News: Weibold Academy

In our last article (Part I) we addressed the question of how the advantages of a classic batch-reactor process design can be combined with those of a continuous process mode. In the current article (Part II) we address some characteristics and advantages of a batch reactor regarding the thermochemical reactions and their effects on the end products. We refer to the extensive scientific literature and to the findings of successful companies in the industry.

Pyrolysis is a thermochemical pathway to treat vulcanized rubber for the recovery of valuable products. It involves the decomposition of the rubber at high temperatures (400 – 900°C) in the absence of an oxygen atmosphere. The main products of pyrolysis are a solid fraction, usually raw carbon black (according to ASTM D8178); a liquid fraction comprised of light oil, heavy oil, and tar; and a gas fraction. [Ramirez-Canon et. al., 2018]

This article is a review by Claus Lamer, a Co-Founder at Carbon Recovery GmbH. Weibold’s Academy article series discusses periodically the practical developments and scientific research findings in the end-of-life tire (ELT) recycling and pyrolysis industry. One of the goals is to give entrepreneurs in this industry, project initiators, investors and also the public, a better insight into a rapidly growing circular economy. At the same time, this article series should also be a stimulus for discussion.

The advantages of pyrolysis to tackle the world's growing disposal problem with end-of-life tires (ELT) in terms of a circular economy were described extensively in the last decade. Pyrolysis is a thermal process that converts organic rubber material into low molecular weight compounds such as pyrolysis gas, pyrolysis oil and raw recovered Carbon Black (ASTM 8178-20a). In contrast to the incineration of ELT, which is often condescendingly referred to as "thermal recycling" or „waste-to-energy“, pyrolysis does not destroy any raw materials, but breaks down the waste product into its chemical raw material components and makes them available for the circular economy. Fortunately, this is in the meantime confirmed by the great demand from the chemical industry for products from ELT pyrolysis.

Today, tire recycling and cement industries are indeed intertwined. An abundance of scrap tires at specialized stockpiles, as well as well-organized tire collection systems and waste management plans, make it possible to (re)use precious rubber and create value out of waste. Tire-derived fuel (TDF) proves to be an alternative to fossil fuels used in cement production, mainly due to high calorific value of tire rubber and its low price. However, TDF emerged as a popular alternative to fossil fuels in cement production for yet another important reason – environment. Tire-derived fuel helps lower CO2 emissions and serves as a cleaner alternative compared to fossil fuels. Added to this, using scrap tires in cement production helps clean up vast scrap tire stockpiles, which otherwise pose threat to environment and which are often unsuitable as feedstock for tire recycling plants due to its exposure to radiation, sand or other contamination.

Attempting to cut costs while launching a tire recycling or pyrolysis business, companies often fall prey to low-quality equipment manufacturers whose equipment does not fulfill to their promises. Typically, such a low quality equipment has far more attractive prices and very often comes from countries, where labor and material costs are still very low. Although seemingly benefitting its buyer through low initial capital investment, such equipment can kill a young pyrolysis company or seriously undermine its operation. In this article Weibold focuses on issues of low-priced pyrolysis machinery and sheds light on the most common problems occurring with such pyrolysis equipment suppliers.

Despite hard efforts of the tire recycling and pyrolysis industry to develop new markets and increase recycling rates, recycled rubber based product markets demonstrate only moderate growth. To tackle the problem and allow thousands of tons of precious materials go back to consumer goods, numerous end-of-life tire management organizations, companies and research labs do their best to find new markets and develop innovative products out of scrap tire rubber.

Pyrolysis is an age old concept, whereas pyrolysis from end-of-life tires (ELTs) is a nascent field in an immature market. Today, in the ever present push towards a circular economy, this technology receives ever more attention in the tire recycling community – investments in tire pyrolysis businesses increase, technology keeps advancing and ever more operators appear on the market worldwide.

By its nature, tire recycling and pyrolysis are capital-intensive businesses which require rather big investments to lay a foundation of successful production. The industry is constantly changing. Existing markets are under threat, other markets emerge. More than ever it is important to facilitate and support R&D efforts. Associations and businesses around the world work hard to protect existing and build new markets for the industry by developing new value-added products from the main output materials of the industry – recycled rubber granulates (crumb rubber), pyrolytic fuel oil and recovered carbon black (rCB).