Continuous-flow Pyrolysis Research Articles

Continuous flow pyrolysis of virgin and waste polyolefins: a comparative study, process optimization and product characterization

Continuous flow pyrolysis of virgin and waste polyolefins: a comparative study, process optimization and product characterization

Utilization of palm residues for biochar production using continuous flow pyrolysis unit

Biochar is a carbonaceous solid substance produced by heating biomass without using air. This research aimed to create and evaluate local carbonization pyrolysis using a screw conveyor and filtration equipment. Date palm frond (DPF) biochar was studied and tested at pyrolysis temperatures of 320, 390, and 460 °C, as well as feeding rates of 60, 90, and 120 kg/h. The physicochemical parameters of DPF biochar were evaluated using SEM and FTIR. When the pyrolysis temperature was raised from 320 to 450 °C, and the feed rates were reduced from 120 to 60 kg/h, the biochar yield of DPF and volatiles fell. At 460 °C and 60 kg/h, the maximum ash and fixed carbon content were 11.73 and 77.61 %, respectively. As the feed rate decreased and the temperature increased, the H and O values (1.96 and 2.62 %, respectively) of DPF biochar decreased considerably; the C and N values (83.60 and 0.24 %, respectively) trended inopposite directions. The BET surface area and pore volume increased as a result of the micropore surface area and volume at higher temperatures and lower feeding rates, but water holding capacity increased from 6.04 gwater/10 g at 320 °C to 6.78 gwater/10 g at 390 °C (60 kg/h). The results showed that the heating temperature increased and the feeding rate decreased; phosphorus) P(and magnesium (Mg) increased significantly, whereas the levels of potassium (K) and calcium (Ca) showed a non-significant increase. Furthermore, as the pyrolysis temperature increased, pH and EC increased from 7.90 to 10.96 and 2.91 to 4.25 dSm−1, respectively, while CEC declined; however, there were no significant changes in CEC. DPF biochar demonstrated enhanced macro porosity and surface area at 460 °C and 60 kg/h, making it acceptable for agricultural use as a soil supplement.

Co-pyrolysis of food waste and wood bark to produce hydrogen with minimizing pollutant emissions

In this study, the co-pyrolysis of food waste with lignocellulosic biomass (wood bark) in a continuous-flow pyrolysis reactor was considered as an effective strategy for the clean disposal and value-added utilization of the biowaste. To achieve this aim, the effects of major co-pyrolysis parameters such as pyrolysis temperature, the flow rate of the pyrolysis medium (nitrogen (N2) gas), and the blending ratio of food waste/wood bark on the yields, compositions, and properties of three-phase pyrolytic products (i.e., non-condensable gases, condensable compounds, and char) were investigated. The temperature and the food waste/wood bark ratio were found to affect the pyrolytic product yields, while the N2 flow rate did not. More non-condensable gases and less char were produced at higher temperatures. For example, as the temperature was increased from 300°C to 700°C, the yield of non-condensable gases increased from 6.3 to 17.5wt%, while the yield of char decreased from 63.6 to 30.6wt% for the co-pyrolysis of food waste and wood bark at a weight ratio of 1:1. Both the highest yield of hydrogen (H2) gas and the most significant suppression of the formation of phenolic and polycyclic aromatic hydrocarbon (PAH) compounds were achieved with a combination of food waste and wood bark at a weight ratio of 1:1at 700°C. The results suggest that the synergetic effect of food waste and lignocellulosic biomass during co-pyrolysis can be exploited to increase the H2 yield while limiting the formation of phenolic compounds and PAH derivatives. This study has also proven the effectiveness of co-pyrolysis as a process for the valorization of biowaste that is produced by agriculture, forestry, and the food industry, while reducing the formation of harmful chemicals.

A comparison of isotope ratio mass spectrometry and cavity ring-down spectroscopy techniques for isotope analysis of fluid inclusion water.

