Working Principle of an Ethanol Distillation Plant

An ethanol distillation plant is designed to produce ethanol by separating it from a fermented mixture. Ethanol is commonly produced from biomass feedstocks like sugarcane, corn, or other carbohydrate-rich materials through fermentation, followed by distillation and dehydration to achieve the desired purity.

Basic Steps in Ethanol Production:

1. Fermentation:

• The feedstock (e.g., corn, sugarcane) is broken down into sugars, which are then fermented by yeast or other microorganisms to produce ethanol and carbon dioxide.

2. Distillation:

• The fermented mixture, known as the beer or wash, typically contains about 10-15% ethanol. It is fed into a distillation column where it is heated, causing the ethanol to vaporize and separate from the water and other components.
• The vaporized ethanol rises through the column and is collected, while the water and other impurities remain in the liquid phase and are removed from the bottom of the column.

3. Dehydration:

• The distillate from the distillation process usually contains around 95-96% ethanol and 4-5% water. To achieve anhydrous ethanol (99.5% or higher), the distillate undergoes a dehydration process, commonly using molecular sieves or azeotropic distillation to remove the remaining water.

4. Product Collection:

• The purified ethanol is collected and stored in tanks, ready for distribution and use in various applications such as fuel, beverages, or industrial solvents.

Equipment Required

1. Fermentation Tanks:

• Large vessels where the feedstock is mixed with water, enzymes, and yeast to convert sugars into ethanol and carbon dioxide.

2. Distillation Columns:

• Beer Stripper Column: Separates most of the ethanol from the water and other components.
• Rectification Column: Further purifies the ethanol to increase its concentration.

3. Reboilers:

• Provide heat to the distillation columns, causing the ethanol to vaporize.

4. Condensers:

Cool the vaporized ethanol, converting it back into a liquid form.

5. Dehydration Unit:

• Molecular Sieves: Use porous materials to selectively adsorb water molecules, leaving behind anhydrous ethanol.
• Azeotropic Distillation: Utilizes an additional substance (such as benzene) to break the ethanol-water azeotrope and remove water.

6. Heat Exchangers:

• Preheat the fermented mixture before it enters the distillation column by recovering heat from outgoing streams.

7. Pumps and Piping:

• Circulate the liquid streams through the plant, including feeding the fermentation mixture into the distillation column and transferring the ethanol between units.

8. Storage Tanks:

• Hold the feedstock, the fermented mixture, and the final ethanol product.

9. Control Systems:

• Automated systems that monitor and regulate the temperature, pressure, flow rates, and other critical parameters to ensure efficient operation.

Process Flow Diagram (PFD)

Here’s a basic outline of the ethanol distillation process:

1. Feedstock Preparation:

• The feedstock (e.g., corn, sugarcane) is processed to extract fermentable sugars.

2. Fermentation:

• The sugars are mixed with water and yeast in fermentation tanks, producing a mixture with ethanol content of around 10-15%.

3. Distillation:

• Stripper Column: The fermented mixture is fed into the stripper column where ethanol is vaporized and separated from the majority of the water and solids.
• Rectification Column: The ethanol-rich vapor is further purified in the rectification column to increase its concentration.

4. Dehydration:

• The 95-96% ethanol distillate is sent to a dehydration unit (e.g., molecular sieves) to remove the remaining water and produce anhydrous ethanol.

5. Product Collection:

• The anhydrous ethanol is collected in storage tanks, ready for distribution.

6. Waste Management:

• The waste from the distillation process, including stillage (solid by-products), is typically processed for further use, such as animal feed or biogas production