Mixture Of Coal Tar Research Articles

Evaluation of the electrical properties of carbon electrodes developed with bio-material additions as a sacrificial anode in cathodic protection

The use of zinc and magnesium sacrificial anodes for the protection of steel structures in cathodic protection techniques have been widely accepted but longevity and environmental friendliness of these materials in service still needs to be improved. Thus, the need to continually develop anodes that can potentially serve the same purpose and/or better performance. This work is a feasibility study on the production of carbon electrodes for possible application as sacrificial anodes for the cathodic protection of mild steel. The main aim of this investigation is to develop an electrode from carbon-based materials with a view to producing anodes that can potentially replace zinc and magnesium electrodes for cathodic protection of low-carbon steel. The electrodes were developed using mixture of coal, charcoal, mill scale, wood dust and coal tar (binder) that were heated and compressed in a metal die. The current passing through the electrodes was measured with the resistance, resistivity and conductivity determined, including the current densities (Iρ) which gives an indication of the electrochemical behavior of the electrodes. Morphology of the electrodes were examined by optical microscope (OM) and scanning electron microscope (SEM) to assess the influence of porosities of the electrodes produced. Based on these findings, it was generally observed that the conductivity increases from 5.23E-4 S/m to 5.87E-3 S/m for 150 µm and 600 µm particle sizes, respectively. Generally, resistivity increases with an increase in the amount of wood dust in the carbon anodes developed. The carbon electrode of 600 µm particle size with the composition of 67 wt% coal, 5 wt% charcoal, 10 wt% coal tar, 10 wt% mill scale and 8 wt% wood dust had the best current density that could offer corrosion protection for mild steel.

Thermokinetic parameters of the primary coal tars destruction in the presence of catalysts and polymeric materials

The hydrogen-donor abilities of polymers and the activity of catalysts in the process of thermal destruction of the organic mass of primary coal tar (PCT) are studied by non-isothermal kinetics methods. PCT,magnetic microspheres, nickel-deposited chrysotilechrysotile and Fe3O4nanocatalysts were used as initial raw materials. Рolymers such as polyethylene (PE), polystyrene(PS) and polyethylene glycol (PEG) were selected as a hy-drogen donor. The phases Mg3[OH]4{Si2O5} and NiO were determined by X-ray phase analysis (XRD) in the obtained catalyst (nickel-deposited chrysotile), and the presence of highly dispersed nickel oxide particles on the surface and inside the nanotubes was shown by the transmission electron microscope (TEM). Nickel oxide particles of 8–11 nmand 30–37 nmwere evenly distributed on the surface and inside the chrysotile nanotubes. The kinetic parameters of the thermal destruction of a mixture of PCT, catalyst and polymer material were determined on the basis of thermogravimetric analysis using the integral method and the method for determin-ing the thermokinetic parameters by the inflection point on the thermogravimetric curve(TG). The change in the activation energy, rate constant and pre-exponential factor with an increase in the degree of destruction of the organic mass of the PCT is established. It was shown that the nature of polymers and catalysts significantly affects the value of the rate constant and the activation energy. The calculated activation energies of the thermal destruction of a mixture of coal tar with PS and PE in the presence of a catalyst (nickel-deposited chrysotile) by the first method are 47.6 kJ/mol and 40.4 kJ/mol, and by the second method are 47.3 kJ/mol and 86.5kJ/mol respectively.

Thermal Decomposition of a Mixture of Tar with Primary Coal Tar with the Additives of Iron Compounds

Studies on the thermal destruction of a mixture of vacuum residue (tar) and primary coal tar (PCT) with and without Fe3O4 and β-FeOOH catalytic additives, which were performed using thermogravimetry and differential scanning calorimetry in an inert atmosphere at a heating rate of 10 K/min, are reported. Based on the results of thermogravimetric analysis and the kinetic parameters of the process, activation energies were calculated, and these activation energies can be used in the development of methods for the technological calculation of reactors and the selection of construction materials for their manufacture.

