ADSORPTION SECTION (1)(1)

ADSORPTION SECTION (1): 

ADSORPTION SECTION (1)

What is ADSORPTION: 

What is ADSORPTION Mass transfer operation involves contact between fluid (Adsorbate) and solid (Adsorbent) to remove certain constituent from fluid phase.

Slide 3: 

We deal with adsorption examples in our life:

Adsorption Mechanism: 

Adsorption Mechanism Adsorption takes place due to presence of unequal force for the surface molecules. If the attraction force between surface molecules and gas is greater than the attraction force between gas molecules themselves, ADSORPTION takes place.

Applications: 

Applications

Comparison between physical and chemical adsorption: 

Comparison between physical and chemical adsorption Physical Adsorption Chemical Adsorption Molecules are adsorbed on available sites. Adsorbates are molecules. Multiple layers. Attraction is a result of Vander Waal’s force. Forces are weak but act on long distance. Reversible Rate is not affected by increasing temperature. Molecules are adsorbed on active sites only. Adsorbates are atoms or radicals. Single layer. Attraction is a result of bonds. Forces are strong but act on short distance. Irreversible. Rate is affected by increasing temperature.

Slide 7: 

Force Distance Physical Chemical

Adsorbent Prosperities: 

Adsorbent Prosperities High Selectivity. High surface area. Thermally & chemically stable. Ease of regeneration. High capacity(mg Adsorbate/gm Adsorbent). Hardness & mechanical strength.

Slide 9: 

q C* or P* T1 T2 T3 T4 T4>T3>T2>T1 q4<q3<q2<q1 Desorption favours high temperature

Adsorption Techniques in Industry: 

Adsorption Techniques in Industry

Case Study 1:Moving Bed Adsorber: 

Case Study 1:Moving Bed Adsorber In Coal Power Plants, fuel is burned to produce heat and electricity. As a result, CO2 is released with fly ashes. The aim of our study is to reduce CO2 emissions through the end of pipe of coal power plants. It can be done by adsorption/ desorption by hot substance. This process is called Temperature Swing Adsorption (TSA)

Case Study 1:Moving Bed Adsorber: 

Firstly, adsorbent beads (blue) are transferred to the adsorption section by bucket elevator. Before entering the adsorption section, adsorbent is screened to separate the beads fines (white) which resulted from regeneration step. The whole beads fall into a series of perforated trays which are designed to retard beads in adsorption section to have sufficient time of contact. Case Study 1:Moving Bed Adsorber

Case Study 1:Moving Bed Adsorber: 

In adsorption section, flue gases that consist of : Adsorbable materials(CO2)....(red) Non- adsorbable materials (N2)...(yellow) Flue gas enters the adsorption section through the perforated distributor pipe at the bottom of that section. Case Study 1:Moving Bed Adsorber

Case Study 1:Moving Bed Adsorber: 

Now the beads are saturated with CO2 and we need to regenerate it. As mentioned before, desorption favours high temperature so, beads must be heated to regenerate them. Case Study 1:Moving Bed Adsorber

Case Study 1:Moving Bed Adsorber: 

Beads are preheated in heat recovery section against a certain fluid that can resist the high temperature. In heat recovery section, beads need to be cooled to start a new adsorption cycle which is achieved against the fluid mentioned above. Case Study 1:Moving Bed Adsorber

Case Study 1:Moving Bed Adsorber: 

After that, beads are heated to higher temperature against the feed flue gases in plate heat exchanger. Now feed flue gases enter the adsorption section with low temperature that favours the adsorption step. CO2 rich gas is collected and sent to sequestration. Case Study 1:Moving Bed Adsorber

Fixed Bed Adsorber: 

Z ads Z ads Z ads Z ads Fixed Bed Adsorber

Fixed Bed Adsorber: 

C t C0 (0.01:0.05)C0 t b (0.95)C0 t ex Fixed Bed Adsorber

Case Study 2:Fixed Bed Adsorber: 

Hydrogen is produced by many ways but the most common process is Steam Reforming. Case Study 2:Fixed Bed Adsorber

Case Study 2:Fixed Bed Adsorber: 

The hydrogen product is not pure as it contains CO,CO2,H2O,CH4...etc It is purified either by: Absorption against Benfield solvent. Pressure Swing Adsorption (PSA) Case Study 2:Fixed Bed Adsorber

Case Study 3:Fluidized Bed Adsorber: 

Case Study 3:Fluidized Bed Adsorber