12 Property Function to Compute the Dustiness of Powders
415
1 Introduction
The dust formation tendency (dustiness) of bulk materials can be understood as
release of particle fractions of a special quantity and size distribution into a gaseous
environment given certain handling. Dustiness of bulk materials may change along
the process path, for example, through comminution, agglomeration, classification
or mixing of the solids involved. In general, such release of particles is undesirable
because it might result in material loss, is often associated with personnel being
exposed to it and may cause environmental pollution.
Within the scope of DFG-focus program 1679 “Dynamic simulation of interlinked solid matter processes”, empirical formulas describing these processes were
developed by the project group B1 “Property functions for calculating dust formation tendency of powders”. Dustiness forecast functions were derived from the three
testing methods “single drop”, “UNC dustiness tester”, and “rotating drum”, taking
into account material density, particle mass and size distribution, particle shape and
moisture. By implementing these functions into the DYSSOL flowsheet simulation
framework, dust formation tendencies of simulated products can be predicted within
the flowsheet. Additionally dustiness quantification of powders based on fractional
release rate and established laboratory testing methods was experimentally investigated. These findings were meant to support the work of cooperation partners and
may improve the fractional release model developed recently [1].
2 Experimental Investigations
2.1 Cooperation with Project A1: Influence of Deposit
Thickness on Powder Layer Dustiness
In cooperation with project A1 “Process modeling for dynamic disperse separation and deposition processes”, maintained by University of Bremen, dynamic layer
growth and layer stability in separation processes of particulate material from fluid
streams was investigated.
For this purpose powder layers of varying thicknesses were generated within an
electrostatic precipitator at the University of Bremen. Filter test materials Pural NF
(bohemite, density 2.47 g/cm
3 , bulk density 0.51 g/cm
3 ) and Ulmer Weiß XMF
(limestone, density 2.68 g/cm
3 , bulk density 0.66 g/cm
3 ) were utilized in these tests.
Particle size distrubutions were determined with a Retsch made Horiba LA-950
laser light diffraction measurement unit. Particle size of Pural NF ranges from x 10,0
= 1.34 µm to x 90,0 = 4.29 µm with the number median x 50,0 = 1.98 µm and a
standard deviation of 1.77 µm. Particle size of Ulmer Weiß XMF ranges from x 10,0
= 0.57 µm to x 90,0 = 2.28 µm with the number median x 50,0 = 1.16 µm and a
standard deviation of 0.81 µm. Both materials have a white color.
415
1 Introduction
The dust formation tendency (dustiness) of bulk materials can be understood as
release of particle fractions of a special quantity and size distribution into a gaseous
environment given certain handling. Dustiness of bulk materials may change along
the process path, for example, through comminution, agglomeration, classification
or mixing of the solids involved. In general, such release of particles is undesirable
because it might result in material loss, is often associated with personnel being
exposed to it and may cause environmental pollution.
Within the scope of DFG-focus program 1679 “Dynamic simulation of interlinked solid matter processes”, empirical formulas describing these processes were
developed by the project group B1 “Property functions for calculating dust formation tendency of powders”. Dustiness forecast functions were derived from the three
testing methods “single drop”, “UNC dustiness tester”, and “rotating drum”, taking
into account material density, particle mass and size distribution, particle shape and
moisture. By implementing these functions into the DYSSOL flowsheet simulation
framework, dust formation tendencies of simulated products can be predicted within
the flowsheet. Additionally dustiness quantification of powders based on fractional
release rate and established laboratory testing methods was experimentally investigated. These findings were meant to support the work of cooperation partners and
may improve the fractional release model developed recently [1].
2 Experimental Investigations
2.1 Cooperation with Project A1: Influence of Deposit
Thickness on Powder Layer Dustiness
In cooperation with project A1 “Process modeling for dynamic disperse separation and deposition processes”, maintained by University of Bremen, dynamic layer
growth and layer stability in separation processes of particulate material from fluid
streams was investigated.
For this purpose powder layers of varying thicknesses were generated within an
electrostatic precipitator at the University of Bremen. Filter test materials Pural NF
(bohemite, density 2.47 g/cm
3 , bulk density 0.51 g/cm
3 ) and Ulmer Weiß XMF
(limestone, density 2.68 g/cm
3 , bulk density 0.66 g/cm
3 ) were utilized in these tests.
Particle size distrubutions were determined with a Retsch made Horiba LA-950
laser light diffraction measurement unit. Particle size of Pural NF ranges from x 10,0
= 1.34 µm to x 90,0 = 4.29 µm with the number median x 50,0 = 1.98 µm and a
standard deviation of 1.77 µm. Particle size of Ulmer Weiß XMF ranges from x 10,0
= 0.57 µm to x 90,0 = 2.28 µm with the number median x 50,0 = 1.16 µm and a
standard deviation of 0.81 µm. Both materials have a white color.