Tar Production Research Articles

Measuring ancient technological complexity and its cognitive implications using Petri nets

We implement a method from computer sciences to address a challenge in Paleolithic archaeology: how to infer cognition differences from material culture. Archaeological material culture is linked to cognition, and more complex ancient technologies are assumed to have required complex cognition. We present an application of Petri net analysis to compare Neanderthal tar production technologies and tie the results to cognitive requirements. We applied three complexity metrics, each relying on their own unique definitions of complexity, to the modeled production processes. Based on the results, we propose that Neanderthal technical cognition may have been analogous to that of contemporary modern humans. This method also enables us to distinguish the high-order cognitive functions combining traits like planning, inhibitory control, and learning that were likely required by different ancient technological processes. The Petri net approach can contribute to our understanding of technology and cognitive evolution as it can be used on different materials and technologies, across time and species.

Identifying Palaeolithic birch tar production techniques: challenges from an experimental biomolecular approach

The intentional production of birch bark tar by European Neanderthals as early as 190,000 years ago plays an important role in discussions about the technological and behavioural complexity of Pleistocene hominins. However, research is hampered because it is currently unknown how Neanderthals were producing birch tar. There are several different techniques that could have been employed, but these differ in their apparent production complexity, time and resource efficiency. Identifying production processes in the archaeological record is therefore paramount for furthering research on the technical behavioural repertoire. Organic biomarkers, identified with Gas Chromatograph–Mass Spectrometry (GC–MS), have been used to identify possible production processes during the Neolithic. Here we test whether these biomarkers can also distinguish Palaeolithic (aceramic) tar production methods. We produced tar using five different methods and analysed their biomolecular composition with GC–MS. Our results show that the biomarkers used to distinguish Neolithic tar production strategies using ceramic technology cannot be reliably used to identify tar production processes using aceramic Palaeolithic techniques. More experimentation is required to produce a larger reference library of different tars for future comparisons. To achieve this, complete GC–MS datasets must also be made publicly available, as we have done with our data.

Scaling Palaeolithic tar production processes exponentially increases behavioural complexity

Technological processes, reconstructed from the archaeological record, are used to study the evolution of behaviour and cognition of Neanderthals and early modern humans. In comparisons, technologies that are more complex infer more complex behaviour and cognition. The manufacture of birch bark tar adhesives is regarded as particularly telling and often features in debates about Neanderthal cognition. One method of tar production, the ‘condensation technique’, demonstrates a pathway for Neanderthals to have discovered birch bark tar. However, to improve on the relatively low yield, and to turn tar into a perennial innovation, this method likely needed to be scaled up. Yet, it is currently unknown how scaling Palaeolithic technological processes influences their complexity. We used Petri net models and the Extended Cyclomatic Metric to measure system complexity of birch tar production with a single and three concurrent condensation assemblies. Our results show that changing the number of concurrent tar production assemblies substantially increases the measured complexity. This has potential implications on the behavioural and cognitive capacities required by Neanderthals, such as an increase in cooperation or inhibition control.

Pyrotechnology and lipid biomarker variability in pine tar production

Tar or pitch produced from pine resin and wood played an important role in the past as an adhesive, waterproofing and medicinal product. However, the formation and biomolecular composition of pine tar produced only from resin under different combustion conditions (i.e., temperature and oxygen availability during heating) has not been as widely investigated as pine tar produced by dry distillation of wood or birch bark tar, for which an extensive literature is available. This lack of information hampers technological interpretations of biomolecular data obtained from organic residue analyses of archaeological pine tar products. In this study, we performed controlled laboratory heating sequences with pine resin (Pinus canariensis) at 150, 250, 350 and 450 ºC under both oxygenated and oxygen-limited conditions, and analyzed the products using gas chromatography-mass spectrometry (GC-MS). A control unheated resin sample was also analysed. We found that the formation of pine tar from resin occurs around 250–350 ºC under both oxygenated and oxygen-limited atmospheres. We also present and discuss the lipid biomarkers of pine resin and its combustion products according to changes in temperature and oxygen availability. Our reference data provide new information for the biomolecular identification of archaeological pine tar products and show potential for shedding light on the conditions in which tar was manufactured by ancient populations in different contexts.

