Neutralization Tanks in Glycerol Treatment

Glycerol, a by-product of biodiesel production through transesterification, initially comes out as a crude product containing various impurities. Among these impurities are soaps, catalyst residues, and free fatty acids, which can make the glycerol acidic or basic. Neutralization tanks play a critical role in treating this glycerol to achieve a neutral pH, ensuring its quality and further refining it for various applications.

The Role of Neutralization in Glycerol Treatment

  • pH Regulation: The primary purpose of the neutralization tank is to bring the pH of crude glycerol to a neutral level, usually close to 7. This ensures that the glycerol is free from residual acidity or alkalinity.
  • Soap Removal: Soaps present in the glycerol can be neutralized and separated out, improving the glycerol’s purity.
  • Protection of Downstream Equipment: Neutralizing the pH of glycerol can prevent corrosion and damage to subsequent processing equipment.

Neutralization Process Steps

  • pH Testing: Before neutralization, the pH of the crude glycerol is tested to determine its current state – whether it’s acidic, neutral, or alkaline.
  • Addition of Neutralizing Agent: Depending on the pH test results:
    • If glycerol is acidic, a base (like caustic soda or sodium hydroxide) is added.
    • If glycerol is alkaline, an acid (like sulfuric acid) is introduced.
  • Mixing: After the addition of the neutralizing agent, the mixture is thoroughly stirred to ensure complete neutralization.
  • Settling: Once neutralization is complete, the mixture is allowed to settle. Neutralized soaps and other impurities will either float to the surface or settle at the bottom, depending on their density.
  • Separation: The neutralized impurities are then separated from the glycerol, typically using a decanter or separator.

Equipment Considerations for Neutralization Tanks

  • Material: The tanks should be made of corrosion-resistant materials like stainless steel, especially given the potential for pH fluctuations and the use of acids or bases.
  • Agitation: A mechanical agitator is essential for thorough mixing of the neutralizing agents with the glycerol.
  • pH Monitoring: Modern neutralization tanks may be equipped with continuous pH monitoring systems to provide real-time data and automate the addition of neutralizing agents.
  • Temperature Control: Some neutralization processes may require the glycerol to be at a specific temperature, necessitating heating or cooling coils in the tank.

Advantages of Glycerol Neutralization

  • Improved Purity: Neutralization helps in removing soaps and other pH-sensitive impurities from the glycerol.
  • Enhanced Market Value: Neutralized and purified glycerol can be sold at a higher price in the market.
  • Versatility in Use: Neutral glycerol can be further refined for a variety of applications, from industrial solvents to food and pharmaceuticals.


Neutralization tanks are pivotal in the glycerol refining process, ensuring that the by-product of biodiesel production is of high quality and free from unwanted acidic or basic components. The proper and efficient neutralization of glycerol sets the stage for its subsequent purification and use in a myriad of applications.