Title page for ETD etd-07122012-172310


Type of Document Master's Thesis
Author Niu, Jing
Author's Email Address niujingw@vt.edu
URN etd-07122012-172310
Title Desalination of Produced Water via Gas Hydrate Formation and Post Treatment
Degree Master of Engineering
Department Mining and Minerals Engineering
Advisory Committee
Advisor Name Title
Yoon, Roe-Hoan Committee Chair
Adel, Gregory T. Committee Member
Gandour, Richard D. Committee Member
Luttrell, Gerald H. Committee Member
Keywords
  • Desalination
  • gas hydrate
Date of Defense 2012-04-19
Availability unrestricted
Abstract
This study presents a two-step desalination process, in which produced water is cleaned by forming gas hydrate in it and subsequently dewatering the hydrate to remove the residual produced water trapped in between the hydrate crystals. All experiments were performed with pressure in the range of 450 to 800psi and temperature in the range of -1 to 1°C using CO2 as guest molecule for the hydrate crystals. The experiments were conducted using artificial produced waters containing different amounts of NaCl, CaCl2 and MgCl2 at varying temperature (T) and pressure (P). The results are presented as functions of %Reduction of difference chemical elements, CO2 requirements and applied T and P conditions.

The impact of dewatering techniques, including centrifuge and filtration process, on gas hydrate solid product is studied. The results showed that over 99% of dissolved NaCl and MgCl2 can be removed from artificial saline water in laboratory experiments. This was achieved in a process involving a single-stage hydrate formation step, followed by a single-step solid-liquid separation (or dewatering). The results also show that the %Reduction (percentage of the concentration decrease) of artificial produced water increases with centrifugation time and rotational speed (rpm). The %Reduction was increased considerably after hydrate crystals were crushed and filtered, indicating that the artificial process water was entrapped in between the hydrate crystals. It was found also that the finer the particle size, the higher the extent of salt removal. In general, filtration was a better than centrifugation for the removal of TDS (Total Dissolved Solids).

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