煤热解过程中含氮气相产物转化规律的实验研究

为了研究煤在热解过程中含氮气相产物的生成规律,在滴管炉反应系统中对四种原煤以及两种脱除矿物质煤样分别在500℃、700℃、900℃和1100℃进行了实验研究。结果表明,随着温度的升高,作为NO前驱物的HCN和NH3的收率随之增加,N2的收率也增加。煤种对含氮气相产物的生成规律也有着较大的影响,煤化程度比较低的煤在热解过程中,燃料氮向气相含氮产物的转化率较高;煤化程度比较高的煤转化率则偏低,大部分的氮缩聚在多环芳香结构中,成为焦炭氮。煤中的矿物质对燃料氮向N2的转化起到了促进作用,而对燃料氮向HCN和NH3的转化起到了抑制作用。     

Experimental study and kinetic modeling of kerosene thermal cracking

Thermal cracking of kerosene for producing ethylene and propylene has been studied in an experimental setup. A set of experiments were designed using Response Surface Design (Box Behnken) method. In these experiments, the coil outlet temperature (COT), residence time and steam ratio varied from 795 °C, 0.13 s and 0.6 to 838 °C, 0.27 s and 1.0, respectively. Obtained maximum ethylene and propylene yield in these experiments were 32 and 16.9 wt.%, respectively. In next step of studies, we tried to develop an applicable kinetic model to predict yield distribution of products of the kerosene thermal cracking. Therefore, a reaction mechanism is generated on the basis of major reactions classes in the pyrolysis and feed compounds using some simplification assumptions in the model. This semi-mechanistic kinetic model contains 172 reactions, 22 molecular and 29 radical species. A sensitivity analysis was done on kinetic model and controlling reactions identified. An objective function was defined and used to tune the model with experimental data. Finally, the calculated model results were compared with the experimental data. Scatter diagrams showed good agreement between model and experimental data.     

Thermal self-sustainability of biochar production by pyrolysis

The pyrolysis of several agricultural and biofuel production residues (grape residues, sugarcane residues, dried distiller's grain, palm oil residues, apple pomace and forestry residue) has been carried out in a pilot bubbling fluidized bed pyrolyzer operating under a range of temperature from 300 to 600 °C and two vapor residence times (2 and 5 s), with the aim of determining their pyrolysis behavior including products yields and heat balance. The composition of the product gases was determined, from which their heating value was calculated. The liquid bio-oil was recovered with cyclonic condensers. The thermal sustainability of the pyrolysis process was estimated by considering the energy contribution of the product gases and of the liquid bio-oil in relation to the pyrolysis heat requirements. The most promising biomass feedstocks for the sustainable production of biochar were indentified. Furthermore, this study presented the char yield in relation to the excess heat that could be obtained by combusting the gas and bio-oil coproducts of biochar production, as functions of pyrolysis temperature and vapor residence time.     

油浆高温快速裂解过程的气固相产物研究

采用高频炉快速热解装置研究油浆的高温快速热解特性,考察了热解温度、氮气流量对气固相产物的组成和产率的影响。温度是影响气相产物产率的关键因素,气相产物主要为甲烷、氢气和乙烯,升高温度可提高甲烷和氢气的产率,而乙烯产率受高温下二次反应的影响在800℃到达最大值后逐渐降低,乙烷、丙烯产率较小且受二次反应的影响在700℃到达最大值后逐渐降低,温度高于800℃时会有少量乙炔生成且升温可提高乙炔产率。增加氮气流量可降低甲烷、氢气分压,缩短乙烯、丙烯等在高温区的停留时间,从而增加气相产物的产率。积炭产率随热解温度升高迅速增加,氮气流量的增加能够削弱二次反应从而降低积炭产率。     

Controlled-potential electrolysis of copper foil and graphite-coated copper foil in a nonaqueous 1 M LiPF6 in a ternary organic carbonate solvent

Controlled-potential electrolysis of battery-grade copper foil and graphite-coated copper foil electrodes in a typical lithium ion battery electrolyte (1 M LiPF₆ in propylene carbonate:ethylene carbonate:dimethyl carbonate [1:1:3 vol.]) was performed in order to construct Tafel plots to obtain values of the exchange current, i₀, and transfer coefficient, α. The transfer coefficients of both electrodes were found to be small (α = 0.25), which was consistent with an assumption of a dominant anodic process in the cell. At room temperature, the graphite-coated copper foil was found to have a higher exchange current than the copper foil. This can be explained by the intercalation of lithium ions into the graphite coating which increases the electron transfer rate. In the range of 0 °C to 50 °C, the exchange currents of both electrodes increased with temperature, but at different rates, while the transfer coefficients were not significantly affected by temperature.     

