Char‐formation kinetics in the pyrolysis of sawdust in a conical spouted bed reactor

Both the generation of a microporous structure and char formation kinetics have been studied in the pyrolysis of sawdust of Pinus insignis in a conical spouted bed reactor, in the range 350–700 °C. The BET surface area (representative of the physical evolution of the solid) and the C/H ratio of the solid (representative of the chemical structural change) have been taken as conversion indices. From the measurement of the C/H ratio of the solid (the more significant variable), it has been determined that the reaction order is 0.5 and that the kinetic constant is between 0.18 min⁻¹ at 350 °C and 1.26 min⁻¹ at 700 °C. However the value of the constant is almost independent of temperature, at 1 min⁻¹ in the range 500–700 °C. © 2000 Society of Chemical Industry     

Continuous pyrolysis of waste tyres in a conical spouted bed reactor

Continuous pyrolysis of scrap tyres has been carried out in a conical spouted bed reactor and the results (yields, composition of the volatile fraction and carbon black properties) have been compared with those obtained operating in batch mode in a previous study. Continuous operation in the 425-600 °C range gives way to a yield of 1.8-6.8 wt.% of gases, 44.5-55.0 wt.% of liquid fraction (C₅-C₁₀ range hydrocarbons, with a maximum yield of limonene of 19.3 wt.% at 425 °C), 9.2-11.5 wt.% of tar and 33.9-35.8 wt.% of char. The main differences between the continuous and batch processes are in the yield of light aromatics, which is higher in the continuous process, and in that of the heavy liquid fraction or tar, which is higher in the batch process. These are the advantages of the continuous process, although hydrogenation of the liquid fraction is required even in this case in order to use it as fuel. The high yield of limonene, the flexibility in the operating conditions and the capacity for a continuous removal of the residual carbon black from the reactor are the advantages of conical spouted bed technology. The excellent performance of the conical spouted bed reactor for the tyre pyrolysis process is due to the solid cyclic movement, the good contact between phases, the high heating rate and the reduced residence time of the volatile products.     

Investigations on heat transfer and hydrodynamics under pyrolysis conditions of a pilot-plant draft tube conical spouted bed reactor

This paper describes the hydrodynamic and heat transfer performance of a pilot-plant scale conical spouted bed reactor designed for the pyrolysis of biomass wastes. The spouted bed reactor is the core of a fast pyrolysis pilot plant with continuous biomass feed of up to 25 kg/h, located at the Ikerlan-IK4 facilities.The aim of this paper is to obtain a deeper understanding of the spouted bed reactor performance at pyrolysis temperatures, in order to operate under stable conditions, improve the heat transfer rate in the reactor and minimize energy requirements. The influence of temperature on conical spouted bed hydrodynamics has been studied and wall-to-bed and bed-to-surface heat transfer coefficients have been determined.     

Recycling poly-(methyl methacrylate) by pyrolysis in a conical spouted bed reactor

The pyrolysis of poly-(methyl methacrylate) (PMMA) has been studied in a pyrolysis plant provided with a conical spouted bed reactor. This reactor is an interesting technology for the pyrolysis of waste plastics due to its excellent hydrodynamic behaviour and its high heat transfer and versatility. A previous kinetic study was carried out in thermobalance, in which the degradation of this polymer was observed to begin at low temperatures, 553 K. Consequently, the activation energy is low compared to other plastics. The influence of temperature on pyrolysis product distribution in the conical spouted bed reactor has been studied in the 673–823 K range. The products obtained at low temperatures are mainly the monomers of the polymer used for the study methyl methacrylate (MMA) and ethyl acrylate (EA). When the pyrolysis temperature is increased, the yield of monomers is lower due to the higher severity of secondary reactions, and there is a significant increase in the yield of gases. The maximum monomer recovery has been obtained at 673 K, with the yields of MMA and EA being 86.5% and 6.2%, respectively.     

Prediction of spouted bed reactor performance using kinetic models

The form of the equation governing the kinetic model of a reactor depends on the mixing regime of the reacting phases and the conversion kinetics. The formation of detached flow in a spouted-bed reactor results in backmixing of the solid material. Therefore, the processes in a spouted-bed reactor can be described by a diffusion (quasihomogeneous) model equation. The paper compares the values of the production capacity of a spouted-bed reactor calculated using the diffusion model with experimental values of the efficiency of green ultramarine oxidation (kinetic region), of oxidative calcination of some metal sulphides (mixed region), and of the ion exchange extraction of copper from solutions (diffusion region). The kinetics of the corresponding conversions are also described.     

