Could experts in distillation please analyze and give some advice?
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There are two feed towers, and during startup they encounter a situation where the load cannot be increased. Please have experts analyze this issue. The following are the observations: The abnormal phenomena in this tower mainly occur in the middle section between the two feed streams. At 40% load, the temperature of the second feed stream remains unchanged; however, the temperatures of the three layers above that feed layer are 20°C higher than the normal operating temperatures. Yet, the temperature of the fourth layer above those is back to normal ； The tower pressure difference has decreased compared to before ； The temperature of the sensitive plate at the bottom of the tower is 10 degrees lower than before℃ ； With a little steam at the bottom of the tower, the temperature rises sharply 3 layers up in the second feed stream. I’ve tried increasing the reflux and adding more steam, but it didn’t work. Please have an expert analyze this for me; thank you
First of all, it is necessary to determine what the minimum operating load of this tower is, and whether operating at a \"40% load\" falls within the acceptable range. Typically, to adjust the conditions of distillation, resistance is first introduced after adding the material so that it reaches the required level, and then purity is adjusted. Your 40% might be the key to the problem. It is recommended to refer to the operating procedures or instructions, as well as the startup steps and process requirements. For reference.
Can the feed rate or temperature of the first stream be adjusted?
First, check what the lowest load of the tower is
The purpose of distillation is to achieve the desired separation effect; not all parameters need to meet the original standards. Since the amount of material has changed, a new balance needs to be established
Yes, it’s not possible to handle the load at the moment. Trying to adjust the reflux and steam levels didn’t help either; it’s clear that the temperature in the middle layer is too high, 20 degrees higher than normal during normal operation of the tower, and as a result the product at the top of the tower is of poor quality
The load is fine; everything is within the normal design range
1. With such a low feed rate, it’s pointless to use two feed inlets； If the properties of the raw material indicate a large volume of product at the top, the upper feed inlet should be used; if there is a large volume of product at the bottom, the lower feed inlet should be used. 2. The main control points should be the top and bottom temperatures of the tower, the top pressure, as well as the amount of product taken from the top and the amount of reflux; feed temperature is secondary, while the temperatures of the intermediate tray levels are only for reference. 3. Adjust the control scheme and control parameters based on the product analysis results.
The problem statement is unclear: 1. It is necessary to specify what type of distillation is involved Reaction distillation, extractive distillation, or azeotropic distillation? 2. Is the feed flow at 40% of what one considers to be the normal value? 3. Is the feed composition consistent with the predetermined value?
Okay, thank you. 1. This tower is used for extractive distillation; the first stream of product leaving the tower (at the top) is the extractant. 2. The feed flow rate and its composition (as determined through sampling and analysis) match the predetermined values