we carefully analyzed
one of the wet scrubbers which had the highest performance in capturing particles at that
time. Prior to our model simulation, we asked the company’s engineers why their
product works better than other companies’ products, and what mechanism they use to
capture fine paint particles of diameter 20 micron. Their explanation was that when air
flow carrying the over-spray paint particles hits a water pool, paint particles will
penetrate to the water, mix with water, and be captured by water, but air escapes.
We used our model to simulate the capturing efficiency by the company’s suggested
mechanism, but failed. During that process, our computer model showed a very
interesting vortex flow where particles are circulating along the circulation at a least
expected location. We carefully analyzed this motion and conducted further calculations
that confirmed a newly found vortex mechanism to be very effective in capturing fine
paint particles.
As the next step, we considered what might be the best geometry and shape to
enhance vortex while minimizing energy to operate the system. Engineers’ creative
minds played an important role in this process. We paid attention to a desert where an
interaction of wind and fine sand particles creates a special 3-D shape, known as a sand
dune. This 3-D crescent shape structure can easily stand against desert storm winds of
over 30 m/s. Since each sand particles are not bonded, sand particles would be blown
away under a strong wind. Why can the sand dune shape stand against a strong wind?
Figure 5 shows a cross section of the sand dune where the wind blows from left to right.
Behind the crescent shape dune, there is a strong circulation which traps the otherwise
blown away sand particles, protecting the dune from erosion and also significantly
reducing the drag force of air that flows over the dune because the circulation acts as a
bearing. The sand dune shape would be most ideal for capturing small particles with
lowest energy consumption