Fluidizing Gas Flow Rate Research Articles

An XCT study on three-dimensional characteristics of a spout-fluid bed

Spout-fluid beds are widely used in the chemical and petrochemical industries for excellent mixing and heat and mass transfer properties. Understanding the behavior of jets in spout-fluid beds is crucial for optimizing these processes. In this paper, we present a novel experimental method for studying the three-dimensional characteristics of jets in spout-fluid beds using X-ray computed tomography. By employing a gas–solid flow parameter measurement system, we propose an accurate experimental fitting method for voxel voidage values, enabling the three-dimensional reconstruction of the time-averaged voidage in the entire flow field of a spout-fluid bed. These data are then used to develop an image processing algorithm for identifying and quantifying gas jets in the flow field, allowing for measures of jet length, volume, and diameter. We further investigate the effects of static bed height, spouting gas velocity, and fluidizing gas flowrate on the three-dimensional characteristics of jets.

Bio-oil from biomass fast pyrolysis: Yields, related properties and energy consumption analysis of the pyrolysis system

Based on a comprehensive study of biomass fluidized bed device, a fast pyrolysis experiment to produce bio-oil was carried out using rice husks as raw material. The effects of reaction temperature, fluidized gas volume, and feed rate on the yield of bio-oil were studied. Experiments showed that the best temperature for bio-oil yield was 500 °C, the best fluidizing gas flow rate was 22 m³/h and the best feed rate was 2.65 kg/h. The physical and chemical properties of bio-oil were analyzed, and the results showed that the density, acidity, calorific value, and viscosity of the first-level bio-oil were greater than those of the second-level bio-oil. Among the components, the contents of acids (18.74%), ketones (22.51%), esters (16.90%), and phenols (17.91%) were relatively high. Aspen Plus software was used to analyze the energy consumption of the reaction model. Most of the energy in the fast pyrolysis of biomass is consumed for the preheating and cooling of nitrogen, which accounts for 60% of the total energy consumption. The combustion of the coke and non-condensable gas, which are produced as by-products can be used for preheating raw materials to realize self-heating production. Combine experiment and simulation will promote its industrialization.

A Study on Catalyst Entrainment from the Ethylene Oxychlorination Fluidized Bed Reactor

During the production of ethylene dichloride, the entrainment of catalyst particles out of the bed is considered a problematic issue that affects the conversion of the hydrogen dichloride and causes repeated unit shut down. In this study the effect of the various operating conditions was measured; the fluidizing gas flowrate, the bed parameters, the reaction conditions, and the static design parameters such as the internal orifice diameter of the distributer. A simulation model was built using Mat Lab and Aspen Plus software. The results from both models were compared with the sample analysis data obtained from the laboratory. It was found that when the entering gas flow rate reached 2570.4 m3/hr, the bubble diameter of the fluidizing gas reached maximum value, and hence, the entrainment of catalyst particles was at the lowest quantity of about 8.2 Kg/m2.s. In addition, it was found that as the pressure drop through the orifice of the distributer decrease the entrainment of solids increase until an orifice diameter of 1 cm is reached, hence, the lowest rate of entrainment of catalyst particles is achieved. at such conditions the highest conversion of ethylene and HCL into Ethylene dichloride could be reached.

Systematic production and characterization of pyrolysis-oil from date tree wastes for bio-fuel applications

The prevailing trends in global energy consumption and the rapid depletion of fossil fuel present an urgent need for alternative fuels, particularly from renewable sources of biomass. In this study, date palm tree mixture wastes (DTM) and date seed (DS) biomass were used as starting materials in the production of bio-oil by pyrolysis. The yields of the pyrolysis oils from DTM and DS were optimized by tuning the experimental parameters. The DS provided a maximum yield of 68 wt% obtained from 30 min of pyrolysis with a biomass loading of 200 g, fluidizing gas flow rate of 10 mL min−1, and at a temperature of 500 °C. In addition, we evaluated the impact of the aging process of the obtained pyrolysis oils. The produced pyrolysis oils (freshly made) were aged for 15 and 30 days at room temperature under closed conditions. All the feedstock biomass were subjected to proximate and ultimate analysis. The TG-DTA results indicated that both biomasses were richer in cellulose and hemicellulose contents than in lignin content. The FT-IR and GC/MS analyses of the fresh and aged oil samples demonstrated the outstanding characteristics of the DS derived bio-oil for use as a bio-fuel. The variation in the chemical composition of the fresh and aged pyrolysis oils are completely described and presented elaborately. This study demonstrates the significance of and a new functionality for the date palm industry to process date palm wastes, particularly the DS as a rich biomass source for the production of bio-fuel.

