Top PDF Gas distribution system for a two-zone fluidized bed reactor

Gas distribution system for a two zone fluidized bed reactor

Gas distribution system for a two-zone fluidized bed reactor

The present invention provides an improved method for constructing a gas distribution system which creates two distinct reaction zones within the same fluidized bed. The invention provides for the distribution of one type of gas at the bottom of the fluidized bed and a second type of gas at a higher level in the fluidized bed. The system is constructed of a plurality of modular units constructed entirely of refractory materials. The modules are fitted and linked together to form a grid, the size of which can be varied to accommodate different reactor sizes.
Show more

17 Read more

High density gas-solids circulating fluidized bed riser and downer reactors

High density gas-solids circulating fluidized bed riser and downer reactors

A large number of studies had examined the influence of entrance and exit geometry in CFB risers. Recent experimental results (Jin, 1988, Brereton and Grace, 1994, Gwyn, 1993, and Cheng et al., 1998) demonstrated that the geometry of the riser exit could greatly influence the performance of CFBs, by affecting pressure and solids holdup profiles, not only close to the roof, but also at a considerable distance down the column. There were two types of exit configurations categorized as abrupt exit and smooth exit. With an abrupt exit, a relatively high solids concentration and a low particle velocity were observed, while with a smooth exit, the restriction to the solids flow was much less, and the dense suspension zone disappears. Reviews by Lim et al. (1995) concluded that the exit design could affect the density profile over several meters in the upper region of a riser. Bai et al. (1992) compared the influence exerted by different exit and inlet structures of fast fluidized beds on the axial voidage distribution. They reported that with a restrictive exit design, the voidage profile had a C-shape, while the profile was S-shape when a very weakly restrictive entrance structure was employed.
Show more

296 Read more

Optimization of fluidized bed carbochlorination of zirconia in pilot scale reactor

Optimization of fluidized bed carbochlorination of zirconia in pilot scale reactor

The main objective of this work was to design and build a pilot-scale carbochlorination fluidized bed reactor with optimal operating conditions. The designed reactor consists of a novel middle layer structure which facilitates more uniform temperature in the reactor. Also an improved control system was provided for fine controlling of power input. Another objective of this work was to use a hydrodynamic two-phase model for simulation of the reactor. For authentication purposes, the experimental data were obtained from the pilot were used for modeling validation. Furthermore, the validated model was utilized to investigate and optimize the effects of initial zirconia particle size, inlet chlorine concentration, reactor temperature and superficial gas velocity time on reactor performance. Therefore, it is possible via the application of the obtained model to pinpoint the appropriate conditions for the reactor operation without any additional time consuming and expensive experiments.
Show more

12 Read more

Modeling the size distribution in a fluidized bed of nanopowder

Modeling the size distribution in a fluidized bed of nanopowder

The fluidized agglomerates are recorded while falling through a settling tube placed in the splash zone. As was demonstrated by Wang et al. [22], agglomerates present in the splash zone are representative of those found in the bed. Additionally, the gas velocity used for fluidization is large enough for the agglomerates to follow the gas flow by keeping their Stokes number bellow one. The settling tube is a black box with an opening at the top to catch falling agglomerates, and two openings on the side for agglomerate recording and tube cleaning purposes (Fig.1). A rigid borescope (Olympus R040-021-000-60 S5) and high speed camera (Phantom v9.1) system are used for the recordings, enabling a visible size range from 30 µm to 4 mm [29].
Show more

21 Read more

Incineration of Municipal Sewage Sludge in a Fluidized Bed Reactor

Incineration of Municipal Sewage Sludge in a Fluidized Bed Reactor

2.2. Equipment and Procedure of Researches Thermal utilization of fuel I and fuel II has been con- ducted in laboratory scale ABFB reactor (capacity of about 5 kW, Figure 1). Fluidized bed reactor was made of a quartz tube, which outer diameter is 96 mm, wall thickness is 2 mm and height is 500 mm, set on a perfo- rated steel plate with a thickness of 1 mm, which was a distributor of air and gaseous fuels. The temperature reg- ulation system was composed of moveable radiation shield, limiting the heat losses to the environment and of the cold air blower (Figure 1). To measure the tempera- ture in the fluidized bed two fixed thermocouples were used mounted at a height of 20 and 50 mm above the distributor. The temperature in the second combustion zone has been measured by 8 thermocouples mounted in the axis of the reactor one above another (Figure 1): in Fuel II was composed of municipal sewage sludge
Show more