Kinetic models based in biomass components for the combustion and pyrolysis of sewage sludge and its compost

In the present work, pyrolysis and combustion of the sewage sludge (fresh and composted) have been simulated using five fractions: low stability organic compounds, hemicellulose, cellulose, lignin-plastic, and inorganic compounds. Thermal behavior and kinetic parameters (pre-exponential factor and apparent activation energy) of the main components of the sludge are similar to those reported for hemicellulose, cellulose, and lignin present in lignocellulosic biomass. Comparing non-isothermal thermogravimetric analysis data obtained from fresh and composted sewage sludge, it is possible to measure the efficiency of the composting process. Most of the biodegradable matter is volatized in a temperature range from 150 °C to 400 °C. Non-biodegradable organic matter volatilizes between 400 °C and 550 °C. In both, fresh and composted sludges, oxygen presence increases the mass loss rate at any temperature, but differences between pyrolysis and combustion are focused in two clearly defined ranges. At low temperature (200–350 °C), mass loss is related with a volatilization process. At higher temperature (350–550 °C), mass loss is due to slow char oxidation (oxidative pyrolysis).     

Bio-oil production from Onopordum acanthium L. by slow pyrolysis

In this study, the usability of the plant thistle, Onopordum acanthium L., belonging to the family Asteraceae (Compositae), in liquid fuel production has been investigated. The experiments were performed in a fixed-bed Heinze pyrolysis reactor to investigate the effects of heating rate, pyrolysis temperature and sepiolite percentage on the pyrolysis product yields and chemical compositions. Experiments were carried out in a static atmosphere with a heating rate of 7 °C/min and 40 °C/min, pyrolysis temperature of 350, 400, 500, 550 and 700 °C and particle size of 0.6 < D_p < 0.85 mm. Catalyst experiments were conducted in a static atmosphere with a heating rate of 40 °C/min, pyrolysis temperature of 550 °C and particle size of 0.6 < D_p < 0.85 mm. Bio-oil yield increased from 18.5% to 27.3% with the presence of 10% of sepiolite catalyst at pyrolysis temperature of 550 °C, with a heating rate of 40 °C/min, and particle size of 0.6 < D_p < 0.85 mm. It means that the yield of bio-oil was increased at around 48.0% after the catalyst added. Chromatographic and spectroscopic studies on the bio-oil showed that the oil obtained from O. acanthium L. could be used as a renewable fuels and chemical feedstock.     

重油催化裂解多产乙烯丙烯催化剂的研究

采用半合成法制备了不同金属改性的ZSM-5分子筛催化剂，以大庆VGO为原料，在固定床微型反应装置上对不同金属改性催化剂进行裂解生产低碳烯烃效果的评价，筛选出生产乙烯、丙烯性能较好的银+镧双金属改性催化剂，采用喷雾干燥的方法成型，并在800℃、100%水蒸气下老化处理4h。该催化剂在两段提升管实验装置上，以大庆AR为原料的评价结果表明，乙烯和丙烯收率可分别达到9.5%和24.9%；若考虑C4组分回炼，乙烯和丙烯收率可分别达到13.0%和29.9%。     

Study of the pyrolysis of municipal solid waste for the production of valuable products

