Principle of concentrated acid absorbing water and sulfur trioxide

In sulfuric acid production, sulfur trioxide (SO3) is typically generated through a contact process, and it needs to be absorbed in this process to produce sulfuric acid. The basic principle behind concentrated sulfuric acid absorbing moisture and sulfur trioxide involves the dissolution process of sulfur trioxide gas in sulfuric acid. 1. **Principle of sulfur trioxide absorption**: In sulfuric acid plants, after being generated in a contactor, SO? gas needs to be absorbed by dilute sulfuric acid to be converted into concentrated sulfuric acid. Sulfur trioxide has very good solubility in sulfuric acid, and it can react rapidly with sulfuric acid to produce sulfuric acid of higher concentration. This process is exothermic and requires appropriate cooling measures. 2. **Principle of concentrated sulfuric acid absorbing moisture**: Concentrated sulfuric acid has a strong water-absorbing capacity and can absorb moisture from its surroundings. This property means that concentrated sulfuric acid can absorb water vapor from the air while absorbing SO2, thereby affecting the concentration and quality of the final product. Regarding your specific situation, namely whether the drying process can also make use of a 98% sulfuric acid cycle, here are a few points to consider: – **Advantages**: Using a higher concentration of sulfuric acid (98%) may improve the absorption efficiency of SO2, as a higher concentration allows for the absorption of more SO2, which could thus increase production efficiency and the quality of the sulfuric acid. - **Disadvantages: – **Equipment corrosion**: Higher concentrations of sulfuric acid increase the corrosive effect on equipment, which may require the use of more corrosion-resistant materials and thus raise maintenance costs. - **Operational risk**: Handling higher concentrations of sulfuric acid requires stricter safety measures, posing a greater threat to the safety of the operators. - **Energy consumption**: Maintaining the temperature and concentration of concentrated sulfuric acid may require more energy input. It is recommended to evaluate whether such a change is economically feasible and safe, based on specific production conditions and equipment status. If the equipment can withstand the corrosion of higher concentrations of sulfuric acid and proper safety measures are in place, this method may lead to improved production efficiency. But safety and cost-effectiveness must be taken into account. .

Additionally, in theory, it’s possible to use 98% acid for drying. However, after drying, water is absorbed and the concentration decreases. Generally, in the case of drying using 93 acid, 98 acid is passed through in sequence to maintain a stable concentration of 93 acid. If drying is carried out using 98 acid, the question arises as to what acid can be used to maintain the acid concentration. Meanwhile, the 93 acid produced by drying is discharged into the absorption circulation tank. Maintain system balance.

The control range for the concentration of drying acid is 93.5%-94.0%. Generally, this concentration is determined based on the following three factors: 1. The water vapor partial pressure above the sulfuric acid solution must be low, to ensure that the moisture content in the flue gas after drying is less than 100 mg/m3； 2. Minimize the generation of acid mist, or avoid its formation, during the drying process ； 3. Minimize the dissolution of SO2 gas, and reduce the loss of SO2 in flue gases as much as possible.

In the north, 93% acid, which is not easily frozen, is produced for most of the year, while 98% acid is prone to freezing. If the concentration of the dry acid is also 98%, then dilution is required to obtain 93% purity, which increases energy consumption.

The absorption of sulfur trioxide gas is essentially the process by which water reacts with sulfur trioxide to form sulfuric acid； Moreover, the acid used here for absorption is not dilute sulfuric acid; theoretically, a concentration of 98.3% is used, while in practice it’s around 98.5%. When considering the corrosive effect on equipment, not only the acid concentration but also the temperature of the acid must be taken into account. If there is only a difference of 93% and 98% in concentration, and the acid temperature is well controlled, the corrosiveness should not increase significantly. I think the factors related to acid concentration and freezing point mentioned by the person on the 5th floor need to be considered. In the north, winters are long and temperatures are low; dry acid has a lower freezing point. If a higher-concentration acid is used, it’s more likely to freeze in areas with low flow rates and low velocities when the temperature is low

Using one or two sucks of acid on the dry string will maintain a dry acid concentration； If the air humidity is high during summer, reduce the amount of water added to the system or add no water at all; dry it out by absorbing acid, and if that approach no longer works, consider adding acid online or replacing it

The first and second inhalations result in a higher concentration; it’s a 93% concentration of dry acid, which can be used directly as the final acid product, right?

I would like to ask, regarding the third point on reducing sulfur dioxide losses, how should this be understood?

Currently, 93% acid circulation is used for the drying of most devices, as it yields the best drying results after absorbing moisture； The 97.5–98.8% acid circulation is used in the first and second absorption stages because 98% acid has the best efficiency in absorbing sulfur trioxide ； If 98% acid is used for drying, the drying effect is inferior to that achieved with 93% acid; the moisture content does not meet the required standards. Additionally, 98% acid tends to form acid mist, which can corrode equipment. What is the principle behind concentrated sulfuric acid absorbing moisture, and sulfur trioxide? Sulfuric acid has strong hygroscopic properties.