10 Read more

Simulation of Olive Kernel Gasification in a Bubbling Fluidized Bed Pilot Scale Reactor

Simulation of Olive Kernel Gasification in a Bubbling Fluidized Bed Pilot Scale Reactor

Haggerty and Pulsifer [13] used the reaction model together with three different reactor models (a) plug-flow, (b) complete-mixing and (c) bubble-assemblage, where the bubble-assemblage model represents a valid alterna- tive when modelling fluidized-bed gasifiers. Marias et al. [14] developed a mathematical model for the fluidized- bed incineration process using the waste composed of wood, cardboard and polyvinyl chloride. Aarsen’s model treated an isothermal fluidized bed as two separate zones, the oxidation zone at the bottom and the gasification zone at the top [15]. Fuel pyrolysis took place at such a fast rate that only pyrolysis yields, which were assumed to vary with bed temperature, were needed. Mukosei et al. [16] examined the problem of the mathematical simula- tion of heterogeneous processes in a fluidized-bed reactor. These works and other more recent ones such as the work by He and Rudolph [17] proposed a new approach to the modelling of gross gas-solids flow through the riser in a circulating fluidized-bed system. This approach differs from the previous ones, which are found to be the- oretically incorrect based on a fundamental analysis of the riser process hydrodynamics.
Show more

15 Read more

Enhancement of Hydrogen and Methanol Production using a Double Fluidized-bed Two Membranes Reactor

Enhancement of Hydrogen and Methanol Production using a Double Fluidized-bed Two Membranes Reactor

configurations. As it can be seen in Fig. 3 (a), controlling the temperature of exothermic side in the DFTMR is easier due to lower hot spot. There is not a sudden increase of temperature for this system at reactor entrance like CR. Furthermore, in the second region, the continually reduced temperature in this bed provides increasing thermodynamic equilibrium potential. Thus, the most favorable exothermic temperature profile seems to belongs to DFTMR system owing to simultaneous heat transfer with permeation side in the inner tube and reacting gas in the endothermic side and also using a fluidization concept.
Show more

18 Read more

Use of a Baffle to Enhance Distribution of a Liquid Sprayed into a Gas-Solid Fluidized Bed

Use of a Baffle to Enhance Distribution of a Liquid Sprayed into a Gas-Solid Fluidized Bed

operation and maximize the yield of valuable products [1][2]. Agglomeration results in incomplete reaction of the feed in the reactor zone, which leads to lower yield and fouling of the stripper zone. Ariyapadi et al. [3] took X-ray movies of radio-opaque liquid sprayed into a gas-solid fluidized bed and discovered that wet agglomerates were immediately formed at the tip of the spray jet cavity and then mixed through the bed by gas bubbles. Bruhns and Werther [4] studied liquid injection into a fluidized bed with thermocouples and inferred from their results that agglomeration occurs near the injection nozzle outlet. It is vital to investigate new methods to curtail agglomerate formation when liquid is sprayed into a fluidized bed. One such new finding would be to place a baffle [5] that could positively influence the bed hydrodynamics and mixing characteristics in the vicinity of the injection nozzles (Figure 3.1). Limited studies has been reported in the literature on the effect of baffles in bubbling gas-solid fluidized beds. Sanchez Careaga (2013) [6] used radioactive particle tracking to study the effect of ring baffles on the motion of wet agglomerates: his results suggest that ring baffles affect bed hydrodynamics by redirecting gas bubbles above the baffle region as a results of gulf streaming [7][8][9] where a low pressure region created by baffles can create gas expansion and drag large bubbles above the baffle. Mohagheghi et al. [10][11][12] have found that the interaction of gas bubbles with the spray jet cavity can greatly affect the distribution of the sprayed liquid.
Show more

