Table of contents
ANNEX ITHERMODYNAMIC PRINCIPLES... 155 I.1 Heat transfer in a shell and tube heat exchanger ... 155 I.2 Approach... 156 I.3 Capacity of a heat exchanger ... 157 I.4 Wet and dry bulb temperatures ... 158 I.5 Relation between heat transfer and heat exchanging surface ... 158 ANNEX IIPRINCIPLE OF ENERGY SAVING THROUGH OPTIMISED COOLING... 161 II.1 Subject... 161 II.2 Summary of conclusions ... 161 II.3 Introduction... 162 II.4 Calculations... 164 II.4.1 Principles ... 164 II.4.2 Quantity of cooling water ... 166 II.4.3 Quantity of cooling air ... 167 II.4.4 Product temperature; gas volume ... 168 II.4.5 Product pressure; cooling compressor ... 169 II.5 Total potential energy conservation per °C colder cooling-water boundary layer ... 170 II.5.1 Efficiency of power generation ... 170 II.5.2 Total water used for cooling in the Dutch industry (excl. power plants)... 171 II.5.3 Total potential energy conservation per °C colder cooling-water boundary layer ... 172 II.6 Examples of calculations for the relative conservation of energy and reduction of the
environmental impact achieved by the use of inhibitors ... 173 II.6.1 The contribution made by oxidation... 173 II.6.1.1 Once-through cooling system ... 173 II.6.1.2 Open recirculating system... 174 II.7 Examples of calculations of the relative savings in energy with colder cooling water ... 176 II.7.1 Coastal water versus cooling towers... 176 II.7.2 River water versus cooling towers... 176 II.7.3 Groundwater versus cooling tower ... 177 II.8 Appendix environmental impacts... 177 ANNEX III SHELL AND TUBE HEAT EXCHANGERS FOR INDUSTRIAL
ONCE-THROUGH COOLING SYSTEMS AND THE OCCURRENCE OF LEAKAGE... 179 III.1 Design of the shell & tube heat exchanger for one through systems... 180 III.2 Leakage in shell & tube heat exchangers ... 182 III.3 Alternatives ... 183 ANNEX IV BEISPIEL FÜR DIE AUSWAHL VON MATERIAL FÜR
KÜHLWASSER-SYSTEME IN INDUSTRIELLEN ANWENDUNGEN (AUSSER KRAFTWERKEN) ... 185 IV.1 Einführung ... 185 IV.2 Direkte Durchlaufsysteme (mit Brackwasser)... 186 IV.3 Durchlaufsysteme mit sekundärem Kühlkreislauf (Brackwasser/entmineralisiertes Wasser) 188 IV.4 Offene rezirkulierende Kühlsysteme... 189 IV.4.1 Anwendung von Süßwasser in offenen Nasskühltürmen ... 189 IV.4.2 Anwendung von Salzwasser in offenen Nasskühltürmen... 189 ANNEX VOVERVIEW OF CHEMICALS FOR THE CONDITIONING OF COOLING
WATER SYSTEMS ... 191 V.1 Corrosion inhibitors ... 191 V.1.1 Corrosion ... 191 V.1.2 Applied corrosion inhibitors... 191 V.2 Scale inhibitors... 192 V.2.1 Scaling ... 192 V.2.2 Applied scale inhibition... 192 V.3 Fouling inhibitors (dispersants)... 193 V.3.1 Fouling... 193 V.3.2 Applied fouling inhibitors ... 194 V.4 Biocides... 194 V.4.1 Biofouling... 194 V.4.2 Applied biocidal treatment ... 197 V.4.3 Oxidising biocides ... 197 V.4.4 Non-oxidising biocides... 199 V.4.5 Factors determining the use of biocides. ... 200
V.4.6 Interactions with other water treatment chemicals...202
V.5 Cycles of concentration and water balance...202
ANNEX VI EXAMPLE OF LEGISLATION IN EUROPEAN MEMBER STATES ...205
ANNEX VIIEXAMPLE OF A SAFETY CONCEPT FOR OPEN WET COOLING SYSTEMS (VCI-CONCEPT)...209
VII.1 Introduction to the concept ...209
VII.2 Requirements of the concept...211
VII.3 Appendix 1 - Automatic analytical monitoring of once-through cooling systems ...213
VII.4 Appendix 2 – R-phrases used to calculate VCI-score...214
ANNEX VIII EXAMPLES FOR THE ASSESSMENT OF COOLING WATER CHEMICALS ..217
VIII.1 Benchmark assessment concept for cooling water chemicals...217a VIII.1.1 Introduction...217a VIII.1.1.1Background ...217a VIII.1.1.2Relevant legislative background...218
