Inventory Analysis and Impact Assessment towards Comprehensive ...

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Economic and environmental effects of Induction Melting Furnace analyzed by the LCA method Hidemitsu Oda・ Keiichi Okajima ・Yohji Uchiyama Department of Risk Engineering, Faculty of Systems and Information Engineering, University of Tsukuba 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan [email protected] Keywords: Induction melting furnace, Cupola furnace, LCA method, CO2 emission, Economic analysis ABSTRACT Recycling of scrap metals is getting important to construct the low carbon society as well as the circulation society of materials. The switch from a cupola furnace to an induction melting furnace is expected to reduce CO2 emission in the manufacturing process of cast iron. Using the LCA process method combined with an input-output analysis, the economic / environmental characteristics of an induction-melting furnace is compared to that of a cupola furnace. The result shows that a life cycle CO2 emission of an induction-melting furnace is much lower than that of a cupola furnace. The economy of an induction-melting furnace is affected mainly by coke price and coke ratio of raw materials for a cupola furnace. 1.OBJECTIVE The objective of this study is to clarify quantitatively

relations table, industrial statistics, and environmental load data. The direct and indirect CO2 emission from F j can be obtained by the following equation (1):

the advantage of using induction-melting furnaces, which recycles iron scraps by electric heating, over cupola

Gj



C B F

1

furnaces from the environmental and economical points of

output analysis.

direct CO2 emission from sector i is C'i , CO2 emission of sector i per production (“emission source unit”)is C i = C ' i / X i , each element of the Leontief inverse matrix is Bij , the final demand of sector i is F j and emission G j . . 3. Economical Comparison of Cupola and Induction

2.

Melting Furnace

view. Specifically, the manufacturing process for iron casting is analyzed using the LCA method, a hybrid approach that combines the process method and the input-

Method of Study

2.1 Definition of Scope

We compared the economy of production using cupola

An LCA is conducted as follows: “defining the

and induction melting furnaces based on the information

objective and scope”, “inventory analysis”, “impact

and data collected from two onsite investigations and some

evaluation”, and “interpretation of results”. This study

listening comprehensive surveys. This section describes the

focuses on the analysis of “inventory” process.

results of the comparison.

2.2 Inventory Analysis

3.1 Economical Comparison of Cupola and Induction

The inventory analysis is the most primary evaluation

Melting Furnaces

method in LCA. There are two types of inventory analysis,

Table 1 shows the result of comparing the life cycle

the process analysis and input-output analysis, and they

cost comporting a cupola with an induction-melting furnace

have their own strengths and limitations. This study

for 12 years, provided that the coke rate for cupola is 15%

combines the use of the two methods for analysis.

and coke unit price is 70 yen/kg. Cupola and induction

Process analysis and Input-Output Analysis The Process analysis method is a bottom up approach to sum up the environmental inventory of each process and/ or materials. On the other hand in an input-output analysis, direct and indirect input energy of and environmental roads are obtained by a top-down manner using an inter-industry

2.3

melting furnaces used are of the same scale of production 4,480 tons of hot iron annually.

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Table 1. Comparison life cycle cost

4. Comparative Analysis by Process Analysis of CO2

cupola① induction furnace② ①-② 24,000,000 38,000,000 -14,000,000 78,539,368 71,999,400 6,539,968 942,472,419 863,992,80 0 78,479,619 966,472,419 901,992,800 64,479,619

life cycle cost ① initial cost(yen) ② running cost (yen/year) ③ running cost for 12 years ①+③ life cycle cost (yen/12years)

Emissions 4.1 Facility-derived CO2 Emissions Life Cycle CO2 emissions of a facility be broadly

3.2 Economical Analysis of Cupola and Induction Melting Furnace 3.2.1

categorized into facility-derived and operation-derived emissions. The facility-derived emissions from cupola and

Net Present Value

induction melting furnaces are calculated by the material

The economical values of investment and expenses in the

composition data of the respective furnaces obtained

future are changed in comparison to those currently

through listening comprehensive surveys to the spot.(the

generated. Therefore, the future value needs to be

foundry in the Kawaguch city and the fireplace

discounted to current value using the discount rate. If the

manufacturer in the Suzuka city)

expected life is 12 years, the net present value NPV can be

4.2 Operation-derived CO2 Emission

calculated from the following equation (2):

CO2 is also generated by operation and maintenance process during plant life .Given that process-related

NPV



c ) (1+r) ´

(c

(2)

between cupola furnaces and induction-melting furnaces, it

r: discount rate

was not considered in the comparison.

