Experimental Study Of Desalination Using Carbon Dioxide Hydrate Method

The seawater desalination has a vital significance for solving the shortage of freshwater resources. There are many merits of hydrate desalination such as simple equipments and low energy consumption. It is still at the base study stage in our country. More investment and larger scale experimental study must be executed to lay theoretical foundation for the application of this method.We developed a set of desalination apparatus by hydrate and proposed experimental method and process. The factors which affected the carbon dioxide hydrate formation induction time including the stirring speed and excessive pressure were studied. We found that there was a suitable stirring speed range. The greater the excessive pressure was, the faster the hydrate generated. The phase equilibrium conditions in pure water, salt solutions of different concentrations and seawater were analyzed. We found that the higher pressure was required in pure water than in salt solutions at the same temperature. High salinity needed great pressure. Liquid carbon dioxide as the hydrate former at the stirring speed of 400 revolutions per minute was the best desalination condition which was help to accelerate the hydrate formation and improve the desalination rate. Salinity and the ion concentration changes were determined under this best condition. The removal rate could reach eighty percent at the second desalination process by means of washing the hydrates and brine with distilled water. We calculated the theoretical water production, theoretical desalination efficiency and theoretical desalination rate by the changes of salinity before and after the hydrate formation.We should pay more attention to look for right hydrate agents and hydrate formation accelerators and study the efficient separation between gas hydrate and the brine in the future study, so as to optimize the desalination process, reduce the desalination costs, improve the competitiveness of hydrate desalination and speed up the industrialization process.