9.2 DESCRIPTION:

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 regenerated.

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.

9.3 REGENERATION:

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 air.

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 the vessel.

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 vessel.

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 be affected.

9.4 IMPORTANT:

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 Equipments.

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.