Seeking advice on the ammonia vaporization combined with desalination process technology

Perhaps ammonia vaporization and desalination can be combined into a multi-effect evaporation process; this depends on the difference between the cost of steam and electricity. The temperature increase achieved with MVR is only around 20 degrees, so it’s a bit difficult to implement a multi-effect system in this case

Thank you. Multi-effect systems are relatively expensive; I hope that combining ammonia evaporation with MVR can help reduce energy consumption

Bro, get your thinking straight – if you want to achieve zero emissions, how can you still focus solely on low cost and low energy consumption? It’s impossible ? The simplest approach is to use alkali to assist in ammonia evaporation, provided that the dilute ammonia solution obtained has other uses, such as serving as a raw material for ammonia-based desulfurization. A 30% caustic soda solution can be added to the middle section of the ammonia evaporation tower to enhance the ability of ammonia to escape. Using direct steam heating in the bottom of the tower improves efficiency; with proper design and operation, it is possible to keep the ammonia content in the wastewater below 50 mg/m3. Approximately 0.1–0.15 tons of steam and 15–20 kg of alkaline solution are required per ton of wastewater, which is a considerable amount. After ammonia evaporation, some sulfuric acid is added for neutralization in order to adjust the pH value. Finally, MVR evaporation is used for concentration to produce sodium sulfate monohydrate; this product contains trace amounts of sulfuric acid. Such sodium sulfate monohydrate cannot be sold at a high price – 200 yuan per ton is already considered a good deal. The MVR process is equivalent to a five-effect evaporation process in terms of operational parameters. If the costs of steam and electricity in your plant are reasonable (for example, if you use a coal-fired boiler for power generation), then the economic efficiency of both the five-effect evaporation process and MVR is similar, and the investment requirements are also about the same. Of course, if you choose domestic vapor compressors for MVR, the initial investment will be lower, but the maintenance costs will be higher. It is recommended that you consult with professional MVR manufacturers; they usually suggest using Piller compressors from Germany, as they are very reliable. MVR is similar to five-effect evaporation: to evaporate one ton of water, 0.2 tons of steam are required (the cost in terms of electricity is roughly the same; it depends on how high your electricity rates are. In any case, **industrial electricity costs are quite high in the power grid**). . In theory, this process seems simple – first ammonia is vaporized and then the liquid is evaporated for concentration. In practice, however, it involves a lot of complex elements. As a rough guideline for investment costs, they range from 1 to 1.5 million per ton of waste liquid. If the amount of waste liquid to be processed is around 6 tons per hour, then the factory will need to invest around 6 to 10 million in construction costs. Moreover, significant operating expenses will be required after the facility is built. . Environmental protection comes at a cost, as the concentration of solid substances in these waste liquids is relatively low; therefore the costs are high. Glauber’s salt isn’t very expensive either, so I suggest you do a thorough calculation. Environmental protection is something that requires a lot of energy and resources, making it quite uneconomical. Yet, it’s necessary to carry out such measures. . . If you’re going to do it, do it well; therefore, having a clear plan is very important. If you don’t want to spend money yet still want to achieve zero emissions, give up on that idea right away – it’s impossible.

The ammonia evaporation process in the initial distillation stage can make use of heat pump distillation (with a temperature difference between the top and bottom of the tower of less than 20 degrees). In fact, this process is also one of concentrating sodium sulfate aqueous solutions, and its energy consumption is relatively low. By using heat pump distillation, both the amount of water required for cooling at the tower top and the heat needed for the reboiler at the tower bottom are reduced, resulting in significant energy savings； Subsequently, a densitometer is used to ensure that sodium sulfate reaches saturation before it enters the forced circulation FCMVR evaporation system at the back end; the energy consumption per ton of water is between 30 and 40 kWh, with the aim of minimizing energy use. (Our company can provide the process package, the main equipment – steam compressors – as well as the design, processing, manufacturing, installation, and commissioning of the entire system. We have completed over 400 such projects.) For inquiries, please contact QQ691951325, 18861029861 (same number on WeChat), or via the in-site messaging system

It is better to add sulfuric acid for neutralization, allowing sodium sulfate and sulfuric anhydride to be precipitated by direct evaporation. For a ternary water-salt system, if separate separation is desired, it is necessary to carefully consider the phase diagram of this ternary system.