Shareholders at refinery operators Frontier Oil Corp. and Holly Corp. voted on Tuesday to merge their companies, in a $3 billion deal expected to close Friday.

Frontier Oil said the deal was approved by 99 percent of the shareholder votes cast. The same percentage of Holly shareholders voted to issue the shares necessary for the share swap transaction, the company said. Holly shareholders also approved changing the company's name to HollyFrontier Corp., the surviving business once the merger closes.

The deal was announced in February as part of a wave of consolidation in the refining industry. Refineries that had struggled to pass on high oil prices during the recession started to see profits surge last year as demand grew for gasoline and other fuels. Marathon Oil announced earlier this year that it would spin off its refining business, and ConocoPhillips plans to minimize its refining arm from 24 percent to 15 percent of its core business.