Code of Practice to reduce emissions of PM2.5 from aluminium sector: chapter 1

Official title: Code of practice to reduce emissions of fine particulate matter (PM_2.5) from the aluminium sector

1. Introduction

• 1.1 Scope of the Code
• 1.2 Code development
• 1.3 Code structure
• 1.4 Sector description

Primary aluminium production is a major industry in Canada, ranking third worldwide with an annual production capacity of approximately 3 million tonnes (3.02 Mt in 2013)^Footnote1, 90% of which is produced in Quebec. Aluminium is produced by electrolytic reduction of dissolved alumina in a liquid aluminium fluoride and cryolite bath maintained at a temperature of approximately 960°C. Alumina is extracted from bauxite ore. Between 0.20 and 0.25 tonnes of aluminium is generally produced per tonne of bauxite. Aside from the electrolytic reduction process, the primary aluminium sector includes many related activities, such as the production of metallurgical grade alumina, prebaked anode production and green coke calcining. All of these activities require the use of electricity, fuel and raw materials (petroleum coke, bauxite, aluminium fluoride, cryolite, tar pitch, etc.) which lead to emissions of air pollutants including sulphur dioxide (SO₂), total particulate matter (TPM), polycyclic aromatic hydrocarbons (PAH), total fluorides and nitrogen oxides (NO_X).

Federal, provincial and territorial ministers of the environment are taking action to better protect human health and the environment by 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 PM_2.5 and a PM_2.5 code of practice was developed and implemented: “The code of practice will facilitate and promote the continuous improvement of the environmental performance achieved by facilities in the sector in Canada and will give a detailed description of best practices that can be used to reduce PM_2.5 emissions in the aluminium sector (excluding Söderberg type plants). The code of practice must include, but is not limited to, the following elements: a description of the sector and the main sources of PM_2.5 emissions, and best practices for electrolysis, anode baking furnaces, alumina production and coke calcining.”

With regard to dust emissions, fine particulates with an aerodynamic diameter smaller than 2.5 microns (PM_2.5) can cause serious health problems when they are inhaled and enter the lungs. In Canada, roughly 45% of PM_2.5 emissions are generated by the stationary combustion of firewood and other fuels, and 20% comes from transportation activities (road, off-road, rail, sea, etc.). The remainder (35%) results from industrial activities. Table 1.1 presents the distribution of PM_2.5 releases from the industrial sector in Canada in 2013 as reported to the National Pollutant Release Inventory (NPRI). It can be seen that the aluminium industry is responsible for nearly 7% of industrial emissions of PM_2.5 in Canada.

1.1 Scope of the Code

The Code applies to facilities in the primary aluminium sector, specifically those involved in the production of aluminium from alumina (electrolytic reduction), prebaked anode production, green coke calcining and alumina production. Other activities, including port and/or rail services for transporting raw materials, regional hydroelectric plants, and pot relining centres, are not covered by the Code, nor are activities associated with the Söderberg technology.

The Code was developed as part of the qualitative BLIERs established for Environment Canada’s AQMS policy with the aim of facilitating and encouraging the continuous improvement of the environmental performance of Canada’s aluminium facilities. It describes the potential sources of emissions of fine particulate matter (PM_2.5) for each of the primary activities covered by the Code and makes recommendations to reduce these types of emissions. Owing to the constraints inherent in the technology, the Code does not aim to eliminate PM_2.5 emissions but rather to control them through effective measures and work practices. Furthermore, the Code does not recommend practices that would require an existing facility to make major technological changes. When a new facility is being designed, other technologies capable of further reducing emissions can be incorporated, such as high draft ventilation of pots activated when the hoods are opened and a regenerative oxidation system to eliminate pitch emissions.

Although the recommendations clearly specify the expected results, they should be applied where and when appropriate depending on the particular circumstances of each facility. Accordingly, the Code does not seek to quantify the effect that each recommendation would have on PM_2.5 emissions. Rather, it should be considered a basic tool designed to enable facilities to develop a program of best practices without being subject to regulatory constraints. The recommendations in the Code in no way reduce the scope or application of the legal requirements of municipal, provincial and federal governments.

1.2 Code development

The Code was developed by Environment Canada in consultation with aluminium industry representatives and other stakeholders. The information on operating procedures and best work practices is taken from various sources, including technical and scientific journals, and 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.^Footnote2 The Code presents a non-exhaustive list of recommendations based on the state of Canada’s primary aluminium sector in 2013, particularly with regard to existing air emission control technologies. Where relevant and applicable, facilities may consider implementing other measures for reducing particulate emissions.

1.3 Code structure

The Code describes the operational activities and the particulate emissions that can result from these activities (Section 2). The recommended work practices intended to control fine particulate matter emissions are set out in Section 3.

1.4 Sector description

The primary aluminium sector encompasses many production activities that yield a finished product at a competitive cost (Figure 1-1). There are four key activities associated with aluminium production:

• production of aluminium (electrolytic reduction);
• prebaked anode production;
• green coke calcining; and
• alumina production.

A Canadian aluminium smelter typically consists of an electrolytic reduction plant and a prebaked anode production plant; other, related activities may be carried out elsewhere. Three Canadian aluminium smelters buy their prebaked anodes from another supplier (anode producer) instead of manufacturing them on-site.

Production of aluminium (electrolytic reduction)

In 2013, Canada’s primary aluminium production sector comprised 10 smelters operated by three companies: Rio Tinto Alcan (RTA) with 46% of production capacity; Alcoa with 35%; and Aluminerie Alouette (AA) with 19% (see Table 1-2). Canadian aluminium production, which stood at slightly more than 3.0 Mt in 2013, represented approximately 6% of the world’s production.

Prebaked anode production

In 2013, six of the nine Canadian smelters using prebaked anode technology produced their own anodes in a facility adjacent to the aluminium production (electrolytic reduction) plant (Table 1-2). Only the Laterrière and Baie-Comeau smelters and the Arvida AP60 Technological Centre, obtain their prebaked anodes from an external supplier. The six prebaked anode production plants have an annual production capacity of roughly 1.3 Mt.

Green coke calcining

RTA operates three petroleum coke (green coke) calcining plants at Kitimat, Arvida and Strathcona for the production of calcined coke, a component of green anode paste. The three calcining plants have a combined calcined coke production capacity of more than 500 kt/y (Table 1-2).

Alumina production

In Canada, only RTA operates an alumina production plant, specifically the Vaudreuil plant in Jonquière, which produces approximately 1.5 Mt of metallurgical grade alumina and specialty chemicals (e.g., aluminium fluoride and commercial hydrates) annually, thus supplying a large share of RTA’s network of electrolytic reduction plants.