Oxidative destruction of monocyclic and polycyclic aromatic hydrocarbon (PAH) contaminants in sulfur recovery units

Rahman, Ramees K.; Ibrahim, Salisu; Raj, Abhijeet

doi:10.1016/j.ces.2016.08.027

Cited by 43 publications

(40 citation statements)

References 28 publications

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“…They decompose to form important species in the furnace such as H, OH, SO, SH, H 2 S, and SO 2 . Their reactions are included in the detailed Claus furnace mechanism, developed in our previous study …”

Section: Resultsmentioning

confidence: 99%

“…Such reactions are present in the detailed Claus mechanism developed in Ref. having 1900 reactions considering the detailed sulfur chemistry. It also includes the reactions of S and SO that are discussed in Refs.…”

Section: Resultsmentioning

confidence: 99%

“…While this article only focusses on the oxidation of xylene radicals by SO 2 , the species such as S and SO can also potentially react with the aromatic radicals. Through Claus furnace simulations using the detailed mechanism with typical feed conditions, it is found that the short‐lived S and SO radicals are present in very low concentrations throughout the furnace (the maximum mol fractions of S and SO being lower than that of SO 2 by more than 4 and 2 orders of magnitude, respectively), as S readily forms S 2 , and SO forms SO 2 . Thus, they are not available to react with the aromatic radicals that are also present in very small concentrations (ppm level).…”

Section: Resultsmentioning

confidence: 99%

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Reaction mechanism and modeling study for the oxidation by SO₂ of o‐xylene and p‐xylene in Claus process

Sinha

Raj²

2017

Int J of Quantum Chemistry

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Claus process, comprising of a furnace and a catalytic unit, is used to produce sulfur from H2S. The aromatic contaminants (benzene, toluene, and xylenes) in H2S feed form soot, and clog and deactivate the catalysts. Xylenes are known to be the most damaging ones. Therefore, there is a need to oxidize them in the furnace to enhance catalyst life. This article presents a kinetics study on the oxidation of o‐ and p‐xylene radicals by SO2 (an oxidant that is already present in the furnace) using density functional theory and a composite method. The mechanism begins with H‐abstraction from xylenes to form xylyl radicals, followed by exothermic addition of SO2 to them. The breakage of OS bond in the xylyl‐SO2 adducts leads to the loss of SO molecule, while the remaining O atom on them helps in their oxidation. The isomerization study shows that less‐stable dimethylphenyl radicals have a high tendency to isomerize to resonantly stabilized methylbenzyl radicals. However, methylbenzyl radicals have lower reactivity toward SO2 than dimethylphenyl radicals. The reaction rate constants were found using transition state theory. The reactor simulations reveal that p‐xylene has lower reactivity toward SO2 than o‐xylene, and CO, SO, and CHO are the main by‐products of oxidation.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Reaction mechanism and modeling study for the oxidation by SO₂ of o‐xylene and p‐xylene in Claus process

Sinha

Raj²

2017

Int J of Quantum Chemistry

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“…and Abián et al . was merged with a mechanism for the oxidation and pyrolysis of H 2 S, CO 2 , hydrocarbons, and other chemical species found in Claus feed . The addition of COS/CS 2 submechanism led to an underprediction of COS production when compared to a plant data .…”

Section: Introductionmentioning

confidence: 99%

“…was merged with a mechanism for the oxidation and pyrolysis of H 2 S, CO 2 , hydrocarbons, and other chemical species found in Claus feed . The addition of COS/CS 2 submechanism led to an underprediction of COS production when compared to a plant data . The assumption that the highly sensitive reaction of COS with O proceeds in a single step, and the use of estimated rate parameters for it may not be valid in a complex Claus furnace (where several active species react simultaneously) and over a range of conditions.…”

Section: Introductionmentioning

confidence: 99%

A reaction kinetics study and model development to predict the formation and destruction of organosulfur species (carbonyl sulfide and mercaptans) in Claus furnace