Online oxygen (δ18 O) and hydrogen (δ2 H) isotope analysis of fluid inclusion water entrapped in minerals is widely applied in paleo-fluid studies. In the state of the art of fluid inclusion isotope research, however, there is a scarcity of reported inter-technique comparisons to account for possible analytical offsets. Along with improving analytical precisions and sample size limitations, interlaboratory comparisons can lead to a more robust application of fluid inclusion isotope records. Mineral samples-including speleothem, travertine, and vein material-were analyzed on two newly setup systems for fluid inclusion isotope analysis to provide an inter-platform comparison. One setup uses a crusher unit connected online to a continuous-flow pyrolysis furnace and an isotope ratio mass spectrometry (IRMS) instrument. In the other setup, a crusher unit is lined up with a cavity ring-down spectroscopy (CRDS) system, and water samples are analyzed on a continuous standard water background to achieve precisions on water injections better than 0.1‰ for δ18 O values and 0.4‰ for δ2 H values for amounts down to 0.2 μL. Fluid inclusion isotope analyses on the IRMS setup have an average 1σ reproducibility of 0.4‰ and 2.0‰ for δ18 O and δ2 H values, respectively. The CRDS setup has a better 1σ reproducibility (0.3‰ for δ18 O values and 1.1‰ for δ2 H values) and also a more rapid sample throughput (<30 min per sample). Fluid inclusion isotope analyses are reproducible at these uncertainties for water amounts down to 0.1 μL on both setups. Fluid inclusion isotope data show no systematic offsets between the setups. The close match in fluid inclusion isotope results between the two setups demonstrates the high accuracy of the presented continuous-flow techniques for fluid inclusion isotope analysis. Ideally, experiments such as the one presented in this study will lead to further interlaboratory comparison efforts and the selection of suitable reference materials for fluid inclusion isotopes studies.

High-yield production of fuel- and oleochemical-precursors from triacylglycerols in a novel continuous-flow pyrolysis reactor

In this study, conversion of soybean oil was carried out in a continuous pyrolysis system with feed injected through an atomizer. This allowed introduction of micron-sized droplets of oil that could be rapidly vaporized inside the reactor. With this novel design, we were able to achieve feed vapor residence times (τ) of 6–300s without use of carrier gas, which would significantly reduce the overall cost of pyrolysis. Effects of reaction temperature (450<T<500°C) and τ on conversion, product yields and composition were investigated. At the optimum experimental conditions of T=500°C and τ=60s, the yield of pyrolysis liquids was as high as 88% (relative to feed mass). Under these conditions, the identified products consisted of 38% hydrocarbons (22% C5C12 and 16%>C12), 33% long-chain fatty acids (C16C18, but primarily oleic acid) and 15% short-chain fatty acids (C6C12). Upon distillation of the liquid products, the long-chain fatty acids were cleanly separated from the hydrocarbons. Overall, our results demonstrate the feasibility of producing liquid products at high yields, including a wide range of fuels (gasoline, jet and diesel) and enriched oleic acid (for oleochemicals production), using our reactor design for pyrolytic conversion of vegetable oil.

An experimental and kinetic modeling study of cyclopentadiene pyrolysis: First growth of polycyclic aromatic hydrocarbons

The importance of 1,3-cyclopentadiene (CPD) and cyclopentadienyl (CPDyl) moieties in the growth of polycyclic aromatic hydrocarbons (PAHs) was studied using new experimental data and ab initio calculations. The experimental investigation was performed in a tubular continuous flow pyrolysis reactor under both high (24molN2/molCPD) and low (5molN2/molCPD) nitrogen dilutions, covering a temperature range of 873–1123K, at a fixed pressure of 1.7bara. At the most severe conditions up to 84% of CPD is converted, and the amount of PAHs is more than 65wt%. Major products observed during CPD pyrolysis were benzene, indene, methyl-indenes and naphthalene, in line with previous studies. On-line GC×GC-FID/(TOF-MS) also allowed to quantify minor species (methane, toluene, styrene, phenanthrene, anthracene, etc.), never reported before at this level of accuracy. The new experimental data have been used to further analyze the role of the successive interactions of CPD, indene, and naphthalene as well as the recombination and addition reactions of their resonantly stabilized radicals and refine their kinetics. The results of the modeling study are in good agreement with existing and new experimental observations.

A continuous‐flow crushing device for on‐line δ2H analysis of fluid inclusion water in speleothems

A method for the isotope analysis of fluid inclusion water in speleothem calcite is presented. The technique is based on a commercially available continuous-flow pyrolysis furnace (ThermoFinnigan TC-EA). The main adaptation made to the standard TC-EA configuration is the addition of a crusher and cold trap unit, which is connected to the carrier gas inlet at the top of the TC-EA reactor tube. A series of tests conducted with this device shows that: (1) standard waters, injected in the crusher, and passed through a cryogenic trapping routine, yield accurate delta(2)H values; (2) crushed cubes of speleothem calcite from two Peruvian caves with rather dissimilar seepage water delta(2)H values yield fluid inclusion delta(2)H values in good accordance with these drip waters. The clear advantage of this continuous-flow technique for fluid inclusion isotope analysis is that it is relatively quick compared with other techniques. Since the conditions of water sample introduction into the TC-EA are identical for delta(2)H and delta(18)O analysis, we expect that only limited adaptations to the extraction procedure are required to provide delta(18)O analysis of fluid inclusion samples with the same device.

