Asst. Prof. Jewel A. CapunitanDepartment of Chemical EngineeringCollege of Engineering and Agro-Industrial TechnologyUniversity of the Philippines Los Baños

ChE 154 - Transfer Operations II1st sem. 2014-2015

PROPERTIES OF SOLIDS

PARTICLE SIZE: ADDITIONAL NOTES

REFERENCES: http://golik.co.il/Data/ABasicGuidtoParticleCharacterization%282%29_1962085150.pdfhttp://www.horiba.com/fileadmin/uploads/Scientific/eMag/PSA/Guidebook/pdf/PSA_Guidebook.pdf

PARTICLE SIZE

• influences many properties of particulate materials and is a valuableindicator of quality and performance

• important in various industries as it influences material properties suchas:

reactivity or dissolution rate e.g. catalysts, tabletsstability in suspension e.g. sediments, paintstexture and feel e.g. food ingredientsappearance e.g. powder coatings and inksflowability and handling e.g. granulespacking density and porosity e.g. ceramics

PARTICLE SIZE

WHICH SIZE TO MEASURE?

• For a spherical particle: size =diameter because everydimension is identical

• For non-spherical particle:multiple length and widthmeasures (horizontal andvertical projections are shownbelow) but requires greatcomplexity

Figure 1. Particle size measurement

PARTICLE SIZE

WHICH SIZE TO MEASURE?

• Equivalent spherical diameter: many techniques make the usefuland convenient assumption that every particle is a sphere

• This approach is simplistic and not perfectly accurate but for mostindustrial processes, the shapes of particles generated are suchthat the spherical assumption does not cause serious problems

PARTICLE SIZE

Figure 2. Equivalent spherical diameter

PARTICLE SIZE DISTRIBUTION

• Performing a particle size analysis is the best way to answer the question:What size are those particles?

• Reporting the result: average size - a single number cannot describe thedistribution of the sample

• Interpreting results of a particle size measurement requires anunderstanding of which technique was used and the basis of thecalculations

• Each technique generates a different result since each measures differentphysical properties of the sample. Once the physical property ismeasured a calculation of some type generates a representation of aparticle size distribution

EXAMPLE: PSD INTERPRETATION - NUMBER VS. VOLUME DISTRIBUTION

Figure 3. Particles with different sizes (left) and corresponding number and volume distributions (center and right)

EXAMPLE: PSD INTERPRETATION - NUMBER VS. VOLUME DISTRIBUTION

Figure 4. Another example of number and volume distributions

PARTICLE CHARACTERIZATION TECHNIQUES

Figure 5. Particle characterization systems