Sulfur removal in petroleum refining: Addressing process gas desulfurization.

Carlos Alvarez.

September 8, 2023

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Author: Ing. Carlos Álvarez, September 8, 2023.

Introduction

Elimination of sulfur in gases is key to mitigating environmental pollution. Oil refining is an industry that plays a critical role in the production of a variety of products, from gasoline and diesel to plastics and chemicals. However, crude oil extracted from the ground contains a number of impurities, among which sulfur is one of the most problematic.

Sulfur in crude oil and its byproducts can have harmful effects on health and the environment, making process gas desulfurization an essential step in the refining process. In this article, process gas desulfurization in petroleum refining, its importance, methods and associated challenges will be explored in detail.

1. Importance of sulfur removal in oil refining

1.1. Problems associated with sulfur

Sulfur present in crude oil and its byproducts can cause a number of problems:

Environmental impact: The combustion of products with high sulfur content, such as diesel and fuel oil, releases sulfur oxides (SOx) into the atmosphere, which contributes to the formation of acid rain and negatively affects air quality.
Human health: SOx are irritants to the human respiratory system and may contribute to respiratory diseases such as asthma.
Damage to equipment and processes: Sulfur can corrode equipment and pipes in refining facilities, increasing maintenance costs and the likelihood of failure.

1.2. Environmental regulations

Due to the aforementioned problems, governments and regulatory bodies around the world have established stricter regulations to limit sulfur emissions in petroleum products. These regulations, such as the Euro 6 standard ¹ for vehicles and the International Maritime Organization’s MARPOL regulations ² , have driven the need for process gas desulfurization in petroleum refining.

2. Gas desulfurization methods

There are several methods to carry out gas desulfurization in petroleum refining ^3,4 , each with its own advantages and disadvantages. Below are the most common methods:

2.1. Desulfurization by hydrotreatment

The hydrotreating desulfurization process is an essential technique in the petroleum industry to remove sulfur from fuels, reducing environmental pollution. In this process, crude oil or its derivative is combined with hydrogen in the presence of a catalyst at high temperature and pressure. Hydrogen reacts with sulfur compounds in petroleum, converting them into non-toxic compounds. This produces cleaner fuels and meets emissions regulations.

Advantage:

Efficient in reducing sulfur content to low levels.
It can be applied to a wide range of petroleum products.

Disadvantages:

Significant hydrogen consumption.
High operating and maintenance costs.
Generation of H ₂ S, which must be managed and disposed of safely.

2.2. Desulfurization by adsorption

The adsorption desulfurization process involves the use of adsorbent materials, such as zeolites or activated carbons, to remove sulfur compounds from flue gases or petroleum products. These materials have a high affinity for sulfur and retain sulfur compounds in their porous structure. As gases pass through the adsorbent, sulfur is selectively adsorbed, leaving a cleaner product. The adsorbent is then regenerated, releasing the sulfur and allowing it to be reused. This method is effective in reducing sulfur emissions and complies with environmental regulations.

Advantage:

Lower hydrogen consumption compared to hydrotreatment.
Can be adapted for small scale process gas desulfurization

Disadvantages:

It requires a regeneration process that consumes energy and can be expensive.
Less efficient than hydrotreatment in removing sulfur.

2.3. Oxidation desulfurization

The ^5- oxidation desulfurization process is used to remove sulfur from fossil fuels and other chemicals. In this process, the sulfur compound is reacted with oxygen or an oxidizing agent, transforming the sulfur compounds into sulfur dioxide (SO2) or similar compounds. The SO ₂ is then removed by absorption or washing techniques. This method is effective, but can generate unwanted by-products and requires careful management of the generated by-products, such as SO ₂ , to avoid environmental contamination.

Advantage:

It is an economical option for the desulphurization of process gases in small installations.

Disadvantages:

It generates toxic SOx waste that must be treated appropriately.

Less efficient at removing sulfur than other methods.

3. Challenges in gas desulfurization

Process gas desulfurization presents several challenges that the industry must address:

3.1. Selectivity

Achieve adequate selectivity in desulfurization to avoid excessive removal of other valuable compounds present in petroleum products.

3.2. Costs

Desulfurization methods, especially hydrotreating, can be expensive due to hydrogen consumption and high maintenance costs.

3.3. toxic waste

The generation of toxic waste, such as H2S and SOx, raises environmental and safety concerns that must be appropriately addressed.

3.4. Regeneration of adsorbents

In the case of adsorption desulfurization, the regeneration of adsorbents is a critical, energy-consuming process that requires continuous attention.

4. Conclusions

The desulfurization of process gases in oil refining is a stage to comply with environmental regulations and guarantee cleaner and safer products. Although presenting challenges, the refining industry continues to research and develop new technologies to address these issues efficiently and profitably. The search for more effective and sustainable desulfurization methods remains an area of ongoing interest for the industry, and it is expected that significant progress will be made in this field in the future.

The importance of desulfurization cannot be underestimated, as it has a direct impact on the quality of the air we breathe, public health and environmental sustainability. As conscious consumers, it is essential to understand