Gas-phase pyrolysis of heterocyclic compounds, part 1 and 2: flow pyrolysis and annulation reactions of some sulfur heterocycles: thiophene, benzo[b]thiophene, and dibenzothiophene. A product-oriented study

Continuous flow pyrolysis (CFP) of thiophene (1), benzo[b]thiophene (2), and dibenzothiophene (3) was investigated. 1 and 2 were studied in the temperature range 500-1100°C. Up to about 20 products were identified by GC-MS and their temperature profiles determined. 3 was pyrolysed at 900°C. All together, more than 30 products were identified in the pyrolysates, the largest number was found for 2. A distinct tendency to form polycyclic aromatic hydrocarbons (PAHs) and sulfur-containing polycyclic hetarenes (PHAs), even with more than one sulfur atom, is observed. At temperatures below 800°C, mainly ‘oligomers’ of the educts arise by radical recombination reactions. Above 800°C, fragmentation of the skeleton becomes important, and products are generated from the starting molecules and their fragments. From 1, PHAs such as benzo[b]thiophene (2, 29%), dibenzothiophene (3, 11%), and thianthrene (22, 4%), and from 2, PHAs such as benzo[b]naphtho[2,1-d]thiophene (32, 13%) and [1]benzothieno[2,3-b][1]benzothiophene (21, 5%) are formed in highest amounts at 850–900°C. Minor amounts of highly annulated thiophenes such as triphenyleno[1,1a,1b,2-b,c,c]thiophene (28) and benzo[1,2-b:3,4-b′:6,5-b″]tri(benzo[b]thiophene) (36), are detected. Formation of PAHs such as benzene (4), naphthalene (5), phenanthrene (7), fluoranthene (8), and pyrene (9) increases rapidly above 850°C. Product formation is explained by annulation reactions of the educts with their fragments (PHAs) or by exclusive combination of fragments (PAHs). Benzo-annulation of thiophene increases the thermal stability.

Gas phase pyrolysis of heterocyclic compounds, part 4: flow pyrolysis and annulation reactions of some oxygen heterocycles: furan, benzo[b]furan and dibenzofuran. A product oriented study

Continuous flow pyrolysis (CFP) of furan ( 1), benzo[b]furan ( 2) and dibenzofuran ( 3) has been investigated at 900°C. Complete decomposition of 1 and 2 was observed, while 3 proved to be more temperature resistant. In the pyrolysates of 1– 3, up to 22 different products were identified by GC-MS, 12 of these are identical. Mainly polycyclic aromatic hydrocarbons (PAHs), such as naphthalene ( 11) (6–28%), phenanthrene ( 17) (2–25%), biphenyl ( 22) (1–11%), pyrene ( 18) (1–10%), benzopyrene ( 19) (1–10%), fluoranthene ( 20) (3–9%), triphenylene ( 21) (3–9%), acenaphthylene ( 13) (1–6%), anthracene ( 23) (1–6%) and fluorene ( 12) (1–3%), were obtained. Only from 3, small amounts of larger oxygen containing polycyclic hetarenes (PHAs), such as benzo[b]naphtho[2,3-d]furan ( 37) and benzo[1,2-b:4,5-b′]bis[1]benzofuran ( 36), are generated as additional products besides PAHs.

Gas phase pyrolysis of heterocyclic compounds, part 3. Flow pyrolysis and annulation reactions of some nitrogen heterocycles. A product oriented study

Continuous flow pyrolysis (CFP) and annulation reactions of pyrrole (1), its benzo-annulated derivatives indole (2) and carbazole (3), pyridine (4), quinoline (5), and isoquinoline (6) have been investigated at 900 o C. While for 1, 2, 4-6 between 15 and 24 products were identified by GC-MS, 3 is rather stable under the reaction conditions and naphthalene (18) was found as the only substantial product. Except for 3, about 10 compounds were always present in the pyrolysate, benzonitrile (14) (6-24%) and naphthalene (18) (2-21%) being the most prominent products. Compounds 4-6 have even 16 common pyrolysis products. Among the major products are nitrogen heterocycles like quinoline (5) (4-13%), isoquinoline (6) (0-8%), and indole (2) (0.5-3%), cyano-substituted aromatic hydrocarbons like 14, 1-cyanonaphthalene (17) (0-16%), and 9-cycanoanthracene (19) (0-6%), as well as the corresponding unsubstituted parent compounds like 18, phenanthrene (31) (2-10%), pyrene (38) (1-5%), and fluoranthene (22) (2- 8%). In addition to the volatile products, several heavy compounds were identified by direct inlet MS. Possible routes of product formation are outlined. The relative amounts of unreacted starting material clearly indicate that benzo-annulation of pyrrole and pyridine causes considerable increase of thermal stability.

