Transcript Figure 1.1 - University of Toronto

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]
Publisher: Earthscan, UK
Homepage: www.earthscan.co.uk/?tabid=101807
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.
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
60
Percent Industrial
50
Global
Average:
37.5%
40
30
20
10
0
Africa
Europe
North
America
Central
America
South
America
Asia
Oceania
Figure 6.2a Industrial energy use in OECD countries in 2005
Textile and Non-specified
11%
leather 2%
Iron and Steel
16%
Construction
1%
Wood and
wood
products 2%
Chemical &
Petrochemical
20%
Pulp and
Paper 13%
Food and
Tobacco 7%
Non-Ferrous
metals 6%
Mining and
Quarrying 2%
Machinery
7%
Transport
equipment
2%
Non-metallic
minerals 8%
Figure 6.2b Industrial energy use in non-OECD countries
Non-specified
25%
Textile and
leather
3%
Iron and Steel
25%
Construction
1%
Wood and
wood products
1%
Chemical &
Petrochemical
13%
Pulp and Paper
2%
Food and
Tobacco 7%
Mining and
Quarrying 2%
Machinery
4%
Transport
equipment
2%
Non-Ferrous
metals
5%
Non-metallic
minerals
11%
on
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Gobal Primary Energy Use (EJ/yr)
Figure 6.3 Global primary energy use for production of the 12
commodities (other than the production of fuels)
using the most energy
35
30
25
20
15
10
5
0
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
Commodity
Cement
Steel
Paper & Paper
Products
Lime
Plastics
Ammonia
Ethylene
Non-fibrous glass
Aluminum
Copper
Production
(Mt/year)
2600
1320
Primary Energy
Intensity (GJ/t)
4-8
20-40
Principle
Energy Input
Coal, NG, or Oil
Coal
Ave C
Emission (tC/t)
0.3
0.7
365
277
260
132
110
95
38
16
16-42
0.4
50-160
36-44
20-30
20-25
~160
~85
Biomass
Electricity
Oil
Natural gas
Oil
Coal, Oil, or NG
Electricity
Electricity
0.0
0.03
1-3
0.7
0.6
0.6
4.2
2.2
Figure 6.4: Trends in production of major commodities
(solid lines use the left scale, dashed lines the right scale)
3000
2000
Cement
Steel
Paper
Plastics
Aluminum
Copper x 10
Zinc x 10
250
200
1500
150
1000
100
500
50
0
1960
1970
1980
1990
Year
2000
0
2010
Annual Production (Mt)
Annual Production (Mt)
2500
300
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
1400
Raw Steel Production (Mt/yr)
1200
1000
Other
Ukraine
S Korea
Russia
US
Japan
China
Compounded Growth Rates, 2000-2007:
China: 19.1%/yr
ROW:
2.8%/yr
Overall: 6.4%/yr
800
600
400
200
0
1995
1997
1999
2001
Year
2003
2005
2007
Figure 6.5b: Production of raw steel in 2007
Other
28%
China
37%
Italy 2%
Brazil 2%
Germany 3%
Ukraine 3%
S Korea 4%
Russia
5%
US
7%
Japan
9%
Figure 6.5c End uses of steel in the US in 2003
Service Centers
and Distributors
27%
Other
33%
Construction
22%
Containers
3%
Transportation
15%
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
1200
1000
Other
Electric arc furnace
Prodcution (Mt/yr)
Basic oxygen furnace
800
