SEMI-FINISHED PRODUCTS by AGRU
At CCR Refinery, an industry leader in precious metals processing, copper refining is being carried out by electrolysis in an acid bath containing 15 % sulfuric acid. Using this process, copper with a purity of 99.9 % can be extracted. The process leaves behind a waste solution still containing valuable metals, which is why the solution is directed to a reclamation process.
This secondary stage is carried out in an evaporator unit, where the temperature of the solution is raised by injection of hot air to about 150 °C / 300 °F, causing the precipitation of nickel sulphate out of the solution. The high temperature also leads to the increase of the sulfuric acid concentration to 70 %, as well as creating a highly corrosive acid-containing vapour, which needs to be vented. And this ventilation was a major problem.
The old lining of the ventilation pipe could not stand the corrosive gases, high temperatures and temperature fluctuations, and vacuum pressure. These conditions soon led to cracks, pinholes, and leaks in the pipe lining causing the shutdown of one of two affected production lines every two to three months to repair the lining. The costs for the repair and loss of productivity made CCR´s engineers look for an alternative solution.
After analysing the process requirements, a new PFA lining was installed in the ventilation pipes using a newly-developed adhesive for application in high-temperature environments. PFA sheets from AGRU were used due to the outstanding chemical and thermal resistance of the fluoropolymer.
After one year of operation, CCR has not had to do any maintenance to the lining. The decision to use the new PFA lining system resulted in notable savings in repair costs and equipment downtime, thereby also increasing the plant productivity and workplace safety. According to an engineer from CCR, the PFA lining “has already more than paid for itself in terms of saved maintenance costs and less downtime.”