How are the front and back positions in the synthesis tower defined?
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How are the front and back positions in the synthesis tower defined?
From the perspective of the process flow, the section from the outlet of the circulator to the synthesis tower is generally referred to as the pre-tower area; the synthesis tower, heat exchanger, and waste boiler are considered part of the in-tower area, while the section from the outlet of the heat exchanger to the inlet of the circulator is called the post-tower area； Valves are often installed between these three sections to facilitate pressure maintenance in separate segments; each of these segments is equipped with a vent valve, referred to as the pre-tower vent, in-tower vent, and post-tower vent respectively. If no vent valve is installed at the pre-tower position, the inlet valve of the circulation pump can be closed and the bypass valve opened, using the circulation pump’s vent valve as a substitute.
The main difference between venting in front of the tower and venting behind it lies in the composition of the gas being vented. Due to variations in ammonia content as well as the hydrogen and nitrogen contents, choosing the appropriate venting location can help reduce losses of useful gases. Of course, different venting locations have varying effects when it comes to purging the system.
It is usually placed before the synthesis tower, and can be used for adjustment when the hydrogen content is high. Behind the tower is the gas that has been cooled by water and then separated from ammonia, either through ammonia fractionation or cold separation; at this point the inert gas content is at its highest, making venting energy-efficient.
The overhead vent is installed on the pipeline before it enters the synthesis tower; it is generally used very rarely. We usually employ it when the circulator shuts down or malfunctions, or when the resistance inside the tower becomes too high. The back-pressure vent is located after primary separation or secondary separation; it depends on the location of the make-up gas supply – it is generally placed before the make-up gas inlet to reduce losses of useful gas. The inert gas content here is high, while the ammonia content is low. Pressure buildup in the synthesis tower, high temperature of the ammonia feed for cooling, high temperature at the water-cooling outlet, high ammonia content in the feed to the tower, catalyst poisoning, and high level of inert gases – all these situations require venting from the tower
Our vent is usually placed after the ammonia separator in our tower, as the gas at that point is the most inert, with less hydrogen and also less ammonia. In front of the tower, we generally place it at the outlet of the oil filter
Placing simple elements in front of and behind the tower can be understood as placing hydrogen in front of the tower and nitrogen behind it
I personally agree with what was said on the fifth floor.
After oil separation, the venting before the synthesis tower is called front venting, while the venting after the ammonia separator and behind the synthesis tower is called back venting. Front placement is generally used less; it is employed when the gas composition for supplementation is unsuitable, while back placement is mainly used for introducing inert gases.