Today marks the 100th anniversary of the birth of Prof. Dr. sc. techn. Drs. h.c. Heinrich Schubert. We take this occasion to remember his work in Freiberg and, above all, his contributions to the fields of mechanical process engineering and mineral processing.

Prof. Heinrich Schubert held the chair and served as head of the Institute of Mechanical Process Engineering and Mineral Processing from 1969 to 1991. During this period, he educated around 550 students and approximately 60 doctoral candidates. In addition, he became widely known far beyond Freiberg for his academic teaching, particularly through his various textbooks on mechanical process engineering and the processing of solid materials. For example, he was a visiting professor at the University of Queensland (Australia), the University of Iowa (USA), and the Iron and Steel University Wuhan (China).

Prof. Heinrich Schubert is internationally recognized and honored not only for his teaching but also for his research. His scientific publications are still widely cited today. Toward the end of his active career as a university professor, he succeeded, together with his research group and the university, in bringing the World Congress of Mineral Processing, the International Mineral Processing Congress (IMPC) 1991, to Dresden and organizing it very successfully. It is remarkable that he achieved all this despite the obstacles and restrictions that existed in the former GDR. Obtaining machines, equipment, or specialist literature from the West, as well as traveling to Western countries, was only possible with the approval of the political leadership and, in his case, due to his international recognition.

In honor of his life’s work, he was awarded the Lifetime Achievement Award by the International Mineral Processing Council in 2006. This distinction particularly underscores the significance of his contributions to mineral processing. On the occasion of his 90th birthday, a special issue of the International Journal of Mineral Processing was published, containing contributions from 56 colleagues, former students, and their students from around the world.

The series of images shows several photographs of Heinrich Schubert, some of which had not previously been published online, from the collection of the Institute of MVTAT and the university, depicting him as many colleagues remember him.

The comments and assessments from experts on the occasion of his 100th birthday show that Heinrich Schubert's scientific work is still relevant today and that he has earned his place in mechanical process engineering and processing technology.

Professor Anh V. Nguyen: 

“I had the privilege of knowing Prof. Schubert for many years and spent a very memorable period with him in Freiberg during my Alexander von Humboldt Fellowship (1994–1996). I still remember the many hours we spent together in his office, carefully watching many of his video footages about flotation and discussing flotation fundamentals, bubble–particle interactions, hydrophobic force, turbulence, and mineral processing phenomena. His scientific clarity, discipline, and generosity as a mentor left a lasting impression on me and strongly influenced my own work and thinking. It is an honour to have known him, and I remain deeply grateful for his guidance and friendship.”

Professor John Ralston: 

“I had the great pleasure of discussing flotation science and technology with Heinrich Schubert in 1997, during one of my regular visits to the TU Bergakademie Freiberg, under the then leadership of Hans Schulze and his fine team. I was developing a strong interest in in turbulence and its role in flotation systems, an area in which Heinrich had made remarkable contributions. I found that Heinrich was very open to discussions, was generous in sharing knowledge, with a warm and caring personality. I acknowledge a very fine research engineer and a wonderful man”.

Professor Graeme Jameson:

"I had the pleasure of meeting Professor Schubert on only one occasion, when I visited him in his home in Freiberg in 2017, not long before his death. Long before, I had known about his seminal work on the role of turbulence in flotation machines. I was particularly struck by an observation in his 1999 paper on turbulence-controlled micro-processes, where he remarked that particle–bubble attachment almost exclusively occurs in the zone of high energy dissipation rates, i.e.in the impeller-stream. This was a remarkably prescient remark, based on his experimental observations. In more recent years, extensive CFD modelling has confirmed Professor Schubert’s conclusion. Since the effective volume of the impeller and stator in a mechanical cell is perhaps 10 - 20% of the total cell volume, one is entitled to speculate on the function of the region outside the impeller zone. The obvious response is that most of the volume in a mechanical cell is due to the need to allow the bubbles to escape into the froth. We conclude that the residence time of a flotation feed in a mechanical cell is strongly related to the time required for the bubbles to rise into the froth, as well as the kinetics of capture of particles by bubbles! Professor Schubert was a giant in the field of flotation, helping with his colleagues at the TU Bergakademie Freiberg to lay the foundations for the study of the physics of bubble-particle interactions. His contributions to flotation fundamentals will long be remembered."

Dr. Martin Rudolph:

"I had the honor of co-supervising Professor Heinrich Schubert’s final doctoral student, Dr.-Ing. Duong Huu Hoang, alongside him from 2013 until his passing in 2018. Our regular meetings first took place in his office in the Karl-Kegel-Bau at TU Bergakademie Freiberg, and eventually at his home. For my colleagues and me, it was always a special moment to see the 'great Prof. Schubert' driving into the courtyard, even well into his 80s. He was a truly impressive personality with a wealth of stories to share. Both Duong and I learned an immense amount from him. What was particularly striking was his ability to provide not only the right answer to any question but also the exact references, all while challenging us with insightful questions of his own. In our final conversations, he repeatedly emphasized how grateful he was for such a long and fulfilled life. I have also heard many stories from colleagues around the world about their encounters with Prof. Schubert; they all speak of his tireless interest in mineral processing and mechanical process engineering, and his willingness to always take the time for scientific discussion. I am deeply grateful to Prof. Schubert for sharing his time and wisdom with us, and for both challenging and supporting us throughout our journey."