Air separation oxygen production area: [Weekly Topic] Week 2 of 2011 – When is the best time to start the expander during air separation unit commissioning?
Thread Content
This post was last edited by siena2008 on 2011-1-11 at 21:09. When starting the air separation unit, should the expander be started after the upper and lower towers have been pressurized, or after only the lower tower has been pressurized? What is the most appropriate time to initiate operation? We hope everyone will share their opinions regarding when the expanded air should be fed into the upper and lower towers!
Personal opinion: Start it after pressing down at the bottom tower! After the expander is started, the expanded air enters the upper tower.
In my opinion, it can be started once the pressure in the lower tower has been restored. The purpose of the expander is to provide cooling; the earlier it is activated, the sooner the tower can be cooled.
As the original poster mentioned, either of these two methods works. We have two air separation units from different manufacturers, and in both cases, gas is first introduced into the tower before the expansion machine is activated. Once the gas is introduced into the tower, the flow path is established, allowing air to circulate; as a result, the inlet temperature of the expansion machine continues to drop, the volume of gas increases, and the expansion machine can produce more cooling effect, thereby enabling the system to cool down more quickly. The gas introduction to the upper tower also doesn’t take very long. In fact, the gas introduction to the upper tower and starting the expander can be carried out simultaneously, as long as you have enough time to handle both tasks. Basically, these two processes take place simultaneously: on-site, verification of starting the expander is carried out, while at the control room, gas is directed into the tower. That’s good too. We are devices for internal compression; we’re not very familiar with those for external compression
In my system, there is internal compression: the expanded air enters the lower tower, where it undergoes mass and heat exchange with another stream of high-pressure air that has been compressed through 4 stages by a compressor. The liquid air from the lower tower is then returned to the upper tower via the condensers in the crude argon tower and the refined argon tower. At startup, once the booster reaches a stable pressure level, the expander is activated.
After the downward tower is pressed, the expander can be used; the expanded air enters the upper tower, and the expanded gas presses on the upper tower
Generally, the expander can be started after stamping is completed in the lower tower. This applies to both internal compression and external compression.
Open after pressing after the up and down tower flushing. The premise of expansion mechanism cooling is that all channels in the heat exchanger are connected, after which the temperature gradually drops as the expander starts to operate.
When starting the expansion machine during the commissioning of an air separation unit, it is necessary to consider the status of the unit. If starting up after a temporary shutdown, it should be initiated once the air intake to the lower column becomes stable. In the case of starting up from an initial liquefaction state, it is first required to ensure that the dew point in the air separation system has been properly purged.
In our factory, gas is guided while the expander operates at the same time, which helps to reduce startup time
Once the pressure equalization in the lower tower is completed, the two expanders can be started!