Page 306 - Chemical engineering design

COSTING AND PROJECT EVALUATION
4. A floating roof storage tank, capacity 50,000 m
5. A cone roof storage tank, capacity 35,000 m 3 3 281
6.8. A storage tank is purged continuously with a stream of nitrogen. The purge
stream leaving the tank is saturated with the product stored in the tank. A major
part of the product lost in the purge could be recovered by installing a scrubbing
tower to absorb the product in a solvent. The solution from the tower could be
fed to a stage in the production process, and the product and solvent recovered
without significant additional cost. A preliminary design of the purge recovery
system has been made. It would consist of:
1. A small tower 0.5 m diameter, 4 m high, packed with 25 mm ceramic saddles,
packed height 3 m.
3
2. A small storage tank for the solution, 5 m capacity.
3. The necessary pipe work, pump, and instrumentation.
All materials of construction, carbon steel.
Using the following data, evaluate whether it would be economical to install the
recovery system:
1. cost of product £5 per kg,
2. cost of solvent 20 p/kg,
3. additional solvent make-up 10 kg/d,
4. current loss of product 0.7 kg/h,
5. anticipated recovery of product 80 per cent,
6. additional service(utility) costs, negligible.
Other operating costs will be insignificant.
6.9. Make a rough estimate of the cost of steam per ton, produced from a packaged
boiler. 10,000 kg per hour of steam are required at 15 bar. Natural gas will be
3
used as the fuel, calorific value 39 MJ/m . Take the boiler efficiency as 80 per
cent. No condensate will be returned to the boiler.
6.10. The production of methyl ethyl ketone (MEK) is described in Appendix G,
problem G.3. A preliminary design has been made for a plant to produce 10,000
tonne per year. The major equipment items required are listed below. The plant
attainment will be 8000 hours per year.
Estimate the capital required for this project, and the production cost.
The plant will be built on an existing site with adequate resources to provide the
ancillary requirements of the new plant.
Major equipment items

1. Butanol vaporiser: shell and tube heat exchanger, kettle type, heat transfer
2
area 15 m , design pressure 5 bar, materials carbon steel.
2. Reactor feed heaters, two off: shell and tube, fixed head, heat transfer area
2
25 m , design pressure 5 bar, materials stainless steel.
3. Reactor, three off: shell and tube construction, fixed tube sheets, heat transfer
2
area 50 m , design pressure 5 bar, materials stainless steel.