Development of Sulfur Release and Reaction Model for Computational Fluid Dynamics Modeling in Sub-Bituminous Coal Combustion

Abstract

Pulverized coal-fired boilers applying low-NO x combustion technologies commonly suffer from high-temperature corrosion due to high-concentration H 2 S. Accurate prediction of sulfur species, especially H 2 S, is of great importance for the optimized design and operation of boilers and burners to reduce such problems. The sulfur release characteristics from coal and subsequent sulfur species gas-phase reaction mechanism are two critical steps controlling sulfur species evolution. In this study, first, a global sulfur species gas-phase reaction mechanism consisting of 10 reactions is proposed based on a detailed mechanism considering hundreds of elementary reactions. Kinetic parameters of the global mechanism are determined via a rigorous mathematical optimization process. Second, the sulfur release characteristics during coal pyrolysis and char burning of five kinds of sub-bituminous coals are investigated in a drop tube furnace (DTF). Equations describing the relationship between sulfur release and coal consumption are proposed and fitted to experimental data. Third, a novel integrated sulfur species prediction model is developed by implementing the global sulfur species gas-phase reaction mechanism and the sulfur release submodel into computational fluid dynamics (CFD )software, Fluent. Finally, combustion experiments of three kinds of sub-bituminous coals are conducted in the DTF at different temperatures with different stoichiometric ratios to validate the developed model. The results show that the prediction errors of sulfur species, including SO 2 , H 2 S, and COS, are within ±25%, which indicates that the novel sulfur species prediction model is of great assistance for actual engineering applications.

Study on the Migration Characteristics of Sulfur and Nitrogen during Combustion of Oil Sludge with CaO Additive

“…However, the following reasons could explain the above phenomena. H 2 S dissolved in OS was first evaporated by heat and then partially oxidized to SO 2 . Under the local reduction atmosphere on the surface of OS particles, H 2 S and S vapor were first produced after the sulfur side chain (−SH−) and sulfur ring chain (−S−) in sulfur-containing organic compounds were broken by heat All four sulfur-containing gases can be oxidized to SO 2 during combustion as soon as they contacted with oxygen, and these reaction processes can be described as follows SO 2 can be reduced during combustion of OS, resulting in the secondary generation of COS, CS 2 , and H 2 S. , These reduction reactions can be expressed as follows In a reductive atmosphere, various sulfur-containing gases could also be converted into each other during combustion of OS. ,− The main transformation reactions can be reflected as In addition, it can be seen from Figure a–d that the four kinds of sulfur-containing gases decreased significantly with the increase of the Ca/S ratio, indicating that CaO had a significant role in sulfur fixation. SO 2 and H 2 S can be directly fixed by CaO .…”

“…All four sulfur-containing gases can be oxidized to SO 2 during combustion as soon as they contacted with oxygen, and these reaction processes can be described as follows …”

“…In a reductive atmosphere, various sulfur-containing gases could also be converted into each other during combustion of OS. ,− The main transformation reactions can be reflected as …”

“…MS Analysis. According to the standard mass spectra of gases, the main sulfur-containing and nitrogen-containing gases produced by combustion were characterized, including hydrogen sulfide (34), carbonyl sulfide (60), sulfur dioxide (64), carbon disulfide (76), ammonia (17), hydrogen cyanide (27), nitric oxide (30), and nitrogen dioxide (46). The evolution of these gaseous products during combustion is shown in Figure 4.…”

Liquid Hydrocarbons Production by the Steam Gasification of Used Tires: Energy Characteristics and Environmental Sustainability

“…Additionally, since the fuel was sprayed into smaller droplets (spark-like satellites) during microbursts, the reaction contact surface between the formed fuel droplets with CO and H2 increases, resulting in promotion of the reduction reaction of sulfur and nitrogen oxide: SO2 + 3CO → COS + 2CO2 [50], NO + CO → N + CO2 [51].…”