Automation to the rescue

Unfortunately, that is typically not the case.

Thankfully, the great minds driving innovation and resourcefulness have been able to deal with one of these undesired compounds, sulfur, which is so often present in the form of hydrogen sulfide. On its own, elemental sulfur is not an issue; it is one of the most common elements (by mass) on Earth, and is essential to life. It is present in living organisms (including humans); can be used in fertilizer production; and even has medicinal applications.

However, sulfur can also be harmful to both humans and the environment. Hydrogen sulfide (H₂S) concentrations of just a few parts per million (ppm) in ambient air can lead to illness, and even death at sustained levels greater than 500 ppmv. Sulfur dioxide (SO₂) is also toxic to humans at very low concentrations, and has received significant attention based on its negative impacts to the environment − specifically the destruction of vegetation and wildlife, and contribution to the production of acid rain. This has historically been the main reason for jurisdiction to ensure the oil and gas industry limits SO₂ emissions and recovers sulfur as elemental sulfur.

It is well known that hydrocarbon processing and refining, as well as other industrial processes, create and release H₂S and SO₂, and these emissions are globally regulated. Operational facilities that are known to generate H₂S and SO₂ will install sulfur recovery units (SRUs) to treat these two compounds and, specifically, remove the valuable sulfur. In other words, they ‘recover’ the sulfur, allowing it to be used safely in other industries. The recovery of the elemental sulfur is accomplished by using the modified Claus process with a variety of different tail gas technologies depending on the allowable SO₂ emissions. The capacity of modern SRUs can range from tens to thousands of tons per day of sulfur, typically at recovery efficiency rates at or above 96%, but may be as high as 99.99%.

In an SRU, the modified Claus unit consists of a main burner, thermal reactor (reaction furnace), sulfur condensers, heaters, and catalytic converters. It is in the modified Claus unit that the H₂S (and other sulfur compounds) is reacted, first thermally and then catalytically, in order to recover elemental sulfur.

This article was originally published in the October 2023 issue of Hydrocarbon Engineering magazine. To read the full article, sign in or register for a free subscription.

Written by Michael Gaura, AMETEK Process Instruments, USA.

Read the article online at: https://www.hydrocarbonengineering.com/special-reports/05102023/automation-to-the-rescue/