University of Nicosia     Compressed Natural Gas   Introduction into Oil&Gas

by Vladislav Dimitriadis       December 2013

of energy today.
It is commonly used to heat and cool

homes and businesses
nationwide. In addition, more than 85,000 compressed natural
gas (CNG) vehicles, including one out of every five transit buses, are operating
sucessfully today. CNG’s popularity stems, in part, from its clean-burning properties.
In many cases, CNG vehicles generate fewer exhaust and greenhouse
gas emissions than their gasoline- or diesel-powered counterparts.

Introduction

CNG is made by compressing natural gas (which is mainly

composed of methane, CH4), to less than 1 percent of the volume it occupies at standard atmospheric pressure. It is stored and distributed in hard containers at a pressure of 200–248 bar (2,900–3,600 psi), usually in cylindrical or spherical shapes.
CNG is odorless, colorless, and tasteless. It consists mostly of methane and is drawn from gas wells or in conjunction with crude oil production. CNG vehicles store natural gas in high-pressure fuel cylinders at 3,000 to 3,600 pounds per square inch. An odorant is normally
added to CNG for safety reasons.

spark plugs.
CNG-powered vehicles have lower maintenance costs than other hydrocarbon-fuel-powered

vehicles.
CNG fuel systems are sealed, preventing fuel losses from spills or evaporation.
Increased life of lubricating oils, as CNG does not contaminate and dilute the crankcase oil.
Being a gaseous fuel, CNG mixes easily and evenly in air.
CNG is less likely to ignite on hot surfaces, since it has a high auto-ignition temperature (540 °C), and a narrow range (5–15 percent) of flammability.

Advantages

for fuel storage than conventional gasoline powered vehicles. Since it

is a compressed gas, rather than a liquid like gasoline, CNG takes up more space for each GGE (gasoline gallon equivalent). Therefore, the tanks used to store the CNG usually take up additional space in the trunk of a car or bed of a pickup truck which runs on CNG. This problem is solved in factory-built CNG vehicles that install the tanks under the body of the vehicle, leaving the trunk free (e.g., Fiat Multipla, New Fiat Panda, Volkswagen Touran Ecofuel, Volkswagen Caddy Ecofuel, Chevy Taxi - which sold in countries such as Peru). Another option is installation on roof (typical on buses), requiring, however, solution of structural strength issues.

Drawbacks

gas). While both are stored forms of natural gas, the

key difference is that CNG is gas that is stored (as a gas) at high pressure, while LNG is stored at very low temperature, becoming liquid in the process. Compressed natural gas is sometimes mixed with hydrogen (HCNG) which increases the H/C ratio (heat capacity ratio) of the fuel and gives it a flame speed about eight times higher than CNG.

Comparison with other gaseous fuels

it is available in Canada and several U.S. regional markets.
Buses powered

with CNG are common in the Canada such as the New Flyer Industries C40LF bus shown here.

Koala CNG Bus Trial" at ACTION in Canberra.
A Mercedes-Benz OC500LE (withCustom Coaches bodywork)

running on CNG, operated by Sydney Buses in Sydney, Australia.

of advantages and not so many disadvantages. But it does

not interfere with technology of CNG to develop.
However, CNG cars produce less emissions and greenhouse gases than their gasoline- and diesel-powered “brothers”