The pilot
plant, combining thermal treatment of municipal solid waste (MSW) with cement
production, was developed by GIC in collaboration with the Chemical Engineering
Department of the Hong Kong University of Science and Technology (HKUST). The pilot demonstration was funded by
the Innovation and Technology Fund under the University-Industry Collaboration
Programme. The CCPP consists of a
MRRF at the front-end followed by a patented thermal process for integrated treatment
of the MSW.
Before
the plant was built, the GIC submitted its Specified Process (SP) licence
application to the EPD under the Section
14 of the Air Pollution Control Ordinance. The first licence was granted on 25
November 2003 and was renewed in 2005.
According to the licence’s conditions, the CCPP could only be in
operation for a cumulative duration of 16 weeks (maximum) over the licensing
period.
The
CCPP was installed within the GICP at Tap Shek Kok by February 2005 and commissioning trials were
undertaken in April and July/August 2005 in order to demonstrate its
performance to EPD according to the licensing conditions. Continuous operation of the plant was
started in early October 2005 and completed in December 2005 (for a cumulative period
of 11 weeks). No more than 24
tonnes of MSW were treated per day during the pilot demonstration of the
CCPP. Figure 2.1a shows the
layout of the GICP and the location of CCPP. Figure 2.1b shows the detailed layout
of the CCPP.
During
the operation of pilot plant, the GIC and HKUST obtained satisfactory results
and sufficient design and operational data on the Co-Combustion
technology. All MSW delivered to
the site was treated and no MSW is currently stored on-site. All the Co-Combustion residues
(including bottom ash and fly ash) were securely packed in labelled sealed bags
and stored in the covered waste reception hall of the MRRF building.
An
air quality monitoring programme was commenced in December 2004 and continued
throughout the pilot demonstration of the CCPP until one month after the
completion of the trials. The Hong
Kong Productivity Council was employed as the independent consultant for
monitoring of flue gas emissions and ambient air quality at the site.
Monitoring equipment was installed in the stack of
the CCPP for the continuous monitoring of Total Organic Carbon (TOC), Hydrogen
Chloride (HCl), Hydrogen Fluoride (HF), Sulphur
Dioxide (SO2), Nitrogen Oxides (NOx),
Carbon Monoxide (CO) and opacity in the flue gas emissions during the operation
of the CCPP.
Two off-site air quality monitoring stations were
established in Butterfly Estate and
Monitoring
results show that the operation of the CCPP did not cause adverse air quality
impact to the identified ASRs. The
results (including the flue gas emission and ambient air quality measured at
the off-site monitoring stations) can be found on the GIC’s
web page at http://www.gii.com.hk/eng/coco_main.htm.
2.2.1
The Need of the Project
The CCPP
was designed as a pilot demonstration process and had the following objectives:
·
to
demonstrate that the Co-Combustion plant could meet EPD’s
Best Practical Means for Incinerators (Municipal Waste Incineration) (BPM 12/1
(08)); and
·
to
obtain engineering data to refine the design of the Co-Combustion Process.
The
pilot demonstration has fulfilled its objectives and the CCPP was closed down
on 17 December 2005. It is
necessary to demolish the whole pilot plant so that the Project Site could be
released for the operation and future development of the GICP. The residues attached to the wall of the
process equipment and units will be removed prior to reuse/disposal. It facilitates better materials recovery
and recycling as the equipment and steel structure can be reused overseas or
recycled locally.
Without
this Project, the equipment, plant and buildings will be left on site and have
to be regularly maintained by GIC to ensure their structural integrity. The residues of the CCPP will continue
be stored on site. In the
long-term, there is a potential of release of the residues due to degradation
of the storage bags/containers.
Most of the plant and equipment for the materials recovery facilities
are still in good serviceable conditions and can be reused for other waste
management facilities. If the CCPP
is not demolished, the conditions of the equipment will be deteriorated and
hence reduce the reuse opportunity of the equipment. This Project will not only enable
the reuse of the materials recovery equipment, and minimise the long-term
environmental risk of storage of residues on site but also will release the
Project Site for operation and future development of the GICP.
