Pyrolysis Of Bark Research Articles

Variations of the optical constants and size spectra of smoke aerosols produced during the thermal decomposition of different types of wooden materials

The directed light scattering coefficient β(ϑ j , λ j ) of smoke mixtures was measured at five scattering angles ϑ j = 15°, 45°, 110°, 135°, and 165° and at nine wavelengths in an interval of 440–690 nm within the framework of the smoke experiment conducted in the 1800-m3-volume Big Aerosol Chamber at the Institute of Atmospheric Optics using an automated polarized spectral nephelometer. The duration of the measurements was about 100 h. Based on the results of the spectral nephelometric measurements, the parameters of the microstructure and the complex refractive index were determined at three ranges of dispersity with the help of the improved method of the inversion of the aerosol light scattering characteristics. The specificity of the formation of the microstructure of a complex multicomponent dispersion mixture produced by the sequential mixing of pyrolysis products of different types of wooden materials is considered. The obtained estimates of the aerosol optical constants show that variations of the real n and imaginary χ parts of the complex refractive index (CRI) for coarse particles with r > 300 nm in the composition of the sequentially mixed smokes of pyrolysis are not as significant as for the fine fraction. In particular, for these particles, n varies in an interval of 1.58–1.62 and χ = 0.008–0.03, which characterizes them as weakly and moderately absorbing particles. The absorption of the particle’s finest fraction is sufficiently strong, varying in a wider interval of values: n = 1.78–2.20 and χ = 0.1–0.8. The moderate-sized particles (100 < r < 300 nm) have the real part of CRI primarily close to n ∼ 1.64 and χ ∼ 0.045 for coarse particles. Only for smoke generated during the pyrolysis of birch and aspen bark are these characteristics noticeably higher, approaching the estimates obtained for the fine fraction: n ∼ 1.80 and χ ∼ 0.20.

Effect of Alkali and Alkaline Earth Metallic Species on Biochar Reactivity and Syngas Compositions during Steam Gasification†

Biochars were prepared from the pyrolysis of the wood, leaf, and bark components of mallee biomass in a fixed-bed reactor at 750 °C. The results show that the volatilization of inherent alkali and alkaline earth metallic (AAEM) species is 10−20% during the pyrolysis of raw wood, bark, and leaf samples. Acid treatment of the biochar samples was also carried out to prepare a set of acid-treated biochar samples. Although the majority of the inherent AAEM species were removed by acid-treatment, there are always some AAEM species that could not be removed for all biochars. Steam gasification experiments of both the raw and acid-treated biochar samples were carried out in a fixed-bed reactor at 750 °C and a steam concentration of 8.2 vol %. Data on the instantaneous syngas composition were obtained as a function of biochar conversion during steam gasification. Our data illustrated the importance of, in the study of steam gasification reaction mechanisms and kinetics of solid fuels such as biochars, optimizing t...

Pyrolysis of Wood and Bark in an Auger Reactor: Physical Properties and Chemical Analysis of the Produced Bio-oils

Bio-oil was produced at 450 °C by fast pyrolysis in a continuous auger reactor. Four feed stocks were used: pine wood, pine bark, oak wood, and oak bark. After extensive characterization of the whole bio-oils and their pyrolytic lignin-rich ethyl acetate fractions by gas chromatography/mass spectrometry (GC/MS), gel permeation chromatography (GPC), calorific values, viscosity dependences on shear rates and temperatures, elemental analyses, 1H and 13C NMR spectroscopy, water analyses, and ash content, these bio-oils were shown to be comparable to bio-oils produced by fast pyrolysis in fluidized bed and vacuum pyrolysis processes. This finding suggests that portable auger reactors might be used to produce bio-oil at locations in forests to generate bio-oil on-site for transport of the less bulky bio-oil (versus raw biomass) to biorefineries or power generation units. The pyrolysis reported herein had lower heat transfer rates than those achieved in fluidized bed reactors, suggesting significant further improvements are possible.

