The properties of carbon dioxide gas
Do you know that carbon dioxide gas is produced from the breathing of humans and animals , It is produced from the combustion of coal or hydrocarbons , the fermentation of liquids , and It is a colorless , tasteless and odorless gas .
You must know that carbon dioxide gas ( CO2 ) one of the most stable of all molecules as it consists of a single carbon atom covalently bonded to two atoms of oxygen , and this bond is very strong , and it is a gas at standard temperature and pressure .
Carbon dioxide gas
We have to know that carbon dioxide gas can change the pH of water and it dissolves slightly in the water to form a weak acid called carbonic acid , and it is a greenhouse gas as it transmits visible light but it absorbs strongly in the infrared and near-infrared .
You have to know that most carbon dioxide units are slightly acidic by nature , the level of acidity can be modified by dissolving the molecules in the water , it is soluble in ethanol and in acetone , It is easily dissolves in the water , so it is not collected by the displacement of water .
Everybody should know that carbon dioxide gas reacts with alkalis to give carbonates and bicarbonates , it is a linear covalent molecule , it is an acidic oxide , and it reacts with the water to give carbonic acid .
Everybody must know that carbon dioxide gas reacts with magnesium to form magnesium oxide ( white powder ) and carbon or coal ( black substance ) that deposits on the wall of the cylinder .
Everyone have to know that carbon dioxide gas does not burn and does not help in burning , so it is used in extinguishing the fires , and it is heavier than the air , so it is collected by upward displacement of air .
You have to know that carbon dioxide gas is prepared by adding dilute hydrochloric acid to calcium carbonate , it is prepared by upward displacement of air because it is heavier than the air , and it is not collected by displacement of water as it easily dissolves in the water , and it is also prepared by adding lemon juice or vinegar to sodium bicarbonate ( the backing powder ) .
Carbon dioxide gas properties .
You have to know that carbon dioxide gas forms a solid substance at temperatures below -70 degrees Celsius ( -94° Fahrenheit ) , It may also transform into a liquid when it is dissolved in the water under constant pressure , it is very stable , and it is largely unaffected as it interacts with many other materials in the atmosphere .
Everyone should know that when we inhale carbon dioxide gas at concentrations much higher than the usual atmospheric levels , it can produce a sour taste in the mouth and a stinging sensation in the nose and throat , as carbon dioxide gas dissolves in the mucous membranes and saliva , and it forms a weak solution of carbonic acid .
Do you know that carbon dioxide gas molecule is moderately reactive and is non-flammable ? but it will support the combustion of metals such as magnesium , it contains two double bonds and it has a linear shape , It has no electrical dipole , and it is fully oxidized .
The properties of carbon dioxide gas
Prandtl Number - Pr - | |||||
-50 | 1156 | 1.84 | 0.086 | 0.119 | 2.96 |
-40 | 1118 | 1.88 | 0.101 | 0.118 | 2.46 |
-30 | 1077 | 1.97 | 0.112 | 0.117 | 2.22 |
-20 | 1032 | 2.05 | 0.115 | 0.115 | 2.12 |
-10 | 983 | 2.18 | 0.110 | 0.113 | 2.20 |
0 | 927 | 2.47 | 0.105 | 0.108 | 2.38 |
10 | 860 | 3.14 | 0.097 | 0.101 | 2.80 |
20 | 773 | 5.0 | 0.087 | 0.091 | 4.10 |
30 | 598 | 36.4 | 0.070 | 0.080 | 28.7 |
- 1 kg/m3 = 0.0624 lb/ft3
- 1 J/(kg K) = 2.389x10-4 kcal/(kg oC) = 2.389x10-4 Btu/(lbmoF)
- 1 W/(m K) = 0.85984 kcal/(h m oC) = 0.5779 Btu/(ft h oF) = 0.048 Btu/(in h oF)
- 1 m2/s = 104 St = 106 cSt = 10.764 ft2/s= 38750 ft2/h
Carbon dioxide is at a low concentration in the atmosphere and acts as a greenhouse gas. Carbon dioxide is used by plants to produce carbohydrates. The photosynthesis process releases oxygen to the atmosphere.
Carbon dioxide gas is colorless and heavier than air and has a slightly irritating odor.
Freezing point is -78.5 oC where it forms carbon dioxide snow or dry ice.
