1. Introduction

In the production process of the sulfuric acid plant, three absorption towers will have liquid flooding problems due to changes in process parameters. In the initial stage of the flooding problem, the process parameters of the absorber are not sensitive and can not be found in time. When the liquid flooding occurs, the moisture at the exit of the drying tower exceeds the standard, and the acid fog at the exit of the first and second suction towers exceeds the standard, and the absorption rate decreases. When the flood tower will cause fan kicking vibration, sublimation sulfur, smoke and other safety and environmental protection accidents, affect the production of the unit. Next, make a detailed analysis of the causes of the liquid flooding problem of the absorber.

2. Liquid flooding

The common phenomenon of liquid flooding in sulfuric acid plant mainly includes acid branch pipe liquid flooding and sulfuric acid mist entrain liquid flooding. Acid branch pipe flooding means that the sulfuric acid in the branch pipe gas obstruction, so that sulfuric acid can not normally flow into the packing layer, resulting in sulfuric acid in the trough acid separator to cause liquid flooding. Sulfuric acid mist entailing liquid flooding means that the gas phase flow rate in the filler gap space in the absorption tower reaches a certain speed, so that sulfuric acid on the surface of the filler enters the surface of the filler along with the rising gas phase, and the circulating sulfuric acid cannot fall to cause liquid flooding. The operating process state during the production of liquid flooding is called the liquid flooding point. In the production, the flood rate must be controlled within the allowable range to ensure the stable operation of the absorber.

When the liquid flooding in the absorption tower begins, the resistance of the tower will rise sharply, the absorption rate will drop sharply, and the liquid level of the circulating tank will drop rapidly. The reason is that the sulfuric acid in the acid distribution branch pipe flows back into the acid distribution tank, so that the circulating acid cannot flow into the packing layer through the acid distribution branch pipe. The sulfuric acid will overflow from the tank and form resistance with the rising air flow, forming a liquid film above the packing around the acid distribution tank, blocking the rising air flow and destroying the gas phase distribution in the absorption tower. When the hydrostatic head can overcome the pressure difference, the sulfuric acid will flow downward. When the liquid flow rate remains the same but the vapor flow rate is uneven, the pressure difference between the filler layer and the acid distribution layer will increase, and the acid distribution liquid level will rise, and the sulfuric acid will not flow downward. When the circulating acid continues to send acid to the acid distribution tank, the liquid accumulation will begin. Severe will make the whole tower full of sulfuric acid, damage the mist eliminator, and even bring sulfuric acid into the system.

3. Causes of flooding

1. The equilibrium value of the current operating gas velocity of the circulating acid flow rate is broken, causing the acid branch pipe to flood, which often occurs in the load regulation process of the device.

2. The acid distribution branch pipe is corroded or blocked by debris, resulting in uneven acid distribution, and the gas phase of the packing layer is uneven, resulting in short gas phase. Sulfuric acid entrainment flooding occurs in the road.

4. Measures to prevent flooding

1. Make the measuring instrument related to the absorber perfect and reliable, and provide accurate data for operation. (Instrument consultation available)

2. Load adjustment must be carried out in strict accordance with the order of operation rules. (The anti-flooding operation manual of the absorber can be provided)

3. Each overhaul of the device needs to repair and maintain the acid distributor and acid branch pipe, replace the corroded acid branch pipe and clean the debris.