Gas Measurement in Coal Power Plants

For energy production, coal pulverizers or mills are used to grind coal into a fine black powder so that the furnace can more easily burn it. Heated air feeds the coal pulverizer and acts as a carrier and dryer for the coal moving to the burner. An exhaust fan pulls the coal dust from the pulverizer and blows it through pipes into the furnace, where it ignites to heat the boiler water. Secondary Air is used maintain the furnace flame and Tertiary Air surrounds the boiler wall...

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Coal Plant Gas Metering Applications

Heated Air
Primary Air is heated with exhausted flue gas through the heat exchanger and pumped into the pulverizer to heat and transport the coal particles.

Gas Characteristics:
Hot, High Flow Rate, High Pressure
Primary Air
Cold Primary Air is mixed with heated air to warm and transport the coal particles from the pulverizer to the boiler.

Gas Characteristics:
High Flow, High Volume
Fuel Air
After the pulverizer coal dust is suspended in the hot, fast moving process. The highly abrasive, flammable and gritty particles will foul most types of gas flow meters. Kurz Meters are immune to this harsh treatment and measure safely and accurately without needing cleaning.

Gas Characteristics:
Hot, Particulates, Abrasive, High Flow, High Volume
Fuel Air
Airborne coal particles are pumped to the boiler as a fuel source. Careful control of the fuel/air ratio allows precise control of the burn.

Gas Characteristics:
Hot, Particulates, Abrasive, High Flow, High Volume
Primary Air to Boiler
Primary air is sent to the boiler to be mixed with fuel and burned. Careful control of the fuel/air ratio allows precise control of the burn.
Secondary Air to Boiler
Additional air is pumped to the boiler above the fire ball (over fire air) to ensure a complete fuel burn and lower emissions.

Gas Characteristics:
High Flow Rate
Flue Gas
Exhaust gases exiting the combustion chamber are sent back to the bottom of the furnace for NOx reduction (Flue Gas Recirculation) or filtered and sent to the stack.

Gas Characteristics:
Hot, Particulates, Abrasive
Exhaust Gas
Excess exhaust gases are sent to the stack to be released. Stack emissions are the metric used to measure a plant's pollution. Continous and precise emissions monitoring is crucial for regulatory compliance.

Gas Characteristics:
Hot, Erratic Flow, High Flow rate, High Volume, Condensing

Coal Plant Gas Metering Instruments

Primary Air

Primary Air in coal plants is used to heat, dry and transport the pulverized coal particles to the combustion chamber. Cool air is heated with recirculated exhaust gases and piped into the coal mill to dry and transport the coal. Primary air may be pre-heated electrically and used fire the boiler. Primary air and heated fuel air is pumped into the bottom of the furnace for combustion and is carefully monitored to control the burn rate. Additional channels of primary air are sent into the furnace at higher levels for staged combustion. This “over fire air”, which produces additional burning above the fireball, helps to elongate the fireball and burn any remaining coal particles.

Combustion Gas

Superheated flue gases exiting the coal boiler are recirculated back to the bottom of the boiler to be re-burned, sent to the coal mill to preheat the coal fuel, channeled to cogeneration units for power generation and finally filtered and sent to the stack. As much heat is recovered and recirculated as possible, excess heat may be dissipated in cooling towers, but a great deal of heat is left to be discharged from the stack. This gas contains carbon dioxide and water vapor, as well as other substances such as nitrogen oxides (NOx), sulfur oxides (SOx), mercury, traces of other metals, and fly ash. Condensation within the stack causes this material to rain down.

Stack Gas

Burning coal produces carbon dioxide and nitrogen oxide, as well as other noxious gases. Despite recirculating and filtering there is still C02 and NOx in the flow stream when it’s sent to the stack. The hot gas is also laden with ash and coal particles. Condensate from oxygen combustion, scrubbers and temperature differential is also present, and mixes with the fine particles to form sludge that collects in droplets. This super-heated and particle laden air billows up the stack and cools, causing condensation to fall back down.