Heat Exchanger Technology and Process Integration

1
Heat Exchanger Technology and Process
Integration
Presentation at STEM Meeting
Lieke Wang

• Division of Heat Transfer
• Lund Institute of Technology
• Box 118, 22100 Lund
• Sweden

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Outlines

• Introduction to process integration.
• Different heat exchanger technologies.
• Achievements in the project.
• Future works.
• Conclusion.

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Introduction

• Total processing system

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Introduction

• Procedures of plant design and construction.
• Conceptual design
• Detailed engineering design
• Procurement
• Fabrication
• Commissioning

5
Optimization methods

• Three major approaches
• Heuristics not used separately any more.
• Algorithmic not widely adapted in industries so
  far.
• Pinch technology widely used at present.
• Pinch technology provides the optimization among
  heat recovery, external energy and exchanger area.

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Pinch technology

• Composite curves
• The composite curves allow the designer to
  predict hot and cold utility targets ahead of
  design, to understand driving forces for heat
  transfer, and to locate the heat recovery Pinch.

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Different heat exchanger technologies

• Heat transfer operation can be enhanced through
• Compact heat exchangers.
• Heat transfer enhancement in conventional heat
  exchangers.
• These technologies influence plant in three
  fundamental ways.
• Reduced unit capital cost
• Reduced cost associated with size, weight and
  piping reduction.
• Reduced plant complexity.

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Different heat exchanger technologies

• These technologies are often ignored in process
  industries.
• Process integration technology is restricted to
  traditional heat exchangers.
• Process engineering softwares policy of linking
  shell-and-tube heat exchangers to process
  simulators.
• It is too late to consider compact heat
  exchangers after the overall network structure is
  established.
• Different heat exchanger technologies have to be
  considered at the very outset of process design.

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Use of compact heat exchangers

• Plant structure is hence changed by use of
  compact heat exchangers through
• DTMIN
• Capital cost

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Multi-stream heat exchangers

• One shell-and-tube heat exchanger

• Three pass shell-and-tube heat exchangers

• One plate heat exchanger

• One plate heat exchanger

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Multi-stream heat exchangers

• Three-stream plate heat exchangers with counter
  flow arrangement. styrene

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Multi-stream heat exchangers

• Shell-and-tube heat exchangers

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Multi-stream heat exchangers

• Multi-stream plate heat exchangers

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Multi-stream heat exchangers

• Multi-stream plate heat exchangers

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Multi-stream heat exchangers

• Multi-stream plate-fin heat exchangers (up to 12
  streams)

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Multi-stream heat exchangers

• It is also needed from the point view of process
  integration.

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Heat Transfer Enhancement Technology

• Types of techniques (shell-and-tube heat
  exchangers)
• Tube inserts.
• Modified tube geometries.
• Enhanced tube surfaces.
• Modified baffle arrangements (helical type).
• Others.

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Heat Transfer Enhancement Technology

• Benifits
• Low heat transfer area for grassroots design.
• Additional exchanger unit may be avoided for
  retrofit design.
• Reduce the fouling formation.
• Reduce maldistribution (both shell and tube
  sides).
• Others.

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What should we do about different heat exchanger
techniques in process integration?

• Procedure for considering different heat
  exchanger techniques should be established at the
  target stage.
• Consideration of pressure drops.
• Plate pattern
• Cost estimation.
• Possibility of multi-stream heat exchangers.
• Others

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Summary of our works

• The works can be divided into three categories
• Heat exchanger networks.
• Individual heat exchangers.
• Industrial case study.
• It should be pointed out that the work in
  individual heat exchangers is to make individual
  heat exchangers consistent with the requirement
  from the networks.

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Works in system

• More accurate heat transfer area estimation with
  the consideration of pressure drops at the target
  stage.
• Design of multi-stream plate-fin heat exchangers
  and multi-stream plate heat exchangers in the
  optimization of heat exchanger networks.
• Flexibility analysis at the aim of less surface
  area, corresponding to less fouling factors.

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Works in individual exchangers

• An improved approach to the design of plate heat
  exchangers.
• Thermal performance analysis of multi-stream
  plate heat exchangers.
• Application of heat transfer enhancement in the
  retrofit of shell-and-tube heat exchangers.

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Works in Case Study

• A case study was carried out at Stora Nymölla AB,
  a pulp and paper mill.
• A heat recovery system at the pulp mill is
  analyzed in detail using the pinch technology.
• Different heat exchanger techniques have been
  considered in the optimization of the heat
  recovery system at the mill.

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Works in case study

• Retrofit advice is suggested to make the system
  more energy-efficient
• The hot and cold utility consumption in the
  existing network can be reduced by 44.5 and
  17.4, respectively.
• Two new plate heat exchangers are required, and
  the excessive energy consumption can be avoided.
• The pay back period is about 12.5 months.

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Publications

• The results have been disseminated widely
• International conferences
• 3rd Baltic Heat Transfer Conference (1999,
  Poland)
• ECOS2000 (2000, the Netherlands)
• 34th National Heat Transfer Conference (2000,
  USA)
• 35th National Heat Transfer Conference (2001,
  USA)
• 3rd International conference on compact heat
  exchangers and enhance technology for the process
  industries (2001, Switzerland)

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Publications

• International journals
• Applied Thermal Engineering (2001)
• Heat Transfer Engineering (2001)
• International Journal of Heat Exchangers (2001)
• These publications show that our work is highly
  appreciated with credits.

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Co-operations

• The work has co-operations extensively with other
  institutes, industrial companies, etc.
• Linköping University (project co-operation)
• Helsinki University of Technology (visiting
  student)
• Norwegian Institute of Technology (visiting
  student)
• Stora Nymölla AB (case study)
• Alfa Laval Lund AB (heat exchanger techniques)

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Future works

• Future possible works include
• To extend full optimization in design of heat
  exchanger networks.
• Consideration of two-phase flow heat exchangers
  in the optimization of heat exchanger networks.
• Adaption of the pinch technology and development
  of complementary calculation algorithms for
  advanced heat and power facilities.
• Combination with mathematics algorithms.
• More industrial case studies.
• Others

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Conclusions

• Use of advanced heat exchanger techniques in
  process integration has the following advantages
• Improved energy efficiency
• Reduced capital expenditure
• Reduced plant complexity
• Improved plant safety
• More work is necessary to understand these
  technologies, and to encourage more people to
  adopt these in process integration.