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Harvesting green energy: pyrolysis is not only a production method--it can also be used as an analytical tool to study second generation feedstocks.

In the world of biofuel, pyrolysis is normally thought of as a large-scale process where heating occurs in an inert atmosphere, ultimately producing an end product--typically a biodiesel. However, the process actually begins in a laboratory. This is where scientists use pyrolysis as an analytical tool to study the effects of temperature on different bio-source materials. Understanding how source material breaks down in the lab helps point chemical engineers in the right direction when they are responsible for scaling up to a pilot reactor and ultimately final production.

By studying the effects of pyrolysis on a microscale, researchers have an analytical tool that allows many samples to be run easily under controlled conditions. Being able to quickly run a high volume of small samples should result in savings of time and money when scaling up, either to a larger laboratory or pilot reactor. Source materials currently being studied in laboratory pyrolyzers include switch grass, wood mass, waste plants and municipal waste.

Modern pyrolyzers

Today's laboratory pyrolyzers study sample sizes in the micro-to-milligram range and offer variable set points and heating rates. Since the pyrolyzer is merely serving as an accurate, repeatable heat source, the actual analysis must be accomplished by a laboratory analyzer, for example, a gas chromatograph (GC) or mass spectrometer (MS). In most cases, the "hyphenated" technique of GC-MS is employed and can provide quantitatable results on each of the individual compounds formed during the pyrolysis process.

Although pyrolyzer specifications vary by manufacturer, most laboratory pyrolyzers have adjustable set point temperatures (as high as 1400 C) and adjustable heat rates. Some pyrolyzers allow programmable heat rates from a slow 1 C/hr to a nearly instantaneous 20,000 C/sec. More advanced laboratory pyrolyzers are also able to study the effects of variations in background gas. Typically, GC carrier gas is used, normally helium. But, when the background is a non-inert gas (such as air or an oxygen mixture) users get different chemistries during pyrolysis because of partial oxidation reactions.

However, laboratory pyrolyzers do present one challenge for the scientist to contend with: sample size limitations. Since many biofuel source materials are non-homogenous in nature, getting a representative sample may not be easy. To help overcome this, it is important to make certain that the samples are ground fine and well mixed before analysis. Sometimes even these measures are insufficient, in which case several representative samples can be run under the same analytical conditions to confirm sample homogenization.

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Some recent developments in laboratory pyrolyzers include the addition of two other process variables: pressure and catalysts. Having the ability to adjust pressures and insert catalysts enables researchers to study all the variables likely to be encountered in the final manufacturing process. The most advanced laboratory systems can now allow for pressure adjustments up to 500 PSI and sample heating up to 1400 C. The resulting hot gas from the pyrolyzed sample can then flow through a heated catalyst bed before being analyzed by the GC or GC-MS. The researcher can easily change catalyst type, thereby allowing for full study of the process variable.

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From forensics to biofuel

Ultimately, the biofuel researcher is typically looking to see how the source material's biopolymers, lignin and cellulose, break down to compounds that can be further refined into a biodiesel. Lignin is a complex, cross-linked aromatic biopolymer that can comprise as much as 30% of a plant's material. Essentially insoluble, it is responsible for much of the heat produced when plant materials are burned. When pyrolyzed, it produces mostly substituted phenolics, including a series of methoxyphenols and dimethoxyphenols.

Cellulose, a glucose polymer, produces considerable char, water, carbon dioxide, and many polar organic compounds when pyrolyzed. Significant among these are levoglucosan and furans such as furanone, furancarboxaldehyde, and hydroxymethyl furancarboxaldehyde. Some researchers are also interested in the total char content. This can be achieved by weighing the sample before and after pyrolysis to determine what is left. If the pyrolysis temperatures were high enough, most of the remaining residue should be char unable to pass through the GC.

CDS Analytical is a U.S.-based company that has been producing pyrolyzers for 40 years. Traditionally, the primary application for laboratory pyrolyzers has been with R&D of industrial polymers and forensics; however, this valuable research tool is finding rapid acceptance in the expanding biofuel market as well. Current users include many government agencies and universities including the National Energy Research Lab (NRL), Lawrence-Berkley, Univ. of Iowa, and U.S. Dept. of Agriculture--along with many European, Chinese and Latin America labs.

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All source materials mentioned here are currently being studied, as well as a host of others including sugar cane, alfalfa stems and canary grass. The very latest subject of study employing laboratory pyrolyzers is algae. Under the right conditions, algae can contain well over 40 percent of its body weight in oil. Pyrolyzers are being used to study the types of oil and quantitiate the amount. This knowledge will aid producers in understanding the best time to harvest this miraculous energy source.

At a glance

* Pyrolysis effects on switch grass, wood mass and waste are currently analyzed in labs.

* GC-MS allows quantitatable results of individual compounds.

* Pyrolyzers study energy source materials to optimize the best harvest times.

Online

For additional information on the company discussed in this article, see Laboratory Equipment magazine online at www.LaboratoryEquipment.com or the following website:

* www.cdsanalytical.com
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Title Annotation:FuelTechnologies
Publication:Laboratory Equipment
Date:Jan 1, 2011
Words:908
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