StobbeDPF - all the way from an idea over R&D to a unique product
Porous Re-crystalized Silicon Carbide ceramics for separating particles from hot gases – such as from diesel engine exhaust gases – was all created during the period 1986 to 1994 by Stobbe Tech A/S.
The development work was financially sponsored by:
- Danish Department of Energy’s Research project from 1987 to 1992. Purpose to develop porous structures intended for diesel particulate filters and hot gas dust filters - 2 mil € budget.
- Danish Department of Industry project from 1991 to 1994. Development of ceramics for hot gas filters - budget >1 mil €.
- Per Stobbe’s private pocket.
It all started with the shown canned 5,66”×6” Cordierite Wall-Flow-Filter (WFF) tested at Per Stobbe’s final thesis as Mechanical Engineer at DTU (The Danish Technical University) in 1985. It took only one hour on the 3 cyl Buck diesel engine, couple to a Schenk dyno to destroy, melt the center out of the first ever Cordierite WFF in Denmark. This raised the question – how can our international society solve the diesel engine particulate emission problem with WFF based on this fragile material?
The remarkable Re-crystalized Silicon Carbide ceramic technology we developed from scratch allowed large, complex dimensions and high porosity structures to be shaped from relatively low-cost coarse grinding SiC grain by extrusion. The extruded bodies dried with only 2% shrinkage and fired at 2500°C with exceptional only 1% shrinkage. Such low shrinkage figures are quite unusual in the ceramics industry. All was developed from scratch - the complete basic science and the manufacturing methods, all the manufacturing equipment such as the complicated extrusion die heads, the wear resistant extruder, the 3 dimensional drying methods / equipment and in particular the challenging design and construction of furnaces capable of operating at 2,500°C in controlled atmosphere.
Over 8 years we were 9 people focusing on developing the bi-modal ceramic method based on cheap SiC grinding powder mixed with an organic binder to shape by extrusion the multi-channel honeycombs. The entire set of production equipment, all the related technologies and even real-life testing on a high number of different vehicles/engines was developed in-house. An impressive achievement for such a small company! At this time, no company had even thought about this principle for “low-cost” manufacturing of thermal stable porous ceramics.
Stobbe Tech A/S received valuable help from:
- Professor Spencer C. Sorenson at Department of Energy Techniques at The Danish Technical University
- Associated professor Jakob Weiland Høj and Associated professor John Emil Engell both from Department of Mineral Industry at The Danish Technical University
- Associated professor Athanasios Konstandopoulos from CPERI in Greece
- Managing Director Richard Utzschneider from Norton GmbH in Bexback, Germany now Saint Gobain Industri Keramik, SGIK in Rödental, Germany
This project and initial work became the fundament for numerous technologies, created many jobs and improved the quality of life for humans in general hereafter. Unfortunately, the technology we developed for DPF purposes was 10 years ahead of its time or the legislation 10 years behind!
The experienced reader will know the Japanese company Ibiden at the same time in parallel developed their quite different mono-modal SiC technology based on the much more expensive finer SiC grain. Further the experienced readers are aware that three different ceramic material technologies later dominated the market for DPF and thus competing:
- Cordierite WFF from Corning and a variety of manufactures - being an oxide ceramic characterized by very low thermal conductivity and thermal expansion
- ReSiC mono-modal technology from Ibiden also manufactured by Saint Gobain SGIK
- ReSiC bi-modal – the Stobbe Tech development - a non-oxide ceramic material characterized by very high thermal conductivity and relative cheap raw materials and manufacturing
The route in the western world to control particle emission from diesel engines has been long and troublesome. The better and more efficient diesel engines the more difficult it becomes to capture and combust the sot, carbon particles. The widely accepted way to reduce particulate emission is by filtering the exhaust gas through typically a high temperature stable Wall-Flow-Filter devise.
Cleaning up exhaust gas from diesel engines is though relatively easy with one of many different sizes of the StobbeDPF. Which has been commercial available since 1992 in 90 (later 200) cell-per-square-inch (CPSI) design ranging from 1 to 40 litre of volume. Later from various suppliers.
StobbeDPF electric heated
Electrical regenerated 15 liter DPF
close contact electrical regeneration
Stobbe Tech A/S developed and patented 1988 the bi-modal ReSiC honeycomb substrate (re-crystalized Silicon Carbide) concept for accurately controlled pore size, porosity and high permeability for capture of diesel engine exhaust particulates. Finally, this turned into the 100% owned daughter company NoTox A/S in 1992.
Manufacturers of the StobbeDPF technology later became:
- dinex.dk - most successful danish manufacturer based on license
- liqtech.dk - aggressive successful company
- NoTox - the factory in Svendborg, Denmark cost 63 mio € to build - now owned by Landson
- ctisa.fr- created a variant of copies without license
- pirelli.com- acquired a license
You will find extensive information about engine emission at www.dieselnet.com and under research/gas filters on this website.
One of many complete DPF packages for different forklift trucks ready to install into the narrow engine compartment. All custom designed by Stobbe Tech and fabricated by daughter company NoTox. Advanced engine modification performed the sequential DPF regeneration. The green forklift truck equipped with dual system integrating electrical heating for off-duty regeneration.
- Unfortunately, Per Stobbe 1996 lost all the technology, companies, patents to a hostile raid performed by a range of greedy danish investors, the danish patent agent used for years and two danish banks.
- Corning purchased on commercial condition the NoTox technology package from the "new owners" 1998.
- Two years later Scandinavian Brake Systems (www.SBS.dk) via some other investors obtained the NoTox package from Corning.
- SBS did some really bad management decision, which gave SBS an accumulated financial loss ranging 75 mio € in 2015.
- The two other surviving manufacturing facilities in Denmark was LiqTech and Dinex (DPF production closed 2017).
- Landson purchased 2017 the NoTox assets from the involved banks at 5 m €.
Corning was not part of the bad management, greedy investors in Denmark - Denmark lost 500 jobs.
Per Stobbe - 2017