Gaseous products evolution during microwave pyrolysis of tire powders

Microwave pyrolysis of tire powders were run in a laboratory scale microwave oven (2.45 GHz). A special attention was dedicated to the yields of gaseous products during the microwave pyrolysis at different powers (300, 500, and 700 W). Triple-channel refinery gas chromatograph was used to quickly detect the gas composition of tire pyrolysis and its evolution during the process. H₂, CO, and CH₄, up to 90% of the total volume of pyrolytic gases, were the most predominant gaseous products. As the pyrolysis proceeded, the composition exhibited a significantly changes, e.g., more H₂ was produced and less CH₄ was generated. As the power increased, the content of CH₄ + CO₂ decreased, while the fractions of H₂ + CO rapidly increased at the intense stage of the microwave pyrolysis. The maximum yields of gaseous and liquid products and the maximum conversion of tires were obtained at 500 W.     

Fuel gas production from dusty tar pyrolysis

Dusty tar is an undesired product obtained from a coal pyrolysis/combustion system. Thermal conversion of dusty tar into fuel gas was studied with a fixed-bed reactor. It is found that C₂-C₅ hydrocarbons are mainly derived from the cracking of long-chain aliphatics, while CH₄ from the decomposition of long-chain aliphatics and alkyl-substituted aromatic chemicals. The yield of the gas product increases monotonously, but the heating value of gas gradually decreases as temperature increases from 400 to 950°C. Decomposition of chemicals with a boiling point over 360°C contributes to 50–90% C₁-C₅ hydrocarbons and CO_x when pyrolysis temperature is lower than 600°C.     

Dry reforming of model biomass pyrolysis products to syngas by dielectric barrier discharge plasma

Biomass is frequently used to produce CO and H₂ together with undesirable by-products containing CO₂ and liquid tar by pyrolysis and gasification. This leads to decreased energy efficiency and increased maintenance costs. This study investigated the reforming of biogas and tar, respectively, using non-thermal plasma featuring dielectric barrier discharge (DBD). The gas surrogates studied were CH₄ and CO₂, and toluene was used as a substitute for tar. During reforming of biogas, CO or H₂ was added to the CH₄ and CO₂ to investigate their effects on CH₄ and CO₂ conversion. Both the discharge power and gas components influenced the conversion of CH₄ and CO₂. The conversion efficiency of CH₄ and CO₂ and the selectivity of H₂ and CO both increased with the discharge power while reforming the mixture of CH₄ and CO₂. The maximum conversion efficiency of CH₄ and CO₂ and selectivity of CO and H₂ were obtained with a CH₄:CO₂ ratio of 1:2. During reforming of toluene, the conversion efficiency of toluene reached a maximum value of 90% and the production yields of H₂, CO, and CO₂ reached respective maximums of 0.79, 2.24, and 1.51 mol/mol-toluene at a discharge power of 90 W and temperature of 300 °C. Higher temperatures of 400–500 °C did not favour toluene destruction due to the thermal breakdown of the quartz dielectric and the rapid decrease in the discharging intensity. In addition, reaction mechanism for reforming of both biogas and toluene was proposed to improve our understanding of the reforming process in DBD plasma.     

Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield

The thermal decomposition of coal was the essential step of many reactions, thus it was widespread concerned. In order to investigate the behaviors and kinetics of coal pyrolysis, coal samples which obtained from Ningdong coalfield of China were pyrolyzed with a tubular furnace in argon atmosphere at the heating rate of 5 K min^?1. The primary gaseous products including CH₄, H₂, N₂, CO, CO₂, C₂H₄ and C₂H₆ were quantified using a gas chromatogram. It can be seen that with the temperature increasing, the yields of H₂ and CO increased, while the others decreased. In order to produce possibly much tar, the optimal temperature was 923 K. The characteristic of pyrolysis kinetics was determined by thermo gravimetric analysis measurement. The Coats–Redfern and Flynn–Wall–Ozawa methods was used to obtain kinetic parameters. The activation energy range of 50–200 kJ mol^?1 was determined.     

