What are the specific control requirements for heating furnaces in zero-reforming DRI? Optimize Your Heat Management

Precise temperature regulation and hydrocarbon management are the absolute critical control requirements for heating furnaces in zero-reforming direct reduction iron processes. You must maintain gas outlet temperatures strictly between 800°C and 1000°C while actively preventing degradation mechanisms like coking and carburization within the furnace tubes.

Core Insight: The central engineering challenge is heating volatile, hydrocarbon-rich gases (like coke oven gas) high enough to enable downstream internal reforming, without allowing those same hydrocarbons to destroy the heating furnace tubes through carbon deposition.

Regulating Outlet Temperature

The Critical Temperature Window

The furnace must heat the reducing gas to a specific target range of 800°C to 1000°C. Maintaining this window is not optional; it is a fundamental requirement for the chemistry of the process.

Enabling Internal Reforming

The heated gas is destined for the shaft furnace. Once inside the shaft furnace, the metallic iron acts as a catalyst.

This catalytic reaction drives internal reforming, which is dependent on the thermal energy provided by the heating furnace. If the outlet temperature drops below the threshold, the reforming process downstream will be inefficient.

Managing Hydrocarbon Risks

Handling High-Hydrocarbon Sources

Zero-reforming processes typically utilize gases with high hydrocarbon content, such as coke oven gas. Unlike simpler fuel sources, these gases are chemically complex and reactive.

The control system must account for the specific composition of these gases during the direct heating phase.

Preventing Coking

The most significant operational risk is coking. This occurs when carbon deposits form on the interior of the furnace tubes.

If the heating process is not managed correctly relative to the gas flow and composition, these deposits will accumulate. This restricts flow and insulates the tubes, reducing heat transfer efficiency.

Avoiding Carburization

Beyond surface deposits, there is a risk of carburization. This happens when carbon penetrates the metal structure of the furnace tubes.

Carburization compromises the metallurgical integrity of the tubes, leading to brittleness and eventual failure under high thermal stress.

Understanding the Trade-offs

Process Efficiency vs. Equipment Life

There is an inherent tension in operating these furnaces. Higher temperatures within the 800-1000°C range generally benefit the downstream internal reforming process.

However, pushing the temperature toward the upper limit increases the kinetics of coking and carburization.

The Cost of Instability

Fluctuations in temperature or flow rate are dangerous. Inconsistent control allows regions of the furnace to overheat or stagnate, creating localized hot spots where coking accelerates.

Strict stability is required to protect the expensive alloy tubes from rapid degradation.

Making the Right Choice for Your Goal

To optimize your furnace control strategy, consider these priorities:

• If your primary focus is Process Efficiency: Prioritize maintaining the outlet temperature closer to 1000°C to maximize the catalytic internal reforming effect in the shaft furnace.
• If your primary focus is Asset Preservation: Focus strictly on monitoring hydrocarbon reactions to prevent coking and carburization, ensuring the longevity of your furnace tubes.

Success lies in delivering the necessary heat for reforming without sacrificing the integrity of your infrastructure.

Summary Table:

Control Requirement	Target Range / Risk	Critical Impact
Outlet Temperature	800°C - 1000°C	Enables downstream internal reforming in shaft furnace.
Coking Control	Prevent carbon deposits	Maintains flow rates and heat transfer efficiency.
Carburization Prevention	Protect tube metallurgy	Prevents brittleness and premature failure of alloy tubes.
Gas Source Management	High-hydrocarbon gases	Requires stable heating to handle complex coke oven gas.

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References

1. Yuzhang Ji, Weijun Zhang. Development and Application of Hydrogen-Based Direct Reduction Iron Process. DOI: 10.3390/pr12091829

This article is also based on technical information from Kintek Solution Knowledge Base .