Abstract:
Effluent Treatment is one of the major operations in industries all over the world to
meet ever tightening environmental regulations. In this background, this project
aimed to develop an effluent densifier catering the high volume effluent output of a
palm oil mill in Galle, Sri Lanka, in order to reduce the bulk volume of effluents,
providing cost advantage for treatment processes and handling. Before any design
works, physical properties of the effluent outlet flow of the mill were measured and
it was found that the average pH value is 4.65, moisture content is 96.9%,
temperature is 70°C, and the flow rate is 2 1/s. Based on these findings, a small scale
evaporator densifier system was designed, fabricated and tested in order to observe
the functionality of the concept. The design was such that the least 30% of the water
from the incoming effluent flow to the evaporator gets evaporated to produce a
densified effluent output. The densifier was designed based on the falling film
evaporator technology and to run on waste steam available at the mill at 3.0 barg
and 134 °C. Based on the above concept, detailed fundamental calculations, and
fluid and thermal simulations were conducted in order to optimise the shape, size
and the configuration of the components of the densifier. Using the small scale
densifier, a series of lab experiments were conducted by supplying steam from a lab
scale steam generator providing above same heating conditions and varying the
effluent flow rate from 0.021/s to 0 .4 1/s. It was observed that32% to 26% of overall
evaporation can be realised by varying the effluent flow rate for a constant supply of
steam. This concept can be further improved by connecting similar densifier units
in series and also by increasing the evaporation surface area or providing additional
forced convective air flow’ over the evaporating surface.
