What is the primary mechanism of size reduction in roller mills?
Anonymous Quiz
8%
a) Impact
14%
b) Attritio
7%
c) Cutting
70%
d) Compression and shearing
🤝1
In a hammer mill, what happens to the material that is small enough to pass through the
screen?
screen?
Anonymous Quiz
14%
a) It is further ground by the hammers
20%
b) It is retained for additional size reduction
59%
c) It is discharged almost as fast as it is formed
7%
d) It is sent to a classifier for further processing
Which factors affect the particle size achievable in a hammer mill?
Anonymous Quiz
49%
a) Type of milling tool, rotor speed, and solid density in the mill
13%
b) Hammer tip speed, screen thickness, and type of milling tool
7%
c) Rotor speed, screen size, and solid feed rate
31%
d) Hammer tip speed and hammer mill screen size
What is the relationship between hammer tip speed and particle size reduction in a hammer
mill?
mill?
Anonymous Quiz
17%
a) Higher hammer tip speed results in larger particle sizes
74%
b) Higher hammer tip speed results in smaller particle sizes
5%
c) Hammer tip speed has no effect on particle size reduction
4%
d) Lower hammer tip speed results in smaller particle sizes
What industries commonly use hammer mills for size reduction?
Anonymous Quiz
78%
a) Pharmaceutical and food industries
10%
b) Chemical and mining industries
9%
c) Construction and automotive industries
2%
d) Textile and paper industries
What is a major advantage of hammer mills?
Anonymous Quiz
15%
a) They produce a wide size distribution
6%
b) They have a low capacity
74%
c) They are compact with a high capacity
5%
d) They require a complex installation process
What is a limitation of hammer mills in producing ultrafine particles?
Anonymous Quiz
80%
a) They require internal or external classification
7%
b) They cannot handle wet materials
8%
c) They can only be operated as an open system
6%
d) They have a high probability of causing explosions
What is the primary grinding medium in a ball mill?
Anonymous Quiz
12%
a) Air
79%
b) Steel balls or pebbles
3%
c) Water
6%
d) Compressed steam
🤝1
How does the speed of rotation affect the size reduction in a ball mill?
Anonymous Quiz
24%
a) Higher speed increases attrition action
18%
b) Lower speed increases impact action
54%
c) Higher speed increases impact action
4%
d) Speed of rotation has no effect on size reduction
What type of milling operation can be performed in a ball mill?
Anonymous Quiz
10%
a) Wet milling only
7%
b) Dry milling only
80%
c) Both wet and dry milling
4%
d) Neither wet nor dry milling
What is an advantage of using ball mills for unstable or explosive materials?
Anonymous Quiz
62%
a) They can be sealed within an inert atmosphere
17%
b) They can be sterilized and sealed for sterile milling
13%
c) They have low installation, operation, and labor costs
8%
d) They are efficient for fine grinding of hard and abrasive materials
In a fluid-energy mill, what is the primary force responsible for particle size reduction?
Anonymous Quiz
7%
a) Impact
14%
b) Compression
77%
c) Attrition
2%
d) Cutting
Why is air commonly used as the fluid in fluid-energy mills for pharmaceuticals?
Anonymous Quiz
3%
a) It is less expensive than other fluids
4%
b) It has a lower viscosity than other fluids
90%
c) Most pharmaceuticals have a low melting point or are thermolabile
2%
d) It is more efficient for size reduction than other fluids
What is a crucial factor to consider when selecting fluid-energy mills for production?
Anonymous Quiz
5%
a) The speed of rotation
42%
b) The number and angle of the nozzles
46%
c) The cost of a fluid-energy source and dust collection equipment
7%
d) The grinding chamber geometry
What is a primary advantage of fluid-energy mills?
Anonymous Quiz
13%
a) Low capital and running costs
71%
b) Quick production of powders with all particles below a few micrometers
10%
c) Low potential for build-up of compressed product in the mil
5%
d) No need for dust collection equipment
What is a disadvantage of fluid-energy mills in terms of cost?
Anonymous Quiz
10%
a) Low capital and running costs
58%
b) High capital and running costs
25%
c) High installation costs but low running costs
7%
d) Low installation costs but high running costs
What is a drawback of fluid-energy mills related to milled particle size?
Anonymous Quiz
73%
a) The potential for build-up of compressed product in the mill
15%
b) The inability to produce particles smaller than a few micrometers
4%
c) The inefficiency in grinding hard and abrasive materials
7%
d) The high cost of dust collection equipmen
Which type of material cannot be crushed by pressure or impact and must be cut instead?
Anonymous Quiz
86%
a) Fibrous materials
7%
b) Friable materials
7%
c) Moist materials
0%
d) Solid materials
At what percentage of water content does comminution become hindered during milling?
Anonymous Quiz
78%
a) 5%
6%
b) 10%
2%
c) 25%
13%
d) 50%
What effect does an increase in moisture content have on the rate of milling to a specified
product size?
product size?
Anonymous Quiz
11%
a) Increases the rate
78%
b) Decreases the rate
1%
c) No effect on the rate
9%
d) Rate varies depending on the material