Heat recovery in paper mill with immersion TCOIL

We recently came back to a customer after five years since we’ve supplied a heat recovery application in a paper mill. Pulp and paper mills are a challenging environment for heat exchangers, due to the presence of colloids flocs or flakes in addition to the employ of aggressive chemical bleaching agents in the water, requiring special corrosion-resistant materials.

The customer wants to recover heat coming from condensation waste, leveraging on the available thermal energy to heat clean water in a collecting tank. The application has the following process parameters:

– Heated water flow rate 108 m3/h
– Heated water temperature min. 32,5° C max. 36,1° C

The new heating fluid has this parameters:

– New heating fluid flow rate 48,5 m3/h
– New heating fluid temperature 81,6° C

After a series of very accurate tests in order to verify the actual efficiency of the heat recovery process, applied in a new section on the factory, we’ve supplied a new immersion TCOIL stainless steel heat exchanger, ensuring the required corrosion resistance due to the presence of bleaching agents in the collected water. The TCOIL has large paths between the plates, because the water in the tank can be very dirt, with the presence of flocs as usual in this kind of industry.

The water flowing inside the TCOIL comes from condensation waste, and the water in the collection tank once heated is re-employed in the production process. Cold condensation waste are also re-employed in the manufacturing cycle.