How to increase the pressure in liquid ammonia storage tanks
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I have two liquid ammonia storage tanks, each with a capacity of 50 m3, used for denitration. It is winter now, with temperatures of 10°C, which results in a low temperature in the liquid ammonia storage tank as well; the pressure is around 0.6 MPa, and this level does not meet the requirements for operational purposes. So, I would like to ask everyone: in winter, how can I increase the pressure in the liquid ammonia storage tank, prioritizing methods that do not require technical modifications? Thank you!
Open the nitrogen valve to fill the liquid ammonia tank with nitrogen, thereby increasing the pressure in the tank
This method seems to be the most direct, but other supporting measures need to be put in place as well; moreover, the original poster requires that no additional technical measures be introduced. . . . .
It’s best not to use nitrogen filling, as it can lead to problems. You can consider raising the temperature of the ammonia storage tank appropriately.
If investing, a heat exchanger can be added; it is necessary to strictly control to prevent overpressure. Problems with adding nitrogen: Nitrogen requires a sufficiently high pressure, and backflow may occur ； Nitrogen will participate in denitration along with ammonia; in reality, the amount of ammonia used may be similar to that without nitrogen, or even less.
Adding a heat exchanger is not feasible; the unit remains in operation, and the ammonia has not been drained for replacement. Charging with nitrogen is a rather complicated process; it is necessary to build up pressure first. Nitrogen does not participate in denitration along with ammonia, because nitrogen is insoluble in liquid ammonia.
Do you use liquid ammonia for denitration? Where does liquid ammonia evaporate?
Yes, using liquid ammonia, heated and evaporated with a water bath heater
Liquid ammonia is pressurized using a pump and then heated to vaporize; it is best to use a small centrifugal pump, as flow control with metering pumps is somewhat more complex. Pressurized nitrogen in the tank not only prevents backflow but also increases the load; in summer, gas-phase supply can affect the denitration efficiency. Heating of liquid ammonia tanks does not recommend the use of internal coils, as leaks or overheating can be very dangerous; it is better to use external coils at the bottom, with hot water being the preferred option.
Can we keep the pressure of gaseous ammonia lower?