Best way to process XLXS files to CSV in background

I'm trying to find a way to open an XLSX file and Export to CSV UTF-8 in the background without
having to bring into a grid or other component.


That's one of the things FlexCel is designed to do. Just create a xls := TXlsFile.Create object, call .Open(fileName), then call xls.Save or xls.Export to export it to CSV. You can use UTF8 or whatever encoding you like, and there is no visual component involved.

You can see an example of code here near the end:

(and also, know about all the issues with CSV you need to be aware of...)