Syngas yield during pyrolysis and steam gasification of paper

Main characteristics of gaseous yield from steam gasification have been investigated experimentally. Results of steam gasification have been compared to that of pyrolysis. The temperature range investigated were 600–1000 °C in steps of 100 °C. Results have been obtained under pyrolysis conditions at same temperatures. For steam gasification runs, steam flow rate was kept constant at 8.0 g/min. Investigated characteristics were evolution of syngas flow rate with time, hydrogen flow rate and chemical composition of syngas, energy yield and apparent thermal efficiency. Residuals from both processes were quantified and compared as well. Material destruction, hydrogen yield and energy yield is better with gasification as compared to pyrolysis. This advantage of the gasification process is attributed mainly to char gasification process. Char gasification is found to be more sensitive to the reactor temperature than pyrolysis. Pyrolysis can start at low temperatures of 400 °C; however char gasification starts at 700 °C. A partial overlap between gasification and pyrolysis exists and is presented here. This partial overlap increases with increase in temperature. As an example, at reactor temperature 800 °C this overlap represents around 27% of the char gasification process and almost 95% at reactor temperature 1000 °C.     

Flash pyrolysis of jatropha oil cake in electrically heated fluidized bed reactor

Fluidized bed flash pyrolysis experiments have been conducted on a sample of jatropha oil cake to determine particularly the effects of particle size, pyrolysis temperature and nitrogen gas flow rate on the pyrolysis yields. The particle size, nitrogen gas flow rate and temperature of jatropha oil cake were varied from 0.3 to 1.18 mm, 1.25 to 2.4 m³/h and 350 to 550 °C. The maximum oil yield of 64.25 wt% was obtained at a nitrogen gas flow rate of 1.75 m³/h, particle size of 0.7–1.0 mm and pyrolysis temperature of 500 °C. The calorific value of pyrolysis oil was found to be 19.66 MJ/kg. The pyrolysis gas can be used as a gaseous fuel.     

Hydrogen-rich gas from catalytic steam gasification of municipal solid waste (MSW): Influence of catalyst and temperature on yield and product composition

In the present study the catalytic steam gasification of MSW to produce hydrogen-rich gas or syngas (H₂ + CO) with calcined dolomite as a catalyst in a bench-scale downstream fixed bed reactor was investigated. The influence of the catalyst and reactor temperature on yield and product composition was studied at the temperature range of 750–950 °C, with a steam to MSW ratio of 0.77, for weight hourly space velocity of 1.29 h⁻¹. Over the ranges of experimental conditions examined, calcined dolomite revealed better catalytic performance, at the presence of steam, tar was completely decomposed as temperature increases from 850 to 950 °C. Higher temperature resulted in more H₂ and CO production, higher carbon conversion efficiency and dry gas yield. The highest H₂ content of 53.29 mol%, and the highest H₂ yield of 38.60 mol H₂/kg MSW were observed at the highest temperature level of 950 °C, while, the maximum H₂ yield potential reached 70.14 mol H₂/kg dry MSW at 900 °C. Syngas produced by catalytic steam gasification of MSW varied in the range of 36.35–70.21 mol%. The char had a highest ash content of 84.01% at 950 °C, and negligible hydrogen, nitrogen and sulphur contents.     

Rice straw as a bio-oil source via pyrolysis and steam pyrolysis

The pyrolysis of rice straw was studied to estimate the effect of pyrolysis conditions on product yields and bio-oil composition when the heating rate was 5 K/min. Pyrolysis temperature, particle size, sweeping gas flow rate and steam velocity were the experimental parameters. Among the four pyrolysis temperatures; namely, 673, 773, 823 and 973 K; 823 K gave the highest bio-oil yield of 27.26%. Six different particle sizes were examined and sample having a particle size of 0.425<D_p<0.85 mm had a bio-oil yield of 27.77%. Nitrogen was used as the sweeping gas with the flow rates of either 50, 100, 200 and 400 ml/min and the highest bio-oil yield was obtained when flow rate was 200 ml/min. The bio-oil yield reached a maximum value of 35.86% with the steam velocity of 2.7 cm/s. Liquid products obtained from pyrolysis, inert atmosphere pyrolysis and steam pyrolysis were then fractionated into aspalthanes and maltanes. The aliphatic subfraction obtained by column chromatography was then analysed by GC/MS. For further structural analysis, the pyrolysis oils were conducted with ¹H-NMR, oils and aliphatic subfractions with FT-IR. The chemical characterisation has shown that the oil obtained from rice straw may be potentially valuable as fuel and chemicals feedstocks.     

