Electrostatic Liquid Spraying

During the 1870s Rayleigh pioneered work on the breakup of liquid jets and on the phenomenon of the instability of charged liquid droplets. As early as 1944 an electrostatic droplet spray scrubber consisting of electrically charged water droplets collecting aerosol particles charged to the opposite polarity was proposed by Penney. He reported an increase in the dust collection efficiency of particles by droplets with that scrubber.

With the development of science and technology, many scientific research fields intersect. Those dealing with charged macroscopic particles and water droplets have recognized that many of these same ideas apply to such diverse problems as electrostatic paint spraying, combustion, ink-jet, rocket propulsion, fog cleaning, agricultural chemicals spraying and surface coating. Many kinds of devices with electrostatic charger have been developed and used in practice.

While there are a number of ways of charging particles, only three main charging mechanisms are applicable to liquids. These are, corona charging (ion bombardment), contact charging and induction charging. Commercially available electrostatic liquid spraying devices are in printing and paint spraying industries, and are using contact and/or ionization charging processes. To make the charged droplets effective in application, the charge or charge-to-mass ratio of droplets is necessary to be adequately high, and the number of charged droplets with the right sizes is also necessary to be large enough. However, most of the current approaches and devices are not able to satisfy these two requirements. For example, those termed as "electrospray", or as "electrohydrodynamic spraying" where the electric field itself is the cause of the atomization of a liquid into fine droplets, produce a very small number of charged droplets. For those commercially available electrostatic liquid spraying devices such as printing and paint spraying, both the contact and the ionization charging processes are utilizing very high voltages or high energies to charge the droplets. The mechanical components are unsafe, unreliable, expensive, and/or not amenable to scaling.

 Through more than 20 years of continuous study and development of the Billinton Group's scientists and engineers, three spraying methods, i.e. pneumatic, hydrostatic and centrifugal, are combined with induction charging mechanisms to produce highly charged droplets with small energy or low voltages but safe handling devices, applying to various areas as 

• Agricultural chemicals spraying;
• Oil mist elimination;
• Dust control, particularly those particles with sizes under 3 µm;
• FGD (Flue gas desulphurization).