Height issue of the U-bend in stage 1 and 2 evaporation.

There is no need for discussion: the vacuum level is determined by the quality of product design, while the height of the bent tube is determined by the pressure difference.

Personally, I don’t think it has much of an impact; the height of the U-shaped bend for primary and secondary steaming can range from 3 to 6 meters. You can figure this out through calculation! ! !

It is closely related to the pressure difference between the first and second evaporators; the height is not small, and fluctuations in the vacuum level between these two stages can very likely cause damage to the vacuum in the second stage (air leakage may occur after the liquid seal is broken), which significantly reduces the flexibility in operation. If the height is too large, the residence time will definitely be longer and the resistance will be greater; this will require a larger pressure difference between stage 1 and stage 2. However, this may also pose a problem in terms of the operating pressures at those two stages. Ultimately, it is the pressure difference between stage 1 and stage 2 that determines the height of the liquid seal.

Experience tip: In evaporation systems, the height of the U-bends in the first and second stages of evaporation only needs to be higher than the local atmospheric pressure

If the liquid from one stage of the separator flows directly into the next stage, the low pressure in that second stage prevents the liquid level from being maintained, allowing gas to enter that stage as well, which would disrupt production. To allow liquid to enter while preventing gas from doing so, it is necessary to lengthen the liquid outlet pipe of the first-stage separator; a U-shaped design is used to ensure that there is no cross-flow of gas between the two evaporation stages. By using the pressure difference between the two stages and dividing it by the specific gravity of the corresponding urine concentration, the minimum required height can be determined. Generally, for safety and to ensure the proper functioning of each operation, sufficient margin is built into the design.

:)The length of the U-tube is determined by the requirement to balance the pressure difference at both ends. The pressure difference between the two sections is 0.032–0.0034 = 0.0286, which is approximately equal to 0.03 MPa (absolute). If 96% of the urine has a specific gravity of 1.2, then (0.03*10000)/1200 = 2.5 m. In other words, to meet the two production requirements, the height from the bottom of the U-tube to the inlet of the secondary vaporizer must be greater than 2.5 m. Given the fluctuations in pressure during production, and to ensure that operations in each section can continue even when the pressure in one section is high (resulting in an increased pressure difference between the sections), sufficient margin should be built into the design. Currently, the height from the bottom of the U-tube to the inlet of the secondary vapor heater is 5.65 m; this corresponds to a pressure difference of (5.65*1200)/10000 = 0.068 MPa. In other words, a pressure difference of up to 0.068 MPa is permissible during production, which indicates that such a height for the U-tube is quite safe.