Soil cleaning from PAH

Project in collaboration with GKSS-Forschungszentrum Geesthacht GmbH .

Polluted soil with PAH is extremally poisonous for living organisms and human lifes. Such polluted soil remains, e.g., after militar or industrial activities. For this reason, a reactor for cleaning of dust was constructed in GKSS (see figure below). Dust consists 30 % of dry phase (soil and PAH) and 70 % water. The dry phase contains 0.1-10 % oil and 0.5 % PAH.

principal scheme of PAH cleaning reactor

The characteristic distribution of diameter of soil particles. Measured by laser scattering technique using HORIBA LA-910. The blue curve is distribution of to soil particles before entering into the reactor, while red - after leaving the reactor tube. Mean diameter of soil before reactor is 17.8 mm, and after - only 6.6 mm. We can interpret it as soil particles disintegrates into parts during evaporation in the reactor. distribution of soil diameter before and after reactor

Some basic data of PAH can be obtained from . The PAH molecules consist of or more benzole rings. In general, the boiling temperature is higher for molecules with higher molecular weight. The cleaning efficiency for PAH with higher boiling temperature is much lower. The melting temperature for more masive PAH molecules is higher than of boiling temperature of water.
name formula mol. weight   boil. temp.
pyrene C16H10 202.25 pyrene 360 C
naphtalene C10H8 128.17 naphtalene 218 C
benzo[a]pyrene C20H12 252.31 benzo[a]pyrene 495 C
anthracene C14H10 178.23 anthracene 340 C
acenaphthene C12H10 154.21 acenaphthene 279 C
chrysene C18H12 228.29 chrysene 448 C

Spraying process. Soil particle is coated with layer of water. Water starts to evaporate at the entering of the reactor. Therefore, the radius of the dust droplet monotonously decreases. Characteristic evaporation time for particles with 100 mm diameter is approximately a second. The evaporation time decreases parabolicaly for particles with smaller diameter. spraying after pipe

Page compiled by Vilnis Frishfelds. Last update: 03.08.00.