Background

A large nickel mine in Ontario, Canada produces nickel metal, which is used in the manufacturing of smart phones and rechargeable batteries that power electric cars. Sulfur dioxide (SO2) is a major air pollutant emitted in the roasting, smelting and converting of sulfide ores. Fortunately, the SO2 is recovered and utilized to make sulfuric acid (H2SO4), an important coproduct that contributes to the mine’s operational revenue. This high-grade sulfuric acid is used to make recyclable fertilizers and paper products.

Oxygen gas is a critical feed requirement in the process to make sulfuric acid. The gas is generated on site and supplied to the acid plant in the acid production process. Pressurized oxygen must be available or the acid plant will need to halt operations – potentially costing up to $60,000 USD per day in lost acid sales revenue alone. This very scenario worried the nickel mine’s acid plant operations management team since a legacy oxygen plant was being decommissioned. This meant there was no longer a backup supply and any unscheduled downtime would impact the acid plant production.

Problem

The plant has two multistage axial compressors, each powered by a large electric motor. Accurate positioning of the Oxygen Compressor IGVs (Inlet Guide Vanes) is necessary to precisely control the gas throughput of the compressor. Doing this effectively ensures the most efficient gas flow through the compressor. The plant operations group grew increasingly frustrated with the pneumatic actuators’ poor performance in positioning the IGV’s. The mechanical position switches would drift – requiring recalibration every 6-8 weeks. Due to the compressibility of air, the compressor turndown increased to safely operate without surging at the cost of compressor efficiency.

Nickel Mine Previous Actuation Technology

The REXA Solution

In 2016, both compressor IGV’s were upgraded with six REXA Electraulic™ Linear actuators. Plant personnel immediately noticed improved accuracy – repeatable to 0.1% of span regardless of process conditions. The plant also noticed significant energy savings, since the Electraulic™ actuators accurately controlled at a higher maximum capacity flow within turndown range. Each compressor had a 0.5 kW power reduction due to the improved oxygen flow and higher compressor efficiency. The annual savings in electricity is calculated to be $1,092,000 USD per year.

Interested in learning more about our solutions for other applications within the mining industry? Visit our mining page here and browse our full catalog of mining applications! You can also check out our Oxygen Compressor IGV Application Video below!