Thread Content
Coke oven gas contains large amounts of impurities such as tar, benzene, naphthalene, and coal dust. During the purification process of this gas, these impurities must be removed step by step to ensure that they do not cause significant issues in the subsequent processing stages. In this process, the waste gas is first sprayed with high-pressure ammonia water, causing its temperature to drop to around 80°C; it is then cooled in a primary cooler to around 22°C to remove naphthalene from the gas. Subsequently, it undergoes further purification in an electrostatic tar catcher to eliminate tar and dust from the gas. After that, the gas is pressurized using a fan and sent for desulfurization, followed by separation of ammonium sulfate and crude benzene. Finally, the purified gas is sent for further processing. For desulfurization systems, the tar present in the gas, once it enters and accumulates within the system, has a significant impact on the properties of the desulfurization liquid. This impact manifests in two main ways: first, it weakens the sulfur foam; since tar has an antifoaming effect, it makes it difficult to form a stable foam layer during the regeneration process. As a result, the concentration of suspended sulfur in the desulfurization liquid increases, and sulfur particles tend to attach to the packing material in the desulfurization tower or settle at the bottom of the tower. This leads to blockages in the desulfurization tower, the pipes carrying the desulfurization liquid, and the injectors, thereby causing difficulties in the operation of the desulfurization system and even resulting in accidents ； Secondly, it affects the quality of the desulfurization liquid, leading to an increase in its density and viscosity, a reduction in circulation volume, less regeneration air, and a decline in the efficiency of gas-liquid mass transfer. In severe cases, this can impact the desulfurization efficiency and result in hydrogen sulfide levels exceeding the allowed limits at the system outlet. In addition to gas introducing tar, there is another way that can introduce large amounts of tar: ammonia/ammonium hydroxide. Since the ammonia method is widely used for desulfurization in coking plants, the content of volatile ammonia in the desulfurization solution is a prerequisite for ensuring efficient desulfurization. Therefore, the ammonia water/ammonia gas obtained through ammonia evaporation is generally used to supplement the ammonia source for desulfurization, and as a result, certain impurities such as tar can easily be carried into the desulfurization process via this supplementary ammonia evaporation system. To address the issue of excessive levels in the desulfurization system, optimization is required from three aspects: 1. Gas purification at the upstream stage (1) Operation management of the primary cooler: Attention must be paid to factors such as temperature control, spray volume, and the ratio of the spray liquid. (2) Operation and management of electrostatic tar collectors: Attention must be paid to factors such as voltage control and sludge discharge control. (3) Operation management of the pre-cooling tower: Attention should be paid to issues such as the quality of residual ammonia water, spraying volume, and liquid carryover. 2. Regarding the replenishment of ammonia sources at the backend: (1) Quality control of residual ammonia water: Attention must be paid to the operation of oil removal equipment such as air flotation oil removers and ceramic filters. (2) Ammonia vaporization tower control: Attention must be paid to the control of the decompressor temperature, as well as the temperature inside the tower, etc. 3. Optimization of the desulfurization process control: (1) For situations where the oil content in the existing desulfurization solution is already high, it is possible to increase the foam overflow rate from the regeneration tank, and use plate and frame filter presses to filter the sulfur paste in order to remove some of the tar. In severe cases, part of the desulfurization solution can be replaced to reduce its oil content. Overall, the actual operational performance is closely related to daily management; only with proper equipment and effective operation management can the tar content in the desulfurization liquid be kept low, ensuring the normal operation of the desulfurization system.