Sunday, January 23, 2011

The development of MWDP

Today we finally reached the first article about Bionic's very unique, proprietary technology. Don't try to copy it, its patented :-). We baptized it microfuel about five years ago. In order to differentiate it from other depolymerization technologies we call it microwave depolymerization or MWDP. The name describes however only half of the truth. Actually the better term would be microwave catalytic depolymerization. You simply cannot always put everything in a name. But lets start from the beginning.

Bionic's founders and core team came together for one reason: frustration about other technologies. All we wanted to do in the beginning was to implement an existing thermal catalytic depolymerization process, but the one we had chosen didn't really work well on a commercial scale. So we started looking for alternatives, but we really couldn't find anything satisfactory. That was the beginning of Bionic...

Others had already identified a major hurdle for all TCDP implementations: for optimal processing results the reaction mass had to be heated from the inside out. Biomass is a very poor heat conductor, so it will stay cool at the inside, while already turning into carbon on the outside, sticking to the wall of the reaction vessel. A fact well known to every cook. That's why he keeps stirring in his pots all the time... However, we didn't like solutions used by others who invented stirrers and scrubbers or use complex screw or auger reactor designs. We were looking for a more elegant, mechanically robust solution. So we started experimenting with a simple kitchen microwave and saw the principle results we were looking for. Quickly better suited microwave equipment was built and endless test runs started. Like many successful business we also started in the garage.

The basic process was clear from the beginning: Take some hydrocarbon containing feedstock, mix it well with the zeolite catalyst and expose it to microwave irradiation. At some point vapor starts coming out. Collect all the vapors, condense them and separate the water from the oil. Everything has to take place in an oxygen free environment. Low pressure is helpful.

From the humble beginnings hundreds of small steps had been taken to optimize everything for the best yield and product quality. One of the main issues was proper feedstock preparation and a perfectly homogeneous mix with the zeolite. Excellent results were achieved by shredding the feedstock and pelletizing it together with the catalyst. That way we were able to increase the material density and eliminate any problems of the uniformity of the zeolite distribution throughout the process. The result is a higher specific weight and energy content in the feedstock an a much more efficient use of the zeolite.

We realized, that it is of high importance to heat the material in the right way over a certain period of time. Going too fast is as ineffective as going too slow. Specific heating patterns were developed to reach perfect conditions for different materials. The optimal maximum reaction temperature turned out to be below 300°C, a fact that makes the conversion very energy efficient. A continuous reactor design had to reflect these necessities.

Many different additives have been tested to further improve reaction conditions, some for chemical reasons, others in order to improve reactivity in the microwave fields.

By now our tests revealed a clear picture: We had succeeded in combining 2 independently functioning chemo-physical mechanisms into one, a form of microwave pyrolysis and the well known catalytic depolymerization we started from. Both mechanisms are reported many times in scientific literature, with widely known parameters and conditions. However, we brought them together for the first time and clearly achieved positive results by doing so. None of the individual processes can match those. Here is the chemo physical background in a few simplifying terms: Both technologies are in itself capable of breaking up molecular bonds (cracking). The trick is how to control the process, which means the cracking has to stop at the intended size and quality of molecules. Here the zeolite's function as a molecular sieve comes into play, while the temperature profile of the reaction determines most of the oil quality.

An important addition to all of this is the fact, that the pellets keep their basic structure throughout the process. They are kind of "sweating out" the oil and the remainder is a perfect biochar with unmatched qualities for either combustion or as a soil amendment (at least in the case of a biomass feedstock). We will talk about the char in detail in a dedicated post soon.

The next challenge on the development path was the design of a continuous reactor that would replicate all the positive properties we had identified in the lab. What the result looks like can be seen in detail in this presentation and a lot more information can be found on the Bionic website. By mid 2010 we had finalized the design of a commercial reactor based on the findings from a working pilot.

From here on there will be a lot of posts describing in depth various details and implications of MWDP including various analysis results. Unfortunately we are not able to publish everything as some of the material has to be kept confidential due to client requests.