Energy and the New Reality, Volume 1: Energy Efficiency and the Demand for Energy Services Chapter 6: Industrial Energy Use L. D. Danny Harvey [email protected].

Energy and the New Reality, Volume 1:

Energy Efficiency and the Demand for Energy Services

Chapter 6: Industrial Energy Use

L. D. Danny [email protected]

This material is intended for use in lectures, presentations and as handouts to students, and is provided in Powerpoint format so as to allow customization for the individual needs of course instructors. Permission of the author and publisher is required for any other usage. Please see www.earthscan.co.uk for contact details.

Publisher: Earthscan, UKHomepage: www.earthscan.co.uk/?tabid=101807

Major Industrial Sectors

- Iron & Steel- Aluminum- Copper- Cement- Glass- Pulp & Paper- Plastics- Petroleum refining- Chemicals (including fertilizers – Chapter 7)

- Food processing (Chapter 7)- General manufacturing

Figure 6.1 Industrial Energy use in 2005 as a percent of total energy use in various regions

0

10

20

30

40

50

60

Pe

rce

nt

Ind

us

tria

l

Africa EuropeNorth

AmericaCentralAmerica

SouthAmerica Asia Oceania

Global Average: 37.5%

Figure 6.2a Industrial energy use in OECD countries in 2005

Iron and Steel16%

Chemical & Petro-

chemical20%

Pulp and Paper 13%

Non-Ferrous metals 6%

Non-specified11%

Non-metallic minerals 8%

Textile and leather 2%

Construction1%

Wood and wood

products 2%

Food and Tobacco 7%

Mining and Quarrying 2%

Transport equipment

2%

Machinery7%

Figure 6.2b Industrial energy use in non-OECD countries

Iron and Steel25%

Chemical & Petrochemical

13%

Non-Ferrous metals

5%

Non-specified25%

Non-metallic minerals

11%

Textile and leather

3%

Construction1%

Wood and wood products

1%

Food and Tobacco 7%

Mining and Quarrying 2% Transport

equipment2%Machinery

4%

Pulp and Paper 2%

Figure 6.3 Global primary energy use for production of the 12 commodities (other than the production of fuels)

using the most energy

0

5

10

15

20

25

30

35

Go

bal

Pri

mar

y E

ner

gy

Use

(E

J/yr

)

Definitions:

• Primary metals: made from virgin ores (raw materials)• Secondary metals: recycled from scrap• Feedstock energy: The energy content of fossil fuels

that become part of the material in a commodity. It is equal to the heating value of the final product.

• Process energy: energy (in the form of heat or electricity) used to power a chemical transformation. It is equal to the total energy inputs to the production process minus the embodied energy of the final products

• Embodied energy: the total amount of energy (process + feedstock) that went into making something

Overview of global production of major commodities of energy interest

CommodityProduction(Mt/year)

Primary Energy Intensity (GJ/t)

Principle Energy Input

Ave C Emission (tC/t)

Cement 2600 4-8 Coal, NG, or Oil 0.3Steel 1320 20-40 Coal 0.7Paper & Paper Products 365 16-42 Biomass 0.0Lime 277 0.4 Electricity 0.03Plastics 260 50-160 Oil 1-3Ammonia 132 36-44 Natural gas 0.7Ethylene 110 20-30 Oil 0.6Non-fibrous glass 95 20-25 Coal, Oil, or NG 0.6Aluminum 38 ~160 Electricity 4.2Copper 16 ~85 Electricity 2.2

Figure 6.4: Trends in production of major commodities (solid lines use the left scale, dashed lines the right scale)

0

50

100

150

200

250

300

0

500

1000

1500

2000

2500

3000

1960 1970 1980 1990 2000 2010

An

nu

al P

rod

uct

ion

(Mt)

An

nu

al P

rod

uct

ion

(Mt)

Year

CementSteelPaperPlasticsAluminumCopper x 10Zinc x 10

Processing of Minerals

• Most minerals of interest occur as oxide minerals in ores (rock bodies with various minerals mixed together, besides the ones of interest)

• The steps in processing minerals are thus – separation of the minerals of interest from the other minerals in the ores

- removal of oxygen (reduction)- purification

Reduction of oxide minerals, calcination of CaCO3 (during production of cement), and processing of

silica and limestone to make glass all release CO2

• Iron: 2Fe2O3 +3C → 4Fe+3CO2

• Alumina (made first from bauxite):

2Al2O3 + 3C → 4Al+3CO2

• Cuprite (produced by roasting Cu-containing minerals):

2CuO+C→2Cu+CO2

• Calcination of limestone to make cement:

CaCO3→CaO+CO2

• Production of glass:

nSiO2 + mCaCO3 + xNa2CO3 + .... → Glass + CO2

In the case of iron, aluminum and copper, the C used for reduction comes from fossil fuel inputs, or from materials (such as C anodes) made from fossil fuels, and so is accounted for in the energy use data combined with the emission factors (kgC/kg fuel) for these energy inputs.

Thus, fossil fuel energy inputs play two roles in producing Fe, Al, or Cu – as a source of C for the reduction reaction and as a source of heat (through combustion) to drive the reaction.

In the case of calcination of limestone or transformation of raw materials into glass, however, the C that is released as CO2 comes from the raw materials themselves and so is not accounted for in the energy use data.

Thus, you will find that national CO2 emission data are given separately for coal, oil, natural gas, and production of cement. This latter category refers to the CO2 that is produced through the chemical reactions involved in the formation of cement, and is in addition to the CO2 released from burning the fossil fuels used at the cement plants.

Chemical emissions from the production of glass are only about 1% of those from cement (due to about 30 times less global production and a 3 times smaller emission factor), and tend to be ignored in compilations of national emissions.