Open Hearth Furnace
600
400
200
0
1975
1990
Year
2003
Figure 6.8 Energy used by EAFs per tonne of crude steel
High power/
long arc operation
Oxygen and
carbon lance
manipulator
Computer control
Foaming slag practice
Water cooled roof/oxy-fuel burner
10
8
Oxygen
lancing
6
630 kWh/tcs
4
Water cooled
walls
Bottom tap hole
Pneumatic
bath stirring
Ladle furnace
Secondary
metallurgy
EBT (slag-free)
Scrap preheating
Higher electric power
supply
Electricity consumption
350 kWh/tcs
DC technology
2
6.5 kg/tcs
Electrode consumption
2.2 kg/tcs
0
1965
1970
1975
1980
1985
1990
year
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 blastfurnace/BOF route for making primary steel
1.9
Coal
Iron ore
Coke
oven
12.4
Blast
furnace
Ore preparation
2.6
Fluxing agent
Pellets
Pig
iron
0.3
Basic
oxygen
furnace
0.6
Crude
steel
Scrap (10%)
Refining
casting Cast
steel
2.1
19.9 GJ/t
Rolling
Shaping
Quality flat
and long
products
Figure 6.9b Primary energy use with advanced
blast-furnace/BOF making primary steel
1.2
Coal
Iron ore
Coke
oven
11.9
Blast
furnace
Ore preparation
2.2
Fluxing agent
Pellets
Pig
iron
-1.0
Basic
oxygen
furnace
0.6
Crude
steel
Refining
casting Cast
steel
1.5
16.9 GJ/t
Rolling
Shaping
Scrap (10%)
By comparison, the present world average
primary energy requirement for primary steel is
about 36 GJ/t
Quality flat
and long
products
Figure 6.9c Primary energy use with best current direct
reduction/EAF steel making
1.4
Iron ore
Ore preparation
Natural gas
or Coal
13.4
3.5
Direct
reduction Sponge
iron
0.6
Crude
steel
Oxygen
Fossil fuel
Refining
casting
1.0
Cast
steel
Rolling
Shaping
20.0 GJ/t
Flat
products/
shapes
Figure 6.9d Primary energy use with advanced direct
reduction/EAF steel making and advanced refining,
casting, and shaping
1.4
Iron ore
Ore preparation
Natural gas
or Coal
11.3
Direct
reduction Sponge
iron
3.5
Electric
arc furnace Crude
steel
Oxygen
Fossil fuel
0.75
Refining
casting
shaping
16.9 GJ/t
Flat
products/
shapes
Figure 6.9e Primary energy use with advanced
smelting-reduction/BOF steel making and advanced
refining, casting, and shaping
13.4
-1.0
Smelting
reduction
Basic
oxygen
furnace
Iron ore
Coal
Oxygen
Pig
iron
(Scrap)
Crude
steel
0.75
Refining
Casting
Shaping
13.2 GJ/t
Quality flat
and long
products
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%.
Figure 6.10a Current mill using scrap steel to make
secondary steel
Scrap
3.4
Electric
arc
Crude
furnace steel
0.6
Refining
casting Cast
steel
1.0
5 GJ/tcs
Rolling
Shaping
Bar/shapes
Flat products
Oxygen
Fossil 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
Scrap
0.5
2.3
Scrap
upgrading
Electric
arc
furnace
Crude
steel
0.75
Refining
casting
Shaping
3.5 GJ/tcs
Bar/shapes
Flat products
Fossil fuel
Oxygen
de Beer et al (1998a, Annual Review of Energy and the Environment 23, 123–205)
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%.
