PWP No. 016NB Phased Reprovisioning of Cape Collinson Crematorium Environmental Impact Assessment Study EIA Report
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PWP No. 016NB Phased Reprovisioning of Cape Collinson Crematorium Environmental Impact Assessment Study EIA Report 3 AIR QUALITY Introduction 3.1 This Section presents an assessment of the potential air quality impacts associated with the demolition of the existing crematorium, construction and operation of the new crematorium. The air quality impact assessment was conducted in accordance with the requirements of Annex 4 and Annex 12 of the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM) as well as the requirements set out under Clause 3.4.1 and Appendix B of the EIA Study Brief. Description of the Project Project Background 3.2 The existing Cape Collinson Crematorium has started operation since 1962. Cremator Nos. 1- 10 were replaced in 1995 and Nos. 11-12 were commissioned in 2001. In order to cope with an increasing demand for cremation service, Food and Environmental Hygiene Department (FEHD) proposes to demolish the existing crematorium as well as to construct and operate a new crematorium in-situ as a replacement (hereinafter referred to as the Project). 3.3 The Project will be developed in two phases, namely Phases 1 and Phase 2. The Project Site is the site of the existing Cape Collinson Crematorium which consists of four service halls with twelve cremators. Site formation work will be carried out at the beginning of Phase 1 which involves extension of the existing car park area for the construction of an access road. After the site formation has been completed, a new crematorium with 4 cremators will be constructed to the north of the existing crematorium. During this period, all the 12 cremators in the existing crematorium will remain in operation until the satisfactory commissioning of the new cremators under Phase 1 by 2012. 3.4 As advised by the Project Proponent, the existing crematorium will still be operating to serve the public during the testing and commissioning (T&C) of the four new cremators under Phase 1. However, special arrangement will be made to control that there will be no more than ten of both existing and new cremators in operation at any time (i.e. two new cremators and eight existing cremators) during T&C period to avoid additional loading of chimney emissions to the environment. In other words, eight out of 12 existing cremators will be operated concurrently with two new cremators during T&C period of Phase 1. Details of the operating conditions during T&C period of Phase 1 would be presented in Sections 3.42 to 3.44 below. 3.5 After the satisfactory commissioning of the new cremators under Phase 1, demolition of the existing crematorium, construction of another six cremators and one service hall will then be carried out in Phase 2. No overlapping of construction/demolition works between Phase 1 and Phase 2 will occur. Phase 2 works will be completed in 2014. 3.6 A total of ten cremators will be provided in the new crematorium. Nine cremators will be of 170 kg/cycle (equivalent to 145.7 kg/hr) capacity and the remaining one cremator will be of 250 kg/cycle (equivalent to 214.3 kg/hr) capacity. The total operating capacity of the cremators will be about 1.5 tonne/hour under full load conditions. As the operating capacity of the new cremators would exceed the exempted capacity of Specified Process – Incinerators under the Air Pollution Control Ordinance, i.e.0.5 tonne/hour, FEHD is required to obtain a specified process licence from EPD for the operation of the new cremators. The Specified Process Licence under APCO will provide overall control of the design, operation, emission limits, monitoring and maintenance of the New Crematorium. It should be noted that the New Crematorium would be used for cremation of coffins and human bodies including amputated limbs and tissues, and would not process any pathological waste. 3.7 Apart from the new cremators, three units of joss paper burners will be installed. Burning of the joss paper usually emits smoke which may affect the nearby environment. Therefore, the ENSR Asia (HK) Ltd. 3-1 February 2009 PWP No. 016NB Phased Reprovisioning of Cape Collinson Crematorium Environmental Impact Assessment Study EIA Report potential air quality impact arising from operation of joss paper burner is also considered in the EIA Study. Cremation Technology 3.8 Cremation is commonly adopted in Hong Kong as a means to dispose of the dead body. Cremation is a process of burning the dead body at high temperature to decompose organic matters. Incombustibles such as bone ash would remain after cremation. A complete cremation normally takes about 2 to 2.5 hours. During cremation, exhaust flue gas containing air pollutants is treated when passing through APC equipment before discharging into the surrounding air. In recent years, cremators have been designed with two combustion chambers, namely the primary combustion chamber and the secondary combustion chamber. The former for cremation of the coffin and its content, and the latter to burn the flue gas to attain the complete combustion so as to enhance the combustion efficiency and reduce air pollutant emissions. 