Iron and Steel

Figure 6.5a: World production of primary + secondary raw steel

0

200

400

600

800

1000

1200

1400

1995 1997 1999 2001 2003 2005 2007

Raw

Ste

el P

rod

uct

ion

(Mt/

yr)

Year

OtherUkraineS KoreaRussiaUSJapanChina

Compounded Growth Rates, 2000-2007:China: 19.1%/yrROW: 2.8%/yrOverall: 6.4%/yr

Figure 6.5b: Production of raw steel in 2007

China37%

Japan9%US

7%

Russia5%

Other28%

S Korea 4%

Ukraine 3%

Germany 3%Brazil 2%

Italy 2%

Figure 6.5c End uses of steel in the US in 2003

Service Centers and Distributors

27%

Construction22%

Transportation 15%

Containers3%

Other33%

Figure 6.6 Anthropogenic iron flows in 2000 (Tg Fe/yr)

Source: Wang et al (2007, Environmental Science and Technology 41, 5120–5129)

Traditional Steps in Making Steel:

• Beneficiation of iron ores (removal of impurities)• Agglomeration of fine particles• Reduction of iron ore to make crude iron• Refining of crude iron to make steel (removing

impurities, adding trace elements)• Shaping of steel into final products

Reduction of iron ore

• Commonly done in a blast furnace• C from coke (which is like charcoal, and made from

coal by driving off volatile materials) is used as a reducing agent

• Theoretical minimum energy requirement is 6.8 GJ/t• Practical lower limit is 10 GJ/t, best blast furnaces

use about 12 GJ/y, world average is about 14.4 GJ/t• Coke provides some of the heat energy required (as

well as serving as a reducing agent), with the balance supplied by coal

Refining of crude iron

• 3 options are: Open-hearth furnace, Basic Oxygen Furnace (BOF), Electric air furnace (EAF)

• BOF requires pure oxygen (separated from air)• EAF is used for scrap metal and in the new

direct-reduction process• Energy by EAFs per tonne of steel fell in half

between 1960-1900

Figure 6.7 Refining of reduced iron to produce steel

0

200

400

600

800

1000

1200

1975 1990 2003

Year

Pro

dcu

tio

n (

Mt/

yr)

Other

Electric arc furnace

Basic oxygen furnace

Open Hearth Furnace

Figure 6.8 Energy used by EAFs per tonne of crude steel

High power/long arc operation

Water cooledwalls

Oxygenlancing

Secondarymetallurgy

630 kWh/tcs

Electricity consumption

6.5 kg/tcs Electrode consumption

DC technology

2.2 kg/tcs

350 kWh/tcs

Higher electric powersupply

Scrap preheating

EBT (slag-free)

Pneumaticbath stirringLadle furnace

Bottom tap hole

Water cooled roof/oxy-fuel burner

Foaming slag practice

Computer control

Oxygen andcarbon lancemanipulator

year

1965 1970 1975 1980 1985 1990

10

8

6

4

2

0

Source: de Beer et al (1998a, Annual Review of Energy and the Environment 23, 123–205)

Shaping of Steel, Traditional Method

Produce steel in cubical blocks, small bars, or slabs using a continuous caster, then convert into final products using various hot mills (heating and cooling occurs between steps, with an energy loss each time)

Shaping of Steel, Alternative approaches: Cast the molten steel closer to the desired final shape, using thin-slab casting, thin-strip casting, or powder metallurgy

• Thin-strip casting has the potential to reduce energy use for shaping by 90-95%

• In thin-strip casting, the length of the production line has been reduced from 500-800 m to 60 m – about a factor of ten reduction!

Alternative Approaches for Reducing Iron Ore:

• Blast Furnace with coke through reaction with CO while the ore is still solid (traditional approach)

• Direct reduction of the ore using coal or natural gas to produce a H2-rich gas (or direct use of purchased H2) combined with a DC current

• Smelting reduction of the ore in the liquid state, directly using coal

Figure 6.9a Primary energy use with best current blast-furnace/BOF route for making primary steel

C o a l

Iron o re

1 .9

C o keo ven

O re p re -p ara tio n

2 .6

12 .4

B la s tfu rn ace P ig

iron

F lu x in g ag en tP e lle ts

0 .3

B as ico xyg enfu rn ace

C ru d estee l

S crap (10% )

0 .6

R efin in gcas tin g C as t

s tee l

2 .1

R o llin gS ha pin g

19.9 GJ/t

Q u ality fla tan d lo ngp ro d u c ts

Figure 6.9b Primary energy use with advanced blast-furnace/BOF making primary steel

By comparison, the present world average primary energy requirement for primary steel is

about 36 GJ/t

Coal

Iron ore

1.2

Cokeoven

Ore pre-paration

2.2

11.9

Blastfurnace Pig

iron

Fluxing agentPellets

-1.0Basic

oxygenfurnace

Crudesteel

Scrap (10%)

0.6

Refiningcasting Cast

steel

1.5

RollingShaping

16.9 GJ/t

Quality flatand longproducts

Figure 6.9c Primary energy use with best current direct reduction/EAF steel making

Iron ore1 .4

O re p re -para tio n

N atural gasor C o al

D irectredu ction

13.4

S po ngeiron

3 .5

O xygenFo ss il fue l

C ru des teel

0 .6

R efin ingcas ting C ast

s teel

1 .0

R ollingS hapin g

20.0 GJ/t

Fla tprodu cts/

shapes

Figure 6.9d Primary energy use with advanced direct reduction/EAF steel making and advanced refining,

casting, and shaping

Iron ore1.4

Ore pre-paration

Natural gasor Coal

Directreduction

11.3

Spongeiron

3.5

Electricarc furnace Crude

steel

OxygenFossil fuel

0.75

Refiningcastingshaping

16.9 GJ/t

Flatproducts/shapes

Figure 6.9e Primary energy use with advanced smelting-reduction/BOF steel making and advanced

refining, casting, and shaping

This is a reduction by 63% (~two thirds) compared to the present average primary energy use for primary steel of

36 GJ/t. The savings is due in part to an assumed improvement in the efficiency in generating the electricity

that is supplied to the steel plant from 40% to 60%.

Iron ore

Coal

Smeltingreduction

13.4

Pigiron

-1.0

Basicoxygen furnace

Crudesteel

0.75

RefiningCastingShaping

13.2 GJ/t

Quality flat and long products(Scrap)Oxygen

Figure 6.10a Current mill using scrap steel to make secondary steel

3.4Electric

arcfurnace

Crudesteel

Scrap0.6

Refiningcasting Cast

steel

1.0

RollingShaping

5 GJ/tcs

Bar/shapesFlat products

OxygenFossil fuel

Source: de Beer et al (1998a, Annual Review of Energy and the Environment 23, 123–205)

Figure 6.10b Advanced mill using scrap steel to make secondary steel

This is a reduction by 50% from the present world average of 7 GJ/t for secondary steel. The savings is due in part to an assumed improvement in the efficiency in generating the electricity that is supplied to the steel plant from 40%

to 60%.

