How to Optimize Valve Use in Sulfur Recovery Units

Overview

Sulfur recovery units are necessary to recover sulfur from acidic gases containing hydrogen sulfide during the refining process. These units use appropriate technologies to promote cleaner production, turn waste into treasure, reduce pollution and protect the environment.

Sulfur Recovery Process

Most sulfur recovery plants use the Klaus process. The process converts hydrogen sulfide (H₂S) in acid gas into elemental sulfur (S) through a series of high-temperature oxidation, catalytic conversion, and catalytic oxidation reactions. Basic steps include:

1. Absorbing H₂S from gas streams using solvents like ethanolamine.
2. Oxidizing a portion of the H₂S to sulfur and sulfur dioxide (SO₂).
3. Reacting the SO₂ with the remaining H₂S over an activated alumina catalyst to produce sulfur.

Sulfur is a key raw material for a variety of industries, including dye manufacturing, pesticides, matches, gunpowder, rubber and rayon production. With the expansion of the application range of sulfur products and the rise of market prices, sulfur recovery equipment is not only an environmental protection device for refineries, but also a profitable production device.

Valve Applications Overview

1. Raw Gas System

Feedstock gas systems process hydrogen sulphide rich gas, sometimes mixed with carbon dioxide. When water condenses, it creates a corrosive environment of h2s + h2o or h2s +CO 2 + h2o. Hydrogen sulfide is highly dangerous, so a valve with a good seal is required. Key considerations for selecting valves in feedstock gas lines include:

• Valve Materials: For pipelines prone to condensation, valve materials must comply with NACE MR0103 standards.
• Valve Types: Gate valves and globe valves with low emission designs are preferred for their reliable shutoff.
• Structure Design: Given the moderate pressure and temperature conditions, bolted bonnet valves with high-strength alloy steel bolts are suitable.

2. High-Temperature Conversion System

The system often encounters temperatures above 250°C and contains corrosive media such as hydrogen sulfide, sulfur dioxide and elemental sulfur. Key points include:

• Valve Materials: For pipes with medium temperatures higher than 240°C, carbon steel has an appropriate corrosion margin. For temperatures above 350°C, alloy steels such as 1Cr, 2Cr and 5Cr need to resist high-temperature sulfur corrosion..
• Valve Types: In order to handle liquid sulfur without leaving a residue, a jacketed valve must be installed. Plug and butterfly valves are superior to globe and gate valves because they do not easily form closed cavities and grooves.

3. Product Handling System

The product handling system focuses on the transportation and storage of liquid sulfur, and its valve requirements reflect the requirements of liquid sulfur pipelines in high-temperature conversion systems.

4. Tail Gas Treatment System

Although the exhaust contains unconverted hydrogen sulfide and other corrosive gases, the maximum temperature of the main process pipeline, except for the incinerator, is 310 ° C. Key considerations include:

• Valve Materials: For low temperature hydrogen sulfide corrosion, carbon steel has a large corrosion margin. Pressure components must comply with NACE MR0103 standards. For rich amine solutions (rich in hydrogen sulfide), use materials such as 304L or 316L, especially when chloride is present.
• Valve Types: Reliable shutoff valves with low emission designs are essential.

Conclusion

In sulfur recovery units, choosing the right valve is critical due to the presence of dangerous and corrosive media. The selection of materials, valve types and design considerations must be consistent with the specific conditions of each system to ensure safety, reliability and efficiency. By adhering to these standards, sulfur recovery units can efficiently convert waste into valuable products while minimizing environmental impact.

FAQs

1. What are the primary hazards of hydrogen sulfide in sulfur recovery units?
   • Hydrogen sulfide is highly toxic and corrosive, requiring valves with excellent tightness and corrosion resistance to ensure safety.
2. Why is the Claus process commonly used in sulfur recovery?
   • The Claus process efficiently converts hydrogen sulfide into elemental sulfur through high-temperature and catalytic reactions, making it a preferred method for sulfur recovery.
3. How do jacketed valves benefit liquid sulfur handling?
   • Jacketed valves prevent the formation of solid residues by maintaining a consistent temperature, ensuring smooth transportation of liquid sulfur.
4. What standards must valve materials meet in sulfur recovery units?
   • Valve materials must comply with NACE MR0103 standards to withstand the corrosive environments present in sulfur recovery processes.
5. Why is alloy steel preferred for high-temperature applications?
   • Alloy steels like 1Cr, 2Cr, and 5Cr resist high-temperature sulfur corrosion, making them ideal for applications where media temperatures exceed 350°C.