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:
• Future average with 90% secondary
and current best practice as average:
This is a reduction by a factor of 3.8
• Future average with 90% secondary,
best projected energy intensities for
primary and secondary steel:
This is a reduction by a factor of 4.5
• All of the above plus 60% electricity
supply efficiency instead of 40%:
This is a reduction by a factor of 5.8
26.3 GJ/t
6.9 GJ/t
5.9 GJ/t
4.5 GJ/t
• 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
Primary Aluminium Production (kt/yr)
40
35
30
Other
US
Canada
Russia
China
25
20
15
10
5
0
1995
1997
1999
2001
Year
2003
2005
2007
Figure 6.11b Production of primary aluminium in 2007
Other
22%
China
32%
UAE 2%
S Africa 2%
Norway 3%
India 4%
Brazil 4%
Australia
5%
Russia
11%
US
7%
Canada
8%
Figure 6.11c End uses of aluminium in the US in 2003
Other
4%
Construction
16%
Consumer
Durables
7%
Transportation
36%
Containers &
Packaging
23%
Machinery &
Equipment
7%
Electrical
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
Bauxite 168.2
MATERIAL FLOW
METAL FLOW
Alumina 61.3
Total Products
Stored in Use
Since 1888
560.7
Primary
Aluminium used
31.6
Ingots 63.8
Fabricated and
Finished
Finished
Products (input) Products (output)
62.5
37.6
Building 32% Transport 28%
o.a.Automotive 16%
Net Addition 2005: 22.2
Remelted
Aluminium 32.3
Other
Applications
1.1
o.a.Recycled
Aluminium 15.3
Traded
New
Scrap 1.3
Bauxite Residues 70.8
and Water 36.1
Fabricator
Scrap
17.0
Metal Losses 1.3
Traded
New
Scrap 7.9
Other
11%
Engineering
and Cable 28%
Packaging
1%
Old
Scrap
7.4
Not Recycled in Under
Investigation: 3.3
2005 3.5
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
Source: IAI (www.world-aluminium.org)
Figure 6.13 Secondary energy used in making
aluminium metal
Materials,
Fuels
17.6%
Smelting,
Electricity
56.4%
Mining
0.4%
Refining,
Electricity
1.7%
Refining,
Fuels
23.9%
Figure 6.14: World average electricity use for the
production of aluminium
30
Electricity Use (MWh/t)
25
20
15
10
5
0
1950
1960
1970
1980
Year
1990
2000
2010
Figure 6.15 Efficiencies of individual processes in
producing aluminium
80
70
Efficiency (%)
60
50
40
30
20
10
0
Alumina
Anode Aluminium
Refining Production Smelting
Primary
Casting
Secondary
Casting
Rolliing
Extrusion
Shape
Casting
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
Production (Mt/yr) or % Secondary
50
Primary aluminum
40
Secondary aluminum
Percent Secondary
30
20
10
0
1971
1976
1981
1986
Year
1991
1996
2001
2006
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:
This is a reduction by a factor of 4.6
• Future average with 90% secondary,
best projected energy intensities for
primary and secondary steel:
This is a reduction by a factor of 6.9
• All of the above plus 60% electricity
supply efficiency instead of 40%:
This is a reduction by a factor of 8.4
34.5 GJ/t
23.3 GJ/t
19.1 GJ/t
• 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
20
Copper Extraction (Mt/yr)
18
16
14
Other
Russia
Indonesia
Australia
US
Peru
Chile
12
10
8
6
4
2
0
1995
1997
1999
2001
Year
2003
2005
2007
Figure 6.17b Copper mining in 2007
Other
19%
Chile
36%
Kazakhstan 3%
Poland 3%
Zambia 3%
Canada 4%
Russia 5%
Indonesia 5%
Australia 6%
US
8%
Peru
8%
Figure 6.17c End uses of copper in the US in 2003
Consumer &
General
Products 11%
Transportation
Equipment
10%
Industrial
Machinery &
Equipment
10%
Electrical &
Electronic
Products
21%
Building
Construction
48%
