In the process of sulfuric acid production, the absorber demister plays a crucial role. However, in the actual production process, there will be a decline in the performance of the mist separator, resulting in the acid fog of the absorber's export gas beyond the allowable range, which will not only cause serious corrosion damage to the sulfuric acid equipment, inhibit the conversion rate of the catalyst and reduce the conversion rate, but also may cause environmental pollution. Therefore, it is of great significance to find out the reason of the performance decline of the demister and take corresponding improvement measures to improve the technological level of sulfur acid production and protect the environment.

The upstream of the drying tower treatment device is the drying air raw material. After the drying tower is arranged with a fan and a sulfur conversion section, so the defogging performance of the drying tower plays a very key role in the production of sulfuric acid. Below we will look at what impact the performance of the drying tower defogger will have on the device.

1. Fan guide vane and impeller corrosion

Drying tower usually adopts wire mesh demister, for the flow of the fan behind the tower, the poor performance of the drying tower wire mesh demister means that there is acid, and the acid has a greater impact on the core equipment of the sulfuric acid device fan. When the process gas containing acid enters the inside of the fan, it hits the impeller at a high speed and erodes several grooves on the impeller, thus forming a major hidden danger affecting the safe operation of the fan. [1]

2. Corrosion and leakage of downstream hot and cold heat exchangers, resulting in a decrease in total conversion rate

When the drying tower wire mesh mist remover with acid is serious, some of the acid entrain will enter the shell process of the downstream hot and cold heat exchanger, and the part of the tube bundle near the entrance of the shell process is easy to be corroded and form a perforation, resulting in the leakage of the above hot and cold heat exchanger, and the total conversion rate will also decrease. In particular, if the Ⅳ heat exchanger or the Ⅴ heat exchanger is used as a hot and cold heat exchanger, the cold process gas from the SO₂ fan has a higher concentration of SO₂ cold process gas and the hot process gas containing SO₃ from the end of the converter is exchanged. When the above hot and cold heat exchangers leak, a small amount of process gas containing high concentration of SO2 will leak into the inlet of the second suction tower, resulting in the SO₂ concentration in the exhaust gas of the second suction tower outlet soaring. [1]

3.SO₂ The water content of the flue gas at the outlet of the fan increases, resulting in powdering and scarring of the catalyst at the top of the layer

When the drying tower wire mesh demister with acid, the drying tower outlet flue gas pipe is easy to be corroded, perforated and formed leakage. For the post-tower fan process, the leakage of the drying tower outlet pipe causes the leakage of wet air, resulting in the increase of water content in the process gas entering the conversion process. There is also a factor that leads to the increase of water content in the conversion process gas is often ignored, the acid from the drying tower mist eliminator is heated after entering the downstream hot and cold heat exchanger, hot and hot heat exchanger, the acid mist will be decomposed into SO₃ and water vapor, will also lead to the increase of water content in the downstream process gas.

When the content of acid fog and water in the process gas of the converter rises, especially when the acid making device is frequently turned on and off, it has a great influence on the top catalyst of the first layer of the converter, which is easy to cause the top catalyst of the first layer of the converter to powder and scar, and the resistance of the first layer rises rapidly. Because the load of the acid plant cannot be turned on, the operating cost increases. [1]

4. Reduced driving rates and increased safety risks

When the drying tower demister carries acid, it will cause corrosion of downstream pipelines and equipment (including the abrasion of the downstream fan impeller with acid), so the operation rate of the acid making device will inevitably decrease. Repeated sealing of downstream heat and cold heat exchangers will increase the number of operations in confined Spaces and also increase safety risks. [1]

5. The thermal balance of a conversion is destroyed, resulting in an increase in operating costs

When the tube bundle of the cold and heat exchanger downstream of the drying tower is blocked too much, the heat transfer efficiency of the cold and heat exchanger decreases, and the self-heat balance of the primary conversion bed is destroyed in severe cases. It is often necessary to add preheating furnaces or electric furnaces to maintain the self-heat balance of the primary conversion bed. [1]

6. A conversion is a heat transfer process of ⅳi or Ⅴ I, which will lead to a surge in the concentration of SO₂ of the exhaust gas

For a conversion is ⅣⅠ or ⅤⅠ heat transfer process, when the drying tower mesh defogger performance is poor, from the drying tower mesh defogger with acid corrosion downstream Ⅳ heat exchanger or Ⅴ heat exchanger, it will lead to a surge in the SO₂ concentration in the flue gas of the second suction tower outlet. Typical IV I - III II “ 3+ 1 ” In this heat transfer process, the secondary conversion gas is successively heated by the heat of the third layer and the second layer of the converter, and the self-thermal balance of the secondary conversion bed is relatively easy to maintain, but the disadvantages are also very obvious. Even if there is a slight leakage of the Ⅳ heat exchanger, the high concentration of SO₂ gas from the SO₂ drying tower will leak directly to the second suction tower. Therefore, when the above heat transfer process is used, the upstream drying tower wire mesh demister must be used with high configuration. [1]