c:cost 3.2.2

difference with regard to CO2 emissions are insignificant

Breakeven

Costs

for

Cupola

competing

Table2. Amount of operation-derived CO2 emission ※CO2emission source unit electric 0.37kg-CO2/kWh, Electric product source unit induction furnace 570kWh/t

Induction Melting Furnaces

CO2emission source unit coke 3.25kg-CO2-t/t ,Electric product source unit cupola 22kWh/t

Figure 1 shows the breakeven costs of coke price for

※Ministry of the Environment ‘FY2002 Deliberation on the Calculation Method of Greenhouse Gas Emission’ The Federation of Electric Power Companies of Japan ‘Environmental Action Plan for the Electricity Utility Industry’

cupola competing economically with induction melting furnaces. The breakeven costs are effected by coke rate in raw materials of cupola and induction-melting furnaces

cupola coke

electric energone year 12 years quantity consumed CO2 emission rCO2 emission rate

coke ratio %



kWh

12 15 18

were: cupola at coke rate of 12% with coke unit price in 70-

538 672 806

79 yen range, cupola at coke rate of 15% with coke unit

t-CO2 1,784 2,220 2,657

21,402 26,643 31,884

induction furnace

price in 60-69 yen range, and cupola at coke rate of 18%

coke coke ratio %

with coke unit price in 40-49 yen range.

t-CO2 98,551 98,551 98,551

electric energone year 12 years quantity consumed CO2 emission rCO2 emission rate t

-

-

kWh t-CO2 2,553,372

t-CO2 945

11,337

300 coke ratio: 18%

Table 2 shows the amount of CO2 generated from the

(

250 c d o i 200 s f 150 t f e 100 r 50 m e 0 i n 0 l c -50 l e -100 i o o -150 n f

coke ratio: 15%

operation of cupola furnaces and induction melting

coke ratio: 12%

)

furnaces for 1 year and 12 years, respectively, based on

(

different coke rates. Furthermore, we presumed that CO2

)

-200

emission source unit remains unchanged for 12 years. 10

20

30

40

50

60

70

80

90

100

4.3 Comparison of CO2 Emission effected by Cupola Coke Rate Figure 2 compares the total CO2 emissions of cupola

unit price of coke (yen/kg)

furnaces, i.e. the sum of facility-derived and operationderived CO2 emissions, with those of induction-melting

Fig.1. Breakeven cost for cupola competing inductionmelting furnace

furnaces. Cupola furnaces emit more CO2 gas than induction melting furnace in both facility-derived and

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operation-derived emissions.

where Yi is direct and indirect CO2 emission of an iron

When compared under the same scale of plant capacity

casting sector estimated by the input-output analysis , and

with an expected life of 12 years, the induction-melting

Yp’ is CO2 emission obtained from the input-output

furnace has a 47% CO2 reduction comparing with a cupola

analysis corresponding to process analysis items.

furnace at a coke rate of 12%. The amount of CO2

Consequently, the hybrid environmental load Y is

reduction by an induction-melting furnace increases in proportion to a coke rate of 15% and 64.3% in a coke rate

Y = Yp + Y’

(4)

18% respectively. where Yp is CO2 emission obtained through the process 57.8

induction furnace

11,337 96.3

cupola【12%】

21,402

facility-generated

analysis method.

operation-generated

5.1 Direct and indirect CO2 emissions of Cast and

Wrought Products

96.3

cupola【15%】

26,643

Direct and indirect CO2 emission for the final goods

96.3

cupola【18%】

31,884

0

5,000

10,000

15,000

20,000

25,000

30,000

can be calculated from the aforementioned equation

35,000

(1)of

tCO2

the inter-industry analysis, However, cast and wrought products are intermediate goods which are mostly Fig. 2. Amount of CO2 generated by cupola under different coke rates

consumed at the “Automotive components and accessories

5. Hybrid Analysis Method of CO2 Emissions by Input-

division” the “Other general machinery, appliances and

Output Analysis

components division”,etc. Therefore the CO2 emission as

In this section the CO2 Emissions of iron cast is analyzed by an input-output method in order to calculate CO2 emissions generated by industrial activities that are left unevaluated by the process method, Figure 3 shows.

