T. Gundersen E&M 01

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Energy & Environment

Special Lecture on Energy & Environment

• Clean Process Technology (Ch. 28 in R. Smith)• Classes of Waste (Process & Utility)• Environmental Impacts from Energy Usage• Energy/Exergy & Component/System Efficiencies• Actions to mitigate Greenhouse Effects (Energy21)• How can TEP4215 Energy & Process (PI) Contribute

Process

EnvironmentEnergy

ProcessIntegration

T. Gundersen E&M 02

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Energy & Environment

Clean Process Technology – Some Ideas(Ref.: Robin Smith, Chemical & Process Integration, Ch. 28)

• Environmental Issues (similar to Heat Integration) are often considered late in the Design Process

• The Result is often “End-of-Pipe” Solutions• Clean Process Technology represents an Opposite

Approach similar to Process Integration thinking: Minimize Waste at Source − Examples:

Choose Reactions Paths that avoid harmful Chemicals being produced as byproducts

Keep harmful Chemicals “inside the loop” by combining producing and consuming Reactions

Closing Processes as in Pulp & Paper

T. Gundersen E&M 03

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Energy & Environment

Sources of Waste from the Process Industry

• Types of Process Waste: Waste Byproducts, Purge Streams, etc.

• Sources of Process Waste: Reactors (byproducts, used catalysts, etc.) Separation & Recycle Systems (inadequate

recovery and recycle of valuable materials) Process Operations (start-up, shutdown, product

changeover, equipment cleaning, etc.)

R S H U R + S : Process Waste

H + U : Utility Waste

T. Gundersen E&M 04

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Energy & Environment

Sources of Waste from the Process Industry

• Types of Utility Waste: Gaseous Combustion Products (CO2, SOx, NOx, Particles) Aqueous Waste from BFW (Boiler FeedWater) Treatment Waste from Water Systems

• Sources of Utility Waste: Hot Utilities (incl. Cogeneration) Cold Utilities and Water Systems

R S H U R + S : Process Waste

H + U : Utility Waste

T. Gundersen E&M 05

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Energy & Environment

Sources of Waste from the Process Industry

• Our Focus in these Lectures: Environmental Impacts from Energy Consumption

• Remember to take a Systems Approach: Local Emissions vs. Global Emissions Producing or importing Electricity?

R S H U R + S : Process Waste

H + U : Utility Waste

T. Gundersen E&M 06

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Energy & Environment

Environmental Impacts from Processesincluding their Use of Energy

• Various Kinds of Waste Material• Heavy Metals• CO and CO2

• NOx and SOx

• CH4 , NH3 and other volatile compounds• Particles (“Particulates”)• VOC (Volatile Organic Compounds)• Heat (or Cooling)• Wastewater• Using scarce Freshwater Resources

T. Gundersen E&M 07

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Energy & Environment

Environmental Design for Atmospheric Emissions(Ref.: Robin Smith, Chemical & Process Integration, Ch. 25)

• Urban Smog (Los Angeles, Mexico City, Lima, Shanghai) Photochemical Reactions VOCs + NOx + O2 O3 (Ozone) + Other

Photochemical Pollutants (Aldehydes, Peroxynitrates, etc.)

• Acid Rain Natural Precipitation is slightly acidic with pH around 5-6

Carbonic acid from dissolved CO2

Sulfuric acids from natural emissions of SOx and H2S Human Activity can reduce pH to 2-4

Mainly caused by emissions of SOx This is a primarily a local environmental problem Can be a regional problem (from UK to Norway)

T. Gundersen E&M 08

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Energy & Environment

Environmental Design for Atmospheric Emissions(Continued)

• Ozone Layer Destruction Lower Levels of the Atmosphere: Ozone is harmful! Upper Levels: Ozone essential; it absorbs ultraviolet light! Destruction is due to Oxides of Nitrogen and Halocarbons

• The Greenhouse Effect CO2 , CH4 and H2O present in low conc. in the atmosphere

Reduces emissivity and reflects some of the heat radiated by Earth. Keeps the Earth warmer − a prerequisite for Life as we know it

This Balance can be disturbed Global Warming Burning Fossil Fuels (increased emission of CO2) Large Scale harvest of Forests (reduced absorption of CO2)

• The largest Volume of Atmospheric Emissions from Process Plants is due to Combustion

T. Gundersen E&M 09

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Energy & Environment

Actions that reduce the Environmental Impacts from Energy Consumption

• Statement: The most “Green” Energy is the Energy that is not used Process Integration increases Energy Efficiency and

results in Energy (in various forms) not being used Investment in Equipment may cause use of Fossil Fuel

based Energy elsewhere (considering LCA)

• More comprehensive List of Actions Use less Energy (vs. “Standard” of Living) Increase Energy Efficiency Increase Process Efficiency Switch between Fossil Fuels Switch from Fossil Fuels to Renewables

