Boilers and furances How to Save Energy and Money

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Boilers and furances How to Save Energy and Money

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Table of Contents

1. INTRODUCTION……………………………………………………………………………………………………………………………………………………………………..1
2. COMBUSTION…………………………………………………………………………………………………………………………………………………………………………..1
2.1 Combustion air…………………………………………………………………………………………………………………………………………………………………..1
2.1.1 Excess Air……………………………………………………………………………………………………………………………………………………………….4
2.1.2 Glue Gas Analysis………………………………………………………………………………………………………………………………………………..4
2.1.3 Determination of Excess Air …………………………………………………………………………………………………………………………..5
2.2 Heat losses …………………………………………………………………………………………………………………………………………………………………………..7
2.2.1 Heat loss due to incomplete combustion………………………………………………………………………………………………….8
3. HEAT TRANSFER…………………………………………………………………………………………………………………………………………………………………….10
3.1 Conduction………………………………………………………………………………………………………………………………………………………………………..10
3.2 Convection…………………………………………………………………………………………………………………………………………………………………………11
3.3 Radiation……………………………………………………………………………………………………………………………………………………………………………..12
4.THE FUELS……………………………………………………………………………………………………………………………………………….13
4.1 Pipeline gas…………………………………………………………………………………………………………………………………………………………………………13
4.2 Liquid Petroleum Gas ……………………………………………………………………………………………………………………………………………………14
4.3 Fuel Oil………………………………………………………………………………………………………………………………………………………………………………..14
4.4 Coal …………………………………………………………………………………………………………………………………………………………………………………15
4.5 Choice of Fuel ………………………………………………………………………………………………………………………………………………………………….16
5. COMBUSTION EQUIPMENT: OIL AND GAS BURNERS……………………………………………………………………18
5.1 Gas Burners ………………………………………………………………………………………………………………………………………………………………………18
5.2 Oil Burners………………………………………………………………………………………………………………………………………………………………………..18
5.2.1 Pressure Jet …………………………………………………………………………………………………………………………………………………………18
5.2.2 Air or Steam Blast Atomiser …………………………………………………………………………………………………19
5.2.3 Rotary Cup …………………………………………………………………………………………………………………………………………………………19
5.2.4 Low Excess Air Burners …………………………………………………………………………………………………………………………………19
5.3 Burner Controls………………………………………………………………………………………………………………………………………………………………19
6. COMBUSTION EQUIPMENT: SOLID FUEL COMBUSTION ……………………………………………………………..21
6.1 Stokers…………………………………………………………………………………………………………………………………………………………………………………21
6.2 Chain Grate Stoker………………………………………………………………………………………………………………………………………………………..21
6.3 Sprinkler Stoker……………………………………………………………………………………………………………………………………………………………….22
6.4 Fluidised Bed Combustion…………………………………………………………………………………………………………………………………………..22
7. ENERGY SAVING EQUIPMENT ……………………………………………………………………………………………………………………………………..23
7.1 Flue gas heat exchangers …………………………………………………………………………………………………………………………………………….23
7.1.1 Economiser (Feedwater heater)………………………………………………………………………………………………………………….26
7.1.2 Recuperator (Air heater) ………………………………………………………………………………………………………………………………26
7.2 Accumulators ……………………………………………………………………………………………………………………………………………………………………26
7.3 Insulation …………………………………………………………………………………………………………………………………………………………………………….26
7.4 O2 Analysers ……………………………………………………………………………………………………………………………………………………………………..27
7.5 Variable speed fan drives …………………………………………………………………………………………………………………………………………….28
7.6 Flue gas dampers …………………………………………………………………………………………………………………………………………………………….28
7.7 Waste heat boilers …………………………………………………………………………………………………………………………………………………………28
8. POLLUTION …………………………………………………………………………………………………………………………………………………………………………….29
8.1 Environmental Equipment …………………………………………………………………………………………………………………………………………..30
8.1.1 Ash Handling Equipment ………………………………………………………………………………………………………………………………30
8.1.2 Air Pollution Control Equipment ………………………………………………………………………………………………………………..30
