Page 292 - Chemical engineering design

Table 6.6.
Summary of production costs
Typical values
Variable costs COSTING AND PROJECT EVALUATION 267
1. Raw materials from flow-sheets
2. Miscellaneous materials 10 per cent of item (5)
3. Utilities from flow-sheet
4. Shipping and packaging usually negligible
Sub-total A ... .... ... .... ... .... .
Fixed costs
5. Maintenance 5 10 per cent of fixed capital
6. Operating labour from manning estimates
7. Laboratory costs 20 23 per cent of 6
8. Supervision 20 per cent of item (6)
9. Plant overheads 50 per cent of item (6)
10. Capital charges 10 per cent of the fixed capital
11. Insurance 1 per cent of the fixed capital
12. Local taxes 2 per cent of the fixed capital
13. Royalties 1 per cent of the fixed capital
Sub-total B ... .... ... .... ... .... .
Direct production costs A + B ... .... ... .... ... .... .
13. Sales expense 20 30 per cent of the direct
14. General overheads production cost
15. Research and development
Sub-total C ... .... ... .... ... .... .
Annual production cost D A C B C C D ... .... ... .... ... .... .
Annual production cost
Production cost £/kg D
Annual production rate

Example 6.4

Preliminary design work has been done on a process to recover a valuable product from
an effluent gas stream. The gas will be scrubbed with a solvent in a packed column;
the recovered product and solvent separated by distillation; and the solvent cooled and
recycled. The major items of equipment that will be required are detailed below.
1. Absorption column: diameter 1 m, vessel overall height 15 m, packed height 12 m,
packing 25 mm ceramic intalox saddles, vessel carbon steel, operating pressure 5 bar.
2. Recovery column: diameter 1 m, vessel overall height 20 m, 35 sieve plates, vessel
and plates stainless steel, operating pressure 1 bar.
2
3. Reboiler: forced convection type, fixed tube sheets, area 18.6m , carbon steel shell,
stainless-steel tubes, operating pressure 1 bar.
2
4. Condenser: fixed tube sheets, area 25.3m , carbon steel shell and tubes, operating
pressure 1 bar.
2
5. Recycle solvent cooler: U-tubes, area 10.1m , carbon steel shell and tubes, operating
pressure 5 bar.
3
6. Solvent and product storage tanks: cone roof, capacity 35 m , carbon steel.
Estimated service requirements:
Steam 200 kg/h
Cooling water 5000 kg/h
Electrical power 100 kWh/d (360 MJ/d)