VIII.1.1.3The water framework directive (WFD) ...218
VIII.1.2 Benchmarking : introduction of the concept ...219
VIII.1.2.1The PNEC 220 VIII.1.2.2The PEC 221 VIII.1.3 Basic cooling towers material balances ...222
VIII.1.3.1Cooling towers basic equations ...222
VIII.1.3.2Water balance...222
VIII.1.3.3Material balance ...222
VIII.1.3.4Concentration ...223
VIII.1.3.5Discussion 223 VIII.1.4 Calculation of PEC and benchmarking ...224
VIII.1.5 Computation methods ...226
VIII.1.5.1Single Substances ...226
VIII.1.5.2Complex multi-substances treatments ...226
VIII.1.6 Appendix I: extract from technical guidance document...228
VIII.2 Concept of a local assessment method for cooling water treatment chemicals, with a particular emphasis on biocides...231
VIII.2.1 Introduction...231
VIII.2.2 Key elements...232
VIII.2.3 Example of proposed local assessment method ...235
ANNEX IXEXAMPLE OF A MODEL FOR ESTIMATING EMISSIONS OF BIOCIDES IN THE BLOWDOWN...239
ANNEX X INVESTMENT COSTS AND OPERATIONAL COSTS OF EQUIPMENT AND ELEMENTS OF COOLING SYSTEMS FOR NON-POWER PLANT APPLICATIONS ....241
ANNEX XI BEISPIELE VON TECHNIKEN, DIE INNERHALB DES PRIMÄREN BVT-ANSATZES FÜR INDUSTRIELLE KÜHLSYSTEME ZU BERÜCKSICHTIGEN SIND ...247
XI.1 Einleitung...247
XI.2 Kühlwasser durch die Wiederverwendung von Wasser einsparen ...247
XI.2.1 Wiederverwendung von (Ab-) Wasser als Zusatzwasser für Kühltürme ...248
XI.2.2 Nullableitungssystem ...249
XI.2.3 Sprühbecken...250
XI.2.4 Lagerung zur Abkühlung ...251
XI.3 Verminderung der Emissionen durch optimierte Kühlwasseraufbereitung ...253
XI.3.1 Seitenstrom-Biofiltrierung in einem offenen rezirkulierenden Kühlwassersystem...253
XI.3.2 Physikalische Methoden...256
XI.3.3 Optimierung der Anwendung von Bioziden ...258
XI.3.3.1 Überwachung...258
XI.3.3.1.1 Überwachung der Makro-Verschmutzung ...258
XI.3.3.1.2 Markierte Biozide zur Bestimmung der Biozid- und mikrobiologischen Aktivität...258
XI.3.3.2 Bioziddosierung...259
XI.3.3.2.1 Verschiedene Betriebsbedingungen für die Aufbereitung, um die optimale jährliche Gesamtanwendung von Oxidationsmitteln in Durchlaufsystemen gegen Makro- und Mikroverschmutzung zu erzielen. ...259
XI.3.3.2.2 Alternierende Impulschlorung in Durchlaufsystemen ...261
XI.3.4 Alternative Kühlwasserbehandlungsverfahren...264
XI.3.4.1 Ozon ...264
XI.3.4.2 UV-Behandlung...266
XI.3.4.4 Chlordioxid ... 267
XI.3.4.5 Wasserreinigung durch Ionen zur Behandlung von Kühlturmwasser... 270
XI.3.4.6 Halogenierte Biozide im Kühlturmwasser stabilisieren... 270
XI.3.4.7 Filmbildende Mittel gegen Verschmutzung, Korrosion und Verkrustung... 271
XI.3.4.8 Stabile organische Korrosionsinhibitoren in offenen Nasskühltürmen... 274
XI.3.5 Behandlung von abgeleitetem Kühlwasser... 275
XI.4 Variable Frequenz-Steuerungen zur Verminderung des Energieverbrauchs... 276
ANNEX XIISPECIAL APPLICATION: POWER INDUSTRY ... 277
Synthesis ... 277
XII.1 Introduction... 277
XII.2 Power plant cooling systems - principles and reminders ... 278
XII.3 Possible environmental impacts of cooling systems ... 279
XII.3.1 Heat discharges to the atmosphere ... 279
XII.3.2 Heating of receiving aquatic-environments... 281
XII.3.3 Suction of organisms into water intakes ... 282
XII.3.4 Alteration of the receiving environment by chemical discharges... 283
XII.3.5 Other possible harmful effects resulting from the choice of some cooling systems... 286
XII.4 Prior study of the sites: indispensable tool for the evaluation of their receiving capacity, impact control and prevention of harmful effects ... 287
XII.4.1 Analysis of the situation ... 287
XII.4.2 Mathematical modellings, simulations on models and tests on pilot loops, first indispensable tools... 287