Conversion and rate behavior of brown macroalgae in pyrolysis: Detailed effects of operating parameters

Non-catalytic pyrolysis of brown macroalgae (Padina sp.) was studied in a batch reactor at temperature ranges of 400–600 °C and 10–90 min reaction times on the product distribution and conversion rate behavior. The highest pyro-oil and pyro-gas yields were obtained at 600 °C, which reached 67 wt% and 27 wt%, respectively, when the reaction times were prolonged (30–90 min). In addition, the high reaction temperature resulted in more generations of heavy tar and a considerable enhancement in aromatization degree. N-aromatic groups and phenol were observed from pyro-oil at 500 °C and 600 °C, respectively. Tar yield increased with reaction temperature, reflecting an order of reaction greater than one for tar production. The rate constant of tar formation was found to be 0.0013/s at 400 °C; 0.0023/s at 500 °C; and 0.0033/s at 600 °C, respectively, with the reaction order being higher than one (1.25). These findings highlighted that the proposed model could be used to accurately predict the pyrolysis process's behavior.

Atomic-level analysis of migration and transformation of organic sodium in high-alkali coal pyrolysis using reactive molecular dynamics simulations

Monitoring the migration and transformation of free radicals and alkali metals (such as tar- and organic gas-bonded sodium) in high-alkali coal pyrolysis through experimental methods alone is a challenging task. To address this challenge, in this work we employed reactive force field (ReaxFF) molecular dynamics simulations to model the transformation behavior of sodium at the atomic level. The different forms of sodium [sodium atoms (Na(g)), sodium hydroxide (NaOH(g)), tar-bonded sodium, and organic gas-bonded sodium] were carefully analyzed to gain insights into their migration during the pyrolysis process. The results show that inherent organic sodium forms binary or multiple coordination structures with oxygen atoms in the coal matrix during pyrolysis. During pyrolysis, inherent organic sodium was transformed into three main sodium species: Na atoms, NaOH, and Na·H2O. The repeated reactions between these sodium-containing intermediates and the coal matrix strengthen the three-dimensional network structure of the coal matrix and hinder its graphitization. The preponderance of Na(g) predominantly stems from organic sodium C1–40+Na, while NaOH and Na·H2O contribute to a lesser extent. The formation of NaOH and Na·H2O can be primarily attributed to the presence of Na(g), with merely a limited portion arising from organic sodium (C1–40+Na). The results also show that organic sodium inhibits char and tar formation at high temperatures, whereas at low temperatures it promotes char formation and inhibits tar production.

Experimental research on hydrogen-rich syngas yield by catalytic biomass air-gasification over Ni/olivine as in-situ tar destruction catalyst

This research focuses on investigating the air-gasification process of pine sawdust using a fluidized bed unit with Ni/olivine as an in-situ tar destruction catalyst. The goal is to eliminate tar production and obtain high-quality synthesis gas. Consequently, the effects of reaction conditions and catalyst properties on the producer gas composition, the lower heating value (LHV) of the yielded synthesis gas (syngas), char conversion efficiency (CCE), and cold gas efficiency (GE) are comprehensively explored. The conclusions indicate that higher temperatures favor the H2 and CO production and result in an evident decrease of CH4 and C2H4, which is responsible for the increasing gas LHV. The tar capture efficiency (TCE) increases by increasing the equivalence ratio (ER); however, a reverse trend obtains for gas LHV because of a significant decline in the combustible gas contents. The results also reveal that when using Ni/olivine as the bed material, GE reaches an optimum value of 72.4% at equivalence ratio (ER) of 0.21 and then lowers down with a further increase in ER to 0.39 due to the enhanced char combustion reaction. The tar yield (1.3–6.8 g/Nm3) significantly decreases with temperature, whereas H2 concentration (14.1–29.8 vol %), CCE (51.3–89.1%), GE (44.8–86.1%) and gas LHV (5.13–7.19 MJ/Nm3) promote at high temperature. Compared to raw-olivine, the lower heating value (LHV) of the producer gas slightly increases under the same conditions (T = 800 °C and ER = 0.21) when the bed material is Ni/olivine. The conclusions obtained help to provide reliable theoretical guidance for operating condition optimization of biomass catalytic air-gasification with Ni/olivine as bed material in a fluidized bed reactor.

