Section 1: Principle of Dry Desulfurization (Desulfurization Tank) Process

Dry desulfurization involves filling a cylindrical desulfurization tower with a certain height of desulfurizing agent. Through the desulfurizing agent, H2S is removed, achieving the desulfurization process. The commonly used desulfurizing agent is iron oxide, which is in a cylindrical granular form. As it is continuously produced, iron oxide absorbs H2S. When the absorption of H2S reaches a certain amount, the removal rate of H2S will significantly decrease, eventually becoming ineffective.

Section II: Dry Desulfurization Performance

The basic principle of dry gas desulfurization equipment (H2S) involves using O2 to oxidize H2S into sulfur or sulfur oxides, also known as dry oxidation method. The composition of the dry equipment consists of placing a packing material, such as activated carbon and iron oxide, inside a container. The gas flows at a low velocity through the packing layer within the container, where (H2S) is oxidized into sulfur or sulfur oxides, remaining in the packing layer. The purified gas is then discharged from the other end of the container.

Section 3: Product Construction Description

1. This equipment is made of stainless steel.

2. Desulfurization Filler - Ferric Oxide Desulfurization Agent

Section 4: Filling Material Description

Desulfurizing agent is an efficient purifying agent mainly composed of ferric oxide, with additional promoters added for processing and shaping. Under normal temperatures, it exhibits high desulfurization performance for gases, and also has a certain degree of removal effect on organic sulfur compounds like thioles and most nitrogen oxides.

It features simple equipment, easy operation, high purification efficiency, low bed resistance, and strong practicality, with no secondary pollution.

5. Desulfurization and Regeneration Principle

Desulfurization:

Fe2O3·H2O + 3H2S = Fe2O3·HO + 3H2O + 15 kcal

Recycling: Fe2O3·H2O + 2O2 = Fe2O3·H2O + 3S + 145 kcal

If the ratio of O2 molecules to H2S molecules in the gas is greater than 2.5, the aforementioned desulfurization and regeneration reactions can be continuously regenerated, in which case the two reactions can be combined into: H2S + 2O2 = Fe2O3·H2O + H2O + S, with iron oxide acting as a catalyst in actuality.

Section 6: Operation and Usage

Operation Conditions:

Air Speed: 200-400 h-1 (can be increased to 500-600 h-1 under pressurized conditions or low H2S content)

Line Speed: 0.10—0.3 meters/second (empty tower)

Pressure: Atmospheric Pressure

Temperature: Room temperature – 130℃ (optimal between 20-80℃)

The above moisture content and pH level:

The moisture in desulfurizing agents serves as a medium, with its content ideally being around 10% of the desulfurizing agent's weight. During use, a slight amount of moisture vapor is required to prevent the airflow from carrying away the moisture in the desulfurizing agent, but excessive steam should be avoided to prevent condensation and blockage of the micropores. The desulfurization and regeneration process is most effective when the pH value is between 7.5 and 9.0.

Section 7: Maintenance of Dry Desulfurization Vessel

Regularly test the concentration of O2 exiting the desulfurization tower; the oxygen content should be controlled below 1%.

2. Regularly test the H2S content before and after desulfurization, as well as the H2S content post-desulfurization. If the desulfurization efficiency falls below 90%, it indicates that the desulfurizing agent is nearing its sulfur capacity and has become ineffective. It's time to replace the desulfurizing agent. You can discharge some of the failed desulfurizing agent from the bottom of the desulfurization tower and replenish with new desulfurizing agent from the top. To ensure effective desulfurization, the amount of iron oxide in the desulfurization tower should ensure the ratio of reaction layer height to tower diameter is greater than 3-4.

3. To prevent excessive moisture content in the desulfurization tank, regular draining of the tank is required (open the bottom drain valve), recommended once a week.

Section 8: Recycle Operations

If the H2S content in the gas emitted from the desulfurization tower exceeds 1ppm or the required specification, and the sulfur tower has not reached 30%, then the desulfurizing agent should be regeneratd.

1. Regeneration Methods: They can be categorized into continuous and intermittent regeneration. Continuous regeneration can be achieved when the molar ratio of O2/H2S in the raw gas is high, and no special regeneration operation is required. If continuous regeneration is not possible due to a low O2 content in the raw gas, intermittent regeneration can be performed, generally involving the following methods:

(1) Natural Air Regeneration

(2) Forced air regeneration

(3) Inert Gas and Air Recirculation System

2. The regeneration process primarily controls the bed temperature between 30-80°C, not exceeding 90°C. Temperature control is mainly achieved by adjusting the oxygen content in the regeneration process. Natural air regeneration is primarily suitable for situations with less quantity and sulfur absorption. Its temperature control is mainly achieved by adjusting the gas flow, and if a sharp temperature increase is detected, the inlet valve should be immediately closed.

3. The regeneration time depends on the amount of sulfur absorbed; more sulfur absorption leads to a longer regeneration process; less sulfur absorption results in a shorter regeneration process.

4. The number of regeneration cycles is generally 2 to 3 times.

5. Indication of the End of Recycling

When the bed temperature does not rise and the import content is basically close, it can be considered that regeneration is complete. Close the inlet valve and integrate the desulfurization tower into the system or switch to standby.

Section 9: Precautions

1. Filling: The quality of desulfurization agent filling directly affects the effectiveness of use. Pay attention to the following points:

(1) First, lay two layers of wire mesh with openings less than 5mm on the grate of the desulfurization tower. Then, cover the mesh with a layer of broken coking pieces, 50mm thick with a diameter of 20-30mm.

(2) Due to dust generation during loading and unloading, screening is required prior to filling.

(3) Prior to loading, the volume must be marked with a high line. After reaching the predetermined height, level the material. However, no foot traffic on the desulfurizing agent; use wooden boards to support the material layer. For scooping and inspection, strictly prohibit foreign objects from being dropped inside the tower.

(4) The new desulfurizing agent has a lower strength, which increases progressively with the increase in sulfur absorption during the desulfurization process. Therefore, it should be filled in layers within the desulfurization tower, with each layer being approximately 1 to 1.5 meters in height.