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1.1.3. Cleaning flue gases from nitrogen oxides

  • Basic methods of flue gas cleaning from nitrogen oxides

    Kotler V.R., Open JSC “VTI”

    In technical literature of the most countries, these methods of nitrogen oxide emission reduction are commonly called "secondary” (secondary measures), as opposed to “primary”, which have been discussed in it. 1.1.2. This name comes from the fact that for economic reasons in boilers, firstly, technological methods of NOx reduction are realized (use of low-NOx burners, staged air or fuel supply, etc.) and only in case of ineffectiveness of the “primary” measures the more expensive “secondary” ones are usually introduced.

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  • 1.1.3.1 Selective Catalytic Reduction (SCR)

    Kotler V.R., Open JSC “VTI”

    This method is currently the most effective tool for NOx emission reduction, applied at the large power boilers. The method has been used for a long time at power plants in Europe, USA and Japan.

    The reducing agent (for that purpose ammonia or urea is usually used) is injected into the flue gas stream before the catalyst. Near the catalyst surface in the temperature range of 170 ... 510°C at a different level of intensity, the reducing reactions, resulting in nitrogen oxide transformation into the molecular nitrogen, occur.

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  • 1.1.3.2. Selective Non-Catalytic Reduction (SNCR)

    Kotler V.R., Open JSC “VTI”

    The second method of cleaning flue gases from NOx, widely spread in the global energy sector and tested in Russia (TP-87 boilers at Tolyatti CHPP) is also a selective (i.e., using ammonia or urea), but non-catalytic reduction of NO to molecular nitrogen. The reduction process takes place without a catalyst in the temperature range, which depends on the reagent use. This approximate range is from 850 to 1100°C.

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