193 Read more

Environment Friendly Continuous Flow Gas Generation by Fluidized Bed Rice

Environment Friendly Continuous Flow Gas Generation by Fluidized Bed Rice

A data acquisition (DAQ) system is used for online recording and processing of the data, like temperature and pressure, collected from the gasifier. This system consists of temperature probes, pressure transducers, power supply, microcontroller, personal computer, and signal conditioning extinctions for instrumentation (SCXI). The National Instruments SCXI is a multi- channel signal conditioning and control system for using with personal computers. It is comprised of a chassis that can house a variety of modules for any I/O needs. The SCXI system is programmed with Lab VIEW (Laboratory Virtual Instrument Engineering Workbench), a National Instruments applications software package. A library of functions included in Lab VIEW is used to develop a model for data acquisition, instrument control, data analysis, data presentation and data storage. It collects inlet, outlet, and reactor zone temp., flow rate etc.
Show more

8 Read more

Dynamic Modeling for Gas Phase Propylene Copolymerization in a Fluidized Bed Reactor

Dynamic Modeling for Gas Phase Propylene Copolymerization in a Fluidized Bed Reactor

A fluidized bed reactor model for polypropylene production using the dynamic two-phase concept of fluidization combined with proper kinetic model is presented in this study to provide a better understanding of the reactor performance and shown that about 13% of the polymer is produced in the bubble phase which is an appreciable amount that needs to be considered in all future models of the system.

5 Read more

Dynamic modeling and Molecular Weight Distribution of ethylene copolymerization in an industrial gas phase Fluidized Bed Reactor

Dynamic modeling and Molecular Weight Distribution of ethylene copolymerization in an industrial gas phase Fluidized Bed Reactor

153 The modeling approach depends on whether we discuss 154 homopolymerization or copolymerization. In homopolymerization, 155 only one monomer is involved in the production of the polymer, 156 while in copolymerization reaction, there are two types of mono- 157 mer forming the polymer. In the current study, the kinetic model 158 developed by De Carvalho et al. [23] and McAuley et al. [24] was 159 employed to produce a comprehensive mechanism which 160 describes the kinetics of copolymerization of ethylene and 1- 161 butene catalyzed by two sites of the ZN catalyst. Table 1 lists 162 the reactions, comprising formation, initiation, propagation, trans- 163 fer and deactivation of the active sites. To solve the equations, 164 method of moments was used. These related moments equations 165 are listed in Table 2. The index i in the tables refers to the type 166 of monomer and index j refers to the type of the active site. Table 3 167 gives the rate constants of each reaction for both site types that 168 were used in this work and mentions their sources in the literature. 169 If we assume that monomers are primarily consumed over the 170 propagation reactions, we can obtain the equation for consumption 171 rate of each component. Eq. (1) shows this mathematical state- 172 ment after solving the moment equations [24]:
Show more

13 Read more

Modeling of heat exchangement in fluidized 
		bed with mechanical liquid distribution

Modeling of heat exchangement in fluidized bed with mechanical liquid distribution

I - zone of downward motion of a granular material, due to the asymmetric introduction of the coolant (the liquor), the transfer of the granular material occurs due to inertial removal from zone II and III in the upper part of zone I. The layer thickness in this zone is practically constant εI = ε0 = 0.4 the maximum height increases to (1.7 ÷ 2) H0, and the motion of the gas coolant in this zone exclusively in the filtration mode, the dynamics of porosity change is shown in Figure-1b.

8 Read more

Effect of Spray Jet Interactions on the Liquid Distribution in a Fluidized Bed

Effect of Spray Jet Interactions on the Liquid Distribution in a Fluidized Bed

In the present work, the effects of interacting spray jets on the liquid distribution in a fluidized bed were determined. This was accomplished by studying the effect of spray nozzle penetration on the liquid content of agglomerates produced. The main objective of this study was to determine the effect of staggering spray nozzles on the amount of liquid remaining in agglomerates in an industrial Fluid Coker. This was achieved by the use of a simplified model developed by Sanchez (2013) to determine the liquid content in agglomerates produced in an industrial Fluid Coker, based on initial values determined in a smaller scale fluidized bed. To obtain the initial liquid content in agglomerates produced in a fluidized bed, a binder solution of gum arabic dissolved in water was injected into a fluidized bed of silica sand particles so that actual agglomerates could be produced. This process was time consuming and labour intensive, so a preliminary screening method was applied to quickly select the most promising distance between vertically separated spray nozzles, by estimating the effectiveness of the liquid distribution. The conductance method that was utilized for preliminary screening was that of Section 2.1.1.1. The most promising results from this conductance method were then validated using the gum arabic solution.
Show more

