Mitigating Fly Ash Emissions in Electric Power Plants
The Process of Fly Ash Emissions in Electric Power Plants
5 million kg/ day of coal are burned in an electric power plant. The coal has an ash content of 12% by mass. 40% of the ash falls out the bottom of the furnace. The rest of the ash (the fly ash) is carried out the bottom of the furnace with the hot gases into an electrostatic precipitator (ESP). The ESP is 99.5% efficient in removing the ash that comes into it.
Calculation of Mass Emissions Rate of Fly Ash into the Atmosphere
Final answer: The mass emissions rate of fly ash into the atmosphere from this plant is 1884 kg/day.
Explanation: To calculate the mass emissions rate of fly ash into the atmosphere from this plant, we need to consider the amount of fly ash that is not captured by the electrostatic precipitator (ESP) and is released into the atmosphere.
Given that 40% of the ash falls out the bottom of the furnace, the remaining 60% is carried out of the furnace with the hot gases into the ESP. The ESP is 99.5% efficient in removing the ash that comes into it, meaning 99.5% of the fly ash that enters the ESP is captured and removed, while 0.5% is not captured and is released into the atmosphere.
Steps to Calculate the Mass Emissions Rate
1. Calculate the mass of fly ash carried into the ESP: 60% of the ash content of the coal.
2. Calculate the mass of fly ash not captured by the ESP: 0.5% of the mass of fly ash carried into the ESP.
3. Add the mass of fly ash not captured by the ESP to the mass of fly ash that falls out the bottom of the furnace.
By performing these calculations, we can determine the mass emissions rate of fly ash into the atmosphere from this plant.
The power plant produces 600,000 kg of ash daily, 240,000 kg of which falls to the furnace bottom, leaving 360,000 kg as fly ash. The electrostatic precipitator removes 99.5% of this, or 358,200 kg. The remaining 1,800 kg/day is emitted into the atmosphere as fly ash. Firstly, if we have 5 million kg of coal being burnt, and the ash content is 12% by mass, that means that 0.12 * 5,000,000 kg = 600,000 kg of ash is produced every day. Of this ash, 40% falls to the bottom of the furnace, which equals 0.40 * 600,000 kg = 240,000 kg. This leaves 60% of the ash to become fly ash and enter the electrostatic precipitator (ESP), which equals 0.60 * 600,000 kg = 360,000 kg. The ESP is 99.5% efficient in removing ash, so that means it removes 0.995 * 360,000 kg = 358,200 kg of ash. The amount of ash that escapes into the atmosphere is therefore 360,000 kg - 358,200 kg = 1,800 kg/day. So, the mass emissions rate of fly ash into the atmosphere from this plant is 1,800 kg/day.