Confused fruits on a confused tree – pumping liquid ammonia from an ammonia tank
Thread Content
This post was last edited by 3983596_FPPZ on 2019-1-14 at 13:06. The company plans to purchase a metering ammonia injection pump: externally purchased liquid ammonia is unloaded into an ammonia tank, and the metering pump draws liquid ammonia from that tank； ①So how is the pump inlet pressure determined? Assuming that a pressure higher than the saturated vapor pressure is applied during unloading, once part of the liquid ammonia is used, does the pressure inside the tank drop to the saturated vapor pressure at the corresponding temperature of the liquid ammonia? ②The liquid ammonia inside the tank is in a saturated state; does this saturated state consist of both saturated vapor and saturated liquid? ③Could the pump get empty or stop working altogether?
Last edited by asolos2010 on 2019-1-14 11:02. Additional note: It is set at the same level as the pump inlet; the L liquid ammonia tank does not have a pressure compensation line
Personal opinion: Just pump normally from the bottom of the tank, so that the pump operates in a reverse flow mode. 1. During pumping, the pressure inside the tank will certainly drop to the vaporization pressure; by pumping from the bottom, the liquid ammonia at the bottom can still enter the pump due to gravity. 2. There is a gas-liquid saturation state. But this does not affect your operating conditions; it seems that the pump is unable to draw liquid up, and there is no liquid ammonia left in the tank. 3. The metering pump (positive displacement pump) can function normally, and when it stops working, it indicates that there is no liquid ammonia in the tank
Use a metering pump? Is the traffic very low? Please tell me the specific flow rate and head; I’ll help you take a look.
The extraction medium is in a saturated liquid state, with a pressure equal to the saturated vapor pressure plus the pressure resulting from the liquid level height； When the fluid is pumped out through the pipeline, it gains kinetic energy, and the pressure decreases. If the liquid level is not high enough and may drop below the saturated vapor pressure, then heat will be absorbed for vaporization: L
Why use a metering pump? The operator is probably reluctant to use one; for liquid ammonia, it’s usually weighed directly on a scale. Because the error of the metering pump can be quite large. A direct finned pump will do; it can draw vacuum, but an ammonia tank generally requires a gas-phase connection pipeline