0.5

Scrapupgrading

2.3

Electricarc

furnace Crudesteel

0.75

RefiningcastingShaping

3.5 GJ/tcs

Bar/shapesFlat products

Oxygen

Scrap

Fossil fuel

de Beer et al (1998a, Annual Review of Energy and the Environment 23, 123–205)

Source: de Beer et al (1998a, Annual Review of Energy and the Environment 23, 123–205)

Steel Summary: Primary Energy Requirements

• Primary Steel:

- 36 GJ/t world average today, assuming electricity supplied at 40% efficiency

• Secondary Steel:

- 7 GJ/t world average today – a reduction by about a factor of 5 compared to primary steel

Steel Summary (continued):

• Current average with 32% secondary: 26.3 GJ/t• Future average with 90% secondary and current best practice as average: 6.9 GJ/t This is a reduction by a factor of 3.8 • Future average with 90% secondary, best projected energy intensities for primary and secondary steel: 5.9 GJ/t This is a reduction by a factor of 4.5• All of the above plus 60% electricity supply efficiency instead of 40%: 4.5 GJ/t This is a reduction by a factor of 5.8

• Thus, the overall potential reduction in the average primary energy intensity of steel is a factor of 4.5 to 6

Aluminium

Figure 6.11a World production of primary aluminium

0

5

10

15

20

25

30

35

40

1995 1997 1999 2001 2003 2005 2007

Year

Pri

mar

y A

lum

iniu

m P

rod

uct

ion

(kt

/yr)

Other

US

Canada

Russia

China

Figure 6.11b Production of primary aluminium in 2007

China32%

Russia11%

Canada8%

US7%

Australia5%

Other22%

Brazil 4%

India 4%

Norway 3%

S Africa 2%

UAE 2%

Figure 6.11c End uses of aluminium in the US in 2003

Construction16%

Containers & Packaging

23%

Electrical7%

Machinery & Equipment

7%

Transportation36%

Other4%

Consumer Durables

7%

Production of Aluminium

• Mining of bauxite (mostly Al(OH)3 and AlO(OH)) (most of the mining is through strip mining)

• Refining of bauxite into alumina (Al2O3)-grinding, then digestion with caustic soda at high T and P

• Smelting of alumina into aluminium, through electrolysis of alumina that has been dissolved into cryolite (Na3AlF6) at 900oC

-both the cathode and anode are made of C

-the net reaction is 2Al2O3+3C→4Al+3CO2

Figure 6.12 Aluminium Mass Flow in 2005

From this diagram it can be seen that a little over 4 t of dry bauxite are mined for every tonne of primary aluminium that is produced

Bauxite 168.2

A lum ina 61.3

MATERIAL FLO W METAL FLOW

Ingots 63.8Prim ary

A lum in ium used31.6

R em eltedA lum in ium 32 .3

TradedN ew

Scrap 1.3

Fabrica torScrap

17.0

Bauxite Residues 70.8and Water 36.1 M etal Loss es 1.3

o .a .R ecycledA lum in ium 15 .3

OtherA pplications

1.1

TradedN ewScrap 7.9

O ldScrap

7.4

Not Recycled in 2005 3.5

Under Investigation: 3.3

Total Produc tsStored in U seSince 1888560 .7

F in ishedProducts (output)37.6

Fabrica ted and F in ishedProducts ( input)62.5

B uild ing 32% Transport 28%o.a.Autom otive 16%

O ther 11%

Engineeringand Cable 28%

P ackaging 1%

N et A ddition 2005: 22 .2

Source: IAI (www.world-aluminium.org)

Figure 6.13 Secondary energy used in making aluminium metal

Mining0.4%

Refining, Electricity

1.7%

Refining, Fuels23.9%

Smelting, Electricity

56.4%

Materials, Fuels17.6%

Figure 6.14: World average electricity use for the production of aluminium

0

5

10

15

20

25

30

1950 1960 1970 1980 1990 2000 2010

Ele

ctri

city

Use

(M

Wh

/t)

Year

Figure 6.15 Efficiencies of individual processes in producing aluminium

0

10

20

30

40

50

60

70

80

Alumina Refining

Anode Production

Aluminium Smelting

Primary Casting

Secondary Casting

Rolliing Extrusion Shape Casting

Eff

icie

nc

y (%

)

Source: Thekdi (2003, Aluminum 2003, The Minerals, Metals & Materials Society, 225–237)

Figure 6.16: World production of primary and secondary aluminium, and the secondary share of total production

0

10

20

30

40

50

1971 1976 1981 1986 1991 1996 2001 2006

Pro

du

ctio

n (M

t/yr

) o

r %

Sec

on

dar

y

Year

Primary aluminum

Secondary aluminum

Percent Secondary

Aluminium Summary: Primary Energy Requirements

• Primary aluminium:

- 193 GJ/t world average today, assuming electricity supplied at 40% efficiency

• Secondary aluminium:

- 17 GJ/t world average today – more than a factor of 10 smaller than for primary aluminium

• Average of the above (with 18.7% recycled) is

160.3 GJ/t (more than 5 times that of steel)

Aluminium Summary (continued): • Future average with 90% secondary and current average energy use separately for primary and secondary Al: 34.5 GJ/t This is a reduction by a factor of 4.6 • Future average with 90% secondary, best projected energy intensities for primary and secondary steel: 23.3 GJ/t This is a reduction by a factor of 6.9• All of the above plus 60% electricity supply efficiency instead of 40%: 19.1 GJ/t This is a reduction by a factor of 8.4

• Thus, the overall potential reduction in the average primary energy intensity of aluminium is a factor of 5 to 8

Copper

Figure 6.17a World copper mining

0

2

4

6

8

10

12

14

16

18

20

1995 1997 1999 2001 2003 2005 2007

Year

Co

pp

er E

xtra

ctio

n (

Mt/

yr)

OtherRussiaIndonesiaAustraliaUSPeruChile

Figure 6.17b Copper mining in 2007

Chile36%

Peru8%US

8%

Other19%

Australia 6%

Indonesia 5%

Russia 5%

Canada 4%

Zambia 3%

Poland 3%

Kazakhstan 3%

Figure 6.17c End uses of copper in the US in 2003

Building Construction

48%

Electrical & Electronic Products

21%

Industrial Machinery & Equipment

10%

Transportation Equipment

10%

Consumer & General

Products 11%

Figure 6.18 Anthropogenic copper flows in ca. 1994 in Gg Cu/yr

Source: Graedel et al (2004, Environmental Science and Technology 38, 1242–1252)

Production of Copper Metal

• Copper minerals occur either as oxides (combined with CO3 or SiO2) or as sulfides (combined with S).