3.9 Cremators of flat-bed type and free-falling type are most commonly used due to their high combustion efficiency. Higher combustion efficiency of new cremators helps decompose organic matters more completely and hence reduction in air pollutants emissions from the cremation process. 3.10 Flat-bed cremators consist of a furnace slide door, primary combustion chamber, secondary combustion chamber, a cease-burning chamber and an ash cooling zone. The combustion chambers are made of high quality fire-bricks and insulation materials. The primary and secondary chambers are located one on top of the other in a compact configuration, achieving optimum heat exchange between the two combustion chambers. 3.11 Free-falling cremators consist of a primary combustion chamber at high level and a mineralization chamber at a lower level. The “cremains” (a portmanteau of “cremated” and “remains”) will fall from the primary combustion chamber to the mineralization chamber (cremains collection chamber). When the cremains are transferred to the mineralization chamber, another coffin can be fed into the primary combustion chamber for cremation. The operations of the primary combustion and mineralization chambers are independent. 3.12 The newly built Diamond Hill Crematorium is equipped with 6 units of free-falling cremators provides an example of new cremation technology that could be adopted in the new Cape Collinson Crematorium. Although the final selection of cremation technology would be subject to open tendering procedure, the performance and specifications of the new cremators shall fully comply with the BPM12/2(06). Air Pollution Control Technology 3.13 The flue gas emissions from the New Crematorium would have the most significant environmental impact to the public. The combustion process within the flue emissions from the new crematorium will generate air pollutants, such as particulate matter, heavy metals, organic gases, acidic gases, dioxins, etc. Installation of an APC equipment is required to reduce the emissions of such air pollutants to acceptable levels. Applicable APC technologies are described below. Wet Scrubbing 3.14 Wet scrubbing removes air pollutants in flue gas through dissolution and chemical absorption by scrubbing solution. The solution may be water or other chemical solutions. Common scrubbing solutions include sodium hydroxide, acidified potassium permanganate, hypochlorite and other acidic solutions. Carbon Injection 3.15 Carbon injection removes organic air pollutants in flue gas. Fine charcoal powder is injected ENSR Asia (HK) Ltd. 3-2 February 2009 PWP No. 016NB Phased Reprovisioning of Cape Collinson Crematorium Environmental Impact Assessment Study EIA Report into the flue gas ducting and organic air pollutants in flue gas are absorbed by the charcoal powder. The fine charcoal powder is then collected with bag filter. This technology is commonly adopted to control the emissions of dioxins and is a dry air pollution control process. Neutralization with Chemical 3.16 Neutralization is adopted if the flue gas is highly acidic or alkaline. For acidic gases, neutralization is accomplished by spraying of lime or soda lime solution to the flue gas. Inorganic acids are usually used to neutralize highly alkaline flue gas. Spray nozzle or jet nozzle is usually used to spray neutralizing solution to the flue gas system. This is a dry air pollution control process. Electrostatic Precipitation 3.17 Electrostatic precipitators are used to collect fine particulate matters in flue gas. The electrostatic precipitator maintains an electric field of several kilowatts to charge up the fine particulates. The charged particulates are collected with the oppositely charged collector plates. Electrostatic precipitators are highly efficient in collecting fine particulates. Collected dust is easily handled and disposed of. This is a dry air pollution control process. Bag Filters 3.18 Bag filters are commonly adopted to control particulate emissions. Particulate matters are collected with the filter medium. The filter bags may be made of cotton or fabric material. Filter bags would be cleaned up regularly to avoid clogging. This is a dry air pollution control process. Quenching 3.19 If flue gas is cooled down slowly to about 400°C to 600°C, atoms of carbon, oxygen, hydrogen and chlorine would re-combine to form dioxins, as these are the most thermodynamically favourable chemical species – this is the dioxin “formation window”. Quenching cools down the flue gas suddenly, to shorten the time within the dioxin “formation window” and so avoids the formation of dioxins. Quenching is usually achieved by drawing in a large amount of fresh air or spraying of water. Flue Gas Cleaning System to be Adopted in the New Crematorium 3.20 After passing through the heat exchanger, the flue gas will enter the flue gas filtering plant, such that specific pollutants in the gas stream will be trapped.