Waste Heat Recovery Solution for Rungta Mines Limited

Client: Rungta Mines Limited
Official Website: https://www.therungtagroup.com

Background

Rungta Mines Limited is a well-established industrial group in India, with extensive operations in mining, steelmaking, and metallurgical production. As part of its blast furnace efficiency improvement program, Rungta Mines sought to enhance energy utilization in a 650m³ blast furnace hot blast stove system.

One of the key objectives was to recover high-temperature flue gas waste heat and reuse it to preheat combustion air and fuel gas, thereby reducing fuel consumption and improving overall thermal efficiency.

Engineering Challenges

The project presented several technical and operational challenges:

• High flue gas temperatures reaching up to 450°C

• Large air and gas flow rates under continuous blast furnace operation

• Strict limits on pressure drop to avoid increasing fan power consumption

• Long-term reliability requirements in a high-temperature metallurgical environment

• Stable performance under variable operating conditions

A well-balanced heat exchanger solution was required to address efficiency, resistance, and durability simultaneously.

Solution Overview

To meet these requirements, a hot blast stove heat exchanger system was implemented, consisting of two independent units:

• Air Heat Exchanger – for combustion air preheating

• Gas Heat Exchanger – for fuel gas preheating

Both units use high-temperature flue gas as the heat source and adopt a tubular heat exchanger design, which is widely proven in blast furnace and metallurgical applications.

Air Heat Exchanger – Case Highlights

The air heat exchanger plays a critical role in improving combustion efficiency and stabilizing hot blast stove operation.

Operating Features

• Designed for flue gas temperatures up to 450°C

• Handles air flow rates exceeding 55,000 Nm³/h

• Raises ambient air temperature to ≥180°C

• Flue gas outlet temperature controlled within 150–180°C

Engineering Benefits

• Low pressure loss on both air and flue gas sides

• Stable heat transfer performance during continuous operation

• Robust tubular structure suitable for high-temperature service

Gas Heat Exchanger – Case Highlights

The gas heat exchanger ensures that fuel gas enters the hot blast stove at a stable and elevated temperature, improving combustion consistency.

Operating Features

• Processes fuel gas flow rates above 80,000 Nm³/h

• Increases gas temperature from approximately 60°C to ≥180°C

• Operates under the same high-temperature flue gas conditions

• Designed for low system resistance

Engineering Benefits

• Improved ignition reliability and flame stability

• Reduced thermal fluctuations in the hot blast stove

• More efficient fuel utilization under varying load conditions

Materials and Structural Design

Heat Transfer Tubes

• Manufactured from carbon steel suitable for high-temperature applications

• Tube wall thickness designed in accordance with national standards to ensure strength and durability

Structural Components

• Support frame fabricated from Q235B carbon steel

• Designed for mechanical stability in long-term industrial operation

Thermal Insulation

• Internal insulation system with liner plates and insulation wool

• Effectively minimizes heat loss

• Controls external surface temperature to enhance operational safety

Performance Results

After commissioning, the hot blast stove heat exchanger system delivered the following results:

• Effective recovery of high-temperature flue gas waste heat

• Stable preheating of both combustion air and fuel gas

• Improved thermal efficiency of the hot blast stove

• Reduced overall fuel consumption

• Reliable, continuous performance under blast furnace operating conditions

Conclusion

This case study demonstrates how a properly engineered hot blast stove heat exchanger system can significantly enhance energy efficiency in blast furnace operations. By combining a proven tubular design, suitable material selection, and optimized thermal parameters, the system achieves a balance between efficiency, reliability, and low operating resistance.

For metallurgical plants seeking blast furnace waste heat recovery, fuel efficiency improvement, and long-term operational stability, this solution provides a practical and proven reference.