PINCH TECHNOLOGY
Pinch technology is one of the most successful and generally useful techniques developed by Bodo Linnhoff. The term derives from the fact that in a plot of the system temperatures versus the heat transferred, a pinch usually occurs between the hot stream and cold stream curves. It has been shown that the pinch represents a distinct thermodynamic break in the system and heat should not be transferred across the pinch for minimum energy requirements Linnhoff and Townsend, Townsend, !"#$%. &pplying the pinch principle leads to promising, accurate results. These levels of temperature, temperature, which for the hot Pinch technology will convert the plant's heat(e)changer streams to lines called the hot and cold composite curves and cold composite curves are a means of separating the plant into two parts, are called streams above and below the pinch. This separation is important to indicate to the process engineer whether the locations of heaters and coolers are correct or not. *rong positions cause energy losses. Process heat integration is a method to ma)imi+e the utility usage by matching hot and cold streams in a plant to achieve heat transfer. This will lead to a substantial reduction in the energy requirements of the plant. In recent years much work has been done on developing methods for investigating energy integration and the efficient design of heat e)changer networks.
Choosing the Right Stream
The reboiler reboiler and condenser condenser of the distillation distillation column will not be selected selected because because of the controllability and the product purity. Integrating the reboiler and condenser of the distillation column will affect the purity of the product inside it which is lower. The pump also did not consider in this process since the pump in did process did not contribute big value energy and have a very small of temperature differences in the outlet and inlet of the pump which is differences in decimal places. Thus, all the heating and cooling that involve in process other than distillation column and pump will be design based on the stream e)tracted from the simulation.
Determination of hot and cold streams
The hot and cold streams were identified from the process flow diagram. ach stream starts from a supply temperature, Ts and is heated or cooled to a target temperature, Tt. -treams from distillation column units condensers reboilers% were not considered because integration will affect the controllability and product purity of the distillation columns. This is because the distillation columns and its equipments operate in a vacuum pressure. Table /.$ below, summari+es streams with all its corresponding conditions.
-tream
Type
0o. 8(# #(!/ !#(; !8(!#
3ot 3ot 6old 6old
1low rate
3eat
m6p
Tin
Tout
7
kg2s%
capacity
k*25c%
5c%
5c%
k*%
/89 $#9 !;9 /9
$#9 ;9 $;9 !;9
#".!9 ";8.:" (:"$.99 (;<;.$9
9.:# $.$; $.8$ $.8$
k42kg.5c% $.98 9."" !.#; :.!< !.#! :."$ !.8/ :.8! Table = -tream 6ondition
Determination of Tmin
The ne)t step is crucial, which is to determine the minimum approach temperature difference, >Tmin. The optimum value chosen for >Tmin is e)tremely important because it will determine the si+e of the heat e)changer in a network. This is because, when the value of >Tmin decreases, the utility consumption and cost will also decrease. 3owever the heat recovery, the e)pense of the equipment si+e and capital cost will increase. Table ".$= >T min for ?espective Industries 0o ! $ / :
Industrial -ector @il ?efining Petrochemical 6hemical Low Temperature
)perience >T min values o6% $9(:9 !9($9 !9($9 /(; *source (www.cheresources.com)
This dimethylether plant falls under the petrochemical and chemical industry. Thus, the range for >Tmin should be between !9 56 to $9 56. 1rom to this range, >Tmin of !9A6 was selected
because the lower the value of >Tmin the lower the utility consumption and cost will be. *ith this >Tmin, the interval temperature of each supply and target temperature can be determined.
Determination of interval temerat!re for so!rce and target temerat!re
The method used is the Problem Table &lgorithm ethod, as named by Linnhoff and 1lower. It is used to determine the pinch temperatures and the minimum utility requirements -innott, $99<%. Interval temperature is needed to determine the pinch temperature. Interval temperature can be calculated using the equations below= 3ot streams= Tinterval C Tactual D E Tmin 6old streams= Tinterval C Tactual F E Tmin The use of the interval temperature rather than the actual temperatures allows the minimum temperature difference, >Tmin C !9 56 to be taken into account for the problem being considered.
-tream 0o
! stream 8 to #% $ stream # to !/% / stream !# to ;% : stream !8(!#%
&verage heat 6apacity k*2o6%
&ctual
3eat Load, k*%
Interval
-ource Temperature o6%
Target Temperature o6%
-ource Temperature o6%
Target Temperature o6%
9.""
