Tar Content Research Articles

Application and study on preparation of bio-asphalt by modified phenolic resin from corn straw tar

XPS, GPC, FT-IR, and GC–MS analyses were conducted on corn straw tar and 70# petroleum asphalt. The results indicate that the sulfur content in corn straw tar is lower than that in petroleum asphalt, potentially mitigating the volatilization of harmful substances upon substituting petroleum asphalt. This finding serves as evidence for the substantial presence of phenolic substances in corn straw tar. Upon employing the BOX-Behnken response surface analysis and utilizing resin yield as the evaluation index, the significance of three factors was established as follows: reaction time > phenol molar ratio > straw tar content. Based on the secondary multiple regression model, the optimal conditions for synthetic resin production are a phenolic mole ratio of 0.8, a reaction time of 125 min, and a straw tar dosage of 10 %. An assessment of resin viscosity at different VI temperatures reveals that corn stover tar can partially replace phenol and formaldehyde in the condensation reaction. Additionally, viscosity improvement is observed at elevated temperatures. Thermal gravimetric(TG) spectroscopy indicates lower mass loss in B-PF resin at high temperatures compared to PF resin or corn stover tar. In the evaluation of biological bitumen performance, it is discerned that the mixing amount of the prepared biological bitumen should be controlled at approximately 10 % of its performance. This ensures optimal efficacy without adversely affecting the performance of petroleum bitumen.

Product characterization and pore structure evolution of a tar-rich coal following pyrolysis under nitrogen, steam/nitrogen, and oxygen/nitrogen atmospheres

Steam and an oxidative medium could be the most promising atmosphere for the in-situ pyrolysis of tar-rich coal. This study investigated the influence of these two atmospheres by comparing product yields, tar properties, and pore evolution characteristics of a tar-rich coal following pyrolysis under nitrogen (N2), steam/nitrogen (steam/N2), and oxygen/nitrogen (O2/N2). Compared with N2 pyrolysis, steam/N2 pyrolysis increased the tar yield by 0.54–1.33 wt% at 350–600 °C; further, O2/N2 pyrolysis increased the tar yield from 0.57 wt% to 3.53 wt% at 350 °C while decreasing this value by 0.31–1.83 wt% at 400–600 °C. At 450 °C and 500 °C, steam addition suppressed the formation of oxygenated compounds, thereby decreasing the O/C ratio of tar from 0.099 and 0.088 to 0.073 and 0.074, respectively. Conversely, O2 introduction presented the oxygen addition of tar by oxidation reactions. Meanwhile, steam inhibited the aromatization of alkanes and the condensation of monocyclic aromatic hydrocarbons (MAHs). By contrast, O2 was able to promote the condensation of phenols and MAHs. At 450 °C, steam/N2 was thought to assist in the cracking of the plastic mass by providing a H2-rich atmosphere, which decreased the pitch content of tar and increased the contents of light fractions. O2/N2 was also beneficial for the formation of light fractions by intensifying the thermal cracking effect. Micro-CT and SEM analysis showed that H2O could promote the formation of micro-sized pores within the coal matrix, decreasing the average pore diameter (APD) from 150.95 μm to 102.67 μm and increasing the average coordination number (ACN) of pores from 6.27 to 8.59. O2 was inclined to enlarge the pyrolysis-induced pore network, which imposed a contrasting effect on APD and ACN parameters. Steam is recommended as the preferred atmosphere for the in-situ pyrolysis of tar-rich coal.

Chemical looping reforming of the micromolecular component from biomass pyrolysis via Fe2O3@SBA-16