2.2.2
Structures to be Demolished
The CCPP
will be demolished and all structures, plant and equipment, foundations and
footing will be dismantled and removed from the site. The site area will be restored into an
open area for operations and development.
The
structures to be demolished including their sizes and heights are shown in Figures
2.2a to 2.2c.
2.2.3
Consideration of Alternative Demolition
& Cleaning Methods
All
equipments and buildings of the CCPP are asbestos-free. Reusable equipments, such as materials
sorting equipments, will be sold to second hand equipment vendors for reuse in
other similar plants. The
decommissioning works will begin by dismantling the process equipment into
segments and disconnecting/removal of main process components. All equipment segments and pipes will
then be cleaned ([1])
in a designated area within
the MRRF building prior to removal from the site for recycle or disposal.
Various
dismantling/demolition methods have been considered and were compared in terms
of engineering feasibility, potential environmental impacts and cost
implication with reference to the Buildings Department’s Code of Practice for Demolition of Buildings (2004) and other
overseas projects ([2])
([3]).
The assessment of alternative demolition methods are presented in Table 2.2a.
After
the process equipments and structures been dismantled and demolished, a
cleaning process will be carried out to allow recycling of the scrap metals and
to minimise the potential environmental impacts associated with the disposal of
the non-recyclable waste at landfills.
Various cleaning methods (1) have been considered and are
summarised in Table 2.2b.
Table 2.2a Comparison
of Potential Dismantling/ Demolition Methods for
the CCPP
|
Method No. |
Description |
Principles/ Procedures |
Engineering Feasibility |
Potential Environmental
Impacts |
Cost Implication |
|
1 |
Loosing the flanges, cutting & lifting |
Dismantling the steel structures by loosing the
nuts and bolts and flanges, or cutting the structure using mechanical,
thermal or laser saw and then lift from top to the ground |
It is the most common method for dismantling steel
structures. Simple equipment will
be required (eg electrical or hydraulically powered
hand held tools). The structures
can be dismantled with care and hence minimise the potential release of the
Co-Combustion residues to the environment. Both ends of the structures will be
sealed immediately after dismantling to contain the residues inside the
structure. |
Electrical or hydraulically powered hand held tools
will be used and the potential for air and noise impacts will be
minimal. As the structures can be
dismantled with care and hence minimise the potential release of the
Co-Combustion residues to the environment. |
Low |
|
2 |
Top down methods |
Breaking away the structure by jack hammer,
percussive or pneumatic hammer |
This method is mostly used for concrete structures. |
Potential release of Co-Combustion residues that
remain in the process lines of the CCPP to the environment, which may cause
adverse environmental impacts. |
Low |
|
3 |
Hydraulic crusher with long boom |
Breaking the structure using a machine mounted
hydraulic crusher with long arm extension |
The hydraulic crusher can be operated from the
ground outside the building or adjacent to the structures. |
Potential release of Co-Combustion residues that
remain in the process lines of the CCPP to the environment, which may cause
adverse environmental impacts. |
Medium |
|
4 |
Wrecking ball |
Destruction by impact of steel ball
suspended from a crane |
Suitable for dilapidated buildings, silos
and other industrial facilities; requires substantial clear space and demands
high level skill operators and well-maintained equipment. As the dismantled plant and equipment
will be deformed, it will be difficult to decontaminate the equipment. It is therefore considered that this
method is not appropriate. |
Potential release of Co-Combustion
residues that remain in the process lines of the CCPP to the environment,
which may cause adverse environmental impacts. |
Medium |
|
5 |
Implosion |
Use of explosives |
Applicable for concrete structure but
not suitable for incinerator/process equipments. |
Potential of dispersion of building
debris into adjoining land during blasting and could cause significant dust,
noise and vibration problems. Potential
release of Co-Combustion residues that remain in the process lines of the
CCPP to the environment, which may cause adverse environmental impacts. |
High |
|
6 |
Drilling |
Coring, drilling and cutting by stitch drilling |
This is suitable for concrete structures but not
for thermal treatment facilities or process equipment. With respect to the nature of the
structures (ie steel structures and processing
equipment) of the CCPP, this method is not suitable. |
Potential release of Co-Combustion residues that
remain in the process lines of the CCPP to the environment, which may cause
adverse environmental impacts. |
Medium |
|
7 |
Non explosive demolition
agent (NEDA) |
Use of static demolition agent to generate an expansive
pressure to crack and break concrete and stone |
Not applicable to slabs and walls. |
Low vibration, noise and dust impacts. |
High |
|
8 |
Thermal lance |
Use of intense heat by fusion of metal |
Involves very high temperature up to 2,000 to 4,000°C
and therefore requires special precautionary measures and care. |
Low vibration, noise and dust impacts. |
High |
|
9 |
Water jet |
Jetting of water at high pressure |
Requires protection of person and properties from
high pressure water. With respect
to the nature of the structures (ie steel
structures and processing equipment) of the CCPP, this method is not
suitable. |
Large amount of wastewater with slurry of concrete
debris and aggregate will be generated.
