The phrase "a proprietary process" is correct and usable in written English.
You can use it when referring to a method or technique that is owned by a specific company or individual and is not available for public use.
Example: "Our company has developed a proprietary process that enhances the efficiency of our manufacturing operations."
Alternatives: "an exclusive method" or "a patented procedure."
Virdia's key innovation is a proprietary process for inexpensively recycling the acid, which makes acid hydrolysis cheaper and cleaner.
Rick Wilson, a company vice president, says the company currently buys raw biochar from the market and then prepares it with a proprietary process.
A proprietary process has been developed at Gevo to convert agricultural waste products into different types of renewable, alcohol-based, liquid fuels.
The chair is made by hand at the Emeco factory in Hanover with a proprietary process that gives it exceptional strength.
AQT has modified off-the-shelf machines used to make computer hard drives to create CIGS cells using a proprietary process.
Grace had a proprietary process for making precise steel shapes, which resulted in the edges of the steel being razor-sharp.
Recently, Aeterna Laboratories, a pharmaceutical company based in Toronto, Canada, http://www.aeterna.com/, has developed a unique proprietary process to extract biologically active molecules contained in cartilage.
It's a top-secret proprietary process involving a special Magic Infinity Ball (like a Magic 8 Ball, but on its side), darts, Devo-style flowerpot hats, and double shots of the Ye Olde Weevil Squeezins.
Initially, the company used DVD manufacturing processes, but it has since moved on to a still-cheaper proprietary process.
The parts were produced by an advanced IC proprietary process.
Their project used a non-standard and proprietary process definition language; the workflow engine generated tasks, and alerts were delivered to clinicians via email.
