Waste Heat Recovery from Paper Drying

There are various possibilities to recover thermal energy from steam and waste heat in the paper drying process. Some of these include the following:

  • Replacing the dryers with stationary siphons in the paper machine;
  • Mechanical vapor recompression and reuse of the superheated steam in the drying process;
  • Use of heat pumps to recover waste heat;
  • Recovering heat from the ventilation air of the drying section and using this heat for the heating of the facilities when needed.

On the other hand, the options that can be considered for the direct-fired air dryer hoods, used mainly on tissue and toweling machines, include:

  • Recovering the hood exhaust air and using this to preheat the air entering the combustion chamber;
  • Employing a cascade system that uses the hood exhaust air to feed the supply fan of the wet section, which will reduce the fuel demand for wet section burners;
  • installing an economizer to reclaim heat from hood exhaust air and use it to heat fresh water for high pressure showers of the paper machine felt and wires (Kramer <em>et al.</em>, 2009. p.102).
Development Status Products
Commercial

Waste Heat Recovery from Paper DryingCosts & Benefits

Parent Process: Papermaking
Energy Savings Potential

In a mill, replacing the dryers with stationary siphons saved 0.89 GJ/t-paper due to enhanced drying efficiency;
Steam savings from mechanical vapor recompression system amounts 5 GJ/t-paper (~50%), but increases electricity consumption of 160 kWh/t-paper (Kramer et al., 2009. p.102)

CO2 Emission Reduction Potential
Costs

Operation cost savings from replacing dryers with siphons amount $0.045/ton paper (1998 dollars).
Installation cost of paper machine heat recovery system has been estimated to be around $18/ton paper;
By recovering the waste heat from the dryer ventilation and using this for heating the facilities in winter months, a US based mill was able to realize costs savings of $1 000 000 per year. The payback time for the cross-flow heat exchangers installed for this option was 1.5 years (Kramer et al., 2009. p.102).

Waste Heat Recovery from Paper Drying Publications

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