Abstract
Non-restrictive, electrostatic methods have been used for measuring solids concentration of pneumatically conveyed solids under ‘lean-phase’ conditions. The passive measurement is based on the phenomena that, during pneumatic transportation, the solids particles can become naturally charged due to particle-particle interaction, particle-pipe wall impact, friction between particles and the air stream etc. The charges can be measured and, under certain conditions, can be used as an indication of the level of solids concentration. This method has been observed experimentally [1], [2] [3] [4] [9] and confirmed on full-scale power plant by the authors [5]. Several attempts have been made to derive a theoretical relationship between the solids concentration and the resultant charge, for example Gajewski [3] and Masuda [6].
This paper further develops a relationship between the solids concentration and the charges carried by flowing solids particles after making certain limiting assumptions. The solids generate stochastic signals on the electrodes and this is expressed mathematically and related to the charge level. This theory is shortly to be tested on pneumatically conveyed solids as part of a European funded research project at Nottingham university and at Kingsnorth power station in the U.K. [7]. A method of measuring average particle size is also proposed using a combination of measuring techniques.
