5- The feather leaf separator is used in the design of the secondary steam for the MVR evaporation crystallizer in ammonium sulfate (sulfuric acid AN) mixed acid systems
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This post was last edited by luoli519 on 2023-10-3 at 18:20. A friend’s company generates large amounts of dilute sulfuric acid an during the production process and in the treatment of waste materials. They found a design firm that provided them with a series of multi-effect evaporators for the purpose of progressively concentrating and crystallizing the ammonium sulfate solution produced by the factory, with the by-product ammonium sulfate being sold externally. However, since the plant began operating, the steam taken from the tops of the evaporation crystallizers at various levels has carried along a significant amount of ammonium salts, resulting in extremely high levels of ammonia nitrogen in the condensed wastewater. This has caused the wastewater treatment units to operate under heavy load, and the water discharged from these units often fails to meet the required standards, which is a real problem. It is understood that multi-effect evaporation crystallizers are widely used in various applications such as salt production, seawater desalination, brine treatment, wastewater desulfurization, and the treatment of waste salts generated in caprolactam production. In some cases, the control of salt content in the steam extracted from the top of these crystallizers and their condensed water is satisfactory; in other companies, the initial performance of the evaporation crystallizers was not ideal, but after modifications, their performance improved significantly. Please share your methods for preventing salt contamination in the steam used in evaporation crystallizers, so that I can offer advice to my friend’s company and help reduce the amount of salt in the concentration steam from its crystallizers. After all, the industry is not doing well, and environmental emission issues only make things worse. Thank you all!
Are there impurities such as coal tar and phosphates in the dilute AN sulfate solution? Such impurities generate foam during the evaporation and crystallization process; this foam occupies the gas space, causing AN sulfate to enter subsequent systems along with the non-condensable gases, as a result of which AN sulfate is present in the evaporated condensate. It is possible to consider adding a demister to solve this problem, but care must be taken to prevent the demister from getting clogged, and it should be easy to clean if it does get clogged.
This post was last edited by luoli519 on 2022-11-30 21:18. This sea friend is absolutely correct. A demister must be added to capture mist from the steam taken from the top of the evaporation crystallizer. To prevent the crystallization of sulfuric acid anhydride in the sulfuric acid anhydride solution from adhering to the demister, it is very important to properly design and select the demister. Additionally, a dual-sided spray washing system should be installed in accordance with international practices, so as to effectively remove any crystals that may adhere to the demister. Evaporation crystallizers used abroad, in both chlor-alkali plants and other types of salt production facilities, are equipped with specially designed finned demisters as well as a two-sided spray washing system designed in accordance with relevant standards.
Solving the problem of entrainment is simple: First, check whether the sulfuric acid AN mother liquor in your facility is foaming; severe foaming will inevitably lead to liquid being carried along, and in extreme cases it can cause the material to overflow, preventing normal evaporation. If that’s the case, controlling foam is the top priority; an appropriate defoamer can be used, and a defoamer device can also help to some extent, but it won’t be effective if foaming is severe. Second, the diameter and height of the evaporation chamber must be sufficient; there needs to be enough headspace for gas-liquid separation, and the upward flow velocity of the gas should not be too high.
This post was last edited by luoli519 on 2023-10-3 at 18:21. This sulfuric acid mother liquor does not form bubbles. For conventional evaporators, entrainment is a common problem that is not easy to resolve, and it represents a significant challenge for many evaporator manufacturers. Considering only the diameter and height of the evaporation chamber represents a traditional perspective on gravity separation; according to previous industry standards, it is only capable of separating droplets larger than 0.6 microns. This approach not only fails to meet the increasingly stringent environmental regulations today, but also results in large equipment sizes and high costs, making it uneconomical in terms of both operating expenses and equipment acquisition costs. Now, the design institute recommends the use of advanced vane-type demister. I am currently learning about the technology.
The main problem is probably not the equipment; we have encountered similar projects before. I guess your waste liquid is alkaline, right? Try adjusting the solution to a weakly acidic level (pH=6~7). Why not give it a try? This design firm isn’t reliable either
The design institute has requested the company to conduct tests for pH value and ammonium forms; the pH value is 6.2, and the ammonium salts exist mainly in the form of diammonium and ammonium hydroxide. The design institute’s recommendation to use high-efficiency gas-liquid demisting separators to address the issue of ammonia salt foam entrainment in the steam taken from the top of evaporators has been officially adopted by industry expert groups. Meanwhile, owners of similar evaporation crystallization equipment are advised to pay close attention to the technical capabilities of the manufacturers and suppliers of steam demisters.
The attached diagram is an installation diagram for the demister of the evaporation crystallizer, specifically designed and provided by Novel Separation Technology Company at the request of the headquarters of a European company for its factory invested in China. For more detailed information on Novel Company’s (Nuowei Technology) separation technologies, you can access additional details directly through this HCBBS forum link: http://bbs.hcbbs.com/thread-1354813-1-1.html. Let’s work together to make a greater contribution to more clear skies and blue skies in China, as well as to the environmental protection industries that are closely related to this
Can a wire mesh demister be used? ?
The use of wire mesh demisters is not recommended, as their internal components tend to get clogged, resulting in an increasing operating pressure drop and a rapid decline in separation efficiency. It is necessary to stop the operation periodically to replace these internal components, which leads to low operational efficiency and high maintenance costs.
It is normal for the ammonia nitrogen content in the condensate water to be slightly elevated after the evaporation of the anhydrous sulfuric acid solution; however, it is abnormal if any liquid from the reaction mixture ends up in the condensate water.