Techno-economic feasibility of soprtion chillers coupled to

Hanning Li1, Yasmine Ammar 2 3, Yaodong Wang2, Vinol Rego 3, David Swailes 3, Vida Sharifi 1, Tony Roskilly 2

1 Department of Chemical and Biological Engineering, University of Sheffield, United Kingdom

2 Swan Centre for Energy Research, Newcastle University, Newcastle Upon Tyne, UK

3 School of Mechanical and Systems Engineering, Newcastle University, United Kingdom

PRO-TEM Special Session on Thermal Energy Management: Energy System & Efficiency Improvement

Techno-economic feasibility of sorption chillers coupled to humidification dehumidification

desalination process for low grade heat recovery

OVERVIEW

• Aims and objectives

• Case Study: Low-grade heat (LGH) source

• Description of humification-dehumidification

process

• Process design

• Results and discussions

• Conclusions

Aims and Objectives

• Investigation of HDAC process (Humidification –

Dehumification coupled with an Absorption

Chiller) for desalination

• Utilising LGH with temperature between 50 °C

and 90 °C

• Process description and two designs

• Evaluation: capital and operational costs

Case Study: Low-grade heat source

• LGH: temperature 50 °C – 90 °C

• An integrated Pulp and board mill producing over

150,000 tonnes of product from virgin timber was

chosen.

• It is equipped with a CHP plant which supplies the

plant with all its steam and most of its electricity

requirements.

• 20 million litres of water at temperature in excess

of 35°C is discharged into the sea daily.

Case Study: Low-grade heat source

• Air & exhaust gas with temperatures 60 - 110 °C;

mass flow rate 150 kg/s

• Effluent water with temperature of 47 °C; mass

flow rate 86 kg/s.

• The large quantity of LGH located on the coast.

• Cycle tempo software developed by Delft University

was used for simulation of water production in the

HD process.

Description of HD process

Tlow = 25.00 K

Thigh = 13.58 K

H,trans = 6433.5 kW

Thigh = 3.15 K

Tlow = 2.45 K

H,trans = 31225.90 kW

Tlow = 15.00 K

Thigh = 5.00 K

H,trans = 4290.29 kW

1.013 20.00

2.258

1717

1.013 44.42

60.000

1616

1.013 -5.00

60.000

1515

1.013 20.00

19.158

1414

1.013 58.00

21.416

1313

1.013 15.00

19.000

1212

1.013 17.45

35.584

1111

1.013 61.15

38.000

1010

1.013 70.00

150.000

99

1.013 90.00

150.000

66

1.013 42.00

38.000

44

1.013 30.00

87.000

33

1.013 47.00

87.00022

1.013 15.00

38.000

11

18

17

16

15

14

13

12

9

7

6

5

4

32

H

1

H

product water sink

Air sinkReturn to the sea

Hot air sink

Hot water source

Air source

Cooling water sink

Cooling water source

Hot air source

Feed seawater source

Hot water sink

Heat exchanger 1

Heat exchanger 2

Humidifier

Dehumidifier

p T

m

m = Mass flow [kg/s]

p = Pressure [bar]

T = Temperature [°C]

H,trans = Transmitted heat f low [kW]

Tlow = Low end temp. diff. [K]

Thigh = High end temp. diff. [K]

� = m

Figure 1: Humification-Dehumidification (HD) process schematic representation

Description of the process

Figure 2 Flow diagram of HDAC-SAV (Humidification-Dehumidification coupled with absorption chiller – Superheated Ammonia Vapour)

Description of the process

Figure 3 Flow diagram of HDAC-APC (Humidification-Dehumidification coupled with absorption chiller - Ammonia Phase Change)

Results and discussions

Cooling method SAV APC

Temperature (°C)

absorber 22 22

Generator -5 -5

Thermal exchange (kW)

absorber 42534.9 1588.2

generator 39250.0 1581.4

economizer 39842.1 1137.4

cooling energy 6433.5 1005.5

condenser 1770.5

mass flow rates (kg/s)

ammonia vapour 53.15 0.91

ammonia-rich solution 652.69 8.95

ammonia-poor solution 599.54 8.03

Table 1 Energy and mass balances in two systems

Type Pall Ring

Material Stainless steel

Nominal size (mm) 50

Bed weight (kg/m3) 385

Area (m2/m3) 115

Percentage of void (%) 96

Packing factor (m-1) 89

Table 2: Characteristics of the packing material (Data from Table 14-7 b of [13])