Rahman

Raj

2018

Int J of Chemical Kinetics

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Carbonyl sulfide (COS), carbon disulfide (CS 2 ), and mercaptans (e.g., CH 3 SH) are unwanted sulfurous species that are produced in sulfur recovery units (SRUs). They can cause equipment corrosion, reduce catalyst activity, and are pollutants for the environment. This necessitates process optimization to minimize their formation in the SRUs using an accurate kinetic model. In this paper, new reactions of COS and mercaptans are studied using the CBS-QB3 level of theory, and their kinetics are evaluated using transition state theory. Such reactions are added to a detailed SRU reaction mechanism, and the updated mechanism is validated using the data on COS and mercaptans from lab-scale experimental setups and an industrial plant. Compared to the previous models, significant improvements in the predicted concentrations of the important species such as COS, carbon monoxide (CO), and sulfur oxides (SO and SO 2 ) are observed due to the inclusion of the new reactions in the mechanism. The simulation studies in a homogeneous reactor within the temperature range of 800-2000 K revealed that furnace temperatures near 1300 K are required to minimize CO and COS formation, while ensuring the oxidation of methane (CH 4 ), mercaptans, and aromatics. Mercaptan formation mainly took place at low temperatures near 900 K.Claus furnace simulations are conducted using industrial feed and operating conditions to show that the optimized inlet air temperature and fuel gas flow rate can assist in simultaneously reducing the emissions of CO and harmful sulfurous species such as COS, CH 3 SH, and CS 2 from the furnace.

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A detailed reaction mechanism for elemental sulphur combustion in the furnace of sulphuric acid plants

2021

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Elemental sulphur combustion is traditionally used to generate SO2 to produce sulphuric acid that is consumed in chemical industries, but is now also being considered as an energy vector for power generation. Despite the fact that sulphur combustion has been practiced for decades, there are limited reaction mechanisms for its combustion chemistry, which is critical for the optimization of the sulphuric acid production process to maximize efficiency and reduce cost. In this paper, a detailed reaction mechanism is developed and validated with different sets of experimental data from lab‐scale and industrial plant studies. The reaction mechanism is used to conduct sulphur furnace simulations, where the effects of feed air/sulphur ratio and oxygen enrichment of air stream on furnace temperature and the concentrations of SO2, SO3, and O2 are investigated. The dominant reaction pathways in sulphur combustion, particularly for the production of SO2 and SO3, are identified. It was found that the feed air/sulphur ratio monitors the furnace temperature and can be used to obtain the desired O2/SO2 ratio at the furnace exit for the optimal operation of catalytic converter (for SO2 oxidation to SO3) that follows the furnace in the sulphuric acid plant. Moreover, high oxygen enrichment above 35% (while maintaining the desired O2/SO2 ratio at the furnace exit) significantly increased the furnace capacity through reduced total gas flow (thus decreasing blower energy requirement and equipment size). The developed reaction mechanism provides a method to obtain optimized furnace parameters to achieve high efficiency and reduced costs in sulphuric acid plants.

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Oxidative destruction of monocyclic and polycyclic aromatic hydrocarbon (PAH) contaminants in sulfur recovery units

Cited by 43 publications

References 28 publications

Reaction mechanism and modeling study for the oxidation by SO₂ of o‐xylene and p‐xylene in Claus process

Reaction mechanism and modeling study for the oxidation by SO₂ of o‐xylene and p‐xylene in Claus process

A reaction kinetics study and model development to predict the formation and destruction of organosulfur species (carbonyl sulfide and mercaptans) in Claus furnace

A detailed reaction mechanism for elemental sulphur combustion in the furnace of sulphuric acid plants

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Oxidative destruction of monocyclic and polycyclic aromatic hydrocarbon (PAH) contaminants in sulfur recovery units

Cited by 43 publications

References 28 publications

Reaction mechanism and modeling study for the oxidation by SO2 of o‐xylene and p‐xylene in Claus process

Reaction mechanism and modeling study for the oxidation by SO2 of o‐xylene and p‐xylene in Claus process

A reaction kinetics study and model development to predict the formation and destruction of organosulfur species (carbonyl sulfide and mercaptans) in Claus furnace

A detailed reaction mechanism for elemental sulphur combustion in the furnace of sulphuric acid plants

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Reaction mechanism and modeling study for the oxidation by SO₂ of o‐xylene and p‐xylene in Claus process

Reaction mechanism and modeling study for the oxidation by SO₂ of o‐xylene and p‐xylene in Claus process