Fluidized bed fast pyrolysis of corn stover: Effects of fluidizing gas flow rate and composition

ABSTRACT Fast pyrolysis of corn stover was carried out in a pilot scale fluidized bed reactor in nitrogen atmosphere. The effects of varying gas flow rates at optimum reaction temperature of about 500ºC and feed size of < 1.0 mm on yield and composition of bio-oil, char and gas were investigated. The results for three runs with flow rate of gas of 45, 80 and 70 L/min, respectively, were obtained. The distribution of pyrolysis products was calculated gravimetrically by mass balance and corrected with optimization mass model using proximate and ultimate analysis of feedstock and pyrolysis products. The maximum yield of bio-oil (52 wt%) was obtained in run 3 with flow rate of gas of 70 L/min having heating value of 21.20 MJ/kg. GC-MS analysis identified the major chemical compounds present in the bio-oil which were levoglucosan, hydroxyl acetaldehyde, acetol, acetic acid, phenols, 2-methyl-2-cylopenten-1-one, guaiacol, 2(5H)-furanone, fufuryl alcohol, p-cresol and 2-ethyl alcohol. The bio-oil produced from run 3 had higher amounts of aromatic hydrocarbons, non-methoxylated phenolics, levoglucosan and smaller amounts of acids. On the other hand, bio-oil obtained from TGRP experiments had low value of total acid number (57.73 mg of KOH/g) indicating less oxygenating compounds with greater heating value in the product.

Innovative utilization of refractory iron ore via suspension magnetization roasting: A pilot-scale study

In this study, an innovative suspension magnetization roasting (SMR) technology was developed and utilized for the recovery of iron from a typical refractory iron ore. The effects of the roasting temperature, CO reducing gas flow rate, N2 fluidizing gas flow rate, and feeding rate on the iron recovery were investigated. Under the optimal roasting conditions, a continuous and stable pilot scale SMR test was conducted for 72 h, and a staged grinding and staged low-intensity magnetic separation (LIMS) process was designed to upgrade the roasted product. The results showed that with the appropriate SMR conditions — a roasting temperature of 520 °C, CO flow rate of 4.0 m3/h, N2 flow rate of 2.0 m3/h, and feeding rate of 100 kg/h — an iron concentrate with a total iron grade (TFe) of 60.18% and iron recovery of 90.17% could be obtained. Compared to the traditional process of shaft furnace magnetization roasting (SFMR) followed by LIMS, the novel technique developed here could improve the TFe and iron recovery of the iron concentrate by 12–14% and 17–22%, respectively, with well-functioning equipment. During the SMR process, hematite and siderite were transformed into magnetite, which enhanced the magnetism of the iron minerals. The utilization of the SMR method has the potential to provide a significant technological advance in the field of refractory iron ore recovery in China and globally.

A Hydrodynamic Study of Chemical Looping Combustion System for Gaseous Fuel

Chemical looping combustion (CLC) is a promising technology for fossil fuel combustion with inherent CO2 capture and sequestration that is able to mitigate greenhouse gases (GHGs) emission. The CLC process employs metal oxide as an oxygen carrier circulating between fuel reactor, where the fuel is combusted to CO2 and H2O, and air reactor, where the oxygen carrier returned to its oxidized form by aeration. In order to demonstrate and investigate the CLC concept experimentally, several previous studies have been carried out with the aim of improving the performance of oxygen carrier. The performance of the oxygen carrier, which circulate between the air reactor and the fuel reactor to transfer oxygen and heat, is the most important factor that determines the efficiency of the CLC process. In order to evaluate the reactivity of the oxygen carrier, the fuel conversion and CO2 selectivity of oxygen carrier have been investigated using thermogravimetric analyzer, batch type bubbling fluidized bed, etc. However, the hydrodynamic study for the solid circulation of oxygen carrier should be preceded to ensure the steady state operation of CLC process. In this study, the characteristics of solid circulation between the air reactor and the fuel reactor was examined in the bench scale CLC unit made of Plexiglas, and the effects of change of fuel reactor configuration and cyclone on the solid circulation between the two reactors were investigated. Ni based oxygen carrier was used as the bed material and the optimal fluidizing gas flow rate capable of maintaining stable solid circulation were investigated.

