Tar Fractions Research Articles

Characterization of renewable reductants and charcoal-based pellets for the use in ferroalloy industries

This study investigates the effect of high-temperature pyrolysis and post-treatment processes on spruce and oak charcoal yields and CO2 reactivity in a slow pyrolysis reactor. Post-treatment processes such as co-pyrolysis of biomass and recirculated tar mixture with that to the distillation of the charcoal-tar blend gave similar increase in charcoal yields. From a technological standpoint, co-pyrolysis of charcoal and tar mixture decreased the CO2 reactivity of the charcoal approaching that of fossil-based coke. This emphasize the importance of tar addition and high temperature treatment on charcoal properties. Moreover, the findings of this work show the potential use of the tar organic fractions as a binder that can be used for the charcoal pellet preparation. The results are promising as they show that the charcoal-based pellets have comparable properties of pellets from herbaceous biomass leading to the cost reduction in charcoal transportation and storage.

Production of Commercial Naphthalene by Coal-Tar Processing

The derivation of commercial naphthalene by rectification is a possible approach in coal-tar processing. Naphthalene is widely used in chemical synthesis for the production of phthalic anhydride, superplasticizers, and intermediate products such as Cleve’s acids in dye production. The quality of the naphthalene derived from petroleum is markedly higher than that of coal-tar naphthalene, primarily in terms of the thionaphthene content, since the thionaphthene content in the initial petroleum fractions is much less than in the naphthalene fraction of coal tar. Simulation of the vapor–liquid equilibrium of binary and ternary mixtures of the components in coal tar by means of the NRTL activity model, at different pressures, indicates that 2,3-xylenol–naphthalene, naphthalene–thionaphthene, and 3-xylenol–naphthalene–thionaphthene mixtures are characterized by positive homogeneous azeotropes. The composition and boiling points of the azeotropes are determined. The presence of the azeotropes significantly complicates the derivation of naphthalene from the naphthalene fraction of coal tar, in which the naphthalene content exceeds 97%. Analysis of the composition of the initial mixture and the azeotropes suggests a design for a three-column system for the distillation of commercial naphthalene, with the preliminary separation of water without the need for special separating agents or chemical extraction of impurities. Optimization of the proposed equipment by means of HYSYS software indicates high technological flexibility of the process and the production of naphthalene from coal tar that matches the quality of the naphthalene derived from petroleum. The naphthalene content in the commercial product derived from coal tar by the proposed method is 99.99 wt %. The yield of naphthalene is 90.5 wt %. The energy consumption in the basic three-column system is 0.92 Gcal/t of commercial naphthalene (of purity 99.99 wt %). If heat is recycled in the three-column system, the energy consumption is reduced to 0.6 Gkal/t of product (with the same degree of purity). That is comparable with the energy consumption in a two-column system, and the commercial naphthalene produced is characterized by greater yield and purity.

An Effective Approach for Separating Carbazole and Its Derivates from Coal-Tar-Derived Anthracene Oil Using Ionic Liquids

Carbazole and its derivates are important value-added chemicals (VACs) in anthracene oil (AO), which is one of the coal tar fractions. In this work, imidazolium-based ionic liquids (ILs) were used ...

Tar-Based Modification of Carbon Mass for Self-Igniting Anodes

The modification of carbon mass for self-igniting anodes is considered. The mass consists of a binder–filler system. The modifier employed is the phenolic fraction of coal tar. The filler is anthracite treated at 1800°C. The binder is moderate-temperature electrode pitch (grade B). Research shows that cocarbonization of the modifier in the binder–filler system on heating may consist of two processes: 1) before transition of the pitch to a viscofluid state, the additive facilitates mutual approach of its macromolecules and expands the temperature range of nucleation of graphite-like structures; 2) on account of adhesive forces, the phenolic fraction is attached to the filler (thermoanthracite) surface. That, in turn, should intensify the wetting, adsorption, adhesion, and sintering capacity of the electrode pitch (binder).