Mathematical modeling of polyethylene terephthalate pyrolysis in a spouted bed

A model has been developed for pyrolysis of polyethylene terephthalate (PET) in a spouted bed reactor based on the conservation equations for heat, mass, and momentum transports. A spouted bed has been constructed and the kinetic parameters have been obtained within the temperature range of 723–833 K, using two particle size ranges, (0.1–1.0) × 10^?3 and (1.0–3.0) × 10^?3 m. The model' predictions for the radial distributions of temperature and concentration confirm the excellent mixing of particles. Thus, spouted beds are appropriate equipments for performing kinetic studies of PET pyrolysis. The inlet gas temperature and the mass of PET highly affect PET conversion. The amount of inert particles has a negligible effect on the conversion and it can be reduced as far as a stable spouting is preserved. The gas flow suffices to eliminate the external heat and mass‐transfer limitations. It can be reduced to the minimum value to decrease the energy consumption. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1900–1911, 2015     

Modeling the thermochemical degradation of biomass inside a fast pyrolysis fluidized bed reactor

A fast pyrolysis process in a bubbling fluidized bed has been modeled, thoroughly reproduced and scrutinized with the help of a combined Eulerian/Lagrangian simulation method. The 3‐D model is compared to experimental results from a 100 g/h bubbling fluidized bed pyrolyzer including such variables as particle composition at the outlet and gas/vapor/water yields as a function of fluidization conditions, biomass moisture concentrations, and bed temperatures. Multiprocessor simulations on a high‐end computer have been carried out to enable the tracking of each of the 0.8 million individual discrete sand and biomass particles, making it possible to look at accurate and detailed multiscale information (i.e., any desired particle property, trajectory, particle interaction) over the entire particle life time. The overall thermochemical degradation process of biomass is influenced by local flow and particle properties and, therefore, accurate and detailed modeling reveals unprecedented insight into such complex processes. It has been found, that the superficial fluidization velocity is important while the particle moisture content is less significant for the final bio‐oil yield. © 2011 American Institute of Chemical Engineers AIChE J, 58: 3030–3042, 2012     

Biomass pyrolysis in a circulating fluid bed reactor for the production of fuels and chemicals

An approach for biomass flash pyrolysis in a circulating fluid bed (CFB) reactor with continuous solids regeneration is described in this study. The unit is capable of performing conventional and catalytic biomass pyrolysis with the proper solid selection. The production of improved quality liquid products in a direct step through catalytic pyrolysis is investigated in this work. Both conventional and catalytic biomass pyrolysis can be effectively performed in this CFB unit. Flash pyrolysis conditions were achieved and liquid product yields of ∼70 wt% (on biomass feed) were obtained. The effect of specific operating variables including the type of inorganic solid material and the solid/biomass ratio was established on the final liquid product quality and yield. Solid materials considered included silica sand, a commercial fluid catalytic cracking catalyst and a ZSM-5 additive. Catalytic biomass pyrolysis generally leads to the production of additional water, coke and gases compared to conventional pyrolysis. However, the obtained liquid product quality and composition is improved.     

Ash-agglomerating gasification of coal in a spouted bed reactor

Australian bituminous coal (Hoskisson) was gasified with oxygen and steam in a 0.4m diameter spouted bed reactor at atmospheric pressure and temperatures of 1050–1170 °C to produce medium calorific value gas. High-ash agglomerates fell through the throat of the spouted bed under restricted gasification conditions, with no simultaneous loss of coal. The effects of temperature, steam-oxygen ratio, coal feed rate and coal size on carbon conversion, production of ash agglomerates, gas composition and decompsition of steam were established.     

