In order to explore in depth the potential of the microfuel technology we need to compare it with other liquefying technologies on the market.
Today I want to start with MWDP's closest relative: pyrolysis.
Task 34 of the IEA Bioenergy initiative focuses on Pyrolysis from Biomass. They run a very informative website that has been around for some time and was integrated into Task 34 some time ago. I suggest visiting that site to anyone who wants to know more.
What is pyrolysis?
The most simple definition can be found on the mentioned website: "Pyrolysis is thermal decomposition occurring in the absence of oxygen". Following that definition MWDP is definitely a form of pyrolysis as the decomposition is at least in part thermal, while assisted by microwaves and the zeolite as explained in the MWDP article. On the other hand, it doesn't easily fit into any of the common categories of pyrolysis.
What types of pyrolysis can be identified?
Usually 3 types of pyrolysis are recognized: Fast, intermediate and slow. Most data of the following table is again taken from the definitions on the Task34 website (MWDP data has been added by us):
Mode
|
Conditions
|
Liquid
|
Char
|
Gas
|
Fast
|
≈500°C, short hot vapor residence time >1sec
|
75%
|
12%
|
13%
|
Intermediate
|
≈500°C, hot vapor residence time 10-30 sec
|
50%
|
25%
|
25%
|
Slow-Torrefaction
|
≈290°C, solids residence time 30 min
|
-
|
82%
|
18%
|
Slow-Carbonization
|
≈400°C, long vapor residence time, hrs > days
|
30%
|
35%
|
35%
|
Gasification
|
≈800°C
|
5%
|
10%
|
85%
|
MWDP
|
≈280°C, solids residence time 30-45 min
|
35%
|
50%
|
15%
|
We can see clearly that MWDP fits in none of the 3 categories. Lower temperatures also suggest a higher energy efficiency of the process. Next lets have a look at typical quality parameters.
Pyrolysis oil is usually called bio-oil, which is a bit misleading at a water content between 20-30% which cannot be separated easily. It can only be burned in direct combustion or upgraded in complex, large scale refinery-style processing. The pyrolysis liquid has a very low heating value of typically 16-19 MJ/kg. For more quality information see again our reference website.
Now we compare this with what we call bio-oil in the MWDP process: Water content is usually below 3%, direct combustion is a possibility, but it can better be used directly in any HFO specified engine, which are usually stationary diesel engines in power plants or on ships. The biggest quality difference can be noticed in the heating value, which reaches up to 45 MJ/kg, similar to standard diesel fuel. Upgrading of MWDP derived bio-oil to achieve ultra low sulfur diesel or SPK (=biojetfuel) is a relatively simple process mostly involving 2 phases: a secondary distillation and a hydrotreatment, both typical phases in any modern refinery.
But not only the MWDP bio-oil shows such big quality differences, the same thing is true for the char fraction. Heating values of up to 30 MJ/kg are unprecedented in any other pyrolysis technology as much as other quality parameters. MWDP char meets the highest quality parameters of industrial applications, where all other biochar was rejected as insufficient.
So where might the future of pyrolysis lie?
Some authors have started already to add a forth category of catalyst assisted processes. While not yet commonly accepted, that is actually the right category for TCDP and MWDP and probably the only category that will be able to bring about true innovation for pyrolysis.
