HEAT INTEGRATION Analysis 6. Data extraction - IqTMA-UVa

HEAT INTEGRATION 

Analysis 

6. Data extraction 

Heat Integration – UVa | Analysis 06. Data extraction 1

Outline 

Data extraction 

Required data 

Rules and guides (1 to 5) 

Process modification 

Plus/minus principle 


Data extraction 

To pull out data from the PFD and include it into the problem 

General principles: 

it's about disconnecting the existing solution (in order to reconnect it) 

to extract only requirements 

don't extract mandatory features: leave it as they are 

extract heat (and cold) that can actually be used by other streams 

Poor data extraction can lead to two extremes: 

thinking that process is at its optimum (if maintaining excessive features) 

over-estimating the room for improvement (if extracting too much) 


Required information/data 

As a minimum: Problem Table 

Supply and target temperatures 

Stream heating and cooling data: enthalpies and/or mCps 

Information on existing/planned utility system 

Information on costs: 

Energy (utilities) 

Equipment 

Heat exchangers material, pressures, type... 

Utility system devices 

General and background information on the process 


Rules - Guides (1) 

Doesn't extract / doesn't include in the problem: 

Mandatory parts / parts that cant' be changed 

e.g.: Using quenching steam generation in a reactor 

This heat cannot be used in other way 

True utility streams 

(utility that can be replaced by other) 

Quenching (steam generation) 

Cold shots for reactor hot spots control 

Steam in a shift reactor (to enhance the shift process) 

Steam injection for steam distillation (different from direct steam 

to reboil the column - only heat transfer) 



Doesn't extract / include in the problem: 

Linked or chained Energy flows 

Reaction (most cases) 

Compression / expansion ΔH can't be integrated 



Don't maintain unnecessary / too detailed features 

Extend (conceptual) streams as much as possible (energy streams are not 

material streams) 

NO 

YES 

T1 T2 dH T1 T2 dH 

------------------- ------------------- 

35.0 45.5 +191 35.0 130.0 +1720 

120.0 55.0 -191 120.0 55.0 -191 

45.5 91.5 +832 210.0 65.5 -832 

210.0 65.5 -832 ------------------- 

91.5 130.0 +697 

------------------- 

Long no-linear streams can be linearized by segments for calculation 

purposes, but conceptual stream is one. Linearization is just a calculation trick 

Correct, if possible up-down-up temperatures (heating-cooling-heating) 

T1 T2 dH T1 T2 dH 

-------------------- ------------------- 

35.0 150.0 +80 35.0 130.0 +66.1 

150.0 180.0 +20.9 ------------------- 

180.0 130.0 -34.8 

-------------------- 

NO 

YES 



Look at hidden (direct) heat exchange 

Mixing streams 

Injecting streams (e.g.: process water) 

Heating/cooling opportunities are lost 

Heat exchange is been condemned to this configuration (no mandatory) 

Can involve heat transfer across the pinch 

Calculating targets with/without mixing assess extraction or not 


Mixing calculation (1) 

[Approximations: constant mCp, no mixing effects, no phase change] 

From mCp : 

mC P1 T 3 −T 1 =−mC P2 T 3 −T 2 

T 3 = mC P1T 1 mC P2 T 2 

= 428,6 K 

mC P1 mC P2 

Duty 1 = mC P1 T 3 −T 1 =−10286 kW 

Duty 2 = mC P2 T 3 −T 2 = 10286 kW 

mC P1 = mC P3 −mC P2 = 90 kW K 

Duty 2 = mC P2 T 3 −T 2 = 12000 kW =−Duty 1 

T 1 = T 3 − Duty 1 

mC P1 

= 316.7 K 

Duty 1 = mC P1 T 3 −T 1 = −12000 kW 

Valid for absolute or relative (ºC or ºF) temperature 


Mixing calculation (2) 

[Approximations: constant mCp, no mixing effects, no phase change] 

From enthalpies: 

T REF = T 2 H 1,rel = H 1 −H 2 = 1400 kJ 

kg , H 2,rel = 0 kJ 

kg 

C P1 = 

H 1,rel 1400 kJ /kg 

= = 4.667 kJ 

T 1 −T 2 300 K 

kg K 

mC P1 = m˙ 

1 ∗C P1 = 1 kg s 4.667 kJ 

kg K = 4.667 kW K 

Duty 1 = mC P1 T 3 −T 1 = 4.667 kW 400 K −600 K = −933.3 kW 

K 

Duty 2 = −Duty 1 = 933.3 kW 

Just a rough approximation 



Extract/approximate non-linear streams the safe side 

SAFE 

DANGEROUS 

DANGEROUS 

SAFE 

Hot streams hotter / Cold streams colder than approximations 


Process modification 

Changing the material and energy balances to reduce 

requirements in utility / equipment 

Hard and soft / flexible and rigid constraints. 

P/T vaporization/condensation 

T of streams to storage 

Column reboiler/condenser P/T 

Process modification possibilities 

Distillation column operating pressure 

Feed vaporization pressure 

Pump-around flow rates 

Reactor conversion / recycle 


Plus-minus principle 1 

Identify/characterize changes in PFD 

(operation conditions) that improve energy 

performance 

Good modifications: 

Those that decreases hot utility: 

Increasing hot stream duty above the pinch 

Decreasing cold stream duty above the pinch 

Those that decreases cold utility: 

Decreasing hot stream duty below the pinch 

Increasing cold stream duty bellow the pinch 


Plus-minus principle 2 

Also changing Ts 

Changes of T confined to one side of the pinch 

have no effects on energy targets 

Changes of T across the pinch can have effects 

on energy targets (if shift duty across to) 

Shift hot stream duty from below to above the 

pinch / Shift cold stream duty from below to 

below the pinch 

As a general rule: made hot streams hotter and 

cold streams colder 

Can shift duty the right way 

Widen ΔT between curves/improve driving forces

HEAT INTEGRATION Analysis 6. Data extraction - IqTMA-UVa

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