Description

Overview of Calcium Chloride

Calcium chloride exists in various forms depending on its hydration state and application requirements, including:

• Calcium chloride solution

• Calcium chloride hexahydrate (CaCl₂·6H₂O)

• Calcium chloride tetrahydrate (CaCl₂·4H₂O)

• Flake calcium chloride dihydrate (CaCl₂·2H₂O)

• Anhydrous calcium chloride (powder or honeycomb form)

Anhydrous calcium chloride (CaCl₂) is a high-purity, white to off-white hygroscopic solid produced through thermal dehydration of calcium chloride hydrates or solutions. Due to its strong moisture absorption capability and stable chemical properties, it is widely used in industrial, chemical, and environmental applications.

1. Desiccant

Used for drying industrial gases (e.g., nitrogen, oxygen) and organic solvents (e.g., ethanol). It is also widely applied in moisture-proof packaging and container desiccation.

2. De-icing / Anti-freezing Agent

Applied for road and airport de-icing in cold regions. It remains effective at temperatures as low as -50°C. It is also used as a concrete accelerator to improve early strength and prevent frost damage.

3. Oil and Gas Industry

Used in drilling fluids to adjust density and improve stability. It can also function as a flocculant or process additive in oil extraction operations.

4. Pharmaceutical Applications

Used in injectable calcium preparations for treating hypocalcemia and magnesium poisoning. It is also applied as an astringent and hemostatic agent in topical formulations.

5. Other Industrial Uses

Includes applications as a metallurgical flux, ceramic additive, fireproof material component, refrigeration brine medium, and soil stabilizer for improving clay compaction.

Challenges in Anhydrous Calcium Chloride Granule Production

In industrial production, drying calcium chloride, whether from dihydrate or concentrated solution to anhydrous form, presents several technical challenges due to its unique physical and thermodynamic properties:

1. Melting-like behavior during drying

Calcium chloride exhibits partial melting behavior during dehydration. As temperature increases, it approaches a eutectic-like state and dissolves in its own crystal water, leading to softening, stickiness, and severe agglomeration or lump formation.

2. High dehydration temperature requirement

The transformation from calcium chloride dihydrate to anhydrous form requires elevated temperatures of approximately 260°C. Accordingly, inlet drying air temperatures must typically exceed 260°C, and sufficient residence time is required to complete dehydration.

3. Complex heat and mass transfer behavior

Unlike conventional surface drying, calcium chloride drying involves both free water removal and bound water (crystal water) removal. This process requires overcoming lattice energy in addition to latent heat of evaporation. Therefore, accurate thermal design must consider phase transitions, enthalpy variations, and coupled heat–mass transfer behavior across temperature gradients.

Equipment Description

The anhydrous calcium chloride granule production plant is designed to convert calcium chloride solution into high-purity anhydrous calcium chloride granules through concentration, granulation, and drying processes.

The plant consists of the following main sections:

1. Multi-effect forced circulation evaporator

Concentrates calcium chloride solution to approximately 55% (depending on site conditions and feed composition).

2. Spray granulation and fluidized-bed drying system

Converts concentrated calcium chloride solution into solid granules and further dries them to approximately 94–97% anhydrous calcium chloride product.

System Advantages

1. The entire process, from calcium chloride solution concentration via multi-effect evaporation to granulation and drying via spray and fluidized-bed technology, can be fully automated.

2. No manual feeding is required for the fluidized bed system, significantly reducing labor intensity and improving operational safety and working conditions.

3. Multi-stage gas washing and demister systems are installed at each vent point to ensure efficient dust removal, material recovery, and compliance with environmental emission standards.

4. The system features a compact structure with fewer operating points. Main equipment requires minimal maintenance, while auxiliary conveying systems are simple and reliable, resulting in low maintenance demand.

5. The overall plant has a small footprint and relatively low investment cost.

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