/89
$#9
/<;
$8;
#".!9
:.!<
$#9
;9
$<;
:;
":8.:"
:."$
!;9
$;9
!:;
$:;
(:"$.9
:.8!
/9
!;9
$;
!:;
(;<;.9
Pinch Calc!lations "
3ot -tream
6old
!
m6pk*2 A6% 9.""
$
/
:.!<
:."$
: :.8!
7 k*%
/89A6 GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG/:9 A6 $#9 A6GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG$;9 A6
:9/.;
!#9 A6 GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG!;9 A6
($9
<9 A6 GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG/9A6
!#./$;
;9 A6 GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG$9 A6
(:".;/
#ig!re $" Temerat!re Interval Diagram A 89.1
#".! Pinch
Pinch
B
a
b
-76 COLD
HOT
!/.!
UTILIT
UTILITY
Y C
73C;$."
-66
D 41.6
#ig!re %" The Cascade Diagram
76C:!.<
&bove Pinch H.U
1
2
52.9
89.1
915.
;$."
#".!
/;9
3
4
492
565.
;<;.$
inimum number of e)changers,0 min,a C : Below Pinch 2 41.6
C.U
:!.<
41.6
inimum number of e)changers,0 min,a C ! #ig!re &" Calc!lation of 'inim!m N!m(er of E)changers
&bove Pinch
-tream
!
m6pk*2 A6% 9.""
$
/
:.!<
:."$
: :.8!
/89A6 GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG/:9 A6 $#9 A6GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG$;9 A6 !#9 A6 GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG!;9 A6 <9 A6 GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG/9A6 25 37 Q1=89. 1
1
28 2
28
25
Q2=3
15
2
15 19 Q3=56 3
3 17
60
Q4=5
30
4 15
Below Pinch
-tream
!
m6pk*2 A6% 9.""
$
/
:.!<
:."$
: :.8!
<9 A6 GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG/9A6 ;9 A6 GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG$9 A6 60 5 50
Q5=4
5 20
#ig!re *" Design of Heat E)changer Net+or, -(ove and .elo+ Pinch
Therefore,
!. inimum amount of heat must be supplied from 3ot Htilities is ;$."9 k* $. inimum amount of heat must be ?emoved by 6old Htilities is :!.<9 k*. /. Pinch Point at interval, >T C /9 o6. a% 6old -tream, T C /9.9o6 b% 3ot -tream, TC <9.9o6
CO'P-RISON .E#ORE -ND -#TER INTEGR-TION •
Total Energ/ Can .e Saved
By implementing the heat integration, the heat removal from condenser can be utili+ed to heat up the reactant mi)ture. Below is the comparison before and after implementing the heat integration. Table != inimum 3eating and 6ooling ?equirement Before and &fter 3eat Integration Htility
Before integration k*%
&fter integration k*%
!9;8.9
:!.<
!9:<.;"
;$."
$!9/.;"
":.;
inimum cooling requirement inimum heating requirement Total
Therefore, percentage% energy hot can be saved = C
1046.59 −52.9 1046.59
x 100
C":."
Percentage% energy cold can be saved = C
1057 − 41.6 1057
x 100
C"<.!
CONCL0SION
&s a conclusion, the choosen of minimum temperature is affected the cost of utilities hot and cold% and cost of heat e)changer in the network. If value of differences in temperature is lower the value of minimum temperature choosen, it will reduce energy requirement and make heat
e)changer more e)pensive which is lower operating cost but increase in fi)ed cost. Pinch also can reduced the energy required to cool or heating in any process.
RE#ERENCES
!. Jundersen, T., and 0aess, L. !"##%. 6omp. and 6hem. ng., The synthesis of cost optimal heat-exchanger networks D an industrial review of the state of the art.
$. Pinch Technology, http=22www.cheresources.com2pinchtech:.shtml , 9$ &pril $9!!%. /. Pinch Technology, http=22www.uic(che.org2pinch2streamGinput.php , 9/ &pril $9!!%. :. -innot, ?.K $99;% 6hemical ngineering esign, Coulson & ichar!son Chemical "ngineering. # r! "!ition. $olume %
