Pyrolysis In Fluidized Bed Reactor Research Articles

Modeling effects of interphase transport coefficients on biomass pyrolysis in fluidized beds

This study numerically characterizes the effects of interphase transport coefficients on the simulation of biomass pyrolysis in fluidized-bed reactors. Numerical modeling of sub-grid structures can affect the evolution of interphase transport coefficients and influence the predictive capability of coarse-grid computational fluid dynamics (CFD) models in simulating fluidized-bed reactors. In this study, a multi-fluid model that solves mass, momentum, energy and species conservations was coupled with chemical reactions to simulate a laboratory-scale biomass fast pyrolysis reactor. Different formulations of drag and heat transfer coefficients were employed. Comparisons between the simulated and experimental results show that the drag coefficient model considering detailed sub-grid structures predicted lower drag forces and performed better than the homogeneity-based drag correlation models. Lower drag forces on solid biomass particles resulted in lower solid biomass outflux, higher gas velocities, and shorter tar residence time, all resulting in higher tar yields. On the other hand, heat transfer correlations had less effect on the temperature distributions and final product yields. These findings indicate that when coarse-grid CFD is used to simulate biomass fast pyrolysis in fluidized-bed reactors, effects of sub-grid structures need to be taken into account in the formulations of drag coefficients.

Effect of the Fast Pyrolysis Temperature on the Primary and Secondary Products of Lignin

This paper presents results on the primary pyrolysis products of organosolv lignin at temperatures between 360 and 700 °C. To study the primary products, a vacuum screen heater (heating rate of 8000 °C/s, deep vacuum of 0.7 mbar, and very fast cooling at the wall temperature of −100 °C) was used. The effect of the temperature on the primary and secondary lignin products was studied with a fluidized-bed pyrolysis reactor (Treactor between 330 and 580 °C) with pine wood. The results obtained with the screen heater show that the primary products of lignin were oligomers. Between 450 and 700 °C, the yield of these oligomers was very high, between 80 and 90%. After formation, the oligomers left the particle by evaporation or thermal ejection. Monophenols and other light compounds were formed by secondary reactions inside the particle or in the vapor phase. In the fluidized-bed reactor, significant quantities of lignin oligomers were formed along with monophenols, water, and other light compounds. The changes o...

Development of a generalized numerical framework for simulating biomass fast pyrolysis in fluidized-bed reactors

A numerical framework for simulating biomass fast pyrolysis is developed in this study. Fast pyrolysis, a thermochemical conversion process converting low-value lingo-cellulosic biomass to various useful products has gained increased interest. This study is to develop an open-source computational tool to help understand the complex phenomena involved within the biomass fast pyrolysis process. In this framework, a multi-fluid model is applied to simulate the multi-phase hydrodynamics while global reaction kinetics is used to describe the physicochemical conversion. The coupling of these two methodologies is realized by a time-splitting method. The model results are validated using experimental data from fast pyrolysis reactors. Good levels of agreement are obtained in the product distribution including tar, biochar, and syngas. The parametric study also indicates that the tar yield can be increased if the biomass injector location is elevated or the superficial velocity of the feeding nitrogen is increased. One feature of the present numerical framework is that sub-models for different constitutive hydrodynamic relations and chemical reactions can be readily incorporated into this framework owing to the object-oriented feature of the baseline code.

Effect of Operating Conditions and Fractional Condensation on Pyrolytic Products

The effects of biomass type, size, and pyrolysis temperature on pyrolytic products distribution have been investigated. Hence, reaction temperatures (400, 450, 500, and 550 °C) and biomass feedstock sizes (0.15-0.5, 0.5-1.0, and 1.0-2.0 mm) were applied. Decomposition of palm kernel shell and mesocarp fiber was performed in a fluidized bed pyrolyzer with nitrogen gas flow rate of 25 L(NTP)/min. The maximum bio-oil yield (39.6 %) was gained from PKS of 0.15-0.5 mm at 500 °C. Many evidence showed that small particle size produced the most noticeable amount of bio-oil production. The fluidized bed pyrolysis reactor used possesses six successive condensers operated at three temperatures. Thus, six fractions of bio-oil samples were obtained from these six condensers. The properties of each bio-oil sample were determined including calorific value, elements, water and ash contents, and major compounds in the bio-oils. The compositions of water and major compounds in the fractional liquids of these six successive condensers were also reported.

