(a)
The critical speed of the trommel screen.
Answer to Problem 5.11P
Explanation of Solution
Given:
The diameter of trommel screen is
The length of trommel screen is
The angle of inclination is
Concept Used:
Write theexpression to calculate the critical speed of trommel screen.
Here, the acceleration due to gravity is
Calculation:
Calculate the critical speed of trommel screen.
Substitute
Conclusion:
Thus, the critical speed of trommel screen is
(b)
The type of movement of MSW in the trommel screen.
Answer to Problem 5.11P
The movement of MSW in trommel screen is cataracting.
Explanation of Solution
Given:
The speed of trommelis
The feed rate is
Calculation:
The movement of MSW is determined by using the relation
Here,
Hence the movement of MSW is either cascading or cataracting.
The critical speed and the fraction of the screen occupied by the refuse are related which gives the process of movement of MSW.
Write the equation to calculate the bulk volume.
Here, the bulk volume of trommel screen is
Consider a single particle in the screen.
The following figure shows the force analysis diagram.
Figure-(1)
Here, gravity is
Write the equilibrium equation for the x and y axis as shown in Figure-(1).
Here, the coefficient of friction is
Write the equation to calculate acceleration.
Here, the acceleration is
Substitute
Calculate time for particle to move from end to end.
Here, the length is
Substitute
Calculate the volume occupied by the solids and the air spaces between the solids.
Here, the mass flow rate is
Convert the unit of
Convert the unit of time to
Substitute
Calculate the total volume inside the trommel screen.
Substitute
Calculate the bulk volume of trommel screen.
Substitute
The following graph shows critical speed and the fraction of the screen occupied by the refuse are related which gives the process of movement of MSW.
Figure-(2)
Since,
Conclusion:
The type of movement is calculated by equating time, bulk volume, mass flow, density, speed and feed rate.
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Chapter 5 Solutions
Solid Waste Engineering
- Solid Waste EngineeringCivil EngineeringISBN:9781305635203Author:Worrell, William A.Publisher:Cengage Learning,