Solubility of CO2 in Water
To calculate the CO2emission from a fuel the carbon content of the fuel must be multiplied with the ratio of molecular weight CO2(44) to the molecular weight Carbon 12 -> 44 / 12 = 3.7
Carbon Dioxide emission can be calculated as
qCO2 = cf / hf CCO2/Cm (1)
where
qCO2 = specific CO2emission (CO2/kWh)
cf = specific carbon content in the fuel (kgC/kgfuel)
hf = specific energy content (kWh/kgfuel)
Cm = specific mass Carbon (kg/mol Carbon)
CCO2 = specific mass Carbon Dioxide (kg/mol CO2)
Emission of Carbon Dioxide - CO2- when combustion some common fuels are indicated in the table below.
Note! Heat loss - 55-75% - in power generation is not included in the numbers.
Fuel | Specific Carbon Content (kgC/kgfuel) | Specific Energy Content (kWh/kgfuel) | Specific CO2 Emission (kgCO2 /kgfuel) | Specific CO2 Emission (kgCO2/kWh) |
Coal (bituminous/anthracite) | 0.75 | 7.5 | 2.3 | 0.37 |
Gasoline | 0.9 | 12.5 | 3.3 | 0.27 |
Light Oil | 0.7 | 11.7 | 2.6 | 0.26 |
Diesel | 0.86 | 11.8 | 3.2 | 0.24 |
LPG - Liquid Petroleum Gas | 0.82 | 12.3 | 3.0 | 0.24 |
Natural Gas, Methane | 0.75 | 12 | 2.8 | 0.23 |
Crude Oil | 0.26 | |||
Kerosene | 0.26 | |||
Wood 1) | 0.39 | |||
Peat 1) | 0.38 | |||
Lignite | 0.36 | |||
Bio energy | 0 | - | 02) |
1) Commonly viewed as a Bio fuel
2) Bio Energy is produced from biomass derived from any renewable organic plant, including
- dedicated energy crops and trees
- agricultural food and feed crops
- agricultural crop wastes and residues
- wood wastes
- aquatic plants
- animal wastes
- municipal wastes and other waste materials
Emissions of CO2can contribute to climate change. Combustion of bio energy don't add to the total emission of carbon dioxide as long as the burned bio mass don't exceed the renewed production. (Emission of CO2 when combusting wood is in reality approximately 0.18 kg/kWh)
A variety of bio fuels can be made from biomass resources, including
- ethanol
- methanol
- biodiesel
- Fischer-Tropsch diesel
- gaseous fuels like hydrogen or methane
A measure of CO2 indicates the amount of fresh air supply:
- 15 cfm ventilation rate per occupant corresponds to 1000 ppm CO2
- 20 cfm ventilation rate per occupant corresponds to 800 ppm CO2
Normal CO2 Levels
The effects of increased CO2 levels on adults at good health can be summarized:- normal outdoor level: 350 - 450 ppm
- acceptable levels: < 600 ppm
- complaints of stiffness and odors: 600 - 1000 ppm
- ASHRAE and OSHA standards: 1000 ppm
- general drowsiness: 1000 - 2500 ppm
- adverse health effects expected: 2500 - 5000 ppm
- maximum allowed concentration within a 8 hour working period: 5000 ppm
Extreme and Dangerous CO2 Levels
- slightly intoxicating, breathing and pulse rate increase, nausea: 30,000 ppm
- above plus headaches and sight impairment: 50,000 ppm
- unconscious, further exposure death: 100,000 ppm
· The carbon dioxide - CO2 - concentration in a room with people can be used as an indication of the ventilation systems efficiency. It's even possible to modulate the ventilation system capacity to the number of people and their activity by measuring the carbon dioxide concentration in the air.
· The carbon dioxide emission from persons and their activity:
Activity | Respiration per Person (m3/h) | Carbon Dioxide Emission per Person (m3/h) |
Sleep | 0.3 | 0.013 |
Resting or low activity work | 0.5 | 0.02 |
Normal work | 2 - 3 | 0.08 - 0.13 |
Hard work | 7 - 8 | 0.33 - 0.38 |
· Example - Carbon Dioxide Emission in a Cinema
· In a cinema with 100 persons at low to normal activity the emission of carbon dioxide will be in the range of 0.02 to 0.08 m3/h per person.
· The total emission will be in the range of 2 to 8 m3/h.