Techno-economic feasibility of sorption chillers coupled to humidification dehumidification desalination process for low grade heat recovery

Transcription

1 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 Hanning Li 1, Yasmine Ammar 2 3, Yaodong Wang 2, 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

2 OVERVIEW Aims and objectives Case Study: Low-grade heat (LGH) source Description of humification-dehumidification process Process design Results and discussions Conclusions

3 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

4 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.

5 Case Study: Low-grade heat source Air & exhaust gas with temperatures 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.

6 Description of HD process Heat exchanger 2 4 Heat exchanger T low = K T high = 5.00 K H,trans = kw Hot air source H Hot water source 1 H Hot water sink Hot air sink Feed seawater source Return to the sea T high = 3.15 K T low = 2.45 K H,trans = kw Humidifier Air source product water sink Cooling water source Air sink p T Dehumidifier m m = Mass flow [kg/s] Cooling water sink p = Pressure [bar] T = Temperature [ C] H,trans = Transmitted heat flow [kw] T low = Low end temp. diff. [K] T high = High end temp. diff. [K] = m T low = K T high = K H,trans = kw Figure 1: Humification-Dehumidification (HD) process schematic representation

7 Description of the process Figure 2 Flow diagram of HDAC-SAV (Humidification-Dehumidification coupled with absorption chiller Superheated Ammonia Vapour)

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

9 Results and discussions Table 1 Energy and mass balances in two systems Cooling method SAV APC Temperature ( C) absorber Generator -5-5 Thermal exchange (kw) absorber generator economizer cooling energy condenser mass flow rates (kg/s) ammonia vapour ammonia-rich solution ammonia-poor solution

10 Results and discussions Table 2: Characteristics of the packing material (Data from Table 14-7 b of [13]) Type Material Pall Ring Stainless steel Nominal size (mm) 50 Bed weight (kg/m 3 ) 385 Area (m 2 /m 3 ) 115 Percentage of void (%) 96 Packing factor (m -1 ) 89

11 Results and discussions Table 3: Dimensions of heat exchangers HEX1 and HEX2 [14] HEX1 HEX2 Fluid at the shell side Water Air Fluid at the tube shell Water Water Baffle spacing Tube pitch Tube inside diameter (m) Tube outside diameter (m) Shell thickness (m) Shell inner diameter (m) Length (m) Tube number 30 50

12 Results and discussions Table 4: Dimensions of economizer designed for two systems 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) Tube pitch (m) Tube inside diameter (m) Tube thickness (m) Shell inner diameter (m) Length (m) Tube number Tube pass 4 4

13 Results and discussions Table 5: Dimensions of generator designed for two systems generator in generator in HDAC-SAV HDAC-APC Fluid at the shell side Water flue gas Fluid at the tube side two phase flow two phase flow Baffle spacing (m) Tube pitch (m) Tube inside diameter (m) Tube thickness (m) Shell inner diameter (m) Length (m) Tube number Tube pass 1 1

14 Results and discussions Table 6: Dimensions of absorber designed for two systems 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) Tube pitch (m) Tube inside diameter (m) Tube thickness (m) Shell inner diameter (m) Length (m) Tube number Tube pass 1 1

15 Results and discussions Table 7: Dimensions of condenser and evaporator designed for HDAC-APC system 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) Tube inside diameter (m) Tube thickness (m) Shell inner diameter (m) Length (m) 10 4 Tube number Tube pass 1 1

16 Results and discussions Table 8 Power consumption in two systems SAV APC Fan power(kw) Compression (kw) Ammonia solution pump(kw) Other pumps (kw) Total(kW)

17 Results and discussions Table 9 estimated capital and operational costs Humidifier ($) Dehumidifier ($) subtotal ($) exchange rate ( -$) subtotal ( ) HEX1 ( ) HEX2 ( ) economizer( ) absorber( ) generator( ) condensor( ) evaporatorr( ) Total (uninstalled) equipment cost( ) Installed factor Installation cost ( )

18 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.

19 Thank you!