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CNG stands for Compressed Natural Gas and is one of the most viable alternative vehicular fuel. Natural Gas is available locally in abundance and use of CNG as a vehicular fuel will reduce the dependence on imported oil which in turn will reduce the subsidy burden on the FGN. It is ‘Clean, Affordable & Safe’. It is NIGERIA’s GAS.
The only major difference between a Petrol/Diesel vehicle and a Natural Gas Vehicle (NGV) is the fuel system. Natural gas is compressed to about 240 kg/cm2 (about 240 bar) and is stored onboard the vehicle in cylinders installed in the boot, undercarriage, or on the roof. When natural gas is required by the engine, it leaves the cylinders, passes through a master manual shut-off valve and travels through a high-pressure regulator located in the engine compartment. The natural gas is injected at atmospheric pressure through a specially designed natural gas mixer where it is properly mixed with air. Natural gas then flows into the engine’s combustion chamber and is ignited to create the power required to drive the vehicle.
Petrol vehicles converted to natural gas are subject to a marginal power loss (about 10% to 15%) when running on natural gas; however, vehicles designed specifically to run on natural gas will have no loss of power and may even have greater power and efficiency. Natural gas has a 120 to 130 octane rating, compared with 87 to 96 octane rating of petrol. In case of dual fuel conversion of diesel vehicles, the power is increased by 15% to 20%.
• Cylinder: The cylinder is used to store CNG at a working pressure of 200 bar. It is fitted with a shut-off valve and a safety burst disc.
• High Pressure Steel Tubing: This connects the refuelling valve to the CNG Cylinder and Pressure Regulator.
• Refuelling Valve: The Refuelling Valve is used to refuel the CNG cylinder.
• Pressure Regulator: The Pressure Regulator has a Solenoid Valve to shut-off gas supply to the engine. The CNG stored at a high pressure in the cylinder is reduced to just below atmospheric pressure by this unit for carburetted vehicles and at above atmospheric (positive pressure) pressure for Fuel Injection vehicles.
• Gas-Air Mixer: The Gas-Air Mixer is a unique component, specially designed to suit each engine model; it allows proper mixing of air & gas before it is fed into the engine inlet manifold. For fuel injection vehicles, a sequential gas injection rail with injectors is used in place of Gas-Air mixer.
• Petrol-Solenoid Valve: The Petrol-Solenoid Valve is used to cut off petrol supply to the engine when it runs on CNG.
• Fuel Selector Switch: The Fuel Selector Switch is fitted at the dashboard, enabling the driver to choose either the CNG mode or the Petrol mode of operation. The electronics built into this unit ensures safety by switching off the gas solenoid whenever the engine is switched off. It also serves as a fuel gauge for indicating the quantity of CNG available in the cylinder.
The Petrol/Diesel system is retained during conversion for CNG so that the vehicle will still run on Petrol/Diesel. In case of petrol vehicle a bi-fuel CNG kit is installed and a switch on the dashboard allows one to make instant change-over from CNG to Petrol and vice-a-versa. While in case of diesel vehicle, a dual fuel CNG kit is installed due to which it can run on either both diesel & CNG simultaneously (this helps in achieving a substitution of 50% of diesel) or diesel alone.
1. Lower Operating Cost: On mile to mile basis, CNG is cheaper than Petrol by 46 %. This is based on the prevailing price (as on 01.11.2012) of CNG & Petrol.
2. Lower Maintenance Cost: Due to the absence of any lead or benzene content in CNG, the lead fouling of spark plugs is eliminated. CNG fuel systems are sealed, which prevents any spill or evaporation losses. There is an increase in the life of lubricating oils, as Natural Gas does not contaminate and dilute the crankcase oil.
3. Environment Friendly: Natural gas has less carbon per unit energy available as compared to Petrol & Diesel and hence reduces vehicular exhaust emissions (Carbon Monoxide, Carbon Di-oxide, Unburnt Hydrocarbons etc) significantly. This in turn will help you to live in a clean environment.
4. Flexibility and Ease of Use: The basic engine characteristics of a vehicle are retained while converting it to run on CNG. The vehicle therefore is capable of running either on Petrol or CNG at the flick of a switch mounted on the vehicle dashboard. In case of diesel vehicles, the vehicle runs on either both diesel & CNG simultaneously or diesel alone
5. Social benefits: Reduction in importation of liquid fuel, which in turn reduces subsidy burden on the FGN.
On mile to mile basis, CNG is cheaper than Petrol by 46% and is cheaper than AGO by 60%. This is based on the prevailing price (as on 01.11.2012) of CNG & Petrol/AGO.
CNG is a safer fuel than most conventional liquid fuels, for reasons associated with natural gas’s ignition, dispersion and burning characteristics and its low toxicity.
• With a specific gravity of 0.6, Natural Gas is lighter than air so in case of any leak, it rises up and dissipates into air (Liquid fuels form ground hugging vapour layers and pools in case of leaks which pose significant localised safety hazard).
• Natural Gas self Ignition Temperature is higher, around 700 degree Centigrade, while that of petrol is around 455 degree Centigrade.
• Natural Gas has a narrow and higher flammability range when compared to liquid fuels.
• CNG storage is far safer than liquid fuels, as CNG cylinders are designed and built from special materials and to high safety specifications.
Refuelling is safe as the cylinder is made from a single piece of special steel alloy, with no welded joints, and every cylinder is tested as per international standards before being installed. A ‘burst disc’ ensures safety as in case of an inadvertent high pressure fill, or in case of any other exigencies, the disc ruptures so no excess pressure situation over the specified level is created. Italy, New Zealand, Argentina and the US are countries where CNG has been in use for many decades, and it has been categorized as a safer fuel.
A pressurized gas cylinder is probably the strongest component on the vehicle. Vehicles that got totally destroyed in collisions show the only discernible component being the intact gas cylinder. It is unlikely that cylinders will rupture due to collision impact.
The use of CNG serves to extend life of lubricating oil as Natural Gas will not contaminate or dilute crankcase oil. Fouling of plugs is eliminated and plug life is enhanced as Natural Gas does not contain any lead. CNG enters the engine as gas while liquid fuel comes in as spray or mist which washes down the lubricating oil from the piston ring area to raise the rate of engine depreciation. This reduces maintenance costs and engine life goes up.
Top 5 countries in terms of no. of CNG vehicles are Pakistan (2.5 million), Iran (1.95 million), Argentina (1.9 million), Brazil (1.67 million) and India (1.1 million). Other countries such as Egypt, Mozambique, Tanzania, Spain, France, UAE, Peru, Venezuela, Brazil, Thailand, Malaysia, Singapore, Indonesia, Phillipine, China, Korea, Japan, Bangladesh, Pakistan, India, Australia, UK, Russia, Canada and the US have significant CNG programs. As of now, worldwide, there are over 15 Million vehicles running on CNG and it is expected to reach 35 Million by the year 2020.
A country can have cleaner environment with comprehensive use of CNG. Nigeria, a country which is very dependent on imported oil for its transport sector can use her existing natural gas resources in a CNG program and achieve substantial reduction in fuel imports, saving in valuable foreign exchange and reduction in the subsidy burden.