农林生物质热裂解制取合成气的研究

以树叶为原料，利用热裂解装置进行了试验。并对裂解产物的组成进行了分析。结果表明：树叶热裂解产物为生物油、合成气和炭，其合成气成分主要由CO、CH4、H2和水蒸气组成。     

Hydrogen production from biomass combining pyrolysis and the secondary decomposition

An efficient method of hydrogen production from biomass was studied in this paper. The pyrolysis of biomass was combined with the secondary decomposition of gaseous intermediate for hydrogen-rich gas production, with the avoidance of N₂ and CO₂ dilution to the energy density of gaseous effluents. In order to acquire the optimum conditions for hydrogen generation, effects of operating parameters on this two-step decomposition of biomass were analyzed through simulation of thermodynamic equilibrium and experiments using Ni/cordierite catalyst. The results indicate that the operating parameters, including pyrolysis temperature 923 K, 18 min of residence time, the secondary decomposition temperature 1123 K and molar steam to carbon ratio 2, satisfy all the criteria for high hydrogen content and energy efficiency. Hydrogen content of above 60% and hydrogen yield of around 65 g/kg biomass were achieved with optimized conditions. The hydrogen-rich gas is preferred for potential utilization in downstream fuel cells for the implementation of distributed energy supply, and is also practical for pure hydrogen production.     

Production and characterization of bio-oil and biochar from rapeseed cake

New and renewable fuels are the major alternatives to conventional fossil fuels. Biomass in the form of agricultural residues is becoming popular among new renewable energy sources, especially given its wide potential and abundant usage. Pyrolysis is the most important process among the thermal conversion processes of biomass. In this study, the production of bio-oil and biochar from rapeseed cake obtained by cold extraction pressing was investigated and the various characteristics of biochar and bio-oil acquired under static atmospheric conditions were identified. The biochar obtained are carbon rich, with high heating value and relatively pollution-free potential solid biofuel. The bio-oil product was presented as an environmentally friendly green biofuel candidate.     

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.     

Pyrolysis of black cumin seed cake in a fixed-bed reactor

The black cumin seed cake (BCSC) is a by-product obtained from the black cumin seeds with cold pressing. This by-product can be utilized as a biomass feedstock for conversion to bio-oil with pyrolysis process. The BCSC samples were initially pyrolyzed on a lab-scale pyrolysis system at different values in the ranges of 300-800 °C and 0.050-0.300 L min⁻¹ to determine the effects of operation temperature and N₂ flow rate on the yields on products, respectively. Then, the bio-oil in the highest yield (wB = 44.37%) which was obtained at pyrolysis final temperature (450 °C) temperature, heating rate (35 °C min⁻¹), particle size (dp > 850 ??m), and sweeping flow rate of 0.200 L min⁻¹ was characterized by Fourier Transform infra-red (FT-IR) spectroscopy, gas chromatography/mass spectrometry (GC-MS) and column chromatography. Consequently, it was shown that the operating temperature and N₂ gas flow rate parameters were effective on the product yields. Also, the important some physico-chemical properties of the pyrolytic oil obtained in high yield were determined as the calorific value of 38.48 MJ kg⁻¹, the empirical formula of CH_1.651O_0.105N_0.042S_0.001, the rich chemical content containing many different chemical groups, and the density of 970.25 kg m⁻³, and the viscosity of 63.42 mm² s⁻¹. Based on the determined properties of the pyrolytic oil, it was decided that the use of pyrolytic oil derived from the BCSC may possible be for the production of the alternative liquid fuels and finely chemicals after the necessary improvements.     

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.     

Modeling chemical and physical processes of wood and biomass pyrolysis

This review reports the state of the art in modeling chemical and physical processes of wood and biomass pyrolysis. Chemical kinetics are critically discussed in relation to primary reactions, described by one- and multi-component (or one- and multi-stage) mechanisms, and secondary reactions of tar cracking and polymerization. A mention is also made of distributed activation energy models and detailed mechanisms which try to take into account the formation of single gaseous or liquid (tar) species. Different approaches used in the transport models are presented at both the level of single particle and reactor, together with the main achievements of numerical simulations. Finally, critical issues which require further investigation are indicated.     

