Gas/Particle Flow Characteristics, Combustion and NO_x Emissions of Down-Fired 600 MW_e Supercritical Utility Boilers with Respect to Two Configurations of Combustion Systems

Abstract

Using a phase-Doppler anemometry (PDA) on a two-phase small-scale model for a down-fired 600-MWe supercritical utility boiler, experiments were conducted to compare the gas/particle flow characteristics between the prior and newly designed deep-air-staging combustion systems. The distributions of mean velocity, particle volume flux, and particle number concentration along several cross sections were compared between the two combustion systems, in addition to the decay and trajectory of the downward gas/particle flow. With the prior combustion system, asymmetric gas/particle flow characteristics appear in the furnace, with the gas/particle flows in the front-half of the furnace penetrating greatly further and occupying much more furnace volume than those in the rear-half of the furnace. The longitudinal gas/particle velocity components, particle volume flux, particle number concentration, decay curve, and trajectory of the downward gas/particle flow all display a severe asymmetric pattern along the furnace center. In applying the deep-air-staging combustion technology as a replacement for the prior art, the original asymmetric gas/particle flow characteristics that are seen in the furnace all develop a symmetric pattern. Industrial-sized measurements performed within the full-scale furnace uncovered that asymmetric combustion characterized by gas temperatures being much higher near the rear wall than near the front wall, developed in the boiler with the prior art. In comparison with the boiler with the prior art, the newly designed boiler applying the deep-air-staging combustion system achieved perfectly symmetric combustion, NO x emission reduction by around 40%, and large improvement in burnout.

Low-NOx and High-Burnout Combustion Characteristics of a Cascade-Arch-Firing, W-Shaped Flame Furnace: Numerical Simulation on the Effect of Furnace Arch Configuration

“…That is, gas temperatures are symmetrical in the front- and rear-half sides and meanwhile, increase initially but then decrease along the flame travel (penetrating in turn the furnace zones corresponding to the typical ports 1–4). The reported symmetrical W-shaped flow-field formation with MIMSCT explains here the symmetrical combustion occurrence. The mentioned increase-to-decrease temperature trend along the flame travel is attributed to the fact that the furnace zones located at typical ports 1–4 (Figures and ) correspond in turn to the burner-outlet zone, preceding stage combustion zone, primary combustion zone with staged air aiding combustion, and upper part of the hopper zone where the flame begins to turn upward.…”

Multi-injection multi-staging combustion mechanistic studies and down-fired boiler technology

“…图 9 (网络版彩图)英巴技术和多次引射分级技术下炉内气 固两相流轨迹 [44] Figure 9 (Color online) Downward gas/particle flow trajectories within the furnace with respect to MBEL technology and multiinjection multi-staging combustion technology [44].…”

Numerical and Experimental Investigations on Reducing Particle Accumulation for SCR-deNOx Facilities

“…Hex/Wedge and Tet/Hybrid grids are used to demonstrate the meshing geometry. For simplification, several assumptions are made for the calculation: (1) the model is considered to be adiabatic since the SCR-deNO x facility is covered with an aluminum silicate blanket, which works as the thermal insulator, (2) no chemical reaction is introduced, (3) the gas flow is considered to be incompressible fluid, (4) the ash particles are treated as inert particles, and (5) the diameters for 99.50% of the ash particles are larger than 2.50 × 10 −3 mm [25,26,29].…”