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

Gas distribution system for a two-zone fluidized bed reactor Abstract 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.

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

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

Kh, Sudan 2 Associated Professor, Department of Telecommunication Engineering, Faculty of Engineering, AL Neelain University, Kh, Sudan 3 Abstract : A two-phase model is proposed for describing the dynamics of a fluidized bed reactor used for polypropylene production. In the proposed model, the fluidized bed is divided into an emulsion and bubble phase where the flow of gas is considered to be plug flow through the bubbles and perfectly mixed through the emulsion phase. Similar previous models, consider the reaction in the emulsion phase only. In this work the contribution of reaction in the bubble phase is considered and its effect on the overall polypropylene production is investigated the kinetic model is combined with hydrodynamic model in order to develop a comprehensive model for gas-phase propylene copolymerization reactor. Simulation profiles of the proposed model were compared with those of well mixed model for the emulsion phase temperature. The simulated temperature profile showed a lower rate of change compared to the previously reported models due to lower polymerization rate. Model simulation showed that about 13% of the produced polymer comes from the bubble phase and this considerable amount of polymerization in the bubbles should not be neglected in any modeling attempt.
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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

Furthermore, the calculated steady state MWD has been com- 429 pared with the literature [19] and actual MWD data points for a 430 LLDPE (BP LL0209) and a HDPE (BP HD5218) grade in Fig. 5 for 431 comparison. The actual data have been produced using the GPC 432 data provided by the petrochemical complex. These two figures 433 are produced by calculating and plotting the derivative of cumula- 434 tive weight fraction against the logarithm of weight average 435 molecular weight, which is a typical GPC output. As can be seen, 436 aside from the slight differences, there is a very good agreement 437 between all sets of data for both cases of LLDPE and HDPE grades. 438 Although taking solids elutriation into account in the present 439 model leads to predicting the polymer properties such as MFI, 440 PDI and MWD accurately, its main advantages lie in calculating 441 the process parameters such as production rate and reactor tem- 442 perature more precisely. This is due to the improved dynamic mass 443 and energy balance equations which consider solids entrainment 444 and essentially improves the model to comply more with the real 445 world process data. In addition, this model is able to predict the 446 dynamic behavior of the fluidized bed reactor and can also be used 447 for control study and designing an efficient control system for this 448 highly nonlinear process. 449
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Modelling of a calcium looping fluidized bed reactor system for carbon dioxide removal from flue gas.

Modelling of a calcium looping fluidized bed reactor system for carbon dioxide removal from flue gas.

first models being the bubbling fluidised bed reactors. The carbonator models that have been suggested by researchers considered the carbonator as a circulating fluidized-bed, which has two compartments, the bottom dense zone and the lean zone. The majority of the models proposed in literature have concluded that the calcium particles that react in the fast regime influence carbonator efficiency. The percentage of the calcium particles that react in the fast regime is defined by the amount of fresh sorbent being introduced into the system and the solid circulation between the calciner and carbonator. It has been proposed in literature to design a model that considers the actual activity of the calcium particles in the system according to their carrying capacity, regardless of their preceding history of partial or full carbonation-calcination cycles. True results would be obtained about the carbonator and general plant performance. It is also important to measure the effect of sulphation and the amount of non-active calcium particles that react with sulphur dioxide in the calcium looping system.
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Different hydrodynamic model for gas phase propylene polymemation in a catalytic fluidized bed reactor

Different hydrodynamic model for gas phase propylene polymemation in a catalytic fluidized bed reactor

Tehran, Iran in the reactor as compared with the simple two-phase model at steady state conditions. Choi and Ray [2] presented a simple two-phase model in which the reactor consists of emulsion and bubble phases. They assumed that the polymerization reaction occurs only in the emulsion since the bubbles are solid-free. Hatzantonis et al. [3]

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Pure hydrogen from biogas: Intensified methane dry reforming in a two-zone fluidized bed reactor using permselective membranes

