Feasibility study on sodium carbonate as a chlorine absorber
Thread Content
This post was last edited by sunjl1981 on 2013-1-6 at 20:03. Common chlorine absorbers include NaOH, Na2S2O3, Na2CO3, and FeCl2. Assuming 1 mol of chlorine is to be absorbed, the amounts of absorbents required are as follows: Cl2 ~ 2NaOH ~ 0.25Na2S2O3 ~ Na2CO3 ~ Ca(OH)2 ~ 2FeCl2. It is clear that Na2S2O3 has the highest efficiency; however, its by-products, HCl and H2SO4, cause secondary pollution, so it cannot be used； After reacting with chlorine, FeCl3, the product of this reaction, is in a flocculent form; it can easily clog the gaps between the tower plates, so it cannot be used ； We are currently using NaOH, which is theoretically effective; however, given its strong corrosiveness, we must find other alternatives. For now, Na2CO3 is undoubtedly a good choice. Na2CO3 has the following advantages as an absorbent: 1. To absorb an equal amount of chlorine gas, the amount required is half that of NaOH. 2. When reacting with chlorine, the products are sodium hypochlorite, sodium chloride, and CO2; thus the hazard is **reduced**, and the product sodium hypochlorite can be sold as bleaching powder. 3. It has low corrosivity. Mass fraction, density (g/cm3), molar concentration (mol/L), temperature after dissolution (°C), pH, skin test (back of hand, exposure time of 60 seconds): 10%: 1.12, 2910, 0.88 – slight stinging sensation; 15%: 1.18, 33212 – slight burning sensation; 20%: 1.25, 435.213 – increased burning sensation along with stinging. 4. It is inexpensive and easy to purchase. In conclusion, it is acceptable to use a Na2CO3 solution with a mass fraction of 10% as the absorbent. . Note♀ ) # ♀ , .
Should we not use a baking soda solution, that is, a sodium bicarbonate solution?
Has the poster considered the cost ratio? For example, when absorbing the same amount of chlorine gas, how much sodium carbonate and sodium hydroxide are consumed respectively? What are the costs for each type of procurement? Does the equipment need to be modified, and what are the costs of such modification? Issues such as changes in pump prices and operating costs? For chlor-alkali plants, sodium hydroxide is produced internally; by absorbing waste chlorine gas, sodium hypochlorite can be generated for sale, so there are no issues with sales. If sodium carbonate is used instead, not only will purchasing costs increase significantly, but as the original poster mentioned, if it is further converted into bleaching powder, what would be the yield of that bleaching powder? How much more will the post-processing costs be? I also don’t understand why your bleach isn’t calcium hypochlorite Perhaps the original poster is only considering technical and security aspects; should we not take the actual situation into account as well? If the chlorine is used in a plant that already produces large amounts of sodium carbonate as a by-product, I believe it is acceptable to use it for absorbing waste chlorine; otherwise, the person in question will need to carefully consider the economic aspects. We look forward to the poster bringing us a **surprise** with a new technique.
Common chlorine absorbents actually also include Ca(OH)2
We only use chlorine in the production process, and there is a small amount of chlorine in the exhaust gases. The price of sodium carbonate is 1,000 yuan per ton, while the price of sodium hydroxide is 1,500 yuan per ton. Ca(OH)2 has too low a solubility, so it is not used. It is recommended to check the solubility data upstairs. The greatest advantage of using this process is its safety and environmental friendliness.
Should we not use a baking soda solution, that is, a sodium bicarbonate solution? The original poster lacks common sense; sodium bicarbonate is acidic, and it’s not generally used for absorbing chlorine.
6# rwanglong902 discussing with LZ: (1) A sodium bicarbonate aqueous solution should be weakly alkaline. (2) Is it economical and reasonable to use sodium carbonate to produce sodium hypochlorite? The key question is whether, when sodium carbonate reacts with sodium hypochlorite, the product is sodium bicarbonate or carbon dioxide? If it is carbon dioxide, it should be acidic at this point; could there be any safety hazards? (3) Has your company already adopted this process?
I’m very interested in knowing whether the original poster has any practical experience using Na2CO3 to absorb chlorine, as well as what the absorption efficiency and rate of this absorbent are. Since NaOH is a strong base, its reaction with CL2 is quite intense. On the other hand, Na2CO3 becomes alkaline after hydrolysis. I wonder if the original poster has conducted any further research in this area
Some people on the Internet say that using green ferrous compounds consumes iron bars; I’m not sure if this is true
This post was last edited by sirsdj on 2010-9-1 at 10:51. The sodium hypochlorite unit in chlor-alkali plants is responsible for handling chlorine gas in emergency situations; to ensure safety and take into account reaction speed as well as the convenience of replenishment, caustic soda should be used. For producing products, other alkaline or reducing substances can be considered.
The original poster’s idea is excellent; it involves determining at what price levels the costs of sodium hydroxide and sodium carbonate reach an equilibrium point. If this can help reduce energy consumption, it could represent a minor reform for the chlor-alkali industry.