Applications of Ultrafine Limestone Sorbents for the Desulfurization Process in CFB Boilers

Abstract

With the stringent emission regulation taking effect, it is difficult for the conventional desulfurization technology in circulating fluidized bed (CFB) boilers to meet the requirements of ultralow SO2 emission. Therefore, in this paper, the application of natural ultrafine limestone, with a Sauter mean diameter of less than 20 μm, was tested by conducting bench-scale, pilot-scale, and commercial-scale experiments to realize highly efficient desulfurization in CFB furnaces. In the past, such small-size limestone was considered unsuitable for CFB boilers. However, as demonstrated by bench-scale results, the desulfurization performance was clearly superior to that of coarse limestone, especially at low SO2 concentrations. In a 3 MWth pilot-scale CFB boiler, the ultrafine limestone exhibited competent desulfurization efficiency to that of the coarse limestone but clearly less significant catalytic effects on NOx formation. As revealed by field tests in four commercial-scale CFB boilers, when high-efficiency cyclones were applied to CFB boilers, the mass inventory of ultrafine particles was significantly increased and the residence time would be extended accordingly; thus, the ultrafine limestone can be used to achieve high desulfurization efficiency and even ultralow SO2 emission with a favorable Ca/S ratio. Furthermore, a technical roadmap was drawn for the cost-effective control of SO2 emission.

Construction of Confined Bifunctional 2D Material for Efficient Sulfur Resource Recovery and Hg2+ Adsorption in Desulfurization

“…Nevertheless, the rapid depletion of limestone resources and large output of low-grade gypsum solid waste cause the inefficiency of sulfur resource recovery. Meanwhile, the single desulfurization system releases massive greenhouse gas CO 2 during the SO 2 absorption treatment. , To this extent, wet magnesia desulfurization with low CO 2 emissions seems to be an alternative and sustainable approach to reclaim sulfur resource from the slurry regarding its great potential to yield valuable MgSO 4 as fertilizer or industrial raw material. − …”

“…Meanwhile, the single desulfurization system releases massive greenhouse gas CO 2 during the SO 2 absorption treatment. 3,4 To this extent, wet magnesia desulfurization with low CO 2 emissions seems to be an alternative and sustainable approach to reclaim sulfur resource from the slurry regarding its great potential to yield valuable MgSO 4 as fertilizer or industrial raw material. 5−7 However, the slow oxidation rate of MgSO 3 always leads to a low sulfate concentration approximately 10 wt %, resulting in more than three-quarters of water in the slurry that needs to be evaporated to crystallize sulfate due to the high solubility of MgSO 4 •7H 2 O (equaling to approximately 32 wt % at 45 °C).…”

Study on economic operating mode for combined desulfurization system of circulating fluidized bed unit

“…However, with the environmental concerns grow, the SO 2 emission standards for CFB boilers have been tightened. The ultralow emission standard in China requires SO 2 emission cannot be higher than 35 mg/Nm 3 [5,6]. Unfortunately, it is difficult to realize the ultralow SO 2 emission by desulfurization in furnace for most CFB boilers, so the FGD systems are installed [7].…”

Dynamic control method of particle distribution uniformity in the rolling circulating fluidized bed (RCFB)

“…However, due to high cost and safety problems, they do not use in real ships. As a rolling circulating fluidized bed (RCFB) has many advantages such as high exhaust gas treatment capacity, high heat transfer efficiency and low manufacturing cost (Wahyudi et al, 2016), thus, the RCFB is usually used as a new treatment device for the ship exhaust gas, There are many calcium carbonate (CaCO 3 ) particles in the RCFB which can effectively remove the harmful substances from the exhaust gas and achieve desulfurization (Cai et al, 2019;Xia & Peng, 2007). Due to the influence of wind and waves on the ship, the RCFB encountered with different amplitude and CONTACT Tong Zhao tongzhao@xaut.edu.cn period.…”