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Reference Document on Best Available Techniques for Large

20,7

Combustion Plants

618

stron

6059

JRC-IPTS Instituto de Prospectiva Tecnológica (IPTS)

2006

rok

EXECUTIVE SUMMARYI

PREFACEXI

SCOPE AND ORGANISATION OF THE DOCUMENT.XXXV

1 GENERAL INFORMATION. 1

1.1 Industry overview. 1

1.2 Economic situation. 7

1.3 Key environmental issues. 10

1.3.1 Efficiency 11

1.3.2 Emissions to air 13

1.3.2.1 Sulphur oxides . 13

1.3.2.2 Nitrogen oxides (NOX). 13

1.3.2.3 Dust and particulate matter 15

1.3.2.4 Heavy metals 16

1.3.2.5 Carbon monoxide. 18

1.3.2.6 Greenhouse gases (carbon dioxide and others) 18

1.3.2.7 Hydrochloric acid. 21

1.3.2.8 Hydrogen fluoride 21

1.3.2.9 Ammonia (NH3). 21

1.3.2.10 Volatile organic compounds (VOC) 22

1.3.2.11 Persistent organic compounds (POPs), polycyclic aromatic hydrocarbons (PAHs), dioxins

and furans 22

1.3.3 Emissions to water . 22

1.3.4 Combustion residues and by-products . 24

1.3.5 Noise emissions . 26

1.3.6 Emission of radioactive substances 27

2 COMMON TECHNIQUES FOR ENERGY GENERATION. 29

2.1 Principles of combustion 29

2.2 Common technical combustion processes 30

2.2.1 General fuel heat conversion 30

2.2.2 Pulverised solid fuel firing. 30

2.2.3 Fluidised bed combustion furnace . 31

2.2.4 Grate firing. 31

2.2.5 Oil and gas firing . 31

2.2.6 Gasification/Liquifaction . 31

2.3 Direct conversion . 32

2.3.1 General 32

2.3.2 Combustion engines. 32

2.3.3 Gas turbine . 33

2.4 Common technical steam processes . 33

2.4.1 General 33

2.4.2 Vacuum condensing power plant . 33

2.4.3 Co-generation/combined heat and power. 34

2.5 Combined cycle 35

2.5.1 General 35

2.5.2 Supplementary firing of combined cycle gas turbines, and repowering of existing power plants.

2.6 Typical elements of a steam cycle 36

2.6.1 The boiler. 38

2.6.2 Steam turbine . 40

2.6.3 Condenser 40

2.6.4 Cooling system. 40

2.6.5 Specific costs of different power plant concepts 40

2.7 Efficiency 41

2.7.1 Carnot efficiency 42

2.7.2 Thermal efficiency . 42

2.7.3 Unit efficiency . 43

2.7.4 Unit efficiency for steam withdrawal. 43

2.7.5 Exergy concept and exergy efficiency44

2.7.6 Influence of climate conditions on efficiency.46

2.7.7 Relationship between efficiency and environmental issues48

2.7.8 Losses of efficiency in combustion plants48

2.7.9 Generic technical measures to improve LCP efficiency.49

3 COMMON PROCESSES AND TECHNIQUES TO REDUCE EMISSIONS FROM LARGE

COMBUSTION PLANTS .51

3.1 Some primary measures to reduce emissions .52

3.1.1 Fuel switch .52

3.1.2 Combustion modifications52

3.2 Techniques to reduce particulate emissions54

3.2.1 Electrostatic precipitators (ESPs) .55

3.2.2 Wet electrostatic precipitators 57

3.2.3 Fabric filters (baghouses) .57

3.2.4 Centrifugal precipitation (cyclones) .60

3.2.5 Wet scrubber.61

3.2.6 General performance of particulate matter control devices 64

3.3 Techniques to reduce sulphur oxide emissions.65

3.3.1 Primary measures to reduce sulphur oxide emissions 65

3.3.1.1 Use of a low sulphur fuel or fuel with basic ash compounds for internal desulphurisation .65

3.3.1.2 Use of adsorbents in fluidised bed combustion systems.65

3.3.2 Secondary measures to reduce sulphur oxide emissions 66

