Development and creation of an efficient Khrom-3 unit for preparing krypton-xenon mixtures

Abstract

Questions are considered for creating industrial technology for processing a primary krypton concentrate of krypton and xenon in the form of a krypton-xenon mixture. New progressive engineering solutions, protected by patents, are used in a Khrom-3 unit. The device does not contain a compression unit. The separation factor for the krypton-xenon mixture in Khrom-3 units is greater than 0.99.The start of commercial production of krypton-xenon mixtures (KXM) relates to the 1930s [1, 2]. The main work on this subject was carried out by the French firm Air Liquide and the German firm Linde together with Vereinigten Gluhlampen Elektrizitäte (Tungsram). Air Liquide constructed a krypton plant for processing 33000 m 3 /h of air in Boulogne (Paris suburb), and the unit started up in 1938. The second unit for processing 25000 m 3 /h of air was constructed by Linde in Hungary and was started up in 1938.Analysis of production schemes provided in [1] for air separation units (ASU) shows that at that time the main principles had been formulated and realized for organizing the separation of krypton from air. In particular, there was stepwise concentration of krypton with preparation of primary krypton concentrate (PKC) with an overall content of 0.1% (mol.) of krypton and xenon (under explosion hazard conditions); gasification of PKC in an evaporator; compression of PKC in a compressor; burning off hydrocarbons in catalyst furnaces followed by purifying PKC from CO 2 and moisture; separation of PKC by rectification with preparation of KXM; additional purification of KXM from hydrocarbons, CO 2 , and moisture and compression of the KXM produced in a gas generator.However, separation of air with the aim of extracting only krypton and xenon gives rise to a very high product cost. Subsequent development of cryogenic technology has governed the predominance of concepts of comprehensive separation of air when the main products are oxygen and nitrogen, and inert gases (argon, krypton, xenon) are produced in the form of secondary or supplementary separation products, which makes it possible to reduce markedly the specific capital and operating expenditure, to reduce product cost, and to increase considerably the overall production profitability.In accordance with this, in the main air separation unit there is stepwise primary concentration of krypton and xenon in the lower, upper, washing and krypton columns, the main condenser unit, the integral evaporator-condenser unit (with partial purification from hydrocarbons in liquid and gas absorbers) with preparation in air at the outlet of the evaporator of gaseous PKC with an overall content of krypton and xenon of 0.05-0.2% (mol.). Here the PKC contains 300-2500 mg C/m 3 of total hydrocarbons (mainly methane). The KXM is a product of the second stage of PKC concentration. Equipment for

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