How increased output of sulphuric acid using upgrades and new technologies helped an African Copper belt mine improve OPEX and efficiency
Sulphuric acid (H2SO4) plays a central role in industrial applications, particularly in mining, where it is used for the leaching of copper, cobalt, and precious metals. In beneficiation processes, H2SO4 extracts these metals from their ores. Additionally, it supports phosphoric acid production for fertilizers and helps descale equipment to prevent mineral buildup, ensuring machinery operates smoothly.
As global demand for sulphuric acid rises, plants face the challenge of increasing output while minimising operational expenditures (OPEX) and unplanned downtimes. This article looks at a sulphuric acid plant in the African copper belt, where production capacity was boosted from 2200 MTPD to 3000 MTPD. Through targeted upgrades by burner and combustion specialist CS Combustion Solutions, such as ultra-sonic nozzles and advanced combustion technologies, major efficiency and cost improvements were achieved.
Challenges before optimisation
The plant had multiple efficiency issues that hampered performance:
1. Incomplete combustion:
Traditional pressure atomisers caused large sulphur droplets to pass into the waste heat boiler (WHB) and catalyst beds, resulting in fouling, increased pressure drops, and unscheduled maintenance shutdowns.
2. Frequent nozzle plugging:
Regular nozzle blockages forced production stoppages for replacement. Over US$200,000 was spent in under two years on nozzle tips and guns alone.
3. Pressure drop and overheating:
Large droplet sizes and poor atomisation caused hotspots in the refractory lining. Inappropriate chamber design amplified overheating, leading to structural risks.
4. Uneven temperature distribution:
Inefficient combustion chamber dynamics and pressure atomisers caused hotspots on the furnace shell, compromising durability and safety.
These issues resulted in elevated operational costs, reduced productivity, and recurring maintenance challenges.
The optimisation approach
To tackle these problems, CS Combustion Solutions implemented a four-step optimisation strategy:
1. Ultra-sonic nozzle atomisation:
Replacing traditional pressure atomisers with ultra-sonic nozzles was a game-changer. Droplet size was reduced from 400 µm to 110 µm, significantly improving sulphur combustion efficiency. Smaller droplets reduced fouling in the WHB and catalyst beds while extending refractory material life.
2. Swirl bodies for enhanced combustion:
Swirl bodies were integrated into the combustion system, inducing rotational motion in combustion air. This promoted better flame stability and complete combustion, particularly during startup operations when oil is also burned.
3. Single vector wall installation:
Ineffective baffle walls, which failed to mix combustion air and sulphur properly, were replaced with a single vector wall. This solution ensured efficient turbulence and mixing within the chamber, preventing unreacted sulphur from reaching downstream equipment.
4. Computational fluid dynamics (CFD) study:
A detailed CFD study was conducted to simulate the proposed modifications and ensure optimal performance before implementation. This predictive step was crucial in minimising risks and validating the expected improvements.
Results and benefits
The optimisation delivered remarkable improvements in plant operations and efficiency:
1. A production capacityincrease of 30%:
The upgrades enabled the plant to achieve 3000 MTPD, incinerating 40 tonnes of sulphur per hour without compromising
performance.
2. Improved maintenance flexibility:
Operators could replace sulphur guns during operation, eliminating unplanned shutdowns and increasing plant availability.
3. Enhanced combustion efficiency:
Swirl bodies and ultra-sonic nozzles optimised SO2 conversion rates, leading to complete sulphur combustion with lower emissions. Despite the increased capacity, emissions remained controlled owing to improved efficiency.
4. Pressure loss reduction:
The vector wall and optimised combustion chamber design reduced pressure drops, leading to annual OPEX savings of US$160,000 on blower operations.
5. Hotspot elimination:
Smaller droplet sizes and controlled atomisation angles prevented large sulphur particles from impacting the refractory, extending its lifespan and enhancing furnace safety.
6. Cost savings and downtime reduction:
Unplanned shutdowns decreased significantly owing to fewer nozzle failures and better refractory stability.
Key learnings and industry insights
The African Copperbelt plant’s success demonstrates the critical role of high atomisation quality in optimising sulphuric acid production. Advanced technologies, such as ultra-sonic nozzles and swirl combustion systems, significantly improve plant efficiency and reliability.
Ultra-sonic nozzles provide a quick and effective upgrade for existing furnaces, reducing droplet size to minimise fouling and refractory wear. The results of this project also emphasise the value of CFD-based studies for validating design changes before implementation.
For plants facing similar challenges, adopting such innovative solutions can increase capacity, reduce operational costs, and enhance long-term performance.
Conclusion
CS Combustion Solutions’ expertise in ultra-sonic atomisation and combustion optimisation helped the plant in the African Copperbelt overcome major operational challenges. By boosting capacity, enhancing efficiency, and reducing OPEX, this case study showcases how targeted upgrades can provide significant benefits in a competitive market.
As sulphuric acid demand continues to grow, plants must adopt similar strategies to remain efficient and competitive while minimising downtime and costs.
For more information visit: www.comb-sol.com/
