Viper Gas resources

Combustion

Background information

In order for combustion to take place, there are 3 essential elements:; Fuel, Ignition source and Oxygen.

Correct combustion is required to maintain customer safety. It is therefore essential that you know and understand the following:

The principles of complete combustion.
The principles of incomplete combustion.

Natural gas comprises of the following by volume. Added to natural gas is a smelling agent as natural gas does not have a smell of its own:

Diethyle sulphide.
Ethyl butyl mercaptan.

Natural gas (methane) is non-toxic when un-burnt. But when burnt incorrectly it will produce: CARBON MONOXIDE. CO.

To prevent carbon monoxide been produced we have to ensure the following;The products of combustion can be removed. There is an adequate supply of air and that the correct amount of air enters the appliance.

Always ensure the correct amount of air enters the appliance

The image with the blue flame is being supplied with the full amount of 10 cubic metres of air to burn 1 cubic metre of natural gas, where as the orange flame is only being supplied half that amount and is NOT achieving complete combustion.

Calorific values

Chart: LPG packs more punch: both propane (red) and butane (blue) contain considerably more energy per cubic meter than natural gas (yellow); in other words, they're more calorific. Butane holds more energy than propane because a molecule of butane has three more atoms than a molecule of propane and three more chemical bonds holding it together. More bonds break when you burn butane, so more energy is released during combustion. Figures in megajoules per cubic meter.

Data from Calor Gas UK.

The main reasons for incomplete combustion

1. Lack of oxygen (soft yellow flames)

2. Incorrect burner pressure (over gassed / under gassed)

3. Flame impingement (flame chilling) A good pre-aerated flame should be bright blue with a strong inner and outer cone, and above all will have a roar. If there is any yellow in the flame then it is incorrect.

(Do not mistake yellow for orange, as orange flames are usually dust being burnt.)

Signs of incomplete combustion

Stoichiometric ratio of natural gas and liquid petroleum gas

The term stoichiometric combustion means perfect combustion and is only ever achievable in laboratory conditions. To create perfect complete combustion, one volume of natural gas (mainly methane) must react with 2 volumes of oxygen. In normal living environments, particulates such as hair and dust, and contaminants like oils and vapours are induced into the air intake of an appliance during the combustion process, and affect the quality of the combustion process meaning that the stoichiometric mixture cannot be achieved.

How to convert a gross figure to a net figure kilowatt input and output

The heat input is the measure of the amount of gas that is being used by the gas fire when it is on full. Do not confuse this with heat output which is the heat supplied to the room by the gas fire and is dependent on the efficiency of the appliance.

The heat input will be shown on the data plate in kilowatt (kW). There are two forms of kilowatt, net and gross. Check the data plate older appliances will most likely show kW gross, modern appliance will show it in kW net.

To convert from kW gross to kW net

heat input (net) = heat input (gross) ÷ 1.1

For example a 10kW (gross) appliance will be rated at 9.1kW.

To convert from kW net to kW gross

heat input (gross) = heat input (net) x 1.1

For example a 9.1kW (net) appliance will be rated at 10kW.

Flame pictures-pre and post aerated flames

Carbon monoxide

Signs and symptoms of carbon monoxide poisoning may include:

Dull headache
Weakness
Dizziness
Nausea or vomiting
Shortness of breath
Confusion
Blurred vision
Loss of consciousness

Carbon monoxide poisoning can be especially dangerous for people who are sleeping or intoxicated. People may have irreversible brain damage or even be killed before anyone realises there's a problem.

Google Sites

Report abuse