141 Read more

Hydrodynamics in the Gas-Driven Inverse Liquid-Solid Fluidized Bed

Hydrodynamics in the Gas-Driven Inverse Liquid-Solid Fluidized Bed

Figure 3.2 shows a sketch of the gas-driven inverse liquid-solid fluidized bed (GDFB) and its cross-sectional view. The top of the column is open to the air and the inner diameter (ID) of the column is 12.5 cm. The column is divided into a riser and a downer by a baffle with a length of 270 cm and a width of 10 cm. The riser refers to the vertical section having a smaller cross-sectional area and the downer is the one with a larger area. As shown in the cross section of the column, end points of the ID are point A and point C, while the baffle crosses the ID perpendicularly at point B. The length of line segment BC is 4 times that of line segment AB. Thus, the area of the downer is about one-sixth of the area of the downer. The purpose of designing these two different areas is to achieve fluidization with a relatively low energy cost. For a given gas flowrate, a smaller area of the riser results in a higher superficial gas velocity (𝑈 𝐺 ) and more liquid can be entrained by a smaller gas amount. Nevertheless, the riser cannot be too small that the total liquid amount constraint the liquid flow entering the downer. Therefore, in this preliminary design, the areas of the downer and riser were selected to have a six times difference. The liquid and gas in this research are tap water and air, respectively. Water is pumped into the column from a tank through a liquid inlet valve at the bottom of the GDFB. Meanwhile, an outlet valve allows water to be discharged back to the tank. Air is
Show more

83 Read more

Reactor Performances and Hydrodynamics of Various Gas-Solids Fluidized Beds

Reactor Performances and Hydrodynamics of Various Gas-Solids Fluidized Beds

A literature review on earlier experimental studies of fluidized-bed reactor performance is written in Chapter 2, revealing the following issues all of which are addressed in this study: most previous reactor performance studies have been done for BFBs and low density CFB risers, while TFBs, HDCFBs and downers have received very limited attention. Moreover, almost all of them were conducted only in each individual type of fluidized bed with different reactor dimensions and catalyst particles. As a consequence, the superior and inferior features of the various fluidized beds are difficult to be identified. Therefore, a systematic study covering the complete spectrum of commonly used fluidized beds under industrial operating conditions is very necessary. For the first time, herewith, our group has investigated the reactor performances of a BFB, a TFB, a CTFB, a CFB riser and a dower in a multifunctional fluidized-bed system using the same catalyst particles, the same reaction and the same reactor diameter for the sake of reliability and convenience of comparisons. By doing so, the distinctive characteristics of each bed can be identified, providing solid scientific basis for selecting suitable fluidized-bed reactors in industries. The BFB, TFB and CTFB are studied in this work, while the work of the CFB riser and downer has been done by Wang (Wang 2013) including high density/flux flow conditions. On the other hand, more efforts in research of reactor performance are required. For BFBs, although the reactor performance has received extensive studies since sixty years ago (Frye, Lake et al. 1958), the reports of complete spatial reactant conversion distributions, especially radial distributions, are insufficient (the references are listed in Table 2.2). For TFBs, only a few experimental studies of the reactor performance have been done, and no conversion mapping is available, even though they have much more commercial applications than BFBs. Furthermore, as a newly invented fluidized bed, the reactor performance study of CTFBs has not yet been reported.
Show more

252 Read more

Bubble-Induced Inverse Gas-Liquid-Solid Fluidized Bed

Bubble-Induced Inverse Gas-Liquid-Solid Fluidized Bed

Three different particles are employed to investigate the effect of water level on bed expansion ratio, including 904kg/m 3 , 3.5mm; 930kg/m 3 , 3.5mm and 950kg/m 3 , 4.6mm. The variations of bed expansion ratio as a function of superficial gas velocity for three water levels with three different particles are shown in Fig 5.3. It is observed from the figure that the bed remains as fixed until a certain gas flow rate, which is termed as the initial fluidization velocity. Thus, with further increasing the gas flow rate, bed expansion increases as more and more particles begin to fluidize. After some of the particles reach the bottom, this gas flow rate corresponding to the gas velocity is referred as the full expansion velocity. When the gas flow rate is higher than the full expansion velocity, as the limit of the total column height, the bed expansion ratio remains constant. The particles have the same trends as the trend in Fig 5.2.
Show more

