Reference Manual for Steam and Compressed Air Systems Professional Level Elective Module of Singapore Certified Energy Manager (SCEM) Programme Acknowledgements The reference manual Steam and Compressed Air Systems for the Professional Level elective module of the Singapore Certified Energy Manager Programme was developed for the National Environment Agency. The material was prepared by LJ Energy Pte Ltd. We wish to thank the following organisations for providing various diagrams, photographs and reference data for this manual: Bry-Air Cleaver Brooks Ingersoll Rand Spirax Sarco © Copyright is jointly owned by National Environment Agency and LJ Energy Pte Ltd. No part of this publication may be reproduced or distributed in any form or by any means without the prior written permission of the copyright owners. June 2019 For National Environment Agency Singapore By LJ Energy Pte Ltd Singapore SCEM Reference Manual for Steam & Compressed Air Systems Table of Contents 1.0 STEAM PROPERTIES ........................................................................................ 1 1.1 Introduction ................................................................................................................. 1 1.2 Saturation temperature .............................................................................................. 2 1.3 Sensible and latent heat .............................................................................................. 5 1.4 Steam quality ............................................................................................................... 7 1.5 Superheated steam ..................................................................................................... 8 1.6 Steam pressure vs volume........................................................................................... 8 1.7 Enthalpy ..................................................................................................................... 11 1.8 Steam pressure vs enthalpy of evaporation .............................................................. 13 1.9 Entropy ...................................................................................................................... 14 1.10 Condensate and flash steam ................................................................................... 14 1.11 Use of steam tables ................................................................................................. 15 2.0 BOILERS........................................................................................................... 18 2.1 Introduction to boilers............................................................................................... 19 2.2 Main components of a boiler .................................................................................... 23 2.3 Boiler operation ......................................................................................................... 27 2.4 Boiler efficiency ......................................................................................................... 28 3.0 APPLICATIONS OF STEAM ............................................................................. 39 3.1 Steam distribution systems ....................................................................................... 40 3.2 Common applications of steam ................................................................................. 47 4.0 OPTIMISING STEAM SYSTEMS ...................................................................... 57 4.1 Improving combustion efficiency .............................................................................. 57 4.2 Reducing steam pressure .......................................................................................... 59 4.3 Optimising operation of auxiliary equipment ........................................................... 62 4.4 Standby losses ........................................................................................................... 65 4.5 Minimising conduction and radiation losses ............................................................. 66 4.6 Heat recovery from flue gas ...................................................................................... 67 4.7 Flash steam recovery ................................................................................................. 69 4.8 Automatic blowdown control .................................................................................... 70 4.9 Heat recovery from blowdown ................................................................................. 73 4.10 Condensate recovery ............................................................................................... 74 4.11 Faulty steam traps ................................................................................................... 76 4.12 Rectifying steam leaks ............................................................................................. 77 i SCEM Reference Manual for Steam & Compressed Air Systems 4.13 Feedwater tank........................................................................................................ 78 4.14 Fouling and scaling in boilers .................................................................................. 78 4.15 Fuel switching .......................................................................................................... 79 4.16 Using heat pumps .................................................................................................... 80 5.0 ENERGY AUDIT OF STEAM SYSTEMS........................................................... 83 5.1 Boiler overall efficiency ............................................................................................. 83 5.2 Boiler combustion efficiency ..................................................................................... 86 5.3 Condensate recovery ................................................................................................. 87 5.4 Blowdown rate .......................................................................................................... 87 5.5 Steam leaks ................................................................................................................ 88 5.6 Convective and radiative losses ................................................................................ 88 5.7 Case study of a boiler energy audit ........................................................................... 88 6.0 COMPRESSED AIR SYSTEMS ........................................................................ 92 6.1 Typical compressed air system components ............................................................. 94 6.2 Free Air Delivery ........................................................................................................ 95 6.3 Standard Conditions .................................................................................................. 96 6.4 Utilisation Factor ....................................................................................................... 99 6.5 Duty cycle ................................................................................................................ 100 6.6 Types of Compressors ............................................................................................. 100 7.0 AUXILIARY EQUIPMENT IN COMPRESSED AIR SYSTEMS ........................ 111 7.1 Dryers ...................................................................................................................... 111 7.2 Receiver tanks ......................................................................................................... 118 7.3 Filters ....................................................................................................................... 119 7.4 Aftercoolers ............................................................................................................. 120 7.5 Distribution systems ................................................................................................ 122 8.0 BASIC THEORY OF COMPRESSION ............................................................ 125 8.1 Compression process ............................................................................................... 125 8.2 Specific power ......................................................................................................... 129 8.3 Isothermal efficiency ............................................................................................... 130 8.4 Volumetric efficiency ............................................................................................... 131 9.0 COMPRESSOR CONTROLS .......................................................................... 133 9.1 On / Off control ....................................................................................................... 134 9.2 Load / unload ........................................................................................................... 135 9.3 Inlet modulation ...................................................................................................... 137 9.4 Variable displacement ............................................................................................. 139 ii SCEM Reference Manual for Steam & Compressed Air Systems 9.5 Variable speed control ............................................................................................ 140 10.0 ENERGY SAVING MEASURES FOR COMPRESSED AIR SYSTEMS ......... 143