Predictions of concentration in the pyrolysis of biomass materials—I

The present work involves the prediction of the concentration profiles in the case of pyrolysis of different lignocellulosic materials in isothermal and non-isothermal conditions. The operative temperature range is from 573 to 973 K for isothermal conditions, and for non-isothermal conditions, the heating rate ranges from 5 to 80 K/min (5, 20, 40, 60 and 80 K/min).

The concentration for the above mentioned conditions is predicted for various biomass components, viz. cellulose, hemicellulose and lignin. Based on the concentration profiles of different biomass materials, it is possible to predict the pyrolysis behavior over a wide range of temperatures under isothermal and non-isothermal conditions for a large number of biomass materials, provided the activation energy and the frequency factor for the various reaction steps are known. It is also possible to ascertain the degree of combustibility of different biomass materials.

The simulation model utilizes a 4th order Runge-Kutta Predictor-Corrector method to solve the coupled ordinary differential equations. Based on thermogravimetric analysis done elsewhere, it is considered that temperature and time have a linear relationship. The above technique enables us to predict concentration profiles of different biomass materials for the entire range of pyrolysis. The concentration vs time data is plotted graphically for both isothermal and non-isothermal conditions utilizing the Harvard Graphics package on a PC-A/T personal computer.     

Synergistic effect of curcumin and activated carbon catalyst enhancing hydrogen production from biomass pyrolysis

This study observes the synergistic effect of low cost and environmentally friendly catalysts, Activated Carbon and curcumin on the production of hydrogen gas in the biomass pyrolysis process. The Study used turmeric containing curcumin as an anti-oxidant agent added to the activated carbon (AC) catalyst. Biomass from coconut wood was pyrolyzed up to 550 °C using a fixed bed reactor. Both AC and curcumin were combined with a ratio of 1:0, 1:1, 1: 3, 0:1, and 3:1. The addition of AC and curcumin was able to increase the production of hydrogen and methane gas. The combination of AC and curcumin with 1:1 ratio was able to increase hydrogen gas by 25.6%. In addition, this combination was also increase methane gas by 71.8%.Curcumin as an anti-oxidant is able to prevents recombination reactions between radical molecules. Activated carbon surface is more protected from free radicals attacking and sticking to the surface. The phi-phi interaction between the two aromatic rings and the surface of activated carbon produces electrostatic forces on the surface of activated carbon to become stronger therefore it is more reactive in cracking hydrocarbon molecules and producing hydrogen gas. Software simulation, SEM, XRD, and FTIR tests were performed to support the analysis of experimental results.     

The Evritania (Greece) demonstration plant of biomass pyrolysis

This paper is focused on describing the Evritania demonstration plant for pyrolysis of forestry biomass. This plant was constructed in the village of Voulpi, district of Evritania, in Central Greece, in 1995, with a threefold purpose; development of know-how, forest fire prevention and rural development. The products are charcoal and bio-oil. The plant capacity is 1200–1450 kg/h of wet biomass and the pyrolysis temperature is approx. 400°C. The raw material used is Arbutus unedo, which is an evergreen broad-leaf tree which covers the area. Other agricultural waste could also be used, such as olive pits and cuttings, almond shells and cotton kernels. The paper includes the conceptual process flow sheet, the changes and improvements made during the trial phase, data from the start-up phase, and product characteristics. Comparison of the process with the Alten process is presented. Additionally, comparisons are made of product characteristics with those from other pyrolysis processes. In general, the results obtained are encouraging even though several improvements of the pilot plant are required.     

Hydrogen-rich gas production from a biomass pyrolysis gas by using a plasmatron

Pyrolysis and gasification is an energy conversion technology process that produces industrially useful syngas from various biomasses. However, due to the tars in the product gases generated from the pyrolysis/gasification of biomass, this process damages and causes operation problems with equipment that use product gases such as gas turbines and internal engines.     

