How does a fluidised bed work?
Typically, pressurized gas or liquid enters the fluidised bed vessel through numerous holes via a plate known as a distributor plate, located at the bottom of the fluidised bed. The fluid flows upward through the bed, causing the solid particles to be suspended.
What does bed expansion mean?
Bed expansion is defined as the increase in the volume of a bed of ion exchange or filter media during upflow operations, such as during backwashing. It is caused by lifting and separation of the media. Usually, bed expansion is expressed as the percent of increase in bed depth.
How do you calculate bed expansion?
Bed expansion is defined by the height of the expanded bed divided by the height of the settled bed (Fig. 13.3). Each type of adsorbent has known expansion properties (e.g., at a liquid velocity of 400 cm/h the bed expansion is two).
What is one of the reason for poor fluidization beds in terms of pressure drop?
9. What is one of the reason for poor fluidization beds in terms of pressure drop? Explanation: Slug formation leads to irregular distribution of pressure drop in the bed.
How do you make sand act like a liquid?
You can make a fluidized bed by blowing air through the bottom of a container of sand. Doing so increases the space between the sand particles, allowing them to move among each other more freely. By reducing internal friction in the sand, the grains are free to swim around as particles in a liquid do.
How is filter bed expansion measured?
2) To record the resting bed measurement, measure the top of the filter bed at rest (normal operation, before backwashing). Lower the expansion tool into the filter until the bottom of the disk touches the media surface. From a fixed location, record the reading, or slide an O-ring to mark the measurement.
What is the most important factor to be considered for designing a fluidized bed reactor?
In designing a fluidized bed system, particle size plays a major role because it is one of the major factors in fluidization characteristics apart from gas velocity.
What is minimum fluidization velocity in fluidized bed?
Minimum fluidization velocity. The minimum fluidization velocity can be calculated by equating the pressure–drop across the fixed packed–bed, calculated from Ergun’s equation to that from the expression for fluidized bed under particulate (smooth) conditions.
What is aggregative 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.
Is quicksand a fluidized bed?
Quicksand is caused when a bed of sand particles have a source of pressurized water rise from underneath until the water is saturated with sand and agitated, making it unable to support weight. This air causes the material to fluidize and behave like a liquid, much like in a bed of quicksand.
When does fluidization occur in a fluidized bed?
Fast Fluidized Bed The fast fluidization occurs as a result of continuing increasing in operating velocity beyond that required at turbulent fluidization, a critical velocity, commonly called the transport velocity (Utr), will be reached where a significant particle entrainment occurs.
Why is pressure important in fluidised bed combustion?
The effect of pressure on the behaviour of the bed is important because many industrial processes, including fluidised bed combustion which is discussed in Section 6.8.4 ., are carried out at elevated pressures.
What happens at the minimum fluidization velocity, UMF?
In a gas–solid fluidized bed, it has long been understood that fixed bed flow transforms to fluidized bed flow at the minimum fluidization velocity, Umf. For fine particle systems, bubbles appear at the minimum bubbling velocity, Umb, while slugs start to form at the minimum slugging velocity, Ums.
Can a fluidized bed maintain an iso-thermal profile?
Even for the most extreme exothermic reactions, a fluidized bed can maintain an iso- thermal profile within a few degrees. The acrylonitrile process, for example, capitalizes on this benefit.