Supercritical fluid dyeing

1. Welcome
To
Our Presentation
On
Supercritical Fluid Dyeing

2. Submitted To:-
Aminul Islam Mishuk
Assistant Professor
Department Of Textile Engineering(BUBT)
Submitted By:-
Name ID Intake
S.M.Saiful Islam 16173207082 19th
Md.Ibrahim Khalil 16173207095 19th
Foysal Ahmed 16173207097 19th
Md.Sariful Islam 16173207145 19th
Md.Roni Hossain 16173207031 19th

3. Supercritical fluid is one kind of fluid which is highly
compressed gases which combine properties of gases and
liquids in an intriguing manner. It is a substance which can
be either liquid or gas, used in a state above the critical
temperature and critical pressure where gases and liquids
can coexist. It shows unique properties that are different
from those of either gases or liquids under standard
conditions. A supercritical fluid has both the gaseous
property of being able to penetrate anything, and the liquid
property of being able to dissolve materials into their
components.

4. Picture of SCF Processing Machine

5. Dyeing Process
1.Pretreatment:In the first step the textiles are cleaned from pollutions
and sticking auxiliary materials from the production because the
rests of wax, oils and other hydrophobic substances can disturb the
dyeing process. With the pressurization pump liquid CO2 from the
buffer tank is compressed to supercritical pressure and heated up in
the heat exchanger to supercritical temperature. The supercritical
CO2 flows through the textiles in the dyeing autoclave and, besides,
solves carefully all sticking pollutions from the fibers. The loaded
CO2 flows via a expansion valve and becomes by the pressure
decrease gaseous. Thereby the solution power is reduced and the
extracted pollutions precipitate and are collected in the separator .
Afterwards the cleaned CO2 is liquefied in the condenser and is led
via the buffer vessel back into the circulation.

6. Dyeing Process
2.Dyeing:After the pre-treatment the actual dyeing process
begins by switching of the dyestuff receiver into the
CO2circulation. The supercritical CO2 solves the dyestuff in
the dyestuff receiver and flows through the dyeing autoclave .
The CO2 loaded with dyestuff is delivered through the textiles
and the dyestuff is adsorbed in the fibers. After the dyeing
autoclave the CO2 flows through a filter to the circulating
pump and afterwards is fortified in the dyestuff receiver with
fresh dyestuff and is led as long as in the circulation, until the
desired dyeing intensity of the textiles is achieved.

7. Dyeing Process
3.After treatment:After finishing the dyeing step the CO2 circuit
and dyed Material are cleaned from excess dyestuff. Therefore
the dyestuff receiver is taken out of the CO2 circuit and the
loaded CO2 is expanded via the expansion valve into the
separator. The excess dyestuff precipitates fall out and is
collected in the separator. The CO2 is circulated as long as the
plant and the textiles is cleaned from the excess dyestuff
leftovers.
After finishing the complete dyeing process the CO2 circulation
is stopped and the dyeing autoclave is depressurized to
atmospheric conditions. The dyed textiles are taken out of the
autoclave.

9. Diagram of SCF

10. Supercritical fluids are highly compressed gases that
have properties of both a liquid,gas & this offers
advantage of textile processing.Supercritical CO2
may act as both a solvent & a solute.supercritical
fluids have higher diffusion coefficent & lower
viscosities than liquids,as well as the absence of
surface tention,allowing better penetration into
materials.

11. Difference between conventional
& supercritical CO2 dyeing
Conventional Dyeing Supercritical CO2 Dyeing
High volume of waste water with
the residual dye chemical etc.
No waste water at all.Dye
remains as powder.No need for
dispersing,levelling agent.
High energy requirements. Only 20% energy requirements.
Dyeing/washing,drying times is
3-4hrs per batch.
Only 2 hours.

12. Characteristics of SCF
1. No surface tension in a supercritical fluid.
2. No liquid/gas phase boundary.
3. Soluble in material in the fluid.
4. Density increases with pressure, solubility
tends to increase with pressure.
5. By changing the pressure & temperature of the
fluid, can be tuned to be more liquid or more
gas.

13. Advantage of SCF
1. Elimination of usage of water, water
treatment & water pollution.
2. Elimination of a drying step,thus reduce
energy cost.
3. No after treatment is required.
4. Time required for dyeing is very less.
5. Gives good rubbing fastness.
6. Dyeing occurs with high degree of levelness
7. No air pollution due to recycling of CO2 is
accomplished.

14. Disadvantage/Limitations of SCF
1. Initial investment is high.
2. High pressure & high temperature are required
for dye solubility during the process.
3. It is a batch process, so processing of long
length fabric is not possible.
4. There is little data available about dye stuff
solubility in SCCO2.
5. At present, SCCO2 dyeing is confined to
synthetic fibers.