AbstractTo solve the problems of low gasification efficiency and high tar content caused by solid–solid contact between biomass and oxygen carrier in traditional biomass chemical looping gasification process. The decoupling strategy was adopted to decouple the biomass gasification process, and the composite oxygen carrier was prepared by embedding Fe2O3 in molecular sieve SBA-16 for the chemical looping reforming process of pyrolysis micromolecular model compound methane, which was expected to realize the directional reforming of pyrolysis volatiles to prepare hydrogen-rich syngas. Thermodynamic analysis of the reaction system was carried out based on the Gibbs free energy minimization method, and the reforming performance was evaluated by a fixed bed reactor, and the kinetic parameters were solved based on the gas–solid reaction model. Thermodynamic analysis verified the feasibility of the reaction and provided theoretical guidance for experimental design. The experimental results showed that the reaction performance of Fe2O3@SBA-16 was compared with that of pure Fe2O3 and Fe2O3@SBA-15, and the syngas yield was increased by 55.3% and 20.7% respectively, and it had good cycle stability. Kinetic analysis showed that the kinetic model changed from three-dimensional diffusion to first-order reaction with the increase of temperature. The activation energy was 192.79 kJ/mol by fitting. This paper provides basic data for the directional preparation of hydrogen-rich syngas from biomass and the design of oxygen carriers for pyrolysis of all-component chemical looping reforming.

Analysis and Evaluation of Tar and Nicotin Content in some Cigarette Products of Vietnam in 2023

Tobacco is one of the biggest public health threats facing the world in general and Vietnam in particular. More than 8 million people around the world die from tobacco-related diseases. There are about 70 carcinogens in cigarettes, in addition to addictive, cytotoxic, mutagenic active ingredients,... Among them, Tar and Nicotin are the biggest dangers affecting people health in cigarette smoke. In the study, analysis of Tar and Nicotin content in 166 cigarette samples taken from 10 cigarette manufacturing companies in Vietnam was performed. Analytical results show that Tar content ranges from 1.67 to 15.1 mg/cigarette; Nicotin content ranges from 0.37 to 1.35 mg/cigarette. These results are all lower than the maximum allowable limit according to QCVN 16-1:2015/BYT, but there are some samples with Tar and Nicotin content close to the asymptotic level. This analysis result is also consistent with reports of Tobacco Institute Company Limited in recent years. Although the Tar and Nicotin contents in the samples do not exceed the maximum limit according to QCVN, they are much higher than other countries in the world. Therefore, it is necessary to propose appropriate routes to reduce Tar and Nicotin to ensure the health of users.

Theoretical Calculation of Different Side-Chain Lengths [Cnmim]FeCl4 and Factors Influencing Coal Pyrolysis Swelling Modification.

With the increasing requirements for clean and effective utilization, coal swelling pretreatment provides a good theoretical basis for coal molecular structure, application in coal pyrolysis, and liquefaction. Ionic liquids containing magnetic anionic groups were designed, synthesized, and used as solvents to study the effect on swelling pyrolysis performance. Studies have shown magnetism enhancement with the growth of alkyl chains. The growth of the MIL alkyl side chain made the modification effect of coal more obvious, and the swelling degree showed a trend of first increasing and then decreasing with the increase of temperature and time, and at the temperature of 35 °C, the swelling degree is the largest when the modification time is 8 h. Pyrolysis experiments show that magnetic ionic liquid (MIL) pretreatment can significantly reduce the temperature at the maximum weight loss of coal and increase the tar content of pyrolysis, indicating that MIL plays a catalytic cracking role in coal pyrolysis.

Product distribution and carbon structure evolution characteristics of semicoke from isothermal pyrolysis of Naomaohu coal

Isothermal pyrolysis of Naomaohu coal was carried out at a temperature ranging from 500 to 750 0C using a fixed-bed reactor. The product distributions of gas and tar were measured using gas chromatography and gas chromatography-mass spectrometry, respectively. In addition, the effect of temperature on carbon structure evolution characteristics of semicokes were also investigated. The results showed that the gas yield increased dramatically from 61.50 to 168.43 mL g−1 when the temperature increased from 500 to 750 0C. CO2 and C2-C3 gases were mainly produced during the primary pyrolysis of lower energy chemical bonds at a lower temperature. The tar content ranges from 18.6 to 20.5 wt%, with the highest at 550 0C. At higher temperature, the branched hydrocarbon and phenols can react with each other to produce more polycyclic aromatic hydrocarbon. The infrared absorption peak area associated with the functional groups of O-H, C-H, CO and C-O initially increased with temperature from 500 to 550 0C before sharply decreasing as the temperature increased from 550 to 750 0C. At a higher pyrolysis temperature, the carbon content of the semicoke and the degree of graphite crystalline structure increased. Semicoke produced at higher pyrolysis temperatures exhibited better crystalline behavior and more pores and cracks.

