Study On Preparation Of New Wall Materials By Desulfurization Ash And Slag

In this paper,the semi dry desulphurization ash of sintered flue gas is taken as the study system,to research the new wall material prepared by coupling with blast furnace slag.Based on the research on the physicochemical properties of the desulfurization ash and slag,explore the mechanism of the coupling reaction between the two materials,to develop a new way of utilization of desulphurizing ash,In order to solve the problem of mass desulfurization ash and slag utilization.To achieve energy saving,environmental protection,waste treatment of waste,while reducing the cost of enterprise production,and improve resource utilization and achieve zero emissions of desulfurized ash.The XRD,microscopic phase analysis,energy spectrum analysis and chemical analysis were used to determine the basic physicochemical properties of desulphurization ash and slag.On the basis of this,the desulphurization ash,which is composed of unstable structure,is modified by electrochemical oxidation or chemical oxidant respectively,and the mechanism of oxidation is deduced.The modified desulphurizing ash and slag were coupled to prepare wall materials,and the physical properties of the samples were analyzed,the hydration mechanism was studied.In the process of low temperature oxidation modification of desulphurizing ash,a lot of highly active oxygen atoms generated by electrolysis process are used to oxidize CaSO₃ sulfite in desulfurized ash.The electrochemical oxidation mechanism is:the first step of the high active oxygen atom is concentrated on the surface of the desulphurized ash particles and diffuses from the surface to the reaction interface;the second step is adsorbed at the reaction interface;and the third step forms the reaction product at the interface through the shell of the reaction.Based on the research and test results,the main particle composition of desulphurization ash is three kinds:The single particle structure composed of CaSO₄;Mixed granular structure composed of CaSO₃ and CaSO₄;CaSO₃,CaSO₄ and Ca?OH?₂are the main components,divi-ded into three layers.The kernel is the unreacted Ca?OH?₂,and the crust like granular struc-ture of the outer layer of CaSO₃ and CaSO₄ respectively.And the diffusion of atomic oxygen in the shell is the rate control process of de oxidation.Study on the technology of preparing new wall materials by coupling desulfurization ash and slag.take full advantage of slag contains a large amount of CSH,CAH,as well as high active and thermodynamic metastable vitreous structure,making it hydration and gelation with desulphurizing ash,and then preparing light foam brick and steam curing standard brick.It is proved by physical and microscopic analysis,XRD and energy spectrum analysis to sample,a large number of hydrated coagulantl produced is mainly include calcium aluminosilicate hydrate and ettringite.The mechanism of the hydration and gelation is:In alkaline environment,a large number of glass network structures in slag are disinte-grated.[SiO₄],[Al O₄]tetrahedron form a three-dimensional continuous high degree of poly-merization network depolymerized into tetrahedral short chain,and further depolymerized into monomers or dimers and other active substances.It is in an amorphous active state and will react with Ca?OH?₂ in the desulphurization ash and produce CSH,CAH and other substances,which can stimulate the potential hydraulicity in the material.On the other hand,desulphurization ash contains some CaSO₄ compone-nts.The SO₄^2-will stimulate hydrated products to form ettringite,resulting in greater strength.In this study,the main process parameters for the preparation of lightweight foamed brick and steam curing standard brick are the following:?1?lightweight foamed brick:the ratio is 50wt%modified desulphurization ash,45wt%slag powder,5wt%cement clinker,2wt%CaO,0.6wt%aluminum powder,0.5wt%water glass?modulus2.2?,0.375wt%accelerator,0.015-wt%water reducing agent,and the ratio of water to material is 0.51.After weighing,adding water and mixing for 0.5 hours,the slurry was injected into the mold.The foam was comple-ted at 50?for half an hour,and then heated to 70?for 2hours of mold release.The specimen after the mold release was cured at 8 h in the steam of 100?.?2?standard steam curing brick:the ratio is 50wt%modified desulphurization ash,50wt%slag powder,5wt%standard sand aggregate,2wt%CaO,0.5wt%water glass?modulus 2.2?,20wt%water.After rolling mixedfor 15 min,the forming pressure is controlled at 13 MPa.The size of the green brick is 240 mm×116 mm×52⁵5 mm,and take the brick static maintained at 3⁵ h.Then maintained in a concrete curing box,and the curing system is 100?×10 h.The performance indexes of light foam brick and steam curing standard brick are:?1?Light foam brick:the dry density is 706⁹05 kg/m³,the average compression strength is 5.87 MPa,the drying shrink-age?0.50 mm,and the thermal conductivity?0.21 W/m·K.It is in accordance with the relevant regulations of B08 in GB11968-2006.?2?Standard steam curing brick:the average compressive stren-gth is 27.3 MPa,full water strength is 24.85 MPa,dry shrinkage is 0.51,freeze-thaw perforance qualified,its main performance reached the MU25 grade of fly ash brick,and the leaching test showed that although the leaching concentration of calcium and magnesium was high,the leaching concentration of lead,zinc,iron and copper was low.The main innovations of this study are as follows:?1?A new technology for the prepa-ration of lightweight foamed brick and standard brick by the coupling of semi dry desulfu-rization ash and slag was developed.?2?The electrochemical method was proposed to oxidize calcium sulfite in the semi dry desulphurizing ash to calcium sulfate.This research opens a new way for the bulk utilization of semi dry desulphurization ash.The method and main results can be used for reference for the development of bulk utilization technology similar to industrial solid waste.