Liquid transportation fuel blendstocks were produced by pyrolysis and catalytic upgrading of woody residue biomass. Mountain-pine-beetle-killed (MPBK) wood and hog fuel from a saw mill were pyrolyzed in a 1 kg/h fluidized bed reactor and, subsequently, upgraded to hydrocarbons in a continuous fixed bed hydrotreater. Upgrading was performed by catalytic hydrotreatment in a two-stage bed at 170 and 405 °C with a per bed liquid hourly space velocity between 0.17 and 0.19. The overall yields from biomass to upgraded fuel were similar for both feeds (24–25%), despite the differences in bio-oil (intermediate) mass yield. The pyrolysis bio-oil mass yield was 61% from MPBK wood, and subsequent upgrading of the bio-oil gave an average mass yield of 41% to liquid fuel blend stocks. Hydrogen was consumed at an average of 0.042 g/g of bio-oil fed, with a final oxygen content in the product fuel ranging from 0.3 to 1.6% over the course of the test. Comparatively, for hog fuel, the pyrolysis bio-oil mass yield was lower at 54% because of inorganics in the biomass, but subsequent upgrading of that bio-oil had an average mass yield of 45% to liquid fuel, resulting in a similar final mass yield to fuel compared to the cleaner MPBK wood. Hydrogen consumption for the hog fuel upgrading averaged 0.041 g/g of bio-oil fed, and the final oxygen content of the product fuel ranged from 0.09 to 2.4% over the run. While it was confirmed that inorganic-laden biomass yields less bio-oil, this work demonstrated that the resultant bio-oil can be upgraded to hydrocarbons at a higher yield than bio-oil from clean wood. Thus, the final hydrocarbon yield from clean or residue biomass pyrolysis/upgrading was similar.
New regulations implemented by the Canadian federal government to limit greenhouse gas (GHG) emissions from coal burning power plants had sparked intense activity in the utility industry to find ways to reduce emissions. Several studies have indicated that carbon capture and storage (CCS) is not going to be economically available in the short term. Co-firing biomass appears to be an option for many of the coal-fired power plants, as Canada has a significant amount of biomass resources. Although biomass combustion can reduce greenhouse gas emissions, it can also generate other air pollutants. To determine emission factors for co-firing biomass and coal, pilot-scale tests were performed. These tests were conducted in CanmetENERGY's 0.5 MWth pilot-scale pulverized fuel research furnace, which was configured with a dual-burner system, electrostatic precipitator, and baghouse. Gaseous emissions were recorded with two monitoring systems, and traditional methods for batch sampling of halogens, mercury, and particulate matter were implemented. Emission factors were developed for a 100% coal baseline, for two co-firing ratios of 20% and 55% biomass by heating value and biomass-only firing.
The ash deposition behaviors of co-combustion of three-fuel blends of white pine pellet (WPP), peat pellet (PP), and crushed lignite (CL) coal were studied on a pilot-scale bubbling fluidized-bed combustor operated at 40% excess air ratio. Reference tests with individual fuel (pine, peat, or lignite) and two-fuel blends of lignite and pine or peat were also performed and discussed in this study. Fly ash deposits were collected with an air-cooled probe installed in the freeboard zone of the reactor. The collected deposits were comprehensively characterized by X-ray fluorescence (XRF), X-ray powder diffraction (XRD), ion chromatography (IC), and scanning electron microscopy (SEM) for their chemical compositions, mineralogical compositions, Cl/S concentrations, and morphology, respectively. As a very interesting finding from this work, co-combustion of the three-fuel blends at 50% lignite/25% peat/25% pine resulted in a higher ash deposition rate than co-combustion of two-fuel blends of either 50% lignite/50% peat or 50% lignite/50% pine. In contrast, co-combustion of three-fuel blends at 20% lignite/40% peat/40% pine resulted in the lowest deposition rate and the least deposition tendency among all of the combustion tests with various mixed fuels or individual fuels. The greatly decreased ash deposition tendency of co-firing three-fuel blends of 20% lignite/40% peat/40% pine might be accounted for by the formation of more minerals containing CaO, MgO, Al2O3, and SiO2 with high ash melting points and high crystallinity. The chemical compositions of deposits obtained from the co-combustions of three-fuel blends were apparently enriched with the elements Si and Al and depleted of the elements P, S, and K.
A round robin study evaluating the analysis of biomass liquefaction oils (BLOs) from fast pyrolysis and hydrothermal liquefaction (HTL) was performed, receiving data from 14 laboratories in seven countries in order to assess the current status of analytical techniques for the determination of nitrogen, sulfur, and chlorine content in BLOs and to evaluate potential differences in origin (i.e., fast pyrolysis versus HTL). The BLOs were produced from a range of feedstocks including pine, mixed softwoods, forest residues, microalgae, miscanthus, and wheat straw to cover a variety in nitrogen, sulfur, and chlorine content and speciation. Nine samples were distributed, comprised of eight separate BLOs and one blind duplicate produced by five producers. The samples were analyzed for water, carbon, hydrogen, nitrogen, sulfur, and chlorine content. No analytical test method was mandated; laboratories were encouraged to utilize whichever method they determined would be most applicable, relying on the existing body of BLO literature as a guide. The results of this round robin study are presented in this paper. The results of the carbon, hydrogen, and water measurements as reference analyses had relative standard deviations (2.9, 3.5, and 5.6%, respectively) that were comparable to those found in past round robin studies on fast pyrolysis bio-oil. The analysis of nitrogen, sulfur, and chlorine showed higher levels of variability. Laboratories mostly chose the same method for water, carbon, hydrogen, and nitrogen determination, whereas there were a variety of methods chosen for sulfur and chlorine determination. The results suggest that specific analytical methods for the determination of nitrogen, sulfur, and chlorine should be further refined to ensure reproducible and accurate results for BLO analysis due to their importance in emissions, material selection, and catalyst activity.
Experiments have been done subjecting ashes from industrial-scale FBC boilers to sulphating conditions in an oven for up to 105 days. These show that sulphation by itself causes agglomeration in the virtual absence of V, K, and Na, the elements normally associated with ash softening and classical fouling. In addition, it has been demonstrated that sulphation goes to completion over long periods of time and, at a specific level which differs from one ash to another, results in agglomeration. These experiments have also shown that there is a size range (75–300 μm) in which the agglomeration is worst, and particles that are smaller or larger either do not agglomerate or agglomerate more weakly. Added “inert” coal-derived ash decreases or prevents the agglomeration. However, this ash does not appear to chemically combine with the sulphate, but acts by mechanically separating the sulphating particles. Finally, if alkali metals are present they can cause agglomeration at levels lower than those at which either the alkalis or sulphation separately cause agglomeration, i.e., they operate synergistically to cause fouling. Current work is being directed at examining these phenomena at higher temperatures (900°C and above).
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