Detecting the Archaeological Traces of Tar Production Kilns in the Northern Boreal Forests Based on Airborne Laser Scanning and Deep Learning

This paper presents the development and application of a deep learning-based approach for semi-automated detection of tar production kilns using new Finnish high-density Airborne Laser Scanning (ALS) data in the boreal taiga forest zone. The historical significance of tar production, an important livelihood for centuries, has had extensive environmental and ecological impacts, particularly in the thinly inhabited northern and eastern parts of Finland. Despite being one of the most widespread archaeological features in the country, tar kilns have received relatively little attention until recently. The authors employed a Convolutional Neural Networks (CNN) U-Net-based algorithm to detect these features from the ALS data, which proved to be more accurate, faster, and capable of covering systematically larger spatial areas than human actors. It also produces more consistent, replicable, and ethically sustainable results. This semi-automated approach enabled the efficient location of a vast number of previously unknown archaeological features, significantly increasing the number of tar kilns in each study area compared to the previous situation. This has implications also for the cultural resource management in Finland. The authors’ findings have influenced the preparation of the renewal of the Finnish Antiquities Act, raising concerns about the perceived impacts on cultural heritage management and land use sectors due to the projected tenfold increase in archaeological site detection using deep learning algorithms. The use of environmental remote sensing data may provide a means of examining the long-term cultural and ecological impacts of tar production in greater detail. Our pilot studies suggest that artificial intelligence and deep learning techniques have the potential to revolutionize archaeological research and cultural resource management in Finland, offering promising avenues for future exploration.

Assessment of the chemical looping gasification of wheat straw pellets at the 20 kWth scale

In this work, the Biomass Chemical Looping Gasification (BCLG) process was evaluated for syngas production at the 20 kWth scale using wheat straw pellets as the fuel feedstock and ilmenite as the oxygen carrier. The effect of different operational variables –namely the fuel reactor temperature, the mean residence time of solids in the fuel reactor, the oxygen-to-biomass ratio (controlled by the oxygen fed into the air reactor) and the gas velocity in the carbon stripper– on the process performance and the syngas yield was analyzed. Interestingly, smooth operation of the CLG unit was observed and no agglomeration issues detected. In addition, char produced during devolatilization still retained its initial pellet shape and unconverted char pellets were elutriated from the fuel reactor mixed with the finer oxygen carrier particles. Both steady-state and transition periods were evaluated to have a complete overview of the process. Transition periods were characterized by a different oxygen transfer rate in the air and fuel reactors. Steady state was reached when the oxygen transference rate was the same in both reactors. In this sense, the oxygen transference rate in the fuel reactor was the main factor affecting the syngas yield and the cold gas efficiency. Also, the temperature and mean residence time of solids in the fuel reactor showed a considerable effect on the char conversion and, consequently, on the syngas yield. However, operating conditions hardly affected the production of light hydrocarbons (CH4 and C2-C3) and tar, which were maintained roughly constant throughout the experimental campaign.

Slow pyrolysis experimental investigation of biomass tar formation and hydrogen production by tar reforming

The characteristics of pyrolysis tar and catalytic hydrogen production during tar reforming with catalysts were investigated. Through the pyrolysis experiment of wheat straw at 400–800 °C, the change of tar yield and tar composition with pyrolysis temperature was obtained. In order to remove tar, different nickel-based catalysts were prepared and catalytic experiments were carried out. The results showed that the pyrolysis tar yield first increased and then decreased with the increase of temperature, and the maximum tar yield was 32.82% at 700 °C. The generation of tar mainly comes from the thermal decomposition of biomass before 500 °C, the homogeneous reactions of tar compositions begin to occur after 500 °C. Through the characterization of the catalysts and their catalytic performance, it was found that due to the interaction of Ni and Ce on the support surface, Ni particles were more evenly distributed on the surface of the support. By adding Ce into Ni/HZSM-5, more oxygen vacancies are formed on the catalyst surface, which makes the catalyst have higher reducibility and more active sites. Compared with 9Ni/HZSM-5, 9Ni3Ce/HZSM-5 has a better catalytic performance with the tar conversion of 89.34% and H2 composition of 0.43.

