The offset printing process is based on feeding continuous paper from a reel to the machine so that it passes successively through the different printing bodies where the image is reproduced.
The ink that is applied to this process is dried by heat and, therefore, the paper web must pass, once printed, by an oven.
After this stage, the paper web is cooled, humidified again and prepared to move to the cutting, folding and gluing stage, if the work requires it.
The main stages of the process are:
Paper feeding. Paper unwinding equipment with different tension compensation rolls and automated paper roll change.quipo de desbobinado del papel con diferentes rodillos de compensación de tensiones y cambio de bobina de papel automatizado.
Printing. An aluminium plate that is in contact with wet rollers and inking rollers is placed in each printing body to transfer water and ink to the plate, thus completing the planographic printing process characteristic of the offset system. A rubber blanket is also placed (intermediate element, since the offset system is an indirect print) that allows the transfer of the image from the plate to the paper.
Accelerated drying. The oven performs a heat drying process that stabilizes the ink so that the paper web can be handled immediately.
Reconditioning of the paper band. Cooling of the web and rehumidification, to avoid cracking of the paper in the subsequent folding stages. Stabilization of printing is achieved here. The process takes place continuously, with application of water and silicone. At this stage no gas emissions are produced, since the process is carried out in recirculation.
Auxiliary stages. Cutting the band, folding and gluing, if necessary, stacking and palletizing. At the printing and drying stages, the organic solvents that are part of the composition of the inks applied are evaporated. Therefore, an extraction system is necessary to remove these solvents from the interior of the rotary presses and from the oven.
This generates a significant flow of gases at a temperature of about 120 °C containing about 2 g/Nm³ of organic compounds. Therefore, it will be necessary to clean them before emitting them into the atmosphere.
Of all the available systems, the thermoreactor is the most suitable to carry out the cleaning, because it is able to achieve an auto-