Lefilter Batch Type Pyrolysis Plant Water Seal Tank

In batch-type thermal cracking oil refining equipment, the water seal tank serves as a critical safety auxiliary device, operating for long periods under oil-containing and dust-laden working conditions. Its common faults mainly fall into three categories: seal failure, blockage, and abnormal liquid level, which are detailed as follows:

Seal Failure and Loss of Backfire Blocking Capacity

This is the most dangerous type of fault. The main causes include an excessively low liquid level inside the tank that fails to fully submerge the pipeline gas outlet; or the water layer being covered by a large amount of oil sludge, forming an oil film that isolates the gas from contact with water, thus causing the failure of the water seal barrier. In such cases, backfire from the downstream system can easily flash back to the upstream equipment, triggering the risk of combustion and explosion. In addition, excessively high water temperature inside the tank (exceeding 60℃) will generate a large number of bubbles, which disrupt the stability of the water layer and also weaken the water seal effect.

Blockage Inside Pipelines or the Tank Body

Solid dust and uncondensed heavy oil mist carried by non-condensable gas continuously settle and accumulate inside the water seal tank, which can block the gas inlet, gas outlet, or bottom blowdown port. Blockage will lead to an increase in non-condensable gas transmission pressure, which may reduce gas circulation efficiency in mild cases and cause pipeline overpressure in severe cases. If the blowdown port is blocked, the oil sludge and impurities deposited at the tank bottom cannot be discharged, which will further exacerbate water seal contamination and failure.

Abnormal Liquid Level Control

This fault is divided into two scenarios: excessively high liquid level and excessively low liquid level. An excessively high liquid level will increase the resistance for gas to pass through the water layer, resulting in poor non-condensable gas transmission and even gas backflow into the cracking reactor. An excessively low liquid level directly leads to water seal failure, which is also the most common fault caused by inspection negligence during daily operation. Common causes of abnormal liquid level include failure of the water supply system, blockage of the overflow port, and the presence of leakage points on the tank body.

Tank Body Corrosion and Leakage

Corrosive gases such as hydrogen sulfide and hydrogen chloride contained in non-condensable gas will dissolve in the water seal water to form acidic solutions, which will erode the inner wall of the tank body and pipeline joints after long-term scouring. Meanwhile, oil contaminants in the water will also accelerate the corrosion of metal components. Corrosion can cause leakage in the tank body or pipelines, which not only leads to a drop in liquid level but also poses potential safety hazards.