Pure hydrogen from biogas: Intensified methane dry reforming in a two-zone fluidized bed reactor using permselective membranes

Research®) used in this work has a total length of 15.2 cm, an external diameter of 0.32 cm, and a thickness of the Pd/Ag layer of 76 m. Both membranes are sealed at their lower end and joined by their upper end and brazed to a stainless steel stub connected to an external vacuum pump (2P-3 - Telstar). When the reactor is operated in a TZFBR+MB configuration, the pump provides a low pressure in the permeate side (c.a. 6 mbar). The stream coming from this side is also analyzed online by gas

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Incineration of Municipal Sewage Sludge in a Fluidized Bed Reactor

Incineration of Municipal Sewage Sludge in a Fluidized Bed Reactor

Figure 4. Concentrations of chosen organic compounds during combustion of: (a) fuel I; (b) fuel II (Index: r-av: average value in reburning area). acid concentration fluctuated at the detection limit. Dur- ing the two zone combustion of fuel I when the value of air excess coefficient reached a value of 1.0 methanol concentration was about 50 ppm (Figure 4(a)) and while the combustion of fuel II in a bed of lime—30 ppm (Figure 4(b)). Concentration of formaldehyde (regard- less of the type of bed and fuel) reached under these con- ditions a value of about 270 - 300 ppm. Calculations in- dicate that in the reburning zone content of C 1 - C 3 hy- drocarbons is not more than 20% of the amount of re- burning fuel dosed into the reactor, but their presence indicate a significant advancement of propane decompo- sition processes involving radicals favourable for NO x
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unit 3-fluidized bed reactor - design consideration

unit 3-fluidized bed reactor - design consideration

Conventional liquid–solid fluidization was studied intensively during the fifties. For pollutant treatment procedure the hydrodynamics of liquid-soild fluidization and liquid-solid-gas fluidization can bring the solution for design purpose. It has been considered that liquid–solid fluidization is a uniformly dispersed homogeneous fluidization, with or without external particle circulation and regardless of the fluidization regime. This assumption of homogeneous behavior for the liquid–solid fluidization systems considers the liquid–solid fluidization as an ideal system and forms the basis of Richardson and Zaki and Kwauk’s work [31].
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Catalytic Biomass Gasification Process in Fluidized bed Reactor

Catalytic Biomass Gasification Process in Fluidized bed Reactor

To perform attrition tests, a stainless steel bubbling fluidized bed reactor 40 mm ID and 1 m high has been used. A 0.6 m high stainless steel column for gas preheating and mixing was placed under the distributor. Two semi-cylindrical 2.2 kW electric furnaces were used for heating the fluidization column and the preheating section. A two-exit brass head was fitted to the top flange of the fluidization column. By operating this valve it was possible to convey flue gases alternately to two removable filters made of sintered brass. Elutriated fines were collected by means of the two- exit head by letting the flue gas flow alternately through sequences of filters (one was in use while the previous one was replaced) for definite periods of time. In order to prevent hydration of the collected material, each filter was readily put in a drier after being used, where it was cooled down before it was weighed. The difference between the weights of the filters before and after operation, divided by the time interval during which the filter was in operation, gave the average fines elutriation rate relative to that interval. The assumption underlying this procedure was that the residence time of elutriable fines in the reactor could be neglected and that elutriation rate could be assumed equal to the rate of fines generation by attrition at any time. Attrition tests have been carried out using N 2 as fluidizing gas at 800°C and at a superficial gas velocity of 10 cm·s -1 .
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Unsteady-State Modeling of the Fluidized Bed Polyethylene Reactor

