Selection and Application of Refractory Linings for Carbon Black Reactors

I. Reactor Structure and Operating Conditions

A carbon black reactor primarily consists of five main components: the combustion chamber, throat, reaction section, quench section, and residence section. The refractory lining within each of these sections must withstand complex physicochemical interactions.

1. Characteristics of Process Media and Atmosphere

The reactor utilizes heavy oil as fuel and hydrocarbons as feedstock. During the production process, the interior of the reactor is subject to multiple simultaneous processes—including fuel combustion, thermal decomposition of the feedstock, and spray quenching of the carbon black—accompanied by the generation of thermal decomposition products derived from both the fuel and the feedstock. These various media engage in complex physicochemical reactions with the refractory lining materials.

2. Temperature and Airflow Conditions
Operating Temperature: Normal operating temperatures reach 1600–1700°C.
High-Temperature Zones: Temperatures at the downstream end of the throat exceed 1700°C, with certain localized hot spots reaching up to 1900°C.
Airflow Characteristics: The high velocity of the hot gas stream subjects the furnace lining to intense erosive scouring.
Temperature Fluctuations: Periodic temperature variations occur due to furnace shutdowns necessitated by product changeovers or operational adjustments.
3. Erosive Factors
Damage to the furnace lining primarily stems from the combined effects of three factors:
Thermal Stress: The complex furnace atmosphere subjects the refractory bricks to thermal shock, triggering structural spalling.
Chemical Erosion: Ash generated during the pyrolysis of fuel and raw materials chemically attacks and erodes the refractory bricks.
Steam Effects: Water vapor present in the gas stream penetrates the furnace lining, thereby accelerating material degradation.

II. Performance Requirements for Refractory Materials

Failure of the reactor lining primarily stems from two factors: first, the refractory bricks are subjected to severe thermal shock under complex atmospheric conditions, leading to structural spalling; and second, the ash generated by the pyrolysis of fuel and feedstock causes continuous corrosion of the refractory materials.

Consequently, the refractory materials used for the inner lining must simultaneously possess high refractoriness, excellent thermal shock resistance, high bulk density, low apparent porosity, and robust resistance to high-temperature corrosion and gas-flow erosion.

III. Common Types of Refractory Materials
The refractory bricks commonly used for lining carbon black reactors primarily include the following categories:
1. Alumina-Silica Refractory Bricks
This category includes high-alumina, mullite, and corundum bricks, which are primarily utilized in medium-to-low temperature zones.
2. Chrome-Corundum Bricks
These are composite refractory materials containing varying proportions of chromium, produced through high-temperature sintering; they exhibit excellent thermal shock resistance.
3. Zirconia Refractory Bricks
This category encompasses both chrome-corundum products containing zirconia and pure zirconia bricks; they are characterized by a high melting point, high density, low thermal conductivity, and excellent chemical stability.
4. Silicon Carbide Composite Bricks
This material is employed in the masonry lining of certain reactors, making it suitable for specific operating conditions.

IV. Classification and Zonal Selection of Refractory Materials
Based on variations in temperature zones, a graded configuration strategy is adopted for the lining of carbon black reactors. Commonly used materials include alumina-silica, corundum, chrome-corundum, and zirconia-based refractory bricks; silicon carbide composite bricks are also selected for certain specific zones.
1. Low-Temperature Zone (≤ 1300°C)
For the cooling zone, high-alumina bricks (containing 65%–70% alumina) or clay bricks are selected, balancing both economic efficiency and basic operational requirements.
2. Medium-Temperature Zone (1550–1750°C)
Corundum-mullite bonded refractory bricks are employed in this zone, leveraging their excellent high-temperature strength and thermal shock resistance.
3. High-Temperature Zone (1750–1925°C)
Chrome-corundum refractory bricks are selected for this zone. These materials are produced through high-temperature sintering; their chromium content endows them with exceptional thermal shock resistance and structural stability.
4. Ultra-High-Temperature Zone (2000–2100°C)
Pure zirconia (ZrO₂) refractory bricks are mandatory for this zone. Zirconia-based refractory materials are characterized by a high melting point, high density, low thermal conductivity, and excellent chemical stability; although their cost is relatively high, they are capable of meeting the demanding operational requirements of extreme service conditions.

V. Conclusion
The scientific selection of refractory materials for the lining of carbon black reactors should be based on a differentiated configuration tailored to the temperature distribution and operational characteristics of each specific section. By matching refractory bricks of appropriate composition to the various temperature zones, it is possible to effectively control production costs while simultaneously ensuring the long-term, stable operation of the furnace lining, thereby achieving a harmonious balance between technical performance and economic efficiency.