CFD-modelling of Selective Non-Catalytic Reduction of NO<SUB align=right>x in grate-kiln plants

Abstract

The overall goal of this project is to find out if selective non-catalytic reduction (SNCR) technologies can be used in grate-kiln plants for NO x reduction. The technique has, to the best knowledge of the authors, never been used in this context before despite that it is commonly used in cement and waste incineration plants.A Computational Fluid Dynamic model of parts of a real grate was created and numerical simulations with a commercial code was carried out solving the flow field. A model for spray injection into the grate was then included in the model enabling a study of the overall mixing between the injected reagent droplets and the NO x polluted air. The simulations show promising results for SNCR with urea but not with ammonia.

Numerical simulation of SNCR (selective non-catalytic reduction) process in coal fired grate boiler

“…Quite recent work reports examination of the effect of urea injection arrangements and velocities on NO x reduction and NH 3 slip in a coal fired stoker [1]. Most of the numerical studies consider biomass or waste fired stokers [2e5], grate-kiln plants [6] or pilot scale experiments [7e10]. Papers reporting CFD validation studies of SNCR chemical kinetic model based on pulverised coal boilers have also been published [11,12].…”

Modelling heat transfer during flow through a random packed bed of spheres

“…In the work by Burström et al [4,5] a typical plot of I at the inlet of the bed in the PH and TPH-zone yielded a variation up Fig. 22 Snap shots of the temperature distribution as derived from the discrete model for uneven temperature to 80% as can be seen in Fig.…”

“…Previous work has been conducted to study fluid dynamic phenomena in the traveling grate zone of a grate-kiln plant [4,5] as well as in rotary kiln [23][24][25]. Of special interest is how the incoming process gas, leakage, and the detailed composition of the pellet bed influence the heat transfer through the bed.…”

The grate-kiln induration machine - history, advantages, and drawbacks, and outline for the future

“…This material can also be deposited as stalagmite structures in the kiln ( Figure 5) or as accretions in the transfer chute. Air flows tend to be turbulent, especially in the transfer chute (Burström et al, 2010), as this is the geometrical bottleneck of the induration machine. A thin layer of deposit on the surface can act as protection for the lining, but when these deposits increase in thickness they contribute to mechanical strain.…”