Combustion 101

Combustion is the process whereby a fuel is burned in the presence of oxygen to produce energy. The process requires a fuel, air and an ignition source (spark/flame), and results in carbon dioxide, carbon monoxide, sulfur dioxide, oxygen, nitrogen oxide, water vapor, and in the case of oil systems, smoke being released into the atmosphere as a result of the process.

Why Should we Measure Combustion?

There are several reasons why we should measure combustions:

1. When combustion is efficient, we use less fuel, which saves us money. A 1% improvement in combustion efficiency results in a 1% less fuel being used.
2. Some of the emissions resulting from combustion, such as carbon monoxide, sulfur dioxide and nitrogen oxide, are toxic and can be hazardous to human health.
3. Some of the emissions are environmental pollutants that are detrimental to environmental health (sulfur dioxide and nitrogen oxide) or are greenhouse gases that contribute to global warming (carbon dioxide).
4. Monitoring allows us to detect problems early on so we can take preventative maintenance measures to limit downtime.

What is the Objective of Combustion?

The objective of combustion is to produce energy as efficiently as possible. To maximize efficiency we need to minimize losses when fuel is burned. The more efficient the combustion process, the cheaper it will be.

What is Complete Combustion?

Complete combustion is when 100% of the fuel’s energy is extracted during the process. If we wish to save fuel, and thus costs, we need to strive for complete combustion.

Types of Fuel

Many different types of fuel can be used in the combustion process, the most common being: wood, coal, oils, gasoline, diesel, propane, natural gas, LFG and coke oven gas.

The Importance of Airflow

In order for combustion to be safe and complete there needs to be adequate airflow — including combustion air, infiltration air and dilution air.

To achieve complete combustion the combustion chamber is fired up with excess air. This increases the amount of oxygen and nitrogen available to the flame, which in turn increases the likelihood of oxygen finding and reacting with the fuel.

To ensure that the combustion gases are removed from the combustion area at the appropriate rate, it is important to carefully control the pressure of the gases in the stack.

Depending on the design of the boiler (e.g. natural draft, forced draft or balanced draft), the draft pressure can be either negative or positive.

Gas Analyzers

Gas analyzers are the perfect tool for monitoring both combustion and emissions. Gas analyzers can be used for a wide range of applications, including tuning combustion engines and compliance reporting, and come in a variety of options, including hand-held gas analyzer models or stationary devices which can be fitted with different types of sensors to measure different parameters, which can be logged digitally, printed out or transmitted to a computer, tablet or cellphone.

Depending on the model, a gas analyzer can measure a variety of gases, including: oxygen, carbon monoxide, carbon dioxide, hydrogen sulfide, methane, nitrous oxide, nitrous dioxide, oxygen, sulfur dioxide, as well as hydro carbons and volatile organic compounds.

A gas analyzer can calculate excess air, combustion efficiency, nitrous oxide and true nitrous oxide, as well as carbon monoxide and carbon dioxide emissions. Additionally, a gas analyzer can be used to measure ambient temperature as well as stack and delta temperature. It can also be used to measure differential and draft pressure; air velocity and flow; mass flow; and energy (e.g. MJ/kg, BTU).

Types of Sensors available through Diamond Scientific for use in emission and combustion analysis:

1) Electrochemical 2) Non-Dispersive Infrared (NDIR) 3) Low Power Infrared (LPIR) 4) Photoionization detector (PID) 5) Catalytic Bead