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 electrorefining 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 electrowinning, 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 (18002800 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 (4050% 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
300
Primary Energy (GJ/t of copper)
Pyrometallurgy, High
Pyrometallurgy, Low
250
Hydrometallurgy, High
Hydrometallurgy, Low
200
150
100
50
0
0.0
0.5
1.0
1.5
2.0
Grade of Ore (% copper)
2.5
3.0
Table 6.12: Average grade of the remaining Cu
ores in different parts of the world
R e g io n
N o r th A m e r ic a
L a tin A m e r ic a
E urope
O c e a n ia
E a s t A s ia
C e n tr a l A s ia
A fr ic a
G rade
(% c o p p e r )
0 .4 7
1 .0 0
1 .5 0
1 .5 6
1 .1 3
1 .5 1
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
Copper bearing
scrap and coke
Low grade ZnO fume
Blast furnace
Granulated slag
Molten black copper (80+% Cu)
Scrap
(2-6% Sn)
Solidified
converter slag
Mixed Sn/Pb/Zn
oxide dust
Converting furnace
Molten rough copper (95+% Cu)
Scrap
(>96% Cu)
Solidified anode
furnace slag
Reduction
furnace
ZnO
fume
Sn-Pb
alloys
Anode furnace
Anodes (99.5% Cu)
Anodes scrap
Electrolytic furnace
Cathodes
< 20 ppm impurities
Nickel sulfate &
Cu + precious metals
slimes
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
18
16
Primary Production
Secondary Production
Annual Flow (Mt)
14
Old scrap flow
12
10
8
6
4
2
0
1966
1971
1976
1981
1986
Year
1991
1996
2001
2005
Figure 6.21b Recycling rate of scrap copper
8000
0.4
7000
Fraction Recycled
0.3
5000
4000
0.2
3000
2000
0.1
Price
1000
0
1966
0.0
1976
1986
Year
1996
2005
Fraction Recycled
Price (2005 US$/t)
6000
Figure 6.22 Distribution of the copper stock in the US
of 238 kg per person
Transportation
28, 12%
Railway,
Motor ships,aircraft, 12
Vehicles,16
Equipment
39, 16%
Domestic, 13
Industrial, 26
Air conditioning
and
refrigeration, 16
Building &
Construction
76, 32%
Wiring,
28
Plumbing, 32
Infrastructure,
95, 40%
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
Atomic
substitution
Mineral
crystals
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
3000
Cement Production (Mt/yr)
2500
2000
Other
Japan
US
India
China
Compounded Growth Rates, 2000-2007:
China:
11.5%/yr
Rest of world:
3.5%/yr
Overall:
6.9%/yr
1500
1000
500
0
1995
1997
1999
2001
Year
2003
2005
2007
Figure 6.24b Cement production in 2007
Other
26%
China
49%
Mexico 2%
Italy 2%
Turkey 2%
Spain 2%
S Korea 2%
Russia 2%
Japan 3%
India
US
6%
4%
Figure 6.24c Disposition of cement produced
in the US in 2003
Other 2%
Masonry cement
4%
Building material
dealers 3%
Contractors 6%
Concrete
products
13%
Ready-mix
concrete
72%
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:
Chemical
formula
CaO
SiO 2
Al2 O3
Fe 2O3
MgO
K2O+Na2O
Other (incl.
SO3)
Shorthand
notation
C
S
A
F
M
K+N
…(? )
Amount
65.0%
22.0%
6.0%
3.0%
1.0%
0.8%
2.2%
Source: van Oss and Padovani (2002, Journal of Industrial Ecology 6, 89–105 )
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
Chemical
formula
Ca3SiO5
Shorthand Description
notation
C 3S
Tricalcium silicate
(“alite”)
C 2S
Dicalcium silicate
(“belite”)
Amount Comment
C 3A
Tricalcium aluminate
0-15%
Ca4Al2Fe2O10 C4AF
Tetracalcium
aluminoferrite
0-15%
CaSO4 •2H2 O C?H2
Calcium sulfate dihydrate 3-7%
(gypsum)
Ca2SiO4
Ca3Al2O6
50-70%
10-30%
Imparts early
strength
Imparts long-term
strength
Acts as a flux and
contributes to early
strength
Acts as a flux;
contributes to longterm strength, and
imparts gray color
Controls early setting