3.3.3 Wet scrubbers .67

3.3.3.1 Wet lime/limestone scrubbers.68

3.3.3.2 Seawater scrubber.75

3.3.3.3 Magnesium wet scrubber77

3.3.3.4 Ammonia wet scrubber.77

3.3.4 Spray dry scrubbers 78

3.3.5 Sorbent injection.81

3.3.5.1 Furnace sorbent injection81

3.3.5.2 Duct sorbent injection (dry FGD).83

3.3.5.3 Hybrid sorbent injection .86

3.3.5.4 Circulating fluid bed (CFB) dry scrubber.86

3.3.6 Regenerable processes87

3.3.6.1 Sodium sulphite bisulphite process 87

3.3.6.2 Magnesium oxide process 88

3.3.7 General performance of flue-gas desulphurisation (FGD) techniques .89

3.4 Techniques to reduce nitrogen oxide emissions .94

3.4.1 Primary measures to reduce NOx emissions .95

3.4.1.1 Low excess air 95

3.4.1.2 Air staging 96

3.4.1.3 Flue-gas recirculation .97

3.4.1.4 Reduced air preheat 97

3.4.1.5 Fuel staging (reburning) .98

3.4.1.6 Low NOx burner .100

3.4.1.7 General performance of primary measures for reducing NOX emissions .104

3.4.2 Secondary measures to reduce NOX emissions.106

3.4.2.1 Selective catalytic reduction (SCR)106

3.4.2.2 Selective non-catalytic reduction (SNCR)113

3.4.2.3 Safety aspects of ammonia storage.115

3.4.2.4 General performance of secondary measures for reducing NOX emissions .116

3.5 Combined techniques to reduce sulphur oxide and nitrogen oxide emissions117

3.5.1 Solid adsorption/regeneration.117

3.5.1.1 Activated carbon process117

3.5.1.2 The NOXSO process 118

3.5.1.3 Other solid adsorption/regeneration processes .118

3.5.2 Gas/solid catalytic processes 119

3.5.2.1 WSA-SNOX process 119

3.5.2.2 DESONOX process 120

3.5.2.3 The SNRB process .120

3.5.2.4 Emerging gas/solid catalytic processes.121

3.5.3 Electron beam irradiation. 121

3.5.4 Alkali injection. 121

3.5.5 Wet scrubber with additives to achieve NOX removal . 121

3.5.6 General performance of combined techniques for reducing SO2 and NOX 122

3.6 Techniques to reduce metal (heavy metal) emissions 123

3.6.1 Control of mercury (Hg) emissions 124

3.6.1.1 Primary measures to reduce the Hg content of solid fuel. 124

3.6.1.2 Flue-gas treatment technologies to reduce mercury emissions 124

3.6.2 Reduction of metal emissions in particulate control systems. 125

3.6.3 Reduction of metal emissions in FGD systems 125

3.6.4 Reduction of metal emissions in NOX control systems 126

3.6.5 Reduction of metal emissions by systems designed for metal removal . 126

3.7 Techniques to reduce emissions of CO and unburned hydrocarbons. 127

3.8 Techniques to reduce halogen emissions . 127

3.8.1 Reduction of halogen emissions in particulate control systems . 128

3.8.2 Reduction of halogen emissions in FGD systems 128

3.8.3 Reduction of halogen emissions in NOX control systems 128

3.9 Reduction of greenhouse gas emissions from large combustion plants . 129

3.9.1 Reduction of carbon dioxide emissions by increasing the thermal efficiency . 129

3.9.2 Removal of carbon dioxide from flue-gases 131

3.10 Techniques to control releases to water . 132

3.10.1 Waste water from water treatment plants. 133

3.10.2 Waste water from cooling circuit systems . 133

3.10.3 Waste water from other origins of steam generation processes . 133

3.10.4 Waste water from flue-gas cleaning systems . 134

3.10.5 Sanitary waste water 135

3.10.6 Waste water treatment techniques 136