Task 4 - final Preparatory Study on Eco-design of CH Boilers Task 4 Report (FINAL) Technical Analysis (incl. System Model) René Kemna Martijn van Elburg William Li Rob van Holsteijn Delft, 30 September 2007 VHK Van Holsteijn en Kemna BV, Elektronicaweg 14, NL-2628 XG Delft, Netherlands Report prepared for: European Commission, DG TREN, Unit D3, Rue de la Loi 200, 1100 Brussels, Belgium Technical officer: Matthew Kestner DISCLAIMER & IMPORTANT NOTE The authors accept no liability for any material or immaterial direct or indirect damage resulting from the use of this report or its content. This report contains the results of research by the authors and any opinions in this report are to be seen as strictly theirs. The report is not to be perceived as the opinion of the European Commission, nor of any of the expertsor stakeholders consulted. Eco-design Boilers, Task 4, Final | 30 September 2007 | VHK for European Commission II CONTENTS page 1 INTRODUCTION .............................................................................. 1 1.1 Scope .....................................................................................................................................1 1.2 Approach.............................................................................................................................. 2 1.3 Report structure................................................................................................................... 3 2 BASIC ENERGY AND MASS BALANCE ..................................................5 2.1 Introduction......................................................................................................................... 5 2.2 Global chemical reaction ..................................................................................................... 6 2.3 Mass balance........................................................................................................................ 6 2.3.1 Stoichiometric volume balance .............................................................................. 6 2.3.2 Air factor/ lambda .................................................................................................. 6 2.3.3 Humidity of combustion air ................................................................................... 7 2.3.4 Influence of emissions ............................................................................................ 7 2.3.5 Converting volume into mass balance.................................................................... 9 2.4 Energy balance combustion............................................................................................... 10 2.4.1 Introduction.......................................................................................................... 10 2.4.2 Combustion heat Qrad + Qconv ................................................................................. 11 2.4.3 Latent condensation heat Qlatent.............................................................................13 2.4.4 Heat loss in excess combustion air Qxsair ...............................................................15 2.4.5 Fuel loss Qfuel-loss .....................................................................................................15 2.5 Energy balance burner........................................................................................................17 2.6 Heat balance primary heat exchanger ............................................................................... 22 2.6.1 Introduction.......................................................................................................... 22 2.6.2 Flue gas losses in on-mode ................................................................................... 24 2.6.3 Losses through the generator envelope in on-mode ............................................ 26 2.6.4 Standing losses in off-mode.................................................................................. 27 2.6.5 Start-stop losses.....................................................................................................31 2.6.6 Primary heat exchanger: Flow diagram ............................................................... 33 2.7 Heat balance secondary and tertiary heat exchanger........................................................ 34 2.7.1 Secondary heat exchanger .................................................................................... 34 2.7.2 Tertiary heat exchanger ........................................................................................ 35 2.8 Heat balance with storage facilities ................................................................................... 36 2.9 Auxiliary energy ................................................................................................................. 37 2.10 Total energy balance .......................................................................................................... 38 3 EMISSIONS ................................................................................. 40 3.1 Introduction....................................................................................................................... 40 3.2 Environmental impact ........................................................................................................41 3.3 Emissions grouped by origin ............................................................................................. 43 3.4 Low non-CO2 Carbon Emission......................................................................................... 44 3.4.1 Formation ............................................................................................................. 44 3.5 Low NOx technology........................................................................................................... 45 3.5.1 Introduction.......................................................................................................... 45 3.5.2 Formation of NOx.................................................................................................. 46 3.6 Principles of Primary Control of NOx Emissions............................................................... 47 3.6.1 Modification of Fuel/Air Delivery-Burner System............................................... 48 3.6.2 Modification of Gas Burner ...................................................................................51 3.6.3 Primary NOx Control Technology Status.............................................................. 54 3.6.4 Secondary Control of NOx Emission..................................................................... 56 3.7 Low emissions vs boiler performance/efficiency ?............................................................ 56 3.8 References.......................................................................................................................... 58 Eco-design Boilers, Task 4, Final | 30 September 2007 | VHK for European Commission III 4 BURNERS ....................................................................................59 4.1 Introduction....................................................................................................................... 59 4.2 Trends ................................................................................................................................ 59 4.3 Types .................................................................................................................................. 60 4.3.1 Surface burners..................................................................................................... 60 4.3.2 Jet burners............................................................................................................ 64 5 HEAT EXCHANGERS..................................................................... 68 5.1 Introduction....................................................................................................................... 68 5.2 Typology............................................................................................................................. 70 5.3 HE – material..................................................................................................................... 73 5.4 HE – shape and design ...................................................................................................... 74 5.4.1 Heat exchangers based on tubes (finned and un-finned) .................................... 74 5.4.2 Heat exchangers based on plates...........................................................................77 5.4.3 Heat exchangers based on integrated castings (aluminium, cast-iron)............... 78 5.4.4 Other heat exchangers types.................................................................................80 6 BOILER CONTROLS .......................................................................81 6.1 Introduction boiler control &components..........................................................................81 6.2 Power input control ........................................................................................................... 83 6.2.1 Pneumatic ratio-control........................................................................................ 83 6.2.2 Integrated mixing & control valve ........................................................................ 84 6.2.3 Turndown ratio oil boilers...................................................................................