Chemical Engineering in Water Infrastructure...
Transcript of Chemical Engineering in Water Infrastructure...
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
Chemical Engineering Series III -Chemical Engineering in Water Infrastructure Projects
Harry LeeSenior Engineer, Arup31 October 2014
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
IntroductionWater InfrastructureWater Scarcity and ResilienceSummary and Thoughts
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
3 What is Chemical Engineering?
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
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• a branch of engineering that applies the natural sciences and life sciences together with mathematics and economics to produce, transform, transport and allow proper use of chemicals, materials and energy
• emerged upon the development of unit operations and focus on several key principles:
- chemical reaction engineering (reactors)
- separation
- process design, control and safety
- plant design and economics
What is Chemical Engineering?
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Obje
ctiv
es
• throughput rate
• process yield
• product purityC
on
stra
ints
• capital costs
• operation and maintenance costs
• available space
• safety concerns
• environmental impact - projected effluents and emissions
• waste production
Oth
er F
acto
rs
• reliability
• redundancy
• flexibility
• anticipated feedstock variability
• allowable product variability
Process Design - Considerations
design of processes for desired physical/chemical/biological
transformation of materials
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• material and energy balances
• thermodynamics
- change in enthalpy: endothermic vs exothermic processes
- phase change(s)
• reaction and reactor
- reaction kinetics: zeroth-/first-/second-order reactions
- batch vs continuous processes
- reactor configurations- continuous stirred-tank reactor (CSTR)- plug flow reactor (PFR)
Chemical Engineering Terminologies (1/3)
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• fluid mechanics (pipe hydraulics)
• heat and mass transfer
• process dynamics and control
• plant/process design and economics
• process safety
- hazard and operability (HAZOP) study
- hazard assessment
- quantitative risk assessment (QRA)
Chemical Engineering Terminologies (2/3)
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• process integration
- emphasise the unity of the process
- consider the interactions among different unit operations from the outset, rather than optimising them separately
• process intensification
- a set of often radically innovative principles (paradigm shift) in process and equipment design
Chemical Engineering Terminologies (3/3)
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HONG KONG
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Block Diagram
• simple diagrams of rectangles and lines indicating major material (or energy) flows
Process Design - Documentation (1/3)
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Process Flow Diagram (PFD)
• more complex diagrams of major unit operations and flow lines
• sometimes include material and/or energy balances
• showing typical or design flowrates, stream compositions, stream/ equipment pressures and temperatures
Process Design - Documentation (2/3)
Example PFD on fluid catalytic cracking
[http://chemengineering.wikispaces.com]
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HONG KONG
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Piping and Instrumentation Diagram (P&ID)
• valving along with instrument locations and process control schemes
• pipelines with piping class and pipe size
Specifications
• written design requirements of all major equipment items
Process Design - Documentation (3/3)
Example P&ID on membrane desalination process
[http://www.projenex.com/]
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
IntroductionWater InfrastructureWater Scarcity and ResilienceSummary and Thoughts
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
13 Water Supplies Department (Fresh Water)
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
14 Drainage Services Department (Sewage Treatment)
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
15 Design with Water (Arup)
Fundamental water &
sanitation services
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HONG KONG
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Chem
ical
Engin
eeri
ng • throughput rate
• process yield
• product purityW
ater
Tre
atm
ent
• demand forecast of supply zone(s), peaking factors
• raw water quality
• contaminant(s) of concern
• wastage
• drinking water standard
• (residuals quality)
Was
tew
ater
Tre
atm
ent • sewage flow
projections, peaking factors
• load projections
• bypass
• discharge standard
• (residuals quality and recovery)
Translation of Process Design Objectives for Water Infrastructure Projects
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
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• reaction
- contact tanks (chemicals addition, aeration)
- digestion
• separation - mostly solid/liquid
- coarse/fine screening
- (coagulation/flocculation and) sedimentation
- filtration (and adsorption)
- thickening/dewatering
• others
- energy/resource recovery (eg CHP, micro-turbine)
- deodourisation
Common Unit Operations for Water Infrastructure (1/2)
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
18 Common Unit Operations for Water Infrastructure (2/2)
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
19 Case Study - HATS Stage 2A, Overview
Photomontage of SCISTW after HATS Stage 2A Upgrading Works
© A
rup
HATS Layout Plan
© A
rup
SCISTW prior to HATS Stage 2A Upgrading Works
© A
rup
Harbour Area Treatment Scheme (HATS) Stage 2A
A centralised sewage collection and treatment system for urbanised areas on both sides of Victoria Harbour.
