Reforming Bio-Oil for Hydrogen Production
19 August 2007
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| The bio-oil reforming process. Click to enlarge. |
Researchers at the Department of Energy’s National Renewable Energy Laboratory (NREL), in collaboration with the Colorado School of Mines and Chevron, are developing a process for the low-temperature, partial oxidation, and catalytic autothermal reforming of bio-oil for the production of hydrogen.
The project, which began in 2005 and now runs through 2012, has a 2012 target of hydrogen produced at a cost of US$3.80/gallon gasoline equivalent with 72% energy efficiency. Currently, the practical yield is about 10 wt% H2 with 65% overall energy efficiency.
The fast pyrolysis of biomass—the chemical decomposition of organic material by heat in the absence of oxygen—produces liquid bio-oil (about 75% of the end products), bio-carbon or char (13%) and gas (12%). By comparison, gasification results in about .1 to 5% bio-oil, 10% char and 85% gas.
Bio-oil, while combustible, is not miscible with hydrocarbons. It has a heating value of about 17 MJ/kg and density of about 1.2 kg/. Its viscosity can increase with time.
Although bio-oil can be used directly in some applications (such as power generation), it can also serve as an intermediate for higher grade chemicals and fuels produced via subsequent processing.
Since shipping a liquid bio-oil is much more convenient and cost-effective than shipping the original biomass, bio-oil increasingly is being explored as a key element in a number of biorefinery projects.
There are three primary elements to the NREL process:
A low-maintenance system for volatilizing bio-oil with manageable carbon deposits using ultrasonic atomization to control physical properties and for modifying bio-oil properties, such as viscosity, by blending or reacting bio-oil with methanol.
Homogeneous partial oxidation of bio-oil to achieve significant conversion to CO with minimal aromatic hydrocarbon formation by keeping the temperature at 650°C or less and oxygen levels at a low and steady level.
Under thermal cracking conditions, unconverted methanol and secondary products from the bio-oil-methanol mix predominate. However, under the oxidative cracking conditions, H2, water, CO, and CO2 predominate.
Heterogeneous auto-thermal reforming of the product gas using precious metal catalysts to complete the conversion of the bio-oil partial oxidation gases and vapors to hydrogen. The role of the catalyst is to finish the conversion begun in the second stage and to catalyze the water-gas shift.
Last year (FY 2006), the team developed the method for bio-oil volatilization and the oxidative cracking conversion to CO with minimal CO2. So far this year, they have introduced the catalysts, demonstrated equilibrium conversion to syngas at low temperature and low H2O/C, improved bio-oil atomization, run methanol modeling studies and begun parametric studies.
The researchers will continue catalyst testing and collaborative development with emphasis on deactivation and poisoning. In FY 2008, they intend to begin bench-scale tests for long-term catalyst testing. FY 2010 will see the “go/no-go” on conceptual design, and FY 2011 will see a prototype system.
Resources:
Robert J. Evans, Jonathan R. Marda, Stefan Czernik, Anthony M. Dean, Richard J. French, and Matthew A. Ratcliff; “Distributed reforming of bio-oil for hydrogen production”; ACS 234, FUEL 2
It's a wonder the old time alchemists didn't try to turn gold into lead. Bio-oil may be an intermediate technology that enables heating and electrical generation with low speed stationary diesels. Hydrogen is for rich countries especially those eligible for DoE handouts that 'prove' hydrogen is a winner.
More formally I'd like to see this compared with a range of other hydrogen generation systems such as the solar thermal method. I also suspect that before long someone will be ADDING hydrogen to Bio-oil though I'm not sure what that will produce.
Posted by: Aussie | 19 August 2007 at 10:32 PM
Indeed, I am convinced it will be much more interesting to add hydrogen in order to reform the carbon source to liquid fuils, than to 'burn' the carbon source to produce hydrogen.
It is clear that in the comming years, we will need a lot of gazoline-like fuils for transportation before we convert to other energy sources.
While we can easily make lots of hydrogen using nuclear power, it is not so easy to make lots of hydrocarbons.
It is such a waste to make hydrogen out of hydrocarbons, while we are actually using hydrogen to convert low-grade oil to gazoline.
In the long run (when we don't need hydrocarbons any-more), it will be useful to convert biomass to CO2 (for sequestration) and H2. but this is many years in the future.
Meanwhile, a combination of catalists could be useful : in a reactor we could make hydrogen from biomass, and then use the hydrogen with more biomass to make high-grade biofuels like butanol. If such a 'transportable' unit could be made, it could be installed near biomass-sources, making transport of the pure biofuel very efficient.
Posted by: | 20 August 2007 at 07:08 AM
You can't make hydrogen into asphalt. If you make biomass into asphalt you make a useful product and a carbon sink at the same time, like killing two birds with one stone. If we were to convert all the agricultural waste, organics in garbage and sewage into biofuels we could replace industrial oil uses (making plastics, asphalt, chemicals, etc), that with waste alone, no new farms no cutting down forests.
Posted by: | 20 August 2007 at 07:14 AM
I like the idea of using the carbon for paving. It is probably not as cheap as using oil right now, but combine that with the off patent rubber tire ingredient and who knows. However, several road projects near me were scaled back due to the increase in the price of paving with oil based products.
Posted by: sjc | 20 August 2007 at 08:43 AM
Hydrogen reforming from biomass can be an important transitional step to help prime the hydrogen economy until infrastructure for synthesis of hydrogen from solar or wind energy will be in place.
Ultimately, upon exhaustion of all fossil fuel reserves, hydrogen made from solar and wind energy and transported using various forms of hydrogen carriers, will be the predominant energy currency. Until then, we have got to produce hydrogen from biomass, coal and NG in order for the hydrogen infrastructure to begin to take hold.
Posted by: Roger Pham | 20 August 2007 at 12:57 PM
It is my contention that we transition to renewable energy BEFORE we run out of fossil fuels. That way we have some left for later. It took 100 million years to create the fossil fuels that we are burning up in 100 years. That million to one ratio is obviously not sustainable. What is the hurry? Why are we in such a hurry to burn up all the available fossil fuels?
Posted by: sjc | 21 August 2007 at 12:14 PM
I doubt that asphalt is a good carbon sink. I think eventually, much of the asphalt will be oxidized and digested by micro-organisms if it is not burried deep below the earth. Asphalt is a very low-quality product which needs to be remodelled every few years. In every recycling process, a lot of energy is needed and a few precentages of the mass is evaporated (which is mildly toxic). I think after a few hundred years, a big part of the carbon is recycled to CO2.
While it is obviously better to use "bio-asphalt" than "petroleum-asphalt", I wouldn't call it carbon sequestration.
Further processing of the hydrocarbons to polyethylene and using that to produce roads, will provide a much higher quality road, which will degrade much slower by micro-organisms or erosion, and which will release no toxic products. I fear it will be much more expensive also. But that may change with an extra catalist.
Posted by: | 22 August 2007 at 05:24 AM
i want some more information
Posted by: praqvgeenbhatraju | 28 September 2007 at 04:53 AM