On-site generation of nitrogen gas is a very important step in process safety. The coal mill area is one such location in a cement plant where nitro-generators are in use.
In coal mills, bag filters and fine coal bins, there are chances of fire as coal is in powder form and has a tendency of catching fire due to the presence of volatile matter and spontaneous combustion in presence of air. Therefore, temperatures are continuously monitored in these coal-handling equipment. Due to spontaneous combustion taking place, the temperature rises more, which accelerates the combustion process further. To prevent such combustion and fires, inert gas is flooded in all the equipment and fire-like conditions are prevented.
Earlier, CO2 cylinders were used to supply inert gas to these equipment. CO2 cylinders are scarce and also carry a higher cost. Therefore, since the past 15 years, molecular sieve nitrogen generators are being successfully used in many cement plants to provide inert gas in place of CO2 cylinders. The nitrogen generators have very successfully replaced the CO2 cylinders used in cement plants.
The system being used is made up of a nitrogen generator with high pressure storage tanks. Nitrogen is produced by PSA (Pressure Swing Adsorption) molecular sieve unit. A screw air compressor feeds compressed air to the PSA unit at 10-Bar pressure & it produces 99 per cent purity nitrogen at 8-Bar pressure. This nitrogen is stored in a number of storage tanks. In the event of any high temperature signal coming from a coal mill, bag filter or fine coal bin, this stored nitrogen is dumped into the coal mills, bag filters, or fine coal bins and this displaces air and brings the fire under control.
The stored nitrogen is used in a short time. When nitrogen tanks become empty, by pressure switch on storage tanks, the nitrogen generator restarts producing nitrogen and fills the storage tanks again. This is a fully automatic system requiring no attendant and nitrogen is available round the clock.
To know more about nitrogen generators, you may visit Website – www.mvsengg.com and write to MVS Engineering Limited – New Delhi