Pyrolysis of scrap tyres pretreated by waste coal tar

For disposal of scrap tyres, there have been a lot of studies done by previous researchers, but it yet remains a longstanding challenge in practice. To find a solution for this problem, the feasibility of a proposed approach in a laboratory scale was tested. The pyrolysis of scrap tyres pretreated by waste coal tar (noted as “as-pretreated” tyres) was performed in a batch reactor at atmospheric pressure. Waste coal tar was used to modify the scrap tyres to improve the pyrolysis efficiency of scrap tyres input and the quality of the product tar. The swelling behavior of scrap tyres soaked in waste coal tar at 10 °C, effect of pyrolysis temperature on the product yields, and the synergies during pyrolysis of the as-pretreated tyres and co-pyrolysis of scrap tyres/waste coal tar mixture were all investigated in detail. The results observed found that by comparison of the calculated yields and the observed experimental yields for pyrolysis products, the synergy from co-pyrolysis of scrap tyres/waste coal tar mixture boosted the gas yield without increasing the tar yield. In contrast, the synergy during pyrolysis of the as-pretreated tyres could enhance the tar yield, but reduced the gas and char yields. According to the distillation range analyses of the tar, more light fractions were found in the tar from pyrolysis of the as-pretreated tyres, in which the gasoline fraction, diesel fraction and kerosene fraction were 38.4 wt%, 46.8 wt% and 50.2 wt%, respectively. This work is expected to be helpful in further use of scrap tyres.

Composition and Structural Characterization of the Extractive Pitches as Compared with the Commercial Reference Pitches of Different Origins

The chemical and group composition, the empirical properties and the molecular structural characteristics of the extractive pitches produced by thermal dissolution of three medium-ranked coals were studied in comparison with the reference commercial pitches including typical coal-tar pitch, petroleum-derived pitch and the pitch sample derived from the blended mixture of coal tar with petroleum feedstock. The structural parameters of the average pitch molecules have been compared based on the 1H and 13C NMR spectra. It was shown that, in terms of chemical composition and empirical properties including carcinogen content, the extractive pitches resemble blended pitch sample, the structural parameters being close to commercial coal-tar pitch sample. The average pitch molecule of extractive pitches was composed of predominantly aromatic nuclei with rather pericondensed structure.

Comparative Study of the Properties of the Coal Extractive and Commercial Pitches

Three extractive pitches were produced by using thermal dissolution of the medium-ranked coals at 380 °C in anthracene oil. The empirical properties such as the chemical composition, solubility in quinoline and toluene, softening point, and content of carcinogenic polycyclic hydrocarbons, and also molecular and structural parameters of the extractive pitches were characterized in comparison with three commercially available pitches, including typical coal-tar pitch, petroleum-derived pitch, and blended pitch derived from the mixture of coal tar with petroleum feedstock. The molecular and structural properties of pitches were studied using FTIR, 1H and 13C NMR, and XRD techniques. It was shown that the average molecule of the extractive pitches was composed of predominantly aromatic rarely substituted pericondensed nuclei, such as that in coal-tar pitch. The spatial structures of both the extractive and reference pitches consisted of predominantly disordered carbon matter with a small amount of rather ordered nanosized “graphite-like” stacks. In terms of the technical specifications, the extractive pitches irrespective of the coal used met the requirements for the pitch binder and resembled commercial blended petro-coal-tar pitch. A remarkable merit of the extractive pitches compared to coal-tar pitch was low carcinogenicity (two to three times as low).

In English

Fractal structures are common in nature, and the structures that play a role in the formation of macroscopic systems, as well as represent new structures characterized by dramatic changes in the physical properties. The aim of this work is to determine the dimensions of fractal carbon structures using electron microscopy and provision characteristics of fractal carbon structures by calculating the fractal dimension. The feedstock for fractal structures in an arc discharge is a mixture of pyrolytic carbon and coal tar. The fractal carbon structures has been systematically studied by scanning electron microscopy (SEM) and transmission electron microscopy. The SEM observation shows quite a large range of sizes of fractal clusters and aggregates. The TEM analysis reveals formation of carbon nanoparticles in a narrow range of 2–8 nm. The results show that the fractal structure of the carbon deposits are volumetric fractals with dimension of carbon deposits of 2.96. Volume fractal structure consisting of fractal aggregates, the cloud formations, and the like ones having a similar structure may be formed of different materials - graphite and pyrolytic carbon. A necessary condition for the nucleation of carbon nanostructures is the formation of carbon nanoparticles in an arc discharge.

Benefits of ultrasound in pitch production from coal tar and its mixtures with styrene distillation residue

Ultrasound treatment of coal tar increases the yield of pitch by a factor of 1.5 in subsequent oxidation by atmospheric oxygen. The yield of pitch may be regulated in terms of its softening temperature by changing the oxidation time. To obtain standard pitch, the following conditions are employed: ultrasound treatment for 3 h; initial oxidation temperature 260–270°C; final oxidation temperature 360–370°C; rate of air supply 63 L/h; oxidation time ~30–70 min, depending on the requirements on the final product. The concentration of aromatic derivatives of benzo[a]pyrene type in the pitch produced and in the liquid fraction (which may be used as a fuel) is considerably less than in the current industrial method. After ultrasound treatment, a 1: 1 mixture of coal tar and rectification residues from styrene yields pitch with satisfactory characteristics on oxidation by atmospheric air. That expands the range of raw materials for pitch production.

