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Paper Industry-Fan Pumps

There are 3 nos paper machines in the plant. For each paper machine, there is one fan pump each which pumps the pulp at low consistency to the paper machine.

For machine-1 & 2, the fan pump operates through a centricleaner and machine screen before discharging to the paper machine head box. In paper machine-3 there are no centrocleaner system.

A schematic of fan pump system for paper m/c-2 is given below.

Note that the valve after the screen is controlled to about 50% when supplying pulp the head box.

The white water pump operates with a discharge bypass arrangement which is a very old and inefficient concept.

There is scope for energy saving in fan pumps and white water pumps, as discussed below. The measurements on these equipments are given in the following table.

Sr.No. Equipments Motor
Rating KW
Voltage Current Power PF  Speed
28 Fan Pump PM-2 250 409 296 205 0.98 1323
158 Fan pump PM1 250 412 203 142 0.98 985
1335 White water pump-PM2 110 398 132 68.7 0.76 750
  Fan pump PM3 132 389 160 92.3 0.86  

Efficiency estimation of these pumps are given below.

Equipments Power, kW Speed, rpm Head, m Flow, m3/h Efficiency, %
Fan Pump PM-2 205 1323 24 1723 55%
Fan pump PM1 142 985 24 1453 67%
White water pump 68.7 750 10 1565 62%
Fan Pump PM3 92.3   23 970 66%

Pump efficiency is moderate. It varies from 55 to 67%. More improtantly, there is valve control in these systems, which causes teh overall efficiency slide down further. Fan pumps of PM1 & 2 have variable frequency drives installed. Energy can be saved by avoiding throttling by reducing speed.

White water pump has discharge bypass and is also throttled at the inlet to the chest. Replacing this pump with a properly sized pump can save energy.

Energy Saving Potential: Reduce speed of Fan pump1 & 2 and open the valves after the screen

During the energy audit, this has been demonstrated on PM2 fan pump. The frequency was reduced while opening the screen outlet valve. The power reduced from 206 kW to 172 kW.

This is a saving of 34 kW. If this can be implemented on PM1 also, an additional saving of 26 kW can be achieved.

For 350 days/year operation, annual energy saving potential is about 500,000 kWh/year. i.e. 20,000 per year. No investment required, as both machines have VFDs for speed reduction.