|
Medium |
Table 2.2b Comparison
of Potential Cleaning Methods for Process Equipments and Structures
|
Method No. |
Description |
Principles/
Procedures |
Advantage |
Disadvantage |
|
A |
Manual wet wiping and scrubbing |
Manual wiping and scrubbing by workers |
· Suitable for small scale
decontaminations · Suitable for low-hazard potential
buildings and equipments · Low cost |
· Labour intensive · Requires protection of person and
properties from potential contaminated environment |
|
B |
Vacuum cleaning |
Make use of vacuum cleaner |
· Require simple skills and equipments |
· Not suitable for fastened materials |
|
C |
Abrasive blasting |
High speed impingement of particles on an object with
the purpose of abrading away surface materials |
· High decontamination capability |
· Containment of abrasive media and debris
generated |
|
D |
Vibratory Decontamination Unit |
A vibrating tub of metal beads that act to abrade particle,
rust, debris etc. from the surfaces; a liquid flushing system is used to wash
debris off of the decontaminated item prior to exit chute. Materials has to
be cut into small pieces (< 30cm in diameter) |
· Sectioned materials will occupy less
volume · Sectional materials will has higher
packaging efficiency |
· Materials have to be cut into small
pieces · Equipment may not be available locally
and it required large area for the decontamination activities · Resulted in a liquid waste for disposal · High cost and not common locally |
|
E |
Chemical flushing |
Dissolve away surface contamination from materials |
· A variety of chemicals are available for
decontamination |
· Resulted in large volume of liquid waste
requiring disposal |
|
F |
Electro-polishing |
Similar to chemical flushing except that an
electrical charge is applied to the items being decontaminated to create an
accelerated corrosion reaction. |
· Removal of surface materials from
metallic items along with the contaminants on their surface |
· Required corrosive liquid as the
electro-polishing medium · Resulted in large volume of liquid waste
for disposal · Only applicable for metallic items · Expensive |
|
G |
Ultrasonic |
Transmitting high-frequency impulses though a liquid
medium on the surface of a contaminated object. |
· Safe operation |
· Materials have to be cut to fit into an
ultrasonic cleaning tank. · Resulted in liquid waste requiring
disposal |
|
H |
High pressure water lance |
High-pressure water spray |
· Require simple equipments |
· Resulted in large volume of contaminated
wastewater requiring treatment prior to disposal |
|
I |
High-temperature water spray system |
Provide cleaning spray and a vacuum collection
system |
· Suitable for removing loose contamination
on concrete and brick surfaces |
· Not applicable for hard or smooth
surface |
2.2.4
Selection of Preferred Demolition and
Cleaning Methods
The selection
of preferred demolition/dismantling methods has made reference to the common
demolition methods in
The
main system and MRRF building of the CCPP are mainly made of steel while the
fire service water tank and pump house are made of concrete. In view of small size of the CCPP, the best
option for dismantling the steel structures (e.g. the
For
the small concrete structures of the fire service water tank and pump house,
breaking away the structure by jack hammer, pneumatic or hydraulic breaker
(i.e. Method 2 – top down method in Table
2.2a) will be used.