T. Gundersen E&M 10

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Energy & Environment

“Energi21” − National Strategy for R&D, Demonstration & Commercialization

− Energy in the 21st Century

• The Vision of Energi21 Norway: Europe’s leading Energy and Environment-

Conscious Nation − from a National Energy Balance to Green Energy Exports

• To realize this Vision: 5 Priority R&D Areas Efficient Use of Energy (Industry/Transport/Buildings) Climate-friendly Power CO2-neutral Heating An Energy System to meet the Needs of the Future Desirable Framework Conditions for R&D

T. Gundersen E&M 11

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Energy & Environment

Energy Consumption (TWh) in Norway by Sector in 2007 (Total: 813.5 PJ)

Industry & Mining

Transportation

Other Sectors

Other Sectors: Private household (20.0%), CommunityConsumption (13.7%) and Fishing/Agriculture (3.6%)

37.3% 35.1%

27.6%

The Course “Energy & Process” makes Sense !!

T(erra) = 1012

T. Gundersen E&M 12

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Energy & Environment

Aluminum

Chemical

Pulp & Paper

Petrochemical

Food Industry

Iron & Steel

Minerals

Wood Ware

Mining

Others

Energy Consumption (TWh) in Norwegian Industry in 2007 (Total: 80.66 TWh)

29.6%

17.6%13.6%

12.0%

Discuss: Primary Application Areas for Process Integration?

T. Gundersen E&M 13

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Energy & Environment

Main Focus in TEP 4215: Efficient Use of Energy

• Saving Energy means Saving the Environment in one or more Ways (CO2, SOx, NOx, Particulates)

• Process Integration provides Methods and Tools to improve Heat Recovery and Heat Integration

• The Result is reduced Energy Consumption• With the current Energy Mix this also means

reduced Emissions from Fossil Fuels• The Systems Approach in Process Integration can

be used also to reduce Waste and other Impacts from the Process Industries

T. Gundersen E&M 14

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Energy & Environment

What we’ve done in TEP 4215Process Integration

• Heat Recovery between Hot and Cold Streams to reduce Energy Consumption in the form of Hot and Cold Utilities

• Heat Integration of Distillation Columns and Evaporators with the “Background Process”

• Use of Heat Pumps to “lift” Thermal Energy (Heat) from below to above the Pinch by using Mechanical Energy (Power or Electricity)

• Combined Heat and Power (Cogeneration) by using Backpressure Turbines and deliver Heat to the Process or District Heating System while producing Power/Electricity

• Process Modifications to improve Scope for Heat Recovery guided by the “Plus/Minus” Principle

T. Gundersen E&M 15

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Energy & Environment

Tools developed in Process Integration

• The Composite Curves Provides Insight and a Graphical Way to establish

Energy Targets Suggests Process Modifications (+/− Principle)

• The Grand Composite Curve Based on the Heat Cascade − a Transshipment Model Optimal Mix of Utilities (including Production) Possible Integration of Reactors Integration of Distillation Columns and Evaporators Potential for and Correct Use of Heat Pumps Combined Heat and Power Considerations

T. Gundersen E&M 16

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Energy & Environment

A brief Discussion about Efficiencies

• Energy vs. Exergy Efficiency Exergy is defined as the Ability to produce Work Exergy screens Energy Types w.r.t. Quality Exergy does not reflect Cost − or better: The Cost

of various Energy Forms does not reflect the 2nd Law

• Component vs. System Efficiency “Local” vs. “Global” Considerations Importing Electricity may improve Plant Efficiency

and Emission Figures (inside Battery Limits) With Process Integration, Systems Thinking and

utilizing Synergies, Component Efficiencies become less Important and System Efficiency improves

T. Gundersen E&M 17

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Energy & Environment

Basic Principle for Combined Cycle Plant

Ref.: Olav Bolland

100%

40%

30%

10%

20%

T. Gundersen E&M 18

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Energy & Environment

Combined Cycle Power Plant

%5.48100

5.48

%5.89100

415.48

E

PE

QP

%57100

57

E

P

Power Production only Heat & Power Production

Ref.: Olav Bolland

T. Gundersen E&M 19

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Energy & Environment

Some Efficiency Calculations• Exergy Content of Heat Q at Temperature T

Ex = Q (1 − T0/T) T0 is “ambient” temperature (25°C or ≅ 298 K)

• Exergy Content of Fuel Includes Chemical Exergy − Difficult !! Often taken to be the Low Heating Value (LHV) More pragmatic: Pure (100%) Exergy

• Exergy Content of Power & Electricity This is Pure Exergy !!

• Calculations on the Blackboard• The Heat Pump “Congregation”

Produce Electricity, “take back” the Heat later !!

T. Gundersen E&M 20

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Energy & Environment

Indicators for CO2 Emissions• Material Production

tons of CO2/tons of Product

• Energy Production tons of CO2/MWh Electricity

• Consider 3 Cases of Power Production Natural Gas (assume pure CH4) based Combined

Cycle Power Plant with an Efficiency of 60% Same as above but Cogeneration of Heat and

Power with a Total Efficiency of 90% State of the art Coal (assume C/H=1) based

Power Plant with an Efficiency of 40%

• Calculations on the Blackboard• Fuel Switching can be Powerful