Distillation column feed temperature
Thread Content
What is the most appropriate feed temperature for a distillation tower? Our company’s equipment consists of only one tower; it requires nitrogen at the top of the tower, and the liquid from the bottom of the oxygen-enriched tower must be drained. There is only one logic control rule: if the feed temperature exceeds the set limit, it triggers the shutdown of the liquid nitrogen injection valve. When the expander fails, liquid nitrogen is fed back as a cooling source to replace the expander. Additionally, a low temperature alarm at the expander outlet can cause the expander to shut down; that’s the only scenario. Can automated production be achieved with such temperature control? Currently, all valves are manually controlled; this rule does not apply to those in IMC internal mode with the valve closed, or in IMO internal mode with the valve open.
May I ask: how does your equipment control the feed temperature? How is the outlet temperature of expanders and boosters controlled?
Generally, the pressure at the bottom of the tower is 0.5–0.6 MPa, with a corresponding saturation temperature of around 100–101 K.
The system used by the original poster is one based on pure nitrogen separation~~ Expansion refrigeration and liquid backflow can serve as alternatives to each other; it’s sufficient to adjust the valve opening for backflow. As for the temperature of the air entering the cooling chamber, I don’t think it’s very necessary; instead, more attention should be paid to the molecular sieve, especially regarding the analysis of carbon dioxide content at the outlet. Additionally, an interlock mechanism should be in place to ensure high purity of the nitrogen at the outlet, and a control valve should be used to regulate the flow rate of the gas at the outlet~~
A low-temperature interlock at the expander outlet should be installed to prevent liquid from being present at the outlet~~
The experienced workers also feel that the feed temperature has little impact, and they operate based on their experience. Will it affect the purity?
The high feed temperature alarm should be what causes the backfill valve to open, right?
Could the poster share a diagram of your process? Is the feed temperature referring to the temperature in the rectifier? If that is the case, the feed should have undergone heat exchange; as a result, the feed temperature in a distillation system at equilibrium remains relatively stable. As long as the feed volume and the molecular sieve are in order, this temperature will not change significantly under normal operating conditions. A interlock should be set to lower the expander outlet temperature, but it’s not necessary to have them linked one-to-one.
Feed temperature refers to the temperature of the material entering the distillation column. With the feed rate remaining constant, the temperature change is minimal. Please explain why Upon observation, the temperature change is indeed minimal