Purifying Sodium Hydrosulfide: Background and Insights

In the petroleum and chemical industry, refinery processes such as vacuum distillation and catalytic cracking typically generate acidic gases. These acidic gases generally consist of 85%–95% hydrogen sulfide (H₂S), 3%–10% carbon dioxide (CO₂), 2%–5% organic gases, and 0.5%–3% other components.

Small and medium-sized refineries usually treat these acidic gases by absorbing them with a 30% sodium hydroxide (NaOH) solution. The NaOH reacts with H₂S to form sodium hydrosulfide (NaHS). When the NaHS concentration in the solution reaches 30%, the solution undergoes a concentration process. After dehydration and concentration, the NaHS content increases to 70%, and the molten NaHS is then sliced into flakes.

However, since the acidic gases contain CO₂, impurities such as sodium carbonate (Na₂CO₃) are generated during treatment, reducing the purity of the NaHS product.

Additionally, when open-drum flakers are used to slice molten NaHS, the NaHS tends to react with oxygen in the air, forming sodium thiosulfate (Na₂S₂O₃), which is prone to deterioration and difficult to store. Open slicing also releases irritating gases, polluting the production environment.

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