To obtain information on the potential of thermal conversion (pyrolysis) of municipal solid waste (MSW), a thermogravimetric study (TGA) is performed in a stream of nitrogen. Based on TGA results, pyrolysis experiments are carried out in a semi-batch reactor under inert nitrogen atmosphere. Slow pyrolysis is performed up to 550 °C (heating rate of 4 °C/min). Fast pyrolysis is performed at 450, 480, 510 and 550 °C and different input transfer rates (12 or 24 g material/min). The pyrolysis products are studied on composition and yield/distribution and investigated for their use as valuable product.The liquid obtained by slow pyrolysis separates spontaneously in a water rich product and an oily product. For all fast pyrolysis conditions, a viscous, brown oil which contains a poly(ethylene-co-propylene) wax is obtained. Composition analyses by GC/MS of the oil products (slow/fast pyrolysis) show that aliphatic hydrocarbons are the major compounds. The pyrolysis oils have high calorific value (between 35 and 44 MJ/kg), low wt% of water (around 6 wt%) and a low O/C value (between 0.2 and 0.3). The presence of waxy material is probably due to incomplete breakdown of poly(ethylene-co-propylene) present in MSW under study. The optimal pyrolysis conditions, regarding to oil yield, fuel properties, and wax yield is fast pyrolysis at 510 °C with 24 g material/min input transfer rate. The fast pyrolysis gases contain mainly hydrocarbons and have an averaged LHV around 20 MJ/Nm³. ICP-AES analyses of pyrolysis products reveal that almost none of the metals present in MSW are distributed within the liquid fractions.     

Coal pyrolysis in a fluidized bed reactor simulating the process conditions of coal topping in CFB boiler

Simulating the conditions of pyrolytic topping in a fluidized bed reactor integrated into a CFB boiler, the study was devoted to the reaction fundamentals of coal pyrolysis in terms of the production characteristics of pyrolysis oil in fluidized bed reactors, including pyrolysis oil yield, required reaction time and the chemical species presented in the pyrolysis oil. The results demonstrated that the maximal pyrolysis oil yield occurred on conditions of 873 K, with a reaction time of 3 min and in a reaction atmosphere gas simulating the composition of pyrolysis gas. Adding H₂ and CO₂ into the reaction atmosphere decreased the pyrolysis oil yield, while the oil yield increased with increasing the CO and CH₄ contents in the atmosphere. TG-FTIR analysis was conducted to reveal the effects of reaction atmosphere on the chemical species present in the pyrolysis oil. The results clarified that the pyrolysis oil yield reached its maximum when the simulated pyrolysis gas was the reaction atmosphere, but there were slightly fewer volatile matters in the pyrolysis oil than the oil generated in the N₂ atmosphere. All of these results are expected not only to reveal the composition characteristics of the pyrolysis oil from different conditions of the coal topping process but also to optimize the pyrolysis conditions in terms of maximizing the light pyrolysis oil yield and quality.     

TGA–FTIR study of a lead zirconate titanate gel made from a triol-based sol–gel system

A Pb(Zr,Ti)O₃ precursor gel made from a sol prepared using 1,1,1,-tris(hydroxymethyl)ethane, lead acetate and zirconium and titanium propoxides, stabilised with acetylacetone, was analysed using TGA–FTIR analysis. Decomposition under nitrogen (N₂) gave rise to evolved gas absorbance peaks at 215 °C, 279 °C, 300 °C and 386 °C, but organic vapours continued to be evolved, along with CO₂ and CO until 950 °C. The final TGA step in N₂ is thought to relate to decomposition of an intermediate carbonate phase and the final elimination of residues of triol or acetylacetonate species which form part of the polymeric gel structure. By contrast, heating in air promoted oxidative pyrolysis of the final organic groups at ≤450 °C. In air, an intermediate carbonate phase was decomposed by heating at 550 °C, allowing Pb(Zr,Ti)O₃ to be produced some 400 °C below the equivalent N₂ decomposition temperature.     

