Desulfurization

Techniques and significance in reducing sulfur content

You can find more information on our web, so please take a look.

Desulfurization or desulphurisation refers to the systematic removal of sulfur contaminants from materials such as fuel. This can be achieved by either eliminating sulfur from individual molecules (e.g., A=S → A:) or extracting sulfur compounds from a blend like that found in oil refinery streams. ¹

This process is vital both industrially and environmentally as it supports the production of the majority of sulfur used commercially (Claus process and Contact process) and facilitates the development of sulfur-free substances. Furthermore, it mitigates the emission of detrimental sulfur compounds, primarily sulfur dioxide (SO2), into the atmosphere, reducing the risk of acid rain.

Common methods of desulfurization include hydrodesulfurization, the SNOX process, and the wet sulfuric acid process (WSA process).

Additional Insight into Desulfurization Techniques

Advanced Application: Desulfurizing Organic Mixtures with Hydrodynamic Cavitation

Initial experiments focused on determining the cavitation inception point, relying on pressure drop measurements against flow rate within a two-phase mixture of an organic solvent and water. Notably, a low pressure drop across a vortex diode indicated the beginning of cavitation, uncovering that cavitation inception for an octanol-water mix (up to 10% volume of octanol) occurs just before a 0.5 bar pressure drop. Further tests were conducted under pressure drops of 0.5 bar and 2 bar.

Cavitation Inception Assessment; (a) Solvent effects; (b) Pressure drop calculations; (c) Predictive modeling based on deviations from standard behavior.

For competitive pricing and reliable delivery, CHIDA is committed to being your ideal supplier and partner.

The controlled sulfur content in the organic phase (e.g., octanol) was adjusted to a specified level (e.g., 300 ppm) by incorporating a precise amount of thiophene. The solvent containing thiophene was then mixed with water to create a biphasic mixture with organic fractions of 2.5% and 10%. We measured the sulfur content over time. These experiments revealed significant insights into the influence of various parameters on the desulfurization process.

Influence of Pressure Drop, Initial Concentration, and Volume Fraction

The developed process signifies that parameters like pressure drop, initial sulfur concentration, organic volume fraction, and the nature of the organic solvent are crucial. As illustrated in Figure 4, high pressure drops lead to an increased number of cavities and more effective cavitation. However, low initial sulfur concentrations yielded better desulfurization results, especially with higher organic phase ratios.

Impact of Different Parameters on Desulfurization by Hydrodynamic Cavitation; (a) Pressure drop effects; (b) Initial concentration influences; (c) Varying volume fractions.

The initial concentration of sulfur and the efficacy of this method at low-pressure drops are essential for commercial viability. The conventional hydrodesulfurization process struggles to reduce sulfur below 350 ppm, but our method successfully addresses sulfur removal from concentrations up to 500 ppm at a minimal cost.

It's also worth noting that thiophene's low solubility in water prevents its physical transfer to the aqueous phase. Comparisons with stirred tank experiments without cavitation reaffirmed that hydrodynamic cavitation, not vigorous contact with the aqueous phase, accounts for sulfur removal.

Necessity of Cavitation for Sulfur Reduction; (a) Cavitation-based sulfur removal (Initial S: 300 ppm); (b) FTIR spectra of aqueous phase post-cavitation.

Full-size image

Known for generating hydroxyl radicals through water molecule cleavage, hydrodynamic cavitation is effectively employed for organic degradation. The proposed mechanism likely involves radical-induced cleavage of sulfur bonds and oxidation to sulfur dioxide. Alternative products such as sulphones may form but remain in the aqueous phase, facilitating sulfur removal.

This non-catalytic oxidative desulfurization method operates without conventional catalysts, suggesting the potential formation of substances like SO2 or HSO3. The process effectiveness for different organic solvents indicates a sophisticated mechanism needing further investigation.

Proposed Cavitation Oxidation Mechanism for Desulfurization.

Full-size image

Desulfurization in Diesel

For practical applications in fuel processing, commercial diesel with an initial sulfur content of 30 ppm was tested. Additional sulfur was introduced using thiophene, and cavitation tests indicated significant sulfur removal, particularly at higher pressure drops. The method demonstrates efficacy in rendering transportation fuels sulfur-free.

Comparison of Deep Desulfurization Results Using Commercial Diesel; (a) Commercial diesel analysis; (b) Results compared with other organic solvents.

This technique can be scaled for large operations, making it ideal for reducing sulfur content in various organic streams efficiently.

If you want to learn more, please visit our website Desulfurizer.