310204d Solids And Liquids Flashcards
What type of product consistency does grinding produce?
A fine powder.
What type of crushing action is used with a Bradford Breaker?
Impact gravity crushing.
Why is water often added to the charge feeding a ball mill?
The water cools the mill and helps to convey the finer crushed material along to the discharge point.
Explain the purpose for adding flocking agents to a flocculation process
The purpose of most flocking agents is to neutralize negative charges on the particles to prevent them from repelling each other
Define granulation and explain how the process works
Granulation is the formation of smaller particles into larger masses in which the original particles can still be identified.
Granulation occurs as the rollers of a granulator press the particles together with rollers such as in the formation of fertilizer
True or False
The prilling process involves particles that are dissolved or dispersed in a liquid phase, or liquefied by heat, that are sprayed downwards from the top of a tall tower
True
A screening system can sort into how many grades
The screening system sorts into a number of grades where the number of grades is equal to the number of screens plus 1
What are 2 conditions that can cause a screen to become blinded?
- Particles that are close to the hole size of the screen
- Material that is wet
True or false
When using a trommel screen, the finer material exits the end of the screen.
False
With a trommel design, the finer material exits first, then the intermediate material and finally the course material exits the discharge and last
What type of separator uses centrifugal force to remove solids from a gas stream and has no moving parts?
A cyclone separator
What accumulates on the inside surface of the bowl of a scroll centrifuge?
Solids or heavy liquids
Which cleaning method does not require the filter to be opened for cleaning?
The backwashing filtration method
True or false
When using a filter press for filtering, increasing the number of filter cells increases the pressure drop
False
Increasing the number of filter cells allows the same flow rate to be handled at a lower pressure drop.
Name the piece of equipment that removes the dust particles from the electrode plate in an electrostatic precipitator
The rapper
What does a good static mixer design accomplish?
A well-designed static mixer can create maximum turbulence with minimal pressure drop
What flow direction is created with the use of a radial impeller?
Flow is perpendicular to the direction of the shaft.
What flow direction is created with the use of an axial impeller?
Flow is parallel to the direction of the shaft
What kind of mixtures would a double spiral impeller be used for?
The double spiral impeller is used for very viscous mixes
Define ‘crushing by attrition’
Crushing by attrition is a rubbing or grinding action
Define flocculation
Flocculation is a chemical process that removes colloidal and suspended solids (colloidal solids, also known as non-settleable solids, do not dissolve in water) from water
What are 3 examples of colloidal solids?
- Bacteria
- Fine clays
- Silts
Define suspended solids
Suspended solids, also known as settleable solids, settle out of water over time although this process can be awfully slow.
What are two examples of suspended solids
- Sand
- Heavy silts
Do most colloidal and suspended solids in water, have a negative or positive charge?
Most colloidal and suspended solids in water have a negative charge, so they tend to repel each other
What are Flocking agents?
Flocking agents, also called clarifying agents, neutralize negative charges on the particles to prevent them from repelling each other.
These agents have a positive charge, which attracts them to the negative particles in the water.
The combination of positive and negative charges results in a neutral or lack of charge. As a result, the particles no longer repel each other.
Define Agglomeration
Agglomeration is the process where smaller particles are compacted and glued together by the addition of a binder, such as water or oil
For example, flour agglomerates into dough, coal dust agglomerates into pellets for easier firing or transport, or the agglomeration of iron ore dust for shipping
Define extrusion.
Extrusion is when fine particles melt to first form a liquid and then pellets
The liquid in the extruder is forced at very high pressure through the orifices of an extrusion nozzle
The extruded filaments are then chopped with a rotating blade into pellets as they cool. The pellets are easier to handle and transport.
What are the 2 classifications for separators?
- Two-phase separators
- Three-phase separators
What is the difference between a two-phase separator and a three-phase separator?
A two-phase separator has a liquid outlet and a gas outlet
A three-phase separator has a gas outlet, an oil outlet, and a water outlet.
Describe the basic operation of a two-phase separator
- Gas enters the separator through the inlet
- The inlet diverter changes the direction of flow, liquid momentum is absorbed, causing the initial separation of liquid and gas
- In the gravity settling section, the larger liquid drops fall to the liquid collection section
- Smaller liquid drops remain with with the gas and pass through the mist extractor
- The mistis extractor uses coalescing elements to remove the small droplets of liquid. The gas must take numerous direction changes, which causes the droplets to impinge and collect on the coalescing elements where they fall to the liquid collection section
- The liquid leaves the vessel through the level control valve.
- The level controller senses changes in liquid level and controls the valve accordingly.
Describe the basic operation of a three-phase separator.
- Gas enters through the inlet
- The inlet diverter changes the direction of flow, liquid momentum is absorbed, causing the initial separation of liquid and gas
- In the gravity saddling section, the larger liquid drops fall to the liquid collection section
- Smaller liquid drops remain with the gas and pass through the mist extractor. The missed extractor uses coalescing elements to remove the small droplets of liquid. The gas must take numerous direction changes, which causes the droplets to impinge and collect on the coalescing elements where they fall to the liquid collection section.
- The liquid collecting section of the vessel provides sufficient times that the oil and emulsion form a layer on top of the water
- The water flows from a nozzle at the bottom of the vessel located upstream of the Weir. An interface level controller senses the height of the oil water interface. The controller sends a signal to the level control valve.Allowing the correct amount of water to leave the vessel so that the oil water interface is maintained at the design height
- The gas flows horizontally and out through the mist extractor to a pressure control valve that maintains constant vessel pressure.
What are 2 common types of centrifuges?
- The disc centrifuge
- The scroll centrifuge
Define classification
Classification is the process of separating mixtures of materials according to density
Classification may be used when particles are so small, that separation by screening is not possible
Define flotation
Flotation occurs when the slurry of different solid or semi solid particles is placed in a vessel where the air bubbles rise from the bottom
Some of the solids adhere to the rising bubbles and are carried up to the surface.
Flotation is used to recover copper, lead, zinc and nickel ores.
Oil sands processing also uses flotation to recover bitumen from the middlings layer off the primary settling vessel.
What are four examples of filtration techniques
- Gravity
- Filter press
- Rotary filter
- Electrostatic precipitator
Which type of filter continuously cleans itself?
A rotary filter is designed to continuously clean itself. It is used in applications where the filter would plug off in a short time.
What are 4 forms of mixing?
- Agitating
- Blending
- Dissolving
- Dispersing
What are the 2 types of mixers?
- Static
- Kinetic
What are 2 types of impellers or agitators?
- Radial impellers
- Axial impellers