Effect of different digestate biochars as promoters via sludge anaerobic digestion on subsequent pyrolysis products: Focusing on the nitrogen, sulfur, and chlorine releasing characteristics

Anaerobic digestion generates a significant amount of byproduct known as digestate, necessitating resourceful disposal. However, the digestate biochar may exert certain impacts on the pyrolysis of sludge, especially regarding the release of N/S/Cl during the pyrolysis process. This may lead to environmental risks and impose restrictions on the recycling of digestate. There is limited existing research on this topic. In this study, the impact and mechanism of digestate biochar on pyrolysis products were analyzed through kinetic analysis, TG-MS, and Py-GC/MS, with a specific focus on the release characteristics of polluting elements during the pyrolysis process. The findings indicate that the Fe-containing digestate biochar, owing to the larger specific surface area, richer functional groups and catalytic activity associated with Fe3+, enhances the production of C/H/O gases during pyrolysis while reducing the release of NH3, NO2, and H2S. Particularly, Fe-containing digestate biochar significantly enhances the release of Cl-containing gases. The decrease in tar content indicates that Fe-containing digestate biochar promotes the catalytic removal of tar. A comprehensive comparison and analysis of the reaction mechanism were conducted in this study, providing a theoretical basis for the release of pollutants from digestate pyrolysis while enhancing the control and management of pollutants containing N/S/Cl.

Two-stage pyrolysis for effective tobacco stem utilization and tar reduction

Tobacco stem (TS) is a waste product of tobacco industry that cannot be directly disposed of due to regulatory concerns. This study explored a two-stage pyrolysis for modifying the TS structure, rendering it unusable for tobacco products, while preserving potassium and nitrogen in the char for agricultural use as fertilizer. Furthermore, the study aimed to minimize the production of harmful tar by in-situ converting heavy volatiles into gases. The effects of first-stage pyrolysis temperature (400 – 650 °C), second-stage temperature (600 – 800 °C) and various catalysts (β(60 H), HY, HZSM-5 and TiO2) on product distributions and properties were studied. Elemental analysis, FTIR, XRF and ICP-MS were employed to assess the retention of potassium and nitrogen in the char. The results show that under optimal conditions (450 ℃ for pyrolysis and 800 ℃ for cracking), a 40.3 wt% char yield with 93.0 wt% potassium and 50.3 wt% nitrogen retention, 1.8 wt% tar yield and 34.6 wt% gas yield were achieved. The two-stage pyrolysis established a staged temperature profile within the reactor, decoupling the “primary pyrolysis” of TS from the “secondary reaction” of volatiles. In comparison to one-stage pyrolysis, this approach reduced tar production by 89.9% and increased gas production by 51.6%. The use of HZSM-5 and HY catalysts further reduced tar yields by up to 30.9%. This innovative process altered TS structure, retained crucial nutrients in the char, significantly reduced tar content, and mitigated harmful substances such as nicotine and phenols, offering a sustainable solution for tobacco waste management.

Effect of syngas recirculation in the pyrolysis zone on the rice husk gasification process using the downdraft reactor

As one of the world's largest rice producers, Indonesia has an abundance of rice husk as a byproduct of rice milling. Rice husks were utilized to examine downdraft gasification with syngas recirculation system. This study attempts to produce better syngas than conventional downdraft gasifier. With an equivalency ratio of 0.20, syngas was recirculated into the reactor in the pyrolysis zone with valve openings at 25%, 50%, and 75%. This study determined the syngas recycling ratio that maximizes H2 and CO gas and decreases tar. Increasing the syngas recirculation valve (25%, 50%, and 75%) accelerates flame propagation and pyrolysis zone temperature. Syngas study showed no recirculation condition produces the maximum CO2 and CH4. Different recirculation valve openings little affect CO and CH4 gas composition. The H2 gas composition demonstrates that valve openings significantly change H2 gas generation and that the peak was at 50% syngas recirculation. Tar content decreased to 30% and 35% at 50% and 75% valve openings. Based on H2/CO comparison and tar concentration, 50% opening syngas recirculation became the optimum case.

