Code of practice to reduce emissions of PM2.5 from aluminium sector: executive summary
Official title: Code of practice to reduce emissions of fine particulate matter (PM2.5) from the aluminium sector
Executive summary
Federal, provincial and territorial ministers of the environment are taking action to better protect human health and the environment by endorsing and implementing the new Air Quality Management System (AQMS). The AQMS includes Canadian Ambient Air Quality Standards for fine particulate matter and ground-level ozone, base-level industrial emissions requirements (BLIERs) and air zone management by provincial and territorial jurisdictions. For the aluminium sector, quantitative BLIERs were developed for total particulate matter (TPM), polycyclic aromatic hydrocarbons (PAH) and sulphur dioxide (SO2). Qualitative BLIERS were also developed for SO2 and PM2.5, including the realization of this code of practice to reduce PM2.5 emissions. This Code of Practice (Code) applies to operational activities related to the primary aluminium sector, including:
- production of aluminium from alumina (electrolytic reduction)
- prebaked anode production
- green coke calcining and
- alumina production
In 2013, 13 facilities in Canada were operating in at least one of these activities. These facilities include ten aluminium production plants, six prebaked anode production plants, three green coke calcining plants and one alumina production plant. Secondary activities, including port and/or rail services for transporting raw materials, regional hydroelectric plants and electrolytic cell relining centres are not covered by the code, nor are activities associated with the electrolytic reduction process using Söderberg technology.
This code was developed by Environment Canada in consultation with aluminium industry representatives and other stakeholders. Information on operating procedures and best practices is taken from various sources, including technical and scientific journals, as well as environmental codes of practice published by Environment Canada, the European Commission, the World Bank and the Light Metals Research Centre (LMRC) at the University of Auckland in New Zealand.
The code describes potential sources of PM2.5 emissions for each of the primary operational activities (Section 2) and makes recommendations to control and reduce these emissions (Section 3). These recommended practices can be used by the primary aluminium industry, regulatory agencies and the general public as a source of technical and policy guidance but they do not replace regulatory requirements. The practices should be implemented in a continuous improvement context, where required, relevant and applicable.
Table S-1 lists measures recommended to limit PM2.5 emissions from each of the sectors’ operational activities.
Owing to the constraints inherent in the technology, the Code does not aim to eliminate PM2.5 emissions but rather to control them through effective measures and best practices. Furthermore, the Code does not recommend practices that would require an existing facility to make major technological changes.
When new facilities are being designed, other technologies can be taken into consideration to further reduce emissions, including high draft ventilation of pots activated when hoods are opened and a regenerative oxidation system to eliminate pitch emissions.
| Operational activity | Source | Recommendation number | Recommendation description |
|---|---|---|---|
| Production of aluminium from alumina | Opening of electrolytic cell hoods | R01 | Optimize work methods to allow a minimum of hoods to be opened simultaneously, and to open them only once work begins. Close hoods as soon as work is complete. |
| Production of aluminium from alumina | Gas extraction system | R02 | Regularly assess the extraction efficiency of fans in relation to power supply, flow rate and pressure loss. Make adjustments as needed to maximize the extraction rate. |
| Production of aluminium from alumina | Changing of prebaked anodes | R03 | Optimize work methods to minimize the time it takes to change anodes and cover them with anode cover material. |
| Production of aluminium from alumina | Crust covering cryolite bath | R04 | Implement a program to monitor cracks in the crust by visual inspection or using an automated system. Ensure that the anode cover material is suitable and effective as a sealant. |
| Production of aluminium from alumina | Crust covering cryolite bath | R05 | Cover the tap hole with anode cover material once the tapping or sampling work is complete. |
| Production of aluminium from alumina | Tapping of cryolite bath and molten metal | R06 | During tapping operations, use flexible tubing to reroute fumes released from the crucible within the pot. |
| Production of aluminium from alumina | Cryolite bath spatter and spills | R07 | Minimize and recover cryolite bath spills and spatter on the floor. |
| Production of aluminium from alumina | Cryolite bath spatter and spills | R08 | Pour the bath into the cell launder at an optimal speed to reduce pouring time and avoid spatter. Avoid pouring too slowly. |
