Disulfide Additives for Cracking Reactor Coke Inhibition
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Solution Overview
Problem
The rapid formation of coke deposits on the internal walls of hydrocarbon cracking reactors and heat exchangers leads to frequent shutdowns, increased maintenance costs, and reduced operating time due to the limitations of existing coke inhibition methods, particularly the thermal decomposition of sulfur-based additives which reduce olefin yields.
Innovation Solution
The use of diethyl disulphide (DEDS), dipropyl disulphide (DPDS), or dibutyl disulphide (DBDS) as coke and carbon monoxide inhibitors, which are added to the steam or feedstock, pretreat the metal surfaces at specific temperatures to reduce coke formation and increase olefin yields by minimizing thermal decomposition into methane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If sulfur-based additives (DMS, DMDS) are used to reduce coke formation, then coke deposition is reduced, but thermal decomposition reduces olefin yields
Solution Approach 1:
The patent changes the chemical structure parameter of the sulfur-based additive by using dibutyl disulfide (DBDS) instead of conventional DMS or DMDS. This structural modification alters the thermal decomposition pathway to reduce methane formation and increase olefin yield while maintaining coke inhibition effectiveness.
Solution Approach 2:
The patent creates an alternative copy of the sulfur-based additive mechanism by using dibutyl disulfide, which replicates the coke-inhibiting function through sulfur release but produces a different decomposition profile that favors olefin production over methane formation.
2Object-generated harmful factors
If high-temperature gasification is used to remove coke deposits, then coke is converted to carbon oxides, but structural limitations prevent in-line decoking in heat exchangers
Solution Approach 1:
The patent applies preliminary protective action by introducing dibutyl disulfide additive into the hydrocarbon feed before it enters the cracking reactor and heat exchangers. This preventive approach forms a protective layer on metal surfaces that inhibits coke formation in the first place, eliminating the need for subsequent high-temperature decoking operations.
3Object-generated harmful factors
If oxidizing decoking treatment is performed, then coke is removed, but catalytic activity of metal surface increases leading to faster coke formation
Solution Approach 1:
The patent converts the potentially harmful effect of sulfur (which can poison catalysts) into a beneficial effect by using controlled amounts of dibutyl disulfide that passivate the metal surface to prevent coke formation. The sulfur acts as a protective agent rather than a contaminant, extending operating time between decokings.
4Object-affected harmful factors
If conventional sulfur additives are used, then coke formation is reduced, but frequent shutdowns are still required for maintenance
Solution Approach 1:
The patent changes the physical and chemical parameters of the sulfur additive by using dibutyl disulfide with higher molecular weight and different thermal stability characteristics. This results in more stable and durable coke inhibition that lasts through longer operating periods, reducing the frequency of maintenance shutdowns.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These additives effectively reduce coke and carbon monoxide formation, increasing the yield of olefins like ethylene, propylene, and butene by stabilizing the metal surfaces and preventing methane production, thus enhancing the operational efficiency and reducing maintenance needs.
Implementation Method 1
the sulphur passivates the active metal sites of the surface of the steam cracking tubes which are known to catalyze the formation of coke
Implementation Method 2
compounds which generate hydrogen sulphide (H2S) in order to reduce the formation of coke
Implementation Method 3
the metal surfaces coming into contact with the organic substance to be cracked are pretreated with a stream of steam comprising in particular the additive according to the invention
Data Source
AI summary
The present invention concerns an additive for reducing the formation of coke and/or carbon monoxide in thermal hydrocarbon cracking units and/or of other organic compounds in heat exchangers. The additive according to the invention is essentially composed of diethyl disulphide (DEDS) or dipropyl disulphide(s) (DPDS) or dibutyl disulphide(s) (DBDS) and can be used on the metal walls of a cracking reactor and on the metal walls of a heat exchanger placed downstream from the cracking reactor, and during the process of cracking hydrocarbons and/or other organic compounds.