Flash pyrolysis of grape residues into biofuel in a bubbling fluid bed

The pyrolysis of two grape residues (grape skins and the mixture of grape skins and seeds) has been carried out in a pilot bubbling fluidized bed pyrolyzer operating under a range of temperature from 300 to 600 °C and three vapor residence time (2.5, 5, and 20 s), with the aim of determining their pyrolysis behavior including products yields and heat requirements. The composition of the product gases was determined, from which their heating value was calculated. The liquid bio-oil was recovered with cyclonic condensers and separated into two phases, an aqueous phase and an organic phase. The chemical composition of these liquid phases was characterized. In addition, the environmental parameters of the distilled fraction (85–115 °C) of the aqueous phase were tested, while the heating value of the organic phase was determined. Furthermore, the thermal sustainability of the pyrolysis process was estimated by considering the energy contribution of the product gases and of the liquid bio-oil in relation to the pyrolysis heat requirements. The optimum pyrolysis temperatures were identified in terms of maximizing the liquid yield, maximizing the energy from the product bio-oil, and maximizing the net energy from the product bio-oil after ensuring a self-sustainable process by utilizing the product gases and bio-oil as heat sources.     

Catalytic Cracking of Lower-Valued Hydrocarbons for Producing Light Olefins

A number of important chemicals are made from light olefins such as propylene and ethylene, and it is expected that market demand for these light olefins will continue to grow at 4–5% annually, and the average overall growth of propylene will be about 1% higher than that of ethylene. From the viewpoint of supply of feedstock and demand of light olefins, it is anticipated that the thermal cracking process of naphtha will be gradually transformed to a catalytic process such as ACO^TM that can efficiently produce both ethylene and propylene in high yield. Also, together with primary light olefin production technologies utilizing heavy feedstocks such as DCC^TM, and HPFCC, supplementary propylene production technologies utilizing C₄–C₄ such as SUPERFLEX^TM, MOI^TM, and PROPYLUR^TM will be applied gradually in commercial production.     

The cleavage mechanism of 1,4-dithiaspiro(4.4)nonane by gas-phase pyrolysis

The initial product formed in the pyrolysis of 1,4-dithiaspiro(4.4)nonane (I) is the thioketone (7). During pyrolysis at 600 °C, this material has been isolated in absolute yields as high as 4.85%. The increase in yield of benzene (1), toluene (3), and naphthalene (14) as the temperature is increased from 600 to 800 °C could be anticipated from dehydrogenation under pyrolysis conditions.The other products isolated, with the exception of the rearrangement products and toluene, appear to arise via further pyrolytic reaction of thioketone (7). These saturated products are dehydrogenated by sulfur to generate the aromatic compounds.     

Characteristics of soot particles formed by diesel pyrolysis

This experiment involving diesel fuel pyrolysis was performed to study the process of soot formation without oxidation. The effects of temperature, residence time, and lubricating oil presence on soot formation were investigated through measurement of particle size distribution, morphology, and C/H ratio as well as through thermal analysis. The results show that the formation of soot during diesel pyrolysis depended strongly on both temperature and residence time. The critical temperature for the creation of soot with a primary particle diameter of 20 nm was about 1100 °C. Greater temperatures and residence times resulted in diesel soot particles that were more mature, i.e., with a higher C/H ratio, larger particle size, and higher ignition temperature. The carbonization of diesel soot through pyrolysis was also weakly affected by the addition of 5% lubricating oil to the diesel fuel. The results of this experiment provide information for modeling the formation of diesel soot without oxidation as well as for developing soot generators for after-treatment systems.     

Feedstock characterization and prediction of product yields for industrial naphtha crackers on the basis of laboratory and bench-scale pyrolysis

A new severity function has been introduced in order to plot and evaluate the yield data from hydrocarbon pyrolysis. It is demonstrated that the new severity function can also be used for the presentation of product yields obtained from hydrocarbon mixtures and naphtha fractions.In order to characterize and evaluate available feedstocks for olefin production, yields for seven naphtha fractions were determined in a bench-scale reactor. It was established that the yields of ethylene and propylene obtained from the different naphtha fractions increase proportionally with the increase in the characterization factor.On the basis of pyrolysis experiments carried out in laboratory, bench-scale and pilot reactors and in a commercial furnace it is shown that by using the new severity function the yield data obtained in reactors of different sizes and operating under different conditions can be directly compared and uniformly evaluated.The feasibility of micro-scale pyrolysis-gas chromatography for predicting product yields and evaluating naphtha feedstocks is also discussed.     

