Hydrogen sulfide treatment

Hydrogen sulfide treatment (Part 1)

Introduction

In nature, the production of hydrogen sulfide is mainly related to volcanic activity. In addition, it is also scattered in mineral springs, lakes, swamps, sewers and fertilizer pits, especially when protein decays. In industrial production, hydrogen sulfide mainly comes from energy addition processes such as natural gas purification, petroleum refining, coking and gas generation; among them, the concentration contained in natural gas purification and petroleum refining tail gas is higher and the total amount is the largest. Secondly, it is also produced in chemical industries such as sulfide dyes, artificial fibers, carbon disulfide, and in light industrial production such as medicine, pesticides, papermaking, and leather making. Although the total amount is small, the concentration is often very high. It is a serious environmental pollution and a harm to health, and must be controlled.

Hydrogen sulfide is produced in natural gas purification, petroleum refining, and production processes such as gas making, leather making, pharmaceuticals, papermaking, and synthetic chemical fibers. Hydrogen sulfide is one of the main pollutants in the atmosphere. It not only harms human health, but also seriously corrodes equipment. Desulfurization methods are basically divided into two categories: dry method and wet method.

Brief History

Hydrogen sulfide treatment started early. In 1809, Clegg of the United Kingdom used lime purifiers for desulfurization. In 1849, Lanning and Hills of the United Kingdom obtained a patent for the dry iron oxide method. In 1870, the United States developed a method for preparing iron oxide. This dry iron oxide method has been used in the field of desulfurization for 100 years. In the 1930s and 1940s, the solution method appeared, and iron hydroxide was suspended in alkaline solution for desulfurization. Since the 1950s, the ammonia method has been widely used in Western Europe. In the 1960s, the arsenic alkali method appeared, using arsenide as a catalyst. Because arsenide is highly toxic, it has gradually been replaced by non-toxic catalysts. For example, the hydroquinone method, A.D.A. method, Fumax method, and Dakehax method all use non-toxic catalysts. These methods are technologies that have developed rapidly in recent years. On the other hand, the technology of absorbing waste liquid treatment in the solution method has also been continuously developed, forming different desulfurization industries.

Dry method

Including iron hydroxide method, activated carbon method, Claus method and zinc oxide method.

1. Ferrohydroxide: Mix iron filings and wet sawdust thoroughly, add 0.5% calcium oxide, and make a desulfurizer with a humidity of 30~40%. Hydrogen sulfide reacts with the desulfurizer and is removed, and the regenerated ferric hydroxide can continue to be used. The reaction is as follows:

2Fe(OH)₃ 3H₂S-→Fe₂S₃ 6H₂O

2Fe₂S₃ 6H₂O 3O₂-→4Fe(OH）₃6SThis method has high desulfurization efficiency and is suitable for purifying gases with low hydrogen sulfide content, but the equipment occupies a large area, the desulfurizer must be regenerated and replaced regularly, and the operating conditions are poor. Therefore, it has gradually been replaced by the wet method, or combined with the wet method for deep desulfurization.

2. Activated carbon method: Use activated carbon to adsorb hydrogen sulfide, pass oxygen to convert it into monomer sulfur and water, use sulfide amine to wash away the sulfur, and the activated carbon can continue to be used. This method is not suitable for gases containing tar.

3. Claus method: First, oxidize 1/3 of hydrogen sulfide into sulfur dioxide, and then react it with the remaining hydrogen sulfide in the converter to produce high-quality molten sulfur directly from the gas phase.

4. Zinc oxide method: Granular zinc oxide reacts with hydrogen sulfide to produce zinc sulfide and water. It is mainly used to purify waste gas with low hydrogen sulfide content. This method is highly efficient, but not economical.