9.1 TECHNICAL DATA:
|Type of Absorbent
Size of Molecular Sieve
Heating Inlet Temperature
Heating Outlet Temperature
Cooling Outlet Temperature
Main Air Inlet Temperature
Max. Permissible Carbon dioxide in Atm. Air
Max. Moisture content
Allowable in Atm. Air relative humidity
Heater voltage supply
|Molecular Sieve Type
1.5 mm partite
3 ½ hours
1 ½ hours
Min. 250 Deg.C. To Max. 300 Deg.C.
Min. 150 Deg.C. To Max. 170 Deg.C.
Min. 30 Deg.C. To Max. 50 Deg.C.
Min. 8 Deg.C. to Max. 20 Deg.C.
Min. 35 Kgs./cm2 to Max. 60 Kgs./cm2
50 % to 70 %
At 15 Deg.C.
Each vessel of the Molecular Battery is filled with Molecular Sieve of 1.5
mm. Type 13-X. As the process air passes through Molecular Sieve the
Molecular Sieve will absorb water vapor and CO2 from the air. After some 10
hours, the Molecular Sieve becomes saturated, and it will have to be
If hot air at low pressure is passed through the saturated Molecular Sieve,
the Molecular Sieve will discharge the CO2 and water vapor and is ready for
use again. The absorbing capacity of the Molecular Sieve drops rapidly if
the process air is warm. Therefore, ensure that the compressed air entering
into the Molecular Sieves below 15 Deg.C. And that the Molecular Sieve is
thoroughly cooled after regeneration, before the process air is passed
through it again.
The waste Nitrogen from the Cold Box is passed through an Electrical Heater
and then passed through the vessel to be regenerated. The temperature at the
inlet of the vessel rises rapidly, while the outlet temperature wills rise
very slowly. If the outlet temperature reaches 170 Deg.C. (For about one
hour) the Molecular Sieve is regenerated. This process is known as the
heating cycle, which will take 2 /3 hours. At this stage, if the inlet
temperature exceeds 300 Deg.C. The heater must be put off and put on again
after 10 minutes. When the outlet put off, but the Cold Nitrogen will
continue to pass through the vessel cooling the Molecular Sieve. This
process is known as the cooling cycle which will last about 4 hours. After
cooling, the vessel is ready for use when required for purifying the process
Oil vapor will destroy the Molecular Sieve and therefore ensure that the
carbon filter is in good condition and the process air is as cool as
possible, that maximum oil and moistures condenses out before the air enters
While changing from one vessel to the other, pressurize the vessel very
slowly, by opening the valve A-7 or A-8. It may take half a for the vessel
to pressurize. If the main valves are opened rapidly, the Molecular Sieve
may break up, due to high pressure air propelling the Molecular sieve in the
When charging fresh Molecular sieve, lower the same slowly through a pipe,
so that it does not break on falling at the bottom.
Most of the Plant operating problems are caused by the carry over of CO2
into the Cold Box and its blocking the Heat Exchangers. Satisfactory working
of the Molecular Sieve will avert all these problems. Therefore, maintain
and operate this equipment carefully.
The drier valve seats should be in prefect condition and if the air passes
through valve seat both production of plant and regeneration of driers will
The Heater should immediately be shut down either in case of Plant shut
down or Expansion Engine shut down. Otherwise, water and water vapor will be
drawn from evaporation cooler by the Blower and will flood the Heater and
the drier with water.
9.5 DRIER CHANGE OVER:
When cooling is complete, the regenerated drier is to be lined up, as the
other drier would have become saturated by now. First, the Nitrogen blower
is to be switched off. The Nitrogen valves of regenerated drier are to be
closed. Then the regenerated drier will first be pressurized through
pressurizing valve. The pressuring should not be sudden and hence not
through main air inlet valve. The Molecular Sieve pallets will get
disintegrated soon if pressurizing and depressurizing is sudden.
After pressurizing open air inlet valve completely. Open air outlet valve
gradually, watching the outlet air temperature. This temperature will
initially go up and thereafter will cool down. Then open the outlet valve
completely. Start closing the outlet valve of the drier on line, taking care
of common air outlet temperature. Then close air outlet and inlet valves of
drier, which was on line tightly. Depressurize the drier by depressurizing
valve. The open the Nitrogen valves of the drier to be regenerated. Start
the Nitrogen Blower. Check flow of the gas at the regeneration Nitrogen
vent. The switch on the drier heater for starting heating cycle of drier.
Check for proper performance of drier heater.
9.6 DRIER CHANGEOVER (In Short):
9.7 REPLACEMENT OF MOLECULAR SIEVE: AND TROUBLE SHOOTING
» Molecular Sieve is to be replaced if:
» It becomes powder.
» If it gets contaminated by oil; or
» If it looses its adsorption capacity:
» The above will be known by frequent checking of Cold Box
To change Molecular Sieve, open the top and bottom flanges of drier
vessels. Remove the filter at the bottom. Collect the old Molecular Sieve,
which will fall down. Clean the filters blow the drier vessel.
Fit the bottom filter. Charge about 3 kgs. of Alumina. Then charges
Molecular Sieve Type 13X, size 1.5 mm., size 1.5 mm. about 90 kegs. The
Molecular Sieve should be sieved and be free of all smaller size particles.
It is better to charge through a long funnel so that Molecular Sieve does
not fall with a force and break. Charging is normally done by hand. When
level of Molecular Sieve is just at the brim of dished end of drier vessel,
stop charging. Then fill up the doomed portion with alumina. Fit the top
filter after cleaning.
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