Pyrolysis of soybean oil with H-ZSM5 (Proton-exchange of Zeolite Socony Mobil #5) and MCM41 (Mobil Composition of Matter No. 41) catalysts in a fixed-bed reactor

Soybean oil was pyrolyzed with various catalysts in a fixed-bed reactor under nitrogen flow at 420 and 450 °C. The H-ZSM5 catalysts (molar ratio SiO₂/Al₂O₃ = 28, 40, and 180) and 2 wt% (Ga, Al or Cu) impregnated MCM41 catalysts were used in order to investigate the effect of catalysts during the pyrolysis process. The gas products in all experiments were mainly methane, ethane and propylene. The liquid products in the presence of H-ZSM5 catalysts were mainly aromatic components while those with metal/MCM41 catalysts were a mixture of alkanes, alkenes, alkadienes, aromatic and carboxylic acids. The highest coke yield of 4.4 wt% was obtained with Ga/MCM41 catalyst at the pyrolysis temperature of 420 °C. The effect of catalysts on product yield and composition was systematically investigated.     

Syngas production from catalytic gasification of waste polyethylene: Influence of temperature on gas yield and composition

The catalytic steam gasification of waste polyethylene (PE) from municipal solid waste (MSW) to produce syngas (H₂ + CO) with NiO/γ-Al₂O₃ as catalyst in a bench-scale downstream fixed bed reactor was investigated. The influence of the reactor temperature on the gas yield, gas composition, steam decomposition, low heating value (LHV), cold gas efficiency and carbon conversion efficiency was investigated at the temperature range of 700–900 °C, with a steam to waste polyethylene ratio of 1.33. Over the ranges of experimental conditions examined, NiO/γ-Al₂O₃ catalyst revealed better catalytic performance as a view of increasing product gas yield and of decreasing char and liquid yields in the presence of steam. Higher temperature resulted in more H₂ and CO production, higher carbon conversion efficiency and product gas yield. The highest syngas (H₂ + CO) content of 64.35 mol%, the highest H₂ content of 36.98 mol%, and the highest CO content of 27.37 mol%, were achieved at the highest temperature level of 900 °C. Syngas produced with a H₂/CO molar ratio in the range of 0.83–1.35, was highly desirable as feedstock for Fischer–Tropsch synthesis for the production of transportation fuels.     

Removal of Cu(II) from aqueous solution using the rice husk carbons prepared by the physical activation process

The adsorption of Cu(II) from aqueous solution by carbons prepared from rice husk through pyrolysis and steam activation was studied. The rice husk carbon was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), and its pore structure was also examined. After comparing different characteristics of the carbons prepared under different conditions and their adsorption abilities of Cu(II), the optimum temperature for pyrolysis and steam activation was chosen as 700 and 750 °C, respectively, using 3% (V/V) steam as the best activation gas. It was found that the Cu(II) adsorption on the rice husk derived carbons was pH and temperature dependent with an optimum pH value of 5.0, and an equilibrium time of 24 h. The adsorption kinetics and isotherms of Cu(II) by the rice husk derived carbons were also investigated under four different temperatures, and good correlation coefficients were obtained for the pseudo-second-order kinetic models, and the Langmuir isotherm model fitted very well with the experimental data. The mean free energy E (kJ mol⁻¹) obtained in the Dubinin-Radushkevitch (D-R) adsorption isortherm equation indicated a chemical ion-exchange mechanism. Several thermodynamic parameters were also caculated to predict the nature of adsorption process.     

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.     

Comparisons of the hydrogen-rich syngas compositions from wet rice husk slurry steam reforming reactions using different catalysts

Rice husk slurry is pumped into a packed reactor and the products from the steam reforming reactions using different catalysts are studied. The steam/biomass weight ratio of such a system is between 3.47 and 5.25. The solids, liquid and gaseous products are a mass fraction of 2.8-4.1%, a mass fraction of 92.4-93.0% and a mass fraction of 3.5-4.7%, respectively. The hydrogen concentration in the gaseous product is approximate a volume fraction of 41% using the Al₂O₃ catalyst of a CuO mass fraction of 13%, a volume fraction of 38% using the Al₂O₃ catalyst of a Ni mass fraction of 13%, a volume fraction of 31% using the Al₂O₃ catalyst of a ZnO mass fraction of 13%, and a volume fraction of 20% using the Al₂O₃ catalyst at the reactor temperature of 800 °C. In the reactor temperature range studied (350-800 °C), the hydrogen concentration in the product stream increases monotonically with the increasing of the reactor temperature and the steam/carbon molar ratio. The value of dry gas LHV is between 9.4 MJ m⁻³ and 12 MJ m⁻³ at the reaction temperature of 600-800 °C. Considering the simple catalyst used in current study, the syngas of a hydrogen volume fraction of approximate 40% is obtained by pumping the biomass slurry to carry out the catalytic steam reforming reaction.     

