admin“Mwana is pleased to announce progress at its Freda Rebecca Gold Mine in Zimbabwe following the previously reported leach tank failure in February,” the company said in a statement last Friday.
A leach tank is used in metallurgical processes to extract and trace metals from ore. In this technique, ground ore is mixed with a reagent inside the tank to form a slurry, allowing for recovery of the metal.
“During March a total of 50 000 tonnes of ore was milled at a grade of 2,5 grammes per tonne, achieving a recovery of 80,2 percent,” Mwana Africa said in the statement. Mwana Africa last month said gold production would suffer in the short term while recovery of the precious metal would affect gold recovery in the medium term.
The accident resulted in the suspension of plant processing operations to allow for repairs while measures to restore safety were also underway.
The brief suspension of operations worried the Alternative Investment Market-listed conglomerate as Freda has been its cash cow, contributing 98 percent of the mining company’s US$83,1 million annual revenue.
Mwana Africa said last month five of Freda’s employees were injured in the accident, but the group indicated that all the victims were in a stable condition.
Normal production throughput has been recommenced as from April 1, using tanks 1, 4 and 5 as leach tanks (rather than tanks 1, 2 and 3) with eight absorption tanks, to ensure that minimum leach times required for full throughput. Management is confident this will work as an interim solution, at full production, with the intention of getting back to an optimal tank configuration of tanks 1, 2 and 3 as leach tanks with 10 absorption tanks over the next few months.
The company said after the incident, immediate modifications were made to the processing circuit to allow limited milling and production to continue.
These modifications included using tanks 1, 4 and 5 as leach tanks and were tested in February and March, while running the mills at a lower throughput.
This configuration has enabled full mill throughput to be re-established.
“The planned rehabilitation of tanks 2 and 3 has commenced. Repairs to tank 2 have progressed well and will be completed during April 2013,” the firm said.
On completion of the repairs to tank 2, the system configuration will be changed so that tanks 1, 2 and 4 will be used as leach tanks. Construction work to replace tank 3 has started and an external contractor is on site to complete removal of damaged tank infrastructure and commence the build.
Following the successful clean-up of the pulp spillage in February, the Environmental Management Agency has acknowledged the mine’s compliance with the environment protection body’s minimum clean-up requirements.
Freda, in conjunction with EMA, has continued to monitor the discharge levels in the drainage canal and these have returned to acceptable levels.
The Mines Inspectorate has completed its preliminary investigation report, providing recommendations for the required structural tank repairs.
Mwana Africa said Freda has also reviewed its internal standards for pressure and storage vessels. As part of that review, ultrasonic thickness tests and integrity tests have been carried out on nine out of the 13 tanks to date.
In addition, a structural audit has been conducted across the complete plant.
Online Reporter