| Production of aluminium from alumina | Cryolite bath spatter and spills | R09 | Minimize and recover cryolite bath residue in the launder when loading is complete. |
| Production of aluminium from alumina | Skimming of carbon dust | R10 | Cool the hot carbon dust inside the pot or in a container with a cover. Minimize the amount of time carbon dust spends in the potroom. |
| Production of aluminium from alumina | Control of operating parameters | R11 | Control and maintain an optimal bath level in the pot to prevent an unintended rise in bath temperature and direct contact with moist air. These two phenomena exacerbate the formation of fluorinated particles. |
| Production of aluminium from alumina | Control of operating parameters | R12 | Prevent, control and minimize anode effect, frequency and duration. After manually suppressing anode effects, cover cracks in the crust with anode cover material. |
| Production of aluminium from alumina | Casting of molten aluminium | R13 | Minimize releases of particulate matter from the casting centre. |
| Production of aluminium from alumina | Maintenance activities | R14 | Regularly inspect, according to a set schedule, the aluminium production (electrolytic reduction) plant’s facilities, including the condition of hoods, the gas exhaust ducts for each pot, the alumina supply system and the pot superstructure. In the event of breakdowns or malfunctions, make repairs or install appropriate replacement parts as soon as possible. |
| Production of aluminium from alumina | Maintenance activities | R15 | Implement an employee training plan in support of an approach for preventing premature wear and breakdowns caused by improper operation of the facilities. |
| Production of aluminium from alumina | Cleaning activities (electrolytic reduction) | R16 | Use a HEPA vacuum to clean the floor of the potroom and other buildings. |
| Production of aluminium from alumina | Cleaning activities (electrolytic reduction) | R17 | Regularly clean the suction inlet located inside the pot superstructure (slots, ventilation hoods section, etc.) |
| Production of aluminium from alumina | Cleaning activities (electrolytic reduction) | R18 | Regularly clear solid residues from the feeder/breaker to reduce the size of the hole in the crust after injection, thus decreasing emissions (corollary to Recommendation R05). |
| Production of aluminium from alumina | Monitoring of scrubber operations | R19 | Regularly and periodically monitor the gas flow in each scrubber compartment while ensuring it is uniform. Monitor pressure loss in order to identify anomalies requiring correction. |
| Production of aluminium from alumina | Monitoring of scrubber operations | R20 | Adjust cleaning frequency and duration for the dust collectors or scrubber and filtration media to balance gas flow for each compartment and maximize collection efficiency. |
| Production of aluminium from alumina | Monitoring of scrubber operations | R21 | Where possible, depending on the production sector, limit the recycling of enriched or fluorinated alumina in GTC and FTC injection reactors, without influencing HF capture. Regularly and periodically monitor the recycling rate to ensure it is optimal. |
| Production of aluminium from alumina | Maintenance of scrubbers, dust collectors and related systems | R22 | Depending on the production sector and the filtration system, regularly inspect the following on a set schedule: the scrubber, including the collection system, sealing joints, fan (corollary to Recommendation R02) and alumina or calcined coke supply systems. Repair any breakdowns or malfunctions as soon as they are noted. |
| Production of aluminium from alumina | Maintenance of scrubbers, dust collectors and related systems | R23 | For the dust collector, replace the bags and other filtration media at the end of their service life. Do not wait until a breakdown occurs. |
| Production of aluminium from alumina | Maintenance of scrubbers, dust collectors and related systems | R24 | For the GTC, regularly inspect ducts where hard gray scale is likely to accumulate. Clean if too much has accumulated. |
| Production of aluminium from alumina | Monitoring of facilities and their outputs | R25 | Monitor emissions of particulate matter from dust collectors. Investigate the causes of sudden increases in particulate matter emissions and make necessary adjustments. |
| Production of aluminium from alumina | Monitoring of facilities and their outputs | R26 | Carry out visual monitoring of pneumatic injection and mechanical handling systems according to a set schedule in order to detect leaks. Make repairs as soon as possible. |
| Production of aluminium from alumina | Monitoring of facilities and their outputs | R27 | Periodically monitor and maintain dust collectors and replace filtration media at end of service life (corollary to Recommendations R22 and R23). |
| Production of aluminium from alumina | Transportation of anode butts | R28 | Minimize air exposure time (and transport time) of anode butts within or outside the potroom. For example, make effective use of covered trays (or equivalent) to cool and transport anode butts (or crust and hot cryolite bath) to the storage room. |
