Experimental Investigation of Nitrogen Species Distribution in Wood Combustion and Their Influence on NO_x Reduction by Combining Air Staging and Ammonia Injection

Abstract

The formation of the nitrogen species HCN, NH 3 (N-intermediates), and NO out of fuel-bound nitrogen has a major influence on NO chemistry. Experiments have been carried out on an entrained flow reactor with pulverized wood as fuel. Staged combustion establishes a fuel-rich primary zone, where both N-intermediates and NO exist. The introduction of NRP as the ratio of the N-intermediates to NO offers a parameter that describes the nitrogen distribution in the primary zone, whereas TFN describes the overall amount of nitrogen. Air staging is an effective method for NO x reduction; the main controlling parameter is the primary air ratio, which defines both NRP and TFN. In fuel-rich conditions, NRP exceeds 1; with increased oxygen availability and temperature, the N-intermediates are depleted and NO is formed (NRP < 1). Thus, the NRP can be increased by adding NH 3 . Conventional SNCR is strongly temperature-dependent; hence, with increased temperatures, the best operation point shifts to lower air ratios. A combination of air staging and ammonia injection directly in the primary zone furthers NO x reduction, as long as it is realized in almost stoichiometric conditions. Since the reduction efficiency increases at high temperatures, the technology is called selective high temperature reduction.

Impact of the Multihole Wall Air Coupling with Air Staged on NOx Emission during Pulverized Coal Combustion

“…By this means the fuel nitrogen was more early and abundantly released to generate a large amount of reducing species (HCN, NH 3 , etc.) . As a result, the NOx emission was reduced.…”

“…By this means the fuel nitrogen was more early and abundantly released to generate a large amount of reducing species (HCN, NH 3 , etc.). 38 As a result, the NOx emission was reduced. Otherwise, only a small amount of reducing species was released in the initial stage of combustion, so the NOx emission may be higher than that in the finer pulverized coal case.…”

Chemical Model for Thermal Treatment of Sewage Sludge

“…For all thermal treatment processes, the varying feedstock is one of the key challenges. Here, the most relevant properties are the moisture content, due to the high energy demand for drying [6,12], the ratio of volatile components and ash-since this is correlated to the lower heating value of the sewage sludge [13]-and the content of elements involved in emission formation processes, that is, nitrogen, sulfur and chlorine [14][15][16][17][18]. To handle this challenging fuel, often sewage sludge is mixed with other solid fuels, such as biomass wastes, in co-gasification [19] and co-incineration in the cement industry [4,20].…”

Study on Double-Layer Ignition Sintering Process Based on Autocatalytic Denitrification of Sintering Layer

“…Meanwhile, sintering, as one of the most polluting processes in steel production, accounts for about 50% of the total NO x emissions of iron and steel production [6,7]. According to the formation mechanism, NO x can be divided into three types: thermal NO x , prompt NO x , and coal NO x [8,9]. In the sintering process, NO x mainly comes from coal combustion, accounting for about 80%-90% of the total NO x emissions from the sintering machine [10].…”