Distribution and modeling of tar compounds produced during downdraft gasification of municipal solid waste

Tar compounds produced during gasification of municipal solid waste (MSW) hinder downstream utilization of syngas. This study investigated the effects of operating conditions (temperature, equivalence air ratio (ER) and MSW moisture content) during gasification using air on tar emissions. Tar was quantified by gravimetric and GC-MS methods, denoted as gravimetric and collected (GC-MS) tar, respectively. Additionally, styrene evolution was studied as it is one of the main tar compounds produced from MSW. By applying the response surface methodology for modeling, it was found that tar contents quantified by the two methods are influenced similarly by ER and MSW moisture content, but differently by temperature. This discrepancy was attributed to the different composition and properties of tar fractions measured by gravimetric and GC-MS methods. Since the selection of analytical method can have impact on the quantification of tar, adoption of different methods for the characterization of tar emissions from MSW gasifiers is essential in order to provide a holistic analysis of the tar evolution process. The content of styrene in collected (GC-MS) tar from MSW gasification was 13–29%. The lower contents of styrene were favored by operating temperature between 850 and 900 °C, higher ER and higher MSW moisture content.

Pretreatment of lignite by acidic bronsted ionic liquid [B(SO3H)mim]OTf for lignite pyrolysis

The effect of pretreatment with acidic bronsted ionic liquid 1-sulfonic acid butyl-3-methylimidazolium trifluoromethanesulfonate ([B(SO3H)mim]OTf) on Shengli lignite (SL) pyrolysis behavior and its pyrolysis products distribution were investigated in this paper. In order to study the mechanism of [B(SO3H)mim]OTf pretreatment on the dissolution of SL, [B(SO3H)mim]OTf treated-SL was also analyzed by the Fourier Transform Infrared Spectroscopy (FTIR), Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT) and TG-DTG. It is found that the pretreatment temperature and the ratio of [B(SO3H)mim]OTf to SL have a significant impact on the pyrolysis of SL. The pretreatment of SL with [B(SO3H)mim]OTf can not only result in the increase of the yield of total tar and light oil fraction but also improve the quality of tar. After the pretreatment at 200 °C and [B(SO3H)mim]OTf/SL at 1, the tar yield, light fraction content, arenes, and phenolics content in tar is 1.6, 2.4, 6.3 and 3.2 times higher than that from raw SL pyrolysis, respectively. Pretreatment with [B(SO3H)mim]OTf leads to the fracture of the coal network, resulting in the increase of the content of CO and COC bonds and the disruption of hydrogen bonds.

Obtaining of Coumarone-Indene Resins Based on Light Fraction of Coal Tar. 3. Coumarone-Indene Resins with Methacrylic Fragments

The method for obtaining coumarone-indene resins with methacrylic fragments (CIRM) was developed with the addition of methyl ethacrylate, using a light fraction of coal tar and its fraction boiling within 423–463 К. CIRM was obtained via radical cooligomerization using 2,2'-azobis (2-methyl-propionitrile) as the initiator. The effect of the initiator amount, temperature and reaction time on the yield, softening temperature and molecular weight of CIRM has been established. The structure of the synthesized CIRM has been confirmed by IR and NMR spectroscopy. It is proposed to use CIRM as a polymer component of bitumen-polymeric mixtures (BPS). The effect of CIRM amount, temperature and time on the main characteristics of BPS has been studied.

Influence of In-Bed Catalysis by Ash-Coated Olivine on Tar Formation in Steam Gasification of Biomass

The use of catalytic bed materials has become a state-of-the-art solution to control the concentration of tar in fluidized bed biomass steam gasifiers. Ash-coated olivine is commonly applied as bed material, owing to its relatively high catalytic activity towards tar species. However, the mechanisms and conversion pathways influenced by the ash-coated olivine when applied as an in-bed catalyst are still not well understood. The present work aims at proving that the ash-layered olivine prevents the formation of biomass-derived tar at an early stage of their formation. Tests with olivine at different stages of activation and at different temperatures are carried out in the Chalmers 2-4MWth DFB gasifier. Detailed characterization of the tar and light hydrocarbon fractions are presented and discussed in relation to the sources of aromatic species. It is concluded that the ash-coated olivine prevents the formation of aromatic tar species by promoting the steam reforming of early tar precursors. Gas-phase interactions of the early tar precursors and bed material contribute to the tar reduction observed. The results indicate that olivine interferes the cyclization routes involving C2H2 and C3 hydrocarbons.

Modification of Electrode Pitch

The phenolic fraction of coal tar may be used to modify the group composition and rheology of pitch, according to the results of the present study. Modification of electrode pitch with a softening temperature of 55°C changes the group composition of the β fraction. That improves characteristics such as the sorptional capacity, limiting wetting angle, and wetting index. Theoretical and practical research shows that introducing 15–20% of the phenolic fraction in 1000 g of pitch improves its plasticity. The processes responsible for the characteristics of pitch in each technological step are studied. The thermochemical transformations of the pitch components with coal tar at low levels of pyrolysis are identified. By this means, the group composition of coal pitch may be modified.