| Prebaked anode production | Baking furnace | R29 | Maintain an effective system for filling baking furnace pits with packing coke to limit coke losses in the building. Train operators in order to standardize work methods for handling packing coke. |
| Prebaked anode production | Baking furnace | R30 | Monitor negative pressure at the FTC inlet or at the exit of the baking furnace |
| Prebaked anode production | Cleaning of anode butts | R31 | Efficiently operate the collection, extraction and filtration systems for dust resulting from the anode butt cleaning process. |
| Prebaked anode production | Crushing of frozen bath | R32 | Filter emissions of fine particulate matter released from the crushing of frozen bath using dust collectors. |
| Prebaked anode production | Maintenance activities | R33 | Regularly inspect the following on a set schedule: the prebaked anode production facilities, including systems for anode butt cleaning, frozen bath crushing, and calcined coke grinding and sieving as well as the baking furnace. In the event of breakdowns or malfunctions, make repairs or install appropriate replacement parts as soon as possible. |
| Prebaked anode production | Maintenance activities | R15 | Implement an employee training plan in support of an approach for preventing premature wear and breakdowns caused by improper operation of the facilities. |
| Prebaked anode production | Monitoring of operations (FTC and PFTC) | R34 | For the FTC only, operate the cooling tower so as to condense most of the tar contained in the baking gas. If necessary, add a prefilter (for example, ceramic packing) to capture most particulate and condensable matter, including tar. |
| Prebaked anode production | Monitoring of operations (FTC and PFTC) | R19 | Regularly and periodically monitor the gas flow in each scrubber compartment while ensuring that it is uniform. Monitor pressure loss in order to identify anomalies requiring correction. |
| Prebaked anode production | Monitoring of operations (FTC and PFTC) | R20 | Adjust cleaning frequency and duration for the dust collectors and scrubber filtration media to balance gas flow for each compartment and maximize collection efficiency. |
| Prebaked anode production | Monitoring of operations (FTC and PFTC) | R21 | Wherever possible, depending on the production sector, limit recycling of enriched or fluorinated alumina in GTC and FTC injection reactors without influencing HF capture. Regularly and periodically monitor the recycling rate, to ensure it is optimal. |
| Prebaked anode production | Type of fuel | R35 | With regard to particulate matter emissions, use hydroelectric power in favour of fossil fuels if possible with the current system. Otherwise, use natural gas instead of fuel oil (or other heavy fuels). For facilities that do not have access to hydro power, careful consideration should be given to other electric power sources before making a decision to switch fuels. |
| Prebaked anode production | Gas extraction system | R02 | Regularly assess the extraction efficiency of fans in relation to power supply, flow rate and pressure loss. Make adjustments as needed to maximize the extraction rate. |
| Prebaked anode production | Maintenance of scrubbers, dust collectors and related systems | R22 | Depending on the production sector and the filtration system, regularly inspect the following on a set schedule: the scrubber, including the collection system, the sealing joints, fan (corollary to Recommendation R02) and alumina or calcined coke supply systems. Repair any breakdowns or malfunctions as soon as they are noted. |
| Prebaked anode production | Maintenance of scrubbers, dust collectors and related systems | R23 | For the dust collector, replace the bags or other filtration media at the end of their service life. Do not wait until a breakdown occurs. |
| Prebaked anode production | Monitoring of facilities and their outputs | R25 | Monitor emissions of particulate matter from dust collectors. Investigate the causes of sudden increases in particulate matter emissions and make necessary adjustments. |
| Prebaked anode production | Monitoring of facilities and their outputs | R26 | Carry out visual monitoring of pneumatic injection and mechanical handling systems according to a set schedule in order to detect leaks. Make repairs as soon as possible. |
| Prebaked anode production | Monitoring of facilities and their outputs | R27 | Periodically monitor and maintain dust collectors and replace filtration media at end of their service life (corollary to Recommendations R22 and R23). |
| Green coke calcining | Maintenance activities | R36 | Regularly inspect the following on a set schedule: the green coke calcining and cooling facilities, including sealing joints and other mechanisms that could potentially lead to a gas leak and emissions of PM2.5. In the event of breakdowns or malfunctions, make repairs or install appropriate replacement parts as soon as possible. |
| Green coke calcining | Maintenance activities | R15 | Implement an employee training plan in support of an approach for preventing premature wear and breakdowns caused by improper operation of the facilities. |
