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1. There are three options when the product nitrogen pressure is higher than 8bar:

The first solution: the backflow expansion nitrogen production process is equipped with a product nitrogen compressor at the same time. The booster end of the expander pressurizes the product nitrogen or forward air. The air compressor pressure is the lowest backflow expansion pressure, and the product extraction rate can reach 38%. about.

The second solution: the positive flow expansion nitrogen production process is equipped with a product nitrogen compressor at the same time, the booster end of the expander pressurizes the product nitrogen or positive flow air, the minimum distillation tower pressure is 4bar, the product extraction rate can reach about 45%, and the amount of liquid Can produce larger.

The third option: the backflow expansion process, the pressurized product nitrogen or positive flow air at the booster end of the expander, the pressure required for the product directly out of the cold box, the disadvantage is that the backflow expansion pressure is high, causing part of the effective energy to be unused.

2. There are two options when the product nitrogen is between 5 and 8 bar:

The first solution: the backflow expansion process, the product nitrogen or forward air is pressurized at the booster end of the expander.

The second solution: the positive flow expansion process, the booster end of the expander pressurizes product nitrogen or positive flow air, and the product is compressed by a nitrogen compressor. This process has a great advantage when the pressure is high.

3. There are four options for product nitrogen at 0 to 5 bar:

The first solution: the backflow expansion process, the booster end of the expander pressurizes the product nitrogen or forward air, and then throttles to the required pressure, generally 4 to 5bar; the pressure of the backflow expansion air compressor is higher than the pressure of the product nitrogen 0.8bar high is required.

The second solution: the positive flow expansion process, the product nitrogen or positive flow air is pressurized at the booster end of the expander, and the product pressure is directly obtained, and the general product nitrogen is 4bar to 5bar. The pressure of the positive flow expansion compressor is about 1.5bar higher than the product nitrogen, but its extraction rate is higher. The expanded air is first pressurized, then expanded, and then directly vented as regeneration gas; when the product scale is greater than 10000Nm³/h, a separate booster can be installed To pressurize the expansion air, enter the tower after expansion, which can increase the product volume.

The third option: a two-tower rectification process. This process uses the oxygen-rich in the middle of the upper tower as exhaust gas to be discharged to the purifier as regeneration gas, and a large amount of oxygen-rich at the bottom of the upper tower is extracted as non-product gas, which can increase the discharge pressure of the upper tower. , Meet the product nitrogen pressure requirements, save the energy consumption of nitrogen product compression. This process can obtain product nitrogen at two pressures of 0 to 2 bar and 5 bar or higher.

The fourth solution: double-tower double-condensation process, throttling the oxygen at the bottom of the upper tower, and then go to the condensation head at the top of the tower, so that you can get 0 to 3 bar and 5 to 7 bar or higher product nitrogen, the product extraction rate of this process High, up to about 60%.