Working of Bio-Diesel production plant

These are the steps involved in production of Biodiesel from Jatropha.

 

1. In the first step Jatropha seeds are treated with hot steam at around 60 to 70 °C which helps in better oil extraction. Oil from seeds is extracted using a mechanical extraction process (crushing). Jatropha seeds contain 35 to 40 % oil by mass and by crushing 28 to 30 % oil is recovered. Which is then allowed to settle in a sediment tank. The By-Product of this step is Jatropha cake which contains 5-7 % oil. This By-Product can be used as fertilizer or it can be used for burning.
2. In the next step extracted oil is filtered through a filter-press.
3. In the next step filtered oil is treated with 5 N solution of NaOH to remove free fatty acid (600 gm of NaOH in 3 lit of water for 125 kg of oil). The neutralized reaction takes 15 minutes with proper stirring. The result of neutralized reaction is soap formation.
4. In the next step oil is separated from soap by sucking the oil through a vacuum pump.
5. In the next step methoxide is produced using methanol and KOH for transesterification process. Around 50 kg of methoxide for 265 kg of oil.
6. The next step is transesterification where methoxide is mixed with oil to produced methyl ester (Biodiesel) and glycerol. The reaction takes around 2 hours to complete. Agitation is provided throughout the reaction. A successful reaction produces two liquid phases: ester and crude glycerol. Crude glycerol, the heavier liquid will collect at the bottom after several hours of settling. After the transesterification reaction, one must wait for the glycerol to settle to the bottom of the container. This happens because Glycerol is heavier then biodiesel. The settling will begin immediately, but the mixture should be left a minimum of eight hour (preferably 12) to make sure all of the Glycerol has settled out. The Glycerol volume should be approximately 20% of the original oil volume.

7. In the next step methyl ester is treated with water for 2 hours. The amount of wash water should equal the amount of oil, and can be drained throughout the washing process.  After this water is separated by gravity separation. After the water is drained, the air washing process can start. At this point, the biodiesel is usually a pale yellow color. Air should be bubbled through the biodiesel mixture for approximately 8 hours. The bubbling should be just enough to agitate the biodiesel surface. A final drain of accumulated contaminants is done immediately after the air bubble wash is finished. The fuel is now ready for use.
8. The By-product of step 6 is used to get crude glycerin. Methanol is separated from glycerol by vacuum distillation process. After methanol removal glycerol is neutralized with H₂SO₄. This neutralized reaction results in two products first is water which contains glycerin and K₂SO₄. And second product is acidic oil (FFA).
9. The mixture of water, glycerin and K₂SO₄ is then evaporated to get K₂SO₄ crystals which can be used as fertilizer for soils low in potassium. At the end of this process we get refined glycerin (65%) which goes through a process of distillation to get distilled glycerin (85%).

 

 

Plant capacity: One M. T. of Jatropha seeds yields 275 lit of Biodiesel, 40-45 kg of soap, 7-9 kg of K₂SO_4, 20 kg of glycerin and about 14 kg of Methanol is recovered.

The inputs are 1.5 kg of NaOH, 50 Kg of Methanol and about 2.5 kg of KOH.