Selective production of phenolics from waste printed circuit boards via microwave assisted pyrolysis

Abstract In this study, microwave assisted pyrolysis of waste printed circuit boards (PCBs) using carbonaceous susceptors like graphite and activated carbon was conducted to devise an efficient technique to treat the electronic wastes. Pyrolysis experiments were conducted in a batch microwave reactor, and the effects of PCB to susceptor mass ratio and the type of susceptor on the yields and composition of char, tar and gas were evaluated. The effect of increasing the initial mass of PCB from 10 to 100 g on product yield and quality was also assessed. Different analytical techniques were adopted to determine the composition of (a) tar compounds like phenols and oxygenated compounds, (b) non-condensable gases like H2, CO2 and CH4, and (c) metals in char. Char constituted a major fraction of the products (ca. 58 wt.%). High amount of susceptor resulted in low yield of tar and high yield of gases. The mass and energy yields of tar were high when graphite was used as the susceptor. Tar fraction contained phenolic compounds and phenyl phosphates in significant amounts. Higher amount of susceptor, i.e. 10:50 g/g of PCB:susceptor, resulted in >90% selectivity of phenol in the tar fraction. Average heating value of the tar fraction was 31.8 MJ kg−1. CO2 was the major component in the gas fraction, and the production of H2 was more when activated carbon was used as the susceptor. The major metals present in char were Cu, Pb, Ti, and other metals present in minor amounts included Bi, Fe and Ca. The average heating value of char was 19 MJ kg−1.

FLASHCHAIN Theory for Rapid Coal Devolatilization Kinetics. 11. Tar Hydroconversion during Hydrogasification of Any Coal

This paper introduces a FLASHCHAIN-based reaction mechanism for oils production during tar hydroconversion with any coal for any hydrogasification conditions. Oils are generated by the hydrogenation of tar monomers in two stages. In the first stage, the tar monomers released as primary tars are rapidly hydrogenated into oils at the monomer hydrogenation rate. Since elevated pressures always shift primary tar molecular weight distributions toward lighter species, monomers constitute substantial fractions of primary tar, and as much as one-half the ultimate oils yield is produced soon after the onset of tar hydroconversion. In the second stage, additional tar monomers are gradually released by hydrocracking of larger tar molecules and then hydrogenated into oils, while control of the oils production rate shifts from monomer hydrogenation to hydrocracking. Oil yields are uniform with H2 pressures higher than 1 MPa because rates of monomer hydrogenation and hydrocracking accelerate for progressively higher H2 pressures to compensate for diminishing primary tar yields. Predicted oil yields grow for progressively hotter temperatures. The analysis shows that aliphatic tar components must be incorporated into oils along with their aromatic nuclei during monomer hydrogenation and constitute one-half or more of the oils yield at the highest H2 pressures. Primary tar composition and, especially, their structural components determine the maximum oil yields from different coals. The sample-to-sample variability in primary tar yields is apparent in their associated oil yields. In combination, the mechanisms for hydropyrolysis, tar hydroconversion, and char hydrogasification accurately interpreted a database representing coals of rank from lignite to anthracite, heating rates from 1 to 104 °C/s, temperatures from 475 to 900 °C, coal contact times from 1 to 900 s, gas contact times from 2 to 42 s, and H2 pressures from 0.3 to 15 MPa.

Effect of phosphorus modification on the coal tar hydrogenation activity of the Ni–Mo/γ-Al2O3 catalyst

In this study, a Ni–Mo/γ-Al2O3 catalyst was prepared by the saturated impregnation method, and the catalyst was modified by phosphorus. Through the model compound, hydrogenation experiments and the coal tar hydrogenation experiments, five kinds of Ni–Mo/γ-Al2O3 catalyst with different phosphorus addition were evaluated. The hydrogenation experiments were carried out for three compounds, quinoline, dibenzothiophene and phenol, and the conversion rules of these three compounds under the action of five kinds of catalyst were analyzed. Finally, the effect of HDS, HDN and HDO on coal tar was determined by comparing with the real fraction of coal tar. The results show that the different addition of phosphorus has different effects on the activity of coal tar hydrogenation. The appropriate amount of phosphorus can increase the activity of HDS, HDN and HDO of the catalyst, while the excessive phosphorus will inhibit the activity. By comparing the hydrogenation experimental results of model compounds and that of coal tar, it could be concluded that because the composition of coal tar is complex, various heteroatom compounds and various unsaturated hydrocarbons form competitive adsorption on the catalyst surface, resulting in the inhibition of the conversion of various heteroatom compounds. The phosphorus content of the Ni–Mo/γ-Al2O3 catalyst suitable for hydrogenation of coal tar is higher than that of the model compounds.

