Application of Calcined Petroleum Coke in Chloride-Process Titanium Dioxide Production

I. Overview

The chloride process is currently the mainstream technology for global titanium dioxide (TiO₂) production. Since 2004, all TiO₂ produced in the United States has been manufactured using the chloride process. In this process, Calcined Petroleum Coke (CPC) plays an indispensable role as the core reducing agent and energy source in the chlorination reaction.

A chloride-process TiO₂ plant typically consists of four main sections: chlorination, purification, oxidation, and post-treatment. The application of CPC spans across this complete process flow.

II. Chlorination Section – The Core Application

The chlorination section is where CPC plays its most critical role. The reaction principle is: using rutile (TiO₂ ≥ 90%) or high-titanium slag as raw material and CPC as the reducing agent, titanium-containing materials are chlorinated with chlorine gas at high temperatures to produce titanium tetrachloride (TiCl₄).

The core chemical reactions are as follows:

TiO₂ + C + 2Cl₂ → TiCl₄ + CO₂

TiO₂ + 2C + 2Cl₂ → TiCl₄ + 2CO

In actual production, rutile or high-titanium slag is mixed with CPC in a specified ratio and fed into a fluidized-bed chlorination reactor, heated to approximately 950–1000°C. Chlorine gas is introduced from the bottom of the reactor and reacts with the materials at high temperatures. The carbon in CPC serves as the reducing agent, removing oxygen from the titanium ore and enabling TiO₂ to react with chlorine to form TiCl₄.

Meanwhile, impurities in the raw materials—including iron, manganese, aluminum, calcium, magnesium, and silicon—also undergo chlorination to form corresponding chlorides (such as FeCl₃, MnCl₂, AlCl₃, CaCl₂, MgCl₂, SiCl₄, etc.). These impurity chlorides are subsequently removed in the purification section.

The chlorination of TiO₂ is a reversible endothermic reaction that cannot proceed without a reducing agent—even at temperatures as high as 1800°C, chlorination will not occur in the absence of a reductant. CPC is precisely this irreplaceable reducing agent.

III. Quality Requirements for CPC

Chloride-process TiO₂ production has specific quality requirements for CPC:

1. Low Ash and Low Volatile Content: Due to its low ash and low volatile content, CPC generates only minimal HCl during the reaction, which helps protect equipment and improve product purity.

2. Preference for Shot Coke Structure: In TiO₂ applications, shot coke is preferred over sponge coke. Shot coke is harder and contains a lower percentage of fines (-100 mesh or -150μm), whereas fines pass straight through the chlorinator and result in carbon loss. Shot coke also has a tighter particle size distribution, better abrasion resistance, and generates fewer fines during handling.

3. Higher Impurity Tolerance: Compared to CPC used for anode production, TiO₂ production has a higher tolerance for impurities such as vanadium and nickel.

IV. Purification and Oxidation Sections

The crude TiCl₄ generated in the chlorination section undergoes cyclone separation, condensation, and distillation to produce purified TiCl₄. In the oxidation section, purified TiCl₄ reacts with oxygen at high temperatures to produce the final product TiO₂ and chlorine gas. The chlorine gas generated in the oxidation process is recovered and recycled back to the chlorination section.

Although CPC does not directly participate in the oxidation stage, its role in the chlorination stage has a critical impact on the efficiency and quality of the entire oxidation process.

V. Conclusion

CPC plays an irreplaceable core role in chloride-process TiO₂ production—from the reduction reaction in the chlorination section to providing high-purity TiCl₄ feed for subsequent purification and oxidation. Its excellent carbon content, low ash content, and suitable physical structure make it an indispensable key raw material for chloride-process TiO₂ production.

Choosing high-quality CPC is a critical guarantee for ensuring efficient and stable operation of chloride-process TiO₂ production lines.