Perfecting past techniques at the lead smelter

Glencore’s Mount Isa Mines Lead Smelter is revisiting a past technique in the blast furnace to help reduce downtime and maximise production capability.

The purpose of the Lead Smelter blast furnace at Mount Isa Mines is to reduce lead oxide into molten lead metal, and to form a low melting point slag (waste) that removes zinc and iron from the lead.

In the 1960s, Mount Isa and Port Pirie lead smelters jointly developed a water-cooled lead spout, made from cast iron, to transport molten lead metal within their blast furnace operations.

Molten lead reaches temperatures between 1,100 and 1,200 degrees Celsius and passes over the lead spout at a rate of around 33 tonnes per hour. These intense conditions make cooling and durability crucial factors in the success of a lead spout.

The jointly developed lead spout worked well for both operations, until the early 1990s when Mount Isa Mines modified the front of their lead smelter blast furnace and increased the size of the forehearth, rendering the existing spout ineffective.

A new precast, refractory lined steel spout known as the block and tile was trialed and eventually adopted as the replacement solution.

Lead Smelter Operations Superintendent, Bill Scotney, says while it did the job, the block and tile arrangement wore quickly and needed frequent replacement.

“We were shutting down the blast furnace every four or five weeks for around 20 hours just to replace the block and tile spout, impacting production,” Bill says.

“Because of this, we trialed a new water cooled lead spout design between 2014 and 2015 with varied success and eventually returned to the block and tile method.”

Determined that it was an issue they could resolve, the Lead Smelter team decided to revisit the water-cooled lead spout again last year.

“We believe that the primary failure in 2014 and 2015 was due to insufficient cooling of the lead spout, which we’ve now been able to fix,” Bill says.

Lead Smelter Senior Project Coordinator, Peter McKellar, was heavily involved in the project trials and in training the operators to ensure its safe and correct operation.

“The project team did a lot of computer modelling to ensure the effectiveness of the solution and to ensure the safety of the operators in the area,” says Peter.

“Not only are the operators finding the new lead spout design much easier to maintain, but we are currently running even better than our modelling specifications.”

“We implemented the new design this year and we’ve successfully maintained the spout at an acceptable temperature.”

“This bodes well for a long-term solution that should see plant availability increased substantially,” Peter says.

With a new cooling arrangement in place, the success of the spout design should allow the blast furnace to push out shutdowns to once every six months − at which time the forehearth will have reached its useful life and require replacement.

General Manager Smelting and Refining, Adrian Herbert, praised the various functional areas on working together to achieve better operating conditions.

“Continuous improvement initiatives such as this one require input and commitment from a broad cross-section of functions, including engineering, maintenance, operations and safety,” says Adrian.

“The redesigned water cooled lead spout solution is proving very effective and we are already seeing the benefits on plant availability and lead bullion production.”

“This is just one of many improvement projects we have been working on across the entire Queensland Metals Smelting and Refining department,” Adrian says.