127 Read more

Neutronic assessment on the use of advanced coated particles in a 
		fluidized bed nuclear reactor

Neutronic assessment on the use of advanced coated particles in a fluidized bed nuclear reactor

Neutronic calculations have been performed to a fluidized bed nuclear reactor that uses advanced coated particles to improve its endurance against irradiation and high temperature. The calculation is intended to determine whether reactor characteristics have been significantly compromised. The characteristic of the reactor is assessed by investigating the change in criticality from packed bed condition to a full expansion of the particle bed. The particle used in this calculation was based on the standard TRISO fuel particle as being used in the HTR-10 reactor, and the use of advanced fuel particle was performed by replacing the SiC layer by a ZrC layer. A packed bed of 50 cm high was used in this research with an additional 20 ppm of boron in the side reflector. At packed condition, replacing SiC by ZrC in TRISO particles significantly decreases the criticality with a range of -336 ± 138 pcm to -2809 ± 99 pcm. Calculation on expanded bed shows similar behaviors, in which case the decrease in reactivity spans from -269 ± 101 pcm to -1286 ± 121 pcm. The use of standard TRISO particles and advanced coated particles might create positive reactivity coefficients for particular height of expanded beds.
Show more

9 Read more

Mechanical Agitation Of Bed In A Motor Driven Two-Phase Fluidized Bed Particle Seeder

Mechanical Agitation Of Bed In A Motor Driven Two-Phase Fluidized Bed Particle Seeder

Fig. 6. Contour at 5:000s, showing a 100% bed rise gas hold up and dispersion delineated. Higher gas hold–up is usually a necessity for particle entrainment into the flow, since sufficient time is required for momentum transfer between the phases. [7] The bed rise is a prerequisite for determining experimental data as it decides the position of the elements of the agitation mechanism. Details on this are discussed in the next section. Also, it imposes a constraint to the speed of rotation of the blades. As seen earlier, the bed rise is solely due to the incoming fluid flow in the numerical model analyzed here.
Show more

5 Read more

Thermal decomposition of selected chlorinated hydrocarbons during gas combustion in fluidized bed

Thermal decomposition of selected chlorinated hydrocarbons during gas combustion in fluidized bed

Liquefied petroleum gas (LPG) was used as hydrocarbon fuel supporting combustion process in all experiments. Dichloromethane (DCM) and chlorobenzene (MCB) - both technical grade - were chosen as chlorinated hydro- carbons. All experiments were done in lab stand, illu- strated in Figure 1. The main element of it was a reactor built from a 500 mm transparent quartz tube (Figure 1, part 4, 96 mm internal diameter) resting on a 1 mm thick perforated plate Figure 1, part 8) and plenum chamber (Figure 1, part 9). The bed material was quartz sand (300 g, particle size 0.3 to 0.385 mm) with static height of 29 mm. Sand was fluidizing by a LPG and air heated to 80°C and mixed in plenum chamber. The air excess was 1.20 (±0.02). Both DCM and MCB were injected to the evaporator and then to the fluidizing air. The combustion process was initiated by a pilot flame (Figure 1, part 10) located in the freeboard. The bed temperature was regulated by a movable cylindrical
Show more

11 Read more

Approximate analytical solution of non linear  reaction diffusion equation in fluidized bed biofilm reactor

Approximate analytical solution of non linear reaction diffusion equation in fluidized bed biofilm reactor

The fluidized bed reactor (FBB) is the reactor which carries on the mass transfer or heat transfer operation using the fluidization concept. At first it was mainly used in the chemical synthesis and the petrochemistry industry. Because this kind of reactor displayed in many aspects its unique superiority, its application scope was enlarged gradually to metal smelting, air purification and many other fields. Since 1970’s, people have successfully ap- plied the fluidization technology to the wastewater bio- chemical process field. An FBB is capable of achieving treatment in low retention time because of the high bio- mass concentrations that can be achieved. A bioreactor has been successfully applied to an aerobic biological treatment of industrial and domestic wastewaters. An FBB offers distinct mechanical advantages, which allow small and high surface area media to be used for biomass growth [9-12].
Show more

9 Read more

Show all 10000 documents...

Related subjects