Modelling of particle flow in a dual circulation fluidized bed by a Eulerian-Lagrangian approach

Understanding the particle dynamics is of paramount importance to the design, operation and optimization of looping combustion reactors. In this paper, a three-dimensional Eulerian-Lagrangian model was developed to study the particle flow in a dual circulating fluidized bed consisting of an air reactor and a fuel reactor. Based on the Multi-Phase Particle-In-Cell (MP-PIC) scheme, the turbulent gas motion was simulated by the large eddy simulation (LES) and the particle flow simulated by the discrete particle method, with the particle size distribution (dp = 0–108 μm) being fully taken into account. The effects of particle size, particle density, initial bed inventory and fluidizing gas flow rate were numerically studied. The results show that small particles mainly distribute in the fuel reactor while large particles tended to stay in the air reactor, leading to an unfavorable influence on the efficiency of metal oxide. The increase of particle density led to the increase of global and internal circulation rates. A high initial bed inventory would result in a high particle concentration and lower axial velocities of particles. When increasing the fluidizing gas flow rate in the fuel reactor, the internal particle circulation rate increased gradually; however, the global particle circulation rate decreased. The results should be useful for the design and control of dual circulating fluidized bed, looping combustion reactors.

Production of Bio-oil through Fast Pyrolysis of Baobab Waste Shells

The increasing demand for transportation fuel, due to increased urbanization, is now compounded by depleting and unstable crude oil reserves. Furthermore, the volatile market and the negative environmental impact of fossil fuels have driven the usage of biomass as a potential energy source. Of particular interest are biomass waste and baobab shells present an interesting option. The objective of this study is to produce bio oil by a fast pyrolysis process from baobab shells. The effect of reaction temperature, biomass particle size and fluidizing gas flow rate on the liquid product yield are investigated. The maximum liquid yield obtained was 36.6% at 500 OC at a N2 gas flowrate of 11.6 l/min and a particle size of less than 0.5 mm.

Production of Bio-oil through Fast Pyrolysis of Baobab Waste Shells

The increasing demand for transportation fuel, due to increased urbanization, is now compounded by depleting and unstable crude oil reserves. Furthermore, the volatile market and the negative environmental impact of fossil fuels have driven the usage of biomass as a potential energy source. Of particular interest are biomass waste and baobab shells present an interesting option. The objective of this study is to produce bio oil by a fast pyrolysis process from baobab shells. The effect of reaction temperature, biomass particle size and fluidizing gas flow rate on the liquid product yield are investigated. The maximum liquid yield obtained was 36.6% at 500 OC at a N2 gas flowrate of 11.6 l/min and a particle size of less than 0.5 mm.

Sensitivity study of a full-scale industrial spray-injected fluidized bed reactor

The industrial fluidized bed reactor (FBR) described here is designed to convert an aqueous solid laden stream into a consistent granular product. The FBR is heated to 650 °C and chemically reducing conditions are achieved by using steam as the fluidizing gas and coal as a source of carbon. The objective of this study is to use the MFiX (Multiphase Flow with Interphase eXchanges) two-fluid model as a screening tool to investigate the effects of off-nominal conditions to establish performance guidelines. This information will be helpful in assessing whether the identified boundaries of the system are steep or gradual. Initially, 13 independent operating parameters were sampled in a one-at-a-time manner using high, low, and base values and ranked against a set of performance criteria indicative of defluidization. Five operating parameters were found to have the largest effect (bed particle size, bed particle density, coal particle size, spray feed flow rate, and fluidizing gas flow rate) on three quantities of interest—bed differential temperature, low solids velocity, and bed voidage. Latin-hypercube sampling was used to generate a minimal number of random values for various combinations of input parameters. The spray feed flow rate was the most significant parameter affecting the temperature differences, followed by the coal particle and bed particle size. The bed particle size had the largest effect on the low velocity of the bed particles, with the coal particle size as a contributing second effect. The high solid packing shows the coal particle size with the largest effect, and significant secondary contributions from the feed flow rate and fluidizing gas flow rate. The fits to the five-dimensional Gaussian Process models were 0.7797, 0.8664, and 0.9440 for the temperature, velocity, and solids packing, respectively.

