Byline: Thinnes, Billy
Sulfur is naturally present as an impurity in fossil fuels. When the fuels are burned, the sulfur is released as sulfur dioxideuan air pollutant that contributes to respiratory problems for humans and acid rain conundrums in nature. Environmental regulations have increasingly restricted sulfur dioxide (SO2) emissions, forcing refiners to remove the sulfur from both fuels and exhaust gases.
Two significant ways in which refiners manage sulfur are via the Claus sulfur recovery process and through amine unit management programs. In the typical Claus process, the acid gas feed is partially oxidized to generate SO2, which then reacts with the remaining hydrogen sulfide (H2S) over a catalyst to produce sulfur. Most Claus sulfur plants involve two or three catalytic stages. Meanwhile, amine management involves close monitoring and fine-tuning of a refineryEs amine unit, which is used to remove mercaptans, carbon dioxide (CO2) and H2S from various hydrocarbon streams.
CLAUS SULFUR RECOVERY PROCESS
Jeff Bolebruch is a senior market manager at Blasch Precision Ceramics and he has a distinct take on how best to apply the Claus recovery process for a refinerEs benefit.
oThe Claus process is the most commercially significant gas desulfurization process, and the vast majority of sulfur produced is produced this way,o Mr. Bole­bruch said when queried about the best way to reduce sulfur content in feedstocks. oHaving said that, it depends on how much additional sulfur is being removed. There are other ways to process small incremental amounts of acid gas, and that might be changes in catalyst chemistry, tail gas configuration, the use of oxygen and the addition of non-Claus chemical processing.o
Mr. BolebruchEs industry experience and time in the field have shown him that that there are ways to increase the rate of hydrodesulfurization without the need to add an additional Claus train. When describing one successful sulfur reduction technique that he implemented, Mr. Bolebruch said, oThe refinery often generates a sour-water stripper offgas stream, and an instrumented furnace showed a 50% increase in the ability of the furnace to accept and destroy the ammonia contained therein. This also buys the refiner considerable additional capability without additional capital cost and the time required to build a new train. So, in a nutshell, we can allow refiners to push more product into the reaction furnace, and therefore accept considerably higher quantities of product from the hydrodesulfurization area.o
Refineries are often configured to process a particular type of crude, depending on geographical location, financial considerations and ease of access to a particular oil field. Fig. 1 shows the sulfur content of the worldEs most prevalent crudes, from most sour to sweetest, based upon the API gravity scale. Sulfur treatment plans are correspondingly designed according to the sour or sweet nature of the crude processed.FIG. 1. Density and sulfur content of selected crude oils.
oIn general, the more sour the crude, the larger the Claus train has to be to process the acid gas generated,o Mr. Bolebruch said. He went on to point...