Research On The Expansion Characteristics And Application Of Coal Gangue Desulfurization Slag From Circulating Fluidized Bed (CFB)

Circulating fluidized bed(CFB)coal gangue desulfurization ashes are the residues of coal gangue power plant after burning and desulfurization by circulating fluidized bed boiler.Among them,desulfurization ash is collected from the flue and desulfurization slag is discharged from the bottom of the furnace.Like coal-fired desulphurization ashes,coal gangue desulphurization ashes also have the characteristics of self-hardening,high water absorption and high expansion.However,due to different fuels,there are certain differences in the chemical composition and mineral composition of the two kinds of desulfurization ashes,which will lead to differences in properties.In this paper,basing on the study of physical and chemical properties of coal gangue desulfurization slag,its expansion characteristics have been systematically studied,and the application of the coal gangue desulfurization slag to self-compacting concrete filled steel tube has been creatively utilized,which provides a reference and basis for the resource utilization of coal gangue desulfurization slag.The main research contents and results are as follows:(1)The influence of desulfurization slag content,fineness and sodium sulfate activator content on the water consumption,setting time and stability of the ground desulfurization slag and cement paste was systematically studied.The results show that,the water consumption of T4(55min)is the maximum,about 28%.The higher the content of desulfurization slag,the higher the water consumption of the paste.When the amount of desulfurization slag is 30%,the setting time of the paste is the shortest.When the amount of the desulfurization slag is 50%,the Le chatelier value is the maximum,about 1.8 mm.The addition of 1%~2% sodium sulfate has little effect on the water consumption of the paste,but will shorten the setting time and increase the Le chatelier value.(2)The fine desulfurization slag was used to replace the cement by the same amount,and the factors such as the fineness of desulfurization slag,the amount of admixture,sodium sulfate activator,water-cement ratio,and the time of mold removal,which affected the linear expansion rate and mechanical properties of mortars,were systematically studied,and the correlation between linear expansion rate and compressive strength was also discussed.The results show that,the expansion of the mortars tends to be stable after 28 d curing age.With the increase of fineness,the linear expansion and compressive strength of martars increase,and the linear expansion rate and compressive strength show obvious positive correlation.As the content of desulfurization slag increases,the linear expansion rate of mortars increases.When the dosage is 30%,the 7d and 28 d compressive strength of the mortars gain the maximum.With the increase of sodium sulfate content,the linear expansion rate and compressive strength of mortars increase,and the linear expansion rate and compressive strength are positively correlated.With the increase of water-cement ratio,the linear expansion rate of mortars increases,the compressive strength decreases,and the linear expansion rate and compressive strength are negatively correlated.The delayed mould removal has a significant effect on the expansion of the mortar.(3)The self-compacting concrete containing desulfurization slag was successfully prepared by mixing ratio design with the content,water-cement ratio and sodium sulfate activator as variables.The effects of dosage,water-binder ratio and sodium sulfate activator on the working performance and compressive strength of self-compacting concrete were analyzed.For fresh self-compacting concrete with desulfurization slag,as the content of ground fine desulfurization slag increases,the slump-flow decreases.As the water-cement ratio increases,the slump expansion rate increases.The addition of 1.5% sodium sulfate has no effect on the slump-flow.For hardened self-compacting concrete with desulfurization slag,the early and late compressive strength of self-compacting concrete with ground desulfurization slag decrease comparing with the basic self-compacting concrete.The decrease of the compressive strength with 30% admixture is smallest,only 2.8%.When adding 1.5% sodium sulfate,the 3d compressive strength of concrete raises about 17.6%,and the 28 d compressive strength raises about 2.9%.(4)The influence of different constraint conditions(free,one-way restriction and steel tube restriction)on the deformation performance of self-compacting concrete with desulfurization slag was systematically studied,the deformation properties were microscopically analyzed,and the finite element simulation using temperature rise model is carried out to the deformation of specimen under steel tube restriction.The results show that,the expansion development process of free expansion specimen can be divided into three stages: rapid release period,slow growth period and steady expansion period.The expansion development process of steel tube restrained specimen can be divided into two stages: increasing period and stable period.XRD study showed that the hydration products under the three constraints were the same,all of which were C-S-H gel,calcium hydroxide,gypsum and AFT.SEM pictures show that the concrete under steel tube constraint is the densest.Using ABAQUS finite element software,the temperature rise model can simulate the deformation caused by the expansion of core concrete,but the simulation value is generally lower than the test value.(5)Experimental research and finite element analysis were carried out on the axial compressive property of self-compacting concrete filled steel tube short columns.The results show that,the failure type of short column is ductile failure,and the failure form is shear type multi-fold lumbar drum failure.The N-? curve can be divided into three stages: elastic stage,elastoplastic stage and hardening stage.When the dosage of ground desulfurization slag is 30%,the ultimate bearing capacity of the short column is the highest.The compressive strength of core concrete is the main factor which affects the bearing capacity of components.The self-stress can improve the ultimate bearing capacity of concrete-filled steel tube,which has significant influence on the ultimate bearing capacity of concrete-filled steel tube.ABAQUS finite element software was used for simulation,and the results obtained were basically consistent with the test results.