Fundamentals, kinetics and endothermicity of the biomass pyrolysis reaction

The paper reviews the pyrolysis of biomass constituents and possible secondary reactions. Biomass pyrolysis yields mostly liquid and solid fuel, easy to store and transport.Relevant working conditions for experiments and large-scale operation are: (i) biomass particles < 200 μm, (ii) a particle heating rate of at least about 80 K min⁻¹ and (iii) a reactor environment where the internal resistance to heat penetration is smaller than the external resistance to heat transfer (Biot-number, Bi < 1).The circumstances of TGA and DSC experiments meet these requirements and fully determine the reaction kinetics and endothermicity of the pyrolysis reaction. The reaction rate constant and the heat of reaction are essential parameters in the design of a pyrolysis reactor. For most of the biomass species tested, the first order reaction rate constant is large and >0.5 s⁻¹. The heat of reaction ranges from 207 to 434 kJ kg⁻¹. All results tie in with literature data, although the reader is cautioned in using literature data since experiments were not always performed under relevant testing conditions.     

Synthesis gas production by biomass pyrolysis: Effect of reactor temperature on product distribution

This paper describes mass, C, H, and O balances for wood chips pyrolysis experiments performed in a tubular reactor under conditions of rich H₂ gas production (700–1000 °C) and for determined solid heating rates (20–40 °C s⁻¹). Permanent gases (H₂, CO, CH₄, CO₂, C₂H₄, C₂H₆), water, aromatic tar (10 compounds from benzene to phenanthrene and phenols), and char were considered in the balance calculations. Hydrogen (H) from dry wood is mainly converted into CH₄ (more than 30% mol. of H at 900 °C), H₂ (from 9% to 36% mol. from 700 to 1000 °C), H₂O, and C₂H₄. The molar balances showed that the important yield increase of H₂ from 800 to 1000 °C (0.10 Nm³ kg⁻¹ to 0.24 Nm³ kg⁻¹ d.a.f. wood) cannot be solely explained by the analyzed hydrocarbon compounds conversion (CH₄, C₂, aromatic tar). Possible mechanisms of H₂ production from wood pyrolysis are discussed.     

Pyrolysis as a technique for separating heavy metals from hyperaccumulators. Part II: Lab-scale pyrolysis of synthetic hyperaccumulator biomass

Synthetic hyperaccumulator biomass (SHB) impregnated with Ni, Zn, Cu, Co or Cr was used to conduct 11 experiments in a lab-scale fluidized bed reactor. Two runs with blank corn stover, with no metal added, were also conducted. The reactor was operated in an entrained mode in a oxygen-free (N₂) environment at 873 K and 1 atm. The apparent gas residence time through the lab-scale reactor was 0.6 s at 873 K.

The material balance for the lab-scale experiments on N₂-free basis varied between 81% and 98%. The presence of a heavy metal in the SHB decreased the char yield and increased the tar yield, compared to the blank. The char and gas yields appeared to depend on the form of the metal salt used to prepare the SHB. However, the metal distribution in the product streams did not seem to be influenced by the chemical form of the metal salt used to prepare the SHB. Greater than 98.5% of the metal in the product stream was concentrated in the char formed by pyrolyzing and gasifying the SHB in the reactor. The metal concentration in the char varied between 0.7 and 15.3% depending on the type of metal in the SHB. However, the metal concentration was increased 4 to 6 times in the char compared to the feed.     

Characterization of the physicochemical and structural evolution of biomass particles during combined pyrolysis and CO2 gasification

The combination of pyrolysis and CO₂ gasification was studied to synergistically improve the syngas yield and biochar quality. The subsequent 60-min CO₂ gasification at 800 °C after pyrolysis increased the syngas yield from 23.4% to 40.7% while decreasing the yields of biochar and bio-oil from 27.3% to 17.1% and from 49.3% to 42.2%, respectively. The BET area of the biochar obtained by the subsequent 60-min CO₂ gasification at 800 °C was 384.5 m²/g, compared to 6.8 m²/g for the biochar obtained by the 60-min pyrolysis at 800 °C, and 1.4 m²/g for the raw biomass. The biochar obtained above 500 °C was virtually amorphous.     

