Heat energy consumption 5% lower than other construction solutions, which means a reduction in running costs of tens of thousands of euros a year with respect to standard plants. That’s just one advantage of the new range of spray dryers by Sacmi, designed to give the tableware industry excellent efficiency, flexibility and process repeatability.
What makes the Sacmi plant engineering solution so outstanding is, above all, the technological process of removing moisture from the slip by spray-drying it in a continuous, automatically controlled manner that lets producers obtain powders of consistent moisture, shape and particle size; the process minimises heat energy consumption and produces powders perfect for the subsequent pressing phase. That result is guaranteed by the use of advanced fluid-dynamic design algorithms that allow control of the air speed and temperature profile inside the distributor and the tower where the slip is dried. Even distribution of the air vortex inside the tower also prevents any build-up of moist material along the walls, a phenomena that can jeopardize both cycle continuity and final product uniformity.
The presence and coordination of two fans - the main one that regulates the flow of air extracted from the tower and the pressurisation fan which regulates air inflow – allows maintenance of a limited yet constant negative pressure inside the tower. The use of air-flow burners, which have replaced those of the traditional blow-air type, and special shaping of the hot air distributor, which generates a vortex that facilitates heat exchange with the material, maximises efficiency and minimises consumption with respect to alternative solutions. The constructive shaping of the SACMI distributor, located in the upper part of the tower and made of stainless steel, also limits the vertical height of the machine (and, therefore, the height of the shed needed to house it). The distributor is designed to move freely during the heating and cooling phases independently of the cylinder, thus reducing maintenance requirements and lengthening the working life of the spray dryer, especially in the zone most subject to thermal stress.
Special measures have been adopted to meet the specific quality/cleanliness needs of the tableware industry, such as the choice of stainless steel with a high nickel content for all machine parts that come into contact with the process air and the spray-dried powder to prevent the formation of oxides that might contaminate the final product. The slip injection system, which consists of filter-equipped piston pumps, is also made of special materials to prevent product contamination and ensure first-rate final quality.
Lastly but not least is the exhaust air purification system with stainless steel separator cyclones that allow powder residues to be fed directly back into the body preparation cycle with high efficiency and with low pressure loss.
The wet scrubber solution involves only limited water consumption thanks to the inclusion of a water recycling unit.
Thick layers of insulation (rock wool and ceramic fibre) inside the combustion chamber, the air distributor and on the outside of the drying chamber keep working temperatures high, thus limiting heat dispersion as much as possible.
These construction solutions – together with the advanced plant control system that features dedicated automation software - ensure that the SACMI spray-drier offers maximum efficiency during the drying process, one of the most delicate stages of the entire production cycle in terms of both energy requirements and observance of finished product quality.
Distribution of the air vortex inside the tower