Yenni Listiana 120405008Hilde Rosa Tampubolon 120405109

Size distribution measurement of floating particles in the Allen regionby a buoyancy weighing-bar method

By: Rondang Tambun, Takumi Motoi, Masamitsu Shimadzu, Yuichi Ohira, Eiji ObataRondang Tambun, Takumi Motoi, Masamitsu Shimadzu, Yuichi Ohira, Eiji Obata

What is the background of this

research ?

Stokes diameter, Andreasen pipette method, Sedimentation balance method, Centrifugal sedimentation method

Laser diffraction/scattering method ,and Coulter counter method

Time consuming and require special skills

The equipment is extremely expensive

What is BWM?

BWM measures the change in suspension density due to particle migration by weighing the buoyancy against a weighing-tool hung in the suspension, and subsequently calculating the particle size distribution using the length of the weighing-tool and the time-course change in the apparent mass of the weighing-tool

What’s the purpose of this research?

Theoretically, a buoyancy weighing-bar method should be applicable to measurethe particle size distribution in both the Stokes and Allen regions

Particle size x is given by the Allen formula

How they do this research?

1. To prepare a suspension, 1000 ml liquid and the particles to be tested were mixed in a graduated cylinder..

2. The weighing-tool was hung from an electronic precision weighing balance using a hanging wire, which did not extend due to the weight of the weighing-tool.

3. After thoroughly stirring the suspension using an agitator, the weighing-tool was set with the balance, and this was recorded as t = 0 s.

4. The measuring data, which consisted of time t and the corresponding mass of the weighing-tool, were recorded on a personal computer.

5. After the measurements, we calculated the particle size distribution of the tested particles based on the above-described theory.

What is the materials?

The initial volume concentration of the suspension was set to 0.01, and the temperature during the experiment was maintained at 298 K. Measurements lasted 150 s.

Spherical ParticlesSpherical ParticlesWhat is the result?

Apparent mass of the weighing-tool as a function of time

Particle size distributions of spherical particle

Cylindrical particleCylindrical particle

Apparent mass of the weighing-tool as a function of time

Particle size distributions of cylindrical particle

conclusionsconclusions

1. Although particles in the Allen region migrate, the floating particle size distributions of solid particles can be measured by the buoyancy weighing-bar method.

2. The precision of the particle size distribution is comparable to that obtained by a laser diffraction/scattering method or a sieving method.

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