Industrial Experiment on NO_x Reduction by Urea Solution Injection in the Fuel-Rich Zone of a 330 MW Tangentially Pulverized Coal-Fired Boiler

Abstract

The effects of various factors on NO x reduction by urea solution injection in the fuel-rich zone (UIFR) under a reducing atmosphere at high temperature were experimentally investigated in a 330 MW tangentially pulverized coal-fired boiler. The experimental results indicated that the NO x emission of the boiler could be effectively reduced by using the UIFR method, and the NO x reduction efficiency was mostly affected by the operating load of the boiler, the air distribution condition, and the boiler operating oxygen content (BOOC). The higher the load was, the larger the optimal normalized stoichiometric ratio (NSR) and the lower the NO x reduction efficiency became. As compared with the condition of conventional air distribution mode, the reducing atmosphere in the combustion zone could be enhanced under the condition of limiting air distribution (LAD) mode, which thus increased the NO x reduction efficiency of UIFR and reduced the optimal NSR value. A low BOOC could further increase the NO x reduction efficiency of UIFR. When the BOOC was, respectively, reduced to 1.71 and 1.85 vol % under 210 and 240 MW loads, the corresponding NO x reduction efficiencies of UIFR reached 45.3 and 41.3% in the LAD mode, respectively. However, the low BOOC increased the CO emission concentration, which could be avoided by the combined use of UIFR and high-velocity over-fire air. These experimental results can provide guidance for the ultra-low NO x emission of coal-fired boilers.

Optimization of Injection Source Settings for SNCR Numerical Simulation of Low-Water Content Biomass Boilers with Blending

“…The urea solution with a mass concentration of 10% was selected as the reducing agent, and the total flow rate of the reducing agent should be 0.0374 kg/s and NSR = 1. Numerous studies have shown that the NSR between 0.5 and 2 is more appropriate, ,, and the denitrification efficiency is lower for too small an ammonia-to-nitrogen ratio, and the ammonia escape rate increases significantly for too large an ammonia-to-nitrogen ratio. Therefore, in this experiment, the NSR was selected as 0.5, 0.75, 1, 1.25, 1.5, 1.75, and 2 gradient flow rates of reductant injection to investigate the effect of injection volume on reduction efficiency and ammonia escape.…”

Research on structural strengthening technology for regenerative denitration catalysts

“…NO x emissions are a global problem, and flue gases emitted from various industrial processes seriously pollute the environment. 1,2 With China's improved flue gas emission standards 3,4 and the strengthening of air pollution regulations, 3 the focus of NO x treatment has shifted to non-electric industries, mainly the steel, cement, and coking industries. The requirements for the denitration of boiler exhaust gases in various industries are becoming increasingly stringent.…”