New challenges for the SRF production in the cement industry: Corrosion protection and fire prevention

For many decades, the waste management industry has significantly contributed to the reduction of CO2 emissions and therefore to climate protection. Billions are being invested in designing innovative manufacturing processes. In addition to reducing carbon dioxide (CO2), nitrogen oxide (NOx) and mercury (Hg) levels, a particular focus is on preserving resources. Furthermore, high-quality alternative fuels (RDF, SRF) increasingly replace fossil fuels such as lignite, oil and natural gas to supply the industry with CO2-friendly energy. Energy generated by alternative fuel is used to produce electricity and process steam as well as to fuel calciners and main burners e.g. in cement plants in an eco-friendly way. But not all alternative fuels are the same. Cement kilns, in particular, require high-calorific SRF, which has to meet strict specifications in terms of particle size, energy content, density and moisture content. The increasingly high demand for top-quality alternative fuels calls for highly productive solutions and smart RDF and SRF production facilities that additionally extract as much recyclable material as possible and substantially reduce the energy required during production. Furthermore, the industry has to adapt to increased waste volumes and new potentially hazardous input materials.

The Austrian company ThermoTeam Alternativbrennstoffverwertungs GmbH, a joint venture between Saubermacher and Holcim, formerly Lafarge, is one of the pioneers in the production of alternative fuels, which invested in the future circular economy more than twenty years ago. Lindner Recyclingtech has been on board as a partner from the very beginning and designed the entire line, which was successfully commissioned in 2003. The challenge: unsorted municipal, commercial and industrial waste. The requirement: high-grade, high-energy SRF for the main kiln at the Holcim cement plant in Retznei. The solution: a comprehensive processing facility with special primary and secondary shredders, ferrous and non-ferrous metal separators, and a wind sifter including feeding systems, conveyors and discharge belts. The facility was approved according to the strict criteria of the Austrian Waste Management Act (AWG) to comply with emission and immission limits. In 2013, ThermoTeam received the Environmental Protection Award of the Province of Styria (Austria) for this concept. “We found Lindner to be a reliable partner: from concept to installation and service support,” says a ThermoTeam employee.

Since Lindner’s facility was commissioned in 2003, the volume to be processed has doubled. While the input material was 50000 t in 2006, more than 100000 tons have been processed annually until 2018. To date, SRF has helped Holcim save 1.5 million tons of carbon dioxide (CO2) just at its cement plant in Retznei in the south of Austria. This corresponds to the amount of CO2 that an average car would emit while circumnavigating the earth approximately 280000 times.

ThermoTeam has invested in more machines from Lindner Recyclingtech to cope with a further increase in processing volumes and problematic materials found in waste. These materials include rechargeable lithium-ion batteries and materials that may react during their cycling process to produce corrosive acids. After 16 years and more than 70000 operating hours, the old Lindner primary shredder was replaced by a Jupiter 3200 equipped with Lindner’s Fire Prevention System (FPS). Four shredders from the Komet High Performance (HP) series, including corrosion protection package, are used for secondary shredding.

Less energy, greater power and throughput

When processing industrial, commercial and municipal waste, difficult to shred materials such as textiles, fabrics and interwoven plastics can be fed into the pre-shredding process. High volumes of tough materials in the waste require more power when shredding. The Jupiter 3200 is one of the longest-standing single-shaft primary shredders on the market. The countershaft belt drive provides additional rotational energy. The increased flywheel mass releases additional power reserves when needed, ensuring high throughputs even with difficult-to-shred materials without an increase in energy consumption.

“The Jupiter series is very popular and often used in SRF production facilities. Many clients, including ThermoTeam, were won over by the resistance to non-shreddables, the tried-and-tested cutting system and the easy maintenance,” says Stefan Scheiflinger-Ehrenwerth, Head of Product Management at Lindner-Recyclingtech.

Transverse discharge conveyor increases non-shreddables removal

Nowadays, the waste bales delivered to SRF producers are often pre-sorted and include fewer recyclables. Despite all this, they may still contain non-shreddables, iron and non-metal scraps as well as recyclable plastics. To achieve the calorific values required for cement production, valuable materials and non-shreddables are also removed from the primary shredded waste in downstream process steps. Essentially, the Jupiter series can also be equipped with a transverse discharge conveyor to allow the output material to lie as thinly as possible on the discharge conveyor belt. This enables magnets, separators and wind sifters to more efficiently sort out the materials that are not desired in SRF production. In addition, valuable raw materials such as waste metals and PO plastics, which are in great demand on the market, can be returned to the recycling process in line with the circular economy principle.

How to meet the new challenges

Apart from the input volume increase the type of non-shreddables changed. Increasingly, in addition to tough and recyclable materials, flammable materials and rechargeable lithium-ion batteries find their way into the pre-shredding process. If these types of materials occur to an increasing degree, not only can some particles heat up, but the risk of fire also increases. To meet this challenge, ThermoTeam invested not only in the Jupiter 3200 but also in Lindner’s Fire Prevention System (FPS).

The Fire Prevention System is fitted to the discharge conveyor and uses an infrared sensor to detect potential hazards. This modern solution cools overheated particles on the discharge conveyor in a fully automatic, targeted and dosed manner, effectively preventing potential fire hazards. The temperatue-resistant infrared system cleans itself and monitors the entire cooling section, adapting the cooling process to the hazard so as to not over-wet the material.

“We still see consumers who dispose of flammable materials and batteries in waste. Devices with rechargeable lithium-ion batteries have especially increased. These are particularly flammable. If a lithium battery is broken or damaged, temperatures can quickly peak. They soon drop again but never entirely level out. The FPS quickly detects these temperature peaks and possible fire hazards,” explains Stefan Scheiflinger-Ehrenwerth.

In general, waste is much more contaminated these days. According to several studies the lack of correct separation behaviour leads to this increase of problematic materials in waste. Biowaste and organic residues are particularly problematic. Understanding today’s challenges, Lindner-Recyclingtech offers special corrosion protection packages. The Komet HP secondary shredder series in use at ThermoTeam is equipped with stainless-steel protection panels to protect exposed areas and components, and the screen cassette is made out of austenitic stainless steel.

Smart, energy-saving and efficient SRF production facilities particularly support the cement industry in increasing high-class output in terms of quality and safety, as well as in achieving its ambitious goals for reducing CO2 emissions and optimising the energy balance.


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