Problems with the pipeline layout of the condenser at the top of the distillation tower
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Figures 1 and 2 show the PFD diagrams of the overhead condenser in the distillation unit. The primary cooler and the tail cooler are connected to the reflux tank in different ways. What was the reasoning behind using this type of gas-liquid separation tube as shown in Figure 1? I would appreciate it if someone could explain this to me. Thank you.
This post was last edited by CHANGBAISHI on 2020-2-13 at 15:34. The gas is taken from the top of the distillation tower and sent to various condensers; under the condition that a certain amount of reflux liquid is maintained, the remaining liquid is obtained as the product. The subsequent steps after removal are incomplete; for now, it is understood as removal. For reference.
The type of connection depends on the amount of non-condensable gases in the gas phase, the physicochemical properties of the medium, and other factors. Pressure balance is required regardless of the connection method.
Typos and wrong characters are really frustrating to read
I have a question: why is the pressure monitoring point at the top of the tower located on the pipeline?
Figure 1 simply adds a pipeline that leads the fluid, after primary condensation, directly to the secondary condenser (exhaust gas condenser). It can be understood that when the vapor phase at the top of the tower increases suddenly and cannot be condensed through the primary stage, part of this fluid goes into the reflux tank while another part goes directly to the secondary condenser (exhaust gas condenser) for condensation.
Can it be installed directly on the top of the tower?
When drawing the process diagram, I may not have paid enough attention to the locations of various devices. I think the pressure control valve is meant for releasing gas; if it were used to discharge liquid, its function would conflict with that of the external liquid level control valve, making the process unreasonable. The return pipeline is located at the bottom of the tank, thereby creating a liquid seal that prevents gas from flowing back into the tank and escaping directly from the pressure control valve without passing through the secondary cooler. Due to the presence of the primary cooler, the amount of gas entering the secondary cooler is limited, and there is not much condensate either; as a result, the pipeline does not get filled to capacity. Therefore, it is feasible to allow a small amount of non-condensable gas to escape from an opening at the upper part of the pipeline in order to control the pressure at the top of the tower.
This post was last edited by HEJIYUER on 2020-2-18 23:46, version 1. In the two diagrams, the product at the top of the tower is in liquid phase. 2. In the first diagram, when it gets cold, a boiling point is reached; thus, the balance tube can create pressure in the reflux tank, providing pressure for the reflux pump. The second cooling stage is used for load regulation, and it can be managed with CWS. TWS: Is it for adjusting the temperature, with a temperature higher than that of CWS? 3. In the second diagram, the first cooling stage involves subcooling; therefore, the pressure in the recirculation tank is maintained by adding nitrogen. The second cooling stage involves the condensation of lighter components, and since the amount involved is small, chilled water is used for this purpose. The question is: As for the means of tower pressure control, using a PV valve to regulate the liquid phase – the intention was to optimize the heat exchange area of the secondary cooler; therefore, it should be installed at the outlet (not on the branching path). Additionally, the second graph shows subcooling; adjusting the load on the secondary cooler has little effect on the tower pressure.
Theoretically, it’s fine to install it on a tower, but making holes in the equipment is still less convenient than making holes in pipes.