Desalination Using Hydrate

Oak Ridge National Laboratory (ORNL) is working with BC Technologies Ltd in developing a desalinization technique using gas hydrates.  Experiments are conducted in the ORNL Seafloor Processes Simulator

Objective

The goal of this research is to develop an effective method of desalinating coal-bed methane produced water as well as other types of contaminated water. 

Need for Produced Water Treatment

Oil and gas production yields environmentally hazardous water.  The cost of transporting and treating produced water is high.  This cost can be decreased by using hydrate water treating at the wellhead.  This process also eliminates the need for transportation costs.  The treated water can then be used for agricultural and other purposes.

Concept for water treatment using Hydrate

The chemical structure of a gas hydrate includes only water and a given gas molecule (e.g. methane or carbon dioxide). When hydrates form the chemical structure excludes all salts and other impurities.  When the hydrate is dissociated only gas and pure water remain.

Preliminary Research

-          Desalination of water has been performed using hydrate in the laboratory at ORNL

-          These experiments were performed on water with a starting salinity of 35 ppt.

-          Experiments were conducted in a 450 mL pressure vessel.

-          CO2 hydrate was formed from the water and separated from unreacted water.

-          The hydrate was then allowed to dissociate

-          The remaining water has a significantly reduced salinity

Research Plan

-          The next step is to increase the rate at which hydrate can be formed.  We plan to use a previously tested continuous-jet hydrate reactor to for methane hydrate.

-          At the final phase of the project, field demonstration of the reactor will be performed. 

-          The results are expected to be valuable in efforts to economically treat produced water at the wellhead and reuse it for other human activities.

Patent Submission for “ Method for Excluding Salt and Other Soluble Materials from Produced Water” pending approval.