gas which is > 95 percent methane (CH4), has been touted as an excellent alternative to coal and oil as a fuel for power generations and transportation due to its low carbon emission characteristics such as releasing considerably lesser degree of pollutants upon combustion per energy basis [7,8]. Despite CH4 being acknowledged as a potential energy source [9], the major challenge is in its handling, and achieving high storage capacities both economically and safely. The commercially available methods like liquified natural gas (LNG) and compressed natural gas (CNG), which are capable of achieving predominant volumetric capacities (≈ 600 v/v for LNG, ≈ 240 v/v for CNG) and energy densities (22.2 MJ/l for LNG and 9 MJ/l for CNG [10]) greatly suffer from their expensive cryogenic (113 K) and high-pressure (25 MPa) storage approaches that prevent their widespread use [11][12][13][14][15].…”

“…Aside from new reactor designs, continuous research efforts have been communicated [9,[58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75] in enhancing the kinetics of CH4 hydrate formation by the use of thermodynamic promoters or kinetic promoters (predominantly surfactants), where these surfactants reduce the interfacial tension between (guest) gas-liquid (host) interface and enhance the hydrate growth (mass transfer of gas and liquid phase) without affecting the thermodynamics [67,68]. Nevertheless, fast hydrate formation is always associated with high hydration heat which ultimately weakens the acceleration effect of surfactants on hydrate formation [77,78].…”

“…On the other hand, the thermodynamic promoters which can alter the hydrate forming conditions, predominantly occupy the larger cages of the hydrate and eventually lower the CH4 storage capacity compared to pure CH4 hydrates, consequently a penalty on storage capacity is ineludible [71]. A comprehensive list of both kinetic and thermodynamic promoters for CH4 hydrates is presented in our earlier publication [9].…”

“…All the experiments were conducted by filling the reactor with 2.05 g H2O and the experiments were carried out at an initial pressure of 6 MPa, and temperatures 273.65 K, 275.65 K, 277.65 K. As it is known that a larger driving force can favor (shorten) the hydrate formation induction time[36,186] at a given temperature or pressure, this work sets the experimental pressure (Pexp) at 6 MPa. The CH4 hydrate formation phase equilibrium curve from CSMHYD[187] and Kummamuru et al[9] reports hydrate equilibrium pressure (Peq) approximately at 2.7 MPa, 3.3 MPa, 4 MPa at 273.65 K, 275.65 K, and 277.65 K respectively. Therefore, the driving force (ΔP = Pexp -Peq; K in 5 mm and 2 mm SSB packed bed systems.…”

Twin Support Vector Regression for Prediction of Natural Gas Hydrate Formation Conditions

“…These correlations are widely used by engineers in oil and natural gas companies. There are two widely used correlations for rapidly estimating the hydrate phase equilibrium conditions, both are attributed to Katz and co-workers, that is, the gas gravity method and K -factor method. , Many hydrate formation prediction correlations based on the gas gravity method could be found in literature, such as Hammerschmidt, Makogon, Kummamuru, Motiee, Towler and Mokhatab, Bahadori and Vuthaluru, Amin, and Ghayyem . However, the gravity method just work only in a particular range of gas gravity, pressure, and temperature.…”