Syngas Quality in Fluidized Bed Gasification of Biomass: Comparison between Olivine and K-Feldspar as Bed Materials

The relevance of selecting an appropriate bed material in fluidized bed gasification is a crucial aspect that is often underestimated. The ideal material should be economical, resistant to high temperatures and have small chemical interaction with biomass. However, often only the first of such three aspects is considered, neglecting the biomass–bed interaction effects that develop at high temperatures. In this work, olivine and K-feldspar were upscale-tested in a prototype fluidized bed gasifier (FBG) using arboreal biomass (almond shells). The produced syngas in the two different tests was characterized and compared in terms of composition (H2, CH4, CO, CO2, O2) and fate of contaminants such as volatile organic compounds (VOCs), tar and metals.. Moreover, the composition of olivine and K-feldspar before and after the biomass gasification process has been characterized. The aim of this work is to show which advantages and disadvantages there are in choosing the most suitable material and to optimize the biomass gasification process by reducing the undesirable effects, such as heavy metal production, bed agglomeration and tar production, which are harmful when syngas is used in internal combustion engines (ICE). It has been observed that metals, such as Ni, Cu, Zn, Cd, Sn, Ba and Pb, have higher concentrations in the syngas produced by using olivine as bed material rather than K-feldspar. In particular, heavy metals, such as Pb, Cu, Cd, Ni and Zn, show concentrations of 61.06 mg/Nm3, 15.29 mg/Nm3, 17.97 mg/Nm3, 37.29 mg/Nm3 and 116.39 mg/Nm3, respectively, compared to 23.26 mg/Nm3, 11.82 mg/Nm3, 2.76 mg/Nm3, 24.46 mg/Nm3 and 53.07 mg/Nm3 detected with K-feldspar. Moreover, a more hydrogen-rich syngas when using K-feldspar was produced (46% compared to 39% with olivine).

Production and use of birch bark tar at the Neolithic pile‐dwelling of Palù di Livenza (North‐Eastern Italy) revealed by X‐ray computed micro‐tomography and synchrotron Fourier‐transform infrared spectroscopy

AbstractRecent excavations at Palù di Livenza (northeastern Italy) revealed a multiphase Neolithic pile dwelling dated between ca. 4,300/4200 and 3,600 cal BC. Three lumps with teeth imprints and a larger amorphous piece from the Late Neolithic layers have been studied by X‐ray computed micro‐tomography (microCT) and synchrotron Fourier‐transform infrared spectroscopy (FTIR). FTIR spectra match well that of birch bark tar and microCT of the larger piece has revealed a rolled‐up structure likely corresponding to bark rolls. The lumps of birch pitch were probably chewed to soften the tar prior to be used as hafting adhesive or therapeutic substance. The rolled‐up inner structure of the larger piece and the remains of birch bark tar and abundant charcoals on its surface suggest it probably corresponds to a rare waste product from allothermic tar production.

Effects of oxidation degree of support and phosphorus modification on the catalytic cracking of coal pyrolysis tar by char-supported nickel catalysts

The low rank coal can be converted efficiently when it undergoes the pyrolysis process. The utilization of tar is modified and the problems such as pipeline blockage are solved by cracking and lightning heavy components in tar. In this study, the char-supported nickel (Ni) catalysts were prepared by different Ni loading methods, and the cracking of coal pyrolysis tar was improved by the coal char support with different oxidation degrees. The catalysts prepared by ion exchange method showed better performance for the tar cracking than other methods, which is related to their smaller Ni crystallite size (NCS). The oxidation of H2O2 and HNO3 significantly increased the number of oxygen-containing groups. The intrinsic correlation between oxidation degree of support and catalytic property indicated that the XH2O2-Ni/C (ZD coal pretreated by H2O2) series catalysts had better tar cracking activity than XHNO3-Ni/C (ZD coal pretreated by HNO3) series catalysts, which did not only depend on the increase of Ni loading amounts but also related to the smaller NCS and higher dispersion. Moreover, the non-metallic additive phosphorus (P) was added to modify the catalysts. It was found that the addition of P significantly improved the tar cracking performance of the 30%H2O2 P-Ni/C catalyst. The amounts of active components loaded and NCS contributed to the production of light tar.