Evaluation of a novel nickel ceramic filter prepared by urea precipitation method for removal of tars from biomass syngas using naphthalene as tar model compound

Gasification has been shown to be an effective thermal conversion process for waste biomass in order to create fuel, specialty chemicals, and hydrogen. Gasification is likely to take on a major role in the near future in the burgeoning hydrogen economy. In order to improve the commercial viability of gasification, catalytic tar reforming has come to the forefront as one of the most promising methods of reducing the tar content that has been detrimental to downstream equipment in the process. The use of catalytic ceramic filters has presented promising potential for this application that can serve dual role of tar and particulate removal. In this study, a nickel-based ceramic filter has been prepared using urea vacuum impregnation technique and evaluated for tar removal efficiencies. The urea technique was more effective than traditional impregnation techniques at uniformly dispersing nickel across the surface of the ceramic filter, driving the nickel particles to penetrate the pores of the support, thus aiding in improved tar removal capabilities. Through steam reforming studies using a naphthalene simulant tar molecule, the 15 wt% nickel filter was able to reduce the naphthalene content by 97% at temperature of 750 °C over 2 h. An activation energy of 126.4 kJmol was achieved for steam reforming using the urea vacuum impregnated catalytic filter compared to 136.4 kJmol using the incipient wetness impregnated filter.

Syngas optimization and tar reduction via multistage catalytic gasification: Effects of catalyst pore, catalyzer stage, and temperature profile

Biomass stands out as a promising availability source of sustainable carbon energy due to its low pollution profile and versatile applications. This study investigates the multistage catalytic gasification (MCG) of coconut shells, employing thermal and catalytic cracking processes in a two-step gasification approach. Local source catalysts, including dolomite, kaolin, and zeolite, were utilized as eco-friendly additives at temperatures ranging from 200 to 300 °C. Zeolite emerged as the most effective catalyst, producing the highest energy content at 6.21 MJ/kg. Conversely, kaolin resulted in higher CO2 emissions. A blend of zeolite and kaolin achieved the highest energy content at 5.43 MJ/kg. However, the combined use of catalysts showed negligible improvements compared to individual catalysts. The study demonstrates that multistage catalytic gasification enhances syngas production and reduces tar content during the gasification of coconut shells. Optimal pyrolysis temperatures were identified within the 500–600 °C range. In conclusion, the introduction of multiple stages in the catalytic cracking process ensures a stable breakdown of hydrocarbon chains, promoting the exposure of gasification products to lighter compounds. Multistage catalytic gasification enhances oxygen supply for oxidation, thereby improving syngas production while mitigating tar and ash content.

The effect of CO2 and a promoter over a Ni-based catalyst on the gas production of toluene as a model tar compound

Catalytic cracking of biomass tar can increase the gas production of biomass gasification and reduce tar content. Taking tar model compound (toluene) as the research object, HZSM-5 as the catalyst carrier, the influence of different Ni loadings, promoters, and CO2 atmosphere on the gas production trend of toluene catalytic cracking was studied. The crystal structure, specific surface area, microstructure and carbon deposition of the catalyst were investigated. When the Ni/HZSM-5 load was 8 wt%, the H2 instantaneous gas production reached highest value. When the load was increased to 10 wt%, catalyst deactivation was delayed, leading to an increase in gas production. With the addition of Ca, Mn and Fe as promoters, Ca decreased the catalytic activity of Ni/HZSM-5, leading to a decrease in H2 instantaneous gas production; however, both Mn and Fe promoted the catalytic activity of Ni/HZSM-5, with Fe resulting in the highest H2 instantaneous gas production. When 20% CO2 was introduced, Ni-Mn/HZSM-5 had the highest catalytic activity and produced the highest H2 content. The characterization of the catalysts showed the addition of CO2 effectively inhibited the formation of carbon deposits, which was beneficial to prolong the catalytic effect and increase gas production.

