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Special report on CNG application

Published by
Oilfield Technology,

This report is intended to present basic information about Compressed Natural Gas (CNG) and its application.


What is CNG?

Natural gas is a clean energy with minimal CO2 pollution among all other kinds of fossil fuel. Its burning products don't generate dissolution of ash dust or SOx compounds. It helps to reduce NOx compounds in the atmosphere due to the fuel control nature.

A car operated using this fuel is called a Natural Gas Vehicle (NGV).

CNG chemical characteristics

CNG is composed of Carbon compounds and various kinds of gases such as Methane Ethane, Propane, Butane, Pentane and a small amount of Nitrogen.

The relative quantities of any of the above gases in a given volume of natural gas differ from one site to the other and dependent on their geographic origin. The difference among gases from different geographic areas is demonstrated as follows:

CNG chemical components relation by (mol/100mol):

Countries Methane% Ethane% Propane% Butane% Pentane% Nitrogen%
Canada 99.81 0.07 0.00 0.00 0.00 0.12
Brunei 89.83 5.89 2.92 1.30 0.04 0.02
Abu Dhabi 82.07 15.86 1.86 0.13 0.00 0.05

CNG volatility is high and it evaporates quickly at normal ambient temperature.

Since CNG is lighter than the air, it is easily diffused in the atmosphere.

Comparing CNG to the Propane gas that is heavier than the air and therefore stagnates in low places at ambient temperature, or comparing to the butane gas, the CNG can be considered as a safe compound.

CNG advantages

  • Clean energy (low emission).
  • Low CO2 emission.
  • Low ash dust emission.
  • Low SOx emission.
  • Low NOx emission and comparing to diesel engine.
  • CO2: 20 to 30% less.
  • Ash dust: 100% less.
  • SOx: 100% less.
  • NOx: 60 to 70% less.

Supply stability

The global natural gas quantity is estimated to be about 181 trillion m3, and its reserve-production ratio (total amount of useable natural gas in the earth/annual output) is expected to be 1.5 times more than oil (63 years of gas supply comparing to 41 years of oil supply). Development of a new gas fields is expected as well.

Moreover, since natural gas exists in every corner on the globe widely, unlike oil, which is commonly a Middle East countries product, it excels a supply stability as well.

The following pie chart presents the estimated natural gas quantities around the world.

CNG disadvantages

  • Delivery cost: compressed gas supplying and storage system is required (pipeline, compressor, storage container, LNG storage ship).
  • Compared to oil, energy efficiency is low.

NGV (Natural Gas Vehicle)

NGV is a vehicle powered by a natural gas engine.

There are two kinds of NGVs: one uses CNG (Compressed Natural Gas) while the other uses LNG (liquid natural gas) as a fuel.Generally, since fuel is the Compressed Natural Gas, it is also called a CNG car or CNG truck.

NGV advantages

  • Low emission (Clean emission gas).
  • Easy reconstruction of vehicle engine.
  • The main parts of NGV engine are the same as gasoline/diesel engine. These are presented in the following figure.

Main NGV engine supporting components

Light Duty Vehicles (LDVs) are almost 95% of NGVs on the roads nowadays. Trucks and buses quantity is increasing at a faster rate and is expected to grow in 9% of the total fleet by 2020.

The leading region in terms of annual sales of NGVs, with 1.2 million sales expected in 2013 is Asia Pacific, while China and Pakistan are the largest markets; Thailand and India are the fastest growing with compound annual growth rates of 18% and 12%, respectively, between the years 2013 and 2020.

The combination of availability of inexpensive CNG, vehicle availability, and strong government support contribute to sales growth in these countries.

The following figure presents the expected increase of LDVs, M/HD buses and M/HD trucks fleets from the year 2013 up to 2020.

In general, points of great importance when selecting components for CNG applications are:

  • Selection of material which can meet the specific temperature range of -40 - 120 °C.
  • Selection of material that provides stable durability in the presence of gases like Methane, Ethane, Propane and CO2.
  • Components design for high flow-pressure conditions.

HAM-LET is a manufacturer of special products ECE R110 approved for CNG trucks in Thailand. All HAM-LET products intended for NGV meet the ECE R110 standard. An example of a HAM-LET top product is the high pressure manifold shown below.

Written by Yasu Chiba and edited by Elizabeth Corner

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