| Green coke calcining | Monitoring of operations (pyroscrubber) | R37 | Optimize the operating parameters of the pyroscrubber to maximize incineration of coke particles in addition to VOCs. As needed, follow up with a system designed to detect particles leaving the pyroscrubber and adjust accordingly. |
| Green coke calcining | Monitoring of operations (boiler followed by a dust collector) | R38 | Optimize the performance of the cyclones and dust collector based on the total particle load. As needed, replace bags with more efficient ones. |
| Green coke calcining | Monitoring of operations (venturi wet scrubber) | R39 | Regular and periodically monitor the gas flow rate through the scrubber by measuring the water flow rate to the venturi inlet. The ration of the two has a direct effect on pressure loss and the effective capture of particulate matter, including PM2.5. Optimize performance for the existing system. |
| Green coke calcining | Green coke storage | R40 | Unload the green coke in a closed building at the coke calcining plant. Move green coke between various transfer points using closed conveyors or similar equipment or any other measures that can control dust emissions. |
| Green coke calcining | Gas extraction system | R02 | Regularly assess the extraction efficiency of fans in relation to power supply, flow rate and pressure loss. Make adjustments as needed to maximize extraction rate. |
| Green coke calcining | Maintenance of scrubbers, dust collectors and related systems | R22 | Depending on the production sector and the filtration system, regularly inspect the following on a set schedule: the scrubber, including the collection system, sealing joints, fan (corollary to Recommendation R02) and alumina or calcined coke supply systems. Repair any breakdowns or malfunctions as soon as they are noted |
| Green coke calcining | Maintenance of scrubbers, dust collectors and related systems | R23 | For the dust collector, replace the bags and other filtration media at the end of their service life. Do not wait until a breakdown occurs. |
| Green coke calcining | Monitoring of facilities and their outputs | R25 | Monitor emissions of particulate matter from dust collectors. Investigate the causes of sudden increases in particulate matter emissions and make necessary adjustments. |
| Green coke calcining | Monitoring of facilities and their outputs | R26 | Carry out visual inspections of pneumatic injection and mechanical handling systems according to a set schedule in order to detect leaks. Make repairs as soon as possible. |
| Green coke calcining | Monitoring of facilities and their outputs | R27 | Periodically monitor and maintain dust collectors and replace filtration media at the end of their service life (corollary to Recommendations R22 and R23). |
| Alumina production | Maintenance activities | R41 | Regularly inspect the following on a set schedule: alumina calcining facilities and boilers at the alumina production plant. In the event of breakdowns or malfunctions, make repairs or install appropriate replacement parts as soon as possible. |
| Alumina production | Maintenance activities | R15 | Implement an employee training plan in support of an approach for preventing premature wear and breakdowns caused by improper operation of the facilities. |
| Alumina production | Red mud disposal | R42 | Set up physical and/or chemical barriers for red mud disposal sites in order to minimize dusting when weather conditions are conducive to the dispersion of dust. |
| Alumina production | Consumption rate | R43 | For boilers and alumina calciners, minimize natural gas or fuel oil consumption per tonne of alumina produced by using efficient heat recovery systems. |
| Alumina production | Monitoring of facilities and their outputs | R25 | Monitor emissions of particulate matter from dust collectors. Investigate the causes of sudden increases in particulate matter emissions and make necessary adjustments. |
| Alumina production | Monitoring of facilities and their outputs | R26 | Carry out visual monitoring of pneumatic injection and mechanical handling systems according to a set schedule in order to detect leaks. Make repairs as soon as possible. |
| Alumina production | Monitoring of facilities and their outputs | R27 | Periodically monitor and maintain dust collectors and replace filtration media at end of service life (corollary to Recommendations R22 and R23). |
| Alumina production | Type of fuel | R35 | With regard to particulate matter emissions, use hydroelectric power instead of fossil fuels if possible with the current system. Otherwise, use natural gas instead of fuel oil (or other heavy fuels). For facilities that do not have access to hydro power, careful consideration should be given to other electric power sources before making a decision to switch fuels. |
| General | Environmental management practices | R44 | Implementation of the recommendations set out in the Code should be integrated with the facility’s environmental management plan, which could include analysis of the initial situation, a training plan, auditing protocols and determination and implementation of corrective measures in a continuous improvement context. |
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