Laser Light Diffraction Technique for Particle Sizing

This paper describes a laser diffraction particle stzing technique applications and hardware improvements. With sound theoretical background, this technique finds itself competing in the particle sizing technology market with the introduction of Malvern model series 1800, 2600 and Master Sizer of which the first two models have been tested extensively. Correction schemes to overcome same basic major problems such as multiple scattering of particles and vignetting effect also presented. Instrument calibration and comparative performance notably with the phase Doppler and other sizing techniques were made. Overall results show that by resolving some basic major problems and instrument calibration properly done then the Malvern particle sizing data is 'correctly' comparable with any other sizing technique. 1.0 INTRODUCTION One of the instrument used widely in sizing particle is the Malvern which based on laser diffraction technique. It was commercially available in 1976 as a result of a theoretical development by Swithenbank and co workers. It is widely used in many industrial applications especially in combustion fuel spray, agriculture and chemical works. Although received well in routine sizing work, however it has many limitations and weakness as faced by any other optical techniques such as visibility, intensity or phase shift methods. Before 1984 (and seriously before 1986), its application totally overlooked the 'vignetting' effect which led to a smaller size particle distribution than the actual distribution. This article is to present the .development that traces the problems