Process simulation and thermodynamic evaluation for chemical looping air separation using fluidized bed reactors

Chemical looping air separation (CLAS) is considered as a promising method for providing an efficient and economic oxygen supply for integration into oxy-fuel combustion power plants. This study is the first to develop a process model, identify the process characteristics, and optimize the thermodynamic behavior for CLAS processes using fluidized bed reactors. In the process developed model, a fast fluidized bed model and a bubbling fluidized bed model are used to respectively represent the oxidation reactor and the reduction reactor, while fluidized bed hydrodynamics and oxygen carrier redox reaction kinetics are considered to grasp the unique characteristics of CLAS process. The effects of operating parameters on CLAS operation are identified and observed that high reduction temperature and high fluidizing gas flow rate can enhance oxygen carrier conversion and reduce energy penalty in the reduction reactor. Multi-variable optimization to minimize specified energy consumption illustrates that, 38.1% energy savings can be achieved and the optimal oxidation operating temperature, reduction operating temperature, air flow rate, and fluidizing gas flow rate are determined as 830 °C, 950 °C, 1133.7 L/h, and 58.4 L/h, respectively. These results are valuable for use by engineers to optimize the process design and achieve energy-efficient operation for CLAS processes.

Effect of Operating Conditions on Discharge Characteristics of Petroleum Coke Powder from a Top-Discharge Blow Tank at High Pressure

Discharge experiments of petroleum coke powders were carried out in a pilot-scale top-discharge blow tank at high pressure. The effects of operating conditions (including fluidizing gas flow rate, blow tank pressure, differential pressure between blow tank and receiving tank, supplementary gas flow rate) on solid discharge rate and solid loading ratio were investigated. The results indicate that the maximum solid discharge rate corresponds to the most effective fluidization of the powders near the riser inlet when the fluidizing gas flow rate reaches a critical value. The solid loading ratio shows the same variation tendency as solid discharge rate with increasing fluidizing gas flow rate, which first increases then decreases. Increasing blow tank pressure can improve the fluidization of powders in the tank, which contributes to the increase of solid discharge rate; however, it would not change the basic discharge law. As the differential pressure between blow tank and receiving tank increases, the solid discharge rate increases, while the solid loading ratio first increases then decreases. Solid discharge rate and solid loading ratio both decrease as supplementary gas flow rate increases. A modified solid discharge rate prediction model is proposed for the top-discharge blow tank at high pressure with errors below ±12%.

Fast Pyrolysis in a Microfluidized Bed Reactor: Effect of Biomass Properties and Operating Conditions on Volatiles Composition as Analyzed by Online Single Photoionization Mass Spectrometry

The real-time analysis of volatiles (primary tar) produced during the fast pyrolysis of biomass in a microfluidized bed reactor (MFBR) is achieved by online single photoionization mass spectrometry (SPI-MS). The effect of biomass composition (Douglas fir, oak, and miscanthus), particle shape and size (cylinder, lamella, or powder), bed temperature, and fluidizing gas flow-rate on primary tar composition is studied. Principle component analysis is conducted on the major ions analyzed by SPI-MS to evidence the significant differences between conditions. The variance in obtained SPI-MS spectra reveals the important effect of biomass composition and temperature on volatiles composition. The effect of particle size on volatiles composition is clearly evidenced. Typical pyrolysis regimes are defined according to specific markers which are key chemical compounds to characterize biomass fast pyrolysis. SPI-MS combined with a MFBR is an interesting tool to unravel the effects of biomass composition and of heat and mass transfers on biomass fast pyrolysis processes.

Analysis of the Rice Husk Pyrolysis Products from a Fluidized Bed Reactor

Rice husks are pyrolyzed in a fluidized bed pyrolyzer using glass beads as the fluidizing media. The effects of the rice husk feeding rate and the fluidizing nitrogen gas flow rates on the mass fraction of the produced syngas, bio-oil and char are studied. The highest bio-oil mass fraction in the product is around 30% when the rice husk feeding rate and the fluidizing nitrogen gas flow rate are 10g/min and 40 L/min, respectively. The chars collected at different parts of the system are analyzed by TGA. The results indicate that although the chars have different content of volatiles, they are relatively clean. GC/MS analysing results indicate that the major compounds in the bio-oil are aromatic compounds, including toluene, phenol, furfural, methylphenol, ethylphenol, benzenediol, and etc.

