Air is a mixture of various gases like as nitrogen, oxygen, argon, hydrogen, helium, neon, krypton, etc. These gases can be separated at cryogenics temperature by liquefying the components at different temperature & pressure. This paper presents the latest technology in bulk production of high purity of nitrogen, oxygen & argon from air, and analytical process design for a 1250 ton / day plant and comparing the data with actual existing plants. The liquefaction of air to produce oxygen was the first engineering application of cryogenics1 and was initially used around the beginning of this century. Today, four-quarters of a century later, it is useful to conduct a review of air separation plant design. This paper summarizes the considerations for analytical design, & materials of construction for air plant design.
[...] AIR BOOSTER SEPARATION It is then cooled in the main heat exchanger (E3116) against a stream of internally compressed liquid oxygen which is, in turn, evaporated and warmed up. To cover the refrigeration requirement of the process, part of the boosted air is taken, after the intercooler, from an intermediate stage of the booster air compressor, transferred to the main exchanger (E3116) and withdrawn from the middle section after having been cooled against returning products. It is then expanded in the expansion turbine (X3471, generator braked), passed through the liquid / gas separator 3432) and fed into the bottom of the low pressure column (T3211). [...]
[...] The liquid argon is pumped from this storage tank to the required product gas pressure and is passed back to the main exchanger (E3116) of the air separation cold box where it is vaporised as product argon gas. DESIGN OF RECTIFICATION COLUMN If the feed mixture contains more than two components, then select two key components from all the components of feed mixture Decide the operating pressure of the distillation column. At the operating pressure, find the vapour-liquid equilibrium data. [...]
[...] Under normal operating conditions, parts of the air separation plant will be operating at temperatures around 90 K. All metals become stronger at these temperatures, but some become more brittle. The problem of brittle fracture is of prime importance in selecting the proper material of construction. Typical materials used in air separation plants are copper; aluminum alloys, austenitic stainless steel, and nickel steel. After eliminating metals and alloys subject to brittle failure, the choice is determined by economic considerations. Stress values and relative economics are presented in reference 56. [...]
[...] α iXid = Rm + 1 Determine the optimum reflux ratio R and find the number of theoretical or equilibrium stages required for the desired separation by following equations11 Figure1 Flow Process Chart = Part of the oxygen free crude argon yielding at the top of the crude argon column (T4110) is withdrawn and fed into the pure argon column (T4112). The oxygen rich liquid collected in the bottom of the primary argon column is fed back to the low pressure column (T3212) by the LOX reflux pump (P4565).In the pure argon column (T4112) with condenser (E4118), the remaining nitrogen content is removed by means of cryogenic rectification. [...]
[...] CONSIDERATION FOR BASIC PROCESS CYCLE SELECTION OF Air separation technology is used for the production of oxygen, nitrogen, and the rare gases that are present in air. Product requirements determine the selection of the process. These include the specific product compositions and purities of the products, their physical state that is gas or liquid, their delivery pressures, and the production rates. The cost of power exerts a major influence on the process selection. Oxygen has been produced commercially by several methods - dissociation of water, selective adsorption, chemical reactions, and cryogenic separation. [...]
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