Sorption of arsenic, cadmium, and lead by chars produced from fast pyrolysis of wood and bark during bio-oil production

Bio-char by-products from fast wood/bark pyrolyses, were investigated as adsorbents for the removal of the toxic metals (As 3+, Cd 2+, Pb 2+) from water. Oak bark, pine bark, oak wood, and pine wood chars were obtained from fast pyrolysis at 400 and 450 °C in an auger-fed reactor and characterized. A commercial activated carbon was also investigated for comparison. Chars were sieved (>600, 600–250, 250–177, 177–149, and <149 μm) and the particle size fraction from 600 to 250 μm was used without further modification for all studies unless otherwise stated. Sorption studies were performed at different temperatures, pHs, and solid to liquid ratios in the batch mode. Maximum adsorption occurred over a pH range 3–4 for arsenic and 4–5 for lead and cadmium. Kinetic studies yielded an optimum equilibrium time of 24 h with an adsorbent dose of 10 g/L and concentration ∼100 mg/L for lead and cadmium. Sorption isotherms studies were conducted in broad concentration ranges (1–1000 ppb for arsenic, 1 × 10 −5 – 5 × 10 −3 M for lead and cadmium). Oak bark out-performed the other chars and nearly mimicked Calgon F-400 adsorption for lead and cadmium. In an aqueous lead solution with initial concentration of 4.8 × 10 −4 M , both oak bark and Calgon F-400 (10 g/L) removed nearly 100% of the heavy metal. Oak bark (10 g/L) also removed about 70% of arsenic and 50% of cadmium from aqueous solutions. Varying temperatures (e.g., 5, 25, and 40 °C) were used to determine the effect of temperatures. The equilibrium data were modeled with the help of Langmuir and Freundlich equations. Overall, the data are well fitted with both the models, with a slight advantage for Langmuir model. The oak bark char's ability to remove Pb(II) and Cd(II) is remarkable when considered in terms of the amount of metal adsorbed per unit surface area (0.5157 mg/m 2 for Pb(II) and 0.213 mg/m 2 for Cd(II) versus that of commercial activated carbon.

Characterization of bio-oils in chemical families

Abstract This paper describes an analytical approach to determine the chemical composition of bio-oils in terms of macro-chemical families. Bio-oils from the vacuum pyrolysis of softwood bark and hardwood were first fractionated using solvent extraction. Fractions obtained were then characterized using GC-MS, thermogravimetric techniques (TG) and Gel Permeation Chromatography (GPC). Thermogravimetric and molar mass distribution curves of each fraction were interpreted in terms of macro-families applying curve-fitting procedures. The composition of the different macro-fractions obtained was in agreement using both methods. The proposed procedure enables a thorough description of bio-oil composition as a mixture of water, monolignols, polar compounds with moderate volatility, sugars, extractive-derived compounds, heavy polar and non-polar compounds, MeOH–toluene insolubles and volatile organic compounds.

Colloidal Properties of Bio-oils Obtained by Vacuum Pyrolysis of Softwood Bark: Aging and Thermal Stability

The objective of this study is to provide background information on pyrolysis oil for gas turbine applications. The bio-oil investigated consists of an upper layer and a bottom layer. It has been p...

Colloidal Properties of Bio-oils Obtained by Vacuum Pyrolysis of Softwood Bark. Characterization of Water-Soluble and Water-Insoluble Fractions

Crude bio-oils obtained via the pyrolysis of bark residues are dark, viscous, and sticky materials that visually appear similar to homogeneous liquids. However, microscopic tests revealed the presence of tridimensional compounds (agglomerates) and solid particles that are dispersed in the continuous bio-oil medium. These materials are responsible for the increase in bio-oil viscosity, the non-Newtonian flow behavior, the poor combustion properties, the corrosiveness, and the increase in the plugging frequency of the nozzles. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) tests, and rheology have been used to evaluate the colloidal properties of the bio-oils. The generic composition of the bio-oil, obtained by extracting water-insoluble materials (i.e., the lignin-derivative compounds), has been determined. The extraction produced a yield of lignin-derivative compounds of 29 wt %. The chemical composition of the water-soluble materials, as well as the molecular weight distributio...

