METI / ECCJ / ACE Training Program MTPEC06 (2007.01)

(1) Industrial Furnaces

9) Heat Recovery Rates for Industrial Furnaces

Waste Heat Recovery Rates, Standard/Target for Furnaces

Exhaust gas temperature (ºC)	Capacity category	Waste heat recovery rates		(Reference for target)
Exhaust gas temperature (ºC)	Capacity category	Standard (%)	Target (%)	Waste gas temperature (ºC)	Preheat air temperature (ºC)
< 500	A & B	25	35	275	190
500 ≤ ~ < 600	A & B	25	35	235	230
600 ≤ ~ < 700	A B C	35 30 25	40 35 30	365 400 435	305 270 230
700 ≤ ~ < 800	A B C	35 30 25	40 35 30	420 460 505	350 310 265
800 ≤ ~ < 900	A B C	40 30 25	45 40 35	435 480 525	440 395 345
900 ≤ ~ <1,000	A B C	45 35 30	55 45 40	385 485 535	595 490 440
1,000 ≤	A B C	45 35 30	55 45 40	- - -	- - -

Notes: A: Rating capacity of from 84GJ/h (≈ 20Gcal/h)
B: Rating capacity of from 21GJ/h (≈ 5Gcal/h) to under 84GJ/h (≈ 20Gcal/h)
C: Rating capacity of from 840MJ/h (≈ 200Mcal/h) to under 21GJ/h (≈ 5Gcal/h)

(2) Boiler and Steam System

1) EE&C Measures on Boiler-Steam system

Boiler
- Measurement of boiler efficiency and SEC
  Boiler efficiency is calculated from the amount of steam generating and fuel consumption. When the amount of direct steam generating cannot be measured, it is judged from the amount of water supply.
- Optimum Air Ratio
- Heat recovery from flue gas and blow-down
- To minimize supply steam pressure
  Minimum pressure to satisfy process temperature
- To reduce heat loss from boiler and parts by heat insulation
  Boiler body, valves, piping, water level gage, etc
Distribution
- Minimize steam leakage
  If there is one 2mm hole on 5kg/cm2 steam piping, the amount of steam leakage will go up to 8kg/h.
- Improve the insulation for piping and fittings
End User
- Suitable pressure
- Drain recovery and maximize condensate return
- Insulation
- Temperature control
- Right steam trapping and air venting

(2) Boiler and Steam System

2) EE&C Technologies on Boiler/Steam System

(2) Boiler and Steam System

3) Standard/Target Air Ratio for Boilers by the Law

Classification			Kinds of fuel
Purpose of use		Load factor (%)	Solid fuel		Liquid fuel	Gas fuel	By-product gas such as blast furnace gas
Purpose of use		Load factor (%)	Fixed bed	Fluidized bed	Liquid fuel	Gas fuel	By-product gas such as blast furnace gas
Electric utility		75~100	- 1.15~1.3 *3	-	1.05~1.2	1.05~1.1	1.2
Electric utility		75~100	- 1.15~1.25 *3	-	1.05~1.1	1.05~1.1	1.15~1.2
Others (Quantity of evaporation (t/h))	30 ≤	50~100	1.3 ~1.45 1.2 ~1.3 *3	1.2 ~1.45	1.1~1.25	1.1 ~1.2	1.2 ~1.3
	30 ≤	50~100	1.2~1.3 1.20~1.25 *3	1.2~1.25	1.05~1.15	1.05~1.15	1.20~1.3
	10≤ ~ <30	50~100	1.3 ~1.45 1.2 ~1.3 *3	1.2 ~1.45	1.15~1.3	1.15~1.3	-
	10≤ ~ <30	50~100	1.2~1.3 1.20~1.25 *3	1.2~1.25	1.15~1.25	1.15~1.25	-
	5≤ ~ <10	50~100	-	-	1.2 ~1.3	1.2 ~1.3	-
	5≤ ~ <10	50~100	-	-	1.15~1.25	1.15~1.25	-
	< 5	50~100	-	-	1.2 ~1.3	1.2 ~1.3	-
	< 5	50~100	-	-	1.15~1.25	1.15~1.25	-

Note *1: The standard values of air ratio mentioned in the table above define those to be obtained in measurements at the boiler outlet when fired at a constant level of load after regular inspection and in a stable states. Note
*2: Air ratio = 21/[(21-(Oxygen content in the exhaust emission in percentage)] Note
*3: In the case of the pulverized coal fired boiler

11/19
Next