• A given ore body tends to have oxide minerals in the upper zone (close to air) and sulfide minerals in the lower zone

• There are two different produciton routes: Hydrometallurgy (acid related) – tends to be applied

to oxide minerals Pyrometallurgy (heat related) – tends to be applied

to sulfide minerals• In the transition zone of the ore body, either

technique can be applied, but there has been a shift to more use of hydrometallurgy

Steps in Pyrometallurgy (1):

• Extraction from the mine, crushing, and grinding• Froth flotation – mix with chemical foaming agents, as

ore minerals adhere to bubbles and float to surface and can be skimmed off. Produces a concentrate of 25-30% copper, mostly CuFeS2.

• Smelting – heating the concentrate in oxygen-enriched air to 1200-1250oC, with addition of silica (SiO2), partially oxidizing the Fe and S, releasing SO2 gas, and producing a molten copper matte (Cu2S*FeS) and molten slag (FeO*SiO2):

CuFeS2 + O2 + SiO2 → Cu-Fe-S + FeO*SiO2 + SO2 + heat

Steps in Pyrometallurgy (2):

• Converting – separating the Cu2S from the FeS in the copper matte and oxidizing the S. Produces blister copper (99% copper) and further iron slag

Cu2S + O2 → 2Cu° + 2SO2 + heat

2FeS + 3O2 + SiO2 → 2FeO•SiO2 + 2SO2 + heat

The smelting and converting reactions are exothermic –and the heat released is sufficient to maintain the required temperature once the process has started. This eliminates the need for fuel energy in state-of-the-art smelters & converters, but requires continuous rather than batch processing.

Steps in Pyrometallurgy (3):

• Fire refining. This is a process for removing most of the remaining O and S and, like previous steps, is carried out at a temperature of about 1200oC. The O is removed as CO2 through reaction with a hydrocarbon reducing agent (typically 5-7 kg per tonne of copper), while S is removed as SO2 through reaction with atmospheric oxygen. Fire refining is carried out in special rotating furnaces that are heated by combusting hydrocarbon fuels. The liquid product is directly cast into thin anodes that are interleaved with cathodes in electro-refining cells. The copper anodes still contain about 0.15% O and 0.002% S.

Steps in Pyrometallurgy (4):

• Electro-refining. This is an electrolysis process that involves electrochemically dissolving copper from impure copper anodes into a CuSO2-H2SO4-H2O electrolyte and electroplating pure copper from the electrolyte onto a cathode without the impurities. After 7-14 days the cathodes are removed from the cell and the pure metal is scrapped off. The reactions are:

Cuºanode → Cu 2+ + 2e- at the anode, and

Cu 2+ + 2e- → Cuº at the cathode.

Steps in Hydrometallurgy:• Leaching – excavate ores, pile in a heap, and add acid to

dissolve the ore, or drill holes into the ore body and pump in acid, and weeks to months later, pump out the leachate

• Concentration – add organic solvents to the acid solution, to selectively absorb copper from the solution

• Refining – an electrolysis process called electro-winning, similar to electro-refining except that the anode consists of an inert Pb-Sn-Ca mixture. The copper is electroplated onto the cathode from the Cu solution supplied from the concentration step rather than supplied by dissolution of a copper anode.

The combination of acid leaching and electro-winning is called the solvent-extraction electro-winning process, or SX-EW.

As previously noted, SX-EW (hydrometallurgy) is being used more and more. There are three disadvantages with this process:

• Any gold, silver, or molybdenum in the ore is lost• The fraction of the Cu present in the ore that can be

extracted is much less than using pyrometallurgy• Electro-winning requires much more electricity (1800-

2800 kWh/t) than the electro-refining process (300-400 kWh/t) used in pyrometallurgy

On the other hand, hydrometallurgy only requires crushing the mined ore to a 10-13 cm size, rather than grinding it

down to the size of individual mineral grains (100-200 μm) (as in pyrometallurgy). The grinding stage is very energy intensive. If 20 kWh of electricity are required per tonne of ore, the amount require per tonne of copper is 20 kWh/(copper fraction in the ore). Thus, for ore with 1% copper (a grade of 1%), the grinding energy requirement is 2000 kWh/tonne – comparable to the energy used for electro-winning (1800-2800 kWh/t) in the hydrometallurgy route.

Thus, the amount of energy used in producing copper increases rapidly with decreasing grade of ore.

This is because mining and concentrating the Cu account for 1/3 to 1/2 half of the total energy used in producing the pure metal for 1% ores, in contrast to iron and aluminum, where the metal concentrations in the ores are high (40-50% for Al, 60-70% for Fe) and mining and concentrating are a very small fraction of the total energy use

Figure 6.19 Estimated primary energy requirement to produce rolled copper tubes

0

50

100

150

200

250

300

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Pri

mar

y E

ner

gy

(GJ/

t o

f co

pp

er)

Grade of Ore (% copper)

Pyrometallurgy, High

Pyrometallurgy, Low

Hydrometallurgy, High

Hydrometallurgy, Low

Table 6.12: Average grade of the remaining Cu ores in different parts of the world

R e g i o n G r a d e ( % c o p p e r )

N o r t h A m e r i c a 0 . 4 7L a t i n A m e r i c a 1 . 0 0E u r o p e 1 . 5 0O c e a n i a 1 . 5 6E a s t A s i a 1 . 1 3C e n t r a l A s i a 1 . 5 1A f r i c a 3 . 0 0

Source: Giurco (2005, Towards sustainable metal cycles: The case of copper’, PhD Thesis, Department of Chemical Engineering, University of Sydney)

Energy Use in Producing Secondary Copper

• Depends strongly on the extent to which the scrap copper is contaminated with other materials

• Purest copper can be simply melted and recast• Less pure copper is re-melted and cast as

anodes, followed by electro-refining• Impure copper must be smelted and converted

Figure 6.20 Flowchart for refining and smelting of contaminated copper

B last fu rnace

A node furnace

C onverting fu rnace

E lectro lytic fu rnace

R eductionfurnace

C opper bearingscrap and coke

M olten black copper (80+% C u)

S crap(2-6% S n)

M olten rough copper (95+% C u)

S crap(>96% C u)

A nodes (99 .5% C u)

S n-P balloys

ZnOfum e

M ixed S n /P b /Znoxide dust

N ickel su lfa te &C u + precious m etals

s lim es

C athodes< 20 ppm im purities

Low grade ZnO fum e

G ranu lated s lag

A nodes scrap

S olid ified anodefurnace s lag

S olid ified converter slag

Source: Davenport et al (2002, Extractive Metallurgy of Copper, Elsevier Academic Press, Amsterdam)

Figure 6.21a Global production of primary and secondary copper, and scrap flow

0

2

4

6

8

10

12

14

16

18

1966 1971 1976 1981 1986 1991 1996 2001

An

nu

al F

low

(Mt)

