Page 212 - Analysis, Synthesis and Design of Chemical Processes, Third Edition

From Table A.5,

C BM = C NF BM q
f
p
N = 40
f = 1.0 (since number of trays > 20, Table A.5)
q

From Table A.6, SS sieve trays identification number = 61; from Figure A.9, F BM = 1.83

C BM,trays (2006) = ($5,756)(40)(1.83)(1.0) = $421,300

For the tower plus trays,

C BM,tower+trays (2006) = $6,486,000 + $ 421,300 = $ 6,908,300

7.3.7 Grass Roots and Total Module Costs

The term grass roots refers to a completely new facility in which we start the construction on essentially
undeveloped land, a grass field. The term total module cost refers to the cost of making small-to-
moderate expansions or alterations to an existing facility.

To estimate these costs, it is necessary to account for other costs in addition to the direct and indirect
costs. These additional costs were presented in Table 7.6 and can be divided into two groups.
Group 1: Contingency and Fee Costs: The contingency cost varies depending on the reliability of
the cost data and completeness of the process flowsheet available. This factor is included in the
evaluation of the cost as a protection against oversights and faulty information. Unless otherwise
stated, values of 15% and 3% of the bare module cost are assumed for contingency costs and fees,
respectively. These are appropriate for systems that are well understood. Adding these costs to the
bare module cost provides the total module cost.

Group 2: Auxiliary Facilities Costs: These include costs for site development, auxiliary buildings,
and off-sites and utilities. These terms are generally unaffected by the materials of construction or
the operating pressure of the process. A review of costs for these auxiliary facilities by Miller [17]
gives a range of approximately 20% to more than 100% of the bare module cost. Unless otherwise
stated, these costs are assumed to be equal to 50% of the bare module costs for the base case
conditions. Adding these costs to the total module cost provides the grassroots cost.

The total module cost can be evaluated from

(7.15)

and the grassroots cost can be evaluated from