The benefits of cryogenic grinding for recycling tyre and rubber

Discover the benefits of cryogenic grinding for recycling tyre and rubber

In the last years, more and more companies have turned to an environmentally sustainable business model. One sector that has emerged in this field is the recycling of used and worn tyres, also as a result of EU regulations on the recycling and recovery of end-of-life materials.

On an industrial level, pulverising processes that are traditionally carried out at room temperature can be conducted at cryogenic temperatures with the aim of obtaining a better quality of the ground product and less energy consumption.

That is why products which have low softening points, elasticity and thermosensitive characteristics due to the presence of elastomers, such as tyres, are efficiently grinded by bringing them to their embrittlement temperature using liquid nitrogen.

Cryogenic grinding is successfully used in the milling processes of rubber and elastomer scrap and in all areas where cryogenics is more efficient, without damaging the physical-chemical or cross-linked structure of the finished product.

Cryogenic Application – Liquid Nitrogen

Liquid nitrogen has three main functions: it rapidly cools the material to embrittlement temperature before it enters the grinding mill. It keeps the processing temperature constant by absorbing heat developed during the grinding operation.

Cryo ground substances have different physical characteristics from those obtained by traditional grinding processes, precisely because of the way in which the structure of the material is broken down.

Here are the main differences between the two processes:

 

CRYOGENICS

– Cryogenically embrittled tyre rubber produces homogenous, crystalline, cubic grains;

– Better production yield

– Better final product quality, without brittleness or breakage

– Reduced energy consumption

– Increased quality of finished product

– Less processing waste (due to overheating)

– Greater product fineness and homogeneity

– Reduction in the amount of material to be reprocessed

 

ROOM TEMPERATURE

– Tears in the initial matrix due to the smoothness of the crystalline planes or special lattice structures

– Powders with non-uniform physical characteristics

– High energy consumption due to low hourly output

– Possibility of material melting on grinding rotors

– Low quantity of fine particles

– High recycling of materials above the sieve.

But what are the most relevant parts of this process? Let’s see how they work and what the main solutions involved are for.

Overhead receiving hopper and dosing unit integrated into the structure

The entire system is designed to contain and utilise cryogenics only at a specific point in the plant, the other areas work at room temperature such as the containment hopper  and the dosing hopper,.

Control is carried out by means of sensors, valves and metal detectors to correctly monitor the material.

Metal detector

By its nature tyre powder contains various metal contaminations, a good defection system, either simple or more advanced, is necessary for preserving the grinding tools.

Liquid Nitrogen Proportional Valve

It controls through electronic PID regulation the amount of liquid to be injected into the circuit, working in synchrony with the recovery of cold gases and the working temperature of the grinding chamber.

Special cast counter rotating impeller

Highly efficient grinding impellers with wear-resistant discs and cylindrically shaped cast pegs, specially designed for highly abrasive polymers.

Easy access to the grinding chamber and simple replacement of pins and wear parts due to the coupled disc construction are the strengths of this solution.

Nitrogen, which is connected via a hose to the cryogenic screw, is atomised via nozzles on the rubber.

The controlled working temperature ensures maximum efficiency of the system, the elevated position without pipeline handling of the product, and the shape contained in the armaflex shell allows the operating frigour to be maintained and processing energy to be optimally utilised.

Case Study STM: MPC 400

The Contraplex MPC400 counter-rotating pin mill has a tyre powder output of approx. 500 kg/h at a grain size of 100%<500µm

The ideal working temperature is approx. – 28°C and the thermal insulation conditionsallow for low management consumption as well as the possibility to recycle non-exhausted cold gases.

This mill was integrated into customer’s production line, the sieved product was then placed in the big bags. The over sieve > 500µm is small and there is thus a recycling of low quantities that do not and vary the productivity of the raw material.

In conclusion, after the collection and block shredding phase, and the 5mm grain milling with 99% elimination of textile and metal fibres thanks to the STM Microtec plant, a 100% cryomacination <500µm was achieved.

HAPPY HOLIDAYS

This year STM Microtec decided to support Fondazione Giacomo Ascoli Onlus that provides the most qualified medical assistance and psychological support possible to children and adolescents suffering from onco-haematological pathologies, to guarantee them greater chances of recovery and the best quality of life during treatment at the Onco-Hematology Department of the Del Ponte Hospital in Varese (Italy).

May this holiday season be filled with peace, health and positivity!

Our offices are closed from 27th to 30th December.

See you in 2023!

 

STM END OF YEAR PARTY

STM END OF YEAR PARTY

 

During the end of year party, it was illustrated how in 2022 STM continued its growth path in name of the 4 essential pillars on which the whole group is based: #innovation, #humanresources, #digitalization and #sustainability.

It was, as always, a pleasant moment for meeting, discussing and witnessing the successes achieved.

We are ready and thrilled to face the goals and new challenges we have set ourselves for 2023.