Hydrogen production from ethanol over Co/ZnO catalyst in a multi-layered reformer

A Co/ZnO catalyst was prepared by coprecipitation method, and was applied for ethanol steam reforming. The effect of reaction conditions on the ethanol steam reforming performance was studied in the temperature ranges from 400 °C to 600 °C and the space velocity ranges from 10,000 h⁻¹ to 120,000 h⁻¹ in a fixed bed reactor. The Co/ZnO showed high activity with an ethanol conversion of 97% and a H₂ concentration of 73% at a gas hourly space velocity of 40,000 h⁻¹ and a moderately low temperature of 450 °C. EXAFS analysis for fresh and spent samples confirms that Co phase maintains during reaction. The catalyst was then loaded into a multi-layered reformer of which the design concept allows for integrating endothermic steam reforming, exothermic combustion and evaporation in a reactor. The performance of the compact reformer demonstrated that the hydrogen production rate satisfy a PEMFC stack power level of 540 W suitable for portable power supplies.     

Energy Applications of Biomass: Pyrolysis of Apricot Stone

Apricot stone (Prunus armeniaca L.) was pyrolyzed in a directly heated fixed-bed reactor under nitrogen atmosphere. Effects of sweeping gas flow rates and pyrolysis temperature on the pyrolysis of the biomass were also studied. Pyrolysis runs were performed using reactor temperatures between 400°C and 700°C with heating rate of about 300°C min^?1. As the pyrolysis temperature was increased, the percentage mass of char decreased while gas product increased. The product yields were significantly influenced by the process conditions. The bio-oil obtained at 550°C, at which the liquid product yield was maximum, was analyzed. It was characterized by Fourier transform infrared spectroscopy (FT-IR). In addition, the solid and liquid products were analyzed to determine their elemental composition and calorific value. Chemical fractionation of bio-oil showed that only low quantities of hydrocarbons were present, while oxygenated and polar fractions dominated.     

Characteristic of hydrogen and syngas evolution from gasification and pyrolysis of rubber

The characteristics of syngas evolution during pyrolysis and gasification of waste rubber have been investigated. A semi-batch reactor was used for the thermal decomposition of the material under various conditions of pyrolysis and high temperature steam gasification. The results are reported at two different reactor temperatures of 800 and 900 °C and at constant steam gasifying agent flow rate of 7.0 g/min and a fixed sample mass. The characteristics of syngas were evaluated in terms of syngas flow rate, hydrogen flow rate, syngas yield, hydrogen yield and energy yield. Gasification resulted in 500% increase in hydrogen yield as compared to pyrolysis at 800 °C. However, at 900 °C the increase in hydrogen was more than 700% as compared to pyrolysis. For pyrolysis conditions, increase in reactor temperature from 800 to 900 °C resulted in 64% increase in hydrogen yield while for gasification conditions a 124% increase in hydrogen yield was obtained. Results of syngas yield, hydrogen yield and energy yield from the rubber sample are evaluated with that obtained from woody biomass samples, namely hard wood and wood chips. Rubber gasification yielded more energy at the 900 °C as compared to biomass feedstock samples. However, less syngas and less hydrogen were obtained from rubber than the biomass samples at both the temperatures reported here.     

Production of bio-fuels from cottonseed cake by catalytic pyrolysis under steam atmosphere

The purpose of this study is to evaluate the amounts of catalytic pyrolysis products of cottonseed cake in steam atmosphere and investigate the effects of both zeolite and steam on pyrolysis yields. The effect of steam was investigated by co-feeding steam at various velocities (0.6:1.3:2.7 cm s⁻¹) in the presence of zeolite (20 wt% of feed). Liquid pyrolysis products obtained at the most appropriate conditions were fractionated by column chromatography. Elemental analysis and FT-IR were applied on both of these liquid products and their sub-fractions. The H/C ratios obtained from elemental analysis were compared with the petroleum products. The aliphatic sub-fractions of the oils were then analysed by capillary column gas chromatography. Further structural analysis of pyrolysis oil was conducted using ¹H-NMR spectroscopy. The characterization has shown that the bio-oil obtained from catalytic and steam pyrolysis of cottonseed cake was more beneficial than those obtained from non-catalytic and catalytic works under static and nitrogen atmospheres.     

