Heat Integration Potential in Batch Processes Using PinCH 2.0

D. Olsen, R. Kislig and B. WelligLucerne School of Engineering and Architecture, Horw, Switzerland

P. KrummenacherPlanair SA, La Sagne, Switzerland

1. Characteristics of Repeated Single Product Batch Processes

4. Batch Supertargeting Results

Fig. 1: Batch example [1] showing the weekly production cycles diagram and the associated equipmentwise repeat operation period (EROP) time slice model formed due to the overlap of the individual batches as calculated in PinCH 2.0.

• Batch process production cycles are often operated in a repeated and over-lapped manner to maximize production capacity.

• Pieces of equipment can contain mul-tiple streams, e.g. reactor with two non-flowing streams as illustrated by E2.1.

• Within the weekly production cycle, an equipmentwise repeated operation period (EROP) can be identified that consists of time slices (TS) to be used for direct heat integration, not only in the single product batch itself, but also across overlapped batches.

Fig. 4: Optimal ∆Tmin values per Time Slice and associated number of units, minimum total HEN area and minimum cost for the shown Batch Example [1].

• The method combines energy and cost optimiza-tion with the required flexibility for HEN design.

• The target results aid the practicing engineer in making critical decisions when designing the HEN (in addition to the optimized area matrices and key pinch match matrices).

6. References[1] R. Kislig: Batch Supertargeting Analysis - Conventional

Design and Resequence Design, Hochschule Luzern, Master Thesis, 2012.

[2]

P. Jones: Targeting and design of heat exchanger networks under multiple base case operation, PhD Thesis, University of Manchester Institute of Science and Technology (UMIST), U.K., 1991.

[3]

P. Krummenacher: Contribution To The Heat Integration Of Batch Processes (With or Without Heat Storage), Thèse No. 2480, École Polytechnique Fédérale de Lausanne, Switzerland, 2001.

PinCH is funded by the Swiss Federal Office of Energy (SFOE) and the Swiss Private Sector Energy Agency (EnAW).

2. Direct Heat Integration Potential• An increase in the energy efficiency of batch processes can be achieved

through direct heat exchange. • However, heat exchanger network (HEN) design for minimal investment cost is

a challenge due to the time dependency of the streams.

Fig. 2: HEN designs for time slices 1 - 3 assuming separate networks in each time slice (i.e. no reuse of heat exchangers has been accounted for).

3. Batch Supertargeting Optimization

Fig. 3: Simple two time slices example illustrating HEN design for conventional and resequence design type contraints.

• In order to achieve minimum investment cost for batch processes, it is important to reuse heat ex-changers and maximize the common area over all the time slices [2].

• Supertargeting optimization to minimize total cost can be done based on conventional and resequence design constraints [3].

• Supertargeting optimization is applicable to multiple base case operation [3].

• PinCH 3.0 to include support for indirect heat transfer, i.e. heat storage.

2

Resequence DesignConventional Design

1200 m2

1

21100 m2

3

550 m2

4

100 m2

5

120 m2

Total Area: 3070 m2

1200 m22

11100 m2

3450 m2

4550 m2

5100 m2

6

120 m2

Total Area: 3520 m2

600 m2

1

4

1100 m2

3550 m2

120 m2

E1 E2 E3

Total Area: 2370 m2

Time Slice 1

H1

C1C2

1200 m2

2

4

450 m2

1

3400 m2

100 m2

Time Slice 2

Total Area: 2150 m2

H2

C3C4

E1 E2 E3

E1 E2 E3E1 E2 E3

TS 1 TS 2

Separate Design Mode

TS 3

Overview:

Goals: • Batch processes and their time depen-

dent nature provide a unique challenge in achieving optimum heat integration.

• Our goals in developing PinCH 2.0 are to provide practical features and graphical tools that an engineer in the practice can use in such batch process optimization.

Design Method Separate Design Conventional Design Resequence DesignOpt. ∆Tmin TS1 25 25 20.5

TS2 18 18 18TS3 14 14 8TS4 25 25 20.5TS5 18 18 18TS6 14 14 8

Number of Units 40 19 11Total Area [m²] 440 244.8 231.7

Total Cost [kCHF] 475.7 390.7 345.9

Time [h]

B1

E1.1

E1.2

E2.1

E2.2

E3

E4

B2

B3

TS1 TS2 TS3

EROP

ShutdownStartup

E1.1

E2.1

E3

E4

Fixed Single Batch – B1

B1

TS4 TS5 TS6

5. Significance and Future Work