Formation of HNCO, HCN, and NH 3 from the pyrolysis of bark and nitrogen-containing model compounds

Bark pellets have been pyrolyzed in a fluidized bed reactor at temperatures between 700 and 1000 °C. Identified nitrogen-containing species were hydrogen cyanide (HCN), ammonia (NH 3), and isocyanic acid (HNCO). Quantification of HCN and to some extent of NH 3 was unreliable at 700 and 800 °C due to low concentrations. HNCO could not be quantified with any accuracy at any temperature for bark, due to the low concentrations found. Since most of the nitrogen in biomass is bound in proteins, various protein-rich model compounds were pyrolyzed with the aim of finding features that are protein-specific, making conclusions regarding the model compounds applicable for biomass fuels in general. The model compounds used were a whey protein isolate, soya beans, yellow peas, and shea nut meal. The split between HCN and NH 3 depends on the compound and temperature. It was found that the HCN/NH 3 ratio is very sensitive to temperature and increases with increasing temperature for all compounds, including bark. Comparing the ratio for the different compounds at a fixed temperature, the ratio was found to decrease with decreasing release of volatile nitrogen. The temperature dependence implies that heating rate and thereby particle size affect the split between HCN and NH 3. For whey, soya beans, and yellow peas, HNCO was also quantified. It is suggested that most HCN and HNCO are produced from cracking of cyclic amides formed as primary pyrolysis products. The dependence of the HNCO/HCN ratio on the compound is fairly small, but the temperature dependence of the ratio is substantial, decreasing with increasing temperature. The release of nitrogen-containing species does not seem to be greatly affected by the other constituents of the fuel, and proteins appear to be suitable model compounds for the nitrogen in biomass.

Colloidal Properties of Bio-Oils Obtained by Vacuum Pyrolysis of Softwood Bark. Storage Stability

Bio-oil obtained via the vacuum pyrolysis of softwood bark residues is a multiphase, viscous, unstable system composed of water-soluble and water-insoluble fractions. Using centrifugation, the bio-oil can be separated into an upper layer (ca. 16 wt %) and a bottom layer (ca. 84 wt %). The upper layer exhibits low contents of water, solid, and ash, as well as a low density, a low acidity, a high content of methanol-insoluble materials, a high viscosity, and a high calorific value. The physicochemical properties of the bottom layer are similar to those of the whole bio-oil, except the bottom layer contains greater contents of ash and water. Microscopic analysis of the bio-oil has revealed a multiphase complex colloidal system that is composed of solid particles, three-dimensional structures, and droplets. The upper layer represents the dispersed droplet phase, which is rich in waxy materials (fatty and resin acids) and water-insoluble compounds. It is the upper layer that, overall, provides the unique collo...

Softwood Bark Pyrolysis Oil-PF Resols. Part 3. Use of Propylene Carbonate as Resin Cure Accelerator

Summary Phenol-formaldehyde (PF) resols were prepared with different proportions of phenol replaced with softwood bark pyrolysis oils under varying formaldehyde to phenolics molar ratios and sodium hydroxide contents. Propylene carbonate (PC) was added to these adhesives to improve the cure of resins. The cure behavior was characterized by differential scanning calorimetry (DSC). Cure kinetics and amount of cure of the experimental resin were improved by adding PC to the resins. Low amounts of PC were used (less than 1.5% of PC on a resin solid basis) to avoid premature gelling of the adhesives. Results obtained by DSC suggested that PC catalyzed the resin cure reaction and also participated in resin cross-linking reactions. Low percentages of PC, 0.5 and 1% on a resin solid basis, were added to the experimental resins for bonding strandboards. These addition levels did not significantly improve mechanical properties of strandboards. It is concluded that a PC addition level of more than 1% by wt (on a resin solid basis) should be used to modify the mechanical properties of panels bonded with pyrolysis oil-PF resins.

