Dear RogerH,
We have two sources of feed: one is napthenic caustic and another one is phenolic. For the naphthenic caustic the unit runs very smoothly. But when we swing to phenolic processing, piping gets clogged. We did flushing with water and found a lot of black solid material look like iron salts. We didnot analyse the salts, but I think almost of them should be sodium salts so they should be well dissolved in water.
Temperature may also the cause. Original design temperature is about 60oC, but now we're operating at 40oC only.
Because my plant is quite new, do you think the dirt inside pipeline due to bad flushing during commissioning stage is the concern?