Field Scanning Methods of particle size measurement
99 pág.

Field Scanning Methods of particle size measurement

DisciplinaProcessamento de Minerais I211 materiais2.063 seguidores
Pré-visualização28 páginas
0.05 |am. PIDS system has been applied to size determination of several 
pigments [157]. The importance of the imaginary part of the refractive 
index, in calculation of particle size distribution, was stressed. 
Ancillaries include a micro-volume module, a hazardous fluid module 
and a dry powder module. Their small volume module uses less than 
125 ml of diluent. The micro volume module has a total volume of 12 ml; 
this has an internal stirring mechanism to keep particles suspended during 
analyses. The automatic hazardous fluids module can be supplied with a 
microtip eight power ultrasonic probe to keep the particles dispersed. The 
dry powder module analyzes both free flowing and cohesive powders 
covering the size range from 0.375 ^m to 2000 jiim. 
Cilas 920 measures suspensions or dry powders in the size range 0.3 to 
400 Jim without changing the optics. It includes automatic feeding and 
analyses of up to 28 samples and has the capability for displaying particles 
in the 10 to 400 |Lim range using a CCD camera. 
Cilas 1064 has high resolution, giving information over the size range 
0.04 to 500 |um for suspensions and 0.3 to 500 \xm for dry powders in one 
shot, due to a double sequenced laser system (two lasers at different 
incident angles) and 64 separate silicon detectors to give 100 size channels 
of data. The benefits of such a system include coverage of a wide size 
range with a small optical bench structure. The diffraction pattern is 
compared to a known powder and the size distribution calculated. 
Cilas 1180 covers the size range of 0.04 to 2,500 |im, for both wet and 
dry systems, using three lasers with a custom silicon detector and a CCD 
camera, with fast response and high resolution. A wide range of 
accessories includes free fall, small liquid volume unit, alcohol 
recirculator, integrated Windows base and particle visualization. 
Coulter LSI00 uses (PIDS) to extends the lower limit to 0.1 |um and 126 
detectors to measure the scattered light. Multiple optical trains and a wide-
angle detector array are used so that the instrument can simultaneously 
capture light diffracted at high angles from small particles and at small 
angles by large particles. Measurements from 0.1 to 1000 |Lim can be made 
in a single run [158]. 
556 Powder sampling and particle size determination 
Fritsch Analysette 22. The outstanding feature of this instrument is its 
convergent laser beam, with the broad measurement range of 0.16 to 
1250 |im that can be covered in a single pass with no need to change 
optical elements. Moreover, by moving the measurement cell in the beam 
the complete range can be divided into over 400 individual size ranges 
starting at 0.16 to 23.7 |Lim. The instrument is available in four versions; 
A(dvanced), C(onvenient fully automated), E(conomical) and 
Horiba LA-300 is a compact instrument with a built-in auto-alignment 
function. This feature not only maintains ideal operating conditions but 
self-calibrates with the touch of a button. Measurements are performed 
using a 650 nm laser diode, six wide-angle detectors and a 36 channel ring-
shaped silicon diode array detector 
Horiba LA-700 is a more sophisticated instrument that employs side 
and back scattering detectors as well as forward scattering detectors. By 
using a tungsten lamp in conjunction with a He-Ne laser the lower limit is 
reduced to 0.04 |Lim to cover the range 0.04 |Ltm to 262 jum with no change 
in lens. 
Horiba LA-900 extends the upper range to 1000 |am by the use of a long 
focal length lens to cover the range 0.04 to 1000 |Lim with no need to 
change lenses. 
Horiba LA-QIO extends the lower size limit down to 0.02 |j,m with no 
optical changes. Small angle light intensity is measured using a condenser 
lens to condense the light on to a ring-type detector. Detectors are located 
at the side and rear to measure light scattered at larger angles. The 
measurable range is extended with the use of a short wavelength tungsten 
lamp in addition to the He-Ne laser beam. Up to three different dispersing 
media can be stored in the analyzer's reservoir unit that automatically 
injects the right amount of dispersant into the sample. It employs an auto-
cycle agitation, ultrasonic dispersion, circulation and measurement. The 
analyzer uses an iterative deconvolution method to calculate the size 
distribution. The results are displayed in an 80-channel histogram. 
Horiba LA-920 has the functionality of the LA-910 with improved 
software. It has a ring shaped detector in 75 sections together with 12 
wide-angle detectors to give 87 sensing elements that extend the upper size 
limit to 2000 |im. The optical system includes a He-Ne laser for large 
particles together with a shorter wavelength tungsten lamp for small 
particles. The unit comes with a computer, printer, monitor and Windows-
based operator interface. 
Horiba Powder Jet Dry Feeder can be teamed up with the LA-910 or 
LA 920 to disperse and de-agglomerate powders by subjecting them to a 
Field scanning methods 55 7 
high shear rate where high and low velocity air meets at the nozzle exit 
followed by expansion in a low pressure region. An optional vacuum 
sample cell is available for friable powders. A high performance industrial 
vacuum is also included. 
Horiba Autoreservoir, available for the LA-910 and LA-920, is a three-
chamber tank with a built-in pump. The unit supplies liquid to the analyzer 
in response to commands. Concentrated surfactant solutions can be added 
to two of the tanks and then automatically diluted during the fill sequence. 
This automates the supply of dispersant solution for fill, sample dilution 
and rinses. 
Horiba Autofill or Autoreservoir supplies liquid to fill the pumping 
system. The system then circulates the dispersant solution and records the 
Horiba Autosampler or Slurry Sampler then supplies the sample to the 
analyzer. Built-in ultrasonics aid in dispersing the sample. The 
concentration is checked and diluted until it is in the optimum range before 
measurement begins. After the results have been calculated, the data is 
saved or printed. The sample dispersion is then drained and rinse cycles 
prepare the system for the next sample. The Autosampler can make 
continuous measurement of up to 24 different samples. Minute quantities 
of material can be analyzed in the optional Fraction Cell. The unit 
includes a PowderJet dry feeder capable of feeding millimeter size 
powders and dispersing cohesive powders to sizes below Ijiim. Horiba 
claim a higher resolution than similar devices by using repetitive 
calculations instead of the more conventional matrix method. 
A description of the Horiba instruments and a discussion of the 
requirements and physical basis for carrying out particle size 
measurements with these instruments have been presented by Boeck [159]. 
Insitec EPCS is covered in detail in section 10.7. They are laser-based 
instruments for in-line particle measurements that provide information on 
particle volume concentration and size distribution. Unlike other 
instruments operating on this principle, the EPCS can perform direct 
measurements of particle-laden gas flow stream provided the concentration 
is within operating limits. 
Lecotrac-LT-100, manufactured by Leco Corp, uses three lasers and 
two detector arrays to measure light intensities from 0 to 160 degrees. 
Lasers are self-aligning and the instrument uses Windows based software. 
Lecotrac-LT-150 is a basic cost-effective analyzer with a more limited 
size range. 
Lecotrac-LT-200 is designed to analyze coarser particles than the LT-
558 Powder sampling and particle size determination 
Low angle 
detector array 
High angle 
lens High angle 
Fig. 10.9 Low angle on-axis and high angle off-axis array as used with the 
Microtrac Full Range Analyzer. 
The Leco units handle dry or wet samples and an automated small volume