Results and discussions

HEX1 HEX2

Fluid at the shell side Water Air

Fluid at the tube shell Water Water

Baffle spacing 1.5 1

Tube pitch 0.00693 0.00625

Tube inside diameter

(m)

0.005 0.005

Tube outside

diameter (m)

0.00525 0.00525

Shell thickness (m) 0.009525 0.00925

Shell inner diameter

(m)

0.06 0.05

Length (m) 7.4 7.8

Tube number 30 50

Table 3: Dimensions of heat exchangers HEX1 and HEX2 [14]

Results and discussions

economizer in

HDAC-SAV

economizer in

HDAC-APC

Fluid at the shell side NH3-poor soln NH3-poor soln

Fluid at the tube side NH3-rich soln NH3-rich soln

Baffle spacing (m) 4 0.25

Tube pitch (m) 0.095 0.045

Tube inside diameter (m) 0.05 0.0254

Tube thickness (m) 0.003 0.002

Shell inner diameter (m) 4.00 0.72

Length (m) 20 15

Tube number 300 30

Tube pass 4 4

Table 4: Dimensions of economizer designed for two systems

Results and discussions

Table 5: Dimensions of generator designed for two systems

generator in

HDAC-SAV

generator in

HDAC-APC

Fluid at the shell side Water flue gas

Fluid at the tube side two phase flow two phase flow

Baffle spacing (m) 25 15

Tube pitch (m) 0.095 0.09

Tube inside diameter (m) 0.05 0.05

Tube thickness (m) 0.003 0.003

Shell inner diameter (m) 0.63 0.36

Length (m) 50 20

Tube number 100 40

Tube pass 1 1

Results and discussions

Results and discussions

absorber in

HDAC-SAV

absorber in

HDAC-APC

Fluid at the shell side Water water

Fluid at the tube side two phase flow two phase flow

Baffle spacing (m) 11.6 3

Tube pitch (m) 0.093 0.09

Tube inside diameter (m) 0.05 0.05

Tube thickness (m) 0.003 0.003

Shell inner diameter (m) 1.41 0.35

Length (m) 35 20

Tube number 500 30

Tube pass 1 1

Table 6: Dimensions of absorber designed for two systems

Results and discussions

Condenser evaporator

Fluid at the shell side Water water

Fluid at the tube side two phase flow two phase flow

Baffle spacing (m) 8 5

Tube pitch (m) 0.049 0.049

Tube inside diameter (m) 0.025 0.025

Tube thickness (m) 0.002 0.002

Shell inner diameter (m) 0.18 0.11

Length (m) 10 4

Tube number 25 10

Tube pass 1 1

Table 7: Dimensions of condenser and evaporator designed for HDAC-APC system

Results and discussions

SAV APC

Fan power(kW) 21.40 21.40

Compression (kW) 8800.64 2.91

Ammonia solution pump(kW) 431.89 4.39

Other pumps (kW) 0.05 0.05

Total(kW) 9200 28.75

Table 8 Power consumption in two systems

Results and discussions

Humidifier ($) 143357.70 143357.70

Dehumidifier ($) 183157.30 183157.30

subtotal ($) 326515.00 326515.00

exchange rate (€-$) 1.39 1.39

subtotal (€) 234902.88 234902.88

HEX1 (€) 1581.02 1581.02

HEX2 (€) 2350.06 2350.06

economizer(€) 199883.17 21808.44

absorber(€) 221496.90 19442.18

generator(€) 85849.37 23479.14

condensor(€) 6988.22

evaporatorr(€) 1896.95

Total (uninstalled) equipment cost(€) 746063.40 312448.89

Installed factor † 1.46 1.46

Installation cost (€) 1089252.56 456175.38

Table 9 estimated capital and operational costs

Conclusions • This study investigates the feasibility of low grade heat from

process industries as a source for thermal desalination processes via a Humidification Dehumidification process coupled to an absorption chiller (HDAC) with water-ammonia as a working fluid.

• two absorption cooling systems are compared: superheated ammonia vapour (SAV) and ammonia phase change (APC) processes.

• It is found that HDAC+APC process is a better solution with a payback period of less than 10 years and an increased energy saving.

• It is found that HDAC+SAV is not a solution since both capital and operational costs are very high.

Thank you !