Carbon diokside emissions reduced by 56.000 tn/year

1. Summary

Total energy savings achieved by vacuum system improvements at paper machines
has reached the level of 10 MW, which equals the carbon diokside emission of
about 56.000 tn/year.

2.  Screening results ( desk top study)

A desktop study of PM vacuum system eficiency has been done for about 90 paper
machines.Conclusion has been, that efficiency losses take place at 70 % of them.

Estimated total energy savings potential is over 30 MW ( see also picture 1).

In a typical case energy savings can be achieved with relatively small modifications, by improving the automation and pump connections ( = without installation of expensive  new equipment, new pumps, fans or blowers).


Picture 1: Cumulative energy savings at PM vacuum systems

3. Pre-Engineering

Pre engineering has been carried out for 30 paper mills, and the total verified
energy saving potential is about 15 MW. 

Pre engineering includes typically process synthesis ( = red pen version of the
vacuum system PI diagram), reliable estimates for energy saving and pay-out 
time of the required improvement.

4. System improvements and achieved results

Total energy savings at the end of 2012 are about 10 MW, which equals to about
56.000 ton CO2 emissions per year.

Biggest savings have been nearly 900 kW, and in average savings have been at 
the level of 400 .. 500 kW per machine. Pay-out time of improvements have often
been less than one year.

In some cases the required vacuum system modifications have been so small, 
that mills have done the improvements inmediatelly. More typically improvements 
and modifications of automation and piping are needed, and they have been 
done during a two day shut down. 

5. When to react

It seems to us, that vacuum system should always be cheked, when a rebuild
of PM is done. "Stand alone" vacuum system improvements  can also be very 
profitable, and not necessarily very expensive.

Improvement of the existing system should always be checked first ( = before 
installation of expensive new equipment ).
    
                                                                                                                        Kari U
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