Attempts to produce blast furnace coke from Victorian brown coal. 2. Hot briquetting, air curing and higher carbonization temperature

Attempts have been made to obtain a substitute for blast furnace (BF) coke from a Victorian brown coal mixed with a tar derived from brown coal under conditions sufficiently mild to be economical. Changes to the procedure used in a previous attempt include hot briquetting of the coal–tar mixture at 150°C rather than ambient, the addition of air curing at 200°C and carbonization at higher temperature, 1200°C, rather than 900–950°C. All these changes led to a decrease in reactivity and increase in compressive strength. In addition, the higher carbonization temperature led to a decrease in surface area. Thus the combined changes led to an increase in strength and decrease in reactivity and surface area. This is the first time a carbonized product has been prepared from brown coal in good yield and of lower reactivity than brown coal char when compared with BF coke. However, the reactivity and surface area remain too high for the product to be used as a substitute for BF coke.

Dissolution and transport of coal tar compounds in fractured clay-rich residuum

We investigated the dissolution and transport of organic contaminants from a crude coal tar mixture in a monolith of fractured clay-rich residuum. An electrolyte solution was eluted through the residuum monolith containing a small emplaced source of coal tar under biologically inhibited and mildly acidic conditions. Concentrations of 10 coal tar compounds, representing mono-, poly-, and heterocyclic aromatic hydrocarbons that constitute crude coal tar were monitored in the effluent over a period of 377 days. Most compounds appeared in the effluent within the first 0.1 pore volume eluted indicating the importance of rapid dissolution and transport through the fracture networks. The concentrations continued to rise but did not reach the corresponding effective solubility limit in most cases. Compounds that were less soluble and those that were more susceptible to sorption or matrix diffusion eluted at a much slower rate. Analysis of contaminant concentrations in microcore residuum samples indicated that all 10 compounds had spread throughout the entire monolith and had diffused into the fine-grained matrix between fractures. These data suggest that the predominantly fine pore structure did not appear to inhibit coal tar dissolution and subsequent transport, even though only a small portion of tar was in direct contact with fractures and macropores that control most flow.

Study of PAH dissipation and phytoremediation in soils: Comparing freshly spiked with weathered soil from a former coking works

A comparison was made between the dissipation of polycyclic aromatic hydrocarbons (PAHs) in soil freshly spiked with pure PAHs, soil spiked with a coal tar mixture and a contaminated soil from a former coking works where the PAHs had been present for more than a century. The potential of five selected plant species for phytoremediation was investigated. The levels of all 7 PAHs in chemically amended soil, both planted and unplanted, fell significantly (>80% reduction) over the 12 weeks of the growing trial. In the coal tar treated soils all PAHs were significantly reduced. In both the planted and unplanted soils the 2–3 ringed compounds demonstrated much greater loss (>77%) than the 4–6 ringed (16–39%). The 3–4 ringed compounds demonstrated strong evidence of phytoremediation but not the 5–6 ringed. The coking soil showed limited reduction (7–24%) of all 12 PAHs present. There was little difference in dissipation between the PAHs and little evidence of a phytoremediation effect in coking soil. The results demonstrated that the form in which PAHs were added to soil influenced their susceptibility to dissipation. Therefore, predictions of PAH dissipation from laboratory amended soil do not reflect the true situation in the field.

Coke quality on adding coking byproducts to the batch

Conditions for the granulation and heat treatment of coking byproducts—heavy coal tar, acid tars, and distillation residues—are developed so as to produce suitable additives for coking batch. It proves possible to improve poorly clinkering batch by adding a mixture of coal and acidic tar from the sulfate department.

Influence of carbon structure of the anode on the production of graphite in single-walled carbon nanotube soot synthesized by arc discharge using a Fe–Ni–S catalyst

We investigated the production of the graphite contained in the soot of single-walled carbon nanotubes (SWCNTs) synthesized using the arc discharge method with a poorly graphitized carbon (PGC) rod in comparison to a graphite rod. A PGC rod was produced using a mixture of coal tar and carbon black and was heat treated to 1000 °C. The rod was packed with a mixture of iron (Fe), nickel (Ni), sulfur (S), and PGC and used for the production of SWCNT soot using arc discharge. From the results of X-ray diffraction and electron microscopy, the amount of graphite in the SWCNT soot synthesized by PGC rod was lower than that by graphite rod. The production of graphite in the soot was found to be dependent on the carbon structure of the anode and the current density of arc discharge.