Study on the flow behavior in spout-fluid bed with a draft tube of sub-millimeter grade silicon particles

An experimental study on gas-particle flow behavior in a spout-fluid bed with a draft tube was performed in a 182mm diameter cylindrical column with a flat distributor. Sub-millimeter grade silicon particles with wide particle size distribution were used as bed materials to investigate the effect of operating conditions and geometrical parameters on the flow behavior. The pressure drop and its standard deviation were recorded using a capacitive differential pressure transducer, which can be applied to evaluate the hydrodynamic properties. The effects of fluidizing gas and geometrical parameters of the bed on the hydrodynamic characteristics were analyzed. The results show that the minimum spout-fluidizing velocity increases with increasing the length of entrainment zone and the draft tube diameter, but it decreases with the increasing of fluidizing gas flow rate and static bed height. Furthermore, a correlation on the minimum spout-fluidizing velocity which has practical value is proposed based on the present experimental data, and the calculated data is in good agreement with the experimental results. In addition, seven flow regions can also be observed in different spouting and fluidizing gas velocity, and a new flow regime map for a spout-fluid bed is established with the consideration of the influence of flow regime on geometrical parameters. Such results mentioned above can provide important information on the flow behavior in the spout-fluid bed with a draft tube for process design.

Effect of Operating Conditions and Powder Properties on Pneumatic Conveying Characteristics of a Top Discharge Blow Tank

AbstractThe effects of fluidizing and pressurizing gas flow rates on pneumatic conveying characteristics such as powder mass flow rate, solid‐gas ratio, and voidage in a top discharge blow tank pneumatic conveying system are evaluated. Pulverized coal and glass beads were used to investigate the effect of powder properties on conveying performance. The results indicate that as the fluidizing gas flow rate increases, the powder mass flow rate and the solid‐gas ratio increase at first and then decline. As the pressurizing gas flow rate increases, the powder mass flow rate increases gradually, while the solid‐gas ratio increases at first and then declines. Since the voidage values of all experiments are below 0.95, it can be inferred that the top discharge blow tank pneumatic conveying system is able to achieve dense‐phase conveying.

Experimental flow behaviors of irregular particles with silica sand in solid waste fluidized bed

Co-fluidization characteristics of irregular particles with bed material have been investigated. Experiments were carried out in a solid waste fluidized bed with cross section of 0.2 m × 0.2 m and height of 2 m. Four particles differing in shapes, sizes and densities were used as simulative solid waste, and silica sand was employed as fluidization medium. The pressure drop, flow pattern and minimum fluidization velocity (Umf) under different operating conditions were investigated by recording pressure differential signals and fluidization images. A correlation of Umf was also developed. The results showed that during the fluidization of irregular particles with the bed material of silica sand, the pressure drop curve measured with increasing fluidization gas flow rate was visibly fluctuant and always underestimated the Umf value; while the pressure drop curve measured with decreasing fluidization gas flow rate was smooth and adequate to determine the value of Umf. The Umf was found to be increased with increasing volume proportion and effective particle density, while the initial static bed height has no significant effect on the minimum fluidization velocity. By comparing the Umf values predicted by the developed correlation with the present experimental data and those from literature, it was found that the correlation was quite satisfactory on predicting the Umf value for the fluidization of irregular particles with the bed material of silica sand. The correlation was also found to be applicable to the prediction of Umf values of a solid waste fluidized bed with a single kind or multi-kinds of irregular particles.

Flow characteristics and stability of dense-phase pneumatic conveying of pulverized coal under high pressure

Conveying characteristics and flow stability are very important for design and control of conveying system under high pressure. The influences of operating parameters (fluidizing gas flow rate and supplementary gas flow rate) and material properties (coal category, particle size and moisture content) on conveying characteristics were investigated in an experimental test facility with the conveying pressure up to 4MPa. Wavelet transform and Shannon entropy analysis were applied to analyzing pressure drops through horizontal pipe in order to obtain stability criterion. Results indicated that with the increase in fluidizing gas flow rate, the mass flow rate of pulverized coal increased at first and then decreased while solid–gas ratio decreased all the way. Conveying phase diagrams and pressure drops through different test sections of pulverized coal under high pressure were obtained and analyzed. Conveying optimal moisture content and extreme moisture content were revealed for different coal categories. The influences of coal category and particle size on conveying characteristics were achieved. Through analyzing the relationship between Shannon entropy and conveying stability at different operating parameters and material properties, a new method for distinguishing conveying stability was established.

Minimum spouting velocity in a spout‐fluid bed with a draft tube

AbstractMinimum spouting velocity was measured in a 0.12 m cylindrical spout‐fluid bed with a draft tube. The effects of fluidizing gas flow rate, entrainment height, and spout nozzle diameter on minimum spouting velocity were discussed. A correlation on minimum spouting velocity has been proposed based on the present experimental data.