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Bericht des silikose-forschungsinstituts der bergbau berufsgenossenschaft
J. Aerosol S,i.. 1976, VoL 7, p. 436. Pergamon Press. Printed in Great Britain.
REPORT Berieht des Silikose-Forsehungsinstituts der Bergbau Berufsgenossenschaft. 1974. pp. 126, 463, Bochum, Hunscheidstrasse 18, Germany. The 1973 report of the Silicosis Research Institute was reviewed in J. Aerosol Sci. 6, 274. In the current report, experiments are described on dust extraction from coal cutting machines. A combination of blowing and sucking is used, the latter flow being five times the former. Blown air is induced to cling to the surface of the machine by the Coanda effect which ensures high efficiency of entrainment. A new recording gravimetric sampler for fine dust is described, M P G If. The mine air is sucked at a constant rate of 4 1/min through a horizontal elutriator and a filter. The pressure drop across the filter is claimed to be proportional to the amount of dust collected on it, 15 20 mg of dust per 100 mbar pressure loss; for very low concentrations special filters are available which give 0 . 5 1.0 m g per 100 mbar. A comparison was carried out between healthy young miners and patients with chronic obstructive diseases of the airways. Each group was exposed first to aerosol of acetyl choline and minutes later to 6-8 ppm sulphur dioxide. Airway resistance and intra thoracic gas volume were measured by body plethysmograph. The healthy men reacted strongly to the aerosol but the SO2 had little effect; the gas, however, affected many of the patients more strongly than the aerosol. Work continues on proteolytic and antiproteolytic enzymes in relation to emphysema and on the aseptic dispersion of lung scars and spontaneous pneumothorax. There is a short s u m m a r y article on silicosis research in the Medical Division over the last 18 years, including a list of 119 published papers. The Physics Section contribute an article on inertial deposition of dust. Experiments showed that the theoretical increase of filter efficiency with rising air velocity was not realised with large particles due to their failing to adhere to the fibres. Better results were obtained by spraying oil mist into the filter along with dust; this was more effective than soaking the filter in oil because, in this case, the oil film was blown away at high velocities from the windward face of the fibre and collected on the lee side, where it did no good. Instead of oil, solutions of calcium chloride, with a wetting agent, were very effective. It was shown that the filtration of fine particles, 0.5 2.0/~m dia., was improved when coarser particles of dust were present. This was shown to be an inertial effect due to collisions between particles of different sizes. A theoretical study has been made of the effect of electric charges on nuclepore filters upon the trajectories of particles as they approach the pores. It is based on an approximation of the flow field approaching a pore into 3 zones, parallel streamlines at a distance, converging flow within an inverted parabolic region upstream of the pore and parallel flow in the pore. The Reynolds number of the pore is 0.43. Deposition by interception is indicated, Stokes numbers are 0 and 0.1 and several trajectories are shown for attracting and repelling electric forces. The electric charge on the filter is supposed to be distributed around the entrance to the pore and the particles are also supposed to be charged, induction being taken as negligible. 52 Papers were published from the Institute during the year and they are listed, with abstracts, at the end of the report. C. N. DAVIES
436
REPORT Berieht des Silikose-Forsehungsinstituts der Bergbau Berufsgenossenschaft. 1974. pp. 126, 463, Bochum, Hunscheidstrasse 18, Germany. The 1973 report of the Silicosis Research Institute was reviewed in J. Aerosol Sci. 6, 274. In the current report, experiments are described on dust extraction from coal cutting machines. A combination of blowing and sucking is used, the latter flow being five times the former. Blown air is induced to cling to the surface of the machine by the Coanda effect which ensures high efficiency of entrainment. A new recording gravimetric sampler for fine dust is described, M P G If. The mine air is sucked at a constant rate of 4 1/min through a horizontal elutriator and a filter. The pressure drop across the filter is claimed to be proportional to the amount of dust collected on it, 15 20 mg of dust per 100 mbar pressure loss; for very low concentrations special filters are available which give 0 . 5 1.0 m g per 100 mbar. A comparison was carried out between healthy young miners and patients with chronic obstructive diseases of the airways. Each group was exposed first to aerosol of acetyl choline and minutes later to 6-8 ppm sulphur dioxide. Airway resistance and intra thoracic gas volume were measured by body plethysmograph. The healthy men reacted strongly to the aerosol but the SO2 had little effect; the gas, however, affected many of the patients more strongly than the aerosol. Work continues on proteolytic and antiproteolytic enzymes in relation to emphysema and on the aseptic dispersion of lung scars and spontaneous pneumothorax. There is a short s u m m a r y article on silicosis research in the Medical Division over the last 18 years, including a list of 119 published papers. The Physics Section contribute an article on inertial deposition of dust. Experiments showed that the theoretical increase of filter efficiency with rising air velocity was not realised with large particles due to their failing to adhere to the fibres. Better results were obtained by spraying oil mist into the filter along with dust; this was more effective than soaking the filter in oil because, in this case, the oil film was blown away at high velocities from the windward face of the fibre and collected on the lee side, where it did no good. Instead of oil, solutions of calcium chloride, with a wetting agent, were very effective. It was shown that the filtration of fine particles, 0.5 2.0/~m dia., was improved when coarser particles of dust were present. This was shown to be an inertial effect due to collisions between particles of different sizes. A theoretical study has been made of the effect of electric charges on nuclepore filters upon the trajectories of particles as they approach the pores. It is based on an approximation of the flow field approaching a pore into 3 zones, parallel streamlines at a distance, converging flow within an inverted parabolic region upstream of the pore and parallel flow in the pore. The Reynolds number of the pore is 0.43. Deposition by interception is indicated, Stokes numbers are 0 and 0.1 and several trajectories are shown for attracting and repelling electric forces. The electric charge on the filter is supposed to be distributed around the entrance to the pore and the particles are also supposed to be charged, induction being taken as negligible. 52 Papers were published from the Institute during the year and they are listed, with abstracts, at the end of the report. C. N. DAVIES
436