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What has been the most challenging unit ops you’ve dealt with

March 25, 2014

Centrifugal separation of oil from coconut milk (freshly expressed from mature coconut meat) by using a disc-bowl centrifuge (Alfa Laval). As I recall, I managed to successfully perform the separation just by controlling and manipulating outlet and inlet stream pressures, flow rates, and temperature at constant rpm without any introduction of chemical intermediates (including water) to enhance separation. It was a difficult experience since I did not have data of coconut milk constituents and the physicochemical analysis. In addition to the shearing stress applied on the fluid by the centrifugal action, as I remember I used to preheat the milk at a reasonable temperature (enough not to dissipate vitamin E content) to aggravate the process of protein denaturing. Protein is the binder of oil and the other components in the coconut milk. After binder breakage, I started controlling the flow and pressure so that the interface between the light and heavy fluids would be at the optimum distance away from the disc holes. This is to facilitate the separation of light component (oil) from the heavy ones and so as to minimize wastage of the oil in the heavy fluid stream. In the end, I was able to build and to operate a virgin coconut oil processing plant. But sad to say, it was short-lived as the market was dominated by an existing more prominent company in the area of coconut oil business (in my country) than my company at that time.

Another experience I had was the operation of old (28 years old) thermal desalination evaporators (32,000 m3/day total capacity) during abnormal conditions: high conductivity, low distillate flow rate, low vacuum, etc. I still remember then we almost spent sometimes more than two hours battling with the distillate pump problems especially during lineup of distillate to the main product line going to chemical treatment plant. Also, purification of carbon dioxide coming from the generator posed a problem sometimes which led to very high pH water. We used to inject carbon dioxide to precipitate excess lime after lime injection into the water. But, sometimes the CO2 had a lot of impurities coming from the generation side and purification side (permanganate presence).

The chemical engineering subjects taken during my college days prepared me to have only the basic knowledge, but not to solve the many problems I encountered in my professional life. At least I have the idea on where to start adding to my wisdom and knowledge.

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