★★★★★Discussion on the recycling of waste sodium! ! !

In our company’s process for reusing defective sodium hydroxide, such defective material does not need to be aerated; it is directly mixed with sodium hydroxide in a high-level tank to produce sodium hydroxide suitable for use as a cleaning agent. The system has been operating stably for over a year now.

I was wondering if the original poster could provide their contact information? Could you please explain this in more detail? Regarding what the poster said about simply adding the waste sodium hydroxide to the high-level tank, I have the following questions: First, how is the effective chlorine level controlled after mixing the waste sodium hydroxide with the fresh sodium hydroxide in the high-level tank? Second, doesn’t adding more liquid to the system over time result in an increasing amount of liquid within it, since nothing is removed from the system? Third, the pH value of the waste sodium hydroxide is quite high; isn’t it necessary to address this issue? Fourth, the waste sodium hydroxide contains a large amount of hard ions; how can this be dealt with?

Also, regarding what the original poster mentioned about adding inferior sodium to the high-level tank – does that mean it should be added directly from the clean tower?

We directly add sodium hypochlorite to the cooling towers to cool crude acetylene (there are two such towers; one is cooled with sodium hypochlorite and the other with water). But why is the waste sodium hypochlorite in our facility acidic? I’m a bit confused by what the original poster said: (1) Why recycle defective sodium, instead of adding it to the generator? Is it for security reasons? But isn’t the accumulation of acetylene more dangerous? The available chlorine in the waste sodium hydroxide solution is very low; I guess it has little value in terms of recovery. (Some of it may decompose after being exposed to sunlight, and the alkaline environment might slow down this decomposition process. But as you mentioned, it’s difficult to control the pH level, and it’s easy for the solution to become acidic. It’s likely that the solution will end up being saline after exposure to sunlight.) (2) Why is acid added to adjust the pH? We usually adjust the pH of hypochlorite to between 7 and 9. Since oxidation of elements such as S and P occurs after cleaning, resulting in the formation of corresponding acids, the pH should be lower than that of the hypochlorite solution. Then why is it necessary to add acid? Personally, I believe the disadvantages of the above process outweigh its advantages. As I have no experience with this process, this is merely my personal speculation; please point out any mistakes. I also do not recommend using waste sodium for cooling, as its acidic nature can cause some corrosion to the equipment. However, since your plant uses an alkaline environment, you might give it a try; in that case, descaling will likely be necessary. I suggest adding another cooling tower, one in use and one as a backup. Could you explain to me why it is alkaline? Thank you, I’m very curious. :o

Same question as the OP? Please advise. Also, since it contains acetylene, isn’t it dangerous when mixed with chlorine? This post was last edited by wf35516481 on 2008-1-21 16:17.]

It is not added directly to the generator because the calcium carbide slag produced is used to make cement clinker, and this slag must not contain chloride ions, as they can corrode the equipment. It has an alkaline nature because when waste sodium is added to the cooling tower to cool crude acetylene, the acetylene contains a large amount of alkaline impurities such as slurry foam. Why is it necessary to recycle waste sodium? First, releasing it directly pollutes the environment and also results in the waste of a significant amount of acetylene gas. Second, direct discharge leads to the waste of a great deal of water resources…… Water is the most precious resource.

I have a question regarding what was mentioned on floor 2: when the amount of recycled sodium hypochlorite used in my company exceeds half of the amount of fresh sodium hypochlorite, it causes sodium hypochlorite to decompose, resulting in a decrease in the effective chlorine content. I’m really puzzled by this. How does your company manage this situation? Have you encountered similar problems?

1. The available chlorine can be controlled using the conventional method of preparing sodium hypochlorite from acetylene. 2. Part of the inferior sodium can be sent to the generator for use, as after pressure filtration of the calcium carbide slurry, about 30% of the water remains in the calcium carbide residue, and this water is removed ； Moreover, the reaction of calcium carbide with water also consumes some water. Therefore, the amount of water in the entire acetylene system will not increase; if it is properly controlled, the amount of water in the system will even gradually decrease. The poster can understand this situation through the water balance. 3. The pH value of the defective sodium hydroxide can fluctuate, but as long as the pH value of the sodium hydroxide used for acetylene purification after reusing this defective sodium hydroxide is properly controlled, it has no significant impact on production. 4. After the reuse of defective sodium, since in the acetylene production system some of this defective sodium is carried away along with calcium carbide slag, a significant portion of the hard ions present in the defective sodium can also be removed. It is important to pay attention to conducting thorough inspections and replacements of the fillers in the cleaning tower and neutralization tower during maintenance, in order to prevent scaling of these fillers and thus avoid disruptions to the normal operation of the towers. This post was last edited by yhpsxj on 2008-1-22 17:11]

It is recommended to mix sodium hypochlorite with sodium carbonate in order to prepare sodium hypochlorite for acetylene purification.

Our company generally keeps the reuse rate at around 50%, as the remaining 50% of defective sodium can be removed along with the calcium carbide slag. The high reuse rate of defective sodium hydroxide, which leads to a decrease in available chlorine, may be caused by the accumulation of impurities in such defective sodium hydroxide. Therefore, it is necessary to control the proportion of recycled defective sodium.

Currently, it’s difficult for us to control the ratio. Our company deals with dry-process acetylene, and it’s not possible to use calcium carbide slag to remove excess sodium hypochlorite; we would like to reuse a larger amount of it. How can we control the reuse ratio?

I have another question: How can alkaline substances still be carried along by acetylene gas after passing through the mud washing tank, secondary water cooling, water ring pump, and vertical separation cooler?

I really don’t know how to answer that question you mentioned upstairs. ....Where does the alkaline substance in the acetylene gas you mentioned come from? What is your process??? The standard procedure is that the acetylene gas passes through a sludge washing tank, a cooling tower, and a water ring pump; it then goes through a purification tower, followed by a neutralization tower (alkaline cleaning tower), and after cooling it is sent on to the synthesis stage!

I’m sorry; the first time I read your post correctly, but the second time I got it wrong and made such a stupid mistake. Please forgive me :loveliness: