HIGH PROFILE
The pieces are then moved to the business end of the plant – the two thermal conversion reactors themselves . Each one has a 20 t / d capacity . The tyre pieces are loaded into the reactors using a specially designed conveyor belt starting from the rear of the reactor to the front . At this stage Kal Tire still knows which particular used tyre is being recycled and the pieces are weighed a final time before being added . The authorities only want to know that the tonnage that entered the plant was recycled , but some mines also want to know what specific tyres were recycled . For Kal Tire the weighing is very important as well – due to mass balance calculations at the end of the process – comparing the tyre weight to derived products including fuel oil , carbon black , steel etc .
It is a very sequential process – one is being cooled down ready for a new batch while the other is working at high temperature . In the combustion chamber , the grey casing surrounding the reactor , temperatures reach over 500 ° C with temperatures inside the reactor itself varying based on the recipe required for the tyre structure and compound that will be processed . The process starts with LPG fuel but after a certain number of hours , syngas from the process starts to be produced which is reused in the heating process – another aspect that is unique to Kal Tire ’ s facility . This both reduces LPG consumption . The reactors constantly rotate the batch mass to transfer the heat evenly through all the tyre pieces .
So where did the design come from ? Kal Tire initially asked an Italian company to design and assemble a system based on its needs – this was done initially in Italy including testing and review by a Kal Tire team , then it was disassembled and shipped to Chile for reassembly .
From when the burner is switched on to when it is switched off is 24 hours – this includes the heating and pyrolysis . This is followed by another 10 hours of cooling after which the direction of rotation also changes after the temperature finally drops to 80 ° C so that a screw system is able to recover the carbon black which by now is in a powder form . This is one of three products obtained along with tyre pyrolysis oil or TPO , a condensate from some of the gases produced by the burning rubber , and the steel cord itself . Some 6 t of steel cord is all that is left after all the carbon black is removed and by that stage has coalesced into a worm like structure – this is removed by a dedicated truck and then the process is complete . Some of the gases that cannot be condensed during the process are sent to a light oil tank where the gases are condensed using a water cooling system – some of this can then be sent back to the burner , again contributing to energy efficiency . In the combustion chamber heat is also recirculated . The number one challenge , more so than getting required permits for the site , sourcing tyres themselves , or anything else – was getting this sequential process right . Reyes told IM : “ From the very beginning the target was to be able to open the reactor and have steel without any rubber . And we were quickly able to do that , within 26 hours . But doing it at that speed means the syngas is generated over a short period such that it would not be able to be used in the process – and we would have no option but to flare it off , and that is not something that fits with our environmental and sustainable goals . You need to have the right ramp up of temperature over time at the right pressure to produce the syngas at a rate where it could self-fuel the process .”
One of the main characteristics of the Kal Tire plant versus other pyrolysis facilities is also that it is an automated system . Both lines can be digitally managed from the nearby control room and there is an emergency shutdown procedure if needed . Also if the system flags up any issues such as pressure exceeding set parameters , it will automatically put the plant in a safe condition mode where a valve is opened to relieve pressure and all the gases sent to flare . The reactors run 24 / 7 with the control room always staffed by two people – with teams operating on two 12 hour shifts .
Final products from OTR tyres
On to the final products – already today Kal Tire is selling its derived oil , steel and carbon black in the immediate region but at a relatively low price . This includes carbon black to the regional plastic , explosives and rubber industries , with the steel going for scrap to a steelmaker in Santiago .
To enhance the saleability of the carbon black a
Kal Tire Chile ' s Carlos Zuniga and Rodrigo Reyes
lot of R & D is going on at the site ’ s own lab and at Kal Tire ’ s Canada facilities . The powder from the process has high fines and volatiles and the research sees it go through a process of heating , milling and pelletising , with different pellet sizes aimed at different markets .
The heavy and light oils from the process are mixed in a tank and filtered to one product . Some of this oil is refined by a customer to a usable diesel similar to marine fuel , while some of the oil goes to the explosives market for mixing with ammonium nitrate in ANFO . Kal Tire has also bought its own 50 kW generator , and is already testing combinations of its refined oil with standard diesel along with additives to operate it .
Future potential
Overall , the RNG has the capacity to recycle 7,300 t per year of large mining tyres . The growth plan for Kal Tire at the site has the potential for the plant to expand to 22,000 t / y by the addition of two more pairs of identical reactors . There is no doubt this will happen and the area is already being prepared for it , but the exact timing will depend on the timing and size of new contracts . The existing storage and cutting area is sufficient to allow for this . And this will be badly needed as all the mining tyres imported since the beginning of 2023 start to filter through the system under the REP Law . Notably despite some noises , no other mining tyre recycling facilities on this scale or with this sophistication and sustainability have yet been developed in Chile . IM
10 International Mining | AUGUST 2023