A strategy for regulating the performance of DCFC with semi-coke fuel

To explore the correlation between the performance of direct carbon fuel cells and the characteristics of semi-coke as the fuel, a strategy for adjusting the characteristics of semi-coke is employed by changing the coal pyrolysis conditions. It is found that the ratios O/C and H/C of semi-coke are decreased with an increase in the final pyrolysis temperature, a slowing of the heating rate and an extension of the pyrolysis residence time. In addition, CO₂ activation can increase the specific surface area of semi-coke. The performance of a direct carbon fuel cell increases with an increase in O/C and H/C in semi-coke. Meanwhile, the combustion characteristic index of semi-coke has a linear correlation with the maximum output power of a direct carbon fuel cell, so the combustion characteristic index can be used as a reference indicator for a direct carbon fuel cell to select solid carbon fuel.     

Pyrolysis of pressure-sensitive adhesive wastes in a fixed-bed reactor

Pyrolysis of pressure-sensitive adhesive (PSA) wastes have been investigated in a fixed-bed reactor with a heating rate of 20°C/min. PSA pyrolysis mainly occurs between 300 and 600°C. The maximum liquid yield was obtained at 550°C with a yield of 55.69%. Liquid product can be used as fuel or raw material for purifying 2-ethyl-1-hexanol, dehydroabietic acid, 2,4-dimethyl-1-heptene, and styrene. The main composition in gas is CO and CO₂, followed by CH₄ and H₂. High content of ash in char limits the application in fuel, but might be used as an adsorption material after upgrading.     

Characteristic and utilization of pyrolysis productions from Dianchi Lake’s sediment in Yunan province in China

In the process of pyrolysis of Dianchi Lake’s sediment, a large number of productions (including gas state, liquid state, and solid state) were obtained. This research analyzed the characteristics and utilization of the representative pyrolysis products by gas chromatography, gas chromatograph-mass spectrometer, Brunauer–Emmett–Teller measurements, and X-ray fluorescence methods. The main gas components were H₂, CO, CH₄, CO₂, C₂H₄, and C₂H₆ in pyrolysis productions of the Dianchi Lake’s sediment. The flammable gases, H₂, CO, and CH₄, were vastly generated at the high-temperature section (>800°C). The main liquid components of pyrolysis products were phenol and hydroxy derivatives, which have no fuel use value, but abundance of phenol and its derivatives can be used as chemical raw materials. Solid products were in the enrichment of Si, Al, Fe, and other mineral elements, which have a good application prospect as building materials.     

Integrated process of coal pyrolysis and CO2 reforming of methane with and without using dielectric barrier discharge plasma

The integrated processes of Shenmu subbituminous coal pyrolysis and CO₂ reforming of methane over catalyst (Ni/SiO₂) with and without using dielectric barrier discharge plasma (ICCP and ICCC) were carried out to check the effectiveness of the integrated process on improving the tar yield of coal pyrolysis. The effects of the pyrolysis temperature and time on product yields were investigated. The results indicate that both the ICCC and ICCP have an effect on increasing the tar yield compared with coal pyrolysis under N₂ or H₂. The tar yield increases with the increase of pyrolysis temperature and time in the ICCC, while relatively lower pyrolysis temperature and shorter pyrolysis time is preferable in the ICCP. The highest tar yield is 24.8 wt% at 600°C for 22 min in the ICCC and that is 23.7 wt% at 500°C for 7 min in the ICCP.     

Characterization and prediction of biomass pyrolysis products

In this study some literature data on the pyrolysis characteristics of biomass under inert atmosphere were structured and analyzed, constituting a guide to the conversion behavior of a fuel particle within the temperature range of 200-1000 °C. Data is presented for both pyrolytic product distribution (yields of char, total liquids, water, total gas and individual gas species) and properties (elemental composition and heating value) showing clear dependencies on peak temperature. Empirical relationships are derived from the collected data, over a wide range of pyrolysis conditions and considering a variety of fuels, including relations between the yields of gas-phase volatiles and thermochemical properties of char, tar and gas. An empirical model for the stoichiometry of biomass pyrolysis is presented, where empirical parameters are introduced to close the conservation equations describing the process. The composition of pyrolytic volatiles is described by means of a relevant number of species: H₂O, tar, CO₂, CO, H₂, CH₄ and other light hydrocarbons. The model is here primarily used as a tool in the analysis of the general trends of biomass pyrolysis, enabling also to verify the consistency of the collected data. Comparison of model results with the literature data shows that the information on product properties is well correlated with the one on product distribution. The prediction capability of the model is briefly addressed, with the results showing that the yields of volatiles released from a specific biomass are predicted with a reasonable accuracy. Particle models of the type presented in this study can be useful as a submodel in comprehensive reactor models simulating pyrolysis, gasification or combustion processes.     