Catalytic upgrading of woody biomass derived pyrolysis vapours over iron modified zeolites in a dual-fluidized bed reactor

In this paper, the influence of the proton forms of beta, Y and ferrierite zeolites and their iron modified counterparts during upgrading of pine wood pyrolysis vapours under nitrogen atmosphere was investigated. A dual-fluidized bed reactor was used where in the first bed pyrolysis of pine wood occurred, and in the second upgrading of the pyrolysis vapours over zeolites was conducted. The temperature for pyrolysis and upgrading was 400 and 450 °C, respectively. De-oxygenation reactions over the proton form and iron modified zeolites increased compared to the non-catalytic pyrolysis. The increased selectivity towards organic compounds through de-oxygenation could be noticed as a higher water yield and CO formation.     

Pyrolysis with partial combustion of oil shale fines in a spouted bed

Pyrolysis with partial combustion of oil shale fines from the Irati Formation in Brazil has been investigated in a 30 cm diameter spouted bed reactor. Experiments were carried out at atmospheric pressure and temperatures between 450 and 600°C. The oi] shale particle size was less than 6.35 mm. Spouting gas temperatures ranged from 20 to 565°C. Three inlet gas pipe diameters and two spouted bed heights were studied. Operation of the process was found to be stable over a wide range of test conditions. Results are presented for oil and gas quality, efficiency of retorting and overall performance of the plant.     

流化床粉煤气体热载体快速热解反应器的计算

在冷态模拟实验和煤热解动力学计算的基础上,对粉煤气体热载体快速热解提升管反应器的高度进行了计算。利用高速摄像粒子测速法结合互相关算法研究了不同气体流量和不同颗粒粒径时固体颗粒在热解提升管中的运动速度,通过求解神府煤热解动力学方程,得到了不同粒径神府煤颗粒热解挥发分析出的时间,从而确定了快速热解提升管反应器的高度。研究结果表明:当气体流量在850 m3/h,粉煤的粒径主要集中在0.7—3.0 mm时,提升管的高度应选择在10.0 m。     

Production of aromatics by catalytic fast pyrolysis of cellulose in a bubbling fluidized bed reactor

Catalytic fast pyrolysis of cellulose was studied at 500°C using a ZSM‐5 catalyst in a bubbling fluidized bed reactor constructed from a 4.92‐cm ID pipe. Inert gas was fed from below through the distributor plate and from above through a vertical feed tube along with cellulose. Flowing 34% of the total fluidization gas through the feed tube led to the optimal mixing of the pyrolysis vapors into the catalyst bed, which experimentally corresponded to 29.5% carbon aromatic yield. Aromatic yield reached a maximum of 31.6% carbon with increasing gas residence time by changing the catalyst bed height. Increasing the hole‐spacing in the distributor plate was shown to have negligible effect on average bubble diameter and hence did not change the product distribution. Aromatic yields of up to 39.5% carbon were obtained when all studied parameters were optimized. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1320–1335, 2014     

Catalytic pyrolysis of woody biomass in a fluidized bed reactor: Influence of the zeolite structure

Catalytic pyrolysis of biomass from pine wood was carried out in a fluidized bed reactor at 450 °C. Different structures of acidic zeolite catalysts were used as bed material in the reactor. Proton forms of Beta, Y, ZSM-5, and Mordenite were tested as catalysts in the pyrolysis of pine, while quartz sand was used as a reference material in the non-catalytic pyrolysis experiments. The yield of the pyrolysis product phases was only slightly influenced by the structures, at the same time the chemical composition of the bio-oil was dependent on the structure of acidic zeolite catalysts. Ketones and phenols were the dominating groups of compounds in the bio-oil. The formation of ketones was higher over ZSM-5 and the amount of acids and alcohols lower than over the other bed materials tested. Mordenite and quartz sand produced smaller quantities of polyaromatic hydrocarbons than the other materials tested. It was possible to successfully regenerate the spent zeolites without changing the structure of the zeolite.     

Non-isothermal modeling of the flue gas desulphurization process using a semi-dry spouted bed reactor

A mathematical model is developed for investigation of SO₂ removal in a powder particle spouted bed (PPSB) for non-isothermal operating condition. For this aim, the stream-tube model which was already validated for such systems is applied for hydrodynamics of solid and gas phases, and then by using the conservation laws of mass and energy, the governing equations for gas and solid phases are derived and solved numerically. The published experimental data in the literature are used to validate the accuracy of the proposed model. The results show that the model is capable of predicting the behaviour of this system properly. Also the optimum performance of this system is investigated by studying the effects of different parameters such as bed height, molar ratio of sorbent to acid gas (Ca/S) and inlet concentration of SO₂.     

