Correlating Flue Gas Composition with Ash Deposit Mineralogy and Morphology during Combustion of Zhundong and its blends with an oil-shale semi-coke in a Circulating Fluidized Bed
This paper tries to correlate the flue gas composition with ash deposit mineralogy and morphology for understanding gas-solid interactions within the deposits.Zhundong lignite (ZD, <3 mm) and its blends with an oil shale semi-coke (SC, <3 mm) of high aluminosilicate at SC blending ratios of 10 wt % or 20 wt % were combusted in a bench scale CFB combustor.Two air-cooled probes installed in the furnace chamber (P1) and at the cyclone outlet (P2) were used to simulate ash deposition.The flue gas composition including O2, CO, NOx,and SO2 around the probes was measured in-situ by using an ECOM-J2KN gas analyzer.Both fly ash and the ash deposits on these probes (denoted as P1S and P2S) were collected and analyzed by using XRD and SEM-EDX.Results show that when ZD was burned alone, the composition of O2, CO, NOx, and SO2 around P1 were 3.2%, >5000, 394, and 871 mg m3, respectively, which around P2 became 2.8%, 542, 377, and 834 mg m3, and turned into 2.7%, 281,358, and 803 mg m-3 at tail flue.This indicates that CO was quickly depleted in top of furnace and separator, which is consistent with the alteration of O2.When 10% or 20% of SC were added, O2,NOx, SO2 concentration around P1 increased to 5%, 727, and 1385 mg m-3, while CO decreased to 1027 mg m-3,due to the reduction of the incomplete combustion as a result of the addition of SC with low calorific.Moreover,SO2 reduced to 637 mg m-3 around tail flue.XRD analysis showed that the fly ash particles were composed of agglomerates rich in CaSO4, Na2SiO3, Na2Si2O5, and metallic oxide (e.g.CaO, MgO), while Na/Ca sulphates were of high contents in the sintered or melted deposits particles on P1S, indicating that gas-solid reaction between SO2 in flue gas and the deposited Na-bearing minerals occurred on the probe surface.Moreover, the P2S deposits was presented of a sintered cone-shape layer rich in Ca sulphates.This indicates that these particles initially generated in furnace, instead of in flue formed by gas-solid reaction of deposits with SO2.As 10% or 20% SC were added, fly ash particles was less agglomeration, and rich in aluminosilicates.In addition, the P1S and P2S deposits particles turned into coarse-grained particles rich in Ca/Na aluminosilicates, and CaSO4.These revealed that complex gas-solid reactions between SO2 and CaO/Na2O/NaCl in the deposits instead of in fly ash occurred.Moreover, Ca/Na-bearing species is more competitive to react with Si/A1, rather than SOx.Therefore,SO2 might be closely associated with the mineral composition of deposited ash, while CO would accelerate slagging in furnace.The effect of NOx on deposit mineralogy and morphology was not considered.
Flue gas composition Circulating fluidized bed Gas-solid reaction oil shale semi-coke Zhundong lignite
Zhuo Liu Jianbo Li Mingming Zhu Xiaofeng Lu Zhezi Zhang Dongke Zhang
Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education of PR Centre for Energy (M473), The University of Western Australia, 35 Stirling Highway, Crawley WA 6009
国际会议
Proceeding of 2nd Conference of Circulating Fluidized Bed Boiler ( 第二届国际循环流化床锅炉会议)
青岛
英文
91-98
2019-07-19（万方平台首次上网日期，不代表论文的发表时间）