Tower pressure drop and temperature difference
Thread Content
I. What are the hazards of an increased pressure drop in a distillation tower? ? How should it be handled? II. In distillation, if there is too much moisture, does the pressure difference across the tower increase while the temperature difference decreases? Could you explain it?
I. What are the hazards of an increased pressure drop in a distillation tower? ? How should it be handled? A large change in pressure drop indicates that there has been a significant change in the gas and liquid flow rates inside the tower; based on this change in pressure drop, the gas and liquid flow rates within the tower should be adjusted accordingly. II. In distillation, if there is too much moisture, does the pressure difference across the tower increase while the temperature difference decreases? Could you explain it? It mainly depends on what the distillation medium is; generally, changes in pressure difference lead to temperature changes, which in turn result in a smaller temperature gradient.
There are several reasons for the significant pressure drop: 1. Excessive steam supply to the reboiler or high load; 2. Contamination of the tray or packing; 3. Liquid flooding or tower submersion. Identify the cause and take appropriate action accordingly. The amount of water added has a certain impact on the pressure difference. For example, if too much water is added to the pre-tower, the moisture content at the bottom of the tower increases, leading to rises in both temperature and pressure, while the conditions at the top of the tower remain almost unchanged; as a result, both the pressure difference and the temperature difference increase.
If the proportion of moisture is high, that is, if the water content is high, then the pressure at the top of the pressure tower changes significantly. Generally, the pressure at the top of the tower decreases, while the pressure at the bottom of the tower remains relatively unchanged. In other words, as mentioned earlier, the overall pressure difference across the tower increases, while the temperature difference decreases.
Reply to 4# Extended Road: The pressure difference of the tower is composed of three parts. That is, the plate resistance, the liquid layer resistance, and the resistance due to the gas overcoming the surface tension of the liquid. Under normal circumstances, as long as the tray or packing is not blocked by dirt. This pressure difference is only related to the meteorological load. Once your water content increases, with the pressure in the two towers remaining almost unchanged, the temperature difference should increase. Due to the high water content in the tower bottom, the thermal load on the tower bottom is lower compared to operations with a high methanol content under the same load (as the latent heat of water vapor is greater than that of methanol). So the pressure difference decreases, but the temperature difference increases.
Reply to 5# Shouhou: I agree with your view