Fixed-bed pyrolysis of safflower seed: influence of pyrolysis parameters on product yields and compositions

Fixed-bed slow pyrolysis experiments have been conducted on a sample of safflower seed 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 44% was obtained at the final pyrolysis temperature of 500°C, particle size range of +0.425–1.25 mm, with heating rate of 5°C min⁻¹ and sweep gas (N₂) flow rate of 100 cm³ min⁻¹ in a fixed-bed lab-scale reactor. Chromatographic and spectroscopic studies on the pyrolytic oil showed that the oil obtained from safflower seed can be used as a renewable fuel and chemical feedstock with a calorific value of 41.0 MJ/kg and empirical formula of CH_1.92O_0.11N_0.02.     

Effect of cellulose and lignin content on pyrolysis and combustion characteristics for several types of biomass

Fundamental pyrolysis and combustion behaviors for several types of biomass are tested by a thermo-gravimetric analyzer. The main compositions of cellulose and lignin contents for several types of biomass are analyzed chemically. Based on the main composition results obtained, the experimental results for the actual biomass samples are compared with those for the simulated biomass, which is made of the mixture of the cellulose with lignin chemical. The morphological changes before and after the reactions are also observed by a scanning electron microscope. The main compositions in the biomass consisted of cellulose and lignin. The cellulose content was more than lignin for the biomass samples selected in this study. The reaction for the actual biomass samples proceeded with the two stages. The first and second stage corresponded to devolatilization and char combustion during combustion, respectively. The first stage showed rapid mass decrease caused by cellulose decomposition. At the second stage, lignin decomposed for pyrolysis and its char burned for combustion. For the biomass with higher cellulose content, the pyrolysis rate became faster. While, the biomass with higher lignin content gave slower pyrolysis rate. The cellulose and lignin content in the biomasses was one of the important parameters to evaluate the pyrolysis characteristics. The combustion characteristics for the actual biomass depends on the char morphology produced.     

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.     

Detailed kinetic study of anisole pyrolysis and oxidation to understand tar formation during biomass combustion and gasification

Anisole was chosen as the simplest surrogate for primary tar from lignin pyrolysis to study the gas-phase chemistry of methoxyphenol conversion. Methoxyphenols are one of the main precursors of PAH and soot in biomass combustion and gasification. These reactions are of paramount importance for the atmospheric environment, to mitigate emissions from wood combustion, and for reducing tar formation during gasification. Anisole pyrolysis and stoichiometric oxidation were studied in a jet-stirred reactor (673–1173 K, residence time 2 s, 800 Torr (106.7 kPa), under dilute conditions) coupled with gas chromatography–flame ionization detector and mass spectrometry. Decomposition of anisole starts at 750 K and a conversion degree of 50% is obtained at about 850 K under both studied conditions. The main products of reaction vary with temperature and are phenol, methane, carbon monoxide, benzene, and hydrogen. A detailed kinetic model (303 species, 1922 reactions) based on a combustion model for light aromatic compounds has been extended to anisole. The model predicts the conversion of anisole and the formation of the main products well. The reaction flux analyses show that anisole decomposes mainly to phenoxy and methyl radicals in both pyrolysis and oxidation conditions. The decomposition of phenoxy radicals is the main source of cyclopentadienyl radicals, which are the main precursor of naphthalene and heavier PAH in these conditions.     

Hydro-upgrading of bio-oils derived from pyrolysis of biomass with different H/Ceff ratios in tetralin over Pt/C and Ru/C

Pyrolysis oils with different effective hydrogen (H/C_eff) ratios are mixed with tetralin at a mass ratio of 1:1 and treated at 400 °C for 2 h under 6 MPa H₂ over Pt/C and Ru/C, respectively, to examine the effect of H/C_eff ratio on the yield and quality of the upgraded oil. Pyrolysis oil with higher H/C_eff ratios results in an upgraded oil with higher yield and H/C_eff ratios. The highest S and O reduction ratios of 96.11% and 56.26% are achieved with added Pt/C at an H/C_eff ratio of 1.39 of the feedstock. In comparison, the highest N reduction ratios of 34.50% is achieved with added Ru/C at an H/C_eff ratio of 1.38 of the feedstock. The N and S poison the catalyst's active sites and reduce the deoxygenation efficiency. Thus, we view that the H/C_eff plays a vital role in improving the properties of the bio-oil.