Experimental Study On Desulfurization And Carbon Sequestration Agent Using Aluminum-silica-calcium Slag From Fly Ash

The calcium-calcium slag is obtained by adding alkali and limestone to fly ash to extract the solid waste that will be produced during the production of alumina.For each ton of alumina produced,approximately 2.0 to 2.5 tons of calcium-calcium slag is produced.The main chemical components of silica-calcium slag are SiO₂ and CaO,which are characterized by light weight,porosity,relatively low density,strong ability to adsorb liquids,and poor acoustic,thermal,and electrical conductivity.Silica-calcium slag is produced in large amounts and accumulated too much.Currently,it is mainly used in the fields of construction materials,cement production,wastewater treatment,and road construction.However,excess waste residue still occupies large amounts of land and pollutes the surrounding environment.With the expansion of alumina production scale,the discharge of calcium-silicon slag will be more,so it is necessary to seek new waste residue treatment and export.The surface of silica-calcium slag is loose and porous,and the pH value of the prepared slurry is more than 12.It can be used as an absorbent for SO₂,CO₂ acid gas.According to the physical and chemical properties of silica-calcium slag,it can be reasonably utilized in flue gas treatment.Silicon-calcium slag is used to absorb CO₂ and SO₂ acid gases to form a"waste and waste treatment"process,forming a new model to treat flue gas with waste residues.In this paper,silicon-calcium slag is used as a laboratory basic research on the feasibility of desulphurization agent and carbon exploration experiments.X-ray fluorescence spectrometry?XRF?was used to test the chemical composition of the silicon-calcium slag.The diffraction patterns were analyzed by X-ray diffraction?XRD?to obtain the mineral composition of the raw materials and products.The results were observed by scanning electron microscopy?SEM-EDS?.The micro-morphology of solid raw materials and products;thermogravimetry?TG-DTG?was used to analyze the thermogravimetric characteristics of solid raw materials and products.The physicochemical properties of the calcium-calcium slag were studied first.Based on this,the characteristics of the sulfation reaction of the silicon-calcium slag were studied,and the sulfation reaction characteristics of the silicon-calcium slag under different conditions were investigated.Such as the order of addition,liquid-solid ratio,grinding time and reaction temperature,etc.,the in-situ changes of the pH of the slurry under different conditions were investigated,and the inherent laws of the sulfation reaction of the calcium-calcium slag were reflected.The results show that the calcium slag is added into the acidic liquid at one time,which easily leads to the rapid formation of the reaction product,calcium sulphate enveloping the surface of the reaction calcium slag,which hinders the reaction to a certain extent;The greater the solid content of the calcium calcium slag slurry?the lower the liquid-solid ratio?,the faster the reaction time with the earlier stage of the sulfation reaction,and the corresponding reaction time is greatly shortened;Grinding silica-calcium slag is beneficial to increase the activity of silica-calcium slag and promote its sulphation reaction.When the silica-calcium slag is ground for 2.0h,the effect of better sulphation reaction speedup can be obtained.At the same time,the reaction temperature is lower than 55°C to obtain better sulfation reaction.Through the analysis of physicochemical characteristics and thermal weight loss characteristics of the calcium sulphate sulphation reaction product,it was shown that the calcium sulphate sulphation reaction can obtain calcium sulphate whisker products and silica gel products,which is used for the industrial application of flue gas desulfurization and desulphurization of silicon calcium slag High value-added use of products provides a theoretical and experimental basis;The reaction rate between silica-calcium slag slurry and SO₂ is closely related to the rate of SO₂ infiltration.The reaction rate between silica-calcium slag and SO₂ is not only related to the flow of SO₂ gas,but also related to the reactivity of silica-calcium slag,but the overall There is no significant relationship between the reaction temperature and the reaction temperature between 25-75°C;The chemical composition,mineral composition,micro-morphology and thermal weight loss characteristics of the reaction products of silica-calcium slag and SO₂ are similar to those of the sulfation reaction product of silica-calcium slag,which proves that the calcium-calcium slag has the technical feasibility for the removal of SO₂ from flue gas.Finally,the absorption of CO₂ by silica-calcium slag was also investigated.The results showed that the rate of carbon sequestration of silica-calcium slag was 10%.How to increase the carbon sequestration rate needs further study.