Renovation of the heat exchange system in the crude distillation tower
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1. Before the modification of the heat exchange system, it consisted of two-stage condensers (stainless steel shell-and-tube condensers), with the first stage being water-cooled and the second stage salt-cooled. Both condensers were horizontal in design; the material flowed through the shell side while the refrigerant flowed through the tube side. The reflux ratio was set at a horizontal position about 1 meter above the flange on the top head of the tower. 2. After the modification of the heat exchange system, a three-stage condenser is used (a stainless steel shell-and-tube condenser): stage 1 cooling is by water, stage 2 and stage 3 cooling are by brine. All condensers are installed vertically, with the material flowing through the tube side and the refrigerant flowing through the shell side; the reflux ratio is set at the horizontal level of the tower top head flange. The problem is that the feed to the crude distillation vessel is a fixed amount supplied once; the materials involved are n-butyl ether and triisopropylsilane. During crude distillation, it is mainly n-butyl ether that evaporates. After making these changes to the heat exchange system, almost no n-butyl ether enters the vacuum system. As a result, the concentration of n-butyl ether does not increase during the distillation process, and the time required for each batch also increases. Before the changes, the reflux ratios were 10:3 or 10:5, yielding a concentration of over 99%. After the changes, the reflux ratios became 15:1, 18:1, or 25:1, yet the concentration still failed to increase. Now the tower is being dismantled to replace the packing; the packing in question is stainless steel wire mesh packing. There are three sections of the tower, each 3 meters long. Experts, what could be the reason for this? ? ? Process Management Group
Are there light components in the feed mixture? If the butyl ether content at the top of the tower is not within specification, is it due to the entrainment of light components or heavy components? There are possibly several reasons I’m considering, for the original poster’s reference: 1. The mixture contains light components, which result in good condensation effects, preventing these light components from escaping in gaseous form ； 2. Due to three-stage condensation, the pressure drop across the condenser may be relatively high; as a result, the pressure difference provided by the reflux ratio controller to send liquid back to the tower is insufficient, which hinders a smooth reflux process. Moreover, if an electromagnetic reflux ratio controller is used, intermittent reflux may occur. If the liquid distributor inside the tower is not properly designed, the efficiency of the packing cannot be fully utilized ；
Thank you very much. 1. There are two feed components: n-butyl ether (the light component) and triisopropylsilane (the heavy component). 2. An electromagnetic type reflux ratio controller is currently being used. 3. The distributor at the top of the tower is functioning properly. Is there any simple solution for this issue?
Could you provide the specific material composition and distillation requirements? I can do a quick calculation. Send a message via WeChat; WeChat ID: job_hu2012
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Most likely, after the modification, the potential difference is insufficient, preventing backflow into the tower
Is the pressure drop from the top of the tower to the vacuum pump taken into account? Prediction: After the modification, the process flow enters the tube side, and a condenser has been added. The pipe diameters are small, the pipelines are long and tortuous, which leads to an increased pressure drop. The operating pressure at the top of the tower is higher than the expected vacuum level, and the operating temperature will also change.
As the reflux ratio increased, the concentration indeed decreased. It is necessary to consider whether the impurities were discharged in gaseous form; if the impurities also become part of the reflux, they will affect the temperature inside the tower, thereby causing changes in the temperature of the product obtained. Samples can be taken to analyze the components of the condensate at the top of the tower as well as the distribution of impurities in each tray within the tower. If more filler is added to increase the concentration without separating out impurities, the concentration will still drop after operating for some time.
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