Experimental validation and CFD modeling study of biomass fast pyrolysis in fluidized-bed reactors

In this work, an Euler–Euler multiphase computational fluid dynamics (CFD) model, which couples a biomass particle pyrolysis model with a multi-fluid hydrodynamics model for gas–particle flow, is used to describe a biomass pyrolysis process, and model predictions are compared to experimental data produced in a lab-scale fluidized-bed reactor. A parametric study of operating conditions was also performed. The kinetic model is based on superimposed hemicellulose, cellulose, and lignin reactions. General biomass feedstock can be represented through the initial mass composition with respect to the three components. The gas–particle flow is modeled with a multi-fluid description (gas, sand, biomass) derived from the kinetic theory of granular flows. The predicted product yields at the reactor outlet are presented and compared with the experimental measurements for both pure cellulose and red oak pyrolysis, and encouraging quantitative agreement is achieved. The model is then applied to investigate the effect of various operating conditions on the pyrolysis product yields in the reactor. Results indicate that biomass particle size and superficial gas velocity influence tar yield and residence time considerably with a fixed bed height. For the range of operating temperature studied, the model captures the trend of biomass decomposition versus temperature and shows an optimal temperature of about 500°C for bio-oil production as reported in the literature. Different biomass feedstocks are also simulated and model shortcomings are discussed.

Bio-oil Production from Empty Fruit Bunch of Palm Using a Fluidized Bed Pyrolysis Reactor

Bio-oil Production from Empty Fruit Bunch of Palm Using a Fluidized Bed Pyrolysis Reactor

Fluid catalytic cracking of biomass pyrolysis vapors

Catalytic cracking of pyrolysis oils/vapors offers the opportunity of producing bio-oils which can potentially be coprocessed with petroleum feedstocks in today’s oil refinery to produce transportation fuel and chemicals. Catalyst properties and process conditions are critical in producing and maximizing desired product. In our studies, catalyst matrix (kaolin) and two commercial fluid catalytic cracking (FCC) catalysts, FCC-H and FCC-L, with different Y-zeolite contents were investigated. The catalytic cracking of hybrid poplar wood was conducted in a 50-mm bench-scale bubbling fluidized-bed pyrolysis reactor at 465°C with a weight hourly space velocity of 1.5 h−1. The results showed that the yields and quality of the bio-oils was a function of the Y-zeolite content of the catalyst. The char/coke yield was highest for the higher Y-zeolite catalyst. The organic liquid yields decreased inversely with increase in zeolite content of the catalyst whereas the water and gas yields increased. Analysis of the oils by both Fourier-transform infrared and 13C-nuclear magnetic resonance indicated that the catalyst with higher zeolite content (FCC-H) was efficient in the removal of compounds like levoglucosan, carboxylic acids and the conversion of methoxylated phenols to substituted phenols and benzenediols. The cracking of pyrolysis products by kaolin suggests that the activity of the FCC catalyst on biomass pyrolysis vapors can be attributed to both Y-zeolite and matrix. The FCC-H catalyst produced much more improved oil. The oil was low in oxygen (22.67 wt.%), high in energy (29.79 MJ/kg) and relatively stable over a 12-month storage period.

Fractional Condensation of Biomass Pyrolysis Vapors

In this paper, we have investigated the possibilities to steer the composition and, thus, the quality of pyrolysis liquids by the reactor temperature and the pyrolysis vapor condenser temperature. Pine wood was pyrolyzed in a 1 kg/h fluidized-bed pyrolysis reactor operated at 330 or 480 °C. The pyrolysis vapors produced were condensed using a condenser train of two counter-current spray columns arranged in series. In this paper, the temperature of the first condenser was varied between 20 and 115 °C, while the second condenser temperature was kept at 20 °C. To describe the composition of the oils, we have integrated several analytical techniques into a novel characterization scheme that can account for 77−82 wt % of the oils. The effects of the condensation conditions on fractions of light compounds in the oils can be predicted with a simple equilibrium stage condensation model. It has been observed that pyrolysis at 330 °C gives a light oil with a low amount of mid-boilers [normal boiling point (nbp) of 150−300 °C] and heavy compounds (water insolubles and mono- and oligosugars). Sugars, mid-boilers, and water-insoluble lignin-derived oligomers are more present in the oil obtained at 480 °C, while the yields of light organics are approximately the same for 330 and 480 °C. It can be concluded that fractional condensation is a promising cheap downstream approach to concentrate compounds (classes) and, thus, to control the quality of pyrolysis oils. For instance, operating the first condenser around 70−90 °C gives an aqueous liquid in the second condenser containing 40 wt % light organics, which are interesting for extraction (e.g., 10 wt % acetic acid) and supercritical water gasification to produce hydrogen. Under these conditions, the oils from the first condenser have a high content of sugars (20 wt %) and lignin-derived oligomers (40 wt %), which are attractive fractions for fermentation/sugar chemistry and gasoline production via fluidized catalytic cracking (FCC)/hydrotreatment, respectively.

