The sulfur content in transportation fuels is being controlled at lower levels around the world in order to reduce emissions from vehicles. Conventional HDS technologies have limitations in terms of product quality and costs that are undesirable to refiners. Phillips Petroleum Company's S_Zorb Sulfur Removal Technology (SRT) is commercialized and available to meet the needs of refiners for production of ultra-low sulfur fuels. The S_Zorb process can economically reduce sulfur content of gasoline to less than 10 parts per million weight (ppm) with minimal octane loss, minimal hydrogen consumption and near zero volume loss. These results are obtained through use of a novel sorbent, which selectively removes sulfur from hydrocarbon molecules. In conjunction with sorbent development, a reliable plant design was developed that allows continuous operation cycles paralleling major refining units, such as a fluidized catalytic cracker (FCC), thus reducing operating and maintenance costs.
S_Zorb SRT is not a modified hydrogenation technology. Rather, it uses a sorbent that operates in a fluidized bed reactor. A stream of vaporized gasoline and hydrogen fluidizes the reactor bed yielding a low sulfur product gasoline with little octane loss. The sorbent circulates between the reactor and the regeneration section allowing regeneration of sorbent resulting in run lengths of a typical FCC unit. Matching the run lengths of the S_Zorb unit and the FCC unit provides refiners an economic advantage, since the refinery will be able to remove sulfur from FCC naphtha when the FCC unit is in operation, thus decreasing extremely costly refinery downtime. The discussion will focus of sulfur removal from FCC naphtha because that steam contains over 90% of the sulfur found in gasoline, however S_Zorb SRT works well with all gasoline range materials.
The latest advancement is S_Zorb-Diesel SRT technology. Phillips is designing a diesel unit for its Sweeny, Texas refinery.
Process Overview The Phillips Petroleum S_Zorb SRT operates in a fluidized bed to allow consistent performance throughout the run cycle. The refining industry has not made wide use of fluidized bed reactors before the arrival of S_Zorb SRT, but they have been used in the chemical industry, where their benefits are widely recognized. These include maintaining start of run activity through the combination of regeneration of sorbent and sorbent replacement; excellent temperature control through the bed; no coke build up through the run cycle; fast response to changes in reaction conditions; and large turndown capability. In S_Zorb units these combine to give stable operations with run lengths for gasoline units that can easily match an FCC unit. Diesel units will exhibit run lengths that are longer t