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Synthesis of Renewable Energy Integrated Combined Heat and Mass Exchange Networks

  • Adeniyi Jide IsafiadeEmail author
  • Michael Short
Original Research Paper
  • 30 Downloads

Abstract

In this paper, a methodology for systematically integrating the synthesis of combined heat, mass, and regeneration exchange networks with solar thermal is presented. The process considered involves the removal of ammonia from ammonia-rich gaseous streams using water-based solvents as the mass separating agent (MSA) and subsequent regeneration of the ammonia-rich MSA stream using steam stripping. A composite superstructure, which comprises the stage-wise superstructure for the synthesis of the heat exchanger network subsystem, primary mass exchanger network subsystem, regeneration subsystem and integrated solar thermal with periodic heat storage, is developed. In order to simplify the modelling of the unpredictable availability of solar thermal energy within the composite superstructure, a multi-periodic synthesis approach is adopted. Sensitivity analysis was performed to establish the price at which solar thermal is favoured over fossil-derived energy as the hot utility source. The economics of the resulting solution is evaluated using net present value, and it was found that, to obtain a positive NPV, the stripping cost in the retrofitted network will have to be as low as possible, or annual operating cost of the non-retrofitted primary mass exchange network will have to be high.

Keywords

Absorption Regeneration Heat exchange network synthesis Mass exchange network synthesis Solar thermal 

Nomenclature

Abbreviations

ACC

annual capital cost

AOC

annual operating cost

CHAMENS

combined heat and mass exchange network synthesis

FBHU

fossil-based hot utility

GHI

global horizontal irradiation

HENS

heat exchange network synthesis

LMCD

logarithmic mean composition difference

LMTD

logarithmic mean temperature difference

MENS

mass exchange network synthesis

MINLP

mixed integer non-linear programming

MSA

mass separating agents

NPV

net present value

TAC

total annual cost

SWS

stage-wise superstructure

Sets

H

hot process streams and utilities

C

cold process streams and utilities

R

rich process streams

S

process lean and external lean streams

INT

superstructure intervals

P

periods of operation

Indices

i

hot process streams and utilities

j

cold process streams and utilities

r

rich process streams

rg

regenerating streams

l

process lean and external lean streams

k

index representing interval, 1, …  … . NOI and temperature location, 1,.....NOI + 1 for HEN superstructure

kk

index representing interval, 1, …  … . NOI and composition location, 1,.....NOI + 1 for primary MEN superstructure

kkk

index representing interval, 1, …  … . NOI and composition location, 1,.....NOI + 1 for stripping column

p

index for operation periods (p = 1, …  … . NOP)

Parameters

a1, a2

solar panel thermal loss coefficient

ACE

area cost index for heat exchangers ($/m2.)

AOCON

annual operating cost of original network ($/y)

HCE

area cost index for primary mass exchangers

HRCE

area cost index for regenerating columns

ACi, j

cost per unit area for heat exchanger (m2)

AFHE

annualization factor for heat exchanger

AFMA

annualization factor for mass (primary) exchanger

AFRC

annualization factor for regenerating column

AFSP

annualization factor for solar panel

AFST

annualization factor for heat storage tank

ACSCi, j

cost per unit area of solar thermal panel (m2)

ACTSi, j

cost per unit volume of heat storage tank (m3)

CFi, j

installation cost for heat exchanger i, j ($)

CFr, l

installation cost for mass exchanger r, l ($)

CFl, rg

installation cost for regenerating column l, rg ($)

Cp

thermal storage tank fluid specific heat capacity (kJ/kg ∙  ° C)

CUCj

cost per unit of cold utility ($/kW ∙ yr)

GHIp

global horizontal irradiation in period p (W/m2)

HUCi

cost per unit of hot utility ($/kW ∙ yr)

Fi, p

heat capacity flowrate of hot process stream and utility in period p (kgs−1)

Fj, p

heat capacity flowrate of cold process stream and utility in period p (kgs−1)

Gr, p

flowrate of rich stream in period p (kgs−1)

Kw

lumped column sizing coefficient (NH3/s ∙ kg)

LSCl

cost per unit of lean stream l (($/y)/(kg/s))

MACr, l

cost per unit mass for mass exchangers ($/kg ∙ y)

N

project life (y)

RACl, rg

cost per unit mass for regenerating column ($/kg ∙ y)

r

interest rate

RSCrg

cost per unit of regenerating stream rg (($/y)/(kg/s))