Noise
and dust impacts could easily be controlled by practical mitigation measures,
such as low noise equipment, temporary noise barriers and water spraying at the
work area, which are commonly used in
The
process equipments and structures of the Co-Combustion unit will then be
cleaned before recycling or disposal.
With respect to the small scale of the Project, wet wiping (i.e. Method
A in Table 2.2b) and vacuum cleaning
(Method B in Table 2.2b) are
considered to be best suited and most cost effective for the Project. The cleaning will be conducted using a
combination of scraping and vacuum cleaning, followed by wet wiping.
Table 2.2c summarises the procedures.
Table 2.2c Selected
Cleaning Methods
|
|
Scraping/ Vacuum Cleaning
|
Wet Wiping |
|
Procedures |
Residues attached to the wall of the equipments
will be removed by scraping and then collected by vacuum cleaner. |
Damping down the dust inside the ducts and equipment
and then cleaned dust with wet cloths or other appropriate absorbents (eg paper towels).
|
|
Applicable areas / instruments |
Lining inside the rotary kiln, secondary combustion
chambers, gas cooler, bag filter chambers and internal lining of pipes and
ducts. |
Lining inside the rotary kiln, secondary combustion
chambers, gas cooler, bag filter chambers and internal lining of pipes and
ducts. |
|
Secondary
pollution |
Residual dust will be collected by the vacuum
cleaner with HEPA filter so that no dust will be escape to the
atmosphere. Solid wastes will be
stored in sealed bags/containers for reuse/disposal. |
Additional waste will be generated from the clothes
or paper used for the cleaning which will be disposed at a designated
landfill. |
|
Final Disposal / Treatment |
The solid residues are intended to be reused as the
raw materials for cement production.
|
The solid residues will be reused as the raw
materials for cement production.
The cleaning materials will be disposed of at a designated landfill. |
|
Health and Safety of workers |
Full body protection PPE will be provided to the
workers. Potential of disturbing
the dust during the vacuum cleaning process as the dust may escape to the
atmosphere if not properly contained. The effectiveness of the HEPA filter
needs to be checked regularly to ensure no damage. |
Full body protection PPE will be provided to the
workers. Dust generation is
minimised by wetting the surface before wiping. |
To
prevent the unintentional spread of the residues and dust throughout the
process area, the cleaning process will be conducted inside the enclosed
cleaning workshop (i.e. the MRRF building after removal of all equipments, see Section 2.4 for further details) where
forced ventilation will be provided and a slight negative pressured be
maintained. All dust and residues
collected will be packed into labelled polyethylene (PE) bags and will be
reused as the raw materials for cement production.
The
CCPP has been closed down awaiting decommissioning after the completion of the
pilot demonstration. All structures
and the associated foundation, and plant and equipment will be dismantled,
cleaned (where necessary) and removed from the Project Site for reuse,
recycling or disposal. The concrete
slab of the Project Site will be demolished and the site will be backfilled
with a layer of imported clean soil.
The Project Site area will be levelled and landscaped.
Before
the commencement of the demolition works, the Project Site area will be
cordoned off and the access to the works area will be controlled ([4]) ([5])
. The south-east side of the CCPP will be
separated from the existing cement plant by hoarding. Hoarding on the other sides are not
considered necessary as the site is separated from the cement plant by existing
road and drainage channel. Safety
is a prime consideration of the Project.
All required preparation works and general safety measures (including
safety training, awareness programmes and provision of personnel protective
equipments) will be in place before the commencement of the demolition
works. Only authorised persons who
have attended the appropriate safety training would be allowed to work at the
site. Appropriate fire fighting
equipment (eg fire extinguishers) will be provided at
designated locations.
The
overall sequence of demolition works is as follow:
·
Cordon
off the site and erection of hoarding;
·
Disconnect
the utilities (except for the power and water supplies to the fire services
pump room and water tank);
·
Dismantling
and removal of all plant and equipment inside the MRRF building;
·
Dismantling
and removal of the Co-Combustion unit;
·
Cleaning
of the Co-Combustion unit within the enclosed cleaning workshop inside the MRRF
building;
·
Demolition
of the steel structure of the MRRF building;
·
Demolition
of the fires services pump room and water tank;
·
Demolition
of the concrete slab and shallow footing foundation;
·
Backfilling
the site with clean soil;
·
Provision
of surface water drains at the site;
·
Landscaping
the Project site area.
