Application of electrostatic precipitation to dust control in the cotton industry

This report describes a programme of work aimed at developing a method of controlling the rate of release of dust from one particular cotton textiles operation, the “”Beaming”” process. The system is based on the use of Electrostatic Precipitation (ESP) of dust and can be regarded as an alternative to local exhaust ventilation.An initial report (Jones 1989) was prepared, as part of this study, reviewing current dust control techniques and outlining possible areas of application of electrostatic precipitation. This in included here as Appendix 1.This phase of the programme was followed by a series of studies program (i) investigations development, (ii) investigations involving a factor “”mock-up”” up1 and (iii) production and testing of a prototype module.Initial laboratory studies were carried out on a small simulated device to investigate the potential efficiency of a full scale system, and to determine the relative importance of the various parameters involved.The potential efficiency of particle charging was determined in relation to the rate of production of “”space charge”” by electrodes of differing configurations. The system chosen for the final application comprises a braided carbon fibre string. This combines an efficient source of air ionisation with a low rate of production of hazardous ozone.Tests were carried out relating dust collection efficiency to the following parameters (i) air flow through the device, (ii) electrical potential and polarity of the dust charging system, (iii) electrical potential and polarity of the dust collection system, (iv) dust particle size, (v) physical construction and size of the device.The method of assessment was by comparison of the airborne concentration of particles penetrating the device when no potential was applied to that with the voltage switched on.This exercise assisted in the design of a laboratory equivalent of the envisaged prototype on which a similar series of tests was carried out. A full scale mock-up of the housing for the envisaged prototype was also assembled and used in the factory to assess the nature of the airflow through the device, and to evaluate any ergonomic problems resulting from its introduction.Finally, a full scale prototype unit has been installed in the factory and its performance assessed. Results are presented of an evaluation of its efficiency in dust control, and of any related ergonomic problems.Several ergonomic problems were encountered and all except one satisfactory resolved. The one outstanding difficulty was considered not to be serious.Measurement of airborne particle are in the vicinity of the machine generator indicated a 25% reduction in exposure to inhalable dust due to the introduction of the control unit. Means of improving on its figure, primarilyiby re-siting-the unit are considered.The design and operation of a novel cleaning system is discussed. This system operated efficiently and without the need for maintenance throughout the factory trials.It is concluded that the study has been successful in producing a safe, low maintenance device which could be operated in to factory with minimal production interference, and other significant improvements could be possible with better siting and more retention to air flow capture. “”