Design and implementation of biodiesel washing automation system with set of sensors and programmable logic controller device

Biodiesel washing is part of a biodiesel production process that aims to remove impurities contained in biodiesel. In this research, the process of biodiesel washing was conducted at a liquid separation mini plant using mechanical stirring method. A capacitive sensor was utilized to detect interface which is used in the separation between the two liquids, biodiesel and water. This sensor acts as a substitute for the operator who does visual observation in liquid separation. The temperature and the level of water and mixture in the mixing tank to make the process run optimally was also constantly controlled. The process of washing or purification was carried out with 3 times iteration. Programmable logic controller (PLC) was used as a controller device that serves to detect the sensor readings and operate the pumps and valves in this biodiesel washing process. The water mixing process was tested by mixing water temperature ranging from 70°C to 75°C with 25°C water for 2 times to get the water temperature of ± 55°C. The capacitive sensor module was able to differentiate water from biodiesel. The module produced 58.2 - 84.5 kHz voltage signal when detecting water and 84.5 - 98.8 kHz voltage signal when detecting biodiesel in static condition. The time delay for the transfer from water discharge valve to biodiesel discharge valve is 12 seconds. The overall, biodiesel washing automation system can be operated in ± 18 minutes duration for one washing cycle (excluding the duration of the water heating).