Year

Primary Production

Secondary Production

Old scrap flow

2005

Figure 6.21b Recycling rate of scrap copper

0.0

0.1

0.2

0.3

0.4

0

1000

2000

3000

4000

5000

6000

7000

8000

1966 1976 1986 1996

Fra

ctio

n R

ecyc

led

Pri

ce (

2005

US

$/t)

Year2005

Price

Fraction Recycled

Figure 6.22 Distribution of the copper stock in the US of 238 kg per person

Infrastructure, 95, 40%

Plumbing, 32

Wiring, 28

Air conditioning and

refrigeration, 16

Industrial, 26

Domestic, 13

Motor Vehicles,16

Railway, ships,aircraft, 12

Building &Construction

76, 32%

Equipment39, 16%

Transportation28, 12%

Energy requirements for recycling Cu:

• ~ 4 GJ/t for Grade 1 scrap• ~ 20 GJ/t for Grade 2 scrap (≥ 94% Cu)• ~ 50 GJ/t for Grade 3 scrap (contaminated)

By comparison, 80-90 GJ/t are required for 1% ore and 180 GJ/t for 0.3% ore (however, one worker gives the primary energy requirement as only ~ 50 GJ/t for 0.35% ore)

So, except possibly for contaminated scrap compared to cases of primary Cu with low energy requirements, recycling saves a lot energy – potentially reducing the energy requirement by more than a factor of 40

This dismal picture will likely change soon, as Cu mining is expected by some analysts to peak in about 20

years, due to supply constraints

Figure 6.23 Quantity of metals vs grade of ores, showing two modes – corresponding to mineral crystals and atomic substitution

Atomicsubstitution

Mineralcrystals

Ore Grade

Source: Ayres et al (2003, The Life Cycle of Copper, Its Co-Products and Byproducts, Kluwer, Dordrecht)

Ways to limit demand for copper:

• More compact and smaller housing – less length of wire needed

• Smaller growth in electricity demand

• Replacement of copper with glass fibre in telecommunications

• Replacement of copper with PVC pipes in plumbing (PVC pipes are less energy-intensive)

Cement

Figure 6.24a World cement production

0

500

1000

1500

2000

2500

3000

1995 1997 1999 2001 2003 2005 2007

Year

Cem

ent

Pro

du

ctio

n (

Mt/

yr)

Other

Japan

US

India

China

Compounded Growth Rates, 2000-2007: China: 11.5%/yr Rest of world: 3.5%/yr Overall: 6.9%/yr

Figure 6.24b Cement production in 2007

India6%

Other26%

China49%

US 4%

Japan 3%

Russia 2%

S Korea 2%

Spain 2%

Turkey 2%

Italy 2%

Mexico 2%

Figure 6.24c Disposition of cement produced in the US in 2003

Ready-mix concrete

72%

Concrete products

13%

Contractors 6%

Building material dealers 3%

Other 2% Masonry cement4%

Production of Cement

• Crushing, grinding, and blending of raw materials into a homogenous powder

• Heating the raw materials to over 1400ºC in a kiln to produce clinker

• Grinding the clinker to a fine powder and mixing it with additions to form cement

Concrete is a mixture of about 10% cement and 90% aggregates (sand and gravel), with cement serving as the binding material. When stronger concrete is required, the proportion of cement is increased, so this increases the embodied energy of the concrete (as cement is the energy-intensive part of concrete).

Table 6.17: Composition of Portland cement

Portland cement (named after the Peninsula Portland in England) is 95% clinker and 5% gypsum. The elemental

composition of clinker is as follows:

Source: van Oss and Padovani (2002, Journal of Industrial Ecology 6, 89–105 )

C h em ic a l fo r m u la

S h o rth a n d n o ta tio n

A m o u n t

C a O C 6 5 .0 % S iO 2 S 2 2 .0 % A l2 O 3 A 6 .0 % F e 2O 3 F 3 .0 % M g O M 1 .0 % K 2 O +N a 2 O K + N 0 .8 % O th er (in c l. S O 3)

… (? ) 2 .2 %

Reactions occurring inside a cement kiln:

• Calcination,

CaCO3 → CaO + CO2

• Clinkering,

29C+8S+2A+F→2C2S + 6C3S+C4AF “alite” “belite”

Table 6.18: Composition of clinker and roles of the different components

C h em ica l form ula

S h or th an d n ota tion

D escr ip tion A m ou n t C om m en t

C a3S iO 5 C 3S Trica lc iu m silica te (“a lite” )

50 -70% Im p arts ea rly stren g th

C a2S iO 4 C 2S D ica lciu m silica te (“b e lite” )

10 -30% Im p arts lo n g- term stren g th

C a3A l2O 6

C 3A

Trica lc iu m a lu m in ate

0 -15 %

A cts a s a f lu x an d c on tr ib u tes to ear ly stren g th

C a4A l2F e 2O 1 0

C 4A F

Te traca lc iu m a lu m in oferr ite

0 -15 %

A cts a s a f lu x; con trib u te s to lon g-term stren gth , an d im p ar ts g ra y co lor

C aS O 4 •2 H 2 O C ? H 2 C a lc iu m su lfa te d ih y dra te (gyp su m )

3 -7% C on tro ls ea rly s ettin g

Source: van Oss and Padovani (2002, Journal of Industrial Ecology 6, 89–105 )

Figure 6.25 Layout of the zones in various cement kilns

20-200 Co 200-750 Co 1200-1450 Co750-1000 Co 1450-1300 CoFuel

Burner

Clinker

ClinkerCooler

DryingZone

PreheatZone

Sintering orBurning Zone

CoolingZone

RawMateria ls

Rotary K iln

CalciningZone

W et K iln 200m~

Long Dry K iln 130m~

Dry, Preheater Kiln 90m~

Dry, PreheaterPrecalcinor K iln

~ 50m

Preheater/ProcalcinorTower

PreheaterTower

Upper, “cool” end Lower, “hot” end

HeatingDrive offWater

CaCO 3 CaO+CO 2

CaO+SiO +Al O +Fe O2 2 3 2 3 C S+C S+C A+C A F3 2 3 4

C S A F

Source: Van Oss and Padovani (2002, Background Facts and Issues Concerning Cement and Cement Data, Open File Report 2005-1152, US Geological Survey, Reston, Virginia)

The binding properties of cement occur when it is mixed with water, which forms hydrated molecules that cling to each other. The binding requires materials with a high surface area (which must therefore be ground to a very fine powder) and materials that can form hydrates. This is relevant to the possibility of producing lower-energy alternatives to traditional Portland cement.

