Experimental study of SO2 emissions and desulfurization of oxy-coal combustion in a 30 kWth pressurized fluidized bed combustor

Abstract

Pressurized oxy-fuel combustion (POFC) has attracted wide attention due to its potentials of high efficiency and low cost in CO2 capture. Compared with numerical simulation and system analysis, there are few experimental studies about POFC. In order to investigate the SO2 emissions and desulfurization behaviors of limestone under continuous fuel-feeding POFC conditions, a series of oxy-coal combustion experiments were conducted with a 30 kWth pressurized fluidized bed combustor. The results showed that the SO2 emission was almost independent of combustion pressure and excess oxygen coefficient, while it was higher in air than in O2/CO2 atmosphere because less sulfur was retained by the coal ash. Although the higher CO2 partial pressure caused by an increase in combustion pressure from 0.1 MPa to 0.4 MPa had negative effects on the calcination of limestone and inhibited the indirect desulfurization, the higher combustion pressure was beneficial to improve the direct desulfurization efficiency. An increase in combustion temperature from 850 o C to 950 o C significantly improved the desulfurization efficiency of limestone with both atmospheric and pressurized oxy-coal combustion. SEM images were obtained and used to show the surface morphology of limestone products under different combustion conditions, which was helpful to the understanding of the desulfurization behaviors of limestone.

Experimental Study of SO2 Emission and Sulfur Conversion Characteristics of Pressurized Oxy-Fuel Co-combustion of Coal and Biomass

“…It is noted that the sulfur content in the fuel ash increases first and then decreases with the increases of M b and the maximum value is obtained at 50% M b . The sum of sulfur in the form of SO 2 and sulfur in the fuel ash is between 84 and 95% in all M b experiments, and sulfur in other forms may include sulfur absorbed by moisture and converted into gaseous SO 3 20 and sulfur in uncollected fly ash. 36 Figure 6 shows the chemical composition in the fuel ash of different M b 's obtained by XRF.…”

“…Although some studies about theoretical calculation and simulation of the POFC system had been conducted, there were only few experiments on POFC. Some researchers had carried out combustion experiments on pressurized oxy-coal combustion in pressurized thermogravimetric analyzers, − tube furnaces, pressurized flow reactors, and fluidized beds. − Zan et al discovered that higher system pressure inhibited NO emission in a pressurized oxy-fuel tube furnace. Liang conducted experiments of pressurized oxy-coal combustion in a pressurized flow reactor to investigate nitrogen transformation.…”

“…Lasek et al , studied the emission of SO 2 , NO, and N 2 O in a pressurized oxy-fuel bubbling fluidized bed, and the experimental results showed that SO 2 , NO, and N 2 O emissions decreased at elevated pressures. Pang et al carried out oxy-coal combustion experiments in the pressurized fluidized bed to investigate the effect of reactor pressure on SO 2 emission characteristics, and the experimental results showed that higher reactor pressures inhibited SO 2 emissions.…”

“…Besides, the generated SO 2 during the co-combustion process will induce boiler corrosion and cause pollution to the environment. High concentrations of SO 2 in the flue gas also have a negative influence on CO 2 capture . Some researchers had carried out relevant studies on the SO 2 emission characteristics of co-combustion in the atmospheric oxy-fuel atmosphere. − Huang et al conducted co-combustion experiments in the tube furnace, which showed that the increase of oxygen concentration in the oxy-fuel atmosphere promoted SO 2 emissions and conversion rate of fuel sulfur to SO 2 .…”

Life-Cycle Environmental and Economic Assessments of the Oxy-coal Combustion System Combined with a Pressurized Circulating Fluidized Bed and the Supercritical CO2 Brayton Cycle

“…Meanwhile, because of the elevated combustion pressure, the volume of the flue gas is reduced, which results in small components and a possible reduction in the capital cost . By elevating the combustion pressure, some of the pollutants are reduced according to the relevant research, and the burnout rate of coal is improved. − Except for pressurized combustion, the use of supercritical CO 2 (S-CO 2 ) has also been regarded as an ideal way to increase the cycle efficiency because of the special characteristics of S-CO 2 , e.g., high fluid density, low viscosity, and high heat capacity over supercritical pressure and temperature. To date, there are numerous works concerning the system layouts, , optimum parameters, pressure drops, and bottoming cycles , in the S-CO 2 Brayton cycle, which demonstrate the superiority against the steam Rankine cycle.…”