Environmentally Friendly Techniques

  • Low temperature SNCR by activated ammonia generated by atmospheric pulsed plasma.［PDF01］
  • Low temperature SNCR by activated ammonia generated by 172 nm vacuum ultra violet (VUV).［External Link］

Background ＆ Objectives

Removal of nitrogen oxides (NOx) from flue gas emitted from stationary combustors is desirable for environmental pollution control and public health. Selective catalytic reduction (SCR), an efficient treatment technology, has been used world-wide for NOx removal in large-scale combustors such as coal-fired power plants. In SCR systems, nitric oxide (NO) reacts with injected molecular ammonia in the presence of a catalyst and oxygen at a temperature of around 350 degC at which NO converts to molecular nitrogen and water. A drawback of SCR systems in application to waste incinerators is that they are particularly costly because frequent replacement of the catalyst is required owing to catalyst poisoning by sulfur dioxide, plugging and erosion by ammonium bisulphate, and deposition of ash, amongst others. Furthermore, most existing waste incinerators do not have enough free space for installing an SCR system. For waste incinerators, another possibility for NOx removal is to adopt selective non catalytic reduction (SNCR) techniques. However, temperature of waste incinerators exit is between 700 degC and 800 degC, which is outside the temperature window of conventional SNCR. Therefore, it is essential for waste incinerators to shift the temperature window for incorporating lower temperatures. 　The aim of the research is to find an alternative method of producing effective chemical species for NO removal without catalyst. A pulsed plasma or a 172 nm VUV (vacuum ultraviolet) excimer lamp is employed as the excitation source for molecular ammonia. SNCR of NO by activated ammonia injection has not been examined to date, making this research unique.

The novel method of DeNOx for furnaces.

A reactor using atmospheric pulsed plasma

A photochemical reactor using 172 nm VUV.

Reaction mechanisms of DeNOx by activated ammonia injection.