Let’s discuss what precautions should be taken regarding liquid backflow during the startup of air separation units
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1. Initial startup after the air separation unit overhaul. 2. Hot start-up after extensive preheating of the air separation unit. 3. (Cold start), starting the vehicle after intermittent short stops, and restarting when the cooling time is long and the amount of cold energy available is limited. Regarding driving in the above three situations, is it possible to use the liquid backflow method? What aspects need attention when applying this method? What are the key points to note? Feel free to share your experiences! I am extremely grateful! Technical Paper Group
In my opinion, when driving the machine in its original state, it is not suitable to perform operations involving the pouring of liquids, as it is necessary to check the condition of the cooling system; if something isn’t in order, the machine has to be stopped to address the issue. Therefore, even when the temperature has reached its lowest point at this stage, it’s still better to continue monitoring! I wonder what everyone thinks?
If the gas production unit needs to start operating for safety reasons or due to economic pressures, then compared to normal operation, the ability to supply gas earlier thanks to liquid backflow is of great significance for the air separation unit. If there is no urgent need for gas, it is possible to calculate the cost of the driving energy used (usually steam or electricity), the hourly consumption, as well as the cost of the liquid required to prevent backflow. Currently, the market price of liquid nitrogen is between 500 and 700 yuan per cubic meter (the price varies slightly depending on the region). The amount of liquid nitrogen required for backfilling varies depending on the size of the air separation unit; it is advisable to compare the energy consumption costs with the liquid consumption costs based on empirical values in order to determine whether it is economical. Additionally: Liquid backflow in air separation units generally can only occur when the temperature inside the unit drops to a certain level, allowing liquid to form within the tower; otherwise, too rapid a temperature drop may cause stress and damage to the equipment.
It’s not difficult; read the instructions more often, practice more, and first master the technical parameters and process specifications. In the original operation, more expanded air is introduced, while less low-pressure and high-pressure air is used, in order to minimize the temperature before the expander. Driving a refrigerated vehicle is relatively simple; all that’s needed is to control the heat loss. Pouring in liquid must be done when the vehicle is at low temperature, and the speed should be kept low at first. This can’t be explained in just a few words; one needs to practice more and think more. It’s actually not difficult at all – what’s difficult is the driving skills.