Africa's biggest refinery is getting bigger. Nigeria's Dangote refinery has started work on a second crude processing unit that will add another 700,000 barrels per day (bpd) of capacity, putting the complex on track to rival the world's largest refining site and giving billionaire owner Aliko Dangote a much larger role in global fuel markets. According to Dangote Petroleum Refinery CEO David Bird, construction is already underway at the Lekki site outside Lagos. The new refinery is expected to be online by the end of 2028 and would lift total…