Simultaneous catalytic esterification of carboxylic acids and acetalisation of aldehydes in a fast pyrolysis bio-oil from mallee biomass

This paper reports the simultaneous catalytic esterification and acetalisation of a bio-oil with methanol using a commercial Amberlyst-70 catalyst at temperatures between 70 and 170 °C. The bio-oil was prepared from the pyrolysis of mallee woody biomass in a fluidised-bed pyrolysis reactor under the fast heating rate conditions. Our results show that the conversion of light organic acids and aldehydes to esters and acetals rises significantly with increasing temperature, reaction time and catalysts loading. However, some acetals (e.g. dimethoxymethane) could decompose at higher operating temperatures (>110 °C) and catalyst loadings (>6 wt.%). The medium and heavy fractions of bio-oil also reacted with methanol to result in increases in their volatility (or decreases in boiling points) when their reactive O-containing functional groups were stabilised. The acid-catalysed reactions between bio-oil and methanol also decreased the coking propensity of the bio-oil reaction products.

A CFD model for biomass fast pyrolysis in fluidized-bed reactors

In this work, an Euler–Euler multiphase CFD model is proposed for continuous fast pyrolysis of biomass in a fluidized-bed reactor. In the model, a lumped, multi-component, multi-stage kinetic model is applied to describe the pyrolysis of a biomass particle. Variable particle porosity is used to account for the evolution of the particle's physical properties. Biomass is modeled as a composite of three reference components: cellulose, hemicellulose, and lignin. Pyrolysis products are categorized into three groups: gas, tar vapor (bio-oil), and solid char. The particle kinetic processes and their interactions with the reactive gas phase are modeled with a multi-fluid description derived from the kinetic theory of granular flows. A time-splitting approach is applied to decouple the convection and reaction calculations using a synchronized time step. The CFD model is employed to study the fast pyrolysis of both cellulose and bagasse in a lab-scale fluidized-bed reactor. The dynamics, particle heating, reaction of the biomass phase, char formation, elutriation, and spatial distribution of tar and gas inside the reactor are investigated. The yields of tar, gas, and char are also discussed.

Characterization of rice husks and the products of its thermal degradation in air or nitrogen atmosphere

Rice husk is a by-product of rice milling process and are a major waste product of the agricultural industry. They have now become a great source as a raw biomass material for manufacturing value-added silicon composite products, including silicon carbide, silicon nitride, silicon tetrachloride, pure silicon, zeolite, fillers of rubber and plastic composites, adsorbent and support of catalysts. The bulk and true densities of raw rice husk with different moisture and sizes were determined. The rice husk was subjected to pyrolysis in fluidized-bed reactor in air or nitrogen atmosphere.

05/01203 A model of wood flash pyrolysis in fluidized bed reactor

05/01203 A model of wood flash pyrolysis in fluidized bed reactor

A model of wood flash pyrolysis in fluidized bed reactor

With a view of exploiting renewable biomass energy as a highly efficient and clean energy, liquid fuel from biomass pyrolysis, called bio-oil, is expected to play a major role in future energy supply. At present, fluidized bed technology appears to have maximum potential in producing high-quality bio-oil. A model of wood pyrolysis in a fluidized bed reactor has been developed. The effect of main operation parameters on wood pyrolysis product distribution was well simulated. The model shows that reaction temperature plays a major important role in wood pyrolysis. And a good agreement between experimental and theoretical results was obtained. It was shown that particles less than 500 μm could achieve a high heating-up rate to meet flash pyrolysis demand.

