Control of C3 in dry gas and control of C5 in liquefied gas
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In our company, when the reaction temperature remains constant and the catalyst stays the same, excessive C5 levels are often observed in the liquefied gas when the feedstock changes from heavier to lighter grades; whereas excessive C3 levels appear in the dry gas when the feedstock changes from lighter to heavier grades. The absorption and stabilization components have limited elasticity, and multiple adjustments do not yield satisfactory results; I would appreciate your advice!
1. The excessive level of C5 is a problem related to the stabilizer tower; it might be due to an excess production of gasoline and LPG, which makes it difficult for the stabilizer tower to handle them properly – it’s overloaded. . . Hahaha. . . 2. In the case of carbon triols, absorption (reabsorption) is poor or there is excessive degradation. . . It might also be because once your raw materials are changed, the amount of gas increases. . . Haha. . .
①Liquid control failure in the reabsorption tower; liquid level is full； Use a control line to regulate the liquid level and connect it to instruments for processing ； ②The absorption tower is flooding; the lean gas contains too much oil ； Increase the absorption dose, lower the absorption temperature, and improve the absorption efficiency ； ③The oil absorption in the lean phase is low, while the amount of gas in the lean phase is too high ； Properly adjust the amount of lean absorbent oil ； ④overdesorption ； Appropriately reduce the temperature of the desorption tower to adjust the desorption efficiency ；
In liquefied gas, the C5 level is controlled by appropriately reducing the temperature at the bottom of the stabilizer, while ensuring that the vapor pressure of the stabilized gasoline remains within acceptable limits； ②Appropriately increase the reflux flow rate at the stabilizer top, or reduce the reflux temperature ； ③Appropriately increase the operating pressure of the stabilizer column and maintain stability ； ④Adjust the feed inlet position according to the specific circumstances ；
The C5 level in the liquefied gas is too high; reduce the reboiling amount at the bottom of the stabilizer, and it is preferable to increase the reflux ratio as long as the operational flexibility permits； Excess C3 in the dry gas can be caused by insufficient absorption in the absorber, or excessive absorption. Insufficient absorption leads to an excess of C3 in the feed to the reabsorber, which in turn results in an excess of C3 in the dry gas. Excessive absorption causes an excess of C3 in the liquefied gas, increases the pressure in the stabilizer tower, and raises the amount of non-condensable gas discharged, thereby also leading to an excess of C3 in the dry gas. The key is to adjust the operation of the absorption tower.
Another possibility is that the reaction depth is too great; for example, excessive catalyst activity (too much fresh agent added) may cause this issue, or the reaction temperature may remain high even after the oil becomes lighter. With a large volume of gas, it is easy for the absorption tower to be overfilled, and the dry gas may carry carbon 3
What the original poster means is that problems tend to arise during the two transition periods when the composition of the raw materials changes from heavy to light or from light to heavy; therefore, it’s necessary to keep an eye on the condition of the raw materials and detect any early signs of changes, so as to adjust the operations in a timely manner. The problems are not difficult to resolve.
The levels of ＜C3 and ＞C5 in LPG are not related to the composition of the feedstock, but only to the operating conditions of the stabilizer column.
The conditions given by the OP are too few! I don’t even know which specific parameters you adjusted! C3 control is primarily determined by the reaction! You need to analyze the reaction temperature! Catalyst activity! Properties of crude oil! Then, let’s take another look at the amount of light oil obtained through distillation to make a comparison! If there’s too much light oil, it indicates that it may be time to increase your absorption level! As for the stable part~ it mainly depends on the amount of desorbed gas from the desorption tower! (I think it’s a very crucial parameter.) Then, check the temperature at the top of the absorption tower and the temperature difference between the crude steam and the stabilized steam! Generally, the top temperature will not be higher than these two values! Other temperatures also need to be monitored! For example, the temperature at the bottom of the desorption tower, as well as the top temperature! Don’t set it too high! The suction pressure works really well~ Remember to lift it upward in moderation! Generally, with careful handling! C3 should be kept below 2%! There are also many factors affecting C5! C2 is very low! Your C5 might be above the limit! The pressure and top temperature–level of the stabilizer must be kept stable! The feed inlet is usually located in the middle to lower part! The cold return flow rate and temperature also need to be well controlled! Which of these factors is not well controlled! It will affect you too! Generally, in our case, C5 is controlled to below 0.5% – because the device following it is a gas separator! You’re not pointing in the right direction! Please do not leave negative comments! Thank you!
It’s the typical impact of changes in raw materials. Our approach is to directly observe the situation based on the extent to which the raw materials are changed, and then adjust the reaction temperature accordingly, so as to avoid exceeding the specified limits