What is entrainment in fluidized bed?
Entrainment is the carryover of particles from the fluidized bed. In the simplest sense, when the gas velocity exceeds the terminal velocity of a particle, one would expect the particle to be removed from the bed. This is indeed the case.
At what velocity entrainment of particles in the fluidized bed takes place?
3. At what velocity entrainment of particles in the fluidized bed takes place? Explanation: At terminal velocity entrainment starts, when velocity is more than terminal velocity complete entrainment takes place.
What is principle of fluidized bed reactor?
In this type of reactor, a fluid (gas or liquid) is passed through a solid granular material (usually a catalyst) at high enough speeds to suspend the solid and cause it to behave as though it were a fluid. This process, known as fluidization, imparts many important advantages to an FBR.
What is the purpose of a fluidized bed reactor?
Fluidized bed reactors are widely used in material processing industries for processes that require very good heat and mass transfer between particles and a gas. The energy provided to the fluidized bed typically comes from the warm gas that fluidizes the bed as well.
What is entrainment in chemical engineering?
In engineering, entrainment is the entrapment of one substance by another substance. For example: The entrapment of liquid droplets or solid particulates in a flowing gas, as with smoke. The entrapment of gas bubbles or solid particulates in a flowing liquid, as with aeration.
What is bed velocity?
Bed velocity represents a weighted average of backscatter from moving bed load particles and spectral reflections from the immobile bed.
What is terminal velocity in fluidized bed?
A particle in a bed has a different field of reference. Instead of a body falling through a stagnant fluid, in a fluidized bed, the fluid is moving the body. A particle’s terminal velocity is the lowest gas velocity that causes particles to start moving with the gas.
What is anaerobic fluidized bed reactor?
Conceptual outline of the anaerobic fluidized bed process In a fluidized bed reactor, fine carrier particles are used for the microbial film development. These particles with entrapped biofilm are fluidized by high upflow fluid velocities generated by a combination of the influent and recirculated effluents.
What is the difference between packed bed reactor and fluidized bed reactor?
Excellent mixing of reactants in the fluidised bed helps to minimise temperature variations and renders this system attractive for carrying out gas–solid reactions. The fluidised bed reactors show better conversion of reactants in comparison with packed beds when solid reactants are used in the form of small pellets.
What is the most important thing one should remember while working with fluidized bed reactor?
Q9: What is the most important thing one should remember while working with fluidized bed reactor? Explanation: For an efficient operation of fluidized beds, gas is sparged to create a suitable and optimised gas-liquid-solid fluid bed.
What are the benefits of a fluidized bed reactor?
General Information Fluidized bed reactors are heterogeneous catalytic reactors in which the mass of catalyst is fluidized. This allows for extensive mixing in all directions. A result of the mixing is excellent temperature stability and increased mass-transfer and reaction rates.
How are fluidized bed reactors used in pyrolysis?
Fluidized bed reactors allow for the efficient transfer of heat to biomass particles, although a prerequisite is that the biomass particles should be fairly small (2–3 mm). Both bubbling fluidized beds and entrained, circulating fluidized beds (CFBs) may be employed for biomass fast pyrolysis.
What happens when a reactant expands in a fluidized reactor?
If it is a liquid the bed expands uniformly with increased upward flow of the reactant. This is called homogenous fluidization. If the reactant is a gas the bed will be non-uniform because the gas forms bubbles in the bed, resulting in aggregative fluidization.
How is the heating of a fluidized bed controlled?
The design of fluidized beds is well understood; however, the scale-up of fluidized bed processes can be limited by overall heat transfer. The vapor residence time is controlled by adjusting the fluidization gas flow rates; however, in bubbling fluidized beds, the undesired entrainment of biomass particles can occur at high gas velocities.