Effect of feed load on tower parameters
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When the load on a column decreases, for example from 100 to around 50 (which is what has happened in our plant recently), how do its control parameters change? It was found that, while the pressure at the top of the column remained constant, the pressure at the bottom of the column decreased. However, the temperature of the feed plate either decreased or increased by several degrees. The temperature of the parameter used for control also decreased by several degrees, yet the purity of the product did not decrease significantly. Physical properties such as the boiling point are related to pressure, but not to the feed rate. I’m really seeking help here – what is the impact of the feed rate on the parameters of the tower?
If the designed lower limit for flexibility is set at 50%, there won’t be much change in product quality, but the vapor-liquid load will change significantly. If you still maintain the original top pressure of the tower, it’s obvious that you need to reduce the reflux ratio. With the feed temperature remaining unchanged, the temperature in the distillation section will rise, the amount of vaporization will increase, and the volume of vapor and liquid at the bottom of the tower will decrease; as a result, the bottom pressure will also drop! This is my speculation; I welcome colleagues with different opinions to point out any errors!
Firstly, your assumption is that the composition of the material remains unchanged. Moreover, you want the product to be obtained from the top of the tower. From what you’ve said, according to the definition of saturated vapor pressure, if the composition of the material doesn’t change, then a certain temperature will correspond to a certain pressure. Therefore, your parameters will definitely change. Your explanation isn’t detailed enough; please be more specific. The empirical values vary depending on the load
Feed conditions come in many varieties; feeding at or above the bubble point differs from feeding at or below the dew point, and an actual analysis is required. In general, if the feed load at or below the dew point decreases, the heating amount should be reduced while adjusting the reflux rate. If the feed load at or above the bubble point decreases, the heating amount should be increased while adjusting the reflux rate. Even within the design range for the reflux rate or reflux ratio, adjustments should still be made based on the temperature of the sensitive plate – that’s just my opinion
The feed mainly affects the tower in terms of temperature and composition