Conveying Caustic or Acidic Chemical Powders

Most corrosives are either acids or bases. Corrosives are materials that can attack and chemically destroy the metal and other materials used to fabricate conveying equipment, as well as cause significant harm to personnel and the environment. Due to their hazardous and corrosive nature, conveying caustic or acidic chemical powders is both a critical and severe service application.

The word “caustic” is often used as a synonym for chemicals that are either alkaline (basic) or acidic in nature. However, the term “caustic”properly refers only to strong bases, particularly alkalis, and not to acids, oxidizers, or other non-alkaline corrosives. In this blog we look at the challenges associated with conveying chemical powders that are either basic (caustic) or acidic in nature.

Caustic chemicals include alkalis such as sodium hydroxide (powder and flakes), potassium hydroxide, and calcium hydroxide. Acidic chemicals include acid compounds and salts. Examples of acidic chemicals include citric acid and boric acid, in powdered or crystalline form. Acid salts, which produce an acidic solution after being dissolved in a solvent, include compounds such as sodium bisulphate, sodium bicarbonate, and others. Caustic and acidic chemicals, in powder, granular, crystalline or flake form, are often found in a variety of industrial and food processing applications.

CONVEYING CAUSTIC OR ACIDIC CHEMICAL POWDERS: CHALLENGES

Chemical powders which are caustic or acidic in nature are corrosive. Corrosive substances destroy other substances and materials with which they come into contact. When these substances are conveyed, corrosion of the conveying equipment can occur due to direct contact with the material or the deposition of fines. The resulting corrosion can degrade or destroy the equipment, necessitating repair or replacement of failed parts and components. In the worst cases, outright replacement of the equipment may be required.

Because conveying equipment can be degraded or destroyed by corrosive substances, it is important to use equipment which is capable of resisting the chemical attack. This will require giving careful consideration to the materials that are used in the conveyor’s construction, as well as the overall design which can serve to limit the chemical contact.

Another important challenge to be surmounted when conveying caustic or acidic chemicals is the need for safety of personnel and the environment. When conveyed, fugitive emissions of caustic or acidic powders can be released which can prove harmful or irritating to personnel. Spills of caustic or acidic powders can create corrosive hazards which require cleanup and disposal. For these reasons, caustic or acidic powders are best conveyed with equipment which fully contains the material and prevents spillage or the release of fugitive emissions.

CONVEYING CAUSTIC OR ACIDIC CHEMICAL POWDERS: SOLUTIONS

For applications involving conveying caustic or acidic chemical powders, UniTrak often recommends the following equipment solutions:

• TipTrak™ Monocoque continuous bucket elevators. A preferred choice for safely conveying hazardous chemical powders at rates up to 2400 cubic feet per hour. TipTrak™ Monocoque elevators feature fully sealed gastight construction. Fully interlocking buckets eliminate spillage and a variety of options are available, including fully conductive drive assemblies, explosion proof drive motors, and more. For handling caustic or acidic powders, corrosion-resistant rubber beltchains and running components, as well as stainless steel frames or corrosion-resistant paint finishes are available.
• TipTrak™ PEC continuous bucket elevators. Fully enclosed elevators that safely contain caustic or acidic powders. Fully interlocking buckets eliminate spillage. For handling caustic or acidic powders, corrosion-resistant rubber beltchains and running components, as well as stainless steel frames or corrosion-resistant paint finishes are available.
• Powderflight aeromechanical conveyors. Operating on the principle of a high-velocity airstream, these conveyors can move significant quantities of powdered material. The fully enclosed tube prevents dusting, and material can be conveyed at any angle from 0 to 90 degrees. Powderflight aeromechanical conveyors can be connected to and fed from a variety of sources, including bins, hoppers and silos, mixers and blenders, and bulk bag dischargers and fillers.
• UniFlex flexible screw conveyors. An economical conveying solution that is ideal for batch-style production. With a simple design and dust-free operation, flexible screw conveyors can handle a variety of powders, granules, and flakes.

If your application involves the conveying of caustic or acidic chemical powders, UniTrak has proven equipment solutions that can help. To find out more about our equipment lineup, please contact our sales team directly.