Catalytic pyrolysis of microalgae to high-quality liquid bio-fuels

The pyrolytic conversion of chlorella algae to liquid fuel precursor in presence of a catalyst (Na₂CO₃) has been studied. Thermal decomposition studies of the algae samples were performed using TGA coupled with MS. Liquid oil samples were collected from pyrolysis experiments in a fixed-bed reactor and characterized for water content and heating value. The oil composition was analyzed by GC-MS. Pretreatment of chlorella with Na₂CO₃ influences the primary conversion of chlorella by shifting the decomposition temperature to a lower value. In the presence of Na₂CO₃, gas yield increased and liquid yield decreased when compared with non-catalytic pyrolysis at the same temperatures. However, pyrolysis oil from catalytic runs carries higher heating value and lower acidity. Lower content of acids in the bio-oil, higher aromatics, combined with higher heating value show promise for production of high-quality bio-oil from algae via catalytic pyrolysis, resulting in energy recovery in bio-oil of 40%.     

Kinetic and experimental characterizations of biomass pyrolysis in granulated blast furnace slag

With the objective of abating the energy crisis and greenhouse gas emissions, biomass pyrolysis to recover waste heat from granulated blast furnace (BF) slag was investigated via thermogravimetric and continuous fixed-bed experiments. The results showed that the mass conversion of biomass pyrolysis increased with the increasing heating rate. At the same time, a higher gas yield and lower heating value (LHV) and concentrations of H₂ and CO were obtained with the increasing temperature. Granulated BF slag can promote the pyrolysis and reforming of biomass tar, increasing the gas yield and LHV and H₂ concentration. Thus, granulated BF slag not only provided heat for the pyrolysis reaction but also promoted the pyrolysis and reforming of biomass tar, which might block and corrode pipes in practical production. The shrinking core model (R2) selected using a two-step calculation method interpreted the biomass pyrolysis in granulated BF slag. The reaction activation energy ranged from 60.743 kJ/mol to 65.963 kJ/mol as the heating rate decreased from 40 K/min to 10 K/min.     

Premium quality fuels and chemicals from the fluidised bed pyrolysis of biomass with zeolite catalyst upgrading

Biomass in the form of pine wood was pyrolysed in an externally heated fluidised bed pyrolysis reactor with nitrogen as the fluidising gas. A section of the freeboard of the reactor was packed with zeolite ZSM-5 catalyst. The pyrolysis oils before and after catalysis were collected in a series of condensers and cold traps. In addition, gases were analysed off-line by packed column gas chromatography. The composition of the oils and gases were determined before and after catalysis in relation to process conditions. The oils were analysed by liquid chromatography followed by gas chromatography/mass spectrometry. The results showed that the oils before catalysis were highly oxygenated, after catalysis the oils were markedly reduced in oxygenated species with an increase in aromatic species, producing a premium grade gasoline type fuel. The gases were CO₂, CO, H₂, CH₄, C₂H₄ and C₃H₆ and minor concentrations of other hydrocarbon gases. After catalysis the concentration of CO₂ and CO were increased. Detailed analysis of the upgraded oils showed that there were high concentrations of economically valuable chemicals. However, biologically active polycyclic aromatic species were also present in the catalysed oil, which increased with increasing catalyst temperature.     

Mechanism of wet sewage sludge pyrolysis in a tubular furnace

The main objective of this work was to develop a preliminary mechanistic understanding of wet sewage sludge decomposition from starting constituents to final products, including intermediates formed during the pyrolysis process. Sewage sludge with a moisture content of 84.2 wt% was pyrolyzed at different temperatures in a tubular furnace, the pyrolysis products (hydrogen-rich fuel gas, tar and solid char) were detected by micro-GC, GC-MS, and FTIR, respectively. The high moisture content of wet sewage sludge generated a steam-rich atmosphere at high temperatures, leading to an in situ steam reforming of the volatile compounds and a partial gasification of the solid char, which contributed to the production of hydrogen-rich fuel gas. The pyrolysis process can be divided into two steps: at a relatively low temperature (<600 °C), the breaking of the C-H bonds of alkyl gave rise to the release of CH₄ and C₂ hydrocarbons, and a large amount of CO and CO₂ evolved as the result of CO decreasing, both processes indicated the decomposition of volatile compounds. The increasing absorbance amount of C-O and C-H_aromatic demonstrated the formation of tar. As temperature increased further, the diminishing IR absorbance of C-O and C-H_aromatic was accompanied by a significant reduction of tar yield and an increase of H₂. H₂ was considered as an indicator for the occurrence of tar cracking. The Diels-Alder reaction mechanism followed by dehydrogenation was employed to explain the PAHs formation.     

