310204d Solids And Liquids

Question 1

What type of product consistency does grinding produce?

Answer 1

A fine powder.

Question 2

What type of crushing action is used with a Bradford Breaker?

Answer 2

Impact gravity crushing.

Question 3

Why is water often added to the charge feeding a ball mill?

Answer 3

The water cools the mill and helps to convey the finer crushed material along to the discharge point.

Question 4

Explain the purpose for adding flocking agents to a flocculation process

Answer 4

The purpose of most flocking agents is to neutralize negative charges on the particles to prevent them from repelling each other

Question 5

Define granulation and explain how the process works

Answer 5

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

Question 6

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

Answer 6

True

Question 7

A screening system can sort into how many grades

Answer 7

The screening system sorts into a number of grades where the number of grades is equal to the number of screens plus 1

Question 8

What are 2 conditions that can cause a screen to become blinded?

Answer 8

1. Particles that are close to the hole size of the screen
2. Material that is wet

Question 9

True or false
When using a trommel screen, the finer material exits the end of the screen.

Answer 9

False
With a trommel design, the finer material exits first, then the intermediate material and finally the course material exits the discharge and last

Question 10

What type of separator uses centrifugal force to remove solids from a gas stream and has no moving parts?

Answer 10

A cyclone separator

Question 11

What accumulates on the inside surface of the bowl of a scroll centrifuge?

Answer 11

Solids or heavy liquids

Question 12

Which cleaning method does not require the filter to be opened for cleaning?

Answer 12

The backwashing filtration method

Question 13

True or false
When using a filter press for filtering, increasing the number of filter cells increases the pressure drop

Answer 13

False
Increasing the number of filter cells allows the same flow rate to be handled at a lower pressure drop.

Question 14

Name the piece of equipment that removes the dust particles from the electrode plate in an electrostatic precipitator

Answer 14

The rapper

Question 15

What does a good static mixer design accomplish?

Answer 15

A well-designed static mixer can create maximum turbulence with minimal pressure drop

Question 16

What flow direction is created with the use of a radial impeller?

Answer 16

Flow is perpendicular to the direction of the shaft.

Question 17

What flow direction is created with the use of an axial impeller?

Answer 17

Flow is parallel to the direction of the shaft

Question 18

What kind of mixtures would a double spiral impeller be used for?

Answer 18

The double spiral impeller is used for very viscous mixes

Question 19

Define ‘crushing by attrition’

Answer 19

Crushing by attrition is a rubbing or grinding action

Question 20

Define flocculation

Answer 20

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

Question 21

What are 3 examples of colloidal solids?

Answer 21

1. Bacteria
2. Fine clays
3. Silts

Question 22

Define suspended solids

Answer 22

Suspended solids, also known as settleable solids, settle out of water over time although this process can be awfully slow.

Question 23

What are two examples of suspended solids

Answer 23

1. Sand
2. Heavy silts

Question 24

Do most colloidal and suspended solids in water, have a negative or positive charge?

Answer 24

Most colloidal and suspended solids in water have a negative charge, so they tend to repel each other

Question 25

What are Flocking agents?

Answer 25

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.

Question 26

Define Agglomeration

Answer 26

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

Question 27

Define extrusion.

Answer 27

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.

Question 28

What are the 2 classifications for separators?

Answer 28

1. Two-phase separators 2. Three-phase separators

Question 29

What is the difference between a two-phase separator and a three-phase separator?

Answer 29

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.

Question 30

Describe the basic operation of a two-phase separator

Answer 30

1. Gas enters the separator through the inlet 2. The inlet diverter changes the direction of flow, liquid momentum is absorbed, causing the initial separation of liquid and gas 3. In the gravity settling section, the larger liquid drops fall to the liquid collection section 4. Smaller liquid drops remain with with the gas and pass through the mist extractor 5. 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 6. The liquid leaves the vessel through the level control valve. 7. The level controller senses changes in liquid level and controls the valve accordingly.

Question 31

Describe the basic operation of a three-phase separator.

Answer 31

1. Gas enters through the inlet 2. The inlet diverter changes the direction of flow, liquid momentum is absorbed, causing the initial separation of liquid and gas 3. In the gravity saddling section, the larger liquid drops fall to the liquid collection section 4. 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. 5. The liquid collecting section of the vessel provides sufficient times that the oil and emulsion form a layer on top of the water 6. 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 7. The gas flows horizontally and out through the mist extractor to a pressure control valve that maintains constant vessel pressure.

Question 32

What are 2 common types of centrifuges?

Answer 32

1. The disc centrifuge 2. The scroll centrifuge

Question 33

Define classification

Answer 33

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

Question 34

Define flotation

Answer 34

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.

Question 35

What are four examples of filtration techniques

Answer 35

1. Gravity 2. Filter press 3. Rotary filter 4. Electrostatic precipitator

Question 36

Which type of filter continuously cleans itself?

Answer 36

A rotary filter is designed to continuously clean itself. It is used in applications where the filter would plug off in a short time.

Question 37

What are 4 forms of mixing?

Answer 37

1. Agitating 2. Blending 3. Dissolving 4. Dispersing

Question 38

What are the 2 types of mixers?

Answer 38

1. Static 2. Kinetic

Question 39

What are 2 types of impellers or agitators?

Answer 39

1. Radial impellers 2. Axial impellers