In this chapter, we shall see how the combustion process is controlled to meet the two objectives defined in the previous paragraph. We shall also examine the subsidiary systems that maintain the correct operational conditions in the fuel-handling plant of coal-fired boilers.

Chapter Contents:

• Part 1: Control
• 5.1 The principles of combustion control
• 5.1.1 Cross-limited control
• 5.1.1.1 Using gas analysis to vary the fuel/air ratio
• 5.1.1.2 Combining oxygen measurement with other parameters
• 5.1.1.3 Using carbon-in-ash (CIA) measurements
• 5.1.2 Multiple fuel sources
• 5.2 Working with multiple fuels
• 5.3 The control of mills or pulverisers
• 5.3.1 The 'load line'
• 5.3.2 Mill control strategies
• 5.3.3 Fuel quality factor
• 5.3.4 Mill temperature control
• 5.3.5 Controlling multiple mills and multiple fuels
• 5.3.5.1 The challenge of auto/manual changeover
• 5.4 Air distribution and pressure control
• 5.5 NOx control
• 5.6 Maintaining the furnace draught
• 5.7 Cross-over pressure control
• 5.8 Binary control of the combustion system
• 5.8.1 Burner management systems (BMS) and plant safety
• 5.8.2 Sequence controls
• Part 2: Instrumentation
• 5.9 Furnace instrumentation
• 5.9.1 CCTV systems
• 5.9.2 Acoustic leak detection
• 5.9.3 Flame monitoring and purge air requirements
• 5.9.3.1 Flame monitors
• 5.9.4 The requirements for purge air
• 5.10 Oil (and gas) flow instrumentation
• 5.11 Air flow
• 5.11.1 Venturi
• 5.11.2 Aerofoil
• 5.11.3 Thermal mass flow
• 5.11.4 Capacitance/cross-correlation
• 5.11.5 Averaging Pitot tube system
• 5.12 Flue gas analysis
• 5.12.1 Oxygen and CO analysers
• 5.12.2 NOx measurements
• 5.12.3 Continuous emission monitoring systems
• 5.13 Mill and silo fire detection and penthouse monitoring
• 5.14 CIA measurements
• 5.15 Summary
• References

Inspec keywords: steam power stations; boilers; power generation control; combustion

Other keywords: subsidiary systems; fuel-handling plant; coal-fired boilers; draught control; combustion process control

Subjects: Steam power stations and plants; Control of electric power systems