ENGINEERING

CHEMISTRY-2

FUELCNG

LPG

COMPRESSED NATURAL GAS

LIQUEFIED PETROLEUM GAS

COMPRESSED NATURAL GASDEFINITION

PROPERTIES

USES

ADVANTAGES

APPLICATIONS

COMPRESSED NATURAL GAS When the natural gas is compressed, it

is called Compressed Natural Gas (CNG). The primary component present in CNG

is methane. It is mainly derived from natural gas.

The natural gas can either be stored in a tank of a vehicle as compressed natural gas (CNG) at 3,000 or 3,600 psi or as liquified natural gas (LNG) at typically 20-150 psi.

The average composition of CNG is as follows

Constituents Percentage (%)

Methane 88.5

Ethane 5.5

Propane 3.7

Butane 1.8

Pentane 0.5

CNGCNG is made by compressing natural gas

(which is mainly composed of methane [CH4]), to less than 1% of the volume it occupies at standard atmospheric pressure

. It is stored and distributed in hard containers at a pressure of 200–248 bar (2900–3600 psi), usually in cylindrical or spherical shapes

Properties1. CNG is the cheapest, cleanest and least

environmentally impacting alternative fuel.

2. Vehicles powered by CNG produce less carbonmonoxide and hydrocarbon (HC)

emission.3. It is less expensive than petrol and

diesel.4. The ignition temperature of CNG is

about 550°C.5. CNG requires more air for ignition

Uses

CNG is used to run an automobile

vehicle just like LPG.

Advantages of CNG over LPG1.CNG produces less pollutants than LPG.2.CNG is cheaper and cleaner than LPG.3.The octane rating of CNG is high, hence

the thermal efficiency is more.4.It does not evolve sulphur and nitrogen

gases.5.It mixes very easily with air than the other

gaseous fuels.6.Noise level is much less than diesel7.CNG vehicle limit 40% less of nitrogen oxide,

90% less of hydrocarbons, 25% less of CO2

Comparison of emission levels between CNG-driven vehicles and petrol driven vehicles

Pollutants

Emission levels

Petrol driven vehicle

CNG driven vehicle

CO (gm/km) 0.92 0.05

HC (gm/km) 0.36 0.24

APPLICATION OF CNG(CNG) is a fossil fuel substitute for gasoline

(petrol), diesel, or propane/LPG.

CNG may also be mixed with biogas, produced from landfills or wastewater, which doesn't increase the concentration of carbon in the atmosphere.

Cars and locomotives.

The difference between CNG and LPGCompressed natural gas (CNG)

Liquefied petroleum gas (LPG)

LIQUEFIED PETROLEUM GAS (LPG)DEFINITION

USES

ADVANTAGES

DISADVANTAGES

APPLICATIONS

LIQUEFIED PETROLEUM GAS (LPG)It is obtained as a by-product during

fractional distillation of crude petroleum oil or by cracking of heavy oil. It consists of propane and butane. It can be readily liquefied under pressure, so it can be economically stored and transported in cylinders.

The average composition of LPG is as follows

Its calorific value is about 25,000 kcal/m3

constituents percentage

N-butane 38.5

Iso butane 37

propane 24.5

LPGVarieties of LPG bought and sold

include mixes that are primarily propane (C3H8), primarily butane (C4H10) and, most commonly, mixes including both propane and butane and isobutane depending on the season — in winter more propane, in summer more butane[. Propylene and butylenes are usually also present in small concentration. A powerful odorant, ethanethiol, is added so that leaks can be detected easily

Uses

1. It is used as a domestic and industrial fuel

2. It is also used as a motor fuel.

Advantages of LPG over gaseous fuels 1.LPG consists of hydrocarbons, so it burns

cleanly without leaving any residue.2.The LPG (hydrocarbons) has higher

calorific value than the other gaseous fuels containing H2 or CO. The calorific value is 7 times higher than

coal gas and 3 times higher than natural gas.

3.LPG is characterized by high thermal efficiency and heating rate.

4. It is easy to manipulate.

5. Comparatively it is less of health

hazard, even in case of leakage.

6. Needs little care for maintenance.

7. It is free from CO, so it is less

hazardous

Disadvantages of LPG over other gaseous fuels 1. Due to its faint odour, leakage cannot be

easily

detected

2. Its octane value is low.

3. Handling must be done under high pressure.

4.LPG is suitable only for the engines working

under high compression ratio.

Application of LPGIt is increasingly used as an aerosol

propellant and a refrigerant, replacing chlorofluorocarbons in an effort to reduce damage to the ozone layer.

When specifically used as a vehicle fuel it is often referred to as autogas.

Other industrial application includes its use in portable blow lamps, soldering, welding, annealing hardening, brazing, steel cutting etc

TECHNIQUE

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