1.For a given bulk solid
how can the particle size distribution be determined?
2. What are the
different characteristics that can affect the flow of bulk solids and how?
3. What do you
understand by Wet bulb Globe temperature?
4. In case of welded
vessels why is stress relieving in the form of post-weld treatment necessary?
5. What significance
the angle of repose holds in the chemical industry, Explain?
6. What are the design
considerations for a piping system for the transfer of slurries?
For a given bulk solid how can the particle size distribution be
In order to determine the particle size distribution the simplest method is to
make use of a sieve stack. In this method a stack is created of with different
mesh sizes at each stack level. The structure is such that the biggest mesh
size is at the top and the smallest at the bottom. Once this setup is created
the before beginning the weight and other values of the solid is noted down.
Once this is done the solid is placed at the topmost cylinder and the entire
setup is exposed to a combination of vertical and horizontal movements. This
will make the solid pass through different mesh sizes in the process separating
the different particles according to their sizes. There are other more advanced
methods of determining the particle size distribution as well such as video
imaging and laser diffraction as well.
What are the different characteristics that can affect the flow of
bulk solids and how?
The main characteristics that can affect the flow of bulk solids are as follows:
> Moisture Content: when the moisture content is high the bulk solids become
sticky in nature. This moisture can sometimes be absorbed from the atmosphere
by some solids.
> Temperature: The flow of the bulk solids can be sometimes affected by the
temperature and also the period for which it is exposed to a particular
> Particle size: More cohesive particles are generally found in bulk solids
that are finer. Round particles are handled easily in comparison to odd,
> Time at rest: Many times the flow of certain bulk solids is affected by
the time for which it has been kept stagnant or at rest. The more it is kept at
rest the more slow the bulk solid flows.
What do you understand by Wet bulb Globe temperature?
The wet bulb globe temperature index is used to measure the sultriness of the
environment. The sultriness is calculated on the basis of the humidity affects,
the air speed and temperature and also the sun`s radiant heating factor. The
sultriness in some cases could be fatal and hence it is very important to keep
this under consideration. The wet bulb globe temperature index number was
developed in the 1950`s and is now accepted as an industry standard. It is
comprised of three temperature readings:
> Wet bulb temperature
> Ordinary dry bulb temperature
> Black bulb globe temperature
In case of welded vessels why is stress relieving in the form of
post-weld treatment necessary?
When a metal is welded together the point at which the two surfaces are joined
are subjected to very high temperatures. During this time period the metals can
go through a lot of random metallurgical processes. This causes the metal to be
harder and brittle. This depends on the amount of carbon content. In order to
relieve the metal of these properties heat treatment is done on the affected
areas. By doing so the affected areas ductility increases. In this process the
heat is maintained in the affected metal according to the thickness of the
metal. The temperature of the heat is calculated from the P number which is
unique for a particular composition.
What significance the angle of repose holds in the chemical industry,
The angle of repose is a property of particulate solids. A conical pile is
formed when a bulk solid is poured onto a flat surface. The angle formed
between the flat surface and the pile edge is called the angle of repose. The
angle of repose depends on the following factors:
> Density of the material
> Surface area
> Coefficient of friction of the material
A material having a low angle of repose would always create float piles as
compared to materials with a high angle of repose. This is used in the
designing of equipments which are used for particulate solids. In addition to
that this angle can be used to calculate the size of the conveyor belt that is
used to transfer the materials.
What are the design considerations for a piping system for the
transfer of slurries?
The following points must be considered for designing a piping system to carry
> The design of the piping system should be able to self drain.
> At the sections of the pipe where self draining is not possible provision
to install manual draining must be installed.
> At certain points where the chances of plugging are high, rod-out or
blow-out connections must be provided to clear the lines.
> In order to make flushing possible clean-out connections should be
installed on either side of the main valves.
> For easy access all the manifolds should have flanged connections.
> T-connections are a must for access flanges.