Effect of temperature
Two sets of experiments, using different amounts of coagulant salt, were carried out to study the effect of temperature on the bed performance.
Slight changes in oil removal were found, although the best performance seemed to be achieved at the intermediate temperature (40 ◦C), as shown in Fig. 6.
However,the pressure drop across the filter had a different behaviour, as
shown in Fig. 7.
An exponential increase in pressure drop was observed at high temperatures and for small contents of calcium sulphate.
High temperatures usually enhance coalescence, due to the lower fluid viscosity and the rise in the number of collisions between droplets, since their mobility is increased.
But, likewise, the probability for a droplet to be entrapped is reduced. An increase in temperature also leads to a less favourable adsorption equilibrium.
The lack of coagulant salt and high temperatures increases the oil droplet residence time in the bed, and hence coalescence and layer clogging are also favoured.