• Hydration of alite (gives early strength):

2C3S+6H(water)→C3S2H3 (CSH gel)+3CH (hydrated lime)

• Hydration of belite (gives long term strength):

2C2S + 4H(water)→C3S2H3+CH

Current national average energy use for producing cement:

• Theoretical minimum for clinkering: 1.67 GJ/t• Japan, 3.1 GJ/t• Germany, 3.8 GJ/t• European average, 4.1 GJ/t• China, 5.0 GJ/t• India, 5.0 GJ/t• Canada, 5.1 GJ/t• USA, 5.5 GJ/t• Columbia, 6.1 GJ/t

Options for reducing energy use in making cement:

• Shifting from wet to dry kilns• Better recovery of waste heat from kilns• Improved grinding techniques• Reducing the clinker portion (95% in Portland

cement) by blending in other materials, such as -blast furnace slag -fly ash from coal-fired powerplants -volcanic materials -natural limestone (easy to grind) -ordinary quartz sand (hard to grind)

Figure 6.26 Supply of fly ash and blast furnace slag

0

20

40

60

80

100

120

140

160

180

200

Ca

na

da

US

A

L A

me

ric

a

W E

uro

pe

E E

uro

pe

FS

U

Mid

dle

Ea

st

Afr

ica

AU

& N

Z

Ch

ina

Ind

ia

Ko

rea

Ja

pa

n

SE

As

ia

Mt

in 2

020

Cement Demand

Slag supply

Fly Ash supply

Source: Humphreys and Mahasenan (2002, Toward a Sustainable Cement Industry, Substudy 8: Climate Change, World Business Council for Sustainable Development, Cement Sustainability Initiative, www.wbcsdcement.org

Other options:

• Development of entirely new cements• Integrated production of cement and electricity

(using waste heat at 300ºC from the clinker cooler)

• Use of concentrated solar energy• Improved durability of cement (or of steel

reinforcing)• Reduced use where feasible without

compromising safety (i.e., baffled basement walls)

Glass

Glass

• Types: container, flat or “float”, and fibrous (insulation, textile fibreglass)

• Raw materials: sand, limestone, maybe soda ash, borate, feldspar and clay

• Production process: - preparation of inputs

- melting of raw materials and refining (removal of bubbles)- shaping the molten glass into the desired final shapes

Table 6.22: Typical inputs to glass

Type of glassMaterial Container

glassFlat (float)

glassFiberglass Insulation

Textile Fiberglass

Sand (SiO2) 0.65 0.73 0.54 0.54Limestone (CaCO3 or CaMg(CO3)2) 0.19 0.24 0.19 0.12Soda ash (Na2CO3) 0.22 0.23 0.22 0.00Borate 0.00 0.00 0.10 0.15Feldspar 0.11 0.00 0.11 0.00Clay 0.00 0.00 0.00 0.34Total 1.17 1.20 1.16 1.15Chemical CO2 emission (tCO2/t) 0.17 0.20 0.16 0.15Chemical CO2 emission (tC/t glass) 0.046 0.054 0.044 0.041

Source: Ruth and Dell’Anno (1997, Resources Policy 23, 109–124)

Types of furnaces for melting of raw materials:

• Regenerative, recuperative

- use fuels (natural gas), maximum efficiency now ~50% ((heat added to raw materials) / (fuel energy used)), could be pushed to 75% (giving a 1/3 reduction in fuel use)

• Electric – efficiency of 70-90%, but must account for losses in generating and transmitting electricity.

- applied to fibrous glass

Typical primary energy use today

• Flat and container glass: ~ 20-30 GJ/t• Fibrous glass at 40%

electricity supply efficiency: ~ 60 GJ/t• Fibrous glass at 60%

electricity supply efficiency: ~ 40 GJ/t• Savings through recycling: ~ 20-30%

Figure 6.27 Rates of Recycling of Glass Containers

0

10

20

30

40

50

60

70

80

90

100

Au

str

ia

Ne

the

rla

nd

s

Ge

rma

ny

Sw

ed

en

Be

lgiu

m

De

nm

ark

Fin

lan

d

Fra

nc

e

Po

rtu

ga

l

Ire

lan

d

Sp

ain

Ita

ly

Gre

ec

e

UK

US

A

Per

cen

t R

ecyc

led

Paper and Paper Products

Production of Paper and Paper Products

• Acquisition of fibres• Pulping• Bleaching• Manufacture of paper from pulp

Figure 6.28a Production of different kinds of paper and paper products

0

50

100

150

200

250

300

350

400

1961 1966 1971 1976 1981 1986 1991 1996 2001 2006

Year

Pro

du

ctio

n (

Mt/

yr)

Other

Wrapping & Packaging

Household & Sanitary

Printing and Writing

Newsprint

Figure 6.28b Production of paper and paper products by region

0

50

100

150

200

250

300

350

400

1961 1966 1971 1976 1981 1986 1991 1996 2001 2006

Year

Pro

du

ctio

n (

Mt/

yr)

Africa

Oceania

L America & Caribbean

North America

Europe

Asia

Figure 6.29 Annual per capita paper consumption

0

50

100

150

200

250

300

350

1960 1970 1980 1990 2000 2010

kg/p

erso

n/y

ear

Year

USA South AmericaCanada AsiaOceania Middle East & North AfricaEurope Sub-Saharan AfricaCentral America & Caribbean

Figure 6.30 Rates of paper recycling

0

10

20

30

40

50

60

70

80

90

100

Ire

lan

dN

orw

ay

Sw

itze

rla

nd

Ne

the

rla

nd

sS

we

de

nU

KS

lov

en

iaA

us

tria

Sp

ain

De

nm

ark

Po

rtu

ga

lF

ran

ce

Fin

lan

dH

un

ga

ryIt

aly

Be

lgiu

mE

sto

nia

Slo

va

k R

ep

ub

licR

om

an

iaL

atv

iaC

zec

h R

ep

ub

licL

ith

ua

nia

Gre

ec

eP

ola

nd

Bu

lga

ria

Cy

pru

sM

alt

a

Ja

pa

nC

an

ad

aU

S

Pap

er R

ecyc

lin

g R

ate

(%)

Sources of Fibre for Paper:

• Roundwood (wood removed from forests or other areas)

• Sawmill residues• Discarded paper

Pulping Processes

• Mechanical • Chemical• Semi-chemical

Mechanical Pulping

• Breaks apart the wood by grinding • Both fibre and lignin are turned into pulp, so the

pulp yield is high - 85% of the original wood mass.

