Steam Cracking Sulfur Injection to Limit Carbon Disulfide in Pygas
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Solution Overview
Problem
Conventional steam cracking processes for producing olefins result in the formation of carbon disulfide and other sulfur-containing impurities, leading to out-of-specification product streams and downstream process issues.
Innovation Solution
Introduce hydrogen sulfide into the hydrocarbon cracking unit to replace organosulfur compounds, reducing the formation of carbon disulfide and other sulfur-containing impurities by passivating internal furnace coils and controlling carbon monoxide generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If organosulfur compounds (such as DMDS) are introduced to passivate internal coil surfaces and reduce coke formation, then the lifetime of furnace coils is extended, but sulfur-containing impurities (such as carbon disulfide) are formed during decomposition
Solution Approach 1:
The patent changes the chemical parameter of the sulfur compound from organosulfur (DMDS) to inorganic sulfur (H2S). This parameter change maintains the passivation function while eliminating carbon-containing sulfur impurities, as H2S decomposes to elemental sulfur without forming carbon disulfide.
Solution Approach 2:
The patent replaces the complex organosulfur compounds with simpler, more readily available H2S gas. While H2S has a shorter residence time in the system, it continuously provides sulfur for passivation without accumulating harmful byproducts, effectively serving as a disposable passivation agent.
2Quantity of substance
If organosulfur compounds are added to control CO concentration in downstream hydrogenation reactors, then the desired CO concentration is achieved, but carbon disulfide impurities increase in pygas streams
Solution Approach 1:
The patent changes the sulfur compound parameter from carbon-containing organosulfur to carbon-free H2S. This maintains CO control functionality while eliminating carbon disulfide formation, as the sulfur from H2S reacts with CO without introducing additional carbon.
3Reliability
If organosulfur compounds are used to reduce coke buildup, then coil lifetime is improved, but product streams become out-of-specification due to sulfur impurities
Solution Approach 1:
The patent changes the chemical composition parameter of the sulfur additive from organosulfur compounds to H2S gas. This parameter change ensures that sulfur is introduced without carbon, preventing carbon disulfide formation and maintaining product stream specifications while preserving coil protection.
4Ease of operation
If DMDS is introduced as a liquid at ambient temperatures for easy handling, then ease of operation is improved, but decomposition produces carbon disulfide and methyl mercaptan impurities
Solution Approach 1:
The patent replaces complex liquid organosulfur compounds with simple H2S gas that can be easily introduced and controlled. While H2S requires different handling procedures, it eliminates harmful decomposition products and can be precisely dosed as a disposable sulfur source.
Solution Approach 2:
The patent changes the physical and chemical parameters of the sulfur compound from liquid organosulfur to gaseous H2S. This parameter change trades some handling complexity for complete elimination of carbon-containing impurities, as H2S decomposes cleanly to elemental sulfur.
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
Reduces the concentration of carbon disulfide in pygas streams to below 50 ppmw, preventing out-of-specification product streams and improving downstream process operation.
Implementation Method 1
sulfur in the form of organosulfur compounds, such as dimethyl disulfide (DMDS), dimethyl sulfide (DMS), diethyl disulfide (DEDS), diethyl sulfide (DES), methyl mercaptan (MM), or combinations thereof, are often introduced to the steam cracking unit to passivate the internal coil surface to reduce coke formation on the internal furnace coils
Implementation Method 2
hydrocarbon cracking (e.g., steam cracking) may be used to produce olefins from a hydrocarbon stream
Implementation Method 3
Acetylene and other impurities and byproducts can be removed from an olefin-containing hydrocarbon cracking effluent through selective hydrogenation
Data Source
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AI summary
Methods for producing olefins through hydrocarbon steam cracking include passing a hydrocarbon feed that includes one or more hydrocarbons to a hydrocarbon cracking unit and passing one or more sulfur-containing compounds to the hydrocarbon cracking unit. The sulfur-containing compounds include at least hydrogen sulfide gas, and a flow rate of the sulfur-containing compounds to the hydrocarbon cracking unit is sufficient to produce a molar concentration of elemental sulfur in the hydrocarbon cracking unit of from 10 ppm to 200 ppm. The methods include cracking the hydrocarbon feed in the hydrocarbon cracking unit to produce a cracker effluent and contacting the cracker effluent with a quench fluid in a quench unit to produce at least a cracked gas and a first pygas. The first pygas has a concentration of carbon disulfide less than 50 ppmw based on the total mass flow rate of the first pygas.