Ultrasonics for Biodiesel Processing

Today, biodiesel is primarily produced in batch reactors. Ultrasonic biodiesel processing allows for the continuous inline processing. Ultrasonication can achieve a biodiesel yield in excess of 99%. Ultrasonic reactors reduce the processing time from the conventional 1 to 4 hour batch processing to less than 30 seconds. More important, ultrasonication reduces the separation time from 5 to 10 hours (using conventional agitation) to less than 60 minutes. The ultrasonication does also help to decrease to amount of catalyst required by up to 50% due to the increased chemical activity in the presence of cavitation (see also sonochemistry). When using ultrasonication the amount of excess methanol required is reduced, too. Another benefit is the resulting increase in the purity of the glycerin.

Ultrasonic processing of biodiesel involves the following steps: 

1. the vegetable oil or animal fat is being mixed with the methanol (which makes methyl esters) or ethanol (for ethyl esters) and sodium or potassium methoxide or hydroxide 

2. the mix is heated, e.g. to temperatures between 45 and 65degC 

3. the heated mix is being sonicated inline for 5 to 15 seconds 

4. glycerin drops out or is separated using centrifuges 

5. the converted biodiesel is washed with water 

Most commonly, the sonication is performed at an elevated pressure (1 to 3bar, gauge pressure) using a feed pump and an adjustable back-pressure valve next to the flow cell.

Costs of Ultrasonic Biodiesel Manufacturing:

Ultrasonication is an effective means to increase the reaction speed and conversion rate in the commercial biodiesel processing. Ultrasonic processing costs result mainly from the investment for ultrasonic equipment, utility costs and maintenance. The outstanding energy efficiency (click chart to the right) of Altrasonic ultrasonic devices helps to reduce the utility costs and by this to make this process even greener. The resulting costs for the ultrasonication vary between 0.1ct and 1.0ct per liter (0.4ct to 1.9ct/gallon) when used in commercial scale. Read more information about ultrasonic processing costs.