③=①-②'

table in order to estimate the CO2 emissions that reflects the

environmental loads excluding prosess analysis items

actual state as intermediate goods. In this method , if the weighted average basic unit of the cast and wrought products is C

②+③ Hybrid environmental loads

Estimation

of

CO2 emissions intermediate goods are obtained by a

and Wrought sectors from other sectors in the inter-industry

②'=environmental loads obtained from input-output analysis corresponding to process analysis items

Fig.3.

intermediate goods. In this study the direct and indirect

weighted method with division of investment to the Cast

① Estimation of direct and indirect environmental loads ② Direct environmental loads of prosesss analysis items

final goods is estimated higher than that of item

, the CO2 emission of the cast and

wrought product C be evaluated by expression (5).

environmental

Loads

by

Cj



Ci B F

(5)

Estimated by Hybrid method The CO2 emissions excluding the effect of process analysis items can be calculated from the following equation (3):

5.2 Derivation of CO2 Emission from Cupola and Induction-Melting Furnaces The values of Yi obtained by the input-output analysis include the environmental load obtained through the

Y’ = Yi – Yp’

(3)

process analysis method. We need to calculate CO2 emission excluding the effect of process analysis items

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from the equation (3). Cast and wrought products consist of

initial cost (facility cost) accounts for only a small share of

93 items on the inter-industry relations table. The

the total cost. In terms of life cycle CO2

environmental load for 9 items estimated by using the

induction melting furnace proved its superiority vis-à-vis

process analysis method should be excluded for cupola

the copula furnace. No significant difference between the

furnaces, and 11 items for induction-melting furnaces.

two difference types of furnace was observed in facility-

Five items are categorized as cast and wrought products in the inter-industry relations table, out of which 2 items,

emission , the

derived CO2 emissions. The difference is mainly effected by the operation-derived CO2 emissions.

cast-iron pipes and iron castings are produced by both culpa

From the environmental measures of life cycle CO2

and induction-melting furnaces. Estimating the percentage

reductions induction-melting furnaces would be expected to

of these two items that account for 63% of the whole of

be diffused and expanded to the market.

cast and wrought products from the appendix table of the

References

inter-industry relations table, we multiplied Y’ by 0.63.

1)

Complied by Ministry of Internal Affairs and

Furthermore, provided that the production ratio from

Communications (2004) ‘Inter-industry Relations

cupola and induction-melting furnace is 6:4, we multiplied

Table for 2000’, National Federation of Statistical

the relevant value for copula by 0.6 and the relevant value

Associations (in Japanese)

for induction-melting furnace by 0.4 to distribute and

2)

estimate the respective environmental loads.

Society’, The Society for the Promotion of the

In order to correspond to the production scale (4480t) used in the process analysis method, we multiplied the CO2

Uchiyama Yohji (2003) ‘Energy Engineering and

University of the Air (in Japanese) 3)

Uchiyama Yohji and Keita Hagiwara (2005) ‘Analysis

source unit per production by 4480t. This value was further

of the Environmental Load and Marginal Cost of Co-

multiplied by 12 to calculate the CO2 generation for an

generation System”, Journal of the Japan Institute of

expected life of 12 years. This is the estimated CO2

Energy, pp 84, 760-766.

emission obtained by input-output analysis excluding the

4)

‘Investigative Research on Measures for Raw Material

CO2 generation obtained by the process analysis method.

Issues on Castings’ / Reference: ‘High-frequency

Figure 4 illustrates the CO2 emissions estimated from a

induction furnace’ (in Japanese)

combination of the summation method and input-output analysis for copula and induction-melting furnaces. The

5)

11336

21402

1613 96.3

33593

5,000

Survey

fa cility-genera ted

31884

1613 96.3 0

Demand

Japanese)

indirect influence (12yrs)

26644

1613 96.3

cupola 【18%】

Power

opera tion-genera ted (12yrs)

28353 cupola 【15%】

Electric

224denryoku.pdf (last viewed: October1, 2008) (in

fa cility+opera tion+indirect (12yrs)

23111 cupola 【12%】

of

(Price)’ www.meti.go.jp/kohosys/press/0004823/0/031

13007 1613 57.8

Agency for Natural Resources and Energy ‘FY2003 Summary

values are equivalent to the values for Y in equation (4). induction furna ce

Japan Industrial Policy Research Institute (2007)

6)

Ministry of the Environment ‘FY2002 Deliberation on the Calculation Method of Green house Gas

10,000 15,000 20,000 25,000 30,000 35,000 40,000 tCO2

Fig. 4. CO2 emissions calculated from the Hybrid

Emission’ www.env.go.jp/earth/ondanka/santeiho/kent

method (for 12 years)

o/h1408/index.html (last viewed: October1, 2008) (in

6. Conclusion

Japanese)

There is approximately a 14 million yen difference of

7)

The Federation of Electric Power Companies of Japan

the initial costs between cupola and induction-melting

‘Environmental Action Plan for the Electricity Utility

furnaces under the same scale of production capacity.

Industry’

Nevertheless, as observed in the 12-year expected life,

viewed: October1, 2008)

www.fepc.or.jp/env/report/2007.pdf

(last