Product Composition from the Fast Pyrolysis of Polystyrene

Polystyrene has been pyrolysed in a fluidised bed pyrolysis reactor and the influence of pyrolysis temperature from 500 to 700°C on the yield and composition of the derived products has been determined. The main products from pyrolysis of polystyrene were a wax/oil product collected, as a condensed wax fraction and a separate oil fraction, using an industrial demister system. The oils and waxes were analysed by size exclusion chromatography to determine their molecular weight distribution, by Fourier transform infra-red spectrometry to determine their functional group composition and by gas chromatography to determine their detailed composition. The derived oils had a molecular weight distribution from 60 to 200 Da, with higher molecular weight material occurring in the wax fraction with a distribution of 60 to over 1000. Detailed analysis of the oils showed that the pyrolysis of polystyrene gave a mainly aromatic composition dominated by styrene and styrene oligomers. The oils also contained polycyclic aromatic hydrocarbons which increased in concentration as the pyrolysis temperature was increased to 700°C. Low concentrations of hydrogen, methane, ethane, ethene, propane, propene, butane and butene were also formed. There was an increase in gas yield with increasing temperature of pyrolysis.

Fluidization of Scrap-Wood Materials: The Influence of the Degree of Thermal Decomposition on the Hydrodynamic Properties

This work focuses on the hydrodynamics of fluidizing scrap-wood particles from five different sources. The objective of this study is to carry out the analysis of the hydrodynamic properties of these particles (size, density, shape factor, and specific surface) when submitted to the same thermal decomposition that takes places in a fluidized-bed pyrolysis reactor. Correlations to describe the change of some properties with the treatment temperature are proposed.

Application of microscopy to the investigation of brown coal pyrolysis

To examine the influence of calcium on the mechanisms of brown coal pyrolysis and gasification, the morphology of chars from raw and calcium-exchanged Yallourn brown coal was analysed. The chars were obtained by slow pyrolysis in a thermo gravimetric analyser and rapid pyrolysis in fluidized bed reactors operating at atmospheric pressure and at 1.1 MPa. They were examined by optical microscopy to determine reflectance and the percentage of particles that had become plastic during pyrolysis. In addition to confirming calcium's inhibiting effect on tar yield, the results from the rapid pyrolysis experiments show that in the presence of calcium, char reflectivity decreases, char H/C ratio increases, and the proportion of particles going through a plastic stage decreases. Calcium's inhibition of plasticity development is augmented by high pressure in the fluidized bed reactor. The effects appear to be attributable to the action of carboxylate calcium as a cross-linking agent, leading to the formation of a tighter char structure which traps the organic material that would otherwise be liberated as tar. The presence of Ca also increases the H/C ratio of the chars produced by slow pyrolysis, but the mechanism of pyrolysis differs, since in slow pyrolysis none of the particles showed evidence of plasticity. In slow pyrolysis, calcium's influence on char reflectivity depends on the holding temperature, since temperature determines the extents of both coal devolatilization and catalytic transformations. The roles of calcium in these processes and their influence on optical anisotropy and reflectance are discussed.

Premium quality fuels and chemicals from the fluidised bed pyrolysis of biomass with zeolite catalyst upgrading

Biomass in the form of pine wood was pyrolysed in an externally heated fluidised bed pyrolysis reactor with nitrogen as the fluidising gas. A section of the freeboard of the reactor was packed with zeolite ZSM-5 catalyst. The pyrolysis oils before and after catalysis were collected in a series of condensers and cold traps. In addition, gases were analysed off-line by packed column gas chromatography. The composition of the oils and gases were determined before and after catalysis in relation to process conditions. The oils were analysed by liquid chromatography followed by gas chromatography/mass spectrometry. The results showed that the oils before catalysis were highly oxygenated, after catalysis the oils were markedly reduced in oxygenated species with an increase in aromatic species, producing a premium grade gasoline type fuel. The gases were CO 2, CO, H 2, CH 4, C 2H 4 and C 3H 6 and minor concentrations of other hydrocarbon gases. After catalysis the concentration of CO 2 and CO were increased. Detailed analysis of the upgraded oils showed that there were high concentrations of economically valuable chemicals. However, biologically active polycyclic aromatic species were also present in the catalysed oil, which increased with increasing catalyst temperature.

