Trace elements in co-combustion of solid recovered fuel and coal

Abstract

Trace element partitioning in co-combustion of a bituminous coal and a solid recovered fuel (SRF) was studied in an entrained flow reactor. The experiments were carried out at conditions similar to pulverized coal combustion, with SRF shares of 7.9 wt.% (wet basis), 14.8 wt.% and 25.0 wt.%. In addition, the effect of additives such as NaCl, PVC, ammonium sulphate, and kaolinite on trace element partitioning was investigated. The trace elements studied were As, Cd, Cr, Pb, Sb and Zn, since these elements were significantly enriched in SRF as compared to coal. During the experiments, bottom ash was collected in a chamber, large fly ash particles were collected by a cyclone with a cut-off diameter of~2.5 μm, and the remaining fly ash particles were gathered in a filter. It was found that when coal was co-fired with SRF, the As, Cd, Pb, Sb and Zn content in filter ash/cyclone ash increased almost linearly with their content in fuel ash. This linear tendency was affected when the fuels were mixed with additives. The volatility of trace elements during combustion was assessed by applying a relative enrichment (RE) factor, and TEM-EDS analysis was conducted to provide qualitative interpretations. The results indicated that As, Cd, Pb, Sb and Zn were highly volatile when co-firing coal and SRF, whereas the volatility of Cr was relatively low. Compared with coal combustion, co-firing of coal and SRF slightly enhanced the volatility of Cd, Pb and Zn, but reduced the volatility of Cr and Sb. The Cl-based additives increased the volatility of Cd, Pb and As, whereas addition of ammonium sulphate generally decreased the volatility of trace elements. Addition of kaolinite reduced the volatility of Pb, while the influence on other trace elements was insignificant. The results from the present work imply that trace element emission would be significantly increased when coal is co-fired with SRF, which may greatly enhance the toxicity of the dusts from coal-fired power plant. In order to minimize trace element emission in co-combustion, in addition to lowering the trace element content in SRF, utilizing SRF with low Cl content and coal with high S and aluminosilicates content would be desirable.

Low temperature combustion of organic coal-water fuel droplets containing petrochemicals while soaring in a combustion chamber model

“…Thus, it is appropriate to conduct model tests, while feeding fuel in air jet into the combustion chamber or ensure a soaring mode in the oxidizer flow. The traditional and most common approach for defining ignition and combustion characteristics is based on suspending fuel droplets at the low-inertia thermocouple junction, wires or non-combustible (usually ceramic) filaments [12][13][14][15][16]. One of the major drawbacks of this method is the presence of heat sink over the thermocouple junction, wire or a ceramic filament [12][13][14][15][16].…”

“…At present, quite a large group of countries (for example, China, Japan, Russia, USA, and others) has increased interest in the use of alternative fuels (based on coal-water technologies) instead of traditional (coal, fuel oil) for various power plants. In particular, the number of research papers has increased significantly in the field of creation and application of coal-water fuel (CWF) in large and small power industries [1][2][3][4][5][6][7][8]. The interest in using CWF in the energy sector is due to reasonable (quite substantial) benefits, including: -the possibility of involving various low-grade fuels (e. g., high-ash coal) and liquid flammable substances (waste oil, oil-water emulsion), the raw material base of which is constantly replenished [9][10][11], -the improvement of the environmental performance of boiler plants on emissions (e. g. SO x and NO x content in flue gases) compared to the burning of traditional fuels (especially coal), and -the improvement of economic performance of heat and electricity production through the use of cheaper source of fuel.…”

Behavior of Pb During Coal Combustion: An Overview

“…At 700-900 • C, bauxite was the best adsorbent for Pb if PVC was present (in comparison to Al 2 O 3 and kaolinite); but if NaCl was used, its retention efficiency was the worst. If Pb was not converted to chlorides (low or negligible amount of NaCl/PVC), a high retention efficiency can be obtained by kaolinite [49], for which a high temperature is recommended (t > 1000 • C) [24,50,51]. If SiO 2 is to be used as a Pb adsorbent, the conversion of PbO to PbCl 2 (e.g., by organic Cl below 350 • C) can hinder Pb retention on SiO 2 because PbO retention on SiO 2 is more efficient than that of PbCl 2 [52].…”

Mathematical Modeling of Ignition of Droplets of Coal-Water Slurry Containing Petrochemicals Using Ansys Fluent

“…During the last 25-30 years the technologies of coal-water slurries are rather actively developed worldwide [4,5]. The main objectives that can be achieved by using coal-water slurries (CWS) and coal-water slurries containing petrochemicals (CWSP) [6,7] are, primarily, reduction of emissions of sulfur and nitrogen oxides, fly ash as compared to pulverized coal, as well as involvement of low-grade coals (even fire dangerous lignite) and a variety of petroleum products (waste motor and industrial oils, sludge, etc.)…”