Compressors for gas recovery

The recovery and repressurisation of solvent gas following depressurisation of a section of plant, which has already been discussed (section 9.2.2) for discontinuous extraction processes, can be necessary for economic or antipollution reasons. As the necessary gas compressors do not usually form a very important part of the plant, the discussion below will be limited to some basic considerations. 

For gas recompression operations dry-running piston machines (non-lubricated) must be used. The compression ratio during the recompression operation will typically increase from a very low value to about 20 as the inlet pressure progressively decreases. Two or three compressor-stages with intercooling are therefore usual. At the end of the recompression operation the compressor inlet pressure may be as low as 3 bar, while the outlet is at 70 bar. The volume flow (measured at NTP) may be as high as 30 000 m /h. 

The author wishes to thank H. Gernandt, Neuman and Esser, D-5132, Ubach-Palenberg for assisting in the preparation of this section. 

Quirin, K.W. and Gerad, D. (1987) Dense Gases for Extraction and Refining (English edition translated by M.R.F. Ashworth), Springer-Verlag, Berlin. 

Matson, D.W., Fulton, J.L., Petersen, R.C. and Smith, R.D. (1987), Rapid Expansion of Supercritical Fluid Solution Solute Formation of Powder, Thin Films and Filters, Ind. Eng. Chem. Res., p. 2298. 

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