The most important sewage infrastructure in Hong Kong serving ultimately over 5 million population.
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• flow and load projections
• system capacity and process design
• process evaluation (liquid + sludge) and value management
• constraints identification and layout design
• reference design and specifications
• contract packaging and procurement
• construction supervision
• testing and commissioning
Case Study - HATS Stage 2A, Chemical Engineering Inputs
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HONG KONG
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Case Study - HATS Stage 2A, Layout Design
New facility under
HATS 2A
Existing facilities
New Main Pumping Station
and Interconnection Tunnel
New flocculation and
sedimentation Tanks
Odour Control Enhancements
(including covers to all
sedimentation tanks, channels
and flow chambers)
New Sludge Treatment and
Disposal Facilities
Disinfection facilities
New Control and Expert
System
New Effluent Tunnel and Flow
Chambers
Ancillary Upgrading and
Improvement Works
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
22 Case Study - HATS Stage 2A, On-going Construction
September 2014
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HONG KONG
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Obje
ctiv
es
• throughput rate
• process yield
• product purityC
on
stra
ints
• capital costs
• operation and maintenance costs
• available space
• safety concerns
• environmental impact - projected effluents and emissions
• waste production
Oth
er F
acto
rs
• reliability
• redundancy
• flexibility
• anticipated feedstock variability
• allowable product variability
Chemical Engineering for Water Infrastructures (1/2)
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HONG KONG
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• HAZOP study
• environmental study
• chemicals storage and handling
- occupational safety and health
- dangerous goods
• process optimisation and operation management
- energy efficiency/recovery
- chemicals consumption
- asset management
• many other involvements (to be explored)
Chemical Engineering for Water Infrastructures (2/2)
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
IntroductionWater InfrastructureWater Scarcity and ResilienceSummary and Thoughts
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
26 Design with Water (Arup)
Too much water?
Too little water?
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HONG KONG
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• climate change
• diminishing available fresh water resources
• population growth
• water-energy-foodnexus
• watershed management and cooperation (politics)
Challenges
Water-Energy-Food Nexus [IChemE]
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HONG KONG
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Total Water Management (TWM) in Hong Kong 2008
water demand management
• public education on water conservation
• promote water saving features
• active leakage control
• sea water for toilet flushing
water supply management
• protection of water resources
• water reclamation
• new water resources (sea water desalination)
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HONG KONG
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Chem
ical
Engin
eeri
ng • throughput rate
• process yield
• product purityD
esal
inat
ion
• demand forecast of supply zone(s) - as augmentation
• recoveries through pre-treatment, desalination and post-treatment; function of feed water qualities
• concentrate (brine) discharge
• product water standard(s)
• (residuals quality)
Wat
er R
ecla
mat
ion
• reclaimed water application(s) and demand
• effluent quality - load projections
• return of wastage to inlet of STW/ public sewer
• reclaimed water standard(s), usage-specific
Translation of Process Design Objectives for Desalination and Water Reclamation Projects
[Wiki]
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HONG KONG
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• separation: removing salt from water
• energy is provided through
- thermal
- mechanical
- electrical
Desalination - Fundamentals
feed water fresh water salt+
ener
gy
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Desalination - Classification
desalination
thermal
heat addition
steamMSF / MED / HDH / MD /
TVC
solarsolar stills /
solar collectors
heat removal freezing
mechanical
MVC
RO
electrical ED / EDR
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• 182MLD desalter, MSF technology
- 15 acres (6.07ha) in 6 production units
- once the largest desalter in the World
- intermittent operation 1975-1982
