Titanium dioxide is a naturally-occurring substance resulting from the oxidation of the element titanium. Also called titanium IV oxide or titania, it is one of the whitest materials known, and is used in many industries to provide whiteness and opacity to products such as paints, plastics, papers, inks, foods, and cosmetics. It is highly refractory in nature, often used in cosmetics to reflect light away from the skin, or in sun block for the same purpose. Other industries use its refractory nature in protective coatings for automobile and marine parts, and in optical mirrors. Titanium dioxide is also used in building and construction materials.

Due to its many uses, titanium dioxide is one of the most-produced chemicals worldwide for industrial and other purposes, and it accounts for 70% of the total production volume of pigments in the world.

In appearance, titanium dioxide is a crystalline white powder and has a bulk density of 48 lb/cu ft (0.77 g/cc).1

Characteristics and Challenges:

Titanium Dioxide is an odorless, highly cohesive and adhesive white powder containing agglomerated lumps and tends to coat steel surfaces. It is moderately abrasive, non-free-flowing, and tends to pack, cake and smear.

TiO2 is incompatible with strong oxidizers and strong acids. Violent or incandescent reactions may occur with metals (fused and highly electropositive) such as aluminum, calcium, magnesium, potassium, sodium, zinc and lithium.

As a safety concern, prolonged exposure to titanium dioxide should be avoided. Inhalation of the dust may cause respiratory problems; titanium dioxide may cause drying of the skin with repeated contact. There is some evidence to suggest that titanium dioxide is a carcinogen.2

Titanium dioxide should be stored in a clean, dry space away from exposure to high temperatures, open flames, and strongly aromatic chemicals.

Titanium dioxide is difficult to handle; it cakes and packs easily. As a result, titanium dioxide fines have a tendency to form deposits in the conveying line. Titanium dioxide is insoluble with water and solvents. Manufacturers must remain vigilant to prevent spills and the cleanup that would follow. Intensive and costly dry vacuuming, with appropriate filtration, is

Titanium Dioxide

the preferred method for removing titanium dioxide surface dust and cleaning spills.

If the titanium dioxide arrives at the processing facility in bulk bags, the frames used to discharge the bags should be equipped with additional accessories to reduce the need for operator intervention when emptying the titanium dioxide from the bag. This includes features such as spring-loaded frames that will elongate and stretch the bags as they empty and lighten, making them rigid and removing any pockets of titanium dioxide cornered in the bags. Bag activating devices are usually effective in dislodging collections of titanium dioxide, promoting a better flow. Some of these bag activating devices also serve as an airtight seal between the bulk bag and the receiving hopper.

After the bulk bag has been connected to the receiving hopper and the titanium dioxide begins to flow, the air inside the hopper is forced out. Unless this displaced air passes through a filter, airborne dust particles can escape into the surrounding atmosphere, creating a potentially hazardous situation. A dust collector mounted on the discharger frame will contain the titanium dioxide inside the conveyance system. Titanium dioxide dust trapped in the filter media can be returned to the receiving hopper by a pneumatic pulse through the filter.

If the titanium dioxide is being added into the processing stream from smaller (>50 lb./22.76 kg.) bags, a bag-breaking station with a dust hood, filtration devices and a pneumatic pulse cleaner is the recommended solution to support the manual unloading of the material. If empty bag disposal is an issue, a dust-tight bag compacting system may be necessary.

With its poor flow characteristics, titanium dioxide will tend to "rat hole" or bridge in hoppers, completely blocking the flow of the material, causing a shutdown while it is removed and elevating the risk of dusting or spillage. Feed hoppers should be designed with proper geometry and may need to incorporate devices such as air fluidizers or vibrators to dislodge titanium dioxide from hopper walls or mechanical agitators to promote flow.

If a flexible screw is being used to convey the material, it is important to use a screw that matches titanium dioxide's characteristics and other application requirements. Generally a screw with a wider, flatter surface than the standard-sized screw is necessary for this type of material.

Should your titanium dioxide application feature the loading the material into bulk bags, the bag capacity will be maximized by use of a vibratory densification deck to level the titanium dioxide as it fills the bag and by the application of load cells to attain the desired weight. Seals and other dust-containment devices will ensure a dust-tight operation.

Flexicon Applications:

Flexicon designed and built a bag dump station with integral flexible screw conveyor system that helped a manufacturer of protective PVC lining products for sewer pipes blend titanium dioxide into the process while containing dust. Another installation of a Flexicon flexible screw conveyance system resulted in reducing mixing time by 30% for a manufacturer of automotive paints and primers.

Flexicon's dust suppression and collection systems ensure proper containment of titanium dioxide throughout the conveyance process.

Consultation with a Flexicon specialist will help you decide if a flexible screw or pneumatic solution best fits your titanium dioxide application.

Flexicon's expert design and engineering staff will weigh each parameter and recommend the best solution for you. Upon request, Flexicon's test lab will simulate your titanium dioxide handling functions before the system is installed in your plant.

Flexicon's product line of advanced flow promotion conveyors, high flow hoppers, deaeration/densification decks and a host of other components and accessories are proven performers that promote flow while reducing degradation, dusting and/or the separation of blends comprised of disparate particles.

Related Articles on Titanium Dioxide:

1 Source: Powder and Bulk. Com - Bulk Density Chart
2 TDMA (Titanium Dioxide Manufacturers Association)

Sources: Wikipedia, Organic Makeup