Optimizing Claus Converters

This video is the third in the SRU Optimization mini series, which describes how to optimize the performance of each individual process unit, and covers 2 case studies from past testing experiences at SRE.

Claus Converters : Where the catalytic reaction occurs with the 2:1 H2S to SO2 ratio.
Exothermic reaction- Heat released/temperature rise in the catalyst bed.
Fully active catalyst will allow for ‘equilibrium’ of the Claus reaction to be reached.
The Claus reaction is favored at lower temperatures

The first converter always runs hotter in order to maximize hydrolysis of COS and CS2, which means converting these unwanted bi-products back to SO2. SRE recommends a temperature of 343 C for Alumina, and 315 C for Titania catalyst.
Downstream converters run cooler to maximize the Claus reaction. This means operating 10 degrees Centigrade above the sulfur dewpoint temperature, which is typically somewhere between 160 and 200.

There are a number of mechanisms that can cause catalyst deactivation. They include BTEX and methanol poisoning; sulfation; hydrothermal ageing; thermal ageing, and normal ageing.
• BTEX poisoning occurs when the RF is unable to completely destroy BTEX components in the acid gas feed stream(s) to the SRU. The resulting effect is a ‘cracking’ or ‘polymerizing’ of these components on the Claus catalyst.
• Methanol poisoning is normally due to an SRU with an acid gas by-pass that allows methanol to by-pass the RF.
Both of these deactivation mechanisms are permanent.
• Sulfation of catalyst occurs when excessive (and continuous) free oxygen is carried over from either the RF or direct-fired reheaters;
• Hydrothermal ageing results when the catalyst is exposed to excessive amounts of water vapor over a long period of time. Although the actual physical mechanism is still not completely understood, it can occur when either excessive steam is introduced into the process and may also occur due to serious tube or tubesheet leaks (BFW being on the shell side) from the Wasteheat boiler or Condensers.
• Thermal ageing is caused by ‘thermal excursions’ or ‘sulfur fires’ in the catalyst beds. Temperatures above 1300 F, which are all too easy to obtain during a serious sulfur fire, can result in ‘fusing’ of the catalyst into large solid pieces.
• Soot deposition and liquid sulfur deposition on the top of the catalyst, results in plugging of the converter beds is not considered a deactivation mechanism, but can be extremely problematic.

Optimizing the converters means taking measures to prevent these catalyst deactivation mechanisms from occurring. To prevent poisoning we have to clean up the feed streams and ensure the RF temperature is adequate for maximum destruction of contaminants. To prevent sulfation and carbon fouling, we have to optimize the burn strategys, or burn ratios, for the RF and any DFRs that may be in place. This minimizes free oxygen carryover, and prevents soot deposition. Then, to prolong the aging and general attrition of the catalyst, we have to optimize the temperature controls and keep up with maintenance and calibrations. Following the proper start-up and shutdown procedures is also key.

Thanks for watching! For more videos on sulfur recovery, subscribe to our page. Also visit our website http://sulfurrecovery.com/, and sign up for our monthly newsletter here: http://sulfurrecovery.com/Newsletter/

Видео Optimizing Claus Converters канала Sulfur Recovery Engineering Inc