Preparation of a low temperature liquid adsorbent water removal material

Abstract

The present application is a kind of liquid nitrogen water removal material, which has the function of purifying finished liquid nitrogen. The material is mixed by silica alumina gel and magnetic powder. During purification, the material is loaded into a fixed bed adsorber, and liquid nitrogen is passed through the adsorber at a certain pressure. After circulation, the water content of the low-temperature liquid nitrogen is less than 0.5 ppm, meeting the use requirements. The present application will play an important role in the field of aerospace.

Description

Technical Field

[0001] This invention belongs to the field of adsorption technology and relates to water removal adsorption materials for cryogenic liquids (such as liquid nitrogen, liquid oxygen, etc.). Background Technology

[0002] Adsorption dehydration materials are commonly used in the chemical industry. They are materials that remove impurities from gases or liquids through adsorption.

[0003] The water content in cryogenic liquids is a crucial indicator of their quality. Excessive water content can severely impact their usability. Generally, during the preparation of liquid nitrogen, specifically the liquefaction of air, moisture in the air is removed while the liquid nitrogen is in its gaseous state. Before leaving the factory after air separation, the water content of liquid nitrogen can reach a certain standard. Currently, the national requirement for pure nitrogen is a water content of 15 ppm (10...). -6 For high-purity nitrogen, the water content requirement is below 3 ppm (mole fraction), and for ultrapure nitrogen, it is below 0.5 ppm. However, the equipment requirements for preparing high-purity and ultrapure nitrogen are extremely stringent, and the cost is also high.

[0004] On the other hand, before being used, liquid nitrogen undergoes a series of operations such as transfer, storage, and transportation. Due to the concentration diffusion effect of the pipe walls, some water contamination is inevitable, thus increasing the water content of the liquid nitrogen before use. Currently, many applications require the water content of liquid nitrogen to be 0.5 ppm or even lower, which necessitates further dehydration of the finished liquid nitrogen after it leaves the factory.

[0005] Traditional adsorbents are used to remove moisture from gases, but their adsorption depth does not reach the required 0.5 ppm. Therefore, it is necessary to improve the interaction between the adsorbent and the adsorbate, and increase its adsorption potential, thereby reducing the water content in liquid nitrogen to the required level.

[0006] The main advantages of this invention are as follows: (1) it can remove water from the finished cryogenic liquid; (2) it can reduce the water content of the cryogenic liquid to below 0.5 ppm to meet the requirements of use under some extreme conditions. Summary of the Invention

[0007] This invention is a cryogenic liquid dehydration adsorbent, the purpose of which is to remove water from cryogenic liquids with high water content requirements, thereby meeting the application requirements.

[0008] The technical solution for the purpose of this invention is as follows: the adsorbent (silica-alumina gel) and magnetic powder are uniformly mixed (the weight ratio is 1:1), and a fixed-bed adsorber is used to fill the mixture. The cryogenic liquid is then passed through the adsorber at a certain pressure. After circulating through the adsorber, the resulting cryogenic liquid has a water content of less than 0.5 ppm. Attached Figure Description

[0009] Figure 1 The graph shows the results of liquid nitrogen dehydration according to the present invention. In the graph, blue represents the water content of liquid nitrogen before dehydration, and red represents the water content of liquid nitrogen after dehydration using the adsorbent of the present invention.

[0010] During measurement, due to contamination of the pipeline and the liquid nitrogen itself, the measured water content of the liquid nitrogen continuously decreases with increasing purging time. However, when it drops to close to 1 ppm, further purging will not result in a further decrease in water content. After dehydration, the water content will decrease to below 0.5 ppm over time. Detailed Implementation

[0011] Specific Implementation Example 1: The present invention will be further described below.

[0012] The liquid nitrogen dehydration material of this invention is mainly composed of silica-alumina gel and magnetic powder. The silica-alumina gel and magnetic powder are mixed evenly in a 1:1 weight ratio, dried in a vacuum drying oven at 150°C for 24 hours, and then filled into a fixed-bed adsorber. Filling should be done in a dry environment, and both ends of the adsorber should be sealed before starting the adsorber. After the equipment is installed, the adsorber is turned on, and liquid nitrogen is passed through the adsorber at a certain pressure. After several hours of circulation, the water content will drop to below 0.5 ppm. The circulation time is adjusted according to the amount of liquid nitrogen and the adsorption dosage.

Claims

1. A method for preparing an adsorbent material for dehydration of cryogenic liquids, characterized in that, The adsorbent material is obtained by mixing silica-alumina gel and magnetic powder in a weight ratio of 1:

1. Before use, the adsorbent material is vacuum dried at 150°C for more than 24 hours, stirred evenly, and then placed into the adsorber to adsorb moisture from liquid nitrogen. The final water content can reach below 0.5 ppm.

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