Tap

ambient temperature for period p (°C)

Tc

solar capture fluid average temperature (°C)

\( {T}_{i,p}^s \)

supply temperature of hot process stream and utility for period p (°C)

\( {T}_{i,p}^t \)

target temperature of hot process stream and utility for period p (°C)

\( {T}_{j,p}^s \)

supply temperature of cold process stream and utility for period p (°C)

\( {T}_{j,p}^t \)

target temperature of cold process stream and utility for period p (°C)

Ui, j

overall heat transfer coefficient between streams i and j (kW/m2 ∙  ° C)

\( {X}_{l,p}^s \)

supply composition of lean (process or external) stream for period p

\( {X}_{l,p}^t \)

target composition of lean (process or external) stream for period p

\( {Y}_{r,p}^s \)

supply composition of rich process stream for period p

\( {Y}_{r,p}^t \)

target composition of rich process stream for period p

\( {Y}_{l,p}^{\ast s} \)

equilibrium supply composition of lean (process or external) stream for period p

\( {Y}_{l,p}^{\ast t} \)

equilibrium target composition of lean (process or external) stream for period p

\( {z}_{rg,p}^s \)

supply composition of regenerating stream for period p

\( {Z}_{rg,p}^t \)

target composition of regenerating stream for period p

DOPp

duration of each period p

NOP

number of periods

ε

lowest possible approach temperature for match i, j, p, k

ω

lowest possible approach composition for match r, l, p, kk

Ωp

upper limit for exchanged heat in match i, j in period p

η0

solar thermal panel efficiency

ρ

density of thermal storage tank fluid (kg/m3)

Binary Variable

yi, j, k

represents the existence of match i, j in stage k in heat exchanger network

zr, l, kk

represents the existence of match r, l in stage kk in mass exchanger network

wl, rg, kkk

represents the existence of match l, rg in stage kkk in regeneration exchanger network

Positive Variables

Ai, j, k

maximum area of heat exchanger for match i, j, k (m)

ASCi, j, k

maximum solar panel area (m)

Qi, j, p, k

heat exchanged between hot stream i and cold stream j in period p and stage k (kW)

dti, j, p, k

approach temperature for match i, j, p, k (°C)

dyr, l, p, kk

approach composition for match r, l, p, kk

Ll, p

flowrate of lean stream in period p (kgs−1)

Vrg, p

flowrate of regenerating stream in period p (kgs−1)

LMCDr, l, p, kk

logarithmic mean composition difference between rich stream r and lean stream l in interval kk and period p

LMCDl, rg, p, kkk

logarithmic mean composition difference between external lean stream l and stripping agent rg in interval kkk and period p

Mr, l, p, kk

mass exchanged between rich stream r and lean stream l in interval kk and period p (kgs−1)

Ml, rg, p, kkk

mass exchanged between external lean stream l and stripping agent rg in interval kkk and period p (kgs−1)

MassAbr, l, kk

maximum column mass for absorber that exchanges mass load in match r, l, kk (kg)

MassRegl, rg, kkk

maximum column mass for stripping column that exchanges mass load in match l, rg, kkk (kg)

NAOCRN

annual operating cost of retrofitted network ($/y)

NACCRN

annual capital cost of retrofitted network ($/y)

ti, p, k

temperature of hot stream i in period p and stage k (°C)

tj, p, k

temperature of cold stream j in period p and stage k (°C)

VTSi, j, k

maximum thermal storage tank volume (m3)

yr, p, kk

composition of rich process stream in interval boundary kk and period p

xl, p, kk

composition of lean (process or external) stream in interval boundary kk and period p

\( {y}_{l,p, kk}^{\ast } \)

equilibrium composition of lean (process or external) stream l in composition interval boundary kk and period p

Notes

Funding Information

This study is supported by the National Research Foundation of South Africa under the incentive funding scheme for rated researchers (Grant number: 85536) and the Research Office of the University of Cape Town, South Africa. The funds are gratefully acknowledged.

Compliance with Ethical Standards

Conflict of Interest

The authors declare that they have no conflict of interest.

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Copyright information

© Springer Nature Singapore Pte Ltd. 2019

Authors and Affiliations

  1. 1.Department of Chemical EngineeringUniversity of Cape TownCape TownSouth Africa
  2. 2.Department of Chemical EngineeringCarnegie Mellon UniversityPittsburghUSA

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