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Adjust excess oxygen – a measure on energy-saving for boilers

Boilers require a lot of energy for operation. Costs for fuel, therefore, might be very high. To make the most from energy saving, you can refer to the following measure on adjusting excess oxygen. 

The adjustment of excess oxygen is one of those measures that bring about boiler efficiency. Try to apply this correctly, you will find amazing results. 

dieu chinh oxy du
Adjust excess oxygen – a measure on energy-saving for boilers 

The provision of an optimal amount of excess air to the combustion process while operating boilers will help minimize heat loss through flue gas leaving the boilers and optimize the efficiency of the combustion process in the combustion chamber. The collection of measurements during the combustion process will be an effective way to assess how efficient energy of the fuel is transferred into the needed energy. The temperature of flue gas and the excess oxygen after combustion process are the 2 main indicators for calculating combustion efficiency. 

During combustion process, oxygen must be supplied so fuel could be turned into useful energy; otherwise, unburned fuel will be emitted from the combustion chambers. This can imply a threat to safety and environment when boilers are not located in an area suitable for the combustion process. Besides, unburned or partial combusted fuel creates toxic carbon monoxide exhaust. Another issue arised from unburned fuel from insufficient excess oxygen supplied to the combustion chambers is potential cause for black smoke and surface fouling. 

It is important to avoid incomplete fuel combustion. That is why most boilers arrange fans to add excess oxygen to ensure complete combustion of the fuel used. However, the excess air is added to the combustion chamber from the environment temperature, for example: 35oC and together with flue gas emitted from boilers at high temperature, for example: 300oC. The excess air put into boilers is heated by energy of the fuel. In addition, the nitrogen density in the air is much higher than oxygen. Nitrogen is not helpful for the combustion process and uses the energy which causes heat loss. The monitoring to decrease energy loss requires that the excess oxygen must be maintained in a reasonable range. This range depends on the types of fuels and methods of monitoring and controls. 

The following matrix provides some general information on typical controlled limit for boilers. 

giơi han kiem soat oxydu
Reasonable excess oxygen limit control

lam sao de kiem soat oxy du
How to control excess oxygen added to the combustion process 

There are many equipments that can measure and analyse compositions of flue gas, including TESCO 135XL. However, to those boilers that use costly fuels like FO, DO, LPG, the online monitor oxy content system is recommended. 

For example: Boiler 5 tons/hour using DO, consumes 300 liters of DO every hour, at the cost of 16,300 VND/liter; boiler operation: 6000 hours/year. Flue gas temperature: 520 0 F environment temperature 30 0 C, % excess oxygen in flue gas: 11%. Refer to the matrix collum 490 (520-30) and collum 11%, energy loss through lue gas is 25.18%. Using fan, adjust the percentage of excess oxygen to 5%, loss via flue gas is reduced to 18.18%. 
Total cost saving = Fuel cost x ( E1-E2) = 300*6000*16300* ( 25.18-18.18)/100 = 2 billions VND/year. 

Only with this simple method, enterprises can save 2 billion VND each year, which is an impressive figure. So let’s try it and save energy for your enterprises today.