Progress 06/01/07 to 02/01/09
Outputs
OUTPUTS: The original work plan consisted of 7 tasks. Some of which were to be completed by Frontline, others were to be done by CSET (ISU). Due to CSET's other obligations, they were unable to complete the tasks assigned to them. Thus it fell on Frontline to complete all of the tasks in addition to designing and building a new pyrolysis system. Task 1, installation of the Baghouse Filter, has been completed. A high temperature fabric filter was designed and constructed by Frontline. Task 2, collection, preparation and characterization of the biomass, has been completed. Ultimate, Proximate and BTU data was obtained from Hazen labs in Colorado. Task 3, conducting of pyrolysis tests, has been completed using the reactor designed and built by Frontline. The work plan outlined eight bio-oil samples that were to be generated from varied feed stocks (wood and DDGS), filtration (cyclone and baghouse) and cooling (water and methanol) methods. These were done with three duplicates (DDGS + cyclone + water, wood + cyclone + water, wood + baghouse + water). Task 4, bio-oil stability tests, has been completed on all 11 samples using a rotary viscometer and temperature controlled water bath at 40 degrees Celsius. Task 5, determination of char and alkali metal contents in oil, has been completed. Char content was measured for all 11 samples using 0.1 micron syringe filters. Alkali and alkaline earth metal content was measured by nuclear activation analysis (NAA) by the USGS lab in Denver for the four samples indicated in the work plan with one duplicate (wood + baghouse + water). Task 6, reactor operations test support, was intended to be done by CSET, thus Frontline was left to support their own efforts. Task 7, writing of the final report, is completed by the current work. Additionally, the oils were analyzed for moisture via Karl Fisher titration. PARTICIPANTS: This work was carried out by the hard work of the following individuals: John Reardon, the PI; Paul Evans, project engineer; Adam Kufner, analytical technician; Jordan Funkhouser, test technician. Frontline would like to thank Tim Debey and others from the USGS lab in Denver, Colorado for graciously offering to perform the NAA testing of the bio oil samples. TARGET AUDIENCES: This work was carried out with the objective of advancing the state of knowledge regarding production of high quality bio oils through fast pyrolysis of biomass. This is an area that is of interest to academic institutions as well as petroleum refiners and other commercial organizations. Distributed production of pyrolysis oils is a potential method for farmers and/or coops to produce a value added energy product from agricultural residues. Pyrolysis systems could also be targeted to forest management entities needing to remove dead trees that represent fire hazards. PROJECT MODIFICATIONS: The one major change to this project was CSET (ISU) chose not to participate in this project, and thus not having the needed pyrolysis reactor, Frontline elected to design and build its own pyrolysis system in addition to assuming responsibility for all the tasks that were to be completed by that organization.
Impacts
The entrained flow reactor design was intended to be simple, but resulted in operational difficulties, such as frequent plugging during operation. In contrast, the baghouse filter operated flawlessly. No fouling, or permanent pressure drop, was observed during the period of operation. No ESP was present after the condensers, and so there was some slip of bio-oil aerosols. The high residence times of biomass in the reactor (due to clogging) resulted in unexpectedly high moisture content, over 40%. This high moisture content led to low viscosity oils and relatively low increases in viscosity over the observed period. Bio oils from cyclone screening had an average viscosity increase of 15% over the 4 hour accelerated aging period compared to 1% for oils prepared through baghouse filtration. Standard deviations of the viscosity increases are high, at 43% and 6% for the cyclone and baghouse sample respectively. A considerable number of samples showed a decrease in viscosity over the time period. A similar phenomenon was observed with the 30 day aging trial. The large variation in viscosity change is likely due to heterogeneity of the bio oils (phase separation) which makes it very difficult to get representative samples. Other researchers have developed homogenization methods for pyrolysis oils that could be employed in the future to help minimize data scatter. Thus, while an improved stability was demonstrated as a result of hot gas filtration, the statistical confidence is not very high. Bio oils derived from wood feedstock had higher levels of char retained in the oil than that of the oils from DDGS. This is likely due to the initial particle size of the wood being smaller than that of the distiller's grains, resulting in smaller char particles. DDGS bio oils from cyclone filtration had an average of 0.9wt% char compared to 0.4% from the baghouse. Wood bio oils prepared through the cyclone had an average of 2.0wt% char compared to 0.4% from the baghouse. Sodium, potassium, calcium and magnesium were measured by NAA. The wood feedstock contains a total of 1372 ppm of these metals compared to 11733 in DDGS. The wood bio oil condensed after the cyclone had 177 ppm measured alkali and alkaline earth metals compared to 43 ppm for the baghouse sample. This represents reductions of 87% and 97% respectively. The baghouse outperformed the cyclone by 76% for the wood feedstock. The DDGS bio oil from the cyclone contained 259 ppm of these metals compared to 57 from the baghouse. This represents reductions of 98% and 99.5% for the cyclone and the baghouse respectively. Clearly the baghouse is a superior method of particulate removal, compared to the cyclone, for pyrolysis vapors. However, there is still a significant amount of char and ash ending up in the pyrolysis oils. No correlation could be drawn between the stability of the bio oils and the levels of either the char or trace metals present in the samples. The reasons for this are likely the high moisture levels and heterogeneous nature of the bio oil samples.