The
whole demolition process will be conducted in a safe manner for the protection
of the workers and to minimise occupational health and safety hazards. Detailed description of the demolition
procedures and safety precautions are discussed in the following sections.
2.3.1
Site Preparation and Access Control
Before
the demolition works, the Project Site will be cordoned off by hoarding or
fencing. Portable barricades will
be used to separate different work zones within the Project Site where
demolition works are in progress.
Suitable metal scaffolding working platform will be erected.
The
access to the Project Site will be controlled by security guards and no
unauthorised persons will be allowed to enter the site. Appropriate warning signboards will be
posted around the perimeter of the Project Site.
2.3.2
Demolition of the Fire Services Water Tank
and Pump House
The
pumps and control panels will be dismantled and sold to scrap metal
recyclers. All water in the water
tank will be drained out. The
concrete wall of the water tank and the pump house will be demolished and
removed by a pneumatic drill mounted backhoe. The concrete structures will be damped
down before and during the demolition works to control dust. The steel reinforcement will be
recovered as far as practicable for recycling. The broken concrete will be disposed of
at the public fill reception facilities.
The load will be properly covered with tarpaulin to minimise dust during
transportation.
2.3.3
Demolition/ Dismantling of the
Co-Combustion Unit
The
duct works of the Co-Combustion unit and the gas cooler will be dismantled by
removal of the bolts or cutting at the joints. The openings (both ends of ducts) will
be immediately sealed with 2 layers of fire retardant polyethylene sheets to prevent
escape of any dust within the duct.
The sheets will be secured with duct tapes. The capped equipment sections/pieces will be lowered
to ground level by crane. Where
necessary, the sections will be cut into smaller size to facilitate cleaning
and transportation.
The
internal wall of the ducts will be properly cleaned with wet cloths or other
suitable absorbents to remove the loose dust deposits. The cleaning materials will be collected
and placed in sealed bags and disposed of at a designated landfill.
The
refractory bricks of the rotary kiln will be removed before lifting the whole
equipment down to the ground. The
refractory bricks will be placed in sealed bags and disposed of at a designated
landfill. The internal wall of the
secondary combustion chambers will be damped down prior to dismantling. The steel frame of the equipment will
then be cut into manageable sections and sold to scrap metal recyclers.
All
filter bags from the dust collector will be removed and placed in sealed bags for
disposal at a designated landfill.
The residual ash will be placed inside a sealed bag. The metal casing of the dust collector
will be properly cleaning using the same procedures for the duct works. The cleaned dust collector will then be
sold as scrap metal.
2.3.4
Dismantling of the MRRF Equipments
The
main power supply to the Project Site will be cut off and all electrical cable
and electrical equipment will be disconnected before the demolition works.
The
materials recovery/recycling equipment (including shredder, conveyor belts,
picking station, magnetic separator, eddy current separator, etc) in the MRRF
building will be disassembled using powered mechanical hand tools and
removed. Most of the plant and equipment
are still in good serviceable conditions and will be sold to other MRRF
operators or second hand equipment vendors.
2.3.5
Demolition of Steel Structure of
After
having dismantled and removed all machinery and equipments, and cleaning of the
Co-Combustion unit, the steel frame structure of the MRRF building will be
demolished in accordance with the Code of Practice for Demolition of
Buildings and generally in the reverse order to that of their
construction. This building was used
for reception sorting of MSW to recover recyclables. There is no potential of concern of land
contamination. The structures will
be demolished progressively from top to bottom. The external non-loading bearing
cladding or any non-structural elements will be removed first. Crane and lifting gear will be used
where possible to support the structural beams and columns whist they are being
cut and lowered to the ground.
Air-powered wrenches, cutting torches, cranes and similar industrial
equipment will be used.
The
steel beams and column will be cut to manageable size to facilitate
transportation. This together with
the metal claddings and scrap metals from the MRRF equipment will be sold to
the scrap metal recyclers.
