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Dynamotive’s Low Cost Path for BioOil Co-Processing in Oil Refineries
4 April 2008
Initial tests by Dynamotive Energy Systems Corporation conducted on hydro-reforming of its pyrolysis-derived BioOil have shown positive results indicating a low cost path to upgrading BioOil to higher value products, according to Desmond Radlein, Director and Head of Research.
Dynamotive provides a fast pyrolysis technology that uses medium temperatures and oxygen-less conditions to turn dry, waste cellulosic biomass into BioOil for power and heat generation. BioOil can be further converted into vehicle fuels and chemicals.
BioOil is a highly oxygenated, polar hydrocarbon product that typically contains about 46 wt% oxygen. Some of the oxygen is present as free water which constitutes about 25 wt% of the BioOil. These properties render BioOil immiscible with fuel grade hydrocarbons which typically contain little or no oxygen.
In principle, oxygen could be removed by hydrotreating BioOil with hydrogen. But two facts militate against this. First, raw BioOil is thermally unstable with a great propensity to form coke when subjected to hydrotreatment temperatures. Secondly, removing all the oxygen with hydrogen would require about 60 kg per tonne of BioOil to give at most a 50 wt% yield of oxygen free hydrocarbons.
Furthermore, at the present time, hydrogen is expensive at the small scales at which BioOil is typically produced. The lowest cost hydrogen is available at petroleum refineries, so it is desirable to find a low cost process to convert BioOil to a form in which it could be co-processed in an oil refinery. Given this, Dynamotive concentrated on finding a low cost solution.
Dynamotive’s “hydro-reforming” process indicates a pathway to we have a path to achieve those objectives. The process has the following features:
The BioOil is stabilized so it can be hydrotreated in a refinery without the risk of coke formation.
It is deoxygenated to a sufficient degree to render it miscible with typical refinery hydrotreater feeds.
The oxygen content is substantially reduced so that any further hydrogen requirements during hydrotreatment at a refinery are minimal.
Hydrogen is internally generated from the water present by reforming a portion of the BioOil so that most of the oxygen is released as carbon dioxide and the net hydrogen requirement is very small (about 18 kg per tonne).
The product is water free as the residual water forms a separate phase.
Only a small amount of gaseous hydrocarbons like methane (that represent a waste of both carbon and hydrogen) are formed.
Acetic acid present in the raw BioOil can be recovered as a valuable by-product.
Process conditions are relatively mild (e.g. pressure < 1,200 psi and temperature < 350° C). Together with the reduced requirements for hydrogen, Dynamotive expects that it may enable small-scale processing of BioOil to provide a renewable source of hydrocarbons from whole ligno-cellulosic biomass.
Rejection of the oxygen as carbon dioxide rather than water does decrease the ultimate maximum yields of hydrocarbon fuels—from ~ 50 % to about ~ 35 %. But we believe this is more than offset by the benefits listed above.
We will continue our research in this area with a view to optimizing our findings and process. It is early days, but we believe that the path is sound. While the company is optimistic about the path that these findings indicate, there can however be no assurance that the company’s research will in fact ultimately yield a technically and commercially viable process.
—Desmond Radlein
April 4, 2008 in Biomass, Fuels | Permalink | Comments (8) | TrackBack (0)
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Refineries can also take vegetable oil as feedstock and hydrotreat that to regular alkanes indistinguishable from fossil diesel compounds. That means car manufacturers do not need to adapt their designs to support chemically more aggressive non-traditional compounds like FAME.
The proposed process for upgrading biocrude is analogous, but the original feedstock much less valuable (straw, forestry waste etc.) The relatively low yield is compensated for by the relative simplicity of fast pyrolysis reactors. A network of these, set up close to where the solid feedstocks are produced, can act as an intermediary for the refineries. Moreover, because the latter are involved and the resulting product readily distributed to consumers, the oil industry may actually welcome this particular biofuel technology.
Posted by: Rafael Seidl | Apr 4, 2008 7:29:52 AM
RS,
I agree. You do not have to replace all oil with this or anything, just use it instead of some fossil fuels. Some might say that it would only encourage the same habits, I say one step at a time.
Locating the bio micro refineries close to the feedstock source is common sense. You can transport a liquid product by rail or truck. This is nothing much more than we do now.
You want to add as much value locally as you can. If you can take the oxygen out locally, the the transported product is more valuable and you transport less of a substance that you can not use.
Posted by: sjc | Apr 4, 2008 8:08:29 AM
The chemistry described for Dynamotive's "hydro-reforming" sounds very similar to that in Direct Liquefaction. It would be interesting to compare the overall energy balance of Dynamotive's two-step process: fast pyrolysis plus hydro-reforming with direct liquefaction. Has anybody done this already?
Posted by: Marc von Keitz | Apr 4, 2008 8:48:02 AM
The yield is stated as "35%", but is that as a fraction of mass input or energy input?
Posted by: Reality Czech | Apr 4, 2008 9:03:18 AM
I would guess mass. I look at biomass to liquids as 35% mass and 70% energy, but that is a guess. This is another reason why you want to convert to the highest energy at the lowest mass as closely as possible to the source. You have less mass and volume to transport. That might be H2, but transporting and storing are problems for now.
Posted by: sjc | Apr 4, 2008 11:11:03 AM
The 18kg of offsite hydrogen implies steam reforming of fossil fuels which we are supposed to get away from. Rather than involve distant petro refineries it would be better to make hydrogen onsite then a finished fuel. These mini-refineries could be located next to sawmills, avoiding the need to move large quantities of 'vinegar'. I say vinegar because Bio-oil seems to have a lot of water and acetic acid.
Posted by: Aussie | Apr 4, 2008 2:32:39 PM
That sounds like a plan. It is a good engineering exercise to design a mini bio refinery for location on sight. Before you know it, the refinery might not be so mini if there is enough biomass available.
This might get rid of some of the NIMBY factor as well. In California, the oil refineries are located along the coast where the tankers can dock. They are pretty ugly and not good for air quality. Every now and then one of them has an explosion and/or fire.
I keep thinking of all the wonderful benefits of changing the model. No tankers, no oil spills, no oil refineries belching smoke, no more tanker truck accidents on the highway, no more polluted ground water. But that would only happen with piped CNG or EV.
Posted by: sjc | Apr 4, 2008 3:46:47 PM
Reality Czech
well in fact this percentage is confizing, it sometimes refers to the amount of eneryy containts in the dry biomass, sometimes to the weight ratio of conversion, Unless they define a standard for efficiency of conversion we will never know what these numbers mean. But so far I have assumed it refers to the initial amoubt of energy that you would get burning the biomass. If you take the FT for CTL they claim 50% conversion efficiency, which means 3 tonnes of coal yield 1 tonne of gazoline, 3 tonnes of coal more or less equal to 1 tonne of oil in energy containt (which means by the way that the EROI of CTL is only 2 which is quite bad)
Posted by: Treehugger | Apr 4, 2008 11:14:13 PM