Experimental investigation of solid particles flow in a conical spouted bed using radioactive particle tracking

Solid particles flow in a conical spouted bed is characterized by radioactive particle tracking. The influence of operating conditions on key parameters of this flow is evaluated and discussed: the morphology of the solid bed is not strongly influenced by the forces exerted by the gas on the solid particles, but rather by geometrical considerations; the particles spend approximately 8% of their time in the spout in all experiments; it is the force exerted on the solid particles by the gas that directly controls the volumetric flow rate between adjacent regions, and not the amount of particles in the bed; as U/U_ms increases, the volume of solid particles in the annulus decreases, the volume of solid particles in the fountain increases and the volume of solid particles in the spout remains constant. Correlations to predict key flow parameters as functions of operating conditions are also established and discussed. © 2015 American Institute of Chemical Engineers AIChE J, 62: 26–37, 2016     

麦秸快速热解的试验研究

介绍了喷动流化床(喷动床)快速热解试验装置及方法,研究了主要影响因素———热解温度对麦秸热解气、液、固三种产品的产率和热解气成分的影响,采用色-质谱联用仪(GC-MS)分析了热解液成分。结果表明,热解温度为460~520℃时热解油产率最大,主要有醋酸、羟基乙醛、羟基丙酮、左旋葡聚糖、糠醛,油热值为17.0MJ.kg-1;热解气主要为CO2和CO,还含有少量H2、CH4和C2~C4的烯烃。     

循环流化床煤燃烧/热解双反应器系统稳定性分析

为了考察循环流化床煤燃烧/热解双反应器系统的稳定性,在冷态实验装置上以电厂锅炉灰为实验物料,其中提升管的内径为100 mm,高为6.7 m,与热解室相连立管的内径为44 mm,高3 m,热解室的截面积为200 mm×200 mm,高770 mm。分别考察了影响系统稳定运行的主要因素,并对系统中存在的几对平衡关系进行了分析。结果表明,旋风料腿内的固体料位高度、热解室内的料位高度以及热解室内的压力等是影响系统稳定运行的关键因素,尤其是热解室内压力的增加有可能使立管内料封破坏,最终导致系统瘫痪。而提升管与热解室立管之间压力的平衡以及提升管与旋风分离器料腿之间压力的平衡等在操作过程中必须保持稳定,否则也会发生窜气、架料、旋风分离器效率下降等现象,影响系统稳定运行。     

Analysis of the dynamics of paste drying in a spouted bed

Although there are some models available in the literature for paste drying in spouted beds, few of them have focused on transient analysis of dynamical systems. Our objective was to integrate experiments and simulations of a dynamic model to investigate the transient response to disturbances and interruptions in the feed flow during paste drying in a spouted bed with inert particles. The spouted bed consisted of a cylindrical column with 50.0?cm of height and 20.0?cm of diameter. Drying tests were performed at inlet gas temperatures of 70?°C and 100?°C and inlet air flow 30% above the minimum spouting velocity. A 5% w/w suspension of calcium carbonate was used as paste material, and glass spheres of 2.2?mm were used as inert materials. Different patterns of step function changes were tested in the paste feed flow rate. A lumped parameter model was used to predict mass and heat transfer during the drying. Experiments and simulations were in good agreement.     

Desulfurization of coal by air + steam at 400°C in a fixed bed

A high-volatile coal was treated by mixtures of air and steam at 400°C. The coal particle size, air/steam ratio and treatment time were varied. The degree of conversion of total sulfur depended on the particle size (but not proportionally) and the air/steam ratio (proportionally). The kinetics of the heterogeneous desulfurization by oxidation of FeS/FeS₂ was investigated. The kinetic data were well described by the model of an unreacted shrinking core in a coal particle of unchanging size. The coal particle size affected the external and internal diffusion of O₂ molecules only; the air/steam ratio affected the internal diffusion of O₂ molecules only. On average, the process was governed 14% by external diffusion, 76% by internal diffusion and 10% by chemical reaction. It was possible to elucidate the desulfurization mechanism merely from a knowledge of the experimental relation between total sulfur conversion degree and treatment time.