Softwood Bark Pyrolysis Oil-PF Resols. Part 2. Thermal Analysis by DSC and TG

Summary Cure behavior of resins formulated with petroleum phenol replaced by 25 and 50 wt% of softwood bark-derived pyrolysis oils, using various formaldehyde to phenolics molar ratios and alkalinity content, was characterized by Differential Scanning Calorimetry (DSC). Kinetic parameters were obtained by the Borchart-Daniels method and the model-free (Vyazovkin) method. Resins containing up to 50% by wt of pyrolysis oils had slower cure kinetics and lower extent of condensation reaction compared to a neat laboratory made phenol-formaldehyde resin. However, very similar kinetic curing behavior to the standard resins was found for resols having 25% by wt of the petroleum phenol replaced by the pyrolysis oils. Thermogravimetric analysis (TG) of cured pyrolysis oil-PF resins has been done under nitrogen and air environments at a constant heating rate. Thermal behavior of resins containing pyrolysis oils differed depending on the nature of the purge gas used in TG. Increasing the amount of pyrolysis oils decreased the thermal resistance of the experimental resins.

Softwood Bark Pyrolysis Oil-PF Resols. Part 1. Resin Synthesis and OSB Mechanical Properties

Summary Bark residues generated by the pulp and paper and wood industries represent a threat to the environment due to leaching of chemicals such as phenolics and resin acids which are being currently regulated by governments. Vacuum pyrolysis of resinous bark produces phenolic-rich oils which represent a potential raw material to replace petroleum-based phenol presently used in the formulation of wood adhesive resols. Resols with different levels of phenol replacement by phenolic pyrolysis oils, formaldehyde to phenolics molar ratios and sodium hydroxide to phenolics molar ratios were synthesized. Strandboards werepreparedandtheirmechanicalandphysicalpropertiessuchasmodulusofrupture(MOR),modulus of elasticity (MOE), dry and 2-hour boil internal bond (IB) and thickness swelling (TS) were evaluated. Homogeneous panels bonded with resins having 25 and 50% by wt of pyrolysis oils replacing phenol exhibited comparable mechanical properties to those of panels made with a commercial surface resin under the same pressing conditions. Three-layer panels made with resins having 50 % by wt phenol replacement in the surface and 25% by wt phenol replacement in the core had mechanical properties above the requirements specified by the Canadian Standards CSAO437.0-93 for OSB products.

Bio-oils obtained by vacuum pyrolysis of softwood bark as a liquid fuel for gas turbines. Part II: Stability and ageing of bio-oil and its blends with methanol and a pyrolytic aqueous phase

This paper completes a study the ultimate objective of which was to provide background information on biomass pyrolysis oils (bio-oils) regarding their use as a gas turbine liquid fuel. The bio-oil was obtained by vacuum pyrolysis of softwood bark residues. The stability and ageing of the bio-oil and mixtures thereof were evaluated. The samples were stored at 40, 50 and 80°C for up to 168 h and at room temperature for up to one year, period after which the phase separation time, viscosity, solid and water content and average molecular weight were measured. The results indicated that the properties of the bio-oil were significantly altered when the bio-oil was heated at 80°C, but that the variations after heating at 40 and 50°C were not critical. It was found that the molecular weight increase after heating the bio-oil for one week at 80°C was equivalent to keeping the sample for one year at room temperature. The addition of aqueous phase to the bio-oil lowered its thermal stability significantly. A rapid phase separation occurred after heating at 80°C and, therefore, the total aqueous phase concentration in the bio-oil must be limited to 15%. Ageing of the raw bio-oil at room temperature resulted in a dramatic viscosity increase during the first 65 days, period after which a plateau was reached. The addition of methanol to the bio-oil was beneficial for the bio-oil properties as well as for the stability of the bio-oil and its mixtures. Methanol dissolved some structured components of the bio-oil and thus reduced the viscosity increase rate. Moreover, the addition of methanol to the bio-oil/pyrolytic aqueous phase mixtures delayed the phase separation process.