Publications
- No publications reported this period
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Progress 06/01/07 to 05/31/08
Outputs
OUTPUTS: Frontline is approximately 70% complete with our phase-1 project effort. We have been operating the bench scale reactor since May 2008 and have completed initial test results for some of the planned test cases. This first task and most significant effort was originally intended to require only minor modifications to an existing fast pyrolysis test bed at the Iowa State University. As a result of changes at the university involving other funding commitments, ISU was no longer able to support our planned test program. ISU and Frontline agreed that the best course of action would be to build a second pyrolysis generator system at the BECON facility. Frontline's pyrolysis system includes a metering device to regulate the amount of feed to the reactor, an ablative-type-flash pyrolyzer, a methanol/water cooling injection point, a high temperature filter, and a condenser. Frontline has completed the design, fabrication and commissioning of the new test bed. Full operation was achieved in May 2008. The decision to build a new test bed put Frontline behind schedule, but we were able to improve certain aspects of the Py-Oil generator design to help facilitate integration of Frontline's Py-Oil vapor filtration equipment (as required by our Phase 1 work plan). Initial tests have been conducted using the new pyrolysis system. Pyrolysis oil samples have been generated from pyrolysis vapors that were passed through one of two filtration devices prior to condensation. Baseline pyrolysis oil comes from the condensation of vapors after passing through a cyclone separator (a low efficiency filtration device). Cleaner oil samples (lower in particulate matter) were generated from the condensation of vapors that had passed through a high temperature fabric filter. In order to achieve high filtration efficiencies from a fabric filter it must be properly seasoned. This process has been started, but it is believed that more operating time (accompanied by more thorough seasoning) will lead to even higher (>99%) filtration efficiencies. Current filtration efficiency has not been quantified. Stability of the pyrolysis oil is measured by its change in viscosity with time. The aging process can be accelerated by exposing the pyrolysis oil to high temperatures. The viscosity of the two pyrolysis oil samples has been determined using a rotational viscometer (as opposed to the traditional capillary viscometer). Samples were stored, with sealed lids, in an oven held at 90 degrees C for 0, 8 and 24 hours. At the completion of each time period, the viscosity of each sample was measured at 40 degrees C at various shear rates. No events or services have been held or performed as part of this project. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: This first task and most significant effort was originally intended to require only minor modifications to an existing fast pyrolysis test bed at the Iowa State University. As a result of changes at the university involving other funding commitments, ISU was no longer able to support our planned test program. ISU and Frontline agreed that the best course of action would be to build a second pyrolysis generator system at the BECON facility. Frontline's pyrolysis system includes a metering device to regulate the amount of feed to the reactor, an ablative-type-flash pyrolyzer, a methanol/water cooling injection point, a high temperature filter, and a condenser. Frontline has completed the design, fabrication and commissioning of the new test bed. Full operation was achieved in May 2008. The decision to build a new test bed put Frontline behind schedule, but we were able to improve certain aspects of the Py-Oil generator design to help facilitate integration of Frontline's Py-Oil vapor filtration equipment (as required by our Phase 1 work plan). Experience was gained in the operation of the pyrolysis system to date. Bottlenecks have been discovered in the process. The elimination of which, are anticipated to allow for higher throughputs and more reliable operation of the pyrolysis reactor.
Impacts
An initial determination of viscosity revealed that the sample obtained through high efficiency filtration (HEF) had a lower viscosity than the other sample (cyclone filtration only). Additionally, the HEF sample exhibited much greater stability (lower relative viscosity increase) than the cyclone filtered (CF) sample over an accelerated aging period of eight hours. Accelerated aging over a period of 24 hours, however, yielded an HEF sample that had multiple liquid phases, with some phase separation. For this reason it was not possible to get a representative viscosity measurement. It is probable that the container was not completely sealed and that a portion of the volatile components escaped during the aging period. These tests will be conducted anew once the filter has been more thoroughly seasoned. Traditionally, capillary viscometers are used in the determination of pyrolysis oil viscosity. Use of a rotational viscometer reveals that the pyrolysis oil is not Newtonian, as has been reported in the literature, and exhibits "shear thinning". Thus, the pyrolysis oil does not have a single value of viscosity at a given temperature as would be indicated by the use of a capillary viscometer. Experience was gained in the operation of the pyrolysis system to date. Bottlenecks have been discovered in the process. The elimination of which, are anticipated to allow for higher throughputs and more reliable operation of the pyrolysis reactor.
Publications
- No publications reported this period
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