7. Our presses have recirculation already included, what difference will it make?
Press manufacturers are increasingly designing recirculation already into the dryers. There are two methods of recirculating the dryer air – active and passive control.
Active control of recirculation varies the airflow for optimum conditions to maintain constant solvent levels. The exhaust is minimised and the solvent concentration is increased to the maximum safe operating limit. In this way, the load on the abatement plant is always minimised and ensures that the RTO is operating auto-thermally as much as possible.
Passive recirculation has fixed recirculation and exhaust with gas monitors to measure the LEL of the solvents which alarm and ultimately stop the machine. However, press dryers are normally set-up for the highest theoretical operating conditions with very high coverage at high speed – in reality, these conditions rarely occur. As a result, the production loading is significantly less than maximum. The result is larger abatement plant, higher running costs of abatement plant and reduced control of the recirculation in emergency conditions.
It is usually relatively easy to improve the efficiency of fixed passive recirculation by modifying the recirculation with active modulation of the recirculation to respond the production conditions.
A flexo press with fixed recirculation and LEL sensor for passive control.
EPM can advise you if any further modification will be beneficial.
However, if the press recirculation is efficient, following the 3 steps towards compliance is still the best solution…
Step 1 – Install dampers and controls to divert the exhaust the air to atmosphere or abatement.
Step 2 - Monitoring the emissions profile
Step 3 – design and install abatement
If you would like to discuss any aspect of the information outlined in this question, please contact EPM at firstname.lastname@example.org.