What is bubbling fluidization?
1.3 Bubbling fluidized-bed gasifier. This type of gasifier is characterized by the bubbling of bed material and solid fuel by flowing gas through it when the gas velocity is sufficiently high.
What is particulate fluidization?
Particulate fluidization is a condition when particles in a fluidized bed are individually suspended. When the fluidizing fluid is liquid and is characterized by a large and uniform expansion of the bed at high velocities, this is known as particulate fluidization.
What is bubbling fluidized bed combustion?
Fluidized bed combustion (FBC) is a combustion technology used to burn solid fuels. In its most basic form, fuel particles are suspended in a hot, bubbling fluidity bed of ash and other particulate materials (sand, limestone etc.) Since this allows coal plants to burn at cooler temperatures, less NOx is also emitted.
How is the temperature maintain in bubbling fluidized bed?
How is the temperature maintained in a bubbling fluidized bed? Explanation: A bubbling fluidized bed gasifier applies inlet from the bottom and moves the bed of fine-grained materials. The temperature is maintained by manipulating the ratio of biomass and gasification agent.
What are types of fluidization?
Based on different Geldart particle groups and gas velocities, several different fluidization regimes can be observed: fixed bed, homogeneous fluidization, bubbling fluidization, slugging fluidization, turbulent fluidization, and entrainment process.
What is the meaning of fluidization?
Fluidization is defined as a method to keep solid particles floating in an upward direction (Figure 5) in a flow of gas or liquid. In freezing, fluidization occurs when particles of a similar shape and size are subjected to an upward stream of low-temperature air.
What is aggregate fluidization?
aggregative fluidization (boiling fluidization) The type of fluidization that occurs when the fluid and solids have significantly different densities, as occurs in gas/solid systems and some liquid/solid systems.
What are the types of fluidized bed combustion?
There are two basic categories of fluidized-bed combustion, i.e., atmospheric fluidized bed combustion (AFBC) and pressurized fluidized bed combustion (PFBC). Each category is further comprised of bubbling fluidized bed combustion (BFBC) and circulating fluidized bed combustion (CFBC).
Why is fluidization used?
Fluidized beds are used as a technical process which has the ability to promote high levels of contact between gases and solids. Extremely high surface area contact between fluid and solid per unit bed volume. High relative velocities between the fluid and the dispersed solid phase.
When do particles become fluidized in fluidization theory?
Fluidization theory Particles become fluidized when an upward-flowing gas imposes a high enough drag force to overcome the down- ward force of gravity. The drag force is the frictional force imposed by the gas on the particle; the particle imposes an
What happens at the point of minimum fluidization?
The point at which this occurs depends on the particle size and density. Smaller or lighter particles tend to experience smooth fluidization before bubbles appear. Larger or denser particles tend to start bubbling at the point of minimum fluidization.
Which is the best description of fast fluidization?
At even higher gas velocities, all of the particles are entrained out of the bed. This type of fluidization is called fast fluidization. Further increases in the superficial gas velocity result in complete conveying of all of the particles.
How does fluidization affect the velocity of gas?
Thus, as a particle becomes more fluidized, it affects the local gas velocity around it due to these drag forces. This effect is minimal for spherical particles, but the influence of the drag force is more significant for irregularly shaped particles.