The effect of ammonia on HPF desulfurization

Thread Content

Ammonia has a significant impact on HPF desulfurization! The absorption of hydrogen sulfide involves the dissolution of H2S from the gas phase into the liquid phase, as well as the dissociation of H2S in the solution. When the partial pressure of H2S in the liquid phase at the interface reaches equilibrium with the partial pressure of H2S in the gas phase, it indicates that the process is complete. In the case of HPF desulfurization, the presence of free ammonia in the solution accelerates the dissociation of H2S, reducing the H2S partial pressure in the liquid phase at the interface and promoting dissolution from the gas phase into the liquid phase ； Until the ammonia in the liquid phase is converted into ammonium ions NH4+. However, when ions such as HCO3-, SCN-, and HSO3- with higher acidity than HS- are present in the solution, it increases the concentration of molecular H2S in the solution, raising the partial pressure at the liquid phase interface and thereby increasing the resistance to the absorption of hydrogen sulfide. When the concentration of active ammonia and the impurity content in the solution change, the solubility of hydrogen sulfide changes as well. The ammonia in aqueous ammonia solutions consists of volatile ammonia and fixed ammonium (free ammonia + weak acid salts). The fixed ammonium is mostly in the form of strong acid salts. The higher the concentration of acidic substances in the aqueous ammonia, the greater the amount of fixed ammonium. Since only free ammonia has the ability to absorb H2S, a high content of volatile ammonia does not necessarily guarantee the absorption capacity of the aqueous ammonia. By means of acid removal distillation using ammonia vapor and ammonia water, fixed ammonium is separated and volatile ammonia is decomposed, thereby increasing the amount of free ammonia, improving the quality of the ammonia water, and raising its free ammonia content. Determining the free ammonia content based on multi-directional data and adjusting operating conditions in a timely manner is useful for improving desulfurization efficiency. The desulfurization process for coke oven gas is both simple and complex. Its simplicity lies in the fact that there are not many key control points in desulfurization itself; by managing a few main control points, it is possible to take into account numerous factors, such as temperature. Proper temperature control has a direct impact on ammonia concentration, desulfurization efficiency, regeneration efficiency, the rate of by-product salt formation, and the system’s water balance ； The complexity lies in the fact that, in addition to desulfurization itself, the water and gas sources from the preceding processes have a significant impact on desulfurization, and the range of factors that need to be controlled is wide. For example, the proper operation of the ammonia evaporation system has a major effect on desulfurization; it influences not only the ammonia content but also the temperature of the desulfurization system, the quality of the desulfurization process, and the stability of the regeneration process. For the desulfurization of coke oven gas, new processes and technologies are emerging in large numbers these days. Facing the complexities associated with coke oven gas desulfurization, particularly regarding the matching of processes at the initial stages of desulfurization, new technical solutions are also needed.