Solvent recovery system savings

It has become necessary for printing industry players to adapt to the reality of becoming more sustainable in order to survive and be profitable. The installation of a solvent recovery system means less solvent going into waste streams and a significant reduction of CO2 emissions (up to zero) and can protect companies from the possible future implementation of a carbon tax, says Gianmario Melogli, sales manager of Donau Carbon Technologies (DCT).

Since 1994, when DCT installed the first classic solvent recovery (SR) plant in a converter factory, 24 systems have been installed worldwide. In 2018, the company patented the game-changing X Compact Solvent Recovery (X-CSR) technology using nitrogen gas (N2) and vacuum regeneration, designed for single and multiple solvent situations, with resounding success, Gianmario reveals. 

‘Today, solvent recovery technology isn’t only reserved for large factories with numerous printing machines, but converters with a solvent consumption below 1 000 tons/year can also benefit from the installation of a DCT Solvent Recovery plant as it will reduce the consumption of solvents, the cost of which has increased,’ he explains.

The classic solution used by DCT is based on the use of large horizontal adsorbers with carbon inside and uses the following steps:

1. Depletion of O2 from adsorber and regeneration circuit. 
2. Heating of the nitrogen in the closed circuit. 
3. When the carbon in the adsorber reaches the necessary temperature, rather than condensing it in the closed loop, the solvent is sucked out by a vacuum pump and condensed using an efficient process and the raw solvent is then separated by distillation and the cooling phase is started. 

As a result, the thermal energy necessary for the regeneration of the carbon decreases up to 30% of the amount of heat necessary for the regeneration of the carbon of a classic plant. DCT calls this patented regeneration process Circular Optimisation Regenerative Energy (CORE).

‘The main problem converters can have with the installation of a solvent recovery plan is when some solvents used to dilute the inks cannot be separated from others by distillation; this can happen, for instance, when methyl ethyl ketone (MEK) is used together with ethyl acetate,’ says Gianmario, ‘however, most of the time, it is quite easy to find appropriate inks that are ketone free.’ 

Gianmario notes that the payback of a solvent recovery plant is quite fast, but depends on the amount of solvent used for the ink dilution. ‘For instance, supposing that the cost of the solvent is €1/kg and the cost to recover the solvent is below €0.2/kg, then the saving for a converter using 

1 000 tons of solvent per year would be about €800 000,’ he describes. ‘The higher the amount of solvent, the shorter the payback time, and after this, the annual savings become pure profit. Thanks to solvent recovery, some DCT customers realise a profit that is in the range of 10% of their turnover.’