Source: van Oss and Padovani (2002, Journal of Industrial Ecology 6, 89–105 )
Figure 6.25 Layout of the zones in various cement kilns
Preheater/Procalcinor
Tower
Rotary Kiln
Dry, Preheater
Precalcinor Kiln
~ 50m
Preheater
Tower
Dry, Preheater Kiln
~ 90m
Long Dry Kiln
~ 130m
Wet Kiln
~ 200m
Drying
Zone
Raw
Materials
o
20-200 C
Drive off
Water
Preheat
Zone
o
200-750 C
Heating
Upper, “cool” end
Calcining
Zone
o
750-1000 C
CaCO3
CaO+CO2
Sintering or
Burning Zone
o
Cooling
Zone
1200-1450 C
CaO+SiO2+Al2O3+Fe2O3 C3S+C2S+C3A+C4AF
C
S
A
F
Clinker
o
1450-1300 C
Fuel
Burner
Lower, “hot” end
Clinker
Cooler
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
200
Cement Demand
180
Slag supply
160
Fly Ash supply
Mt in 2020
140
120
100
80
60
40
20
SE Asia
Japan
Korea
India
China
AU & NZ
Africa
Middle East
FSU
E Europe
W Europe
L America
USA
Canada
0
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
Material
Sand (SiO2)
Limestone (CaCO3 or CaMg(CO3 )2 )
Soda ash (Na2 CO3 )
Borate
Feldspar
Clay
Total
Chemical CO2 emission (tCO2/t)
Chemical CO2 emission (tC/t glass)
Container
glass
0.65
0.19
0.22
0.00
0.11
0.00
1.17
0.17
0.046
Type of glass
Flat (float) Fiberglass
glass
Insulation
0.73
0.54
0.24
0.19
0.23
0.22
0.00
0.10
0.00
0.11
0.00
0.00
1.20
1.16
0.20
0.16
0.054
0.044
Source: Ruth and Dell’Anno (1997, Resources Policy 23, 109–124)
Textile
Fiberglass
0.54
0.12
0.00
0.15
0.00
0.34
1.15
0.15
0.041
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:
• Fibrous glass at 40%
electricity supply efficiency:
• Fibrous glass at 60%
electricity supply efficiency:
• Savings through recycling:
~ 20-30 GJ/t
~ 60 GJ/t
~ 40 GJ/t
~ 20-30%
USA
UK
Greece
Italy
Spain
Ireland
Portugal
France
Finland
Denmark
Belgium
Sweden
Germany
Netherlands
Austria
Percent Recycled
Figure 6.27 Rates of Recycling of Glass Containers
100
90
80
70
60
50
40
30
20
10
0
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
400
350
Other
Wrapping & Packaging
Production (Mt/yr)
300
Household & Sanitary
Printing and Writing
250
Newsprint
200
150
100
50
0
1961
1966
1971
1976
1981
1986
Year
1991
1996
2001
2006
Figure 6.28b Production of paper and paper
products by region
400
350
Production (Mt/yr)
300
250
Africa
Oceania
L America & Caribbean
North America
Europe
Asia
200
150
100
50
0
1961
1966
1971
1976
1981
1986
Year
1991
1996
2001
2006
Figure 6.29 Annual per capita paper consumption
USA
Canada
Oceania
Europe
Central America & Caribbean
South America
Asia
Middle East & North Africa
Sub-Saharan Africa
350
kg/person/year
300
250
200
150
100
50
0
1960
1970
1980
1990
Year
2000
2010
Japan
Canada
US
Ireland
Norway
Switzerland
Netherlands
Sweden
UK
Slovenia
Austria
Spain
Denmark
Portugal
France
Finland
Hungary
Italy
Belgium
Estonia
Slovak Republic
Romania
Latvia
Czech Republic
Lithuania
Greece
Poland
Bulgaria
Cyprus
Malta
Paper Recycling Rate (%)
Figure 6.30 Rates of paper recycling
100
90
80
70
60
50
40
30
20
10
0
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
250
Recycled
Non-wood
Pulp Production (Mt/yr)
200
Dissolving
Semi-chemical
Chemical
150
Mechanical
100
50
0
1961
1966
1971
1976
1981
1986
Year
1991
1996
2001
2006
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 chlorinefree (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:
Potential energy production:
Net energy requirement:
• Paper from waste paper:
~ 29 GJ/t
~ 31 GJ/t
-2 GJ/t
~ 20 GJ/t
So, in terms of gross energy requirements,
recycling gives a 30% savings. However, in terms
of net energy use, recycling increases the energy
requirement.