 

STM MICROTEC: INDEPENDENT AND VERSATILE LABORATORY MILLS

STM MICROTEC: INDEPENDENT AND VERSATILE LABORATORY MILLS

 

Since 1971 STM Microtec has been providing integrated solutions and tests for grinding and dosing. A wide and complete range of customized services, from single machines to complete packages for numerous industrial and environmental applications.

 

STM stands out for its concept of intelligent work in a dynamic world, where low-cost research with high physical and chemical data acquisition is essential to take into account new production possibilities.

 

The Laboratory Line represents the ideal choice for a research and development department and for companies with limited production quantities but of high-quality standards.

 

With its autonomous workstation, the pilot mill is a true autonomous and multifunctional laboratory plant that is highly innovative from a technical point of view.

The operating principle of the installed machines is the same as that of industrial production machines.

The possibility of testing the micronization on a small scale guarantees the transfer of the laboratory process to an industrial scale machine, thanks to the identification of the grinding mill, and a linear and precise increase in the machine production factor.

 

The GALILEO LINE offers 3 different functions:

  1. MJS – compressed gas jet mill (air / nitrogen);
  2. JCF – impact grinding mill;
  3. SDF – separation and classifying mill.

 

The three machines are specially designed for the production of small batches, the equipment and electronic devices used follow high design standards and the technology applied is at the forefront. The mechanical part is integrated with a series of electronic devices integrated as well into the transformation process to analyze the process parameters and the analytical recovery of p physical, chemical and mechanical data received by the instrumentation during the grinding of the product.

 

The ZERO LINE consists of:

  1. MDS – dosing system with volumetric augers and gravitational weight control;
  2. CLC – Cryogenic Auger (Liquid Nitrogen System);
  3. PIN – Mulino a Pioli – Pin Tool;
  4. NET – Mulino a Rete – Net Tool;
  5. EV – Venturi Ejector – Propulsion.

 

The operating principle and the conformation of the working chamber allow the application of cryogenic grinding or cryopulverization systems, for the artificial embrittlement of tenacious products at room temperature.

 

The STM Lab Line offers an ideal solution for obtaining process parameters, thanks both to the extreme quality of the granulometric results and its versatility.

 

STM has a Pilot Plant equipped with an efficient Laboratory where it can simulate and verify the performance of its technologies, varying the input material and the operating and process parameters by adapting the solutions to every need.

 

JCF IMPACT MILL WITH DYNAMIC CLASSIFIER

JCF IMPACT MILL WITH DYNAMIC CLASSIFIER: THE STM SOLUTION FOR PRODUCING FLOURS WITH HIGH PROTEIN CONTENT

 

Nutrition is a powerful mean of prevention and a fundamental tool in dealing with everyday life. The increased awareness of the importance of a balanced diet and the use of natural products has led to greater use of high protein flours.

 

These are flours with a high concentration of proteins and fibers and with a very low content of carbohydrates and fats used both in bakery and pastry, and in the production of superfoods and sports foods, as well as vegetable powders for the production of scrubs or for make up.

 

STM has always collaborated with the food, parapharmaceutical and cosmetic industries to obtain high protein flours that retain the fundamental organoleptic properties and have a higher protein value than the starting material.

 

Particularly suitable for this sector is the JCF series grinding and selection mill combined with the SDF dynamic classifier, for maximum protein extrapolation.

 

JCF Impact Mill

It consists of a horizontal geometry grinding unit and specific tools for this application, shaped to provide maximum efficiency between grinding impact and product ventilation.

The ground particle passes through a selection sieve in a single compact machine, with a determinable and constant particle size 100% <50µm.

 

SDF dynamic classifier

The milled product enters the separation chamber, where the forced dynamic rotation between the static rotor and the dynamic classifier with adjustable rotation are able to divide and extract a significant amount of extra fine particles 99% <20µm.

SDF is integrated to the instrumentation for detecting the protein content, through an in-line analyzer.

The classifier unloading cone, makes the coarse product with fraction 20 ÷ 50 µm flow easily, while the finer dust is collected in the dedusting filter.

 

The JCF impact mill allows you to adjust the grinding parameters so that the flours are grinded to the necessary fineness with a high concentration of protein powders and the in-line separation of the coarse product poor in proteins.

The operational advantages of the JCF mill are:

  • Maximum energy efficiency
  • Low noise emission
  • Minimum maintenance
  • Compact machine, minimum space required
  • High reliability and quality of the system
  • Easy cleaning and maintenance
  • Reliability
  • Grinding of a wide range of materials
  • Possibility of temperature conditioning.

 

The machine can be easily opened for checks, cleaning and maintenance as it is equipped with a pneumatic mechanism that facilitates the opening of the grinding and classification chamber.

 

Do you want to learn more about JCF? Contact us.

 

STM MICROTEC EXHIBITS IN POWTECH 2022!

VISIT STM AT GLASSTEC 2022!

Increase of end product quality and process optimization with the cryogenic grinding of coffee beans

Vegetable proteins, derived from legumes, dried fruits and vegetables: protein concentrates and healthy energy thanks to the strength of grinding