Thermodynamic and kinetic effect of biodegradable polymers on carbondioxide hydrates

Abstract

In this work, the effect of biodegradable polymers, i.e. pectin (PC), sodium-carboxymethyl cellulose (Na-CMC), tapioca starch (TS) and dextran (DX) on thermodynamics and kinetics of CO2 hydrates are evaluated on sapphire hydrate reactor. The CO2 hydrate liquid vapour equilibrium (HLwVE) data is evaluated in the presence of biopolymers (1.5wt%) using isochoric T-cycle method at temperature and pressure ranging from 278.7 to 283.0K and 2.3 to 4.3MPa respectively. The effect of biopolymers on HLwVE curve is reported by measuring average increment temperature (ΔŦ). The constant cooling method is used to evaluate the kinetics of CO2 hydrates at 4.3MPa in the presence of biopolymers (0.12–1.5wt%) at 274.15K and 277.15K. The inhibition effect of biopolymers on the kinetics of CO2 hydrate is reported by measuring induction time, hydrate formation rate and amount of gas consumed. The kinetic inhibition strength of biopolymers is compared with poly-N-vinylpyrrolidone (PVP) and with two non-commercial inhibitors, i.e. glycine and tetra-methyl ammonium chloride (TMACl) through relative inhibition strength (RIS). Results reveal that DX shows maximum increment temperature of 0.36K. While PC and Na-CMC delayed CO2 hydrate nucleation for 423 and 181min respectively. Additionally, biodegradation study on biopolymers indicates that, compared to PVP, biopolymers are easily biodegradable and show potential for gas hydrate offshore applications.