Processing
Crushing
Learning Objectives:
- Define and explain the fundamental principles of crushing, including its purpose and importance in various industrial processes.
- Differentiate between crushing and other size reduction processes, such as grinding and milling.
- Identify and describe common types of crushing equipment, including jaw crushers, cone crushers, and impact crushers.
- Crushing is the first mechanical stage in extraction and refining of ore.
- It is generally a dry operation and is usually performed in two or three stages.i.e primary,secondary and tertiary stage.
- In Primary crushing the feed size of ore can be as large as 1.5m and is reduced to 10-20cm in heavy duty machines.
- Crushing may be done in open circuit or closed circuit.
- In open-circuit crushing, undersize material from the screen is combined with the crusher product and is then routed to the next operation.
- In Closed-circuit crushing, the undersize from the screen is the finished product.
Skiffm Anatoly Verevkin (Анатолий Веревкин), Public domain, via Wikimedia Commons
Solved Example: 9102-01
On which of the following factors the crushing strength of stone does not depend?
A. Texture
B. Workability
C. Specific gravity
D. Both the texture and specific gravity
Correct Answer: B
Solved Example: 9484-01
What is the primary purpose of the crushing process in chemical engineering?
A. Separation of components
B. Particle size reduction
C. Heat transfer enhancement
D. Mixing enhancement
Correct Answer: B
Solved Example: 9484-02
Which of the following factors influences the efficiency of a crushing operation?
A. Temperature
B. Pressure
C. Feed particle size
D. Flow rate
Correct Answer: C
Solved Example: 9484-03
Which type of crushing equipment is typically used for reducing large-sized particles to a finer size by applying compressive forces?
A. Jaw crusher
B. Hammer mill
C. Ball mill
D. Fluidized bed reactor
Correct Answer: A
Grinding
Learning Objectives:
- Define and explain the fundamental principles of grinding, including its purpose and importance in various industrial processes.
- Differentiate between grinding and other size reduction processes, such as crushing and milling.
- Identify and describe common types of grinding equipment, including ball mills, rod mills, and grinding wheels.
- Grinding is a process of removing material by abrasive action of a revolving wheel on the surface of a work-piece in order to bring it to required shape and size.
- The wheel used for performing the grinding operation is known as grinding wheel It consists of sharp crystal called abrasive held together by a binding material or bond.
- The wheel may be a single piece or solid type or may be composed of several segments of abrasive blocks joined together.
JzG, CC BY-SA 3.0, via Wikimedia Commons
Solved Example: 9104-01
Grinding of hard materials requires:
A. Fine grit size and hard grades
B. Fine grit size and soft grades
C. Coarse grit size and hard grades
D. Coarse grit size and soft grades
Correct Answer: B
Solved Example: 9104-02
Which factor decides the selection of the grinding wheel?
A. Abrasive
B. Grain size
C. Grade
D. Structure
Correct Answer: B
Solved Example: 9104-03
Grinding is a:
A. Multi-point machining process
B. Non-traditional machining operation
C. Single point machining process
D. None of the given options
Correct Answer: A
Solved Example: 9463-01
Which of the following grinding mills operates by tumbling action and uses grinding media such as balls or rods?
A. Jaw Crusher
B. Hammer Mill
C. Ball Mill
D. Fluid Energy Mill
Correct Answer: C
Solved Example: 9463-02
Which factor is essential for achieving efficient grinding in a ball mill?
A. Low rotational speed
B. Small grinding media size
C. High feed particle size
D. Decreased residence time
Correct Answer: B
Solved Example: 9463-03
In the context of grinding, what is the critical speed of a rotating mill?
A. The speed at which grinding media adheres to the mill walls
B. The speed at which the mill achieves maximum efficiency
C. The speed at which the mill stops rotating
D. The speed at which particle size reduction is minimal
Correct Answer: B
Crystallization
Learning Objectives:
- Define crystallization and explain its significance in chemical engineering processes. Understand the basic principles of nucleation and crystal growth.
- Differentiate between various types of crystallization processes, such as cooling, evaporation, and precipitation.
- Explain when each type is suitable for different applications.
This image has been created during "DensityDesign Integrated Course Final Synthesis Studio" at Polytechnic University of Milan, organized by DensityDesign Research Lab in 2015. Image is released under CC-BY-SA licence. Attribution goes to "Elisa Riva, DensityDesign Research Lab"., CC BY-SA 4.0, via Wikimedia Commons
Solved Example: 9103-01
The crystallization technique is better than the simple evaporation technique and:
1. Crystallization is a process that separates a pure solid in the form of its crystals from a solution.
2. it is applied for the purification of salt that we get from seawater.
3. it is applied for the separation of crystals of alum from impure samples.
Select the correct answer using the code given below.
A. 2 only
B. 1 only
C. 1, 2 and 3
D. 3 only
Correct Answer: C
Solved Example: 9103-02
Crystallisation is an example of?
A. Physical Change
B. Chemical Change
C. Chemical Reaction
D. Galvanisation
Correct Answer: A
Solved Example: 9103-03
Out of the following, which salt has no water of crystallization?
A. Gypsum
B. Blue vitriol
C. Washing soda
D. Baking soda
Correct Answer: D
Solved Example: 9476-01
What is the primary purpose of crystallization in chemical engineering processes?
A. Separation of gases
B. Production of high-purity solids
C. Enhancement of heat transfer
D. Control of fluid flow
Correct Answer: B
Solved Example: 9476-02
Which method is commonly used to monitor and control the crystallization process to achieve the desired crystal size distribution?
A. X-ray diffraction
B. Fourier-transform infrared spectroscopy
C. Ultraviolet-visible spectroscopy
D. Particle size analysis
Correct Answer: D