Bio-oils obtained by vacuum pyrolysis of softwood bark as a liquid fuel for gas turbines. Part I: Properties of bio-oil and its blends with methanol and a pyrolytic aqueous phase

The objective of this study was to provide background information on biomass pyrolysis oils (bio-oils) regarding their use as a liquid fuel for gas turbine applications. The bio-oil was obtained by vacuum pyrolysis of softwood bark residues. Alkali metal content, viscosity, solid content, heating value, surface tension, moisture content and density of the bio-oil were investigated. The effect of the addition of methanol and/or a pyrolytic aqueous phase on the physicochemical properties of the bio-oils was also investigated. The pyrolytic aqueous phase is the sum of the water contained in form of moisture in the feedstock plus the water formed during biomass pyrolysis reactions. The results indicated that the bio-oil sample investigated is a valuable gas turbine fuel: it has a relatively low Na+K+Ca content (21 ppm), a low viscosity ( 5.3 cSt@90° C ), a high net heating value (32 MJ/kg, as-received basis) and a low solid content (0.34 wt%). The addition of methanol to the oil was beneficial. It was also found that the pyrolytic aqueous phase addition had no significant effect on the viscosity, but that its “flowability” effect was beneficial for other properties. A concentration of 10–15% of the aqueous phase in the bio-oil seemed to be optimal. The second phase of this study investigated the storage and thermal stability of bio-oils and their mixtures. This was carried out using a method performed in our laboratory. The results are presented in Part II of this study.

Surface and bulk chemistry of charcoal obtained by vacuum pyrolysis of bark: influence of feedstock moisture content

Samples of maple bark and softwood bark with moisture contents ranging from 6 to 42 wt% were pyrolyzed under vacuum at a temperature of 775 K. Vacuum pyrolysis of maple bark yields approximately 30 wt% wood charcoal on an anhydrous basis. For softwood bark the charcoal yield is smaller (23–28 wt%). The charcoal yield of maple bark pyrolysis depended only slightly on the bark moisture. The surface and bulk chemistry development of the charcoals was studied by electron spectroscopy for chemical analysis (ESCA), secondary ion mass spectroscopy (SIMS) and Raman spectroscopy, respectively. With decreasing bark moisture the charcoal surface becomes more graphite-like, whereas the bark moisture had only a limited influence on the bulk structure. The high specific surface area of the charcoals at 200–300 m 2/g makes these materials valuable feedstocks for the production of activated carbons.

96/05555 The issue of indoor air quality. The AGA position

Microwave-assisted pyrolysis (MAP) of lignocellulosic biomass is a technique that could potentially be used to produce and upgrade renewable energy carriers. However, there is no available information about the formation of dioxins and other organic pollutants in MAP treatment of woody biomass. In this study, MAP experiments were conducted in lab-scale using virgin softwood, bark, and impregnated wood as feedstocks. The non-condensable gas, liquid (fractionated into aqueous and oil phases), and char fractions generated during pyrolysis were collected and analysed for polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and naphthalenes (PCNs). The concentrations of PCDDs, PCDFs and PCNs in the pyrolysis products ranged from 0.52 to 43.7 ng kg−1. All investigated compound groups were most abundant in the oil fraction, accounting for up to 68% (w/w) of the total concentrations. The highest PCDD, PCDF and PCN concentrations were found from the pyrolysis of bark, which has relatively high contents of chlorine and mineral matter, followed by impregnated wood, which contains organic and metal-based preservatives. The homologue profiles of all three compound groups were dominated by the less chlorinated homologues. The homologue abundance decreased as the degree of chlorination increased. This trend was observed for all three feedstocks.

