The Thermal Refinery (1910-1940)

The Thermal Refinery (1910-1940)

Incorporating thermal cracking of gas oil into the refinery increased the yield of light and middle distillates, i.e., gasoline, kerosene, and diesel fuel, from crude oil. Although the electric light made the kerosene lamps obsolete, there was still continued demand for kerosene in rural regions because of slow electrification outside the urban areas. The evolution of the refinery in the three decades between 1910 and 1940 was driven largely by the development of thermal cracking processes, although finishing (or chemical treating) processes also started to become important in this era to stabilize and purify the products of thermal cracking.

Figure 11.3 shows a simple schematic diagram of the Burton-Clark batch thermal cracking process. The process employed tubular heating similar to those used in a steam boiler. The series of tubes in the firebox circulate the hot gas oil back to the drum by thermal convection for more uniform heating. The hot gases from the coal-fired furnace are directed up over the high end of the tubes and down over the low end of the slanted bundle. Feed is introduced in the low end of the tubes and tar is withdrawn from the bottom set of tubes. The products of thermal cracking are fractionated in the Bubble Tray Tower and in the high-pressure and low-pressure separators. In the high-pressure separator are the gaseous products hydrogen, methane, and ethane, and in the low-pressure separator are the gases ethane and propane and the liquid products gasoline and kerosene.

Figure 11.3. Burton-Clark Batch Thermal Cracking Process to increase distillate yields [3].

Figure 11.4 shows the configuration of different processes in the thermal refinery. As different from the thermal processes in a current refinery, the thermal refinery includes processes such as Thermal Polymerization, making gasoline from the light olefins propene and butene; Thermal Reforming, to make relatively high octane number gasoline from straight-run naphtha; and gasification of heavy gas oil with steam, to produce town gas (CO+H2) which predates the use of natural gas in cities for domestic heating and cooking.

Figure 11.4. The configuration of the thermal refinery [3].

Click here for a text alternative to the figure above

Atmospheric Column (Pipe Still of Series of Shell Stills)

-Light ends & Other gas sources

Gas Plant

Methane and ethane (fuel gas)

Propane and Butane

Thermal Polymerization

Gas

Tar Residue

Gasoline (joins gasoline treating process)

-Naphtha

Thermal Reforming (light cracking)

Gas

Tar

Gasoline

Gasoline Treating

Gasoline

-Kerosene (Distillate)

Kerosene Treating

Kerosene

-Gas Oil

Thermal Cracking (heavy cracking)

Gas

Tar

Kerosene (Joins kerosene treating process)

Gasoline (joins gasoline treating process)

Gasification using the shift (uses Steam)

“town gas” (hydrogen and carbon monoxide)

-Lube Oil

Lube treating

Lube Oils

-Asphalt Resid (Tar)

Treating asphalt resid (uses steam and air)

Asphalt

-Other Sources of Tar

Fuel Oil

The essential driver of the Thermal Refinery was the shift in demand to gasoline from kerosene because of the introduction of the automobile, the airplane, and electricity. The demand for gasoline rapidly increased when the U.S. declared war on Germany in 1917 and became a party in World War I. Thermal refinery processes, thermal cracking, thermal reforming, and thermal polymerization enabled the expansion of gasoline supply [3]. With the introduction of tetraethyl lead (TEL) as an octane number boosting additive in 1923, a growing interest was directed to production of high-performance gasoline which would be defined later as a high-octane number-gasoline after the introduction of a test method to measure the octane number of gasoline as an anti-knock property in 1931. Because of the toxicity of lead, TEL concentration was limited to 3 milliliters per gallon of finished gasoline (approximately 800 ppm by volume). The addition of lead to motor gasoline continued until the 1970s in the United States when the mandate for adding catalytic converters to automobiles took effect in accordance with the Clean Air Act to reduce tailpipe emissions, and the unleaded gasoline was introduced. Lead is still added to aviation gasoline used in turboprop aircraft in quantities 0.3-0.56 g/L in a range of avgas grades, and efforts are underway to remove lead from the aviation gasoline as well in the near future.

Up through 1924, even with the rapid introduction of various thermal cracking processes, only 20% of the gasoline produced in the U.S. came from thermal processes. But after the introduction of TEL, the contribution of gasoline produced by thermal cracking has steadily increased to reach over 50% of the gasoline pool by the end of the age of the Thermal Refinery in 1940. For reasons discussed in Lessons 6 and 7, the Catalytic Refinery arrived in the scene of brutal competition of making high-performance gasoline and other petroleum fuels in the period leading to and during World War II.