Two-stage fluidized bed gasification enhanced with oxidative pyrolysis for low-tar producer gas from biomass

Oxidative pyrolysis of fuel was adopted to configure an advanced two-stage fluidized bed gasification system, aiming to produce low-tar producer gas efficiently. A series of tests were carried out to investigate the effect of oxygen allocation in supply on gasification of pine chips in terms of both efficiency and producer gas quality. Compared with the case without pre-oxidation, coupling oxidative pyrolysis increased gas volume fraction of CO, CH4, and CnHm while decreasing that of CO2 and H2 in the produced gas. Further analysis showed that adopting oxidative pyrolysis reduced fuel gas yield, but the tar in the produced gas was lighter. The generated tar is easily transformed into small-molecule combustible gas by the catalytic action of hot char, thus increasing the calorific value of product gas. The long-term operation of the pilot plant presents a great steady continuous running with a minimum tar content in the producer gas of 1.3 g/Nm3. The above-mentioned results thus well verified the technical advantage and feasibility of the two-stage fluidized bed gasification with oxidative pyrolysis.

Thermal Decomposition and Kinetic Parameters of Three Biomass Feedstocks for the Performance of the Gasification Process Using a Thermogravimetric Analyzer

Thermogravimetric analysis (TGA) is a powerful technique and useful method for characterizing biomass as a non-conventional fuel. A TGA apparatus has been utilized to experimentally investigate the impact of biomass feedstock diversity on the performance of the gasification of hardwood (HW), softwood (SW) pellets, and refuse-derived fuel (RDF) materials. The solid conversion rate and the volatile species formation rate have been estimated to quantify the rates of devolatilization for each material. In addition, the combustion kinetic characteristics of the three biomass feedstocks were investigated using TGA at different heating rates, and a thermal kinetic analysis was conducted to describe the gasification process. Therefore, the kinetic parameters have been evaluated for different thermal reactions and non-isothermal kinetic models that depend on the relationships between heating rates and temperature profiles. The results show that the amount of tar content from the RDF was higher than that of pure hardwood and softwood feedstocks. Hence, tar removal must be part of any process using syngas produced from RDF feedstocks in a gas engine to produce electricity.

Gasification of Egusi Melon (Citrullus lanatus) Shell over a Novel Ni/dolomite/MgO/[formula omitted]Al2O3 Catalyst for the Production of H2-rich gas

Hydrogen-rich gas was produced from Citrullus-lanatus in a fixed-bed reactor using a novel Ni/dolomite/MgO/γ−Al2O3 with air-steam mixture as the gasifying agent. The feed and steam-air flow rates were 3 and 0.8 kg/h with fixed steam-air volume-concentration of 40% v/v. The results displayed a high cracking activity of the hydrocarbons/tar in the biomass by the catalyst with a resultant upgrade in the gas quality/H2 yield. The highest H2 yield was 66.1 g/kg biomass, a minimal tar concentration of 2 g/Nm3 with steam-to-biomass ratio of 2 at 1100 °C. The highest H2 yield (57 vol%) was achieved at 0.28 equivalence ratio.

Carbon dioxide-steam reforming gasification of carbonized biomass pellet for high syngas yield and TAR reduction through CFD modeling

Experimental and numerical evaluation of steam and carbon dioxide gasification on torrefied palm kernel shell in an updraft fixed bed gasifier is studied. Euler-Lagrangian two-dimensional model with 15 kinetic reactions is developed to investigate tar formation in relation to torrefaction temperature, gasification temperature, and steam-to-carbon-dioxide ratio (S-CO2-R). The combination of steam and CO2 had considerable effect on the tar reduction and also influenced the gaseous composition significantly when the varying parameters were compared. The results show that increasing both gasification temperature and S-CO2-R do enhance the H2 production whiles drastically reducing the tar formation. The tar concentration reduced by 21.4 % and 20.5 % by changing the S-CO2-R from 0.4 to 2.0 and gasification process temperature from 973 and 1173 K respectively. An increase in hydrogen is also observed, from 55.5 % to 60.84 %, when the S-CO2-R is increased to 1.2. Similarly, 29.1 % increase is observed in gasification efficiency as compared to the raw-PKS.

Tar Formation in Gasification Systems: A Holistic Review of Remediation Approaches and Removal Methods.