XII.5 Design of components and choice of materials... 288
XII.5.1 Wet cooling ... 288
XII.5.2 Hybrid cooling... 289
XII.5.3 Dry cooling... 290
XII.5.3.1 Forced draught air-cooled condenser ... 290
XII.5.3.2 Natural draught air-cooled condenser ... 290
XII.5.3.3 Closed recirculating dry cooling towers ... 291
XII.5.4 Cooling towers with discharge of cleaned flue gas ... 291
XII.6 Cost comparison between the various types of cooling towers... 292
XII.7 Choice of the treatment of circulating water alternative methods - monitoring ... 295
XII.7.1 Anti-scale treatment... 295
XII.7.2 Anti-fouling treatments (biocides)... 296
XII.7.3 Monitoring... 296
XII.8 Design of the cooling system ... 297
XII.8.1 Design and energy recovery ... 297
XII.8.2 Design and noise reduction measures... 297
XII.8.3 Implementation of physical methods... 297
XII.8.4 Modelling and pilot tests ... 298
XII.8.5 Choice of the cooling system... 298
XII.9 Conclusions... 298
XII.10 Literature... 300
XII.11 Illustrations... 306
List of tables
Table I.1: Fouling factors for shell and tube heat exchangers, indicative values [Van der Schaaf, 1995]155
Table I.2: Specific heat capacities of air and water ...157
Table I.3: Heat transfer coefficients and estimated surface areas A (m2) per MW and at 20K mean temperature difference for different industrial applications...158
Table I.4: Effects of the cooling principle on the capacity, approach and cooling surface of a cooling system ...159
Table II.1: Energy consumption in kWe, electricity consumption / MWth, cooling with clean heat exchangers...163
Table II.2: Mean attainable lowest cooling water inlet temperatures for the various cooling systems during the months of July and August in the Netherlands. ...163
Table II.3: Conservation ratios for once-through and recirculating cooling system...177
Table II.4: Energy conservation with potential colder cooling water source...177
Tabelle IV.1: Geschwindigkeit des Kühlwassers und Materialart...185
Tabelle IV.2 Für Pumpen in Brackwasser angewendete Materialien ...186
Tabelle IV.3: Für Gehäuse- und Rohr-Wärmetauscher in Brackwasser angewendete Materialien...187
Table V.1: Survey of fouling and clogging organisms, and degree of fouling in marine, brackish and fresh water. In the last column mitigation is presented...195
Table V.2: Estimated consumption levels of some commonly used oxidising biocides in a few European Member States ...198
Table V.3: Estimated consumption levels in some of European Member States of some commonly used non-oxidising biocides in kg/yr ...200
Table VII.1: Score for a number of R-phrases to calculate the total score for process substances...210
Table VII.2: Requirements of VCI safety concept for cooling technology ...211
Table VII.3: Description of R-phrases used to calculate VCI-score for cooling systems selection ...214
Table VIII.1: Calculation of PEC and Benchmarking ...225
Table VIII.2: Assessment factors to derive a PNEC...229
Table VIII.3: Predicted concentrations of DBNPA in different surface waters for this example...237
Table VIII.4: Ecological data of DBNPA...237
Table VIII.5: Consequences of closing the discharge ...238
Table X.1: Cost elements for water and air cooling systems...243
Table X.2: Cost indications for water and air cooling systems for industrial applications with the exception of power plants (1993-1995) ...244
Tabelle XI.1: Investitions- und Energiekosten pro MWth für Sprühbecken und Kühlturm ...251
Tabelle XI.2: Physikalische Techniken zur Minderung der Biozidanwendung...257
Tabelle XI.3: Wirkung der Anwendung eines optimierten Dosierungssystems auf die Anzahl der durch Muscheln verursachten Leckagen...262
