Interfacial Characterisation of Gas-Liquid Interfaces Related to Gas Flotation in Offshore Produced Water Treatment - Dynamic Adsorption of Heteroatoms

摘要

Produced water is the largest waste stream produced in the recovery of oil and gas. The processing of produced water occurs in several stages including gas flotation. Gas flotation is separation by gravity and the effectiveness of gas flotation is dependant on the size of the gas bubble, the distribution of bubbles and the degree of dispersion. The concentration of oil and the chemical content of the produced water play a role, a long with the pH, viscosity and the interfacial properties between the oil, gas and brine. Interfacial tension, wettability and spreading coefficient is interfacial properties that are important for the effectiveness of gas flotation.The aim of this thesis is to see how dynamic adsorption of heteroatoms affects the interfacial tension and properties of solutions with different concentrations and at different pH values. The chemicals used in this thesis are Pyridine, Phenol and 3-cyclopentyl propionic acid. The interfacial tension measurements were done on a Maximum Bubble Pressure Tensiometer, which measures the interfacial tension at short time scales. Throughout this thesis three chemicals with different properties, concentrations and various pH have been used. Each chemical shows different behaviour in both MQ-water and synthetic brine. Pyridine shows similar behaviour for all the six concentrations at pH 2 in both MQ-water and synthetic brine compared to the other pH values. For pH 7 and pH 10 the influence of concentration is more sever. The influence of pH at the higher pH values is almost non-existing for Pyridine in MQ-water. For Phenol in MQ-water an increase in concentration will lead to a decrease in surface tension. The influence of pH on Phenol indicates that at lower pH values Phenol is more soluble. For Phenol in synthetic brine the changes in pH has no affect on the surface tension. When comparing the result for Phenol in synthetic brine and MQ-water it is clear that the solubility of Phenol decreases in synthetic brine, leading to more sever decrease in surface tension in MQ-water than in synthetic brine. For 3-cyclopentyl propionic acid the influence of concentration on surface tension is clear. The decrease in surface tension before equilibrium values are reached is larger for this acid, due to the size of the molecule. The surface tension for this acid seems to be dependent on pH at low and at high concentrations.