Integrated catalytic adsorption (ICA) steam gasification system for enhanced hydrogen production using palm kernel shell

This paper investigates the integrated catalytic adsorption (ICA) steam gasification of palm kernel shell for hydrogen rich gas production using pilot scale fluidized bed gasifier under atmospheric condition. The effect of temperature (600–750 °C) and steam to biomass ratio (1.5–2.5 wt/wt) on hydrogen (H₂) yield, product gas composition, gas yield, char yield, gasification and carbon conversion efficiency, and lower heating values are studied. The results show that H₂ hydrogen composition of 82.11 vol% is achieved at temperature of 675 °C, and negligible carbon dioxide (CO₂) composition is observed at 600 °C and 675 °C at a constant steam to biomass ratio of 2.0 wt/wt. In addition, maximum H₂ yield of 150 g/kg biomass is observed at 750 °C and at steam to biomass ratio of 2.0 wt/wt. A good heating value of product gas which is 14.37 MJ/Nm³ is obtained at 600 °C and steam to biomass ratio of 2.0 wt/wt. Temperature and steam to biomass ratio both enhanced H₂ yield but temperature is the most influential factor. Utilization of adsorbent and catalyst produced higher H₂ composition, yield and gas heating values as demonstrated by biomass catalytic steam gasification and steam gasification with in situ CO₂ adsorbent.     

Low temperature sugar cane bagasse pyrolysis for the production of high purity hydrogen through steam reforming and CO2 capture

Biomass pyrolysis offers a fast route to produce elevated yields towards highly valued liquid products. This research aims the determination of optimal experimental conditions for a slow and low temperature pyrolysis to produce the highest yield towards condensable (CVM) and non-condensable (NCVM) volatile matter from Mexican cane bagasse and to quantify and characterize the compounds that constitute CVM and NCVM obtained. Results indicate that yield towards volatiles is strongly dependent on temperature. The highest yield was achieved at temperatures greater than 500 °C at a heating rate of 10 °C/min, residence time of 60 min and a particle size between of 420 and 840 μm. Product quantification under isothermal conditions determined that at 550 °C the NCVM, CVM and solid residue was of 26, 57 and 16%, respectively. Preliminary thermodynamic analysis of steam reforming and CO₂ absorption reactions using one of the main CVM products resulted in a potential high hydrogen production yield.     

Hydrogen production from polystyrene pyrolysis and gasification: Characteristics and kinetics

Polystyrene (PS) pyrolysis and gasification have been examined in a semi-batch reactor at temperatures of 700, 800 and 900 °C. Characteristic differences between pyrolysis and gasification of polystyrene (PS) have been evaluated with specific performance focus on the evolution of syngas flow rate, evolution of hydrogen flow rate, evolution of output power, syngas yield, hydrogen yield, energy yield, apparent thermal efficiency and syngas quality. Behavior of PS under either pyrolysis or gasification processes is compared to that of char based sample, such as paper and cardboard. In contrast to char based materials, PS gasification yielded less syngas, hydrogen and energy than pyrolysis at 700 °C. However, the gasification of PS yielded more syngas, hydrogen and energy than pyrolysis at 900 °C temperature. Gasification of PS is affected by reactor temperature more than PS pyrolysis. Syngas, hydrogen and energy yield increased exponentially with temperature in case of gasification. However, syngas and energy yield increased linearly with temperature having rather a mild slope in the case of pyrolysis. Pyrolysis resulted in higher syngas quality at all temperatures. Kinetics of hydrogen evolution from the PS pyrolysis is introduced. The Coats and Redfern method was used to determine the kinetic parameters, activation energy (E_act), pre-exponential factor (A) and reaction order (n). The model used is the nth order chemical reaction model. Kinetic parameters have been determined for three slow heating rates, namely 8, 10 and 12 °C/min. The average values obtained from the three heating rate experiments were used to compare the model with the experimental data.     

