TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Process: In the rectifying process for extracting xenon-krypton from liquid oxygen, the bottom of the first stage rectifying tower is provided with a reboiler and the top is provided with a condensing evaporator; the nitrogen is introduced to the rectifying tower and cooled by a main heat exchanger, introduced to the reboiler at the bottom of the first stage rectifying tower, and used as heat source; the nitrogen is further cooled to become liquid nitrogen that is throttled and depressurized; a part of liquid nitrogen is extracted and introduced to the condensing evaporator at the tower top of the first stage rectifying tower as cold source, and a part of liquid nitrogen enters the nitrogen washing tower directly; the low-temperature nitrogen at an outlet of the condensing evaporator of the first stage rectifying tower reheats and enters the nitrogen washing tower; the bottom of the second stage rectifying tower is provided with a reboiler and the top is provided with a condensing evaporator; after the nitrogen is cooled by a main heat exchanger, a part of nitrogen is introduced to the reboiler at the tower bottom of the second stage rectifying tower and used as heat source, and another part of nitrogen is cooled to liquid nitrogen; after the liquid nitrogen is throttled and depressurized, a part of liquid nitrogen is extracted and introduced to the condensing evaporator at the tower top of the second stage rectifying tower and used as cold source; a part of liquid nitrogen is introduced to a condensing evaporator of a methane removing tower and used as cold source, and the rest of liquid nitrogen is collected and discharged as product; the cold source of each of the third stage rectifying tower, the fourth stage rectifying tower, the fifth stage rectifying tower, the sixth stage rectifying tower, and the seventh stage rectifying tower adopts the gas formed by mixing low-temperature nitrogen and normal-temperature nitrogen, which avoids solidifying xenon-krypton due to over-low temperature of cold source; the nitrogen discharged from the condensing evaporator at the tower top of each stage rectifying tower joins to return the main heat exchanger together to recycle the cold amount; and the rectifying tower, a low-temperature pipeline for connecting rectifying towers, and a valve are contained in a cold box filled with insulating material. Preferred Components: The insulating material comprises extra-fine glass wool or expanded perlite.