Sequence and description of stages in the production process of ceramic tiles:

1. Preparation of ceramic bodies.
2. Tile production.
3. Recycled processing waste.
4. Smoke treatment.
5. Waste management.
6. Optimizing energy consumption.
7. More information on processing waste.


Preparation of ceramic bodies.
The raw materials used to produce ceramic tiles reach the plant by truck. They are unloaded and heaped in bins inside the warehouses used to store raw materials, in covered areas where they are not at risk of being washed or blown away.



The individual raw materials are selected using special mechanical shovels and sent by conveyor belt to storage silos, where they are later selected, dosed, and weighed automatically, in a cycle managed by a computer program, based on the formulations of the different bodies.



The resulting mixture is sent to the temporary holding silos above the grinding mills. This mixture, along with a set percentage of water and recycled scraps, is then finely ground in the continuous ball mills, by the mechanical action of the grinding media (natural pebbles or sintered aluminium balls).



The result is an aqueous suspension called "slip", which is sieved and then sent to the spray-drying line (atomizer).
The spray-drying process takes place inside a cylindrical chamber where the slip is sprayed by high-pressure pumps into a stream of hot air that evaporates the water in the droplets, producing a special powder made of tiny spheres, called "atomized material".



After this stage the processing cycle begins that will determine the shape and appearance of different types of tiles.

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Tile production
The atomized body moves on to the pressing stage, where it is shaped into tiles using special moulds, and pressed to give it the density needed for the specifications of the finished tile.



After pressing, the material is dried out completely to eliminate the water still in it (which is necessary for the pressing stage).
The pressed tiles, which are shaped but not yet fired, move on to the glazing stage where "glazes" are applied to the face that will give the product the desired appearance and colour, visible at the end of the production cycle.



Afterwards, the glazed tiles are "fired" using the single-firing method, where the tile body and the glazes applied to it are fired at the same time.
With firing, the raw materials and the glazes take on substance and turn into the "tile product" that everyone is familiar with. The firing process takes place in kilns that are 80 to 140 meters long, which the tiles move through on refractory rollers. Special burners heat the inside of these kilns to temperatures of up to 1200° C, and so a series of reactions and mineralogical transformations complete the process of creating "ceramics".




A mixture of raw materials enters the kiln, and after a firing cycle of approximately 40 minutes, tiles are ready, whose fundamental characteristics (shape and colour) have already been determined.
The product undergoes selection and inspection of both appearance and dimensions, then is boxed, packaged, and ready for use.




Every step of the process described here is performed using automated machinery that eliminates physical strain for workers, so that they are primarily responsible for running and overseeing the lines.

> Production process flow(.pdf).

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Recycled processing waste
Ceramic waste from the production cycle is made up of semi-finished products, finished products, and liquids created throughout the production process that fall out of the line accidentally or are removed because of production requirements.
They primarily consist in:

1. Unfired waste from pressed or glazed tiles that have not yet completed the cycle through the firing stage;
2. Fired waste from tiles that have already completed the full processing cycle;
3. Dust. General waste made up of raw materials that have not yet been processed or which have undergone some processing stages, such as spray-drying and pressing;
4. Processing water from washing during preparation of the basic tile bodies, containing suspended raw materials;
5. Processing water from washing during preparation of glazes and cleaning the glazing lines, primarily containing suspended glazes;

The categories listed here below are treated in different ways according to the type of waste.

1. Unfired waste. Material generated during the pressing, drying, and glazing processes is collected in airtight containers at these points in the line and taken to the raw materials warehouse, where it is put into special bins. The mechanical shovel then loads it into a hopper and transfers it to silos, where it is selected, weighed, and sent to be dosed.
2. Fired waste made up of tiles that are collected as scrap after firing, primarily as rejects from the final sorting phase. Fired tiles are finely ground and the resulting powder is sent to the storage silo for later selection, weighing, and dosing.
3. Dust. Dust is primarily produced in the handling of raw materials and in certain stages of the processing cycle (when material falls from one conveyor belt to another, is loaded, unloaded, picked up, etc.). These stations, as well as any others that could generate dust emissions, are equipped with special suction hoods connected to filtration systems. The dust collected at the bottom of the filters is collected and pneumatically conveyed to collection silos, then put back into the production cycle after being picked up and dosed just like raw materials.
4. Processing water from washing during preparation of tile bodies. To allow correct dosing of components, the water is treated to separate the suspended raw materials it contains. The treated water is used as grinding water, while the slurry is filter-pressed and dosed for use in the preparation of tile bodies.
5. Processing water from washing during preparation of glazes and cleaning the glazing lines. This water undergoes a chemical and physical treatment process to obtain clean water and a thickened slurry. The water is used as grinding water and the slurry, after filter-pressing, is collected in a bin to be reused in the preparation of tile bodies.

Careful research is devoted to the reuse of waste and the dosing of various mixtures; its aim is to make the most of these materials without altering the characteristics of the tile body and thus the finished product, safeguarding the final quality standards that have been set for the product.
The entire recycling process is constantly monitored and managed through an automated system that guarantees correct formulation.

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Smoke treatment
During the firing of ceramic bodies, at temperatures that may even exceed 1200° C, an entire series of mineralogical and chemical changes take place, along with the decomposition of several stable compounds, specifically those containing fluorine.
As well as products of combustion, the smoke includes other substances, such as fluorine and possibly lead, since particles of the latter can be given off by the glazes, some of which may contain low percentages of this element.
To keep these substances from being emitted into the environment, the kilns are equipped with filtration and removal systems that make it possible to filter all the particles and remove the fluorine using special reagents (air-floated lime).
All the filtered powders and the reagent are collected at the bottom of the filter, machine-bagged, and sent to authorized disposal units.

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Waste management
Waste management is a stage of the process to which particular care is devoted.
All waste produced during the work cycle is classified according to European coding, sorted, and collected separately in clearly identified, marked areas which meet the technical requirements set by waste management regulations.
The different types of waste are then sent off to predetermined uses, which can be summarized as follows:

In-house recycling, for processing waste

The manufacturing industry, for recyclables (paper, wood, plastic, iron, etc.)

Recycling consortiums (oil, batteries, etc.)

The remainder (less than 1%) is sent to authorized dumps that Marazzi has carefully selected and evaluated.

All management of waste accounting and documentation (forms, stamps, registries) is carried out through a centralized computer system that prints out the necessary documents and keeps records of the amounts of waste that have been handled.

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Optimizing energy consumption
To obtain the thermal energy needed in its production cycle, Marazzi uses a "clean" fuel, methane gas.
Industrial management optimizes the use of thermal energy through a series of measures aimed at reducing the amount needed in the process.
Since 1992, Marazzi has installed cogeneration plants with gas turbines that produce electricity and heat.
The heat is used in the spray-dryers to dry the slip, and the electricity is used to meet plant system demands. In other uses, especially firing, energy consumption is optimized through the best available technology, with high-efficiency burners, excellent kiln insulation, heat recovery, and computer monitoring of firing curves.
Reduced consumption also results in reduced gas emissions.

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More information on processing waste.

> Recycling of processing waste(.ppt)

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