Nitrogen production system for producing nitrogen with different purities and nitrogen production process thereof

A nitrogen production system, comprising:

• a heat exchanger configured to at least partially condense a compressed and purified air stream to form a cooled air stream;
• a nitrogen rectifying column configured to receive the cooled air stream and separate the cooled air stream into an oxygen enriched liquid and a nitrogen enriched top gas, the nitrogen rectifying column having a top portion, a bottom portion and a rectification section located between the top portion and the bottom portion;
• a top condenser in fluid communication with the top portion of the nitrogen rectifying column such that the top condenser is configured to receive a nitrogen-enriched top gas and condense the nitrogen-enriched top gas, and then return the condensed nitrogen-enriched top gas to the top portion as reflux, wherein the top condenser is in fluid communication with the bottom portion of the nitrogen rectifying column such that the top condenser is configured to receive an oxygen-enriched liquid from the bottom portion;
• a cold ultrahigh purity conduit in fluid communication with the top portion of the nitrogen rectifying column and the heat exchanger, wherein the ultrahigh purity conduit is configured to transfer ultrahigh purity nitrogen from the nitrogen rectifying column to the heat exchanger for warming therein;
• a cold high purity conduit in fluid communication with an intermediate section of the rectification section of the nitrogen rectifying column, wherein the high purity conduit is configured to transfer high purity nitrogen from the rectification section of the nitrogen rectifying column to the heat exchanger for warming therein, wherein the high purity nitrogen has an oxygen concentration;
• a warm ultrahigh purity conduit in fluid communication with the heat exchanger and configured to remove the ultrahigh purity nitrogen from the heat exchanger after warming therein;
• a warm high purity conduit in fluid communication with the heat exchanger and configured to remove the high purity nitrogen from the heat exchanger after warming therein;
• an oxygen concentration measurement unit in fluid communication with the warm high purity conduit and configured to measure the oxygen concentration of the high purity nitrogen;
• and
• a controller configured to indirectly determine the argon concentration of the ultrahigh purity nitrogen stream using the measured oxygen concentration of the high purity nitrogen, wherein the controller is further configured to adjust a flow rate of the ultrahigh purity nitrogen withdrawn from the nitrogen rectifying column based upon the measured oxygen concentration of the high purity nitrogen.