Various types of precipitators are commonly used in industry and research laboratories for removal of aerosol particles from gas carriers. Three main types exist: gravimetric, electrostatic, and thermophoretic precipitator (TP). The first two are mainly used for air quality control purposes. TP could be employed as a particle sampler for following analysis of size, shape, morphology, and chemical composition of collected materials.
The TP’s operation principle is based on passage of an aerosol stream through a narrow slot between hot and cold plates. An aerosol particle in that stream experiences a thermal force in the direction of decreasing temperature. The magnitude of the force depends on the gas and particle properties as well as the magnitude of the temperature gradient between the two plates.
Lucija Boskovic and Igor E. Agranovski, Griffith School of Engineering, Queensland, Australia, developed a new TP precipitator for representative and efficient collection of aerosol particles from the ambient air and technological pipelines.
The device consists of hot and cold plates (5 x 5 cm2) capable of operation at temperature gradients ranging from 20 000 to 100 000 K/m. A gas sample is made to pass through a 1-mm slot between the plates at a flow rate of up to 1.5 L/min. This makes the device suitable for operation in conjunction with common aerosol instruments including differential mobility analyzer (DMA) and diffusion batteries with similar operational flow rates.
The efficiency of the device was highest for the lowest gas flow rate used (0.3 L/min) reaching a level of above 99 %. The efficiency was decreased reaching its minimal values at the highest flow rate investigated (1.5 L/min). However, even here, the average efficiency for removal of particle smaller than 60 nm was around 50 %.
- A New Thermophoretic Precipitator for Off-Line Particle Analysis,
Lucija Boskovic, Igor E. Agranovski,
Clean Soil Air Water 2012, 40 (6), 565–570.