Tabelle XI.4: Typische Dosierung von Chlordioxid für Durchlauf- und rezirkulierende Systeme in Europa ...268
Tabelle XI.5: Wirkung von Chlordioxid, angewendet im Durchlaufsystem gegen Larvenablagerung ....269
Table XII.1: Example of simplified balance of a thermal cycle for conventional new design ...278
Table XII.2: Relationship between the installed capacity and cooling parameters ...278
Table XII.3: Comparison of different types of recirculating cooling systems with a lifetime of 25 years and an actualisation ratio of 8% (study on EDF units of 1300 MWe) ...293
Table XII.4: Comparison of wet cooling towers and aircooled condenser with a life-time of 20 years and an actualisation ratio of 8% for a combined cycle unit 290 MWth ...293
Table XII.5: Relationship between the concentration factor, the withdrawn water flowrate and the energy discharged into the receiving waterway (individual example) ...295
List of figures
Figure II.1: Illustration of areas of potential energy saving by reduction of the temperature gradient
through a fouling layer as well as by using colder cooling water influent ... 162
Figure II.2: Graphic representation of pollution factors responsible for extra temperature gradient over the pipe wall ... 164
Figure II.3: Schematic representation of driving force over the length of a heat exchanger... 166
Figure II.4: Number of cooling water pumps and change of cooling water low due to fouling... 167
Figure II.5: Change of temperature gradient of product gas (moles) in a counter flow heat exchanger due to fouling ... 168
Figure II.6: Representation of increase of process pressure to compensate temperature increase due to fouling ... 169
Figure II.7: Efficiency power generation for pumps, fans and compressors... 170
Figure III.1: Major components of shell & tube heat exchanger... 179
Figure III.2: Heat exchanger nomenclature (Standards of the tubular Exchanger Manufacturers Association)... 181
Figure V.1: Tower and solids balances for an evaporative cooling system using a cooling tower ... 203
Figure V.2: Reduction of the make-up flow by concentration in an evaporative cooling system... 203
Figure VIII.1: Cooling tower material balance ... 222
Figure VIII.2: Combined approach for the assessment of cooling water biocides for existing installations ... 234
Figure VIII.3: Schematic representation of a recirculating cooling system with the data for the example of a local selection method of cooling systems chemicals... 236
Abbildung XI.1: Optimierte Hypochlorid-Dosierung (alternierende Impulschlorung) unter Berücksichtigung der Verschmutzung und der Charakteristika des Kühlsystems ... 263
Figure XII.1: Once-through system ... 306
Figure XII.2: Wet cooling tower... 306
Figure XII.3: Once - through cooling with cooling tower... 307
Figure XII.4: Recirculating cooling ... 307
Figure XII.5: Mechanical draught cooling tower (pressure fans) ... 308
Figure XII.6: Mechanical draught cooling tower (suction fans, cell construction) ... 308
Figure XII.7: Mechanical draught cooling tower (pressure fans, cell construction) ... 309
Figure XII.8: Hybrid cooling tower ... 309
Figure XII.9: Forced draught air-cooled condenser ... 310
Figure XII.10: Natural draught air-cooled condenser ... 310
Figure XII.11: Closed recirculating indirect dry cooling tower ... 311
Figure XII.12: Cooling tower with discharge of cleaned flue gas... 311
Figure XII.13: Cooling system with fixed concentration factor... 312
Figure XII.14: Cooling system with sliding concentration factor ... 312
Figure XII.15: Decision-making logic diagram for the choice of the cooling system ... 313