OCR Text |
Show as an appendix to the published guideline. A future guideline for lime kilns will also be developed subsequent to further research with the lime industry. Regional or provincial regulatory authorities could decide to impose stricter standards in response to local air quality problems. Principles that were considered to be important were those of pollution prevention, energy efficiency, cost-effectiveness and a comprehensive view towards minimizing various emissions to reduce air pollution and greenhouse gases. The National Emission Guideline states that emissions from large new natural gas or coal-fired cement kilns ( capacity >1500 tonne/day) should not exceed 2.3 kg of N O x per tonne of clinker production, based on a monthly average time period. The monthly averaging period w a s chosen to avoid issues associated with the transient nature of the hourly/daily emissions profile of most kilns. Special permitting could be done for the use of other fuels such as oil or petroleum coke, or for the use of alternative fuel mixes including landfill gas. For an existing large cement kiln, the New Source Guideline limits stated below shall apply when a modification results in a 25 percent increase in permitted kiln capacity. For modifications associated with one-time lesser increases in permitted capacity, a program to improve performance should take advantage of cost-effective technologies to achieve feasible emission reductions. The resulting emission levels on these modified kilns do not necessarily have to meet those limits stated for n e w kilns. For kilns smaller than 1500 tonnes per day, or where there are opportunities to improve environmental performance and energy efficiency on kilns for which major modifications are planned, emission rates and control methods can be evaluated in close consultation with the appropriate regulatory authorities. The reduction of clinker production, or the offset of other emissions, is also recognized as a strategic option for the industry and for regulatory bodies to deal with permitting issues on existing or new plants. Where a plant proposes to reduce clinker production by the addition of additives such as fiyash or slag, a higher N O , limit could be considered. This would be based on the portion of clinker produced from primary raw materials, excluding the additives. This allowance would serve to increase the kg/tonne of clinker emission level for the kiln, and to recognize a reduction in overall net emissions for a given amount of cement produced. A similar approach was introduced to credit NO, emissions if waste heat from the stack exhaust or clinker cooler was used for any other heating processes not normally associated with kiln operation. Emissions of Other Pollutants The cement industry has previously been mostly concerned with other emissions involving particulate matter, addressed in a 1974 regulation. It had been agreed to in the consultation process that a comprehensive evaluation of other emissions would be included to the extent which would be practical. W h e n considering the installation of process modifications to reduce emissions of NOx, other pollutants should be minimized to avoid adverse environmental impacts, while maintaining acceptable clinker quality. The Guideline has a revised particulate limit of 0.2 kg per tonne of clinker (about 90 mg/m3) from the stack, and 0.1 kg per tonne from the clinker cooling system. N e w kiln systems should be designed, and raw materials selected, to minimize S 0 2 and C O emissions while remaining in compliance with N O x guidelines. 19 |