Exxon Mobil process completely bypasses refinery and feeds crude oil to cracking furnaces
HOUSTON – Two new steam-cracking processes developed by Exxon Mobil and Saudi Aramco will allow petrochemical producers to essentially skip the refining process in converting crude oil directly to light olefins, according to consultancy IHS Inc.
“In 2014, Exxon Mobil commissioned a world-scale facility in Singapore that produces 1 million tons per year of ethylene directly from crude oil,” said Anthony Pavone, director of engineering at IHS Chemical.
These new processes could potentially save refiners as much as $200-per-ton of ethylene produced, according to a comprehensive engineering analysis conducted by IHS.
“We at IHS Chemical believe this process nets ExxonMobil about $100 to $200 per metric ton above traditional naphtha cracking,” said Pavone.
The ExxonMobil process completely bypasses the traditional naphtha cracking process. Saudi Aramco has its own process for crude oil to olefins, and in June, Aramco announced a joint venture with SABIC to study building a ‘crude oil-to-chemicals’ complex in Saudi Arabia.
Though the exact process configuration for the potential joint-venture was not disclosed, it is possible this complex will employ the Aramco process, at least in part.
According to the IHS report, the ExxonMobil process completely bypasses the refinery and feeds crude oil to the cracking furnaces.
These have each been modified to include a flash pot between the convective and radiant sections of the furnaces. Next, the crude oil is pre-heated and then flashed, IHS said, essentially ‘topping’ the lighter components from the crude.
This extracted vapor, the IHS report said, is then fed back into the furnace’s radiant coils and cracked in the usual fashion. The heavier liquid that collects at the bottom of the flash pot is either transferred to the adjacent ExxonMobil refinery, or sold into the merchant market.
“This analysis was conducted at a $50 per barrel cost for crude oil,” Pavone said. “As you might expect for Singapore, this process requires the local availability of light, sweet crude.”
The Aramco process, IHS said, works along an entirely different concept from that of the ExxonMobil crude-to-olefins process. As of yet, the Aramco process is still only a proposed project; no facility actually has been built to test the process.
The IHS report said the Aramco process begins by feeding the whole barrel of crude to a hydrocracking unit, which removes sulfur and shifts the boiling point curve significantly toward lighter compounds.
The gas-oil and lighter products are sent to a traditional steam cracker, while the heavier products are sent to a proprietary, Aramco-developed deep-fluid catalytic cracking unit that maximizes olefin output.
“The hydrocracker and deep-fluid catalytic cracker add significant capital costs, though, so at 15 per cent pre-tax return on investment, we estimate the Aramco process would pencil in at roughly equivalent costs to naphtha cracking in Saudi Arabia,” said Pavone.