Activation of group IVC phospholipase A2 by polycyclic aromatic hydrocarbons induces apoptosis of human coronary artery endothelial cells

Exposure to environmental pollutants, such as polycyclic aromatic hydrocarbons (PAHs) found in coal tar mixtures and tobacco sources, is considered a significant risk factor for the development of heart disease in humans. The goal of this study was to determine the influence of PAHs present at a Superfund site on human coronary artery endothelial cell (HCAEC) phospholipase A(2) (PLA(2)) activity and apoptosis. Extremely high levels of 12 out of 15 EPA high-priority PAHs were present in both the streambed and floodplain sediments at a site where an urban creek and its adjacent floodplain were extensively contaminated by PAHs and other coal tar compounds. Nine of the 12 compounds and a coal tar mixture (SRM 1597A) activated group IVC PLA(2) in HCAECs, and activation of this enzyme was associated with histone fragmentation and poly (ADP) ribose polymerase (PARP) cleavage. Genetic silencing of group IVC PLA(2) inhibited both (3)H-fatty acid release and histone fragmentation by PAHs and SRM 1597A, indicating that individual PAHs and a coal tar mixture induce apoptosis of HCAECs via a mechanism that involves group IVC PLA(2). Western blot analysis of aortas isolated from feral mice (Peromyscus leucopus) inhabiting the Superfund site showed increased PARP and caspase-3 cleavage when compared to reference mice. These data suggest that PAHs induce apoptosis of HCAECs via activation of group IVC PLA(2).

Application of the margin-of-exposure (MoE) approach to substances in food that are genotoxic and carcinogenic e.g.: Benzo[a]pyrene and polycyclic aromatic hydrocarbons

Benzo[a]pyrene (BaP) and a number of other polycyclic aromatic hydrocarbons (PAH) are mutagenic and are also carcinogenic in rodent bioassays. Oral carcinogenicity data are not available for individual PAH other than BaP, and so BaP has been used as a marker of the carcinogenicity of, and exposure to, PAHs. Carcinogenicity studies of coal tar mixtures, considered to be representative of the genotoxic and carcinogenic PAH in food, have been used for dose-response modelling. Modelling the number of tumour-bearing mice resulted in a BMDL 10 of 0.122 mg BaP/kg-bw/day, which was lower than that for any of the individual tumours and was considered to be most appropriate since the different PAH may have different mechanisms of carcinogenicity. An average dietary exposure estimates of 0.008 μg BaP/kg-bw/day was identified from the range of national estimates. The calculated MoE was 15,000.

Effect of coal rank on the properties of coal-based activated carbon honeycomb monoliths

Activated carbon honeycombs (ACHs) were prepared by extrusion of honeycombs from a mixture of coal, coal tar, bean oil, methylcellulose and water, followed by carbonization and steam activation. Three Chinese coals, Qujing, Shenfu and Datong, were used as carbon precursors. The ACH monoliths obtained were characterized by N2 adsorption,thermo-gravimetry and compression tests. Results show that both coal rank and activation time have great a impact on the pore size distribution and mechanical strength. The ACHs from Datong obtained under optimum conditions have the highest BET surface area(884m2/g), the highest ignition temperature (535℃) and the highest mechanical strength(13MPa) among the three coals. The mechanical strength of the ACH monoliths decreases with increasing macro-pore volume. The ignition temperature is hardly affected by ash content but decreases with increasing volatile content.

Material Properties of Coal-Tar Emulsion Sealers

Coal-tar emulsion sealers are used to protect hot-mix asphalt pavements from damage due to the spillage of petroleum-based materials. This paper contains the results of a study, which has field tests and laboratory tests, concerning the effect of various amounts of aggregate, temperature variations, a polymer additive, and aging on the material properties of coal-tar emulsion mixtures. The material properties tests included thermal expansion, creep stiffness test, and by measuring tensile strength, the stress-strain relationships. The study results indicate that the thermal expansion of the mixtures increased with increasing amounts of coal-tar emulsion; however, this effect was slightly reduced with the addition of a polymer additive. Creep stiffness values increased with age and increasing amounts of aggregate in the mixture. The results of the stress-strain evaluation were not consistent. Increased amounts of aggregate, lower temperatures, and decreased amounts of polymer generally resulted in greater stress levels being achieved prior to failure.

Application of benzo(a)pyrene and coal tar tumor dose-response data to a modified benchmark dose method of guideline development.

