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South African Journal of Science

versão On-line ISSN 1996-7489
versão impressa ISSN 0038-2353

S. Afr. j. sci. vol.103 no.5-6 Pretoria Mai./Jun. 2007

 

RESEARCH ARTICLES

 

On cooling-water systems design for South African industry: Two recent developments

 

 

Thokozani Majozi; Nongezile Nyathi

Department of Chemical Engineering, University of Pretoria, Pretoria 0002, South Africa

 

 


ABSTRACT

This paper presents two recent developments in the targeting and design of cooling-water systems using process integration. The basis of this work is the observation that true optimization of any cooling-water system, comprising a cooling tower and a network of operations that use cooling water, can be realized only by considering the system as a whole. Traditional approaches have focused separately on either the cooling tower or the operational network. Optimality, in the context of this paper, refers to minimum cooling-water flowrate to the network or maximum return temperature to the source of the cooling water (a cooling tower). Only systems with at least two cooling towers instead a single one are considered here, to highlight the complexity of a typical cooling-water system. The first exercise is based on a graphical technique in which targeting for the minimum cooling water precedes design of the cooling-water network to achieve the target. The second exercise uses mathematical modelling to optimize a superstructure that entails all possible topological arrangements of the cooling-water network. An industrial case study involving a South African explosives manufacturing plant is used to demonstrate the effectiveness of both techniques. Cooling-water savings of more than 20% were realized with modest capital investment.


 

 

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References

1. Linnhoff B., Mason D.R. and Wardle I. (1979). Understanding heat exchanger networks. Computers and Chemical Engineering 3, 295-302.         [ Links ]

2. El-Halwagi M.M., El-Halwagi A.M. and Manousiouthakis V. (1992). Optimal design of dephenolization networks for petroleum-refinery wastes. Trans. IChemE 70b, 131-139.         [ Links ]

3. Wang Y.P. and Smith R. (1994). Wastewater minimization. Chemical Engineering Science 49, 981-1006.         [ Links ]

4. Wang Y.P. and Smith R. (1995). Time pinchanalysis. Trans. IChem E 73a, 905-914.         [ Links ]

5. Wang Y.P. and Smith R. (1995). Waste minimization with flowrate constraints. Trans. IChemE 73, 889-904.         [ Links ]

6. Olesen S.G. and Polley G.T. (1997). A simple methodology for the design of water networks handling single contaminants. Trans. IChemE 75a, 420-426.         [ Links ]

7. Doyle S.J. and Smith R. (1997). Targeting water reuse with multiple contaminants. Trans. IChemE 75b, 181-189.         [ Links ]

8. Alva-Argáez A., Kokossis A.C. and Smith R. (1998). Wastewater minimization of industrial systems using an integrated approach. Computers and Chemical Engineering 22 (Suppl.), S741-S744.         [ Links ]

9. Savelski M.J. and Bagajewicz M.J. (2000). On the optimality conditions of water utilization systems in process plants with single contaminants. Chem. EngngSci. 55, 5035-5048.         [ Links ]

10. Jödicke G., Fischer U. and Hungerbühler K. (2001). Wastewater reuse: a new approach to screen for designs with minimal total costs. Computers and Chemical Engineering 25, 203-215.         [ Links ]

11. Hallale N. (2002). A new graphical targeting method for water minimization. Adv. Environ. Res. 6, 377-390.         [ Links ]

12. Kasperski M. and Niemann H-J. (1988). On the correlation of dynamic wind loads and structural response of natural-draught cooling towers. J. Wind Engng Ind. Aerodyn. 30(1-3), 67-75.         [ Links ]

13. Bartoli G., Borri C. and Zahlten W (1992). Nonlinear dynamic analysis of cooling towers under stochastic wind loading. J. Wind Engng Ind. Aerodyn. 43(1-3), 2187-2198.         [ Links ]

14. Wittek U. and Meiswinkel R. (1998). Non-linear behaviour of RC cooling towers and its effects on the structural design. Engineering Structures 20(10), 890-898.         [ Links ]

15. Sudret B., Defaux G. and Pendola M. (2005). Time variant finite element reliability analysis - application to the durability of cooling towers. Structural Safety 27, 93-112.         [ Links ]

16. Soylemez M.S. (2001). On the optimum sizing of cooling towers. Energy Conserv. Mngt 42, 783-789.         [ Links ]

17. Knoche K.F. and Bosnjakovic F. (1998). Pinch analysis for cooling towers. Energy Conserv. Mngt 39, 1745-1752.         [ Links ]

18. Martinez S.S., Gallegos A.A. and Martinez E. (2004). Electrolytically generated silver and copper ions to treat cooling water: an environmentally friendly novel alternative. Int. J. Hydrogen Energy 29, 921-932.         [ Links ]

19. Kim J.K. and Smith R. (2001). Cooling water system design. Chem. Engng Sci. 56, 3641-3658.         [ Links ]

20. Bernier M.A. (1994). Cooling tower performance: Theory and experiments. ASHRAE Transactions Res. 100, 114-121.         [ Links ]

 

 

Received 13 January 2005.
Accepted 12 January 2007.

 

 

Author for correspondence. E-mail: thoko.majozi@up.ac.za

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