Membrane distillation (MD) is a technology that is emerging as a viable
alternative to traditional desalination techniques such as Reverse Osmosis, Multistage flash distillation, Multiple-effect distillation, Vapour-compression evaporation,
etc. The advantages of MD over conventional desalination technologies include
higher ionic rejection capacity, greater feasibility for high saline brine treatments,
ability to operate using low-grade heat energy, a single-stage process and remote
operation using renewable energy, among others.
In this dissertation, a parametric study was performed using experiments to
assess the feasibility of using direct contact membrane distillation (DCMD)
technology to desalinate saline water of different concentrations. The results showed
that the permeate flux increased to 37.1 L/m².h from 11.6 L/m².h when the
temperature was raised from 45 °C to 75 °C. Additionally, the permeate flux
decreased to 13.6 L/m2
.h from 27.3 L/m2
.h, and the reduction in flux was around
50% when the concentration of sodium chloride in the feed solution was increased
from 0% to 26%.
The experimental results obtained using oilfield-produced water were highly
encouraging. The permeate flux was 11.5 L/m².h and 12.5 L/m².h at 80 °C and 85
°C, respectively. The results indicate the enormous potential of DCMD to treat
hypersaline oilfield-produced water, with an overall rejection of salts above 99%. The
base-line technology is the DCMD technology.
This study also evaluated the viability of air-gap membrane distillation
(AGMD) and vacuum membrane distillation (VMD) for treating different types of
saline water (3.5%, 7%, 15% and 26% NaCl solutions), including Arabian Gulf
Seawater (AGS) and oilfield-produced water. AGMD experiments at different feed
temperatures found that increasing the test temperature from 70 °C to 85 °C
increased the permeate flux by 56.64%. In contrast, the VMD experiments showed
that increasing the feed temperature from 65 °C to 85 °C resulted in a 26.87%
increase in permeate flux. The results obtained from the experiments showed that
VMD performed better at higher feed concentrations, while AGMD was superior at
lower feed concentrations. The flow-rate experimental results showed that increasing
the flow rate from 1.3 to 2.0 litres per minute resulted in a 1.2-fold increase in
permeate flux for both configurations, with salt rejection close to 99.9% and unaffected by the feed flow rate. AGMD outperformed VMD at all flow rates, and the
increase in permeate flux with flow rate was similar for both configurations.
This study found lower gaps, i.e. air gap and vacuum space, were preferred in
AGMD and VMD configurations, respectively, as they showed good flux, potentially
due to the reduced effects of heat and mass-transfer mechanisms at smaller gaps.
The experimental results showed that AGMD and VMD processes were highly
efficient in treating oilfield-produced water and AGS, achieving high salt rejections as
high as 99.97%. The results showed that the tested membranes achieved salt
rejections as high as 99.97%, and the order of fluxes observed in the VMD
configuration was Polyvinylidene fluoride (PVDF) > Polypropylene (PP) >
Polytetrafluoroethylene (PTFE). In the AGMD configuration, the order of fluxes
observed was Polypropylene (PP) > Polyvinylidene fluoride (PVDF) >
Polytetrafluoroethylene (PTFE).
This study’s results will provide valuable insights into the potential applications
of AGMD and VMD processes in desalination, especially in regions where freshwater
resources are scarce or contaminated. The information gained from this study can
be used to optimise the performance of these processes, improve their costeffectiveness and energy efficiency, and enhance their viability as potential solutions
for addressing water scarcity and pollution issues. The study discussed in this
dissertation is the first to present laboratory-scale results of using AGMD and VMD
technologies to treat AGS and oilfield-produced water in Kuwait while considering
prevailing conditions. The findings of this study lay the groundwork for conducting
pilot-scale studies on Arabian Gulf Seawater and oilfield-produced water utilising
DCMD, AGMD and VMD technologies, not only in the Middle East region but
globally.
| Date of Award | 18 Nov 2024 |
|---|
| Original language | English |
|---|
| Awarding Institution | - University Of Strathclyde
|
|---|
| Sponsors | Kuwait Cultural Office / EMBASSY OF THE STATE OF KUWAIT |
|---|
| Supervisor | Edmondo Minisci (Supervisor) & Marcello Lappa (Supervisor) |
|---|