\"Equilibrium\" in the desulfurization process of coke oven gas”

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Chemical production emphasizes safe, stable operation over long periods of time; each process interacts with and affects the others, which makes stability and balance particularly important. Coke oven gas has a significant impact on its utilization due to its complex composition and numerous harmful impurities; therefore, it must be purified one by one. The hydrogen sulfide removal process is the most important step in gas purification. Whether it is the HPF technology or the complexed iron technology used for removing hydrogen sulfide from coke oven gas, achieving \"material balance\" is the key to ensuring the long-term stable operation of this process. In the wet oxidation method for desulfurizing coke oven gas, several types of \"balance\" need to be maintained: ① Sulfur balance: The amount of sulfur entering and leaving the system must be equal; it cannot accumulate within the system, as this could lead to serious problems such as tower blockages. This is the most fundamental requirement of this process, and it is closely related to the absorption of hydrogen sulfide, the separation of sulfur foam, and the treatment of sulfur foam. In the HPF technology, about 50% of the sulfur is converted into sulfur, while the remainder is converted into by-products. In contrast, with the iron-chelation technology, approximately 99% of the sulfur is converted into sulfur; thus, under the same operating conditions, the sulfur yield produced by this method is twice as high. Therefore, when using the iron-chelation technology, the impact on sulfur balance is particularly important. ②Water balance: As the name implies, the water entering and leaving the system as well as that generated by reactions should be in balance; otherwise, it is easy to encounter problems with excess liquid. The structure of the pre-cooling tower, the method of treating sulfur foam, make-up water, and the temperatures of the gas and liquid phases all affect the system’s water balance. ③Salt balance: The accumulation of salts directly affects desulfurization absorption and mass transfer, thereby impacting the efficiency of desulfurization. The stability of the catalyst, the pH value/alkalinity of the desulfurization solution, the HCN content in the gas, the concentration of the catalyst, the volume of liquid discharged, the method used for treating sulfur foam, and the temperature control of the desulfurization solution—all of these factors can affect the salt balance. With the HPF technology, about 50% of the sulfur is converted into by-products salts, requiring large amounts of liquid to be discharged daily to maintain salt balance; whereas with the iron-chelation technology, only 1% of the sulfur is converted into by-products salts, making the management of salt balance relatively simpler and the costs much lower. ④Impurity balance: mainly refers to the oil and dust impurities brought in from coke oven gas, or known as oil balance. The accumulation of oil dust can lead to problems such as a high specific gravity and difficulty in floating foam. Impurity levels in the gas (coal ash, tar, benzene, toluene, etc.), light tar in the additional excess ammonia water, wastewater from the sump return system, and sulfur foam treatment methods all determine the impurity content in the system. ⑤Alkaline balance: Desulfurization takes place in a weakly alkaline environment; the higher the alkalinity, the better the desulfurization effect in theory, but side reactions are also more likely to occur, so the alkalinity must be controlled properly. The type of alkali source, the temperature of the desulfurization liquid, the method of treating sulfur foam, the inlet hydrogen sulfide concentration, the volume of discharged liquid, etc., are all directly related to the alkali balance. ⑥Heat balance: The inlet and outlet temperatures of the gas, the method used for treating sulfur foam, the heat exchange area of the heat exchangers, the conditions of the cooling or heating medium, and climate conditions all affect the system’s heat balance. Thermal balance also directly affects water balance, alkaline balance, salt balance, and so on. The balance among these aspects is interrelated and interdependent; they cannot be controlled separately. A systematic approach is necessary, taking into account everything from the project design stage through to its later operation, in order to achieve a stable state. Wuhan Guolitong’s “GLT zero-waste liquid technology for coke oven gas desulfurization” is based on the \"balance\" of various substances during the desulfurization process. Through optimized and adapted processes, it achieves zero waste liquid discharge during desulfurization, prevents tower blockages, and ensures efficient desulfurization and purification.