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Recovery of Caustic and Acids in the Dairy Industry

Recovery of Caustic and Acids in the Dairy Industry

Overview

Dairy production equipment such as pipe lines and evaporators must be cleaned periodically to maintain high hygienic standards and to ensure proper functioning of the equipment.

The cleaning and sterilization of dairy equipment is done typically with hot solution of 2% caustic (NaOH). The hot caustic disinfects the equipment and removes caramelized organics, precipitated proteins, and fats from the surfaces of tanks, pipes, heat exchangers and evaporators. In some cases, additional chemicals, such as antifoams and chelating agents, are also added. The spent caustic solution is heavily contaminated with dispersed and soluble organics. Acid cleaning cycles are also done to remove scale from production equipment and piping. Nitric acid, phosphoric acid, or a blend of different acids is most commonly used.

Caustics and acids used in dairies for cleaning are expensive and environmentally hazardous. Neutralization and disposal of caustic and acid solutions is becoming a less acceptable practice. Rising chemical costs also make recovery and reuse of these solutions an attractive alternative.

The Challenge

To recover expensive acid and caustic from clean-in-place (CIP) streams, and comply with increasingly stringent regulatory requirements.

The Solution

Membrane technology can be used in the dairy industry to recover the expensive caustic solutions used to clean process equipment. Membranes clarify the cleaning solution to remove suspended and dissolved solids, and the treated solutions can be reused within the plant.

Koch Membrane Systems (KMS) offers the SelRO® line of chemically stable nanofiltration (NF) membranes for caustic and acid streams. SelRO membranes are the preferred choice in settings where temperature and pH are especially challenging.

The SelRO Caustic Recovery System, using SelRO MPS-34 membranes, offers a total solution for recycling spent caustic and acids. The system removes low molecular weight organic matter and inorganic contaminants, from acids, recovering up to 90% of these valuable chemicals while reducing waste treatment costs. The SelRO Caustic Recovery System achieves cost savings, reduced effluent volumes and fees, and smooth production.

Users of SelRO membranes in CIP systems also benefit from improved productivity. Higher quality caustic and acids are readily available in the CIP tanks at all times. Their cleaning effectiveness is greater, foaming does not occur, and thermophilic bacteria are constantly being removed by the tight NF membranes. The use of chemical additives can be reduced significantly.

The SelRO Caustic Recovery System

The SelRO Caustic Recovery system is designed to remove the suspended and dissolved substances from spent caustic or acid. More than 90% of the brown-burnt colored contaminants and COD are removed from the treated cleaning solution (caustic or acid), accompanied with substantial reduction of calcium and carbonates (ineffective alkalinity).

In the membrane process the spent solution is separated to two streams:

Permeate: Consists of the high quality caustic or acid (over 90% of the original spent solution volume). This stream is continuously recycled to the CIP tank.

Concentrate: Concentrated organic material, (less than 10% of the original volume). This stream can be diafiltered to remove excess alkalinity and used as an animal food additive.

Installation: The membrane system can be installed either as an add-on to the caustic or acid CIP tank (kidney mode), or operate in batch mode in single use cases.

Membranes: The membranes used in the system are chemically stable spiral wound SelRO MPS-34 nanofiltration membranes. All the other materials used in the SelRO system, besides membranes, were chosen for compatibility with acid or caustic environments, at high temperature conditions.

MPS-34 membranes have long term stability in phosphoric acid, nitric acid, sodium hydroxide and potassium hydroxide, at concentrations of 2-20%. Typical membrane life in dairy caustic recovery applications is 1-2 years. Membrane life in nitric or phosphoric acid is typically 2-3 years.