Why is hydrochloric acid added in the third baffle tank during the brine treatment process?
Thread Content
This post was last edited by sunjl1981 on 2013-1-6 at 20:40. Hello, teachers and friends from Haichuan – what is the purpose of adding hydrochloric acid to the third baffle tank? # hcbbs
The main task is to adjust the pH value of the brine to between 8.5 and 10.5, so as to facilitate the absorption of divalent metal ions in the brine by the chelating resin
The excess alkali is neutralized to lower the pH value, causing substances such as calcium carbonate and magnesium hydroxide in tiny particle form to turn into ionic states, so that they can be removed in the secondary salt solution.
There are also those that do not add acid here; it is added at the inlet of the refined salt water pump, and the effect is similar in either case
Its main function is to adjust the pH value of the primary brine, neutralize excess alkali, and facilitate the absorption of the secondary brine as well as the adjustment of the pH value of the brine entering the tank.
The functions and purposes of adding acid in these two cases are completely different. After a large amount of calcium and magnesium has precipitated out in the brine, acid is added to convert the insoluble forms of calcium and magnesium into soluble forms; these substances are then further removed using chelating resins. The pH value at this stage is usually around 10 ； Acidification of the second-stage refined brine is used to adjust the pH of the brine fed into the system; this pH is generally between 3 and 4, although different processes and different membranes may require different values.
This post was last edited by Wang Zongliang on 2010-4-10 at 12:32. In the previous system, to remove calcium and magnesium impurities, sodium hydroxide and sodium carbonate were used to cause precipitation; meanwhile, to accelerate the reaction rate, an excess of these substances was required to make the brine alkaline. After completing the above process, it is necessary to adjust the pH value of the brine. The main reasons for this are as follows: 1. In the case of diaphragm electrolyzers, this affects the efficiency of the anode, and it also leads to a decrease in the purity of chlorine gas ； 2. In ion-exchange membrane electrolyzers, there is a process of refining the secondary brine; since the chelating resin column requires a pH value between 9 and 10, it is necessary to adjust the pH of the brine.
Hehe, I’m not sure what concentration of acid is appropriate; high-concentration acid is definitely hard to control. If there are issues with monitoring and the filtered salt water becomes acidic, that would be a big problem
The main purpose is to adjust the pH value so that it meets the adsorption requirements of the chelating resin column. It also involves converting the unfiltered small particles of calcium carbonate back into ions, thereby ensuring thorough adsorption and keeping the concentration of calcium ions plus magnesium ions below 20 PPb
It mainly adjusts the pH value of the saline solution to between 8.5 and 9.5, allowing calcium and magnesium to exist in ionic form, which facilitates adsorption by the resin.
Thank you to all the teachers for their enthusiastic responses, but there is one thing I still don’t understand: how can hydrochloric acid more effectively decompose the remaining calcium carbonate and magnesium hydroxide precipitates in an alkaline environment? Does adding hydrochloric acid react first with sodium hydroxide? I hope someone knowledgeable can provide an explanation!