2.3.6
Demolition of the Foundation and Concrete
Pavement
The
foundation (including the reinforced concrete footing, plinths, with a maximum
depth of 1.5m below ground) of the MRRF building, water tank and Co-Combustion
unit will be demolished by hydraulic breakers and removed. The concrete slab of the Project
Site will then be demolished. The
demolition debris will be further broken down into manageable sizes (<250mm)
and loaded on to dump trucks for transportation to public fill reception facilities. Steel bars will be separated from concrete
for recycling.
The
Project Site will then be backfilled using clean imported soil and landscaped.
2.4
Cleaning of the
Co-Combustion Unit
After all the machinery and equipment were
removed, half of the MRRF building will be converted into a cleaning workshop
for cleaning works. At the entrance to the cleaning area, warning signs
in both Chinese and English will be posted in a prominent location outside the
cleaning workshop throughout the entire period of the decommissioning works.
The cleaning workshop will be provided with forced ventilation and a slight negative pressure would be maintained
within the cleaning workshop during the cleaning works. The exhaust air from the cleaning workshop will
be cleaned using a High Efficiency
Particulate Air (HEPA) filter prior to discharge to the
atmosphere.
The characteristics of the residues were
analysed. The results show that the
physical and chemical compositions of the both residues are similar to those of
the typical clinker raw materials (including pulverised fly ash and bottom ash
from coal fired power station, iron/copper slag). The ingredients of both residues show
the normal chemical substances associated with cement clinker raw feed
materials (calcium carbonate/calcium oxide/calcium salts, alumina, and
iron/copper slag). The residues
contain very low levels of heavy metals and extremely low levels of (in the
order of part per trillion) dioxins (see Table
5.5c). To minimise the exposure
of residues, the workers will wear appropriate PPE (including face mask,
protective gloves, overcoat, and safety boots).
It is expected that a
small quantity of residues (e.g. fly ash, bottom ash) will remain inside the
Co-Combustion unit since the operation of the CCPP was completed. The materials that may still be present
in the gas cooler and dust collector etc. are estimated to be less than 5 m3
in total. The decommissioning
process will start with removal of all residues remaining in the CCPP system by
a vacuum cleaner with a HEPA filter.
Any residues attached within the equipments will be removed by a
combined method of scraping and cleaning.
The internal surfaces of the equipments will be cleaned by wet
wiping.
The scraped lining material will be placed
in sealed bags and disposed of at a designated landfill. The filtered materials, and cloths used
for wet wiping will be packed in sealed bags and disposal of at a designated
landfill. With proper precautionary
measures and handling procedures in place, contamination of steel structure of
the MRRF is not anticipated.
During the entire decommissioning process,
strict industrial hygiene and safety control will be exercised to protect
workers from contact with the residues.
The safety procedures
to be used will include the use of personal protective gear such as chemical
resistant clothing, gloves, boots and/or shoe covers, hard hats, full-face positive pressure respirators equipped
with a cartridge that filter particulate, and other standard
safety equipment.
After
completion of the cleaning process of the Co-Combustion equipment and removal
of the equipment, the cleaning workshop will be vacuum cleaned and wet
wiping. The cleaning materials will be disposed
of at designated landfill.
All
operation of the CCPP ceased on 17 December 2005 after it achieved the Project
objectives as stated in Section 2.3.1. Since that date the facility has been
mothballed pending approval to decommission. The tentative programme for the
demolition, cleaning and disposal works is shown in Table 2.5a.
Table 2.5a Tentative
Programme for the Demolition, Cleaning and Disposal Works of CCPP
|
Tasks |
Tentative Date |
|
Issue of Environmental
Permit by EPD |
June 2009 |
|
Issue of Buildings
Department Permit |
July 2009 |
|
Demolition Works Tendering |
June 2009 |
|
Site Preparation for
Demolition Works |
July 2009 |
|
Demolition and Cleaning |
August to December 2009 |
|
Disposal of Scrap Materials
|
September to December 2009 |
|
Backfilling &
Re-surfacing |
December 2009 |
|
Completion of Demolition
and Decommissioning |
December 2009 |