• Lots of heat is generated that can be used elsewhere in the paper mill

Chemical Pulping

• Soften wood chips with steam• Then cook for several hours at 160-170oC under

pressure in a highly alkaline solution (contains NaOH and Na2S) called white liquor

• This dissolves the lignin, leaving only the fibres (40-55% of the wood) to form pulp

• The spent liquor (now called black liquor) and bark are burned to produce heat and electricity for use by the pulp and paper mill

Figure 6.31 Annual trade of different kinds of pulp

0

50

100

150

200

250

1961 1966 1971 1976 1981 1986 1991 1996 2001 2006

Year

Pu

lp P

rod

uct

ion

(M

t/yr

)

Recycled

Non-wood

Dissolving

Semi-chemical

Chemical

Mechanical

Bleaching

• Process of removing residual lignin from the pulp, which otherwise causes the pulp to be dark

• Requires a chemical (Cl2, ClO2, H2O2 or O3) that oxidizes the lignin but not the fibre (cellulose and hemi-cellulose)

• Cl2 bleaching causes severe water pollution, so there is a move toward elemental chlorine-free (ECF) bleaching (using ClO2) or totally chlorine-free (TCF) bleaching (using H2O2 or O3)

Steps in making paper from pulp

• Addition of water sufficient to give a water:fibre ratio of 100:1 (i.e., a consistency of 1%).

• Forming – spread stock over a wire screen, then remove sufficient water through gravity and suction to give a consistency of 20%

• Pressing – increase consistency to 40-45% by passing the sheet with felt through 3-4 pairs of press cylinders

• Drying – pass sheet through 40-50 steam-heated cylinders, to give a consistency of 90-95%

Options to reduce energy use per unit of paper made

• Integration of pulp and paper mills• Heat recovery from mechanical pulping• Reductions in market demand for bleached

paper products (through consumer awareness)• More efficient drying of initial pulp sheets• More efficient cogeneration• Increased recycling

Cogeneration in the pulp and paper industry

• Currently very inefficient – only 10-15% electrical efficiency, in part to avoid producing excess electricity because it can’t be sent to the grid in many jurisdictions due to monopolistic practices by power utilities

• Potential electrical efficiency of 27-30% (and 72% overall efficiency) with gasification of black liquor followed by combined-cycle power generation. Some problems still to be worked out

• This could make the pulp and paper mill a net source of energy – this would be renewable, biomass-based energy

Other possibilities:

• Production of dimethyl ether (a substitute for diesel fuel in the transportation sector) from biomass wastes, integrated with pulp and paper production, is potentially more attractive in terms of energy saving than is cogeneration of heat and electricity

• Development of completely closed mills – all liquids flow back through the mill, rather than be ejected with heat (and pollutants) to the environment. At present it would be hard to make use of the saved heat.

The energy balance in recycling of paper includes:

• The net energy required to make paper from virgin fibres, taking into account the energy that can be produced from black liquor and forestry residues and the energy required to make any fertilizers that are applied to plantation forests

• The energy that can be obtained from incineration of waste paper to cogenerate heat and electricity if it is not recycled (landfilling is totally out of the question)

• The energy required during recycling of waste paper, including the energy required to collect waste paper and transport it to the recycling plant

• The energy that could be supplied from the biomass that is saved when waste paper is recycled

Rough energy balance:

• Paper from wood: gross energy requirement: ~ 29 GJ/t Potential energy production: ~ 31 GJ/t Net energy requirement: -2 GJ/t• Paper from waste paper: ~ 20 GJ/t

So, in terms of gross energy requirements,recycling gives a 30% savings. However, in termsof net energy use, recycling increases the energyrequirement.

There is, of course, more to it

• Incineration of waste paper with cogeneration saves ~26 GJ/t of primary energy, so the overall energy gain with production of paper from virgin fibres and later incineration is ~ 28 GJ/t

• BUT – for each tonne of waste paper that is recycled, 2.2 tonnes of biomass are saved.

• For the set of assumptions in Table 6.29, this saves 52 GJ of primary energy, for a net energy gain of ~ 32 GJ/t

• Thus, recycling is slightly better from an energy point of view, but for slightly different assumptions, it could be slightly worse.

Plastics

• Produced by reacting steam with hydrocarbons at high T and P, thereby breaking the C-C bonds in the hydrocarbons (so this process is called steam cracking)

• Most are made from naptha, an intermediate product in the refining of petroleum

• Cracking produces methane, olefins, and aromatics, which are the precursors to various kinds of plastic

Figure 6.32a: Plastics production in 2007

Europe24%

NAFTA23%

China15%

Japan6%

Rest of Asia17%

FSU 3%

Middle East & Africa 8%

Latin America 4%

Figure 6.32b: Uses of plastics in Europe

Packaging37%

Building & Construction

21%

Automotive8%

Electrical and Electronic

6%

Other28%

Figure 6.33 Plastics and other petrochemicals made from petroleum

Source: Geiser (2001, Materials Matter: Towards a Sustainable Materials Policy, MIT Press, Cambridge)

Most plastics are long chains of molecules (monomers), hence the prefix “poly” in the names of most plastics. The major plastics are:

• Polyethylene• Polypropylene• Polyvinyl chloride• Polystyrene

Figure 6.34 Production of plastics in Europe

Low density polyethylene

17%

High density polyethylene

12%

Polypropylene18%

Polyvinyl chloride

12%

Polystyrene8%

PET (polyethylene teraphthalate)

7%

Polyurethane7%

Other19%

Energy Use in Making Plastics

• Feedstock Energy: 20-40 GJ/t• Process energy: 20-120 GJ/t• Total energy: 50-160 GJ/t

Energy is used for heating to up to 1000oC (to “crack” naphtha or other raw materials), for chilling (sudden cooling to as low as -150oC is needed for some of the reaction and separation steps), and for pumps and motors

Figure 6.35 Primary energy inputs to make plastic

0

20

40

60

80

100

120

140

160

180

Nylo

n-6

,6

Nylo

n-6

Ep

ox

y re

sin

Po

lya

cry

late

Po

lyc

arb

on

ate

Me

lam

ine

re

sin

Po

lyu

reth

an

e

Po

lys

tyre

ne

Po

lya

cry

lon

itri

le

Po

lye

thyle

ne

Syn

the

tic

ru

bb

er

Ph

en

ol f

orm

ald

eh

yd

e re

sin

s

PE

T

Po

lyvin

yl a

ce

tate

Po

lyvin

yl c

hlo

rid

e

Ure

a re

sin

En

erg

y In

pu

t (G

J/t

on

ne)