Characterisation of oils from the fluidised bed pyrolysis of biomass with zeolite catalyst upgrading

Biomass in the form of pine wood was pyrolysed in an externally heated 7.5 cm diameter, 100 cm high fluidised bed pyrolysis reactor with nitrogen as the fluidising gas. A section of the freeboard of the reactor was packed with zeolite ZSM-5 catalyst. The pyrolysis oils before and after catalysis were collected in a series of condensers and cold traps. In addition, gases were analysed off-line by packed column gas chromatography. The compositions of the oils and gases were determined in relation to the primary fluidised bed and after catalysis at increasing catalyst bed temperatures from 400° to 550°C. The oils were analysed by a number of techniques to determine composition, including liquid chromatography, gas chromatography/mass spectrometry. Fourier transform infrared spectroscopy and size exclusion chromatography. The results showed that the oils before catalysis were highly oxygenated; after catalysis the oils were markedly reduced in oxygenated species with an increase in aromatic and polycyclic aromatic species. The gases evolved from the fluidised bed pyrolysis of biomass were CO2, CO, H2, CH4, C2H4, C3H6 and minor concentrations of other hydrocarbon gases. After catalysis the concentrations of CO2 and CO were increased. The conversion of oxygenated compounds was mainly to H2O at lower catalyst temperatures and CO2 and CO at high catalyst temperatures. Detailed analysis of the oils showed that there were high concentrations of biologically active polycyclic aromatic species in the catalysed oil which increased with increasing catalyst temperature. The oxygenated compounds in the uncatalysed oil were mainly phenols and car☐ylic acids. After catalysis these decreased in concentration with increasing catalyst temperature

Hydrotreating the bitumen-derived hydrocarbon liquid produced in a fluidized-bed pyrolysis reactor

The pyrolysis of bitumen-impregnated sandstone produces three primary product streams: C 1C 4 hydrocarbon gases, a C 5 + total liquid product, and a carbonaceous residue on the spent sand. The bitumen-derived hydrocarbon liquid was significantly upgraded relative to the native bitumen: it had a higher API gravity, lower Conradson carbon residue, asphaltene content, pour point and viscosity, and a reduced distillation endpoint relative to the native bitumen. The elemental composition was little different from that of the native bitumen except for the hydrogen content, which was lower. Thus, integration of the bitumen-derived liquid into a refinery feedstock slate would require that it be hydrotreated to reduce the nitrogen and sulphur heteratom concentrations and to raise the atomic hydrogen-to-carbon ratio. The bitumen-derived liquid produced in a fluidized-bed reactor (diameter 10.2 cm) from the Whiterocks tar sand deposit has been hydrotreated in a fixed-bed reactor to determine the extent of upgrading as a function of process operating variables. The process variables investigated included total reactor pressure (11.0–17.2 MPa (1600–2500 psig)); reactor temperature (617–680 K; (650–765 °F)) and liquid hourly space velocity (0.18-0.77 h −1). The hydrogen/oil ratio was fixed in all experiments at 890 m 3 m −3 (5000 scf H 2/bbl). A sulphided Ni-Mo on alumina hydrodenitrogenation catalyst was used in these studies. The extent of denitrogenation and desulphurization of the bitumen-derived liquid was used to monitor catalyst activity as a function of process operating variables and to estimate the extent of catalyst deactivation as a function of time on-stream. The apparent kinetics for the nitrogen and sulphur removal reactions were determined. Product distribution and yield data were also obtained.

Effect of freeboard residence time on the molecular mass distributions of fluidized bed pyrolysis tars

Yields and molecular mass distributions are reported for tars obtained in an atmospheric pressure fluidized bed pyrolysis reactor operated at two different freeboard residence times (0.8 s and 4.5 s). Experimentally, significant tar loss through covalent bond scission for the longer freeboard residence time (4.5 s) was observed to occur at temperatures as low as 500 °C. At higher temperatures (580–750 °C) the molecular mass distributions of the tars appear to shift to lower values. The larger molecular mass fractions of the tars (typically the > 2500 Da fraction) are found in greater abundance in tars thought to have undergone the least extent of secondary reactions. Taken together, the data appear consistent with pyrolysis models describing tar evolution as being primarily limited by bond scission and evaporation of tar precursors.