Co-Combustion of Tannery Sludge in a Bench-Scale Fluidized-Bed Combustor: Gaseous Emissions and Cr Distribution and Speciation

Abstract

In this study, 11 coal mono-combustion tests and four co-combustion tests of coal and tannery sludge were conducted on a 35 kW fluidized-bed combustor. The combustion behavior and emission characteristics of the fuels were investigated on a bubbling fluidized bed (BFB) and a circulating fluidized bed (CFB). The effects of an excess air ratio, primary air rate, secondary air ratio, and fuel type on flue gas emissions were studied. The results showed that the fluidization status and temperature distribution had direct influences on CO emission. Sufficient fluidization and high temperature effectively reduced CO emission. NO x emission was relatively sensitive to the excess air ratio and increased with increasing excess air ratio. By comparing BFB and CFB, we found that CFBs have an advantage in optimizing combustion and controlling emissions by enhancing mixing and increasing freeboard temperatures. The Cr speciation and distribution among different ash types were extensively investigated in four co-combustion tests. The results showed that the distribution modes of Cr in BFBs and CFBs were different and determined by separate fluid dynamics modes of sludge ash particles in the combustor. The extent of Cr oxidation in ash in CFB tests was higher than that in BFB tests, particularly for bottom ash and heat exchanger ash, due to longer residence times in high-temperature regions.

Study of Sewage Sludge/Coal Co-Combustion by Thermogravimetric Analysis and Single Particle Co-Combustion Method

“…4,5 SS could be used as a kind of renewable fuel for electricity generation in the existing coal-fired power plants. 6,7 Unfortunately, the moisture content of the dewatered SS is about 73− 84%, which makes the transportation of dewatered SS risky and high cost. 8 Moreover, the high moisture content is detrimental to ignition and combustion.…”

Characterization of Biocrude Produced by Hydrothermal Liquefaction of Municipal Sewage Sludge in a 500 mL Batch Reactor

“…In the context of biomass exploitation for energy production, the main thermochemical routes include pyrolysis and oxypyrolysis, 2,3 torrefaction, 4 gasification, 5 or combustion. 6 Application to biomass with large moisture content may be hampered by the need for an energy-intensive drying stage. 7 Hydrothermal liquefaction (HTL) represents a promising process for the conversion of wet biomass, such as sewage sludge, into liquid fuels.…”

“…Scientific research focuses on the development of a broad portfolio of sustainable technologies to meet ever-growing energy demand. In the context of biomass exploitation for energy production, the main thermochemical routes include pyrolysis and oxy-pyrolysis, , torrefaction, gasification, or combustion . Application to biomass with large moisture content may be hampered by the need for an energy-intensive drying stage .…”

Multifunctional Additives for NOX Abatement in Fluidized Bed Biomass Combustion

“…7 Several countermeasures have been proposed to deal with NO X emissions and bed agglomeration. are air staging, 8,9 temperature adjustment, 10 selective noncatalytic reduction (SNCR), 11 lowering excess air, 12 reburning (fuel staging), 13,14 flue gas recirculation, 15 and fuel blending. 16,17 Hybrid systems such as SNCR, air staging, 11 and reburning combined with SNCR (advanced reburning) 18,19 have also been investigated.…”

“…Several countermeasures have been proposed to deal with NO X emissions and bed agglomeration. Primary measures employed for NO X emission control in fluidized bed combustion are air staging, , temperature adjustment, selective non-catalytic reduction (SNCR), lowering excess air, reburning (fuel staging), , flue gas recirculation, and fuel blending. , Hybrid systems such as SNCR, air staging, and reburning combined with SNCR (advanced reburning) , have also been investigated. In comparison, countermeasures against bed agglomeration include the use of alternative bed materials, ,, additives, , cocombustion, , and biomass pretreatment. , Techniques for overcoming these two issues normally target each area independently.…”