Mobile Rice Husk Gasifier Performance and Techno-Economic Analysis as Micro Scale Power Generation: Modeling and Experiment

Indonesia annually produces significant amounts of biomass waste in the agriculture sector. Rice husk, one of the highest produced agricultural waste materials, has sufficient caloric value to produce syngas in a gasification system to generate sustainable energy. However, the production of tar from rice husk gasification is significantly high, damaging the equipment and internal combustion engine. This study carried out performance analysis on a small-scale rice husk gasifier. A simulation provided a syngas composition overview and showed a maximum LHV value of 6.47 MJ/Nm3 at ER 0.25, and a maximum CGE value of 83% at a temperature of 900 ℃. Furthermore, the economic aspect of integrating renewable technology was also considered. The gasifier had an LCOE value ranging from 0.014 to 0.089 USD/kW, depending on the use of the gasifier. The feasibility of using a mobile rice husk gasifier was also inspected, based on net present value, benefit-to-cost ratio, and payback period.

Insight into influence of process parameters on co-pyrolysis interaction between Yulin coal and waste tire via rapid infrared heating

Co-pyrolysis of coal and waste tire is an important route to realize their clean and efficient utilization. To study the interaction during co-pyrolysis, the rapid infrared-heated fixed-bed reactor was adapted to explore the effects of heating rate, pyrolysis temperature and mixing ratio on the products distribution, tar quality and compositions during the co-pyrolysis of Yulin coal (YL) and waste tire (WT), and the interaction mechanism was also explored. The results show that heating rate, mixing ratio and pyrolysis temperature exerted the synergistic effect during co-pyrolysis. High heating rate was beneficial to the interaction of coal and waste tire, and the maximum positive synergistic effect of tar production was obtained at the heating rate of 10 °C/s. The content of light tar (boiling point < 360 °C) in co-pyrolysis tar increased gradually with amount of WT added in blends. When the mixing ratio of YL/WT was 1:1, the most remarkable difference between the experimental and calculated contents of light tar in tar suggested obvious positive synergy among the blended samples. In addition, gas production was remarkably suppressed during co-pyrolysis. It is analyzed that H-rich free radicals like H or CH3 produced from the cleavage of aliphatic hydrocarbon chains of WT or other reactions like cyclization stabilize the free radicals from coal pyrolysis and contribute to the improved tar quality and the synergy during co-pyrolysis.

Variation of molecular structures affecting tar yield: A comprehensive analysis on coal ranks and depositional environments

Coal with a tar yield ≥ 7 %, which is measured in the Gray-King assay, is called tar-rich coal in China. However, the comprehensive impact of coal ranks and depositional environments on tar yield is still unclear. Here, the coal petrology, molecular structure, and depositional environment of the samples were thoroughly investigated to clarify the influence of the coal rank and depositional environment on the tar-rich coal. The difference in the tar yield is attributed to the molecular structure. Concerning Fourier transform infrared (FTIR) spectroscopy, the high tar production resulted from the existence of relatively long aliphatic side chains and high aliphatic hydrogen content. For the 13C nuclear magnetic resonance analysis, the structure of the aliphatic carbon also played a crucial role in tar formation. Among these, the various unstable structural parameters (falH/fas, (fas + fap)/fa', fas/fa', falH/fal*) and weak bonds could improve the tar yield. Furthermore, the molecular structures were also controlled by the coal rank. More specifically, the CH2/CH3 in FTIR and the falH, falH/fa*, fas/fa’ in 13C NMR had similar patterns with coal rank, which was close to the pattern between the coal rank and the tar yield. This effect also indicated that the tar yield was mainly influenced by bridge bonds, aliphatic side chains, and branched aromatic carbon. Between similar coal ranks, the molecular structure differences originated from the depositional environment. For the coal facies, the tissue preservation index (TPI) and vegetation index (VI) were negatively correlated with CH2/CH3, Hal/H, and “A factor”. In contrast, they were positively correlated with the oxidation degree (Io2). The gelification index (GI) was also positively correlated with CH2/CH3 and Hal/H. Consequently, the coal-forming environment with a relatively high degree of decomposition, low woody tissue content, and high gelification can form key molecular structures easier, which is beneficial for the tar yield.

