Absorption columns costs

Duplex stainless steels (ca 4% nickel, 23% chrome) have been identified as having potential appHcation to nitric acid service (75). Because they have a lower nickel and higher chromium content than typical austenitic steels, they provide the ductabdity of austenitic SS and the stress—corrosion cracking resistance of ferritic SS. The higher strength and corrosion resistance of duplex steel offer potential cost advantages as a material of constmction for absorption columns (see CORROSION AND CORROSION CONTROL). 

The installed cost,, of the absorption column (including auxiliaries, but excluding packing) is given by... 

The absorption column and its associated structures (platforms, ladders and railings) are expected to cost in the region of AS870 000. The final design comparesfavourably with similar units already found in industry. 

The final cost estimate for this absorption column and associated structures was determined to be As870 000. This is significantly more than the first estimate (As250 000), however, the new cost reflects the need for a larger column than originally considered. 

The costs of the two sieve-plate columns (absorption column and product bleaching column) are estimated according to the recommendations presented in Ref. CE9 (p.389). The columns are costed according to their diameter, operating pressure, and the number of sieve trays. 

The absorption column operates at about 10 bar and is estimated (Ref. PT2) to be 2m in diameter with 50 trays. At US 1850/tray, the cost isapproximately USS95 500. Including the cost of providing two separate cooling circuits in the column, the cost increases to... 

Cbcc Base cost for absorption-column cooling circuit. i... 

Cbt Base unit-cost per absorption-column tray. ... 

The absorption column is sized according to two key parameters, these are to design for optimum mass transfer and optimum unit cost. A column internal diameter can be estimated according to the liquid and gas flowrates by utilizing graphs and nomographs such as those contained in Ref. A3. These recommendations have been refined using a computer-based mathematical model. The model predicts the required number of trays for a specified column internal diameter. These results enable a compromise to be achieved between tower cost and tower performance. 

Separation S02/02 requires two absorption columns. Only one column is shown in Figure 2, the second one finishing S02 absorption before exhausting (or valorisation of oxygen which is not taken into account therein). This section also requires heat exchangers and compressors. Cost of installed chemical equipment with piping, instrumentation, buildings, etc. is about EUR 223.8 M. 

Duplex stainless steels (4% nickel, 23% chrome) may offer cost advantages in absorption columns. These materials provide the ductability of austenitic stainless and the stress-corrosion cracking resistance of ferritic stainless steel104. 

The results of this work were consistent with those of Jalili and Mather [8-11], with the solubility of H S found to increase with increasing pressure and decrease with increasing temperature. It was found that H S could be more readily removed from the gas stream than CO, due to a higher solubility in the IL and higher rate of mass transfer, potentially enabling some reductions in process costs as a shorter absorption column could be used to separate H S from CO [3],... 

Random-packed absorption columns have seldom been used for large commercial-size dehydrators because of the very low liquid flow rates usually employed. As pointed out in Chapter I, a low liquid flow rate normally leads to the selection of a bubble-cap column. The recent trend toward extremely low dew-point requirements (-40°F and below) has resulted in a reexamination of contactor designs to attain more theoretical stages at a reasonable cost. Structured packing, which is offered by several vendors, is claimed to offer greatly increased throughput, lower pressure drop, and lower column height than bubble-cap trays for the same service. 

For high natural gas flows combined with high carbon dioxide content an association of membranes and absorption seems to be the most profitable option. Membrane modules, located before the absorption column, carry out a bulk removal of carbon dioxide, while the absorption columns allow the final polishing of the natural gas. This configuration leads to significant investment cost reductions on the absorption unit. 

For gas absorption, the water or other solvent must be treated to remove the captured pollutant from the solution. The effluent from the column may be recycled into the system and used again. This is usually the case if the solvent is costly (e.g., hydrocarbon oils, caustic solutions, amphiphilic block copolymer). Initially, the recycle stream may go to a treatment system to remove the pollutants or the reaction product. Make-up solvent may then be added before the liquid stream reenters the column. 

Determining the number of theoretical and actual trays in a distillation column is only part of the design necessary to ensure system performance. The interpretation of distillation, absorption, or stripping requirements into a mechanical vessel with internal components (trays or packing, see Chapter 9) to carry out the function requires use of theoretical and empirical data. The costs of this equipment are markedly influenced by the column diameter and the intricacies of the trays, such as caps, risers, weirs, downcomers, perforations, etc. Calcvdated tray efficiencies for determination of actual trays can be lost by any unbalanced and improperly designed tray. 

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