(Adds union chief's comments, background details)
By Fabian Cambero
SANTIAGO, Aug 21 (Reuters) - A key production unit at Chilean state copper miner Codelco's Ministro Hales deposit is now operating normally and nearly at full capacity after a start-up delay, the mine's union chief told Reuters on Thursday.
In July, the world's No. 1 copper producer Codelco said for the first time that its newest mine was behind schedule because of problems with its roaster, which sources said forced it to cancel sales in China.
The roaster removes arsenic from the ore at Ministro Hales.
"We're operating at 95 to 98 percent of total capacity," said union chief Claudio Rodriguez, adding "our roaster is working normally ... it is producing."
"The improvements, adjustments and repairs were made ... It has been a success with all the repairs that were made," he added.
However, even at full capacity the roaster will not be able to process all the mine's material, so Codelco has struck a deal to mix it with clean concentrate in Taiwan, sources said earlier this month.
Codelco was not immediately available to comment.
Ministro Hales has been a key part of Codelco's ambitious investment strategy, which in the next stage will plough $23 billion to overhaul older mines with depleted ore grades and launch new projects by 2018. (Reporting by Fabian Cambero; Writing by Anthony Esposito; Editing by Steve Orlofsky and Lisa Shumaker)