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EX1 - Combustion Fumes - Exercises

This document provides calculations to estimate air pollutant emissions from combusting peat in a fluidized bed boiler. It details the steps to calculate particulate matter, sulfur dioxide, nitrogen dioxide, and carbon dioxide emissions based on information provided about the peat composition and quality, boiler power output, combustion conditions, and operational hours. The calculations involve determining the molar amounts and volumes of combustion products and reactants using chemical equations and combustion reactions, then estimating pollutant concentrations and annual emissions based on these values and the boiler operating parameters.

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34 views5 pages

EX1 - Combustion Fumes - Exercises

This document provides calculations to estimate air pollutant emissions from combusting peat in a fluidized bed boiler. It details the steps to calculate particulate matter, sulfur dioxide, nitrogen dioxide, and carbon dioxide emissions based on information provided about the peat composition and quality, boiler power output, combustion conditions, and operational hours. The calculations involve determining the molar amounts and volumes of combustion products and reactants using chemical equations and combustion reactions, then estimating pollutant concentrations and annual emissions based on these values and the boiler operating parameters.

Uploaded by

ducanh
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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LUT

Environmental Technology
BH60A0451 Air Pollution Control
Exercise: Combustion fumes

1. Peat is combusted in a fluidized bed boiler. Calculate particulate matter (mg/Nm3),


sulfur dioxide (mg/Nm3), nitrogen dioxide (mg/MJ) and carbon dioxide (t/a)
emissions. Combustion air factor is 1,1, the boiler power is 200 MW, the boiler
efficiency is 88% and operational period 8400 h/a.

Peat Quality Content in dry


Component
matter (%)
Lower heating 9,2 MJ/kg
value Carbon 50
Water content 50 p-% Hydrogen 5
Ash content in dry 5 p-% Oxygen 38
matter
Nitrogen 2
Volatile content in 70 p-%
dry matter Ash 5
Density 250 kg/m3

Combustion reactions:

C + O2 → CO2
H2 + ½O2 → H2O
S + O2 → SO2
LUT
Environmental Technology
BH60A0451 Air Pollution Control
Exercise: Combustion fumes

1. Emissions from combustion of 1 kg peat.

M, O2- CO2, SO2, H2O, N2,


m, g n,
g/mol tarve, mol mol mol mol
mol
mol
C 12

H2 2

O2 32

N2 28

H2O 18

S - -

ash - -

total

M 44 18 28

Combustion in reality  = 1,1

Oxygen need:

nO 2 ,need    (O2  need ) 

Oxygen and nitrogen amounts in combustion fumes:


LUT
Environmental Technology
BH60A0451 Air Pollution Control
Exercise: Combustion fumes

Volume of combustion fumes (NTP normal air temperature and pressure)

n, mol Vn, m3n/kmol V, m3n

CO2 22,26

SO2 21,89

H2O 22,4

O2 22,39

N2 22,4
dry
combustion
fumes

Particulate matter emissions


We assume that 70 % of ash falls to bottom of the boiler and 30 % of ash drifts to
combustion fumes.

Sulfur dioxide emissions


The fuel does not contain sulfur so sulfur dioxide emissions are:
LUT
Environmental Technology
BH60A0451 Air Pollution Control
Exercise: Combustion fumes

Nitrogen dioxide emissions

- Fuel NOx is dominant formation process in fluidized bed boilers


- Thermal NOx has only a marginal role
It is assumed that approximately 10% of nitrogen in fuel reacts to NOx. There is
typically 95 % NO and 5 % NO2.

NO and NO2 are formed in combustion via the following reactions:

N2 + O2  2 NO (1)

NO + ½ O2  NO2 (2)

m NO n  M  NO

m N2 n  M  N 2

m NO

mN2

m NO 

By using the reaction 2, NO2 amount can be calculated:

m NO2 n  M  NO 2

m NO n  M  NO

mNO2 
LUT
Environmental Technology
BH60A0451 Air Pollution Control
Exercise: Combustion fumes

NO2 emission per 1 MJ fuel energy:

Carbon dioxide emissions:


At first annual fuel consumption is calculated:

 CO2 emissions

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