DMDS in Steam Cracking: Coke Control and Furnace Tube Passivation

Its effectiveness depends on the feedstock, furnace metallurgy and treatment strategy. DMDS should therefore be selected and applied according to the requirements of the specific installation.

Why Is Coke Formation a Problem in Steam Cracking?

Steam cracking produces light olefins, including ethylene, by breaking down hydrocarbons at high temperatures. Alongside the desired reactions, carbonaceous deposits can accumulate inside the furnace coils.

Coke buildup creates several operating challenges:

• Reduced heat transfer through the tube wall.

• Increased resistance to flow and pressure drop.

• Shorter operating periods between decoking operations.

• Additional thermal stress and concerns about equipment condition.

Coke control is consequently an important part of furnace operation and maintenance planning.

How Does DMDS Passivate Furnace Tube Surfaces?

Under steam-cracking conditions, DMDS produces sulfur species, including hydrogen sulfide (H₂S). These interact with the metal surface inside the cracking tubes.

This interaction modifies the surface and suppresses the activity of metal sites involved in unwanted reactions. The effect is commonly described as surface passivation.

For this application, the objective is to reduce the metal surface’s contribution to coke and CO formation. It is not equivalent to applying a permanent protective coating, and it does not make the equipment immune to every form of deterioration.

Does DMDS Prevent All Coke Formation?

No. Steam-cracking coke forms through multiple mechanisms, and surface passivation addresses only part of that behavior.

Published research examining DMDS during hydrocarbon steam cracking found that its effect on coke formation depended on both the method of application and the amount used. The study also observed changes in coke morphology and the distribution of metals at the surface and within coke deposits.

These findings support a practical conclusion: DMDS treatment needs to be matched to the process rather than treated as a universal anti-coking solution.

What Is the Connection Between DMDS and Carbon Monoxide?

Carbon monoxide is another unwanted product of side reactions in steam cracking. Some of these reactions are promoted by the metal surface of the furnace tube.

By passivating relevant surface sites, sulfur treatment can help suppress CO formation. Experimental research on DMDS has reported reduced CO production under the conditions studied.

However, a reduction in CO does not by itself prove that the overall coking rate has decreased. Operators should evaluate both outcomes separately when assessing treatment performance.

What Determines Treatment Performance?

Several factors should be considered when evaluating DMDS for a steam cracker.

Research and technical reviews identify both the reactor material and sulfur-addition strategy as important variables. Published experimental results should not be transferred directly into a different furnace’s operating procedure.

How Should a Plant Assess the Results?

A useful evaluation compares performance under reasonably comparable feed and operating conditions. The process team can track:

• CO formation.

• Pressure-drop trends.

• Tube metal temperature trends.

• Furnace run length.

• Decoking frequency and inspection findings.

These indicators help distinguish a measurable treatment benefit from changes caused by feedstock or operating severity.

DMDS is used to manage deposit formation during operation. It should not be presented as a chemical cleaning agent for removing an existing coke layer or as a replacement for required decoking.

What Should Buyers Confirm Before Ordering DMDS?

A purchasing inquiry should include the plant’s approved raw material specification and receiving requirements.

Purity alone does not establish suitability. The complete specification should be reviewed by the plant’s technical team before a new supplier or grade is accepted.

Chemical supply and application services should also be discussed separately. Injection equipment, operating recommendations and on-site assistance should only be included when specifically agreed.

DMDS Supply from NBWCHEM

Gansu Nabowang Chemical Products Co., Ltd. manufactures 99.5% dimethyl disulfide (DMDS) in China, with a minimum order quantity of 1 metric ton.

Available packaging includes galvanized steel drums, IBC containers and ISO tanks. Shipments can be arranged through Tianjin or Qingdao Port, and third-party inspection before shipment is available.

For steam-cracking applications, provide your approved product specification, required quantity, packaging preference, destination port and delivery schedule. We can use these details to assess your supply requirements and prepare a quotation.

CONTACT US