THE FIELD OF CERAMIC INDUSTRY FORESEES A DIGITAL PRINTING METHOD TO APPLY COLORS, IMAGES OR DRAWINGS TO THE SURFACES OF TILES OR OF BIGGER SLABS, THUS OBTAINING HIGH QUALITY AND RESISTANCE ON WASHABLE SURFACES THAT UNDERGO HEAVY CHEMICAL AND MECHANICAL STRESS.
Color application is performed using an organic carrier that – during the following firing – turns into substances characterized by a low olfactory threshold. These substances are then released through the ovens’ atmospheric emissions, often causing odorous issues in the surrounding area.
Atmospheric emissions coming from ceramic material digital printing have the following characteristics:
VARIABLE | CHARACTERISTICS |
---|---|
Temperatures | Average high, between 140 and 200°C |
Presence of volatile organic compounds (V.O.C.) | Aldehydes in particular – characterized by a high odorous charge |
Presence of inorganic compounds | Hydrochloric and fluorhydric acid, sulphur dioxide, ammonia and carbon monoxide |
Presence of inorganic dusts | Originated from the processes of dry neutralization of the above-described inorganic acids |
Humidity | High |
Metals | Present |
Operational cycle | Both during the day and the night, for the whole duration of ovens operation |
Depuration goals are mainly to reduce the odorous impact of the emissions in the atmosphere as much as possible, respecting the foreseen limits for each pollutant without creating secondary pollutants and with capital and handling costs that are acceptable for the production process.
Different possible solutions have been evaluated to solve the environmental issue – which in some instances has caused concern for the nearby population. The options considered solutions both upstream the production processes – therefore intervening on the formulation of the inks used in the printing process – and downstream, adding an air depuration plant.
In this last case, the regenerative thermal oxidation technology has proved to be particularly effective.
Regenerative thermal oxidation is a chemical process that allows – with high temperature and the oxygen normally contained in the emissions – the transformation of organic pollutants into sub-products with reduced environmental impact: water and carbon dioxide.
Since the conversion needs a temperature up to 800-900°C, we foresee a particularly efficient energy recovery which – thanks to the use of specific ceramic filling materials – can limit operating costs bound to the use of auxiliary fuel feeding a dedicated burner.
Regenerative thermal oxidation is a frequently used process for treating atmospheric emissions containing V.O.C. and released by different industrial productive processes.
The application in the ceramic industry had to foresee specific aspects, aimed at reaching the following goals:
Here are the results: