2                                 Consideration of Alternatives

2.1                           Need for the Project

As stated in EPD’s Progress Report on Improving the Air Quality in Hong Kong released in November 2005 ([1]) , the HKSARG and the Guangdong Provincial Government have reached a consensus to reduce, on a best endeavour basis, the emission of four major air pollutants, namely sulphur dioxide (SO2), nitrogen oxides (NOx), respirable suspended particulates (RSP) and volatile organic compounds (VOC).

The Project is proposed by CAPCO in response to the HKSARG’s emissions reduction initiative with regard to SO2 and NOx emissions.  Some further reduction in particulate emissions is also anticipated as a result of SO2 emission control in addition to existing high efficiency ESP.

2.2                           Scenario With or Without Project

The Project is proposed and accepted in the 2005 Financial Plan as an additional measure to ongoing efforts in improving the environmental performance of CAPCO generation plant.  The Project is expected to deliver significant emissions reduction thus contributing to emissions reduction initiative undertaken by the HKSARG and the Pearl River Delta region.  Without the Project, CAPCO’s efforts in contributing to emissions reduction initiatives will undoubtedly be undermined.

2.3                           Consideration of Different Technologies and Emission Control Options

2.3.1                     Introduction

 

There are many different technologies available for the control of NOx and SO2.  The choice of control technologies and their associated equipment would result in different installation, process material supply and the management of any wastes and/or saleable by-products. 

The following sub-sections provide a review of available emission control technology options for the Project, discuss their technological maturity and environmental performance in order to explain the rationale for the base technology selection, LS-FGD and SCR.

2.3.2                     Review of the available NOx emission control technologies

Overview of NOx Emission Control Technologies

The control of NOx emissions from large new thermal power stations has become an important consideration in the design and operation of such plant.  A number of control technologies have been developed to meet the emerging emission control requirements.  Retrofit NOx control for operating plant varies from combustion control technologies to post-combustion flue gas denitrification (de-NOx).

CPB has already implemented combustion control technologies to control its NOx emissions by retrofitting with low NOx burners (LNBs).  This has helped reduce the NOx production from the boilers.  The enhancement technology options available for consideration include:

 

·             Advanced Low NOx Burners (ALNBs)

·             Low NOx Burners (LNBs) or ALNBs with Over Fire Air

·             Gas Reburn or Amine Enhanced Fuel Lean Gas Reburn (AEFLGR)

·             Selective Non-catalytic Reduction (SNCR)

·             Selective Catalytic Reduction (SCR)

Advanced Low NOx Burners (ALNBs)

CPB is equipped with LNBs of an early design, an incremental improvements could be made by installing ALNBs either as part of the normal routine maintenance regime of the station or as part of a specific NOx reduction strategy.  This technology can be used in combination with any of the other available NOx reduction technologies.

LNBs / ALNBs with Over Fire Air

NOx emissions could be further reduced by adding either an Over Fire Air (OFA) or “reburning” technology to the existing LNBs or ALNBs.  Over fire air and boosted over fire air are in-furnace NOx control techniques that stage combustion in the entire furnace.  Typically a portion of the total combustion air is diverted from the main wind box and is injected into the furnace at a level above the top burner row. The intent is to operate the burner zone at a lower stoichiometry than the upper furnace.  Staging combustion in the furnace reduces NOx in two ways.  Firstly, a reducing zone is formed which is not conducive to fuel NOx conversion.  Secondly, furnace staging delays combustion which results in a longer flame and causes heat absorption to occur over a large area of the furnace.  The temperature of the air/fuel/combustion gas mixture is thus reduced, lowering thermal NOx production.  OFA systems provide up to 30% NOx reduction at slightly increased auxiliary power consumption and increased carbon content in ash.  Higher carbon in ash content can be managed.

Gas Reburn or Amine Enhanced Fuel Lean Gas Reburn (AEFLGR)

Reburning is sometimes considered a potentially effective method of reducing NOx emissions levels using secondary natural gas through the inherent staging effect of the reducing and over fire air zones.  The reburning process divides the furnace into three combustion zones.  The main supply of the fuel is burnt under stoichiometry conditions in the lower furnace.  Above the main burners a second fuel such as natural gas is injected often using high pressure recirculated flue gas as a carrier to ensure adequate mixing.  The balance of the combustion air is introduced above both combustion zones in order to complete the combustion process within the furnace.  This remaining air is introduced through openings in the upper furnace wall to the manner typical of over fire air.  NOx reduction typically is 35-45% from an uncontrolled base.  The Gas Reburn system requires additional usage of a supplementary fuel such as natural gas. 

AEFLGR is a combination of natural gas reburn and SNCR with urea as the reagent. The method features minimal use of natural gas at approximately 7% of the heat input.  The effectiveness may approach 50%, but the technology may not be sufficiently tested in large coal-fired plants.

Selective Non-Catalytic Reduction (SNCR)

NOx emissions in the flue gas are converted into elemental nitrogen and water by injecting a nitrogen-based chemical reagent, most commonly urea (NH2CONH2) or ammonia (NH3; either anhydrous or aqueous).  The chemical reactions, in a simplified form, are as follows.

 

2NO + NH2CONH2 + 1/2 O2           à

2N2 + CO2 + 2H2O

NOx + NH3 + O2 + H2O + (H2)                à

N2 + H2O

Because the highest NOx reduction is achieved at temperatures between 870 and 1,200°C, the reagent is introduced at the top and back-pass of the boiler. Multiple injection locations may be required, especially in case of cycling units; different injection locations are used as the unit operates at a reduced load.

SNCR is a proven technology applied in some installations worldwide.  This technology has generally been applied to units of around 350MW and less, however application has extended to larger generating units of the size similar to CPB.  The typical removal efficiency is 30-40%.  In the case of SNCR the ammonia slip may be a more important issue than for SCR but can be managed.

Selective Catalytic Reduction (SCR)

SCR is similar to SNCR in that it uses ammonia injection in the flue gas to convert NOx emissions to elemental nitrogen and water.  The key difference between SCR and SNCR is the presence in SCR systems of a catalyst, which accelerates the chemical reactions.  The catalyst is needed because SCR systems operate at much lower temperatures when compared with SNCR system.  Typical temperatures for SCR are 340 to 380°C, compared with 870 to 1,200°C for SNCR.  Different types of SCR catalyst are available in the market.  The catalyst active surface is typically metal, ceramic or fibre reinforced.  The catalysts are usually made of heavy metal oxides, consisting of the base material TiO2 and active components vanadium, tungsten, molybdenum, copper and chromium.  In most cases, V2O5 is used with a small amount of WO3 and SiO2.  As these catalysts are not chemically modified in the process, their service life is generally very long.  Rejuvenation of catalysts is only required after 4 to 6 years of use.  The rejuvenation process usually involves the removal of solid particles on the catalysts by vacuum cleaner, washing of the catalysts in acid baths and drying of the washed catalysts.  The solid particles removed generally consist of ash particles and therefore can be disposed of in a similar manner.  The wash water generated will be separately treated to the required standards by neutralisation before discharge and is not expected to affect the existing wastewater effluents of CPB.  Relevant requirements under the Water Pollution Control Ordinance (WPCO) and Waste Disposal Ordinance (WDO) should be met for the treatment and disposal of waste and wastewater arising from the catalyst rejuvenation process.

The SCR process is a post-combustion NOx control technology that removes the NOx from the flue gas exiting the boiler.  When the flue gas passes upstream of the SCR catalyst reactor, the NOx in the flue gas reacts with the ammonia gas (a reagent) and is reduced to N2 and water vapour.  No solid or liquid by-products will be generated from this process.

The ammonia gas will be generated from an urea to ammonia conversion system to be installed at the CPB, thus avoid bulk anhydrous ammonia storage on site.  Up to 40,000 tonnes of urea will be used per year.  When urea reacts with water under a heated environment, it hydrolyses to ammonia, carbon dioxide and water.  There are also other urea to ammonia conversion technologies available, e.g. thermal decomposition.  No solid or liquid wastes will be generated from the conversion process.

A limited amount of solid waste, in the form of spent catalyst, will be generated from the SCR process.  Common industry practice is to recycle spent catalysts with original supplier(s) or to rejuvenate them on-site.  If the spent catalyst cannot be recycled by the overseas suppliers or has reached a depleted stage, it can be disposed of at the Chemical Waste Treatment Centre (CWTC) or at the SENT Landfill after stabilisation if required.  With proper recycling and disposal management of spent catalysts, potential environmental impacts of spent catalysts on the existing and future waste management facilities in Hong Kong will be minimal.

The typical NOx removal efficiency of SCR is 80%.  When compared with SNCR, there would be a slight increase in auxiliary power consumption while ammonia slip can be more easily controlled within acceptable limit because of the presence of catalysts.

Summary of the Option Evaluation for NOx Emission Control Technologies

Several NOx emission control technologies have been reviewed and some of the NOx reduction technology integrating the existing combustion technologies with added modifications. The elements of such reduction technologies are combined, taking into account characteristics of the particular power plant and its fuel.  ALNBs and LNBs/ALNBs with OFA can reduce the NOx emissions by 30%, they can also be used in combination with SNCR and SCR.  Combining technologies together may result in the use of less ammonia reagent and less catalyst.  Table 2.1 summarises the main features of the control technologies discussed above, final NOx control facility will be subject to design optimisation. 

Table 2.1         Summary of Considered NOx Control Technology Options

Control Technology

Typical NOx Reduction Efficiency

Environmental Considerations

Other Comments

Advanced Low NOx Burners (ALNBs)

 

20%

 

 

Low NOx Burners (LNBs) or ALNBs with Over Fire Air (OFA)

30-50% reduction in addition to present LNBs

Increased auxiliary power consumption and increased carbon content in ash (thus reduce the re-use potential of ash) but can be managed

 

 

Gas Reburn or Amine Enhanced Fuel Lean Gas Reburn (AEFLGR)

 

Up to 50%

 

AEFLGR may not been sufficiently tested in large coal-fired plants

Selective Non-Catalytic Reduction (SNCR)

 

30-40%

Ammonia slip that can be managed to avoid adverse effects on the quality of ash and hence its re-use potential

 

More experience in 350MW, application now extended to larger generating units

Selective Catalytic Reduction (SCR)

80%

Ammonia slip that can be managed to avoid adverse effects on the quality of ash and hence its re-use potential

 

Proper management of spent catalyst required

 

A smaller SCR with OFA may also achieve up to 80% NOx reduction efficiency.

 

The summary in Table 2.1 indicates that none of the NOx control measures considered would present environmental considerations that prohibit their implementation for CPB. Each of the technologies would be capable of providing air quality improvement in terms of NOx emissions, either individually or in combination.

For the purpose of this EIA Study, the environmental considerations of different NOx control options were considered and the most conservative process is selected for detailed assessment with respect to environmental impacts.  Advanced Low-NOx burners do not present any new issues.  Low-NOx burners are currently installed at the CPB units.  With respect to overfire air, this is a process that involves adding an additional source of air available for combustion into the furnace, again no new environmental considerations are involved.  Both SNCR and SCR will involve a reagent which will produce an ammonia slip of a few parts per million (ppm), the SNCR will have a slightly higher slip.  However these low levels of ammonia slip are not environmentally significant.  The SCR brings with it an additional environmental consideration of catalyst which the SNCR process does not involve.  The Gas Reburn option does not bring any new consideration. All of the above does not affect the flue gas dispersion parameters used in the air quality modelling.  As a result of the above consideration, SCR has been selected as the most conservative process with respect to environmental impact. 

2.3.3                     Review of the Available SO2 Emission Control Technologies

Overview of SO2 Emission Control Technologies

Flue gas desulphurisation (FGD) represents the most extensively used method for limiting SO2 emissions from large-scale fossil fuel combustion.  These methods remove SO2 from the flue gases in the furnace or, most frequently, in a processing unit downstream from the boiler.  Many widely used FGD systems can achieve a high level of SO2 removal efficiencies.  Typical SO2 control technologies considered for CPB Emission Control Project include:

 

·             Dry Type Flue Gas Desulphurisation

·             Limestone Forced Oxidation Flue Gas Desulphurisation

·             Seawater Flue Gas Desulphurisation

Dry Type Flue Gas Desulphurisation

There are three major types of dry sulphur dioxide removal technologies: Dry Circulating Scrubber (DCS), Spray Dryer Absorber (SDA) and dry sorbent injection.

In dry scrubbers, a calcium hydroxide slurry (quicklime mixed with water) is introduced into a spray dryer tower.  The slurry is atomized and injected (close to saturation) into the flue gases, where droplets react with SO2 as they evaporate in the vessel.  The resulting dry by-product is collected in the bottom of the spray dryer and in the particulate removal equipment (ESP or bagfilter).

 

SO2 may also be removed by injecting a sorbent (lime, limestone, or dolomite) into the combustion gases.

The sorbent decomposes into lime, which reacts in suspension with SO2 to form calcium sulphate (CaSO4). The calcium sulphate, unreacted sorbent, and fly ash are removed at the particulate control device (either an electrostatic precipitator or bagfilter) downstream from the boiler.  Sorbent injection, however, affects the properties of the particulates (higher resistivity and different size and morphology than derived from pulverized coal without SO2 control), which in turn adversely affects the performance of the electrostatic precipitator (ESP).

Dry FGD systems have up to 70-90% SO2 removal efficiency, but their disadvantages are the use of reagents that are less cost effective and the large amounts of waste by-products which are of little or no commercial value and have to be disposed in a landfill site.

Limestone Forced Oxidation Flue Gas Desulphurisation (LSFO FGD)

LSFO FGD is by far the most commonly used FGD technology for large power boilers ([2]).  In typical wet scrubbers the flue gas enters a large vessel (spray tower, absorber, bubbler, etc), where it is sprayed or mixed with limestone slurry.  The calcium in the slurry reacts with the SO2 to form calcium sulphite or calcium sulphate.  A portion of the slurry from the reaction tank is pumped into the thickener, where the solids settle before going to a filter for final dewatering to about 50 percent solids. 

Limestone with forced oxidation (LSFO) is a variation of the traditional wet scrubber in that it utilizes limestone instead of lime.  In the LSFO process, the flue gas is passed through absorbers that contain a slurry of ground limestone in water.  The sulphur dioxide is removed by reacting with the limestone (calcium carbonate) to form calcium sulphite.  The slurry is then aerated to oxidise the calcium sulphite initially formed and is nearly fully oxidized to form gypsum (calcium sulphate).  The resulting gypsum slurry is then treated, resulting in dewatered gypsum and a small quantity of liquid effluent.  The resulting effluent may have a small chemical oxygen demand and/or reduced dissolved oxygen concentrations.   

The treated effluent from the Limestone FGD process is likely to have the following characteristics:

·             Increased concentrations of sulphate ions;

·             Small amount of suspended ash particles, which are likely to contain some trace amount of metals content; and

·             Chemical oxygen demand (COD).

The effluent will be treated to comply with the discharge standards stipulated in the Technical Memorandum on Standards for Effluents Discharged Into Drainage And Sewerage Systems, Inland And Coastal Waters issued under the Water Pollution Control Ordinance.  It will then be added to the cooling water flows and discharged via the existing sub-marine cooling water outfall of CPB, resulting in a small increase in the total flows from the outfall.  It should be noted that there would be no effect on the temperature of the cooling water or on the quantities of residual chlorine in the discharge.

By-products (up to 240,000 tpa of commercial grade gypsum and 17,000 tpa of lower grade gypsum) and sludge arising from FGD wastewater treatment (about 180 tpd at 30% dry solids) will be generated from the operation of the Limestone FGD system.  Gypsum is a material that can be used for a number of applications (such as plasterboard and cement production).  According to a market survey commissioned by CLP Power (as CAPCO operator), there is a large demand of gypsum in Pearl River Delta (PRD) and East-Asia region.  Taking into account the anticipated growth in population growth and GDP in the region, it is anticipated that all the commercial and lower grade gypsum would be recycled through the regional market (the total gypsum generation rate is only a few percentage of the existing consumption of gypsum for plasterboard and cement production in the PRD and East-Asia region).  A number of plasterboard and cement manufactures in the region have expressed interest in engaging in a long term arrangement to take all the gypsum to be generated by the FGD operations. 

Typical SO2 removal efficiency of the LSFO FGD system is 90%.  Approximately 1 to 2 percent of the unit's generating capacity is consumed to meet the power requirements of the scrubber.  LSFO FGD may also help reduce particulates emission to some extent.

Sea Water Flue Gas Desulphurisation (SWFGD)

SWFGD system reduces SO2 emissions by reacting seawater with the flue gas.  Seawater (reagent) contains natural alkalinity due to dissolved calcium and magnesium bicarbonate will react with the acidic components of the flue gas to form soluble compounds that become part of the effluent.

For the SW FGD option a portion of the existing cooling water is diverted, typically 25% of the total flow, to the absorber.  In the absorber, the sulphur dioxide is stripped from the flue gas, reacting with the seawater to form sulphite ions.  The effluent from the absorber is mixed with more seawater to reduce acidity (ie raise the pH level) and vigorously aerated to oxidise the sulphite ions, producing sulphate ions.  Depending upon the effectiveness of the aeration process the final effluent may have a small chemical oxygen demand and/or reduced dissolved oxygen concentrations.  The flue gas will contain small quantities of ash, which are likely to be captured by the seawater in the FGD system.  The ash is likely to contain some trace amount of metals content, the quantities of which depend upon the constituents of the original coal fuel. 

The final effluent from the SW FGD process is likely to have the following characteristics:

·             Increased temperature;

·             Increased concentrations of sulphate ions;

·             Decreased pH;

·             Suspended ash particles, which are likely to be contaminated with trace amount of metals content;

·             Chemical oxygen demand (COD); and

·             Decreased dissolved oxygen.

The final effluent is then returned to the main cooling water stream and discharged via the CPB outfall.  It should be noted that the SW FGD process will typically not result in either increased cooling water flows or a change in the residual chlorine concentrations at the discharge point.

Typical SO2 removal efficiency of SW FGD is 80%.  Particulate emission is also expected to be reduced.  No solid waste is generated, but one of the major drawbacks is that additional sulphate, chlorine and heavy metals would discharge back into the sea.  This has limited the worldwide application of this technology.

Summary of the Option Evaluation for SO2 Emission Control Technologies

LSFO FGD can achieve typically 90% reduction of SO2 emissions and SW FGD would reduce SO2 emissions by about 80%.  Both could achieve a higher level of SO2 reduction than the Dry Type FGD systems.  They also offer the environmental benefit over Dry Type FGD regarding the issue of waste / byproduct management.  Dry Type FGD could result in large amounts of waste by-product, which may have no commercial value and has to be disposed in a landfill site. 

The potential water quality impacts from the LSFO FGD option were considered to be much less than those from the SW FGD option, which is to be expected given the very small treated effluent discharge from the LSFO FGD system.  The SW FGD system reduces the sulphur dioxide (SO2) emissions by reacting seawater with the flue gas.  Some of the fly ash and trace elements entering the SW FGD system will also be removed by the seawater and ultimately end up in the discharge water, which is undesirable.  The long-term marine water quality impacts throughout the operating life of the SW FGD are considered to outweigh the transient localised impacts from the construction of additional berthing facility required for the LSFO FGD option.

On the other hand, LSFO FGD's by-product gypsum can be commercially recycled as construction materials.  As there are large demand for gypsum market in the PRD and East Asia region, gypsum would be commercially recycled through the regional market or through a buy-back agreement with the limestone supplier.  However, provision for a temporary buffer storage within CAPCO facilities will be required to allow for operational contingencies.

Table 2.2 summarises the main features of control technologies discussed above.

Table 2.2         Summary of Considered SO2 Control Options

Control Technology

Typical Efficiency

Environmental Considerations

Other Comments

Dry Flue Gas Desulphurisation (FGD) Systems

 

70-90%

Solid waste that cannot be reused

 

Limestone Forced Oxidation Flue Gas Desulphurisation (LSFO FGD)

 

90%

Solid by-product (gypsum) can be recycled with commercial outlets. 

 

Sludge from wastewater treatment can be disposed of locally.

 

Preferred

Sea Water Flue Gas Desulphurisation (SW FGD)

80%

Contaminated effluent with elevated sulphate, chlorine and heavy metals discharged into the sea throughout the operating life of the system and uncertainties with regard to potential bioaccumulation

 

Limited operational experience for large coal-fired plants

 

2.3.4                     Selection of Emissions Control Option

Following the review of different control options and consideration of their environmental impacts, the SCR and LSFO FGD were selected as the package of emission control options for the purpose of the EIA Study.  The choice was based on the expected environmental benefits of each option, potential adverse environmental impacts and technological feasibility.

The environmental impacts of these options and the reasons for selecting these measures have been discussed and summarised in Tables 2.1 and 2.2.

·             SCR has been selected as the most conservative process with respect to environmental impact.  This is due to the fact that the SCR system encompasses the facilities and elements associated with the other available NOx reduction technologies 

·             Limestone FGD was selected due to its technological maturity, and the overall lower environmental side effects when compared to other FGD technologies.

The preliminary general arrangements of the proposed facilities are shown in Figure 2.1. 

2.4                           Consideration of Alternative Construction Methods and Sequence of Work

The total capacity of the four existing power generation units at CPB represents about one-third of all electricity supplied by CAPCO and CLP Power for use in Hong Kong.  Given the complexity and scale of the Project, both the engineering design and construction are being carefully planned to ensure the facilities are phased in smoothly while maintaining a reliable electricity supply.  The Project will involve retrofitting the existing units with additional equipment for emissions control.  Special considerations have to be given to site constraints such as ground footprint limitations, extensive relocation of existing facilities and common systems, customisation of emissions control equipment to meet specific site requirements and plant conditions while maintaining a reliable power supply.

The scheme described in Section 2.5 takes into account of many constructability issues associated with this complex retrofitting project.

2.5                           Description of the Selected Scheme

The currently envisaged construction and operational activities associated with the Project are presented below.

2.5.1                     Construction Phase

Demolition and Relocation of Certain Existing Facilities

While the existing generating units will remain in their current locations, some of their auxiliary and common facilities to the south of the generating units at CPB may be demolished or relocated to provide space for the FGD, SCR and related facilities.  It must be emphasized that the extent of demolition / relocation works depends primarily on the layout and design of the new emissions control facilities which will be finalised during the design engineering phase.  The following paragraphs aim to provide a description of the current scheme of these demolition / relocation works.

Demolition of CPB Fuel Oil Day Tank

The Fuel Oil Day Tank (FODT), which has a capacity of 4,680 t, with the associated stairs, piping, instrumentation, junction boxes, heat tracing, cables, etc, located southwest of the CPB generating units will be demolished.  The works will involve cutting the fuel oil piping, moving the fuel oil equipment, and demolishing the fuel oil tank and retaining wall.

The existing 1 m thick reinforced concrete foundation under the tank will be left in place.  The eight existing 2 m diameter caissons drilled into the bedrock will also remain in place.  The portion of the concrete slab between the tank support foundation and the retaining wall will be backfilled with compacted granular.  The oil interceptor serving the FODT bund areas will also be removed.

Demolition of Dangerous Goods Store

The Dangerous Goods (DG) Store to the south of the FOPH will be demolished.  The ground floor slab and the existing concrete pavement will remain in place.  If caissons or concrete piers are required in the area to support the future emissions control equipment, portions of the pavement will be demolished. 

Re-routing of Underground Pipeworks

Several sections of the underground pipeworks of the following systems will be re-routed aboveground:

·    sea water flushing;

·    town water domestic;

·    town water maintenance; and

·    sea water fire main.

The underground trench will be backfilled with soil after re-routing of the pipeworks.

Relocation of CO2 Storage Tank

The existing 2,626-litre CO2 storage tank, fill connection and vaporisers will be relocated from their existing locations to the area north of the chemical waste building in an area presently occupied as a scaffolding laydown area.  The concrete slab supporting the existing CO2 Tank will remain in place.

Relocation of the LPG Storage Tanks

The existing two LPG tanks of 4,600 litres capacity each and the associated equipment will be removed and relocated to the existing foundation and piers east of Eastern Road.  The adjacent vapour room and switch room will be demolished but the concrete slab on grade will remain in place.

Relocation of the Intermediate Pressure Reduction Station

The Intermediate Pressure Reduction Station (IPRS) of the gas transmission system will be relocated to provide space for the installation of the emissions control equipment.  The concrete slab floor and objects protruding aboveground will be demolished and backfilled.

Installation of the New Emissions Control Equipment and Facilities

New facilities to be installed for the Project will include the SCR and FGD equipment, reagent and by-product handling and storage facilities associated with the SCR and FGD operations.  An additional berthing facility for the loading and unloading of reagents and by-products will also be required.  These are described in the following sections.

Installation of SCR and FGD Facilities

The SCR and FGD facilities will be retrofitted to the CPB generating units.  The exact footprint of these facilities will be finalised upon design optimisation.

Provision of Reagent and By-product Handling and Storage Facilities

The major reagent and by-product handling facilities for FGD operations will include limestone storage facilities, limestone slurry tanks, gypsum dewatering and storage facilities, and handling and storage facilities for lower grade gypsum.  SCR systems will require urea as the ammonia supply reagent, urea storage facilities, dissolvers, urea solution storage tanks and urea-to-ammonia reactors will be required.

Provision of Additional Berthing Facility

The SCR systems could require about 40,000 tonnes per annum (tpa) of urea, while the FGD systems could consume about 150,000 tpa of limestone and generate about 257,000 tpa of gypsum as by-product.  The quantities of reagents required and by-product produced will be finalized during the design engineering phase.  It is anticipated that additional berthing facility will be needed for the loading and unloading of process reagents and by-product.

The provision of additional berthing is by extending the existing Heavy Load Berth to form a multi-purpose wharf, providing a straight quay with the potential to accommodate ships with a wide range of loaded draft requirements.  It is anticipated that the extension work will require some small-scale dredging for the foundations of the deck and for providing sufficient turning basin for the different marine vessel loaded draft requirements.  The estimated quantity of the dredged sediment is 80,700 m3.  Figure 2.2 shows the existing hydrographical profile (i.e. seabed level) in the vicinity of the additional berthing facility.  Based on the loaded draught requirement of the vessels to be accommodated, a minimum depth of -8.2 mPD will be required.  The area expected to require dredging for the additional berthing facility has been determined taking into account the loaded draught requirements, the existing hydrographical profile and the safety requirements for the berthing manoeuvres and the dredging area is shown in Figure 2.3.

The preliminary design of the additional berthing facility, with the envisage pile design and layout, is presented in Figure 2.4.

2.5.2                     Operational Phase

The schematics of the emissions control systems have been presented in Figure 2.5.  The FGD wastewater treatment system (or known as the chloride purge treatment system) is used to treat effluent from LS FGD processes.  No effluent is anticipated from the operation of the NOx control system.

2.5.3                     Proposed Project Programme

Subject to timely agreement of a long-term environmental policy and the successor regulatory regime with the HKSARG, the currently envisaged project milestones are as follows:

 

Key Stage of the Project

Indicative Date

Finalisation of other major permitting requirements

2006

Completion of front-end engineering design

1st half of 2007

Commencement of relocation of existing facilities

1st half of 2007

Award of major contracts

2007

Dredging works

2nd Quarter of 2007

Commencement of retrofit site work

End 2007

Start-up of the retrofitted units

End 2009 to 2011

 



([1])             http://www.epd.gov.hk/epd/english/environmentinhk/air/prob_solutions/files /Brief_Progress_Report_Nov2005.pdf

([2])              According to Integrated Pollution Prevention and Control (IPPC) - Reference Document on Best Available Technique for Large Combustion Plants published by the European Commission in 2005, wet limestone FGD is the most widely used of all the FGD systems and accounts for about 80% of all the installed FGD capacity.