Gasification is an advanced thermochemical process that converts carbonaceous feedstock into syngas, a mixture of hydrogen, carbon monoxide, and other gases. However, the presence of tar in syngas, which is composed of higher molecular weight aromatic hydrocarbons, poses significant challenges for the downstream utilization of syngas. This Review offers a comprehensive overview of tar from gasification, encompassing gasifier chemistry and configuration that notably impact tar formation during gasification. It explores the concentration and composition of tar in the syngas and the purity of syngas required for the applications. Various tar removal methods are discussed, including mechanical, chemical/catalytic, and plasma technologies. The Review provides insights into the strengths, limitations, and challenges associated with each tar removal method. It also highlights the importance of integrating multiple techniques to enhance the tar removal efficiency and syngas quality. The selection of an appropriate tar removal strategy depends on factors such as tar composition, gasifier operating and design factors, economic considerations, and the extent of purity required at the downstream application. Future research should focus on developing cleaning strategies that consume less energy and cause a smaller environmental impact.

Catalytic gasification of municipal solid waste using eggshell-derived CaO catalyst: An investigation of optimum H2 production, production distribution, and tar compounds

This study reports the optimum hydrogen (H2) production from municipal solid waste (MSW) via waste eggshell derived-CaO catalyst through gasification technology. The response surface model was applied to design the experiments and the data validation. Results showed that CaO catalyst had a better performance that enhanced 15 mol% more H2 production than non-catalytic gasification by mainly involving reaction temperature and catalyst loading as the critical parameters. Tar content was efficiently declined from 11.34 wt. % to 4.7 , wt. %, which ultimately elevated the H2 and syngas from 33.95 mol% to 51.27 mol% and 74.05 to 83.4674.05–83.46 wt. %, respectively. The model showed a strong interaction among the statistical parameters verified through the regression values; R2 = 0.990, P-value = 0.000005, respectively. Scanning electron microscopy, X-ray diffraction, and Brunauer-Emmett-Teller techniques investigated the catalyst's structure hence; presented comparable results. From tar analysis, the aromatics were found as the dominant family followed by polycyclic aromatic, phenyls, aliphatic, aromatic heterocyclic, polycyclic, and aromatic ketones. Optimum H2 production of 51.27 mol% (with H2/CO ratio 2.82, LHV 9.47 MJ/Nm3, and H2 yield 22.74 mol kg-MSW−1) was produced which can be a better alternative to depleting fossil fuels and utilized for liquid fuel manufacturing and power generation.

Novel selective adsorption cooling materials for heating cigarettes

Heated cigarettes are becoming trendy due to their advantage of not burning the tobacco material and thus reducing the amount of harmful ingredients released, while being able to leave the nicotine and tar content of the smoke untouched. However, the high temperature of the smoke as it enters the human mouth can affect the user experience. Therefore, the development of adsorption cooling materials for use in heated cigarettes is gradually becoming a hot topic. In this work, an adsorption cooling material based on embossed rod powder was prepared. It was found that compared with the commercial Yoga cooling material, the embossed rod powder based adsorption cooling material was able to reduce the maximum smoke temperature to 45.16 °C. In addition, it reduced the adsorption of nicotine by the cooling material, and increased the glycerol and nicotine content in the cooled smoke, which effectively promoted the taste of the smoke. Furthermore, the molecular simulation results found that the higher specific surface area and rich microscopic pore structure could increase the heat conduction area of the high-temperature flue gas, which enhanced the heat transfer effect of the flue gas. Finally, the periodic characteristic velocity pulsation destroyed the boundary layer formed by the fluid in the wall region, which increased the convective heat transfer effect between the fluid and the particles. The optimum sample 03 had the largest specific surface area and the lowest crystallinity, and thus had the best cooling effect. This work could provide some reference significance for the development of cooling materials for heating cigarettes.

STUDY ON THE PROCESS OF GASIFICATION OF BLACK LIQUOR

This review paper describes the potential of developing a new lignocellulosic biorefinery concept integrated with the Kraft industry. To demonstrate that gasification is a sustainable and more valuable processing route than burning it in recovery boilers, additional processes of syngas cleaning and high sulfur recovery are required in order to achieve a significant reduction in operating costs to improve economic feasibility through BL gasification. BL gasification is performed using two types of gasifiers, one with a fluidized bed, which requires a higher air velocity to increase the yield of valuable products aiding to increase the calorific value of the produced gas compared to fixed bed gasifiers. Fixed-bed gasifiers produce gas with a high tar content because the heat and mass transfer between the gasifier and the biomass is low and non-uniform. BL gasification offers great potential for increased energy recovery with a reduced amount of emissions compared to that of conventional BL burning in recovery boilers.