Are there any new technologies for chlorine drying?
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Recently, fewer and fewer customers are using chlorine to dry sulfuric acid. Moreover, the concentration of sulfuric acid requires high-performance equipment. Is there a chlorine drying process that does not involve sulfuric acid? As far as I know, temperature-swapped adsorption is used for VCM dehydration – could it be applied to chlorine drying as well? Anhydrous calcium chloride can also be used for chlorine drying. I think that after passing through a titanium cooler, the moisture content in chlorine would be around 0.4%; to reduce it to 0.04% or 0.01%, the amount of moisture involved is not much. Using solid adsorbents might be an option, but the choice of adsorbent and its regeneration processes are important issues to consider. Let’s discuss this further.
Drying sulfuric acid with chlorine gas? It seems to be written backwards. Although it is only a one-percentage-point reduction, the large production volume means that the amount of desiccant required is quite substantial. Solid drying – use a bed dryer? I’m afraid it won’t achieve the desired effect
Chlorine drying can be done using the molecular sieve dehydration method.
The main component of molecular sieves is alumina; hydrochloric acid is present in wet chlorine, which leads to the formation of aluminum chloride
This post was last edited by qugd on 2019-11-25 at 17:33. Using concentrated sulfuric acid to dry wet chlorine is a mature process, and its cost is low even under continuous operation conditions. Using other desiccants to dry wet chlorine gas presents two problems: first, the drying effect is not necessarily ideal (for example, with calcium chloride, it is very difficult to determine when it needs to be replaced or regenerated after absorbing water; once anhydrous calcium chloride absorbs water and turns into dihydrate calcium chloride, its water-absorbing capacity and efficiency drop significantly, and heating alone is insufficient to convert hydrated calcium chloride back into anhydrous calcium chloride). Second, the cost of these alternatives is much higher than that of sulfuric acid (concentrated sulfuric acid is inexpensive, and its subsequent treatment is simpler compared to other desiccants). Third is the operational difficulty: the absorption of water by sulfuric acid involves gas-liquid phase reactions, making continuous operation straightforward. In contrast, the use of calcium chloride for water absorption entails gas-solid phase reactions; after absorbing water, calcium chloride easily forms a semi-liquid form of polyhydrated calcium chloride (with up to six molecules of water of crystallization), which remains attached to the surface of the solid calcium chloride particles. Whether operating in a moving-bed or fixed-bed system, replacing and regenerating this material proves to be very difficult. Operational costs are difficult to predict. The physicochemical properties of VCM differ significantly from those of wet chlorine; it does not possess chlorine’s strong corrosivity and strong oxidizing power, making it easier to work with in terms of materials and processing procedures.
Technology is advancing by leaps and bounds, and what the original poster said is correct. As mentioned on the second floor, one aspect is quantity handling – whether it is possible to ensure continuous and stable operation. There’s also the issue of costs, which is the most important factor. Compared to sulfuric acid, the daily operating costs must not be too high; otherwise, it’s not worthwhile. There are also issues such as the service life of the absorbent, the one-time investment required, and the frequency of replacement. If there were a method that is more effective and cost-effective than sulfuric acid for dehydration, many companies would opt to use it.
I think the original poster might have been inspired by laboratory drying methods to come up with this idea.