Particle Technology

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CH3041 Chemical Engineering Unit Operations II
Lau Wai Man, Raymond Jiang Rongrong Office: N1.2-B2-32 Office: N1.2-B1-08 Phone: 6316 8830 Phone: 6514 1055 Email: wmlau@ntu.edu.sg Email: rrjiang@ntu.edu.sg

Course Outline
•  Particulate Technology –  Particle size analysis –  Packed bed –  Gas-solid fluidized bed –  Gas-liquid-solid fluidized bed •  Filtration •  Crystallization •  Drying

Covered by Prof. Jiang Rongrong

Grading
•  Continuous Assessment –  30% Quizzes •  Exam –  70% Final Exam

Text
Particulate Technology •  Liang-Shih Fan and Chao Zhu, Principles of Gas-solid flows, Cambridge University Press, 1998. •  Ch.1.1-1.3; Ch.5.6; Ch.9.1-9.7; Ch.10.1-10.3; Ch.11.1-11.4

CA policy
•  If student misses CA due to following reasons:
–  valid MC (not from Chinese doctor) –  passing away of immediate family (parents, siblings, grandparents) –  participate in an activity representing NTU then the CA component will be counted towards the final exam. There will be no makeup CA.

•  Otherwise student gets 0 for CA.

Tentative Schedule
Week of
9/1/2012 16/1/2012 23/1/2012 30/1/2012 6/2/2012 13/2/2012 20/2/2012 27/2/2012 5/3/2012 12/3/2012 19/3/2012 26/3/2012 2/4/2012 9/4/2012 LT LT LT LT LT LT LT LT LT LT LT LT

- Tutorial Week - Holiday
Mon
LT LT

Tue
LT LT Chinese New Year LT LT LT LT

Wed

Thu

Fri

Chinese New Year LT LT LT Quiz (CA1)

Recess

Good Friday

Particulate Technology
Particulate systems impact a number of industries including advanced materials, environmental, chemical, mineral, energy, agricultural, pharmaceutical, and food processing. Particle technology deals with the characterization, modification, handling, production and utilization of a wide variety of particles, in both dry and wet conditions. Recently, these issues are being reinvestigated for the nano- and bio-technologies.

Particulate Technology
The fourth phase in the nature: “powder” or “particulate solids” phase Not solid, but can withstand some deformation Not liquid, but can flow Not gas, but can be compressed Having some characteristics of the other three phases, but does not belong to any of the other phases.

Size and Properties of Particles
The flow characteristics of solid particles in a gas-solid suspension vary significantly with the geometric and material properties of the particle.

Material properties include such characteristics as physical adsorption, elastic and plastic deformation, ductile and brittle fracturing, solid electrification, magnetization, heat conduction and thermal radiation, and optical transmission.

Particle Size and Sizing Methods
Sieve Diameter: The width of the minimum square aperture through which the particle will pass. Sieve diameter Minimum dimension Maximum dimension

dv ds

Martin’s Diameter, Feret’s Diameter, and Projected Area Diameter: Measured based on the projected image of a single particle. Martin’s diameter – Averaged cord length of a particle which equally divides the projected area Feret’s diameter – Averaged distance between pairs of parallel tangents to the projected outline of the particle Projected area diameter – dA=(4A/π)1/2 The particle orientation under which the measurement is made, is important! Thus, use a large number of sampled particles.

Based on 3-D geometric characteristic of particle Surface Diameter: the diameter of a sphere having the same surface area as the particle

ds =

S

π

Volume Diameter: the diameter of a sphere having the same volume as the particle

⎛ 6V ⎞ d v = ⎜ ⎟ ⎝ π ⎠

1 3

Sauter’s Diameter (surface-volume diameter): the diameter of a sphere having the same volume to surface ratio as the particle

6V d v3 d 32 = = 2 S ds
Dynamic Diameter: the diameter of a sphere having the same density and the same terminal velocity as the particle in a fluid of the same density and viscosity

Re t µ dt = ρ U pt
where Ret is the particle Reynolds number at the terminal...
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