desulfurization

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Technical characteristics of the wet oxidation desulfurization process and several issues worth paying attention to in normal operation I. Technical characteristics of the wet oxidation desulfurization process: H2S is an acidic gas that can ionize to release hydrogen ions in solution; H2S = H+ + HS-； Na2CO3 + H2S == NaHCO3 + NaHS. HS- possesses strong reducing properties and tends to lose electrons and be oxidized: HS- + 1/2 O2 == S↓ + OH-. This property is cleverly utilized in the wet oxidation process for sulfur removal. The wet oxidation process is essentially a wet acid-base neutralization process accompanied by an oxidation reaction; through catalytic oxidation, sulfur in the +2 valence state is converted into elemental sulfur, which is then separated out. Its process technology has the following characteristics. 1. It is crucial to select high-quality desulfurization catalysts: In the wet oxidation method for desulfurization, the oxidation of H2S to elemental sulfur is achieved through oxygen-carrying catalysts present in the desulfurization solution. The catalyst plays a significant role in determining a range of important parameters in the wet oxidation process, including the desulfurization efficiency, sulfur elemental production rate, alkali consumption, regeneration efficiency, and the yield of side reactions. Therefore, selecting a high-performance catalyst as the redox agent becomes key to determining the operation of this process. 2. Regardless of the catalyst used, the common characteristic of the chemical reaction process is that it takes place in three steps: in the first step, ammonia water or soda ash solution is used to absorb H2S from the gas to carry out a neutralization reaction. In the second step, a oxygen carrier catalyst is used to carry out a catalytic oxidation reaction to oxidize HS- and S-2 into elemental sulfur. In the third step, self-priming air is added or injected to oxidize and deactivate the catalyst, thereby regenerating it, restoring its activity, and enabling its reuse. At the same time, elemental sulfur is floated out and separated for sulfur smelting. Moreover, from a process perspective, the first absorption reaction must take place in the desulfurization tower. The gas and liquid phases are in counterflow contact, and through mass transfer (via the packing), H2S is transferred from the gas phase to the liquid phase, entering the liquid phase matrix. In an acid-base neutralization reaction, the corresponding salt is formed, which is then converted into rich liquid. In this process, it is a diffusion-type absorption controlled by an air film. However, the second set of chemical reactions involving catalysis, oxidation, and sulfur precipitation also take place primarily within the desulfurization tower. Thus, this complex pattern of coexistence among phases was also formed. Therefore, factors such as mass transfer area, spray density, liquid-to-gas ratio, alkalinity, pH value, catalyst concentration, and reaction temperature all affect the selectivity of absorption, as well as sulfur precipitation and regeneration and gas purity. 3. Jet regeneration process: In the nitrogen fertilizer industry, solution oxidation regeneration mostly makes use of regeneration tanks; this process is advanced and highly effective. The general process is as follows: the rich liquid exits from the bottom of the desulfurization tower and enters the rich liquid tank. After being pressurized by a regeneration pump, it passes through the injector nozzles, where it forms a jet and creates a local vacuum that automatically draws in air. At this point, the gas-liquid two-phase mixture is evenly distributed at high speeds and is in a highly turbulent state; after undergoing enhanced reaction in the contraction zone, throat, diffusion tube, and tail pipe, it forms a foam mixture that enters the regeneration tank for oxidative regeneration. Elemental sulfur flotation is carried out by evenly distributing the cuttings and flocs through a perforated plate distributor. That is, under the agitation caused by air, sulfur particles collide with each other and combine to form small sulfur clumps; these clumps aggregate to create a foam layer, which then overflows into the foam tank and is sent to the sulfur melting station. The clear liquid then enters the clear liquid circulation groove for secondary flotation (where a calm area is formed, which facilitates the aggregation and separation of bubbles), and is sent to the depleted liquid tank via a level regulator. At the same time, under the aeration effect of air, waste gases such as CO2 in the rich solution can be driven out, which reduces the suspended sulfur in the solution and increases its alkalinity, thereby enabling the various components to be adjusted and restored. As well as the oxygen absorption regeneration of the catalyst to restore its activity, thereby improving the quality of the solution and reducing residual sulfur content. Therefore, the liquid phase pressure of the injector, the amount of air, the blowing intensity, the reaction temperature, the residence time, the control of the foam layer, and overflow are all very important. Furthermore, the requirements for process equipment in absorption and regeneration involve inconsistent control parameters (some of which are even opposite to each other), and it is necessary to find an optimal balance. Therefore, the quality of the lean liquid after oxidation regeneration directly determines the desulfurization efficiency and its impact on the resistance in the desulfurization tower.