Loading...
The comparative analysis of adsorbents suitable for thermal desalination system
Author(s)
Ntsondwa, Sindisiwe
Date Issued
2022
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
Adsorption desalination is a new type of desalination that uses an adsorption-desorption cycle.
The adsorbent and adsorbate are the two main components of this cycle. The adsorbent is a
substance with both hydrophilic qualities and hydrophobic qualities that adsorb (attracts) and
desorbs (releases) adsorbate that comes into contact with its surface area. When the adsorbent
is exposed to low temperatures, the hydrophilic property is activated, whereas when the
adsorbent is exposed to high temperatures, the hydrophobic property is stimulated. Hydrophilic
happens during the adsorption process and hydrophobic takes place during desorption.
Each process is conducted for a period of time and that time is called the half cycle. By including
the adsorption desalination (AD) cycle, the water vapour uptake rate is increased, resulting in
more desalination water being produced in a shorter amount of time. Silica gel (SiO2), activated
alumina oxide (Al2O3), and molecular sieve zeolite are the three specific adsorbents used. These
adsorbents used are determined by their natural sorption properties, such as porosity and surface
area. These adsorbents were compared to find which one is suitable for the thermal desalination
process.
To examine the performance of adsorbent material, the impact of cycle time, hot, cold and chilled
water temperature, adsorption isotherms, cycle performance (COP) as well as adsorption energy
are also required. Adsorption isotherms speak to the extreme measure of adsorbate adsorbed
per unit mass of dry material at a particular pressure. A weighing apparatus capable of operating
in the range of 5 g–10 kg of sample mass with an accuracy of 0.1 g and a time response less than
0.1 s used to directly monitor the dynamic development of the uptake during the isobaric
adsorption and desorption stage.
The innovative lab work was performed on an AD-heat exchanger made up of granules of silica
gel, zeolite and activated alumina using an aluminium designed heat exchanger. The process
operated at different thermodynamic cycles (Th =70 °C, Teva =10 °C, Tc = 30 and 35 °C), which
are actually for the adsorption/desorption process. The half cycle time was found to be 1200s,
because all three adsorbents were at equilibrium phase even though silica gel adsorbed 12%
water vapour higher than zeolite, and 18% higher than activated alumina. The heat of adsorption
of this process conducted using Origin software and it operates in the range of 12 kJ/mol – 15
kJ/mol.
The adsorbent and adsorbate are the two main components of this cycle. The adsorbent is a
substance with both hydrophilic qualities and hydrophobic qualities that adsorb (attracts) and
desorbs (releases) adsorbate that comes into contact with its surface area. When the adsorbent
is exposed to low temperatures, the hydrophilic property is activated, whereas when the
adsorbent is exposed to high temperatures, the hydrophobic property is stimulated. Hydrophilic
happens during the adsorption process and hydrophobic takes place during desorption.
Each process is conducted for a period of time and that time is called the half cycle. By including
the adsorption desalination (AD) cycle, the water vapour uptake rate is increased, resulting in
more desalination water being produced in a shorter amount of time. Silica gel (SiO2), activated
alumina oxide (Al2O3), and molecular sieve zeolite are the three specific adsorbents used. These
adsorbents used are determined by their natural sorption properties, such as porosity and surface
area. These adsorbents were compared to find which one is suitable for the thermal desalination
process.
To examine the performance of adsorbent material, the impact of cycle time, hot, cold and chilled
water temperature, adsorption isotherms, cycle performance (COP) as well as adsorption energy
are also required. Adsorption isotherms speak to the extreme measure of adsorbate adsorbed
per unit mass of dry material at a particular pressure. A weighing apparatus capable of operating
in the range of 5 g–10 kg of sample mass with an accuracy of 0.1 g and a time response less than
0.1 s used to directly monitor the dynamic development of the uptake during the isobaric
adsorption and desorption stage.
The innovative lab work was performed on an AD-heat exchanger made up of granules of silica
gel, zeolite and activated alumina using an aluminium designed heat exchanger. The process
operated at different thermodynamic cycles (Th =70 °C, Teva =10 °C, Tc = 30 and 35 °C), which
are actually for the adsorption/desorption process. The half cycle time was found to be 1200s,
because all three adsorbents were at equilibrium phase even though silica gel adsorbed 12%
water vapour higher than zeolite, and 18% higher than activated alumina. The heat of adsorption
of this process conducted using Origin software and it operates in the range of 12 kJ/mol – 15
kJ/mol.
Additional information
Thesis (MEng (Chemical Engineering))--Cape Peninsula University of Technology, 2022
File(s)![Thumbnail Image]()
Loading...
Name
Ntsondwa_Sindisiwe_210053046.pdf
Size
3 MB
Format
Adobe PDF
Checksum
(MD5):bd14c85c16caea5c7bdd9ea2e7b616a2