Reference Document on the application of Best Available

4,59

MB

Techniques to Industrial Cooling Systems (adopted Dec 2001)

335

stron

1151

ID

JRC-IPTS Instituto de Prospectiva Tecnológica (IPTS)

2002

rok

Executive summary . i

Preface 1

Scope.5

Glossary7

Thermodynamic definitions.7

Other definitions 8

Abbreviations and acronyms 13

1 General BAT concept for industrial cooling systems 15

1.1 Sources of heat, heat levels and application ranges .19

1.2 Level of cooling system and influence on process efficiency20

1.2.1 Temperature sensitive applications 20

1.2.2 Non-sensitive applications .22

1.3 Optimising the primary process and reuse of heat.22

1.3.1 Optimising the primary process .22

1.3.2 Use of waste heat off-site.23

1.4 Selecting of a cooling system in order to meet the process requirements and site conditions.23

1.4.1 Process requirements23

1.4.2 Site selection 25

1.4.3 Climatic conditions 28

1.4.4 Mathematical modelling, simulations on models and tests on pilot loops .30

1.5 Selecting a cooling technique in order to meet environmental requirements 30

1.5.1 General comparison between air and water cooled systems 30

1.5.2 Design factors and choice of materials.31

1.5.3 Options for a technological change of existing systems.32

1.5.3.1 Retrofit – reasons and considerations.33

1.5.3.2 Change of heat transfer technology 34

1.5.3.3 Replacement of outdated heat transfer technology by modern one 35

1.5.3.4 Upgrading existing heat transfer technology36

1.6 Economic considerations .37

2 Technological aspects of applied cooling systems39

2.1 Introduction .39

2.2 Heat exchangers41

2.2.1 Shell and tube heat exchangers 41

2.2.2 Plate and frame heat exchangers 41

2.2.3 Environmental issues of heat exchangers.42

2.3 Once-through cooling systems.42

2.3.1 Direct once-through cooling systems.42

2.3.2 Once-through cooling systems with cooling tower 43

2.3.3 Indirect once-through cooling systems.44

2.4 Open recirculating cooling systems.45

2.4.1 Natural draught wet cooling towers .46

2.4.2 Mechanical draught wet cooling towers.48

2.4.2.1 Forced draught wet cooling towers 49

2.4.2.2 Induced draught wet cooling towers.50

2.5 Closed circuit cooling systems 51

2.5.1 Air-cooled cooling systems51

2.5.1.1 Natural draught dry cooling tower52

2.5.1.2 Air-cooled liquid cooling systems54

2.5.1.3 Air-cooled steam condensers55

2.5.2 Closed circuit wet cooling systems 56

2.5.2.1 Mechanical draught wet closed circuit cooling systems.57

2.5.2.2 Evaporative steam condensers57

2.6 Combined wet/dry cooling systems.58

2.6.1 Open wet/dry (hybrid) cooling towers .58

2.6.2 Closed circuit hybrid cooling systems59

2.6.2.1 Sprayed (finned) coils.60

2.6.2.2 Adiabatic coolers, wetting and pre-cooling the air that cools the coils 60

2.6.2.3 Combined technology.61

2.6.2.4 Costs of hybrid systems . 61

2.7 Recirculating cooling systems. 62

2.7.1 Direct recirculating cooling systems 62

2.7.2 Indirect recirculating cooling systems . 62

2.8 Costs of cooling systems . 62

3 Environmental aspects of industrial cooling systems and applied prevention and reduction

techniques 65

3.1 Introduction 65

3.2 Consumption of energy . 67

3.2.1 Direct consumption of energy 67

3.2.2 Indirect consumption of energy . 67

3.2.3 Reduction of required energy for cooling 70

3.3 Consumption and emission of cooling water 71

3.3.1 Consumption of water . 71

3.3.1.1 Intake of water and water requirements . 71

3.3.1.2 Applied techniques to reduce water consumption 73

3.3.2 Fish entrainment 74

3.3.2.1 Level of entrainment 74

3.3.2.2 Applied reduction techniques. 75

3.3.2.3 Costs of sound devices and light systems 77

3.3.3 Heat emission to surface water 77

3.3.3.1 Levels of heat emission 77

3.3.3.2 Legislative requirements of heat emissions . 78

3.3.3.3 Applied reduction techniques. 79

3.4 Emissions from cooling water treatment. 80

3.4.1 Application of cooling water treatment . 80

3.4.2 Emissions of chemicals into the surface water 83

3.4.2.1 Oxidising biocides . 83

3.4.2.2 Non-oxidising biocides 84

3.4.2.3 Factors influencing emissions of biocides . 84

3.4.2.4 Emission levels 85

3.4.2.5 Legislation . 85

3.4.3 Reduction of emissions to the surface water 86

3.4.3.1 General approach . 86

3.4.3.2 Reduction by selection of material and systems design . 91

3.4.4 Reduction by application of additional and alternative cooling water treatment. 91

3.4.5 Reduction of emissions by assessment and selection of cooling water additives 92

3.4.6 Optimising the use of cooling water additives. 95

3.4.6.1 Dosage of cooling water additives . 96

3.4.6.1.1 Dosage regimes 96

3.4.6.1.2 Dosage systems 97

3.4.6.2 Monitoring of cooling water 98

3.4.6.2.1 Monitoring of scale inhibitors, corrosion inhibitors and dispersants 98

3.4.6.2.2 Monitoring of biofouling 99

3.5 Cooling air use and air emissions 101

3.5.1 Air requirements 101

3.5.2 Direct and indirect emissions. 101

3.5.3 Cooling tower plumes 103

3.5.3.1 Plume formation. 103

3.5.3.2 Plume abatement 103

3.6 Noise emissions 104

3.6.1 Sources of noise and noise levels 104

3.6.2 Noise abatement 107

3.6.2.1 Noise control of cascading water (wet cooling towers) . 107

3.6.2.1.1 Primary measures . 107

3.6.2.1.2 Secondary measures . 107

3.6.2.1.3 Dry-cooling towers. 108

3.6.2.2 Noise control of mechanical equipment (mechanical draught cooling towers) . 108

3.6.2.2.1 Primary measures . 108

3.6.2.2.2 Secondary measures . 109

3.6.2.3 Costs of noise reduction. 109

3.7 Risk aspects associated with industrial cooling systems110

3.7.1 Risk of leakage.110

3.7.1.1 Occurrence and consequences 110

3.7.1.2 Reduction of leakage 111

3.7.1.3 Reduction by preventive maintenance112

3.7.2 Storage and handling of chemicals.113

3.7.3 Microbiological risk.113

3.7.3.1 Occurrence of microbes113

3.7.3.2 Measuring of bacteriae .114

3.7.3.3 Techniques to reduce microbiological risks .114

3.8 Waste from cooling system operation117

3.8.1 Formation of sludges117

3.8.2 Residues from cooling water treatment and cleaning operations .117

3.8.3 Residues as a result of retrofitting, replacing and decommissioning of the installation.117

3.8.3.1 Use of plastics 118

3.8.3.2 Treatment of timber used for wet cooling tower construction118

3.8.3.3 Wet cooling tower fill.118

4 Best available techniques for industrial cooling systems 119

4.1 Introduction .119

4.2 A horizontal approach to defining BAT for cooling systems 120

4.2.1 Integrated heat management.121

4.2.1.1 Industrial cooling = Heat management.121

4.2.1.2 Reduction of the level of heat discharge by optimization of internal/external heat reuse.121

4.2.1.3 Cooling system and process requirements121

4.2.1.4 Cooling system and site requirements 123