Basic Elements of Pinch Technology

Under the guidance ofMr. Umesh Chandra SharmaChemical Engineering Department

Presented byRajat Kumar SonkarCSJMA12001390208

Contents• What is PINCH TECHNOLOGY ?• Principle of Pinch Technology• Significance of Pinch Technology• Objectives of Pinch Analysis• Traditional vs. Pinch approach• Energy & Water Saving Potential of Pinch Technology• Steps of Pinch Technology Explanation• Areas of Applications of Pinch Technology• Alternatives Of Pinch Technology• Conclusion

What is PINCH TECHNOLOGY ?• The term “Pinch Technology” was introduced by Linnhoff and

Vredeveld in year 1978 to represent a new set of thermodynamically based methods that guarantee minimum energy levels in design of heat exchanger networks.

• Pinch technology is a state of the technique for design of energy efficient processing plants.

• Pinch Technique is used to compute the theoretical minimum utility consumption for a process based on thermal data process stream.

• Pinch point is defined as the temperature where the net deficit or surplus is ‘zero’.

Principle of Pinch Technology

• Pinch Technology is a thermodynamically based method specifically using the First and the Second law of thermodynamics.

• First law of thermodynamics helps to calculate the enthalpy of the various streams in the process.

• Second law of thermodynamics is used to determine the direction of heat flow.

Significance of Pinch Technology

• The three basic significance of pinch technology are – • No external cooling above the pinch temperature• No external heating below the pinch temperature• No heat transfer between the process stream across the pinch

temperature• Violation of any of them will lead to higher energy than theoretical

minimum requirements and will adversely affect the energy efficiency.

Objectives of Pinch Analysis

• To match cold and hot process streams with a network of exchangers so that demands for externally supplied utilities are minimized.

• The prime objective of pinch analysis is to achieve financial savings by better process heat integration .

Traditional vs Pinch approach

Design of Core Process

UtilitySystem

Heat Exchange System

Design of Core Process

Heat Exchange System

UtilitySystem

Target

TargetTarget

Traditional approach

Pinch approach

Potential energy savings in some major industrial sectors

Potential water consumption savings in some major industrial sectors

Brief Outline Of The Process

Identification of Hot and Cold Streams

Find the value of DTmin

Composite Curves

Shifted Composite Curve

Grand Composite Curve

1

2

3

4

5

Identification of Hot and Cold Streams• The first step involves the determination of the various hot and cold

streams present in the process.• The identification of the various streams involves determining:

• The supply temperature of the streams• The temperature to which the streams have to heated/cooled i.e.

the target temperature• The specific heat capacity of the streams and the heat capacity

flow rate• The enthalpy change of each stream

Typical Stream DataStream Number

StreamName

Supply Temp°C

Target Temp°C

Heat Capacity Flow

Kw/°C

EnthalpyChange

Kw1 Feed 60 205 20 2900

2 Reactorout

270 160 18 1980

3 Product 220 70 35 5250

4 Recycle 160 210 50 2500

Find the value of DTmin• DTmin is the minimum temperature difference between the stream

temperature profiles.• A lower value DTmin implies that the temperature difference

between the streams is low and hence a very large area of heat exchanger is required for the heat exchange which increases the capital cost.

• A higher value of DTmin implies that a larger quantity of utility is required for heating/cooling which increases the energy cost.

• Thus we need to choose an optimum value of DTmin for a process.

Typical Value of DTmin for various industries are

Sr. No. Industrial Sector Experience Dtmin value

1 Oil Refining 20-40°C

2 Petrochemical 10-20°C

3 Other Chemical 10-20°C

4 Low Temp. Process 3-5°C

Composite Curves• For composite curve, we first

plot the temperature enthalpy diagrams for all the hot and cold streams. The slope of the curves is CP i.e the heat capacity flow rate of the stream. To draw the hot composite curve we simply add the slopes of the hot streams i.e. the values of CP for all the streams.

The following diagram depicts how a combined composite curve consisting of both curves – the hot composite curve and the cold composite curve – looks like:

Shifted Composite Curve• For this we carry out the following changes to the temperatures of

the hot and cold composite curves:• For hot streams = Tact- Dtmin/2• For cold streams = Tact+ Dtmin/2

• Carrying out the above changes and re-plotting the curves gives us the shifted composite curve.

Grand Composite Curve• The final step of the process is to construct the grand composite

curve.• The curve is constructed by simply subtracting the enthalpies of the

shifted cold and hot composite curves and plotting the enthalpy differences v/s temperature.

• The following is a diagram showing how a grand composite curve looks like

Areas of Applications of Pinch Technology

• Applications (equipment-wise) include:• Heat exchangers• Distillation columns• Evaporators• Refrigeration systems

• In the Indian sector companies like:• IPCL• Reliance• Indian Oil• Hindustan Petroleum

• Some of the international companies are: • Cadbury• British Steel• Shell Oil• Pennzoil• Procter And Gamble

• Applications (industry-wise) include:• Petrochemicals• Petroleum• Bulk chemicals• Pulp and paper• Sugar• Food processing

Alternatives of Pinch Technology• MILP/MINLP Approach, • State-Space Approach, • Genetic Algorithm Approach, • Process Graph Theory Approach,• Super targeting Approach

Conclusion• To summarize pinch technology offers a systematic approach for

saving cost and reducing energy consumption. • The technology helps to cut down utility requirement as well as its

cost. It thus provides an alternative to use of various other energy resources such as heating oil or other fuels which are used as utilities and are scarce.

• Although the initial cost for carrying out the analysis and implementing the changes may be high but the long run benefit is more than sufficient to cover it.

References• R K Sinnot Coulson & Richardson Chemical Engineering Design 4 Edition, R K

Sinnot, pg111-126.• Cost Minimization And Energy Recovery Using Pinch Technology, Dr. Akansha

Mahajan.• Using Pinch Analysis to Optimize the Heat Exchanger Network of a

Regenerative Rankine Cycle for an Existing Modern Nuclear PowerPlant, Stephanie Barnes

• Introduction to Pinch Technology, Linnhoff March www. linnhoffmarch.com

Thank You