Study of properties of tar obtained from underground coal gasification trials

This work presents the results of an experimental study on the properties of tar that originated from underground coal gasification (UCG) trials. Two in situ experiments of UCG were performed using oxygen as the gasification agent under the HUGE and HUGE 2 projects. Trials were conducted using different configurations of the fire channel, gasification time and method of raw gas collection and purification. The obtained tars were analysed over a wide range of parameters that are typical for the assessment of the quality of conventional coke oven tar. The results of the analysis showed that in terms of physical–chemical properties, both tars are highly different from each other, as well as from typical coal tar from a coking plant. One characteristic observation of the UCG-derived tars is a higher content of ash as well as toluene and quinoline insolubles compared with a typical coke oven tar. Both tars are susceptible to thermal destruction and degradation to lighter products, and the characteristics of the coking distillation residue after heating to high temperatures is different from coke oven tar. The tested tars vary in boiling range and fractional composition. The analysis also showed that tars from UCG contain more heterocyclic compounds than does coke oven tar, and the tar from HUGE is heavier than tar from HUGE 2. The content of PAHs in the tar from HUGE is many times higher than in tar from HUGE 2 and at a similar level as coke oven tar; however, the naphthalene content in both UCG tars is many times lower compared to typical coke oven tar. The probable reasons for the differences described in this report include the tar residence time in the sampling point, as well as different extents of tar fractionation phenomena, which resulted from the distinct configurations of the gas transportation and purification systems.

Catalytic upgrading of coal pyrolysis products over bio-char

Several reactions parallel happened during co-pyrolysis of coal and biomass, such as primary volatiles of coal and biomass will contact and react with the nascent char from coal or biomass themselves' pyrolyzed. To clarify the function of bio-char and investigate if bio-char has the catalytic effect on pyrolysis products of Hulunbuir lignite, a two-stage reactor is designed and used in this study. The effects of bio-char preparing temperature, char-making method and usage amount of bio-char were discussed. In comparison with the alone coal pyrolysis at 650 °C, the portion of light tar (n-hexane soluble) from pyrolysis of coal with bio-char (20 wt% of coal), increased by 30.31%, gas volume yield increased by 9.05% and the volume yield of hydrogen and methane increased by 6.36% and 5.64%, respectively. For the most efficient RSCR-700 against the test with quartz, the H/C molar ratio in RSCR-700's produced tar increased by 22.06%, while the contents of N and S elements decreased by 27.88% and 25.0% accordingly. The role of bio-char in the coal tar upgrading process was further explored through the instruments characterization. Besides the thermal cracking, the bio-char also can provide catalytic active sites to crack heavy fraction of coal tar.

Pyrolysis of waste tire rubber: Influence of temperature on pyrolysates yield

Previous studies conducted on the pyrolysis of used rubber were either directed towards the yield and properties of liquid fuel or focused towards the generation of carbon black as end product and, hence, little attention was paid to the quantitative determination of gaseous, liquid, tar and char fractions obtained from the pyrolysis of used tire rubber. Therefore, the aim of this study was to re-utilize waste tire rubber as raw material for production of these valuable products which has substantial benefits for domestic and commercial use. Pyrolysis experiments were performed for thermal degradation of used tire rubber (UTR). The pyrolysates from the pyrolyzer were collected in separate traps on the basis of volatility into fractions like tar, liquid and gas. Influence of temperature was determined. The gaseous fraction was monitored using gas chromatography and the major hydrocarbons detected were C1–C5. The liquid fraction was analyzed by gas chromatography/mass spectrometry and the compounds detected in the range of C16 to C19. As the different fractions (gas, liquid, tar and char) were collected independently of each other, therefore, they may be used separately for useful purposes.

Molecular composition of low temperature coal tar and its transformation in the hydrogenation-refining process

The low temperature coal tar is a complex mixture which poses a challenge to chemists for the molecular characterization. The State Key Laboratory of Heavy Oil Processing in the China University of petroleum-Beijing carried out in-deep analysis of the low temperature coal tar based on advanced technologies such as high resolution mass spectrometry. This review introduces the progress in molecular composition of low temperature coal tar. Bulk properties and molecular composition were characterized for ten coal tars derived from different low rank coals by gasification or carbonization. Distillation, extraction, and chromatographic methods were developed for the separation for various coal tar fractions. The raw coal tars, their fractions and hydrogenation-refining products were analyzed by gas chromatography-mass spectrometry (GC-MS) and high resolution mass spectrometry. Transformation of various compounds, especially for the heteroatoms was investigated in molecular level along the hydrogenation-refining process. In deep understanding of molecular composition and the transformation mechanism of coal tar will provide theory and data foundation for the utilization of low temperature coal tar, including the technology selection, catalyst design, process development and optimization.

