Introduction to Dry Particle Analysis

Transcription

1 Introduction to Dry Particle Analysis Today, many dry particle size analyzers are working with high air pressure in order to avoid agglomeration of sticky powders. This leads to broken particles whose size distribution is underestimated. Cilas decided to develop a new dry dispersion technique and set high expectations for the project: -Excellent reproducibility and accuracy -Improved dispersion for any type of sticky powder -Extended measurement range Cilas engineers worked with fluid dynamics experts from the EADS group to improve the dispersion system in order to smoothly disperse sticky powders. The result is an optimized air-particle mixing system which improves the dispersion of dry powders. The project team added an additional constrain: develop a traceable solution for calibration of the instrument. After 2 years of development, the team came up with an innovative technology : Dry Jet Dispersion Dispersion Challenge #1: Deaglomeration without breaking the particles! Dispersion Challenge #2: Traceability of the results! Fig 1. Visualisation of dry particle flow 1/8

2 How does DJD Technology work? The powder is introduced in a mixing chamber where an airflow exchanges energy with the particles. The resulting two phases flow is then directed to the laser path through a succession of venturi sections and a special nozzle. Many parameters are involved in the process: pressure distribution in the mixing chamber, particle flow properties, mass flow, air flow rate, exhaust pressure, etc. Software Simulation of the velocity distribution in the mixing chamber The complex design of the mixing chamber and the nozzle ensure that the airflow disperses the powder in a fine and homogeneous particle cloud. The deagglomeration is obtained by airflow turbulence combined with particle-particle and particle-wall collisions. Very fine and coarse particles from hard or brittle material are efficiently dispersed for precise analysis using laser diffraction. Wall collision Accurate control of each parameter allows the user to adapt the system to any type of powder. Technical specifications Range Units Air flow L/s Mass flow 0-5 Gr/s Working pressure 0-4 by 0,01 steps Bars Velocity 0-40 M/s Accuracy < 3% on D50 Reproductibility < 1% D50 Measurement Range 0,1 µm µm Measurement time 5 to 15 Sec 2/8

3 Measurement of Certified Reference Cement using DJD Technology Sample Description: NIST Certified Cement, ref 1149 Purpose of the Analysis: To demonstrate the ability of the Cilas DJD technology to measure the size of certified cement particles. The analysis must evaluate the quality of the dry dispersion in terms of signal reproducibility and size accuracy. Results : NIST certified results at 45µm: 0.79 % Cilas results at 45 µm: 0.74 % (using 3 independent measurements) Results summary: The excellent reproducibility (less than 1% over 3 measurements) shows that the cement cohesive powder is properly dispersed. The pressure required to disperse the powder is low (less than 1 bar) and prevents the possible break down of particles. Fine dispersion at low pressure is one of the major advantages of DJD technology. 3/8

4 Measurement of Calcium Cabonate using DJD Technology Sample Description: Ca CO 3 Purpose of the Analysis: To demonstrate the ability of the Cilas DJD technology to disperse fine and cohesive powders. Results : Results summary: The dispersion of the powder remains efficient even in the submicron range. The excellent reproducibility (less than 1% in 5 measurements) shows that a fine and cohesive powder such as calcium carbonate is properly dispersed (D50=1.2µm). 4/8

5 Measurement of Certified Reference Glass Beads using DJD Technology Sample Description: Whitehouse Scientific PS µm Glass Beads Purpose of the Analysis: To demonstrate the compliance of Cilas DJD technology to the ISO standard. This analysis also evaluates the correlation between dry and wet mode. Results : Whitehouse certified limits Reproducibility test on µm glass beads from Whitehouse. Results summary: The excellent reproducibility (less than 1% in 5 measurements) shows that the powder is properly dispersed. An exceptional correlation between dry and wet modes (less than 3%) is obtained because of the innovative calibration method of the two dispersion modes according to the ISO standard. 5/8

6 Enter the ISO World with DJD Technology Proper calibration and verification of a dry particle size analyzer requires a large quantity of Certified Reference Powder (5 times more powder than in wet mode). This is a major obstacle to the ISO qualification of a dry dispersion system. Cilas developed a specific Certified Reference Material for dry calibration in order to get the right accuracy and traceability while keeping the cost as low as possible. The CSR (Cilas Secondary Reference Powder), available in 5 gr single shot vials, is traceable to an international standard. This technology means our systems are compliant with all requirements of the ISO standard. The standard calibration procedure ensures a perfect correlation between wet and dry modes. Most other dry measurement systems available on the market today are calibrated using a grid or masks. These approximated methods verify only the optical system and do not verify the dry dispersion system. Therefore, they are not compliant with the ISO standard. CSR Kit The ISO Standard The standard requires that the manufacturer calibrates the instrument using Certified Reference Materials (CRMs) of a known size distribution. The user must also verify operation of the instrument, both repeatability and accuracy, at regular time intervals using CRMs. Cilas Traceability Certificates Single shot vials - 5 gr Reduce time Improve accuracy 6/8

7 DJD is a Breakthrough Technology offering the market an Innovative Solution for dry particle measurement. Superior accuracy that is traceable with ISO calibration (better than 3 %). Excellent correlation with wet mode because of the unique calibration method. The best reproducibility because of the short fixed optical bench (better than 1 %). The 2/1 concept allows the user to choose between the wet or dry dispersion system. Both systems are integrated in the instrument and switching from one to the other does not require hardware changes or optical realignment. Switch between modes in software with a single click of the mouse. Quick measurements, which minimize the workload and time involved, are available due to the easy operation and user-friendly software. Fast, cost effective calibration is provided using the build in procedure. Robust design, not affected by dust or vibration, provides reliable analysis even under adverse industrial conditions. Switch to DJD with just the click of the mouse! Wet Mode Dry Mode No hardware modification or realignment needed! 7/8

8 Technical specifications DJD DJD technology is available on Cilas instruments in 3 different measurement ranges. All instruments are available with the DJD system alone or in combination with the Wet Iso Dispersion system (WID system). Principe of measurement Modes of calculation Laser Diffraction Fraunhöfer, Mie DJD TECHNOLOGY INSIDE Laser Diffraction & CCD camera Range µm µm µm Number of classes Ways of Dispersion Venturi Accuracy < 3 % on NIST traceable CRM (1) Venturi - Free Fall Repeatability < 1 % on NIST traceable CRM (1) Performances compliant with ISO norm Amount of sample 5 g minimum Acquisition time 5 s minimum Compressed Air (2) 0-4 +/ bars Number of lasers Wavelength Power Length/width/height Weight nmg 635 and 830 nm 635 and 830 nm 110/240 V - 50/60 Hz - < 100 VA) 830 mm / 560 mm 480 mm (33 in / 22 in / 19 in) 50 kg (110 lbs) 54 kg (119 lbs) 60 kg (132 lbs) (1): measures of diameter by weight made on certified reference materials, traceable to NIST standards (2): Air compressor and vacuum cleaner systems available in option 3 ISO CFR 21 Contact us: info.particle@cilas.com Find a local dealer at www. particle-size-analyzer.com 8/8