Decreasing the NO x Emissions at Coke Plants
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Decreasing the NOx Emissions at Coke Plants V. I. Rudykaa, *, S. A. Kravchenkoa, **, S. J. Abdullina, ***, S. J. Stelmachenkoa, ***, and O. I. Makeia, *** a
Giprokoks, Kharkov, Ukraine *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected] Received January 22, 2020; revised January 22, 2020; accepted February 14, 2020
Abstract—Various approaches to decreasing toxic emissions of nitrogen oxides at coke plants are described: stepwise air supply; recirculation of smokestack gases; and selective catalytic and noncatalytic reduction of the nitrogen oxides. Keywords: nitrogen oxides, coke batteries, NOx, emissions, heat recovery, vertical channels, simulation, combustion, smokestack gases, recirculation, stepwise air supply, selective catalytic reduction, selective noncatalytic reduction DOI: 10.3103/S1068364X20050051
In recent years, requirements on the toxic content of atmospheric emissions from industrial enterprises have been tightening. The coke battery is a major source of toxic emissions. The combustion of gas in the vertical channels of the heating walls in coke batteries forms NOx (that is, a mixture of the nitrogen oxides NO and NO2). Already, the NOx content in the combustion products at many coke batteries is out of compliance with environmental standards. In its ongoing efforts to lower the environmental impact of coke plants, Giprokoks continually develops new approaches to minimizing the NOx content in coke-battery combustion products. BASIC APPROACHES In the present work, we consider the minimization of NOx emissions both by modifying the coke batteries and by means of additional external devices. We may identify two classes of methods: (1) decrease in NOx formation in the combustion zone; (2) decrease in the NOx content of the exhaust gases ahead of the smokestack. DECREASE IN NOx FORMATION WITHIN THE COMBUSTION ZONE NOx formation is greatest in the vertical channels of the coke batteries, according to the results in [1–13]. The NOx is formed by a thermal mechanism at high
temperature and high O2 concentration. Hence, decreasing the temperature in the vertical channels may decrease the NOx content in the combustion products. One approach is to decrease the temperature and oxygen content in the active combustion zone. That is possible by recuperation of the combustion products and stepwise supply of air or heating gas. The combination of these two measures within a single design permits 55–80% decrease in NOx content. In specialized research, numerical modeling by means of ANSYS FLUENT software is used to study flame propagation over the height of the vertical heating channel and the regions of NOx formation. Vertical channels developed for 70.5-m3 coke ovens are considered. The air is supplied at heights of 0, 2.00, and 3.65 mm from the channel base. Coke-oven gas is used for heating. Table 1 presents the combination of different approaches to decreasing the NOx content. Numerical experiments show that the temperature is greatest between the bottom of
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