Air

Sulphur dioxide
(continued)

The electricity industry’s share of Canada’s sulphur dioxide emissions is about 20 per cent. Most of these emissions are from Alberta, Saskatchewan, Ontario, Nova Scotia and New Brunswick, where fossil fuel generation is the primary or an important source of electricity.

Power companies’ efforts to reduce sulphur dioxide emissions have focused largely on using advanced emission control equipment and improving operating practices:

• scrubbers
  Some power plants have installed flue gas desulphurization units (or “scrubbers”) to remove sulphur from exhaust gases going up plant stacks. In most scrubbers, limestone is mixed with water and sprayed into the gases. The limestone and sulphur react to capture the sulphur, producing a removable gypsum waste byproduct. Although scrubbers can reduce sulphur dioxide emissions by more than 90 per cent, they are expensive and require considerable energy to operate.
  
  
• fuel combustion technologies
  Power companies are also exploring the use of fluidized bed combustion technology. Here, crushed coal particles float inside the boiler on upward-blowing jets of air. The boiler mixes limestone with the coal to capture sulphur and burns coal at lower temperatures to reduce nitrogen oxide emissions.
  
  
• low sulphur coal
  Burning coal with low sulphur content is another way that power plants reduce sulphur dioxide and nitrogen oxide emissions from coal combustion. Coal reserves in Western Canada tend to have lower sulphur content (less than 0.5 per cent) than coal found in Eastern Canada and coal imported from the U.S. (three per cent and higher).
  
  
• coal cleaning and blending
  Power companies use innovative coal grinding and blending processes to mill different types of coal before they are burned as fuel. This results in better combustion performance, higher unit output and, potentially, lower sulphur dioxide emissions. Coal cleaned by “washing” is also a standard practice in industry. It reduces emissions of ash and sulphur dioxide when coal is burned.