Oxygen isotopes in tree rings of Abies alba: The climatic significance of interdecadal variations

We determined the δ18O variations in the latewood of tree rings from four silver firs (Abies alba Mill.) for the period 1840–1997 at a mountain site in Switzerland, establishing the longest available tree ring record for δ18O in central Europe. The isotope ratios were determined on whole wood with a rapid continuous flow pyrolysis technique, thus avoiding cellulose extraction. We found significant correlations with δ18O tree ring records from the same region, although these involved different materials (cellulose extracted from whole rings rather than latewood) and different species. This indicates that physical factors are more important than biological influences as a determinant of δ18O in tree rings. The isotope tree ring chronology was highly correlated with the oxygen isotope variations in the June/July precipitation for the period 1972–1992 (r=0.72), and δ18O in whole wood of tree rings is therefore well suited for the reconstruction of δ18O in precipitation. We found a slow, quasi‐periodic variation of the δ18O series with a periodicity of ∼24 years, which is correlated to variations in the July temperature. This could be caused by fluctuations in the large‐scale atmospheric circulation over Europe and the North Atlantic, which may result in a change in source and flow path of atmospheric moisture, affecting the isotope ratio of precipitation in Switzerland. Although a significant correlation with summer temperature was found (p&lt;0.01), the low correlation coefficient (r = 0.31) indicates that the δ18O variations cannot be explained by temperature variations alone. However, even when considering that the factors influencing δ18O in precipitation are not yet fully understood, our study shows the potential of tree rings to provide long records of δ18O in precipitation for continental areas, which will improve our understanding of the causes of natural perturbations of the climate system.

Measurement of deuterium incorporation into fatty acids by gas chromatography/isotope ratio mass spectrometry

A continuous-flow pyrolysis interface for gas chromatography/isotope ratio mass spectrometry (GC/IRMS) has been developed for δ2H analysis of individual organic compounds. Pyrolysis of gas chromatographically separated fatty acid methyl esters is performed at 1200 °C in an unpacked alumina tube to convert nanomole quantities of individual compounds to H2. Hydrogen is separated from other gaseous pyrolysis products on a solid-phase capillary column prior to its entering the mass spectrometer. Use of an isotope ratio mass spectrometer with high mass dispersion ensures 2H1H:1H1H ratio measurement is accurately made in the presence of a large excess of helium carrier gas. The technique has been applied to the measurement of lipid synthesis in humans, using deuterium oxide (D2O) incorporation into fatty acids. Using safe body water deuterium enrichments (<0.5%) the labelled fatty acids are unlikely to contain more than one deuterium per molecule, and show similar chromatographic behaviour to natural abundance samples. Following overnight incorporation of D2O, plateau palmitate enrichments were measured by GC/IRMS with a relative standard deviation (RSD) of ∼0.5%. This compares favourably with GC/MS measurements for which an RSD of 5 to 10% would be expected for similar samples. Compared to off-line sample conversion and IRMS, the current approach is much less laborious and gives information on individual fatty acids rather than the mixed triacylglycerols. Copyright © 1999 John Wiley & Sons, Ltd.

High-Precision δ2H and δ18O Measurement for Water and Volatile Organic Compounds by Continuous-Flow Pyrolysis Isotope Ratio Mass Spectrometry

An on-line pyrolysis technique is described for analysis of δ2H and δ18O by continuous-flow isotope ratio mass spectrometry. A pyrolysis furnace packed with nickel, on which carbon is deposited as required, is shown to give efficient conversion of nanomole quantities of sample material to H2 and CO. A water trap and postpyrolysis gas chromatograph separate analyte gases from traces of H2O and CO2. The isotope ratio mass spectrometer used gives adequate separation of 2H1H+ and 4He+ to allow use of He as carrier gas. The pyrolysis technique provides a rapid method for analysis of water with a precision of ±2‰ for δ2H and ±0.3‰ for δ18O. Similar precisions are obtained for injections of 0.5 μL of urine and volatile organic compounds. Memory between samples is <2% for both δ2H and δ18O measurement. The technique is accurate over a wide range of enrichment for both δ2H and δ18O and is suitable for use in natural abundance and tracer studies of liquid samples.

Pyrolysis of oil sand from the Whiterocks deposit in a rotary kiln

A rotary kiln reactor was evaluated for thermal recovery of oil from Utah oil sands. A series of continuous-flow pyrolysis experiments was conducted. Process variables investigated included temperature (748–848 K), solids retention time (10–27 min) and sweep gas flow rate (1.27–2.83 m s 3 h −1). The results indicated that the pyrolysis temperature and the solids retention time were the two most important variables affecting the liquid and gas yields. The liquid yield (C 5 +]) decreased and the gas yield (C 1–C 4) increased with increasing temperature. The liquid yield increased with decreasing solids retention time, while the gas yield decreased. No significant effect of the sweep gas flow rate on the product distribution and yields was observed. The quality of the bitumen-derived liquids was significantly better than that of the bitumen. A preliminary process kinetics model which conforms to the observed trends was proposed.