Gas Evolution from the Pyrolysis of Jordan Oil Shale in A Fixed-bed Reactor

Jordan oil shale from El-Lajjun deposit was pyrolysed in a fixed-bed pyrolysis reactor and the influence of the pyrolysis temperature between 400 to 620°C and the influence of the pyrolysis atmosphere using nitrogen and nitrogen/steam on the product yield and gas composition were investigated. The gases analysed were H₂, CO, CO₂ and hydrocarbons from C₁ to C₄. The results showed for both nitrogen and nitrogen/steam that increase the pyrolysis bed temperature from 400 to 520°C resulted in a significant increase in the oil yield, after which temperature the oil yield decreased. The alkene/alkane ratio including ethene/ethane, propene/propane, and butene/butane ratios, can be used as an indication of pyrolysis temperature and the magnitude of cracking reactions. Increasing alkene/alkane ratio occurring with increasing pyrolysis temperature. The alkene/alkane ratio for nitrogen/steam pyrolysis atmosphere was lower than the one found under nitrogen atmosphere. This revised version was published online in July 2006 with corrections to the Cover Date.     

基于Py-GC联用的煤快速热解实验研究

采用居里点裂解仪-气相色谱仪(Py-GC)联用的方法研究了4种煤的快速热解特性,分析了挥发分主要气相产物及其析出规律.结果表明,大于等于50%的挥发分在热解初期(t ≤ 2 s)释放,采用箔片装载方式的居里点裂解仪完全热解1 mg煤样需要10 s;挥发分主要气相产物中,各气体组分的生成量(mmol/g_coal)顺序为H₂ > CH₄ > CO > CO₂ > C2(C₂H₆、C₂H₄)> C3(C₃H₈、C₃H₆);挥发分释放量随热解温度的升高而增加,相同热解条件下,次烟煤挥发分的释放率高于贫煤和无烟煤;H₂和CH₄的生成量依赖于热解温度,热解温度越高,H₂和CH₄的生成量越多;CO和CO₂的生成量不仅与热解温度相关,而且与煤中的氧含量紧密相关,氧含量越高的煤热解生成的CO和CO₂越多;C2和C3气体的生成量相对于其他气体很少,体积占挥发分气相产物的5%.     

Optimization of catalytic, surface and magnetic properties of nanocrystalline manganese ferrite

Single-domain manganese ferrite nanoparticles have been synthesized with narrow particle size distribution using the combustion technique. Influence of fuel ratios on the as-prepared powders were characterized by XRD, SEM, VSM, N₂ adsorption at −196 °C and conversion of cyclohexene at 200–400 °C. Ratios of fuel to cations were maintained variously at 0.0, 0.67, 1.33 and 2.67.The fuel to cations ratio of 2.67 gives better yield in the formation of nanocrystalline Mn ferrite and single-domain particles with a narrow range of size distribution. Maximum magnetization and coercivity values of the investigated ferrite are also greater for the ratio of 2.67. These values measured at room temperature are found to be 68.58 emu/g and 62.57 Oe, respectively. The BET surface area of the investigated solids was found to decrease by increasing the ratio between fuel and cations due to increasing the flame temperature. However, this treatment resulted in a significant increase in catalytic activity of the as-synthesized solids. All solids investigated behaved as dehydrogenation catalysts. The change in fuel/cations ratios did not alter the mechanism of dehydrogenation of cyclohexene, but increased the concentration of active sites involved in the catalyzed reaction.     

Effect of silicon compounds on the pyrolysis of propane-butane hydrocarbon mixture

The effect of silicon-containing catalysts on the pyrolysis of propane-butane hydrocarbon mixture in a flow system was studied in the temperature range 500–850°C, the rate of the gas mixture flow 50–100 ml min⁻¹, contact time 0.1–12.0 s, and the value of the heterogeneity factor 0.1–2.1×10⁷ cm⁻¹. The catalytic activity of different systems under similar conditions was compared, and the influence of various factors on the yield of ethylene and propylene was studied. The most active silicon-containing catalyst for the pyrolysis of propane-butane hydrocarbon mixture was found.