METI / ECCJ / ACE Training Program MTPEC06 (2007.01)

Manufacturing of ceramics and stone/clay products

Ex.3 Waste heat recovery from the tunnel kiln

A. Preheating of Combustion air

1. Existing problems:
	The cooling zone air of the tunnel kiln is used as combustion air, but the highest possible temperature is only 80ºC because the flow-meter currently in use is made of glass.
2. Improvement measures:
	The supply-air flow-meter for the burners in the sintering section is replaced with a heat-resistant flow-meter. This allows the air temperature to be increased form 80ºC to 250ºC, thereby reducing fuel consumption.

3. Preconditions for estimation:
	Fuel: A-fuel oil Fuel consumption: 467kL/y at sintering part (Total 667kL/y in kiln) Air ratio, m: 1.2 Flue gas temperature: 1,300ºC Fuel saving ratio: 23% - 8% = 15% (By figure) Fuel price: k\31.1/kL
4. Estimated energy saving: 467kL/y×0.15 = 70kL/y
5. Effect
	Reduction in crude oil equivalent = 70kL/y×39.1GJ/kL/38.76MJ/L =71kL/y CO² reduction = 70kL/y ×39.1GJ/kL×0.0189tC/GJ×44/12 = 190t/y Cost saving = 70kL/y × k\31.1/kL = k\2,177/y

Ex.3 Waste heat recovery from the tunnel kiln
(Ceramics and stone/clay products)

B. Heat recovery by steam from exhaust gas

1. Existing problems:
	The flue gas (having a temperature of 258ºC) from the tunnel kiln is released into the atmosphere without any heat recovery.
2. Improvement measures:
	The heat of the flue gas (258ºC) from the tunnel kiln is recovered by means of steam having a pressure of 3 kg/cm² (and a saturation temperature of 143ºC). Using this steam as the heat source for the factory’s dryers cuts the dryers’ LPG consumption.

3. Preconditions for estimation:
	Specific gravity of A fuel oil: Theoretical air volume, A0: Theoretical combustion gas volume, G0: Present A fuel oil consumption: Oxygen content in dry flue gas: Supplied water to waste heat boiler: Generated steam: Dryers’ operation: Dryer LPG consumption: LPG price:	0.85kg/L 10.85m²_N/kg 11.5m²_N/kg 111L/h = 667 kL/y(250d/y×24h/d) 15.8% (Estimated air ratio, m = 4.0) 20ºC, enthalpy: 73.7kJ/kg 143ºC, enthalpy: 2,738.1kJ/kg 4,000h/y (16h/d, 250d/y ) 5.3kg/h (= 21.15t/y/4,000h/y),LPG = 50,2MJ/kg ¥137/kg
4. Calculation:
	Amount of flue gas: 111L/h×0.85kg/L×(11.5+10.85×(m-1)) m²_N/kg = 4,156m²_N/h If the flue-gas exhaust heat above is recovered to such an extent that the gas temperature is lowered to 180C; Heat value of the recovered heat: 4,156m²_N/h×1.382kJ/m²_N/K×(258-180)C = 448MJ/h Steam generated by the recovered heat: 448MJ/h/(2,738.1-73.7)kJ/kg = 168kg/h. This steam will be used as the heat source for the factory’s dryers. Heat value of LPG: 5.3kg/h×50.2MJ/kg = 266MJ/h. This can be amply covered by the heat value of the recovered heat, 448MJ/h.
5. Effect
	Reduction in crude oil equivalent = 21.15t/y×50.2GJ/t/38.76GJ/kL = 27.4kL/ CO² reduction = 21.15t/y×50.2GJ/t×0.0163tC/GJ×12/44 = 63.5t/y Cost saving = 21.15t/y×k\137/t = k\2,900/y

Textile Industry

Ex.4 Introduction of Inverter control to Aerator Blower Motor

1. Existing problems:
	The blower of the aerator system is always operated in full load, but the load factor is lowered at the night time. The aeration efficiency is low because of the large air bubbles into the treated water.
2. Improvement measures:
	Exchanging the diffused air pipes to small hole type, and introduction of the inverter control system to the blower motor With the aim of reduction of power consumption, the motor revolution is controlled according to the dissolved oxygen concentration (DO) in the aerating tank.

3. Preconditions for estimation:
	Blower Motor characteristics: Blower motor capacity: Load factor: Operation time: Energy saving ratio by inverter: Electricity price:	45kW×2units 80% 24h/d×365d/y = 8,760h/y 20% (= Ave. revolution 93%) ¥15.4/kWh
4. Estimated energy saving:
	Power Saving: 45kW×2units×0.8×8,760h/y×0.2 = 126,144kWh/y

5. Effect:
	Reduction in crude oil equivalent = 126.1MWh/y×9.76GJ/MWh / 38.76GJ/kL = 32kL/y CO² reduction = 126.1MWh/y×0.555tCO²/MWh = 70t/y Cost saving = 126,144kWh/y×\15.4/kWh = k\1,943/y

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