Can hydrothermal ammonia be directly fed into a normal-pressure ammonia tank?
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Hello everyone: I am currently facing a tricky problem. I have just started a new 180,000-ton synthetic ammonia production project. When the urea production line is shut down, 25 t/h of cold ammonia at -33°C is generated. There are two 5,000 m3 atmospheric-pressure ammonia tanks available for storing this ammonia. Additionally, there is also hot ammonia produced by the old plant, at a rate of 14 t/h, at 20°C and 2.4 MPaA; this hot ammonia used to be sent to the pressurized ammonia tanks. However, it has been decided that those pressurized tanks will be removed, so this hot ammonia also needs to be stored in the atmospheric-pressure tanks. I am concerned that directly sending this hot ammonia into the atmospheric-pressure tanks might pose the following problems: 1. The selection of valves used before the ammonia enters the tanks, as well as the operating requirements for such valves, are quite stringent, and the pressure difference across the valves is high； 2. Ammonia being directly fed in due to poor control, failed valves, and other reasons can very easily cause overpressure in the ammonia tank ； 3. Moreover, after thermal ammonia is depressurized, it has a certain temperature, which differs significantly from that of the cold ammonia formed upon injection; continuous injection ensures that the cold and hot ammonia remain in contact with each other, and the expansion and contraction due to temperature changes can also cause the ammonia tank to rupture ；
Reply to 1# Classmate: I suggest using liquid ammonia at 2.4 MPa and 20°C. It should first pass through the ammonia storage tank in the refrigeration system, where the pressure needs to be reduced to around 1.5 MPa; this allows the liquid ammonia that has been cooled in the refrigeration system to be further cooled, taking advantage of the cooling capacity of this liquid ammonia at 20°C. After that, it enters the ammonia tank at normal pressure. Before doing so, it’s advisable to have it cooled again by the refrigeration system. I’m not sure what your refrigeration system looks like; if you have a P&ID, we can discuss it together. This explanation might not be very clear
One is a pressure system with a pressure of 2.4 Mpa and a temperature of 20°C, and the other is a low-pressure system at atmospheric pressure with a temperature of -33°C. Although both store liquid ammonia, how can they be mixed together? Have you calculated what the state of the liquid ammonia at 2.4 Mpa and 20°C would be like after its pressure is reduced to atmospheric pressure? What form is the decompression taken? In my opinion, the two gases must under no circumstances be mixed directly together, as there is a huge difference in their states, which could lead to overpressure accidents in the ammonia tanks at normal pressure. The safety supervision authorities would not approve such an approach either. A pressurized ammonia tank is still needed for storing liquid ammonia at 2.4 Mpa.
Hello, I would like to know approximately how much the investment and operating costs are for a 650-cubic-meter liquid ammonia storage tank system under normal temperature and pressure conditions. It would be helpful if you could provide a flow diagram and a list of the equipment used. Thank you