We know that, for gas cutting operation generally we use combination of oxygen and LPG or Oxygen and acetylene.But now a days for some industry LPG is banned for safety point of view.
Following table gives the difference between Oxy-acetyle and Oxy-LPG gas cutting
COMPARISON BETWEEN ACETYLENE AND LPG FUELS FOR GAS CUTTING OPERATION | ||
SL No. | Acetylene | LPG (Propane) |
1 | Highest flame temperature up to 3100 Deg C | Flame temperature up to 2800 Deg C |
2 | Flame speed up to 7.5 m/sec | Flame speed up to 3.3 m/sec |
3 | Most of the heat released is in inner cone | Most of the heat released is in outer cone |
4 | Higher flame GCV of inner cone (4500 kcal/M3) | Lower flame GCV of inner cone (2500 kcal/M3) as compared to acetylene |
5 | Stoichiometric air fuel ratio1.2:1 (Requires 2.5 to 3 Oxygen cylinders for burning one Acetylene cylinder) | Stoichiometric air fuel ratio 4.3:1 (Requires 7 to 8 Oxygen cylinders for burning one LPG cylinder) |
6 | Can be used in gas welding, as acetylene when burning with air creates reducing zone that cleans the steel surface | Cannot be used in gas welding as it does not create reducing zone |
7 | Acetylene has Specific gravity 0.9 kg/m3, so if it leaks it will raise in air without harming much | Propane has Specific gravity 1.6 kg/m3,which is heavier than air.So if it leaks it will concentrate in deck level or any other closed/corner area |
8 | Acetylene requires less air for complete combustion | Propane requires more air for complete combustion, so there may be chances of formation of carbon monoxide (CO) in case of incomplete combustion. This incomplete combustion may result into poisoning of working area, as CO is poisonous gas |
9 | Can be used for cutting & welding applications in industry | Used only for domestic applications |
Calculate the number of Oxygen cylinders required to consume 1 no.of industrial LPG cylinder for gas cutting operation
Commercial LPG (C3H8) has 19 kg weight that is 19 kg of propane
Combustion equation of propane
C3H8 + 5O2 = 3CO2 + 4 H2O
44 + 160 = 132 + 72 (Molecular weight of C = 12, O = 16, H = 1)
Divide equation by 44
1 + 3.63 = 3 +1.63
From above result it is clear that 3.63 kg of Oxygen is required to burn 1 kg of Propane to achieve 100% combustion.
So for burning 19 kg of commercial LPG, need 19 X 3.63 = 68.97 Kg of oxygen
Volume of oxygen cylinder in cylinder = 6.9 M3 compressed at 140-150 kg/cm2
Convert 6.9 to kg by dividing oxygen density, we get weight of O2 in cylinder = 9.1 kg
So total O2 cylinders required = 68.97 / 9.1 =7.58 Nos for consuming 1 LPG cylinder
Calculate the number of Oxygen cylinders required to consume 1 no.of dilute acetylene cylinder for gas cutting operation
DA (C2H2) cylinder has 8 m3 of acetylene
Convert volume to kg by multiplying the density of the gas
8 X 0.899 = 7.192 kg
Combustion equation of propane
2C2H2 + 5O2 = 4CO2 + 2H2O
52 + 160 = 176 + 36 (Molecular weight of C = 12, O = 16, H = 1)
Divide equation by 52
1 + 3.07 = 3.38 +0.69
So for burning 7.192 kg of DA, need 7.192 X 3.07 = 22.07 Kg of oxygen
So total O2 cylinders required = 22.07 / 9.1 =2.42 Nos
Read Powerplant maintenance calculations
Note:
DA (Dilute Acetylene): OD 265 mm X Height 1 meter (Appx) and thickness 4.0 mm.Volume of acetylene in cylinder is 8.5 m3
Oxygen cylinder size : OD 235 mm X Height 1.34 meter (Appx) and thickness 4.0 mm.Volume of O2 in cylinder is 6.9 m3
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