Catalytic reforming of biomass primary tar from pyrolysis over waste steel slag based catalysts

Steel slag (SS) contains high amounts of metal oxides and could be applied as the catalyst or support material for the reforming of biomass derived tar. In this research, steel slag supported nickel catalysts were prepared by impregnation of a small amount of nickel (0–10 wt%) and calcination at 900 °C, and then tested for the catalytic reforming of biomass primary tar from pine sawdust pyrolysis. The steel slag after calcination was mainly composed of Fe₂O₃ and MgFe₂O₄, and granular NiO particles was formed and highly dispersed on the surface of nickel loaded steel slag which lead to a porous structure of the catalysts. The steel slag showed good activity on converting biomass primary tar into syngas, and its performance can be further enhanced by the loading of nickel. The yield of H₂ increased significantly with the increase of nickel loading amount, while excessive nickel loading resulted in the decrease in CO and CH₄ yields and significant increase in CO₂ yield. The presence of steam contributed to enhancing the tar steam reforming as well as reactions between steam and produced gases, while decrease the contact probability between the reactants and the active sites of catalysts, leading to a little decrease in tar conversion efficiency but significant increase in syngas yield. The iron and nickel oxides were reduced by the syngas (CO and H₂) from the biomass pyrolysis, and stable and porous structure was formed on the surface of the nickel loaded catalysts during tar reforming.     

Steam gasification of Miscanthus X Giganteus with olivine as catalyst production of syngas and analysis of tars (IR, NMR and GC/MS)

Steam gasification of Miscanthus X Giganteus (MXG) at high heating rate in a fluidised bed reactor with the use of olivine as catalyst was investigated. The effects of temperature (815-880 °C) on the yields and the compositions of syngas and tars were determined. The experimental results show that the gas yields and the content of H₂ increase with the temperature, while the yields of tar, char and the content of CO, CO₂ and CH₄ in the product gas decrease. Noteworthy is that about 1.1 m³ of dry gas (at ambient conditions) per kg of dry ash free biomass were obtained with about 46% of H₂ and 24% of CO by volume at 880 °C.The tars composition was determined by FTIR, NMR and GC/MS. The identification of different compounds shows mainly the presence of simple molecules. This may be facilitating the possibility of complete tar reforming process (hot gas cleaning), to improvement of the syngas yield and the decrease of the formation of pollutants.     

Gasification of landfill leachate in supercritical water: Effects on hydrogen yield and tar formation

Landfill leachate was gasified in supercritical water (SCW) in a batch reactor made of 316 SS. The effects of temperature, pressure, reaction time and oxidation coefficient (OC) on the pollutant removal efficiencies and gasification characteristics were investigated. To observe the formation of tar and char visually, a capillary quartz reactor was also used. Results indicated that CO₂, H₂ and CH₄ were the most abundant gaseous products. Temperature has an appreciable effect on the gasification process. Increasing temperature enhanced the H₂ yield (GY_H2) and TOC removal efficiency (TRE) significantly. Although the influence of reaction time on the fractions of gaseous products was negligible at time above 300 s, the yields of H₂, CH₄, and CO₂ increased with reaction time whereas the CO, C₂H₄ and C₂H₆ yields decreased. Tar and char formation was evident on the interior surface of capillary quartz reactor. Adding a little oxidant could increase H₂ and CH₄ yields and decrease tar and char formation. GY_H2 reached up to the maximum of 231.3 mmol L^?1 leachate at 500 °C, 25 MPa, 600 s and 0.2 OC, which was 2.4 times of that without oxidant.     

