The top pressure of the distillation column can be maintained stably, but the reflux temperature increases as the temperature of the circulating water rises, resulting in an increase in the pressure difference across the column.

This issue relates to the process details of acetonitrile extraction; the top pressure of the tower can be used to control the stability of the separation process, but an increase in the reflux temperature leads to changes in various parameters, such as an increase in the pressure difference across the tower. In the case of alkyne flash towers, high-temperature and high-pressure tetraalkyne compounds are fed in and subjected to vacuum flashing; butane and butylene are used to dilute the flashed mixture in order to control its composition – this is one of the common solutions. -

I’m seeking advice from all the teachers regarding the reasons for changes in the reflux temperature

Changes in the reflux temperature can be caused by the following factors: 1. Changes in the temperature of the circulating water: Reflux condensers are usually cooled using circulating cooling water; if the temperature of this water rises, then the reflux temperature will also increase accordingly. 2. Thermometer malfunction: Problems with the reflux thermometer, resulting in inaccurate readings, can cause changes in the reflux temperature. 3. Furnace tube blockage: In some cases, the furnace tubes may become blocked by material, leading to the accumulation of liquid inside the tubes and changes in the heating area. This may affect the readings of the reflux temperature. 4. External interference: The reflux condenser may be affected by external environmental factors such as direct sunlight or wind; these factors can cause changes in the temperature of the reflux condenser, thereby affecting the readings of the reflux temperature. The above are some possible reasons for changes in the reflux temperature; the specific cause needs to be analyzed and determined based on the actual situation. -

I’m not sure about the exact process, but circulating water is supposed to be the medium used for cooling and recycling, so the return temperature will increase as the temperature of the circulating water rises

I can’t understand the principle behind how changes in circulating water temperature lead to changes in return flow temperature. Furthermore, in other distillation columns, the reflux temperature does not change with variations in the circulating water temperature; this phenomenon occurs only in this column. The key issue is that the reflux temperature has increased while the reflux volume remains unchanged, and yet the top pressure can still be kept under stable control; I don’t understand this.

The question you raised is quite specific, allowing for a targeted analysis. First, the relationship between the reflux temperature and the circulating water temperature is determined by the working principle of the reflux condenser. The function of the reflux condenser is to cool the reflux liquid and turn it back into a liquid state, thereby ensuring a stable reflux volume. It also acts as a heat exchanger, cooling the reflux liquid through heat exchange with circulating water. Therefore, as the temperature of the circulating water rises, the heat exchange between the return fluid and the circulating water is affected, resulting in an increase in the temperature of the return fluid. As for why the other distillation columns do not experience changes in reflux temperature due to variations in the temperature of the circulating water, this may be attributed to the following reasons: 1. Different column designs: Different columns have distinct design structures and operating principles; some distillation columns use other refrigerants such as alcohol or liquid nitrogen instead of circulating water for their reflux condensers, so changes in the temperature of the circulating water have no effect on these columns. 2. Different operation control methods: In addition to differences in tower design, the operation control methods of distillation towers can also vary. For example, some towers may use reflux ratio control rather than reflux temperature control; as a result, changes in the temperature of the circulating water have no effect on the reflux temperature. In summary, an increase in the reflux temperature while the reflux rate and top pressure remain stable may indicate that there have been changes in the operating conditions of the reflux condenser and the tower; therefore, a detailed analysis of the operational parameters and equipment inspection are necessary to determine the cause of the problem. -

You’re welcome; feel free to ask me any questions at any time. -

Distillation is a systematic issue; each parameter has its own control logic, and a change in one parameter will cause changes in others. Generally speaking, as the temperature of the circulating water rises, the amount of heat carried away by the system decreases; if the steam volume and the processing capacity remain unchanged, this will inevitably lead to an increase in the temperature of the entire system. In fact, the overall temperature has not increased; the most likely reason is that the amount of steam has decreased. Looking at it individually. “The principle behind how changes in the temperature of the circulating water lead to changes in the reflux temperature is as follows: obviously, when the temperature of the circulating water rises while its volume remains unchanged, less heat is removed, and as a result the condensate cannot cool down, leading to a higher temperature. He doesn’t have this problem with the others; perhaps the circulating water volume in those other towers is higher, or their heat exchange area is large enough, leaving a surplus. This tower has insufficient margin. The control of the tower top pressure is achieved through the outlet valve; it is the valve that determines the pressure, and this is independent of temperature

The temperature of the reflux stream increases, but there is no significant change in the temperature at the top of the tower. Considering the increase in tower pressure, it is possible that the reflux flow rate has increased. If the temperature at the top of the tower and that of the reflux valve control system are under automatic regulation, then an increase in the temperature of the condensate at the top of the tower necessarily implies an increase in the reflux flow rate. If there is no flow meter for the reflux stream, this can be verified by observing changes in the opening degree of the reflux valve