9. BOILERS ………………………………………………………………………………………………………………………………………………………………………………..31
9.1 Types of boilers………………………………………………………………………………………………………………………………………………………………..31
9.1.1 Water Tube Boilers…………………………………………………………………………………………………………………………………………..32
9.1.2 Multi-Tubular Shell Boilers …………………………………………………………………………………………………………………………….34
9.1.3 Reverse Flame or Thimble Boilers………………………………………………………………………………………………………………36
9.1.4 Steam generators …………………………………………………………………………………………………………………………………………….37
9.1.5 Sectional Boilers ………………………………………………………………………………………………………………………………………………..38
9.1.6 Condensing Boilers…………………………………………………………………………………………………………………………………………..39
9.1.7 Modular Boilers ………………………………………………………………………………………………………………………………………………..40
9.1.8 Composite Boilers …………………………………………………………………………………………………………………………………………..41
9.2 Boiler system selection ………………………………………………………………………………………………………………………………………………..42
10. ENERGY AND COST SAVING FOR BOILERS ………………………………………………………………………………….43
10.1 Potential Losses …………………………………………………………………………………………………………………………………………………………43
10.2 Boiler Energy Balance …………………………………………………………………………………………………………………………………………….43
10.3 Minimizing Boiler Losses ……………………………………………………………………………………………………………………………………….44
10.3.1 Maintenance saving opportunities ………………………………………………………………………………………………………………44
10.3.2 Blowdown Heat Loss ……………………………………………………………………………………………………………………………………..45
10.3.3 Heat Transfer ……………………………………………………………………………………………………………………………………………………..46
10.3.4 Excess Air Reduction……………………………………………………………………………………………………………………………………….48
• • • • • • • • • • • • • •
10.3.5 Flue gas heat recovery ……………………………………………………………………………………………………………………………………49
10.3.6 Combustion air pre-heat ………………………………………………………………………………………………………………………………53
10.3.7 Load Scheduling ………………………………………………………………………………………………………………………………………………..54
10.3.8 On-Line Cleaning …………………………………………………………………………………………………………………………………………….56
10.3.9 Flue Shut-Off Dampers ………………………………………………………………………………………………………………………………….56
10.3.10 Variable speed fan drives ………………………………………………………………………………………………………………………………56
10.3.11 Integrated control …………………………………………………………………………………………………………………………………………….57
10.4 What to do first – a quick checklist ………………………………………………………………………………………………………………..58
10.4.1 Check list …………………………………………………………………………………………………………………………………………………………….58
11.TYPES OF FURNACES ……………………………………………………………………………………………………………………………………………………….59
11.1 Batch Furnaces …………………………………………………………………………………………………………………………………………………………..59
11.2 Continuous Furnaces ………………………………………………………………………………………………………………………………………………59
11.3 Direct Fired Furnaces …………………………………………………………………………………………………………………………………………….60
11.4 Indirect Heated Furnaces ……………………………………………………………………………………………………………………………………..61
12. ENERGY AND COST SAVINGS FOR FURNACES ………………………………………………………………………………………………62
12.1 Potential Losses …………………………………………………………………………………………………………………………………………………………62
12.1.1 Furnace Energy Balance………………………………………………………………………………………………………………………………….62
12.2 Minimizing Furnace Losses ……………………………………………………………………………………………………………………………………63
12.2.1 Flue gas heat loss………………………………………………………………………………………………………………………………………………63
12.2.2 Heat Loss to incomplete combustion……………………………………………………………………………………………………….66
12.2.3 Radiation Heat Loss…………………………………………………………………………………………………………………………………………66
12.2.4 Furnace pressure control ………………………………………………………………………………………………………………………………67
12.2.5 Furnace efficiencies and Monitoring and targeting ………………………………………………………………………………68
12.3 What to do first – a quick checklist ………………………………………………………………………………………………………………..69
APPENDIX ………………………………………………………………………………………………………………………………………………………………………………..70
Conversion Tables …………………………………………………………………………………………………………………………………………………………………………70
Boiler Efficiency Test ……………………………………………………………………………………………………………………………………………………………………..71
Furnace Efficiency Test ………………………………………………………………………………………………………………………………………………………………….83