Plate reactor as an analysis tool for rapid pyrolysis of biomass

This work presents a study of the performance of the modified plate reactor by rapid pyrolysis experiments with different biomass samples (MDF, bark pine and Avicel cellulose). The use of the plate instead of a grid allowed us to achieve a more homogeneous temperature distribution across the plate and, therefore, biomass sample. The mass yields of the major pyrolysis products CO, CO₂, C₂H₂, CH₄, C₂H₄ and C₂H₆ are measured as a function of the holding time (from 0 to 50 s) for a number of the final temperatures (from 435 to 1100 C) using the novel approach to quantitative FTIR analysis of biomass pyrolysis spectra. Special care was taken to demonstrate the influence of the secondary tar cracking on the yields of the permanent gases. Yields of major permanent gases plotted versus each other on a logarithmic scale show two distinctive regions reflecting primary and secondary kinetic processes. The experiments show that the modified plate reactor can be used for studying the kinetics of the primary decomposition of the biomass at temperatures ≤600 C.     

Effect of Olive Kernel thermal treatment (torrefaction vs. slow pyrolysis) on the physicochemical characteristics and the CO2 or H2O gasification performance of as-prepared biochars

The thermochemical conversion of biomass through its gasification has been widely explored during the last decades. The generated bio-syngas mixture can be directly used as fuel in thermal engines and fuel cells or as intermediate building block to produce synthetic liquid fuels and/or value added chemicals at large scales. In the present work, the effect of Greek olive kernel (OK) thermal treatment (torrefaction at 300 °C vs. slow pyrolysis at 500 and 800 °C) on the physicochemical characteristics and CO₂ or H₂O gasification performance of as-produced biochars is examined. Both the pristine OK sample and biochars (OK300, OK500, OK800) were fully characterized by employing a variety of physicochemical methods. The results clearly revealed the beneficial effect of thermal pretreatment on the gasification performance of as-prepared biochars. Α close relationship between the physicochemical properties of fuel samples and gas production was disclosed. Carbon dioxide gasification leads mainly to CO with minor amounts of H₂ and CH₄, whereas steam gasification results in a mixture containing CO₂, CO, H₂ and CH₄ with a H₂/CO ratio varied between 1.3 and 2.3. The optimum gasification performance was obtained for the slowly pyrolyzed samples (OK500 and OK800), due to their higher carbon and ash content as well as to their higher porosity and less ordered structure compared to pristine (OK) and torrefied (OK300) samples.     

Solar-driven pyrolysis and gasification of low-grade carbonaceous materials

Three low-grade carbonaceous materials from biomass (Scenedesmus algae and wheat straw) and waste treatment (sewage sludge) have been selected as feedstock for solar-driven thermochemical processes. Solar-driven pyrolysis and gasification measurements were conducted directly irradiating the samples in a 7 kW_e high flux solar simulator and the released gases H₂, CO, CO₂ and CH₄ and the sample temperature were continuously monitored.Solar-driven experiments showed that H₂ and CO evolved as important product gases demonstrating the high quality of syngas production for the three feedstocks. Straw is the more suitable feedstock for solar-driven processes due to the high gas production yields. Comparing the solar-driven experiments, gasification generates higher percentage of syngas (mix of CO and H₂) respect to total gas produced (sum of H₂, CO, CO₂ and CH₄) than pyrolysis. Thus, solar-driven gasification generates better quality of syngas production than pyrolysis.     

Catalytic pyrolysis of biomass: Effects of pyrolysis temperature,sweeping gas flow rate and MgO catalyst

Cotton seed, as a biomass source, is pyrolysed in a tubular fixed-bed reactor under various sweeping gas (N₂) flow rates at different pyrolysis temperatures. In the non-catalytic work, the maximum bio-oil yield was attained as 48.30% at 550 °C with a sweeping gas flow rate of 200 mL min⁻¹. At the optimum conditions, catalytic pyrolysis of biomass samples was performed with various amounts of MgO catalyst (5, 10, 15, and 20 wt.% of raw material). Catalyst addition decreased the quantity of bio-oil yet increased the quality of bio-oil in terms of calorific value, hydrocarbon distribution and removal of oxygenated groups. It was observed that increasing the amount of catalyst used, decreased the oil yields while increased the gas and char yields. Bio-oils obtained at the optimum conditions were separated into aliphatic, aromatic and polar sub-fractions. After the application of column chromatography, bio-oils were subjected into elemental, FT-IR and ¹H NMR analyses. Aliphatic sub-fractions of bio-oils were analyzed by GC–MS. It was deduced that the fuel obtained via catalytic pyrolysis mainly consisted of lower weight hydrocarbons in the diesel range. Finally, obtained results were compared with petroleum fractions and evaluated as a potential source for liquid fuels.