Fixed-Bed Pyrolysis of Hazelnut (Corylus Avellana L.) Bagasse: Influence of Pyrolysis Parameters on Product Yields

Fixed-bed slow pyrolysis experiments have been conducted on a sample of hazelnut bagasse to determine particularly the effects of pyrolysis temperature, heating rate, particle size and sweep gas flow rate on the pyrolysis product yields. The temperature of pyrolysis, heating rate, particle size and sweep gas flow rate were varied in the ranges 350–550° C, 10 and 50° C/min, 0.224–1.800 mm and 50–200 cm³/min, respectively. Under the various pyrolysis conditions applied in the experimental studies, the obtained char, liquid, and gas yield values ranged between 26 and 35 wt%, 23 and 34.40 wt%, and 25 and 32 wt%, respectively. The maximum biooil yield of 34.40% was obtained at the final pyrolysis temperature of 500°C, with a heating rate of 10° C/min, particle size range of 0.425–0.600 mm and a sweep gas flow rate of 150 cm³/min.     

Slow, fast and flash pyrolysis of rapeseed

Pyrolysis experiments have been conducted on a sample of rapeseed to determine particularly the effects of pyrolysis temperature, heating rate, particle size and sweep gas flow rate on the pyrolysis product yields and their chemical compositions. The maximum oil yield of 73% was obtained at the final pyrolysis temperature of 550–600 °C, particle size range of +0.6–1.25 mm, and sweep gas flow rate of 100 cm³min⁻¹ (N₂) at flash pyrolysis conditions in tubular transport reactor. Chromatographic and spectroscopic studies on the pyrolytic oil showed that the oil obtained from rapeseed can be used as a renewable fuel and chemical feedstock.     

Hydrogen-rich gas production from waste plastics by pyrolysis and low-temperature steam reforming over a ruthenium catalyst

Operating conditions for low-temperature pyrolysis and steam reforming of plastics over a ruthenium catalyst were investigated. In the range studied, the highest gas and lowest coke fractions for polystyrene (PS) with a 60 g h⁻¹ scale, continuous-feed, two-stage gasifier were obtained with a pyrolyzer temperature of 673 K, steam reforming temperature of 903 K, and weight hourly space velocity (WHSV) of 0.10 g-sample g-catalyst⁻¹ h⁻¹. These operating conditions are consistent with optimum conditions reported previously for polypropylene. Our results indicate that at around 903 K, the activity of the ruthenium catalyst was high enough to minimize the difference between the rates of the steam reforming reactions of the pyrolysates from polystyrene and polypropylene. The proposed system thus has the flexibility to compensate for differences in chemical structures of municipal waste plastics. In addition, the steam reforming temperature was about 200 K lower than the temperature used in a conventional Ni-catalyzed process for the production of hydrogen. Low-temperature steam reforming allows for lower thermal input to the steam reformer, which results in an increase in thermal efficiency in the proposed process employing a Ru catalyst. Because low-temperature steam reforming can be also expected to reduce thermal degradation rates of the catalyst, the pyrolysis-steam reforming process with a Ru catalyst has the potential for use in small-scale production of hydrogen-rich gas from waste plastics that can be used for power generation.     

Thermodynamic analysis of hydrogen production via autothermal steam reforming of selected components of aqueous bio-oil fraction

From a technical and economic point of view, autothermal steam reforming offers many advantages, as it minimizes heat load demand in the reformer. Bio-oil, the liquid product of biomass pyrolysis, can be effectively converted to a hydrogen-rich stream. Autothermal steam reforming of selected compounds of bio-oil was investigated using thermodynamic analysis. Equilibrium calculations employing Gibbs free energy minimization were performed for acetic acid, acetone and ethylene glycol in a broad range of temperature (400–1300 K), steam to fuel ratio (1–9) and pressure (1–20 atm) values. The optimal O₂/fuel ratio to achieve thermoneutral conditions was calculated under all operating conditions. Hydrogen-rich gas is produced at temperatures higher than 700 K with the maximum yield attained at 900 K. The ratio of steam to fuel and the pressure determine to a great extent the equilibrium hydrogen concentration. The heat demand of the reformer, as expressed by the required amount of oxygen, varies with temperature, steam to fuel ratio and pressure, as well as the type of oxygenate compound used. When the required oxygen enters the system at the reforming temperature, autothermal steam reforming results in hydrogen yield around 20% lower than the yield by steam reforming because part of the organic feed is consumed in the combustion reaction. Autothermicity was also calculated for the whole cycle, including preheating of the organic feed to the reactor temperature and the reforming reaction itself. The oxygen demand in such a case is much higher, while the amount of hydrogen produced is drastically reduced.