• site selection
- near Pearl River estuary, clearer and less salty sea water
- proximity to Tai Lam Chung Reservoir
• closed down in 1982
- adequate rainfall, public opposition, high fuel price, committed DJ water
Lok On Pai Desalter (1/2)
[WSD / Wiki / HK Reporter]
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HONG KONG
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Lok On Pai Desalter (2/2)
[Lok On Pai Desalting Plant, Water Supplies Department (HKU Library)]
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HONG KONG
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From Thermal to Membrane (1/2) -Process Intensification
[ GWI / DesalData.com / roplant.org ]
• less energy-intensive: no heating or phase changes
• dedicated research & development in membrane science and technology
• continuous process development / optimisation
• competitive membrane prices
• dimensional standardisation
• other market factors
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
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• pressure exchangers (work exchangers)
- directly transfer pressure from the brine to the feed
• turbine systems (Pelton wheel or turbocharger systems)
- convert potential energy from the brine to mechanical energy either supplied to the SWRO high pressure pump as auxiliary power supply or directly to the feed
From Thermal to Membrane (2/2) -Energy Recovery
Dual Work Exchange Energy
Recovery (DWEER) supplied by
FlowserveIsobaric PX supplied by ERI
Pelton Wheel
Turbo Charger Francis Turbine
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• 240m3/day capacity
• 3×3 configuration
- 3 pre-treatment- submerged UF- pressurised UF
- dual media filter
- 3 RO membrane brands
• process optimisation
• post-treatment study
• cost estimation
Hong Kong Pilot Desalination Plant (1/2) - Unit Operations and Process Configuration
[WSD Pilot Plant Study, Executive Summary]
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Hong Kong Pilot Desalination Plant (2/2)
Tuen Mun (2004-2005)
• estuary water (Pearl River)
• considerable seasonal variations in
wet season
• generally less saline
Ap Lei Chau (2006-2007)
• oceanic water (South China Sea)
• relatively stable and consistent
water quality year-round
• relatively more saline
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
38 From very sophisticated system…
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
39… to system that meets the basic need of people in developing regions.
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HONG KONG
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• site selection
• source water quality characterisation
• environmental study, pilot study
• process design and configuration, energy consideration
- intake and pre-treatment
- SWRO/BWRO array - staging and pass(es), modelling
- post-treatment
- water chemistry and chemical dosing
- waste and brine management
• life-cycle costing (CAPEX and OPEX)
Chemical Engineering for Water Resilience (1/4) Planning and Design
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• testing and commissioning
• plant utilisation
• (unit) production cost
• (product) water quality compliance
• process control and automation
• system reliability and diagnosis
• improvement works and prioritisation
• knowledge transfer and operator on-the-job training
Chemical Engineering for Water Resilience (2/4) O&M Strategy
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• H3BO3H2BO3+ HBO3
2+ BO33+
- 4-8mg/L (typical sea water)
- 0.3mg/L (WHO1993)
- 0.5mg/L (WHO2004)
• implications to SWRO
- non-ionic species in normal pH range
- maximum 80-90% removal in first-pass
• solutions
- blending with catchment/DJ water (technical limitation)
- first-pass RO alkalisation (precipitation and/or scaling)
- partial/full second-pass RO ($$$)
Chemical Engineering for Water Resilience (3/4) Boron Mitigation Study
[Huehmer et al (2006) Boron Mitigation Strategies in Seawater Desalination]
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Chemical Engineering for Water Resilience (4/4) The Chemical Engineer | Issue 804, June 2008
“During [the Lanarca plant’s] eight years of operation, we followed a defined plant
operation strategy involving four main steps: optimisation, standardisation,
stabilisation, and innovation… In each step, distinct chemical engineering
principles can be used to ensure that the plant performs optimally.”
“…faced with a substantial growth in the desalination industry… action must be
taken by IChemE and the chemeng community to grasp this opportunity and
meet the demand with a supply of well-educated and skilled engineers.”
