GB1118047A - A method of determining the particle size distribution of a dust and a device for carrying out the method - Google Patents

Abstract

1,118,047. Centrifugal separators, gas filter for particle analysis. SVENSKA FLAKTFABRIKEN, A.B. 23 Dec., 1966 [30 Dec., 1965], No. 57793/66. Headings BIT and B2P. The particle size distribution of a dust, produced in an industrial process and dispersed in a gas stream discharged from the process, is determined by withdrawing from the gas stream a partial representative stream and immediately passing it in series through two portable analytical cyclones with known efficiency curves and a filter element of known weight, after which the amounts of dust collected in the cyclones and on the filter element are weighed and the numerical values obtained are analyzed in known manner. As shown in Fig. 1, the gas sample is withdrawn from the main stream in a flue 1 by means of a probe 3 and passed via a cooling pipe 4 into cyclones 5, 7 contained in a heatinsulated casing 14, Fig. 2, within which an electric heater 18 is provided in order to maintain the gas temperature above the dew point temperature to prevent condensation in the cyclones. The latter have removable covers 16, 17 and have dust containers 6, 8 detachably secured at their lower ends. A filter is connected to the cyclone 7 and comprises a housing 9, Fig. 3, containing a filter element in the form of a sheet 31 of glass fibre supported by a net 32 and clamped between upper and lower portions 22, 26 of the housing. The upper portion is provided with a gas inlet 23, heat insulation 24 and an electric heater 25. The lower portion is provided with an orifice plate 27, a clean gas outlet 30, a thermometer 37 and pressure tappings 28, 29 connected by hoses 39, 35, Fig. 1, to a micromanometer 36. The gas outlet 30 is connected by a hose 10 to a fan 11 driven by an electric motor 12 fed through an adjustable transformer 13. At the start of a sampling operation, the gas velocity in the flue 1 is measured by a Pitot tube connected to the micromanometer 36. This determines the size of probe to be selected. The gas temperature and the dew point are measured by thermometer to decide whether use is to be made of the cooling pipe 4 or of the heaters 18 and 25. The fan 11 is then started and its speed adjusted by the transformer 13 to ensure normal gas flow through the cyclones, the flow being determined by means of the orifice plate 27 in conjunction with the micromanometer 36 and the thermometer 37. When sufficient dust has accumulated in the containers 6, 8 and on the filter element 31, sampling is discontinued and the amounts of dust collected determined and analyzed.