Sustainable conversion of citrus peel waste

Patent metadata

Field	Value
Publication number	US-9253996-B2
Application number	US-201213660254-A
Country	US
Kind code	B2
Filing date	Oct 25, 2012
Priority date	Oct 26, 2011
Publication date	Feb 9, 2016
Grant date	Feb 9, 2016

Abstract

A sustainable method and system for producing bio-fuels from citrus peels and the recovery of limonene and pectin prior to fermentation of the peel solids. In one embodiment a sustainable method and system for the concurrent recovery of limonene and pectin from citrus peels is disclosed. The peels are optionally zested, mixed with water and an acid, and then exploded in a jet cooker or a pressurized extruder. The exploded peels are transferred to a flash vessel where the remaining limonene and water vapor are separated into water and limonene. The pectin fraction is removed from the flash tank and extracted by centrifuge, precipitation and/or filtration. The remaining peel solids are fermented in an anaerobic digester which produces methane, ethanol, acids, CO 2 or other end products which can be used as fuel for power generation equipment sufficient to supply the processing system for sustainable operations as described herein.

First claim

We claim:

1. A method of recovering pectin from citrus peels comprising:
removing the zest from the citrus peels;
mixing the citrus peel with water to form a citrus peel slurry;
adjusting the pH of the citrus peel slurry with an acid in a mixing feed tank;
heating the citrus peel slurry in the mixing feed tank;
pumping the heated citrus peel slurry to a pressure cook vessel;
exposing the citrus peel slurry in the pressure cook vessel to pressurized steam to substantially elevate the temperature of the citrus peel slurry resulting in the formation of a vapor containing a limonene fraction and a water fraction, a solubilized pectin liquor fraction, and a substantially de-oiled citrus peel fraction, wherein the citrus peel slurry residence time within the pressure cook vessel is from about one to about twenty minutes;
separating the substantially solubilized pectin fraction from the substantially de-oiled citrus peel fraction prior to any fermentation, hydrolyzation, digestion or drying of the substantially de-oiled citrus peel fraction; and,
recovering a substantial amount of pectin from the solubilized pectin liquor.

2. The method of claim 1 further comprising venting the vapor containing limonene oil and water to an unpressurized flash vessel.

3. The method of claim 2 further comprising separating the limonene oil and water fractions from the vapor in a condensate tank.

4. The method of claim 1 wherein the citrus peel feedstock is substantially rinsed prior to being exposed to pressurized steam.

5. The method of claim 1 wherein the citrus peels are preheated to a temperature of about 35 to about 70 degrees Celsius.

6. The method of claim 1 wherein the citrus peel slurry is heated with steam to a temperature of about 100 to about 135 degrees Celsius.

7. The method of claim 1 wherein the citrus peel slurry is heated under pressure of about 10 psig to about 100 psig.

8. The method of claim 1 wherein the citrus peel slurry residence time within the pressure cook vessel is up to about 11 minutes.

9. The method of claim 1 wherein the substantially de-oiled citrus peels are anaerobically fermented.

10. The method of claim 1 wherein the pressure cook vessel includes an extruder mechanism whereby the citrus peels are further ground into smaller particle sizes while being heated under elevated pressure.

11. The method of claim 1 comprising the steps of transferring the heated citrus peels of the citrus peel slurry from the pressure cook vessel to a first centrifuge and mixing the heated citrus peels with water to separate into peel solids and soluble pectin.

12. The method of claim 11 comprising the steps of transferring the peel solids to a second centrifuge and mixing with water for additional dewatering and pectin recovery.

13. The method of claim 11 comprising the step of transferring from the first centrifuge to an evaporator to produce a more concentrated pectin solution.

14. The method of claim 13 comprising the step of routing the concentrated pectin solution to a precipitation unit where it is mixed with a precipitating agent to precipitate pectin from the concentrated solution.

15. The method of claim 1 wherein 8% pectin solution is recovered.

Assignees

• Godfroid Robert
• Palta Deepali
• Narayan-Sarathy Sridevi
• Small Ii William B
• Frito Lay North America Inc

Inventors

• Godfroid Robert
• Palta Deepali
• Narayan-Sarathy Sridevi
• Small Ii William B

Classifications

• C12P5/023

  Methane · CPC title

• A23L19/07 Primary

  Fruit waste products, e.g. from citrus peel or seeds · CPC title

• C11B9/027

  Recovery of volatiles by distillation or stripping · CPC title

• C12P7/10

  substrate containing cellulosic material · CPC title

• A23K50/10

  for ruminants · CPC title