METI/ECCJ/AOTS Training Program

Indonesia

Effect of air ratio reduction

The graphs are developed on the assumption that a change in air ratio does not affect the exhaust gas temperature.

Criteria for air ratio (standard values)
(the Law Concerning Rational Use of Energy)

Standard air ratio for boiler

Type	Load factor, %	Solid fuel		Liquid fuel	Gaseous fuel	Blast furnace gas, etc. Byproduct gas
Type	Load factor, %	Fixed bed	Fluidized bed	Liquid fuel	Gaseous fuel	Blast furnace gas, etc. Byproduct gas
Electric utility service	75-100	-	-	1.05-1.2	1.05-1.1	1.2
Other service (Quantity of evaporation, tons/h)
30-	50-100	1.3-1.45	1.2-1.45	1.1-1.25	1.1-1.2	1.2-1.3
10-30	50-100	1.3-1.45	1.2-1.45	1.15-1.3	1.15-1.3
5-10	50-100	-	-	1.2-1.3	1.2-1.3
-5	50-100	-	-	1.2-1.3	1.2-1.3

Summary of note

After periodical inspection / stable operation state / air ratio at the boiler outlet
Additional notes on pulverized coal combustion on fixed beds
Use the fuel of higher mixing ratio in case of mixed fuel combustion.
Exemption:
Small boilers specified by the Labour Safety and Health Law, boilers for which the fuel has been changed after installation, boilers burning an industrial waste with fuel
Boilers burning either black liquor or waste tires, byproduct gas of a heating value of 3,800kj or lower, or burning a poisonous gas for treatment purpose
Boilers for the purpose of using waste heat, using a heating medium, operating unsteadily, or for the purpose of development, research and test manufacturing

Criteria for air ratio (target value)
(the Law Concerning Rational Use of Energy)

Target air ratio for boiler

Type	Load factor, %	Solid fuel		Liquid fuel	Gaseous fuel	Blast furnace gas, etc. Byproduct gas
Type	Load factor, %	Fixed bed	Fluidized bed	Liquid fuel	Gaseous fuel	Blast furnace gas, etc. Byproduct gas
Electric utility service	75-100	-	-	1.05-1.2	1.05-1.1	1.15-1.2
Other service (Quantity of evaporation, tons/h)
30-	50-100	1.2-1.3	1.2-1.25	1.05-1.15	1.05-1.15	1.2-1.3
10-30	50-100	1.2-1.3	1.2-1.25	1.15-1.25	1.15-1.25
5-10	50-100	-	-	1.15-1.3	1.15-1.25
-5	50-100	-	-	1.15-1.3	1.15-1.25

Summary of note

almost the same as those of the table of standard values

Energy conservation by air preheating

Air preheating preheats the combustion air using the heat of the combustion gas.
The preheated combustion air carries heat to the boiler / furnace; therefore, the required fuel is reduced.
Consequently, heat loss attributable to the exhaust gas is reduced.
The effect of air preheater becomes higher as the air ratio is higher.

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