Page 225 - Analysis, Synthesis and Design of Chemical Processes, Third Edition

The cost of manufacture without depreciation, COM , is
d

(8.2)

The calculation of manufacturing costs and expenses is given in Example 8.1.

Example 8.1

The following cost information was obtained from a design for a 92,000 tonne/year nitric acid plant.

Determine
a. The manufacturing cost in $/yr and $/tonne of nitric acid
b. The percentage of manufacturing costs resulting from each cost category given in Tables 8.1 and
8.2

Using Equation 8.2,
COM = (0.180)($11,000,000) + (2.73)($300,000) +
d
(1.23)($356,000 + $1,000,000 + $7,950,000) = $14,245,000/yr
($14,245,000/yr)/(92,000 tonne/yr) = $155/tonne

From the relationships given in Table 8.2,

Direct Manufacturing Costs = $7,950,000 + $1,000,000 + $356,000 + (1.33)($300,000) + (0.069)
($11,000,000) + (0.03)($14,245,000) = $10,891,000

Percentage of manufacturing cost = (100)(10.891)/14.25 = 76%

Fixed Manufacturing Costs = (0.708)($300,000) + (0.068)($11,000,000) = $960,000

Percentage of manufacturing cost = (100)(0.960)/14.25 = 7%

General Expenses = (0.177)($300,000) + (0.009)($11,000,000) + (0.16)($14,245,000) = $2,431,000

Percentage of manufacturing cost = (100)(2.431)/14.25 = 17%

In Example 8.1, the direct costs were shown to dominate the manufacturing costs, accounting for about
76% of the manufacturing costs. Of these direct costs, the raw materials cost, the waste treatment cost,
and the cost of utilities accounted for more than $9 million of the $10.9 million direct costs. These three