Unsteady-State Modeling of the Fluidized Bed Polyethylene Reactor

A mathematical model is developed for describing the dynamic behavior of the gas phase ethylene polymerization reactor. The model is based on the dynamic two-phase concept of fluidization in which the bubbles may contain solid particles and the emulsion is capable of containing more gas than that of minimum fluidization. The fluidized bed reactor is divided into several serial sections consisting of bubble and emulsion phases. Flow of the gas is considered as plug flow through the bubbles and perfectly mixed through the emulsion phase. Polymerization reactions occur in both emulsion and bubble phases. Variation of the process variables as well as the polymer properties were studied as a function of operating time. The bed height was controlled by the product withdrawal rate with a PID controller. The results of the model were compared with the experimental data and a good agreement was observed between the model prediction and actual data. The simulation results indicate that a significant amount of polymer production (roughly 12%) takes place in the bubbles.
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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

Nowadays, hydrogen and methanol are attractive prospects because of lower emissions compared to the other energy sources and their special application in fuel cell technology, which are now widely regarded as key energy solutions for the 21st century. These two chemicals can also be utilized in transportation, distributed heat and power generation and energy storage systems. In this study, a novel double fluidized-bed two-membrane reactor (DFTMR) is proposed to produce ultrapure hydrogen and enhance methanol synthesis as environmentally friendly fuels, simultaneously. The fluidization concept is used in both sides to overcome drawbacks such as internal mass transfer limitations, pressure drop, radial gradients of concentration and temperature in thermally coupled membrane reactors. The DFTMR system is modeled based on the two-phase theory of fluidization and then its performance is compared with those of thermally coupled membrane reactor (TCMR) and conventional methanol reactor (CR) under the same operating conditions. The simulation results show 24.69% enhancement in hydrogen production in comparison with TCMR. Furthermore, 14.39% and 15.78% improvement in the methanol yield can be achieved compared with TCMR and CR, respectively.
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Simulation of Fischer-Tropsch Fluidized Bed Reactor for the Production of Methane from Synthesis Gas (Gas to Liquid Technology)

Simulation of Fischer-Tropsch Fluidized Bed Reactor for the Production of Methane from Synthesis Gas (Gas to Liquid Technology)

Figure 1: Two phase Fluidized bed reactor model (Kunii and Levenspiel, 1991) where r is the density of the gas phase, r ib , r ie are the emulsion and bubble phase densities, U O is the superficial velocity, U b , U e are the bubble and emulsion velocities, is the mass transfer coefficient between bubble and emulsion phase, is the minimum fluidization velocity.

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Effect of Local Bed Hydrodynamics on the Distribution of Liquid in a Fluidized Bed

Effect of Local Bed Hydrodynamics on the Distribution of Liquid in a Fluidized Bed

between 0.3 and 0.9 m/s. The temperature in the reactor is preferably maintained between 480 °C to 540 °C while the gauge pressure is between 0 to 3.5 bar. [3] In the fluid bed reactor, the feed is converted to hot hydrocarbon vapor, permanent gases and solid coke. The gas and vapors pass through cyclones where most of the entrained particles are removed. Then the vapors enter a scrubber section in which remaining particles are removed and heavy liquids are condensed. At the base of the reactor, coke particles flow through the stripping section and interstitial product vapors are removed by a stripping gas, e.g. steam. The coke particles flow down through a stand-pipe then up though a riser to the burner. A portion of the coke particles are burned with air to produce enough heat for the process. The remaining,
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Optimization of fluidized bed carbochlorination of zirconia in pilot scale reactor

Optimization of fluidized bed carbochlorination of zirconia in pilot scale reactor

EXPERIMENTAL SECTION To obtain the necessary experimental data, a pilot scale carbochlorination reactor was designed and manufactured which is shown in Fig. 1. The reactor consists of two electrodes to introduce electric current into a fluidized bed of conductive particles. In the case of chlorination reactions, the bed of carbon particles provides both the necessary reductant and the heating means. The reactor system is made of a hard graphite chlorination reactor, a bed resistance heating unit, two condensing unit, and auxiliary equipment for supplying and measuring the gases, feed, and power to the system. The graphite chlorination reactor tapered from a 6.35-cm diameter at the bottom to 11.43 -cm in diameter at the top and was 123.19-cm high. A 1.27-cm hole in the bottom of reactor was used as a feed and fluidizing gas inlet. In order to achieve more uniform temperature throughout the reactor, a layer of fine graphite powder was built around the reactor. The second electrode for the heating system was at the center of the reactor.
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Oxidation Kinetics of Aluminum Powders in a Gas Fluidized Bed Reactor in the Potential Application of Surge Arresting Materials

