The first thing you might notice as you approach ExxonMobil’s Baytown Petrochemical Complex is the billowing plume of water vapor rising from the facility. What you might not realize is just how far steam and water have traveled… and how important it is to every stage of the refining and chemical production process at Baytown, a complex that covers five square miles and is the largest in the U.S.
Steam and water play a vital role in everything from the very first stages of separating crude oil into usable products to putting finished fuels into tanker trucks for distribution. In fact, while Baytown processes 584,000 barrels of oil every day, it produces several million pounds of steam per hour.
“Every ounce of work”
While some of the Baytown Petrochemical Complex steam helps produce fuel, the bulk is used to transfer thermal and kinetic energy from where it is generated to where it is needed. This is one of many processes of the facility where no molecule is wasted. “We try to get every ounce of work out of the steam we generate,” says Matt Neely, the utilities and optimization coordinator. And optimize he does. Neely ensures that the petrochemical complex can use the same batch of steam to accomplish multiple goals before its energy is completely spent. This means charting the flow of steam from the most energy-intense processes when steam has the highest pressure, to the next-highest pressure and on down the line.
It takes energy to create all that steam, so the Baytown Petrochemical Complex has multiple cogeneration machines for the job.
“They are engines like a jet would have, but they burn natural gas. And instead of generating thrust with exhaust, we produce electricity and heat. We use that heat to generate steam as well,” says Philip Hicks, another member of Baytown’s Utilities and Optimization section. The steam produced from cogeneration reduces the amount of natural gas needed at the site. Altogether, the Baytown facilities have a combined cogeneration capacity in excess of 500 megawatts, the size of many power plants.
A river runs through it
The key ingredient in any steam recipe is a reliable supply of water. In order to get it just right, the Baytown Petrochemical Complex facility uses an onsite water purification plant that strips minerals from the water. The process helps create steam that has the most predictable chemical and physical properties.
“It’s a mechanical engineering job in a chemical engineering world,” Hicks explains. “But from our standpoint the use of steam and cogeneration facilities is a sign of our commitment to run the plant as efficiently as possible. We’re using it to clean up fuels and operate most of the plant. We’re devoted to a high level of environmental performance.”
“We go to great lengths to minimize our energy footprint,” Neely adds. “We want to be at or above government standards.”
By the time water vapor rises above Baytown, the gaseous water particles have reached the end of a complex process that’s helped power one of the world’s largest petrochemical plants in an efficient way.
Steam or water vapor?
Although many who drive by the facility might suspect the white billowing clouds coming from the facility are emissions, they are actually water vapor. What’s the difference between water vapor and steam? Matt Neely explains, “We hesitate to call what comes out of the facility steam because within the utilities industry, steam is pressurized water molecules that are vaporized and able to perform work. Sending steam into the atmosphere would represent an energy inefficiency that we try to avoid since the steam contains energy to perform work.” So now you know – steam still has more work to do.
Cogeneration is the simultaneous production of electricity and steam from a single fuel source. Due to its inherent energy efficiency, the use of cogeneration also leads to reduced GHG emissions. Worldwide, ExxonMobil has interests in approximately 5,300 megawatts of cogeneration capacity, roughly equivalent to the annual energy needs of 2.5 million U.S. homes.
ExxonMobil: Baytown complex fact sheet