Industrial ecology and skin diseases

Technogenic effects on the production of oil, coal tar, other hydrocarbons and products of their processing can lead to diseases of the sebaceous glands. Gum-related factors trigger common links in the pathogenesis of vulgar and oily acne, which are inflammation, increased sebum production, excessive follicular hyperkeratosis. There is a description of the clinical manifestations of severe oily acne in a railway worker on previously unchanged skin. We also have a description of the severe stage of the course of vulgar acne in the assistant engineer of the railway, who has a genetic predisposition, also has a history of juvenile acne of mild severity. Chemical factors such as a mixture of hydrocarbons, phenol, creosote, asbestos-containing dust can provoke oily acne in a railway worker. Oxides of nitrogen, carbon, sulfur, nitrogen dioxide, technical mixtures of hydrocarbons, violation of physiological rhythms of nutrition, sleep, rest, severity and intensity of the labor process, constant stress can lead to a relapse of vulgar acne with a more severe course in workers of locomotive crews. The given clinical examples reveal the need for interdisciplinary interaction of dermatologists-venereologists and occupational pathologists in the treatment of skin pathology in workers of harmful industries.

Aspen Plus Simulation of Biomass Gasification: a Comprehensive Model Incorporating Reaction Kinetics, Hydrodynamics and Tar Production

Aspen Plus Simulation of Biomass Gasification: a Comprehensive Model Incorporating Reaction Kinetics, Hydrodynamics and Tar Production

Simultaneous in-situ tar abatement and H2-enriched syngas production via heterogeneous doping of LaFeO3 during chemical looping gasification of microalgae

Chemical looping gasification (CLG) is an emerging environment-friendly technology for efficient and clean utilization of biomass, in which oxygen carrier (OC) is one of the key issues concerning the overall performance. As a rising-star material, perovskite with a tunable crystal structure shows great potential in syngas enrichment and tar decomposition during the CLG of biomass. In this study, the newly-developed LaNi0.5Fe0.5O3 (LN5F5) and La0.3Ba0.7FeO3 (L3B7F) perovskites through heterogeneous doping of LaFeO3 (LF) were evaluated as oxygen carriers with the purpose of simultaneous tar abatement and H2-enriched syngas production from microalgae. Silica sand (SS) and iron ore (IO) were used for comparison. Results showed that the CLG performance order of several materials was L3B7F > LN5F5 > LF > IO > SS at an oxygen carrier to biomass ratio (O/B) of 0.4, water injection rate of 0.3 mL/min and gasification temperature of 800 °C. The heterogeneous doping obviously improved the cyclic stability of perovskite during redox tests. In addition, possible tar conversion routes over L3B7F oxygen carrier were proposed. Results implied that heavy PAHs (4 rings or more) were first converted to light PAHs (1–3 rings) and n-hydrocarbon, which were finally transformed into micromolecular gases. The outstanding performance of L3B7F in microalgae CLG can be ascribed to the formation of oxygen vacancies and high-valence Fe4+ stimulated by the introduction of Ba2+, which were demonstrated by the XRD, H2-TPR and XPS results. These results evidence that the heterogeneous doped L3B7F is a good alternative for improving biomass availability in the CLG process.

Advantages and limitations of an interdisciplinary approach in woodland archaeology: An example of 18th-19th century tar production in European temperate forest

Tar production was an important part of forest management until the beginning of the 20th century. Tar – used for many purposes – from glue, through boatbuilding, to a pharmacy – was widely produced throughout Europe. As early as in the 18th century, in some parts of Europe, tar production became massive. In the eastern part of Europe, however, that process was still carried out with simple methods known from the Middle Ages. With Airborne Laser Scanning, we have detected 53 traces of tar processing in the Polish part of the Białowieża Forest. In 2019, one of the features was archaeologically excavated to identify its preserved structure/architecture and collect samples for laboratory tests. The outcomes of the archaeological test trench did not provide answers to many research questions. Therefore, it was decided to apply an interdisciplinary approach to determine the utilised raw material, timing and the process of tar production. In result of the dendrochronological and anthracological analyses, it was found that diverse parts of Scots pine trees were used for tar production. Our tree ring analyses provided also the first information about the absolute chronology of the tar kiln activity. To obtain information on the tar production process, i.e. the burning temperature and the characteristics of the obtained tar, we performed chemical analyses of the tar samples (microscopic and Fourier Transform Infrared, FTIR). This multidisciplinary case study of one of the many sites from the Białowieża Forest provided basic information about the methods of tar production in modern times and their probable impact on the immediate vicinity of the forest. However, such an interdisciplinary approach is limited by both the quantity and quality of the preserved artefacts, found during archaeological excavations.