Oxidation Kinetics of Aluminum Powders in a Gas Fluidized Bed Reactor in the Potential Application of Surge Arresting Materials

Abstract In this technical paper, the oxidation mechanism and kinetics of aluminum powders are discussed in great details. The potential applications of spherical aluminum powders after oxidation to be part of the surging arresting mate- rials are discussed. Theoretical calculations of oxidation of spherical alumi- num powders in a typical gas fluidization bed are demonstrated. Computer software written by the author is used to carry out the basic calculations of important parameters of a gas fluidization bed at different temperatures. A mathematical model of the dynamic system in a gas fluidization bed is devel- oped and the analytical solution is obtained. The mathematical model can be used to estimate aluminum oxide thickness at a defined temperature. The mathematical model created in this study is evaluated and confirmed consis- tently with the experimental results on a gas fluidization bed. Detail technical discussion of the oxidation mechanism of aluminum is carried out. The ma- thematical deviations of the mathematical modeling have demonstrated in great details. This mathematical model developed in this study and validated with experimental results can bring a great value for the quantitative analysis of a gas fluidization bed in general from a theoretical point of view. It can be applied for the oxidation not only for aluminum spherical powders, but also for other spherical metal powders. The mathematical model developed can further enhance the applications of gas fluidization technology. In addition to the development of mathematical modeling of a gas fluidization bed reactor, the formation of oxide film through diffusion on both planar and spherical aluminum surfaces is analyzed through a thorough mathematical deviation using diffusion theory and Laplace transformation. The dominant defects and their impact to oxidation of aluminum are also discussed in detail. The well-controlled oxidation film on spherical metal powders such as aluminum and other metal spherical powders can potentially become an important part How to cite this paper: Shih, H. (2019)
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Agglomeration in Fluidized Bed Combustion System

Agglomeration in Fluidized Bed Combustion System

Key words: Agglomeration, Fluidised bed, Fouling, Sulphur capture I. I NTRODUCTION Fluidisation is the art of making granular solids to behave like fluid, fluidised bed technique used for gasification, combustion and incineration. All type of coal, coal residue, biomass, petroleum products and municipal solid waste are used as fuel in fluidised bed. Fuels with high ash content, low bulk density, poor flow characteristics and low ash melting point are utilised in fluidised bed. The bed material used as thermal flywheel to store heat energy, maintains bed temperature and restart of the system without external heating. Simple design, compact combustion chamber, good heat and mass transfer, high reaction rate of gas solid mixture, high combustion efficiency, easy temperature control makes the system attractive [1, 2]. Fluidised bed promotes good mixing of air and fuel, uniform heat distribution, low operating temperature and short system start-up time makes it economical and quick response to varying load; no pre- treatment of fuel required and low ash related problems.
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Computational Fluid Dynamics Simulation of Gas-Solid Flow during Steam Reforming of Glycerol in a Fluidized Bed Reactor

Computational Fluid Dynamics Simulation of Gas-Solid Flow during Steam Reforming of Glycerol in a Fluidized Bed Reactor

Abstract: A CFD simulation of gas-solid flow in a fluidised bed reactor was performed to investigate the steam reforming of glycerol using a three-step reaction scheme, motivated by the worldwide increase of crude glycerol produced by the transesterification of vegetable oil into biodiesel. The Eulerian–Eulerian two-fluid approach was adopted to simulate hydrodynamics of fluidisation, and chemical reactions were modelled by the laminar finite-rate model. The gas-solid system exhibited a more heterogeneous structure. Clusters were observed to fall and stack together along the wall, and the process of wall slug formation was very evident. This suggests the bed should be agitated to maintain satisfactory fluidising conditions. The results showed that the glycerol conversion increased with increasing reaction time and most of the gas products H 2 , CO 2 , CH 4 and CO were formed during the initial 2 s. The prediction of the gas -solid phase flows and mixing, glycerol conversion and products distribution will provide helpful data to design and operate a bench scale catalytic fluidised bed reactor.
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Hydrogen Gas Production from Gasification of Oil Palm Empty Fruit Bunch (EFB) in a Fluidized Bed Reactor

