The equipment of pure nitrogen and high-purity nitrogen is one of the main products of our company, and most of them adopt the process of forward flow and backflow expansion of single (double) tower. The characteristics of positive flow expansion process are: low energy consumption per unit, high extraction rate and remarkable long-term operation economy; while the characteristics of backflow expansion process are: high pressure of outlet tower nitrogen products and unaffected purity, complete set of equipment disposable less investment.
I. Waste gas backflow expansion process
Air is filtered by air filter and then compressed into compressor to the required pressure, then cooled and separate oil and water. Compressed air is put into the precooler, and water is separated in the water separator after cooling to about 10℃. The precooled air is put into the molecular sieve adsorber to remove the residual water, carbon dioxide, acetylene and other hydrocarbon, thus obtaining pure air.
Pure compressed air first enters into the main heat exchanger of the cold box (distillation column), and exchanges heat with the backflow low temperature gas. Part of the air is liquefied and then enters the distillation column. When the vapour rises, it conducts mass transfer and heat transfer with the recirculation fluid in the tower, thus obtaining high purity nitrogen at the top of the tower and oxygen-enriched liquid at the bottom of the tower. A part of high purity nitrogen is reheated by the main heat exchanger and then comes out of the cold box as product nitrogen; the other part enters into the condensing evaporator and is condensed into liquid nitrogen. Liquid nitrogen is divided into two parts. One part enters the distillation tower as recirculation liquid, and the other part enters the liquid nitrogen measuring tank as the output of liquid nitrogen. The oxygen-enriched liquid at the bottom of the tower is evaporated to the condensing evaporator after throttling, which is used to condense nitrogen. The evaporated oxygen-enriched air enters the turbine expansion machine for expansion after being reheated by the main heat exchanger, and the inflated oxygen-enriched air enters the main heat exchanger to cool the raw material air, providing cooling capacity for the cold box. Expansion after cold box of oxygen-rich air as purifier regeneration gas.
Waste gas expansion flow chart
II. Air forward flow expansion process
Air is filtered by air filter and then compressed into compressor to the required pressure, then cooled and separate oil and water. Compressed air is put into the precooler, and water is separated in the water separator after cooling to about 10℃. The precooled air is put into the molecular sieve adsorber to remove the residual water, carbon dioxide, acetylene and other hydrocarbon, thus obtaining pure air.
Pure compressed air first enters into the main heat exchanger of the cold box (distillation tower), and exchanges heat with the backflow low temperature gas. Part of the air passes through the supercooler, and enters the distillation tower after throttling; the other part enters the turbine expansion machine, and enters the distillation tower after expansion. The cold volume generated by expansion is used to maintain the balance of cold volume in the cold box. After the air enters the distillation tower, when the steam rises, mass transfer and heat transfer are conducted with the recirculation fluid in the tower, thus obtaining high purity nitrogen at the top of the tower and oxygen-enriched liquid at the bottom of the tower. One part of the high purity nitrogen is reheated by the main heat exchanger and then comes out of the cold box as the product nitrogen, and the other part enters into the condensing evaporator and is condensed into liquid nitrogen. Liquid nitrogen is divided into two parts. One part enters the distillation column as recirculation liquid, and the other part enters the liquid nitrogen measuring tank as the product to transport nitrogen. The evaporated oxygen-enriched air enters into the supercharging end of the turbine expansion machine after being reheated by the cooler and the main heat exchanger, and then enters into the purifier for regeneration gas.
Air expansion flow chart
Technical parameters list of pure nitrogen equipment
|
Model |
Nitrogen production/purity |
Gas and liquid nitrogen outlet tower pressure |
Liquid nitrogen production/purity |
Processing air volume |
Normal operating pressure |
Start time |
Operation Cycle (month) |
Note |
|
KDN-50 |
50/≤ 5 |
≥ 0.7 |
|
195 |
0.95 |
~ 10 |
6 |
|
|
KDN-100/6Y |
100/≤ 5 |
≥ 0.7 |
6/≤ 5 |
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