Process Flow and Key Equipment in Coke Oven Gas By-Product Recovery

1. Introduction: Why By-Product Recovery Matters

In modern coke-making industries, Coke Oven Gas (COG) is not only a fuel gas but also a valuable carrier of chemical components.
Raw COG contains various recoverable substances, including tar, ammonia, benzol, naphthalene, and hydrogen sulfide.

The primary objectives of a By-Product Plant (BPP) are:

• Maximizing resource utilization

• Reducing environmental emissions

• Improving the overall economic efficiency of coke plants

As a result, the BPP system has evolved from an auxiliary unit into a core process section in integrated coke plants.

2. Overall Process: PGC + BPP

The treatment of coke oven gas generally consists of two main stages:

1️⃣ Primary Gas Cooling (PGC)

Main functions:

• Cooling raw gas from approximately 700–800°C to 80–90°C

• Condensing tar and moisture

• Reducing the load on downstream systems

2️⃣ By-Product Recovery (BPP)

After primary cooling, the gas enters the BPP system for multi-stage separation and recovery:

Coke Oven Gas → Primary Gas Cooler (PGC) → Tar Removal → BPP System
                                                           ↓
        ├─ Ammonia Recovery
        ├─ Benzol Recovery
        ├─ Naphthalene Removal
        ├─ Desulfurization (H₂S Removal)
        └─ Further Gas Purification

3. Core Process Units in a BPP System

1️⃣ Tar Condensation and Separation

Function:

• Condense tar vapors into liquid phase

• Achieve gas-liquid separation

Key equipment:

• Tar condenser coolers

• Gravity separators / electrostatic tar precipitators

2️⃣ Ammonia Recovery System

Principle:

• Absorption of ammonia using water or acidic solutions

Typical processes:

• Saturator process

• Ammonium sulfate production (fertilizer by-product)

3️⃣ Benzol Recovery System

Function:

• Recover aromatic hydrocarbons (benzene, toluene, xylene)

Key steps:

• Absorption (commonly using wash oil)

• Desorption and distillation

4️⃣ Naphthalene Removal

Challenge:

• Naphthalene tends to crystallize and block pipelines

Solutions:

• Controlled cooling and dissolution

• Anti-fouling system design

5️⃣ Desulfurization

Objective:

• Remove hydrogen sulfide (H₂S) to meet environmental standards

Common methods:

• Wet desulfurization (e.g., HPF process)

• Dry desulfurization

4. Key Equipment: The Critical Role of Heat Exchangers

Heat exchange equipment plays a decisive role in efficiency and operational stability throughout the BPP system.

Main application areas:

• Tar condenser coolers

• Benzol condensers

• Ammonia liquor coolers

• Gas cooling units

Common heat exchanger types:

Key technical challenges:

• Fouling and blockage

• Corrosive media (NH₃, H₂S)

• Fluctuating operating conditions

• Maintenance complexity

Efficient design and proper equipment selection are therefore essential for long-term stable operation.

5. Development Trends in BPP Systems

With increasingly stringent environmental and efficiency requirements, BPP systems are evolving toward:

✔ Higher Efficiency

• Improved heat recovery

• Reduced energy consumption

✔ Lower Emissions

• Deep desulfurization and ammonia removal

• Compliance with ultra-low emission standards

✔ Digitalization

• Integration of digital twin technologies

• Predictive maintenance and real-time monitoring

✔ Modularization

• Integrated equipment design

• Easier installation and retrofit

6. Conclusion

The By-Product Plant (BPP) serves as a critical bridge between coke production and chemical recovery.
Through optimized process design and efficient heat exchange solutions, it is possible to maximize resource recovery while ensuring operational stability and environmental compliance.

In future coke plant upgrades, high-efficiency, reliable, and easy-to-maintain heat exchange equipment will play a key role in enhancing overall system performance.