A purification method for ultra-pure ammonia full-temperature adsorption extraction deep dehydration and impurity removal

Abstract

The invention discloses a full-temperature-range adsorption, extraction, deep dehydration and impurity-removing purification method for ultrapure ammonia. The method comprises the processes of liquidphase adsorption, extraction and desorption, extraction agent regeneration and shallow cold rectification, and particularly comprises the following steps: performing a pretreatment process on industrial-grade liquid ammonia to obtain 5N-grade (purity is higher than or equal to 99.999 percent) liquid ammonia, entering the liquid phase adsorption process, adsorbing water and trace impurity components in the raw materials by an adsorption tower, and removing impurity components taking oxygen and nitrogen as main components by the shallow cold rectification process to obtain ultrapure ammonia withthe purity being 7N grade; and after the liquid phase adsorption process is completed, introducing into the adsorption tower, performing the extraction and desorption process and dissolving out waterand trace impurity components from the materials adsorbed in an adsorbent and a dead space in the adsorption tower. The extraction and desorption gas enriched with water and trace impurity componentsenters the extraction agent regeneration process for regeneration and then returns to the extraction and desorption process for recycling. The adsorption-extraction and desorption process is adopted,and the adsorption mechanism and the extraction, desorption and dissolution mechanism are combined, so that the purity of the prepared ultrapure ammonia product is higher than or equal to 7N grade and the yield can reach 98 to 99 percent.

Description

technical field [0001] The invention belongs to the technical field of separation and purification of chemical industry, and more specifically relates to a purification method of full-temperature absorption, extraction, deep dehydration and impurity removal of ultra-pure ammonia. Background technique [0002] Ultra-pure ammonia (purity ≥ 99.99999% (7N)) is one of the important gas materials required by the electronics industry. It is mainly used in the preparation of silicon nitride films for semiconductor component integration and gallium nitride light-emitting diodes (LEDs). One of the main impurity content limit indicators for ultra-pure ammonia: carbon dioxide and carbon monoxide (CO2+CO) ≤ 60ppbv, argon (Ar) ≤ 10ppbv, hydrogen (H2) ≤ 50ppbv, oxygen (O2) ≤ 10ppbv, methane (CH4) ≤ 10ppbv , water (H2O) ≤ 1ppbv, and other impurities are mostly metals. Among them, the impurities that have the greatest impact on silicon nitride films and gallium nitride chips in ultra-pure a...

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Problems solved by technology

Although the water content index of the normal ammonia gas flowing out during the adsorption process is guaranteed by letting go of the purified ammonia gas flowing out of the initial adsorption process, it is difficult to determine the outflow time at the initial stage of adsorption, and it is impossible to fundamentally solve the problem of the adsorbent in the process of adsorption and regeneration. The difference in the two kinds of equilibrium adsorption capacity will also waste the yield of ultra-pure ammonia; secondly, due to the introduction of new regeneration media N2 and H2 in the system, which are relatively close to the physical properties of O2, the subsequent low-temperature rectification operation load and The increase in separation difficulty affects the quality of the final ultra-pure ammonia; third, the two-stage adsorption adopts the traditional temperature swing adsorption (TSA), which needs to realize the cyclic operation of adsorption and desorption regeneration through temperature changes, which makes it difficult to match the adsorption and desorption with Balance, temperature stress also greatly reduces the service life of the adsorbent; fourth, the energy efficiency ratio of the process is uneconomical and reasonable: since the sequence of each unit in the process is normal temperature liquid phase adsorption, evaporation, gas phase adsorption, and low temperature rectification, the operating temperature It also shows periodic changes of normal temperature, high temperature, high temperature, low temperature, etc., and in the secondary adsorption, it also requires a certain temperature adsorption and a higher temperature regeneration. The periodic changes of the adsorption itself, the energy utilization efficiency is very low; fifth, In the final low-temperature rectification process, after condensing and cooling the higher-temperature gas flowing out from the gas phase adsorption, there will be residual and trace amounts of saturated equilibrium moisture, which will enter the low-temperature rectification process, affecting the purity of the ultra-pure ammonia flowing out from the bottom of the tank

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