Hydrogen Gas Production from Gasification of Oil Palm Empty Fruit Bunch (EFB) in a Fluidized Bed Reactor

Data of proximate and ultimate analysis of EFB done by Mohammed, Salmiaton [30] was selected for this study since the hydrogen yield and other operation condition of this simulation will be compared with their experimental analysis result. 4.0 RESULT AND DISCUSSION The design basically consist of a few processes which are gasification reaction, by-product separation and gas cleaning process as illustrated in Figure 5. As feed material, EFB is nonconventional, therefore its element compositions are all need to be converted to element in RYIELD. The RYIELD block was used for the devolatilization of the feedstock and after passing through the drying and pyrolysis stage, EFBs were converted into different types of elements which are H 2 , CO, CO 2 , etc. After that, EFB (elements) moved down due to gravity and came in contact with air in the RGIBBS block in which balanced products under certain temperature and pressure can be determined based on the method of Gibbs free Energy Minimization. The produced gas contains some particles are then eliminated using the CYCLONE solid separator and finally hot syngas are cooled using heat exchanger aspen plus block. Table 5 shows the flow sheets of the EFB gasification system and detailed mass and energy analyses for the main streams involved which are EFB, FBRGAS, SYNGAS2, SYNGAS3, H2-GAS, OTHERGAS and H2 stream. FBRGAS is a stream that produce syngas after gasification including H 2 , CO, CO 2 , H 2 O, and CH 4 .
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Ethylene Dichloride Production by Oxychlorination in a Fluidized Bed Reactor with CFD Model

Ethylene Dichloride Production by Oxychlorination in a Fluidized Bed Reactor with CFD Model

The first part studied on many effects of the boundary condition because it can be a very versatile tool to improve the operating conditions in a real plant. The effects of difference parameters on the behavior of the system were investigated. The significant discovery is the effect of feed molar distribution. The operating points where ethylene reached the highest conversion with least excess of hydrochloric acid and oxygen was at a feed of ethylene mole fraction equal to 0.22. An outlet pressure in the range of 200 to 450 kPa boosts the ethylene conversion from 96.39 to 98.46%. The improvement of ethylene conversion by increase of pressure appeared to interfere with the overall operating pressure and the gas-solid flow behavior. The increase of cooling medium temperature from 300 to 420 K raises the ethylene conversion from 96.9 to 98.8% and gas outlet temperature from 422 to 565 K. Therefore, the improvement in ethylene conversion should be the adjustment of a high cooling medium temperature. Finally, the gas feed temperature has a minor effect on ethylene conversion. Although the parameter variation in the operation increased the ethylene conversion this also affects the system behavior such as the operating pressure, operating temperature, and the gas-solid flow behavior. Hence, the parameter adjustment should be considered under these limited parameter values.
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Mathematical Modelling of Biomass Gasification in a Circulating Fluidized Bed CFB Reactor

Mathematical Modelling of Biomass Gasification in a Circulating Fluidized Bed CFB Reactor

The pyrolysis model based on the approach proposed by Merrick and tested in this work can be suggested as promising basis for a more accurate modelling of the biomass thermal decomposition. It is capable to predict the formation of tar and hydrocarbons as components of the volatile matter, but still requires further improve- ments. To improve such procedure, the empirical corre- lations used to build the linear equations system should be re-defined and validated in accordance with the gas composition observed during the experiments of biomass pyrolysis, in the case of solid fuels with a volatile content typically around 80%, surely higher than coal [9].
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