96/05553 Institutions for global environmental change. The US President's Council on Sustainable Development

Microwave-assisted pyrolysis (MAP) of lignocellulosic biomass is a technique that could potentially be used to produce and upgrade renewable energy carriers. However, there is no available information about the formation of dioxins and other organic pollutants in MAP treatment of woody biomass. In this study, MAP experiments were conducted in lab-scale using virgin softwood, bark, and impregnated wood as feedstocks. The non-condensable gas, liquid (fractionated into aqueous and oil phases), and char fractions generated during pyrolysis were collected and analysed for polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and naphthalenes (PCNs). The concentrations of PCDDs, PCDFs and PCNs in the pyrolysis products ranged from 0.52 to 43.7 ng kg−1. All investigated compound groups were most abundant in the oil fraction, accounting for up to 68% (w/w) of the total concentrations. The highest PCDD, PCDF and PCN concentrations were found from the pyrolysis of bark, which has relatively high contents of chlorine and mineral matter, followed by impregnated wood, which contains organic and metal-based preservatives. The homologue profiles of all three compound groups were dominated by the less chlorinated homologues. The homologue abundance decreased as the degree of chlorination increased. This trend was observed for all three feedstocks.

95/06523 Formation of NH 3 and HCN in slow-heating-rate inert pyrolysis of peat, coal and bark

95/06523 Formation of NH 3 and HCN in slow-heating-rate inert pyrolysis of peat, coal and bark

Formation of NH 3 and HCN in slow-heating-rate inert pyrolysis of peat, coal and bark

In gasification processes, nitrogen compounds are formed in the gas. There are very few data available on the conversion of fuel nitrogen to nitrogen compounds in pyrolysis conditions that simulate fixed-bed or fluidized-bed gasification or other fuels than coal. In this study, relatively large fuel pieces of peats, bark and coal were pyrolysed in an inert gas atmosphere at a slow heating rate. All fuels produced more NH 3 than HCN. The conversion of fuel nitrogen to NH 3 ranged from 17 to 24 wt% for peat, 10 to 12 wt% for bark and 15 to 17 wt% for coal. The conversion of fuel nitrogen to HCN was 5–11 wt% for coals and considerably less for the other fuels. Increasing the tar cracking can increase the HCN conversion and NH 3 conversion in peat pyrolysis. The pyrolysis of fuel pieces seems to produce the NH 3 and HCN observed in the fixed-bed gasifiers.

Products from the flash pyrolysis of peat and pine bark

Dry powders prepared from fuel-grade medium-decomposed Carex peat and from bark of Scots pine ( Pinus sylvestris) were pyrolyzed in a continuous bench-scale fluidized-bed reactor over a temperature range of 400–800° C. Gas-phase residence time within the heated zone was about 0.5 s. In addition to the determination of the yields of major product groups, the organic liquid products were separated and identified by gas chromatography/mass spectrometry and characterized by infrared spectroscopy and gel permeation chromatography. The highest yields of organic liquids, more than 50 wt% of bark organic matter and over 40 wt% of peat organics were obtained at 500° C. The yields of liquid products decreased at 600° C because of thermal secondary reactions, and the yields of gaseous products, such as CO, C 2H 4, CH 4 and H 2 increased correspondingly. At the highest temperature nearly 60 wt% of peat and nearly 50 wt% of bark were degraded to gaseous products. The proportion of organic liquids analyzed by gas chromatography was, in all cases, less than 30 wt%. Even so, significant changes in chemical structures were detected. According to the gel permeation chromatography results, the liquid products formed at 800° C still contained high-molecular-weight substances. On the other hand, the high-temperature liquid products were, overall, of lower molecular weight than those obtained at lower temperatures. The results can be utilized in the development of thermochemical conversion processes based on flash pyrolysis. In addition, they can be applied in basic research on gasification and combustion at high-heating rates.