What is the most appropriate concentration for diacid?

Hehe, if it’s 99%, it might not be enough; the chimney could still emit smoke. Theoretically, an absorption rate of 98.3% yields the best results.

The last edit to this post was made by txglyl on 2010-12-1 at 21:42. We share one circulation tank for absorption and drying; the acid concentration is kept between 98.2% and 98.6%. During one operation, the acid concentration reached 99%, which caused the sampling tank to emit some smoke, and the chimney released a large amount of smoke as well – it was really scary, as the amount of smoke was extremely high

It’s definitely not good – when the concentration is too high, the partial pressure of SO3 in the gas phase becomes excessive, which makes it difficult to absorb SO3 and leads to a decrease in the absorption rate; as a result, smoke is emitted from the exhaust gases

Thanks! But in our case, as the acid concentration increased, the amount of smoke coming from the chimney decreased – it’s really hard to understand.

Reply to 5# yiyunjin: Haha, there’s only one explanation – either your acidity measurement wasn’t accurate, or there’s an issue with the sampling point; otherwise it doesn’t conform to scientific principles. Just my personal opinion!

This post was last edited by txglyl on 2011-4-24 at 22:16. Reply to 5# yiyunjin: This is quite normal. If the acid concentration is too low, or too high, smoke will appear in the exhaust gases. The reasons for smoke in acid production exhaust gases include: 1. Acid mist, 2. SO3, 3. Water vapor. 1. Acid mist: Mist removal efficiency – poor; acid mist is already present in the flue gases (and such mist is generally difficult to remove). Drying efficiency – poor; there is too much moisture in the flue gases, which lowers the dew point and facilitates the formation of acid mist. Low acid temperature – acid mist can form inside the absorption tower due to local temperatures being lower than the dew point temperature. 2. Excessively high acid temperature: A high acid concentration results in a high partial pressure of SO3 in the atmosphere; as a result, more unabsorbed SO3 ends up in the flue gases. At the chimney outlet, SO3 combines with water in the air to form acid mist. Uneven acid distribution: Due to faults, the acid is not distributed evenly, and some of the SO3-containing flue gases remain unabsorbed; again, SO3 combines with water in the air at the chimney outlet to form acid mist. Too low acid concentration: An excessively high partial pressure of water vapor in the atmosphere leads to the formation of acid mist. 3. Water vapor: Excessive moisture – The moisture content in the flue gas exiting the exhaust treatment system is too high; at the chimney outlet, the moisture content of the flue gas exceeds the maximum allowable level for that temperature

The situation of inaccurate acid concentration analysis does not exist; I have conducted many experiments, and in fact such a situation does occur. I’ve also looked up a lot of information; 99% of the acids have a decent absorption rate, but they’re not suitable for use in a single absorption tower. Of course, our situation is very special; it may also be related to the defogger and the acid separation effect. We’ll have to wait until there’s an opportunity for a major overhaul.

99% is on the high side; we usually keep it between 98.6 and 98.8 here.

One absorption tower: Uses 98% concentrated sulfuric acid as an absorbent to absorb SO3 from the primary conversion gas from the conversion unit, thereby producing sulfuric acid as a product. Second absorption tower: 98% concentrated sulfuric acid is used as an absorbent to absorb SO3 from the secondary conversion gas from the conversion unit, thereby producing sulfuric acid as a product. Main reaction: SO3 + H2O == H2SO4 + Q

I think it mainly depends on the process involved, as well as the concentration of sulfur dioxide in the conversion system and the main components of the flue gas. When acid is produced from sulfur or pyrite, the flue gas has a high concentration, a simple composition, and few impurities. A high acid concentration results in a high partial pressure of SO3 in the atmosphere, leading to some loss of sulfur; it is recommended to keep this value between 98.0% and 98.5%. In the case of producing acid from smelting flue gas, the concentration of the gas is low (the sulfur dioxide content before conversion is generally 4-5%), and the composition is complex; therefore, the acid concentration can be slightly higher, with a recommended range of 98.0-99.0%. If the exhaust emits a lot of smoke, it is generally not caused by a high concentration of acid in the second stage of processing; other components originating from the mineral source can also lead to such smoke emission (for example, cuprous thiocyanate)