Process energy

Feedstock Energy

Energy Savings Potential

• For the cracking step – 25% or more savings should be typically possible in the medium term (with modest further improvement of existing state-of-the-art crackers)

• Improved cogeneration (if present) or implementation of cogeneration (if not already used) (both steam and electricity are required)

• Adjustment of piping systems, use of variable speed drives (mentioned in the Buildings chapter), better chiller controls and increasing the temperature of chilled water produced by the chillers reduced electricity use by 50% in one case

Energy Savings Through Recycling

• The feedstock energy is saved (except possibly for small material losses during the recycling process)

• Some (often large) portion of the process energy is also saved (no need to crack hydrocarbons again)

• Energy savings is typically 85-90% according to the one source

• Obstacle: the need to separate different kinds of plastic from one another

Figure 6.36 Disposition of plastics waste in Europe

0

5

10

15

20

25

30

1995 1997 1999 2001 2003 2005 2007

Mt

per

Year

Year

Energy recovery

Mechanical recycling

Feedstock recycling

Sent to landfill

20%

28%

Source: Plastics Europe (2008, The Compelling Facts about Plastics 2007: An Analysis of Plastics Production, Demand and Recovery for 2007 in Europe, www.plasticseurope.org)

Where was this photo was taken?

Answer: in the middle of the Pacific Ocean, 1400 km north of

Hawaii!

Eastern and Western Pacific Garbage Patches – about 3-5 Mt each?

Floating debris occasionally washes ashore on Hawaii

Urban runoff

Contents of the gut of an albatross, killed by ingesting floating plastic garbage

For more information, go to

www.greatgarbagepatch.org

Petroleum refining

• Potential for 20% savings in the US if no other changes occur. However:

• 10% increase in energy use if S concentration is decreased from 30 ppm to 1 ppm to meet more stringent pollution emission requirements (current most-stringent regulations are around a 15 ppm limit)

• Increasing energy use with a shift to heavier grades of oil as the lighter grades are depleted.

• Big jump in processing energy use for oil shales and tar sands

Table 6.31: Energy Use for Petroleum Refining

Energy Use (GJ/tonne oil)Extraction Refining Total

Energy Use as a % of Energy in Products

US conventional onshore oil 1.3 2.9 4.2 10.0Canadian conventional onshore oil 2.4 3.0 5.4 12.8Conventional offshore oil 3.9 3.0 6.9 16.4Heavy oils 2.9 3.0 5.9 14.1Canadian tar sands 12.9 3.0 15.9 37.8

Source: (S&T)2 Consultants (2005, Documentation for Natural Resources Canada’s GHGenius Model 3.0, www.ghgenius.ca )

Chemicals, General Considerations

• Importance of improved catalysts • Importance of advanced membranes (for

separating materials) in reducing general energy use in the chemical industry

• Importance in capturing exothermic heat (most reactions in the chemical industry are exothermic, and the total exothermic release equals 60% of the overall process energy used in the manufacture of products produced by exothermic reactions)

Figure 6.37 Membranes

MICROFILTRATION

ULTRAFILTRATION

REVERSE OSMOSIS

DIALYSIS

retains suspended matter

passes dissolved substancesand water

retains dissolved matter

passes some macromolecules,microsolutes, ions, and water

retains all ions

passes water

retains dissolved matter

passes microsolutes andwater

M MM

H H H

ELECTRODIALYSIS

GAS SEPARATION

COUPLED TRANSPORT

retains nonionic matter

passes ionic matter

retains membrane impermeablegases

passes membrane permeablegases

passes carrier complex ions

M denotes monovalent metal ion

H denotes hydrogen+

+

Source: Goldemberg et al (1998, Energy for a Sustainable World, Wiley Eastern, New Dehli)

Cogeneration and heat management

• It is estimated that the amount of waste heat in exhaust flows and pressurized gases in US industry that could be used in practice to generate electricity is sufficient to supply about 13% of US electricity demand, with no extra fuel use

• Efficiencies of electricity generation, and overall efficiencies in industrial cogeneration are quite low, but leave room for substantial improvement (although there are often logistical difficulties in upgrading existing facilities)

Figure 6.38a Industrial cogeneration using an internal combustion engine or simple-cycle gas turbine

Typical electrical efficiencies: 22-35%Typical overall efficiencies: 39-54%

Waste Hea t

Heat Recovery

e1

h3

h2h1

F1

Useful Heat

e = F1 1 1

h = (1- ) F2 1 2 1

ICE orGas Turbine, 1 2

overall 1 1 2= +(1- )

Figure 6.38b Industrial cogeneration using a steam turbine

Typical electrical efficiency: 9-13%Typical overall efficiency: 61-68%

W aste H eat

Heat R ecovery

e 2

h 7

h 6Steam Turb ine

Bo iler,

F 2

4

h 5

h 3

5

h 4

3

Useful H eat

h = Fe = Fh = (1- )Fh = (1- )Fh = (h +h )

3 3 2

2 3 4 2

4 3 2

5 3 4 2

6 5 4 5

o ve ra ll 2 6 2 = (e +h )/F o ve ra ll = (e +h )/F 2 6 2

Figure 6.38c Combined-cycle industrial cogeneration

Typical electrical and overall efficiencies: 30-36% and 60-70%

G as Turbine Steam Tu rb ine

W aste H eat

Heat R ecovery

Bo iler,

Useful Heat

e 3 e 4

6=0.29

F 3 h 8

8=0.12

F 4

h 9

h 11

h 1 0

h 1 3

h 1 2

9=0.51

7=0.8

e = Fh = (1- )F

3 5 3

8 6 3

h = (h +F )e = hh = (1 - )h

a 7 8 4

4 8 9

11 8 9

h = (1 - )(h +F )h = (h +h )

1 0 7 8 4

1 2 9 1 0 11

o ve ra ll 3 4 1 2 3 4 = (e +e +h )/F +F )

Pinch Analysis

• Many industrial processes have simultaneous heating and cooling requirements

• Pinch analysis is a powerful technique integrating the two (when cold and hot fluid streams are brought together, the hot stream will be cooled and the cold stream warmed)

• Heating and cooling energy savings of 50% or more can sometimes be achieved.

Figure 6.39 Pinch Analysis

• Heating only above the pinch point

• Cooling only below the pinch point

• No heat flow from above to below the pinch point should be allowed

100

50

150

1000 Units Heat load

Pinch Point

417Units

497 Units

Temperature Co