TECHNOLOGICAL DEVELOPMENT
THE ISSUE OF TYRE RECOVERY
AND TECHNOLOGICAL DEVELOPMENT
The history of the thermic processing of used or otherwise degraded tyres dates back to the 1980s, when the author completed his dissertation concerning the destruction and stabilization of polymers. During this period he solved problems of utilization of thermic processes within the research team of the Institute of Theoretical and Applied Mechanics of the Czechoslovak Academy of Sciences.
The issue of thermal decomposition, commonly referred to as "pyrolysis", is the process by which organic matter is heated in the absence of air. Pyrolysis, originally referred to as "dry distillation", carries several limiting phenomena. The first is the necessity for external heating of the mass in the reaction vessels. This makes the process more expensive. The second phenomenon is related to the behaviour of the decomposing mass in the reactor. First, the vapours of low-molecular-weight disintegrative products - gases - leave, then the fractions of the above-boiling products which condense to liquids, and finally, the carbonaceoussolid remains stay in the reaction vessel. These phenomena negatively affect the possibilities of continuous processes.
The issue of convex heating was solved by the author at the end of the 1980s when he worked at the Department of Technical Physics and Electrical Engineering at the Institute of Chemical Technology, Prague. There the possibilities of microwave and high-frequency heating of matter were tested at this period.
However, even these procedures did not solve the negative phenomenon of high energy demand for decomposition.
In the 1990s, the author developed a process of heterogeneous heating the mass using superheated gases. This procedure allowed the decomposition of polymers by a continuous way. However, there remains an unresolved problem with external energy for gas heating.
Another phenomenon that could not be eliminated at that time was the structure of the arising products. In this case, they had an identical distribution curve for the individual hydrocarbons, but in the form of an aerosol.
The aerosol could not be stored and had to be treated as gas, ie for immediate consumption.
This development led in a cogeneration unit with an internal combustion engine, before which a refuse polymer decomposition unit was placed.
The technical solution required a unit for each engine what made it difficult to use. Attempts to precipitate aerosol onto the liquid and gaseous components have led to high voltage devices at the beginning of this century. It was assumed that the electrostatic negative charge of the aerosol particles would discharge at the device anode. The efficiency of this process was small. Progress in this area was brought by the results of research between 2011 and 2013, when liquid and gaseous aerosol components were separated by mechanical separators. Further development has helped increase the efficiency of separation above 90%.
At this stage of knowledge, there were already enough results to construct a continuous polymer decomposition device.
Considering that conventional polymers are thermoplastics which become a viscous liquid when they are heated, development has focused on polymer materials where this phenomenon does not occur. These masses are rubbers that retain their shape even at decomposition temperatures. It loses its shape only after all the polymer mass has been exhausted. As the remainder of the decomposition, soot particles remain as the remainder of the reinforcing filler in rubber and the steel cords serving as the tire reinforcement.
Between 2016 and 2018, development work was realized on a continuous tire disposal facility. The result was a functional prototype of a device with an hourly capacity of 1000 kg of processed tires in semi-automatic mode. In this case, the semi-automatic mode means that the machine only requires attendant when tyres are filling. Other cycles and modes are under computer control.
The environmental impact of equipment could be caused by emissions of decomposition products into the air. These are eliminated by the process being carried out under reduced pressure so that they cannot expand into the atmosphere. Sulphur dioxide emissions in the energy recovery process are eliminated by calcining the combustion products. In the combustion of sulphur-containing fuel, sulphur dioxide is bound to non-volatile gypsum.