Obtaining of Coumarone-Indene Resins Based on Light Fraction of Coal Tar. 2. Coumarone-Indene Resins with Epoxy Groups

Obtaining of Coumarone-Indene Resins Based on Light Fraction of Coal Tar. 2. Coumarone-Indene Resins with Epoxy Groups

Screening of organic compounds in complexly contaminated scrubber dust by GC × GC-MS and FT-ICR-MS

Theisen sludge is a complexly contaminated scrubber dust, which arised during the production of copper stone. Besides high contents of heavy metals, it also contains approximately 10% of a tar like organic fraction. Inorganic and organic components both represent an environmental risk and the assessment of potential remediation activities requires a detailed analysis of the contaminants. In this study, the organic part of the scrubber dust was analyzed by highly resolving gas chromatographic and mass spectrometric methods.Lower molecular weight compounds were analyzed by comprehensive gas chromatography (GC × GC-MS). A complex mixture of aliphatic and aromatic hydrocarbons was observed, which was predominantly composed of aromatic hydrocarbons with one to 4 rings with different number and length of alkylsubstituents. The most abundant heteroatomic compounds observed are benzo- and dibenzothiophenes and their alkylated homologues, but also phenols, carbazoles and acridines could be observed.Higher molecular weight compounds were analyzed by fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Two different ionization methods, electrospray ionization (ESI) and graphite assisted laser desorption ionization (LDI), were used in positive and negative ionization mode. Compounds with masses up to 1450 u are observed. The results were evaluated based on the number of formulas in the molecular formula classes and their distribution in double bond equivalents versus carbon number plots (DBE-nC plots). The results from both ionization polarities show significant differences regarding the quality of observed molecular formulas and both ionization methods.

Coupling coal pyrolysis with char gasification in a multi-stage fluidized bed to co-produce high-quality tar and syngas

A multi-stage fluidized bed (MSFB) by configuring the distributor with an overflow standpipe between its neighboring stages was developed to couple the powder coal pyrolysis with its resultant char gasification for co-production of tar and syngas. This work succeeded in the smooth operation of MSFB for coal staged conversion. The three modes of coupling pyrolysis and gasification in terms of the one-stage, two-stage and three-stage bed characterized by temperature drop from the bottom up were investigated to evaluate the quality of the liquid and gas products. Coupling low- and mid-temperature tandem coal pyrolysis with high-temperature char gasification in the MSFB improved the quality of tar and syngas. The obtained tar yield was over 80% of the Gray-King assay tar yield and its light tar fraction (boiling point <360 °C) was as high as 70–80% in the MSFB. Syngas with CH4 content of 5.2 vol.% was produced that was suitable for SNG production. Inside the reactor, the flow direction of pyrolysis volatiles toward the temperature drop avoided the deep secondary reaction of tar. Syngas and steam from the bottom gasification section could contribute to the formation of light tar and CH4 by affecting the top coal pyrolysis. A comparison with the typical pyrolysis processes suggested that the MSFB process had its own advantages in treating powder coal to produce the high-quality tar and syngas.

Thermal Dissolution of Coking Coals in the Anthracene Fraction of Coal Tar

The thermal dissolution of two samples of 1GZhR and ZhR coal in the anthracene fraction of coal tar is studied. The yield of quinoline-soluble products increases considerably in the temperature range of coal softening. Optimal thermal-dissolution conditions are determined for selective production of quinoline-soluble pitch-like products. At 350–380°C, the yield of quinoline-soluble products is 70–73% after 1–2 h. The yields of the distillate fraction and the gas are 0.9% and 0.2%, respectively. The ash-free pitch-like product is a plastic mass with a softening temperature of 76–81°C. It consists mainly of polycyclic aromatic hydrocarbons with a few short alkyl substituents in the aromatic rings. The spatial structure mainly includes poorly structured polycyclic aromatic molecules of the γ component. The proportion of relatively ordered graphitelike packets is 31–37%. Each packet contains five stacked polycyclic aromatic molecules of diameter 17 A. In terms of its composition and plasticity, the product is suitable as a source of alternatives to coal pitch.