Parameters affecting the solubility of carbon dioxide in seawater at the conditions encountered in MSF desalination plants

The solubility of carbon dioxide in different mixtures of aqueous solutions (normal water and different composition of saline water) has been determined at temperature of 25–90°C and pressure of 1–2 bar by using an experimental rig which has been designed to ensure proper contact between the CO2 gas and different mixtures of aqueous solutions. The continuous analysis of the outlet vapour for CO2 content was done by the CM-5011 Carbon Coulometer and the amount of CO2 absorbed into the solution was calculated, this was followed by calculating Henry’s law constant. The objective of this work is to present an experimental data that would show the effect of temperature, salinity and pressure on CO2 solubility in aqueous solutions.

In this work CO2 gas solubility in different aqueous solutions was measured using an equilibrium apparatus connected to CM-5011 Carbon Coulometer to analyze the outlet vapour continuously until equilibrium or gas saturation was reached. Then, the obtained data from the Carbon Coulometer was downloaded to an excel sheet where a CO2 gas mass balance was carried out and CO2 solubility was then calculated. The CM-5011 Carbon Coulometer has been utilized to monitor CO2 concentration in the outlet vapour continuously. From the data obtained it was shown that as the system temperature increased the CO2 gas solubility in different aqueous solutions tested decreased. The reduction in the CO2 gas solubility was noticed at temperature between 25 and 60°C but this phenomenon was less evident at 80 and 90°C. When measuring the solubility of CO2 in different aqueous solution it was found that the presence of different salts in the solutions would reduce the CO2 gas solubility in the solutions. This trend was very evident at 1 bar and temperatures between 25 and 60°C but this effect was less noticeable at higher temperatures 80–90°C. However, at system pressure of 2 bar it was noticed that the presence of different salts in the solutions would reduce the CO2 gas solubility in the aqueous solutions at the different temperatures 25–90°C. Also, from the experimental results obtained it was found that CO2 gas solubility decreased as the concentration of the salts dissolved in the aqueous solutions increased. The effect of system pressure on the CO2 gas solubility was studied and it was shown that the CO2 gas solubility increased when the system pressure increased from 1 to 2 bar.