Separation systems, air

AIR SEPARATION SYSTEMS 6.4.1. Linde Single-Column System 

The Linde single-column system introduced in 1902 is the simplest air-separation system used. In this scheme, shown in Fig. 6.23, water vapor and carbon dioxide are removed from the air after the latter has been compressed isothermally. The air then passes through a precooling heat exchanger. This 

The Linde single-column separation system is obtained by replacing the liquid reservoir of the simple Linde liquefaction cycle with a stripping column. However, any of the other liquefaction processes could be used just as well to furnish liquid for the column. 

Solution. To make an overall mass balance around the column, it will be necessary to determine the composition of the nitrogen stream leaving the top of the column. This will involve determining the temperature of the feed since Tj = Tjr h0.5 K. This 

To complete the flash calculation, temperatures must be assumed until Eq. (6.25) is balanced (see Example 6.7). A temperature of 79.01 K satisfies the relation with a nitrogen vapor mole fraction of 0.930. With the aid of Eqs. (6.21) and (6.22) and Td = 79.51 K, we can now determine (following the procedure in Example 6.4) that the product stream leaving the top of the column has a nitrogen mole fraction of 0.908. This permits solution of the overall and component balance around the column represented by 

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This process was developed by industry and refined by the U.S. Naval Academy (USNA). The equipment used is a Gayco-Reliance air separator system, built by Universal Road Machinery. This technology is not currently commercially available. 

Dow (Generon) separation installed -1994 produces first N air separation system -1982... 

Since helium and neon have boiling points considerably below that of nitrogen, these gases will collect on the nitrogen side of the condenser-reboiler associated with the double-column air separation system. Recovery of these gases is accomplished by periodic venting of a small portion of the gas from the dome of the condenser and transfer to a small condenser-rectifier refrigerated with... 

A self-contained, skid-mounted membrane air-separation system is commercially available that generates nitrogen at flow rates of up to 2431 L (643 gal ... 

High-pressure systems in the vicinity of critical points, such as synthesis gas and air separation systems, remain a challenge. Our flash algorithm has difficulty in identifying the correct phase state, or converging to the correct vapor-Uquid solutions. This problem may be exacerbated by the difficulty in obtaining the equation of state volume root in the vicinity of the critical points. Further work to improve the algorithm and the equation of state volume root determination is required. It is believed that the homotopy continuation methods are probably better suited for calculations near the critical points. 

The block of inter-linked columns offers robust simulation of a combination of complex distillation columns, as heat-integrated columns, air separation system, absorber/stripper devices, extractive distillation with solvent recycle, fractionator/quench tower, etc. Because sequential solution of inter-linked columns could arise convergence problems, a more robust solution is obtained by the simultaneous solution of the assembly of modelling equations of different columns. 

A small amount of liquid oxygen and liquid nitrogen can be drawn off the air separation system from the distillation columns. However, to produce quantities larger than about 2 wt% of the air feed to the unit, a product liquefier is required. 

Steam stripping, which is widely used in the regeneration of solvent recovery systems using an activated carbon adsorbent, can be considered as a combination of thermal swing and displacement desorption. Vacuum desorption, which is used in some versions of the Union Carbide IsoSiv process for separation of medium-chain linear paraffins as well as in some air separation systems can be considered as a special case of pressure swing. 

The Heylandt system, shown in Fig. 6.30, is an air-separation system commonly used for the production of liquid nitrogen and liquid oxygen. A... 

After a double-column air-separation system has been in continuous operation over long periods of time, the effectiveness of the heat transfer in the condenser-reboiler is observed to decrease. This is attributed to the gradual accumulation of neon and helium in the nitrogen, which lowers the partial pressure of the nitrogen so that it will not condense at the condenser design temperature. This problem can be solved by periodically venting some of the accumulated gas from the dome of the condenser either to the atmosphere or to a neon-separation system. 

Fig. 6.33. Neon-recovery subsystem. Crude neon and helium are recovered from the dome of the lower-column condenser in a double-column air separation system.

Air is compressed isothermally from 0.101 MPa and 300 K to 20.26 MPa in a Linde singlecolumn air-separation system. The overall efficiency of the compressor is 65%. The composition of the feed stream is 79% nitrogen and 21% oxygen by volume. The high-pressure... 

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