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
Middle East &
Africa 8%
FSU 3%
Latin America
4%
Europe
24%
Rest of Asia
17%
Japan
6%
NAFTA
23%
China
15%
Figure 6.32b: Uses of plastics in Europe
Other
28%
Packaging
37%
Electrical and
Electronic
6%
Automotive
8%
Building &
Construction
21%
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%
Other
19%
Polyurethane
7%
High density
polyethylene
12%
PET
(polyethylene
teraphthalate)
7%
Polystyrene
8%
Polyvinyl
chloride
12%
Polypropylene
18%
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
Urea resin
Feedstock Energy
Polyvinyl chloride
140
Polyvinyl acetate
Process energy
PET
160
Phenol formaldehyde resins
Synthetic rubber
Polyethylene
Polyacrylonitrile
Polystyrene
Polyurethane
Melamine resin
Polycarbonate
Polyacrylate
Epoxy resin
Nylon-6
Nylon-6,6
Energy Input (GJ/tonne)
Figure 6.35 Primary energy inputs to make plastic
180
120
100
80
60
40
20
0
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-theart 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
30
Energy recovery
25
Mechanical recycling
Feedstock recycling
Sent to landfill
28%
Mt per Year
20
20%
15
10
5
0
1995
1997
1999
2001
2003
2005
2007
Year
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
US conventional onshore oil
Canadian conventional onshore oil
Conventional offshore oil
Heavy oils
Canadian tar sands
Energy Use (GJ/tonne oil)
Extraction Refining
Total
1.3
2.9
4.2
2.4
3.0
5.4
3.9
3.0
6.9
2.9
3.0
5.9
12.9
3.0
15.9
Energy Use as a % of
Energy in Products
10.0
12.8
16.4
14.1
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
ELECTRODIALYSIS
retains suspended matter
passes dissolved substances
and water
retains nonionic matter
passes ionic matter
GAS SEPARATION
ULTRAFILTRATION
retains membrane impermeable
gases
passes membrane permeable
gases
retains dissolved matter
passes some macromolecules,
microsolutes, ions, and water
REVERSE OSMOSIS
H
H
H
retains all ions
passes water
M
M
M
COUPLED TRANSPORT
passes carrier complex ions
M+denotes monovalent metal ion
H +denotes hydrogen
DIALYSIS
retains dissolved matter
passes microsolutes and
water
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
Waste Hea t
e1
h3
ICE or
Gas Turbine,
F1
Heat Recovery
1
h1
h2
2
e1 =
h2 = (1-
F1
1)
2F
Useful Heat
1
1
Typical electrical efficiencies: 22-35%
Typical overall efficiencies: 39-54%
overall
=
+(1-
1
)1
2
Figure 6.38b Industrial cogeneration using a steam turbine
Waste Heat
e2
h7
Steam Turbine
h5
4
Heat Recovery
h6
Useful Heat
5
h4
h3
Boiler,
3
h3 = 3F2
e2 = 3 4F2
h4 = (1- 3)F2
h5 = 3(1- 4)F2
h6 = 5(h4+h5)
overall
F2
Typical electrical efficiency: 9-13%
Typical overall efficiency: 61-68%
= (e2+h6)/F2
Figure 6.38c Combined-cycle industrial cogeneration
Waste Heat
e4
e3
h13
Gas Turbine
6=0.29
Steam Turbine
8=0.12
h11
Heat Recovery h12
9=0.51
h10
h9
F3
h8
Boiler,
F4
ha = 7(h8+F4)
e4 = 8h9
h11 = (1- 8)h9
e3 = 5F3
h8 = (1- 6)F3
overall
Useful Heat
7
=0.8
h10 = (1- 7)(h8+F 4)
h12 = 9(h10+h11)
= (e3+e4+h12)/F3+F4)
Typical electrical and overall efficiencies: 30-36% and 60-70%
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
o
Temperature C
150
497 Units
100
• 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
50
Pinch Point
417
Units
1000 Units
Heat load