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• a dependable source
• effective approach on overall water efficiency with dual benefits
- reduce fresh water demand
- reduce effluent discharge to environment
• public acceptance
- Singapore (NEWater, indirect potable reuse)
- California (aquifer recharge, indirect potable reuse)
- Windhoek, Namibia (direct potable reuse)
- Hong Kong (non-potable uses)
Water Reclamation - General Perspective
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HONG KONG
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[Modified from Takashi Asano, “Water from (waste)water – the dependable water resource”, 2001 Stockholm Water Prize Laureate Lecture]
Urban Water Usage and Quality Profile
1) different starting points and end points
2) different process designs and technologies
3) paradigm shift: wastewater = used water
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HONG KONG
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the first tertiary STW in Hong Kong
• within a country park
• 500m above sea level
• within water gathering ground of Shek Pik Reservoir
reclaimed water as pilot scheme and education (100-150m3/day)
• toilet flushing
• controlled landscape irrigation
treatment technology
• tertiary treatment (SBR + media filter) and disinfection (UV + chlorination)
Reclaimed water uses within NPSTW
© A
rup
Ngong Ping Sewage Treatment Works (NPSTW)
© A
rup
t
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
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What do you think about large-scale applications of Reclaimed Water (RW) in HK?
Water Reclamation Demonstration Scheme in North District
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HONG KONG
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• holistic water strategy and thinking
- across the entire water cycle
- fresh water + used water
• next available water source
- ascending life-cycle costs
- match quality with usage
• impact on existing infrastructure(s) and environment
- not only water but also energy/power infrastructures
- centralised vs decentralised approaches
- desal: brine/waste discharge, energy/chemical consumption
- water reclamation: potential risks on “closing the water loop”
How shall the alternative water treatment processes be applied? (1/2)
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How shall the alternative water treatment processes be applied? (2/2)
water demand management
• public education on water conservation
• promote water saving features
• active leakage control
• sea water for toilet flushing
water supply management
• protection of water resources
• water reclamation
• new water resources (sea water desalination)
compatible?
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
IntroductionWater InfrastructureWater Scarcity and ResilienceSummary and Thoughts
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
51
1) process maturity: technology advancement over time, market creation, value-adding
• research and development - product, process, service
• proof-of-concept design
• bench-scale
• pilot-scale
• demonstration
• full-scale / commercialisation
2) physical-size: spatial consideration, scale-of-economy
• house-hold
• building-/block-level
• development-level
• district-level
• municipal-/city-level
• portable/mobile units
Scale Approach - Two Dimensions
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• chemical: process system(s), unit operations, instrumentation & control - steady-state, conversion, economic potential
• civil: structures, building, transportation, site development -risks, uncertainty
• mechanical: materials, mechanics, energy - machinery and tools
• electrical: power supply, [process] control, computer programming, [tele-]communication - electricity, electronics
• …environmental, geotechnics, coastal/maritime, hydrology…
• collaboration is the key
Different Disciplines and Focuses
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“Here [in Singapore], water is an issue of life and death. That's always been the message.”
Chew Men Leong, Chief Executive, PUB
Macao Recycled Water Development Plan (2013-2022)• target of 10% of total water
consumption by 2022• price of recycled water: 85% of tap
water
Maritime Administration (CP) and Working Group for the
Promotion of a Water-Saving Society, Macau SAR
The Chinese characters below embedded the relationship of water and politics, precisely:
治水 - Water management水治 - Water politics
Professor Yun Zu-whan, Dept of Environmental
Engineering, Korea University
The Wider Perspective - Water Governance
Channel NewsAsia, 30 July 2012 Keynote speech, the 4th IWA-ASPIRE Conference and Exhibition, Tokyo, 2-6
October 2011
My Blog, Financial Secretary Office, 30 March 2014
“Hong Kong… should not be over-reliant on Dongjiang water, but should bear the responsibility to explore other new water sources, to prepare for the challenges of water supply in the future.”
John Tsang, GBM, JP, Financial Secretary, HKSAR
Government
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• resource recovery
- sludge, MSW, organic (food) waste
• cleaner production
- waste minimisation, life-cycle analysis, eco-design
• advanced/sustainable materials
- nanotechnology, (bio-)composites
• mining, minerals, energy and utility
- from fossils to renewables
• food, beverage, pharmaceutical
Chemical Engineering - Beyond Water Infrastructures
香港公開大學THE OPEN UNIVERSITY OF
HONG KONG
Chemical Engineering Series III -Chemical Engineering in Water Infrastructure Projects
Harry LeeSenior Engineer, Arup31 October 2014