Assessment of cancer risk from exposure to polycyclic aromatic hydrocarbons (PAHs) has been traditionally conducted by applying the conservative linearized multistage (LMS) model to animal tumor data for benzo(a)pyrene (BaP), considered the most potent carcinogen in PAH mixtures. Because it has been argued that LMS use of 95% lower confidence limits on dose is unnecessarily conservative, that assumptions of low-dose linearity to zero in the dose response imply clear mechanistic understanding, and that “acceptable” cancer risk rests on a policy decision, an alternative cancer risk assessment approach has been developed. Based in part on the emerging benchmark dose (BMD) method, the modified BMD method we used involves applying a suite of conventional mathematical models to tumor dose–response data. This permits derivation of the average dose corresponding to 5% extra tumor incidence (BMD0.05) to which a number of modifying factors are applied to achieve a guideline dose, that is, a daily dose considered safe for human lifetime exposure. Application of the modified BMD method to recent forestomach tumor data from BaP ingestion studies in mice suggests a guideline dose of 0.08 μg/kg/day. Based on this and an understanding of dietary BaP, and considering that BaP is a common contaminant in soil and therefore poses human health risk via soil ingestion, we propose a BaP soil guideline value of 5 ppm (milligrams per kilogram). Mouse tumor data from ingestion of coal tar mixtures containing PAHs and BaP show that lung and not forestomach tumors are most prevalent and that BaP content cannot explain the lung tumors. This calls into question the common use of toxicity equivalence factors based on BaP for assessing risk from complex PAH mixtures. Emerging data point to another PAH compound—7H-benzo(c)fluorene—as the possible lung tumorigen.

Cancer risk assessment for oral exposure to PAH mixtures.

Cancer risk estimates for oral uptake of polycyclic aromatic hydrocarbons (PAHs) currently are based on risk estimates for benzo[a]pyrene (BAP). The potency of PAH mixtures often is calculated using relative potency values (BAP equivalency factors). We used recent oral carcinogenicity studies with BAP and coal tar mixtures, as well as older studies for a critical reappraisal of the current practice. A literature survey identified several carcinogenicity studies with oral and dermal exposure and lung implantation that allow a direct comparison of the carcinogenic potency of pure BAP and PAH mixtures. Moreover, when the PAH composition of the mixture has been analysed, prediction of the potency of PAH mixtures by BAP equivalency factors could be compared with the observed PAH potency. The analysis indicates that BAP equivalency factors do not describe adequately the potency of PAH mixtures and lead to underestimations of carcinogenic potency in most cases. Evaluation of several studies with various PAH mixtures revealed that the potency ratio between pure BAP and the PAH mixture in the same assay is highly dependent on the exposure pathway and the target organ, therefore potency estimates for PAH mixtures should be derived separately for oral, dermal and inhalative exposure using data from studies with the relevant pathway. A cancer slope factor for oral PAH exposure was derived based on data from a recent feeding study with coal tar mixtures. By using incidence data for all exposure-related tumours, a slope factor for humans of 11.5 (human excess risk per oral lifetime exposure with 1 mg BAP kg(-1)day(-1) in a PAH mixture) was obtained. Our analysis led to the conclusion that the contribution of BAP to the carcinogenic potency of the mixture depends on the exposure pathway and type of cancer observed but is relatively constant for various PAH mixtures from industrial sources. Thus, the derived oral slope factor is recommended to be used for the risk assessment of PAH-contaminated soils.

Magnetic Resonance Imaging of Hydrocarbon-Contaminated Porous Media

Nuclear magnetic resonance response measurement is a nondestructive and nonintrusive technique, which is potentially useful for in situ characterization, mapping, and diagnostic purposes in hydrocarbon-contaminated subsurface, including rock. Magnetic resonance measurements of a porous medium allow the determination of necessary parameters to evaluate permeability and porosity of the medium and the type of hydrocarbons present in the pore fluid. This information is of particular importance in evaluation of hydrocarbon transport in contaminated soils. This paper presents the results of a preliminary study intended to evaluate the robustness of the magnetic resonance imaging technology using well-characterized laboratory specimens of porous material containing hydrocarbon liquids. First, a dry uniform sand pack impregnated with an aqueous coal tar mixture was imaged to evaluate discernable hydrocarbon distribution in the pore space of the sand column. Then, packed columns of glass beads of various sizes, permeated with distilled water and trichloroethylene, were imaged. The discernable images of the pore space and the interface of the two liquids in the pore space indicated that magnetic resonance imaging could be a viable tool to determine spatial distribution and mass fraction of hydrocarbon liquids in contaminated subsurface.