Study Of Mechanism Of CO₂ Mineralization Capture By Phosphogypsum Decomposition Slag

Phosphogypsum?PG?is a waste product of industrial hydrometallurgical phosphoric acid,whose main component is calcium sulfate dihydrate?Ca SO₄·2H₂O?.It has good thermal stability and is accompanied by a certain degree of acidity and slight corrosion.According to a rough estimate,the production of 1 ton of phosphoric acid will produce 3.5 tons of PG and it is now with an increasing accumulation.The current treatment for phosphogypsum includes the production of co-produced sulfate cement,production of raw materials?calcium chloride,ammonium sulfate,potassium sulfate,sodium sulfate,thiourea,sodium hydrogen phosphate,hydroxyapatite nanoparticles,etc.?,and use of soil as soil,production of building materials,purification of heavy metal polluted water and so on.CO₂ emission all over the world is constantly on the rise while human activity was considered to be the main reason for greenhouse gas CO₂ emissions.The acceleration of the industrialization process,the excess combustion of fossil fuels,the destruction of forest vegetation,and the rapid development of modern agriculture has led to a sharp increase in CO₂ concentration which further causes a rise in global sea levels,a reduction in fresh water resources,extreme climate,human health,and severe damage to the global ecosystem.It has been estimated that,by the year 2050,to decrease the average global temperature by 2.0-2.4°C,in comparison to that in the year 2000,the world must reduce nearly 50%-80%of CO₂ emission levels.Therefore,it is imperative to develop reasonable and scientific CO₂ emission reduction technologies.In recent years,CO₂ capture technology has been changing with each passing day and has been greatly improved and innovated.The calcium-based absorbent method is currently one of the more widely used technologies for CO₂ gas capture applications.The principle is to use a calcium-containing absorbent to perform carbonation under certain conditions to achieve CO₂ absorption.The calcium-based absorbent has high absorption capacity,good absorption effect,high temperature resistance,and widely distributed calcium sources in nature.CaO and CaS as the main components of phosphogypsum decomposition slag have good CO₂ capture efficiency.This paper presents a method of phosphogypsum decomposition slag as a calcium-based absorbent,uses a theory of?waste to waste?to solve the exhausts at the same time.Meanwhile,the relevant experiments were carried out and the mechanism of the reaction process was studied.A new solution was proposed for CO₂capture and resource utilization of phosphogypsum.?1?Simulations and calculations of Factsage 7.1 and phosphogypsum TGA related experiments were carried out.In order to ensure fully reaction of PG and lignite,the optimal mixing molar ratio of phosphogypsum and lignite for thermal decomposition was 4:1,the best decomposition temperature was 1100°C,and the optimal holding time was 60 minutes.The decomposition slag mainly composed of CaS was generated.At the same time,the above data was applied to a tube furnace for verification experiments.At the same time,the above data was applied to a tube furnace for verification experiments.Studies have shown that the purity of CaS obtained under this decomposition condition can reach at 98.47%.?2?The relevant thermodynamic parameters of CO₂ capture experiment were simulated by Factsage 7.1,and the thermodynamic parameters of the decomposition slag during CO₂ capture were determined through gas-liquid-solid three-phase diagram.The capture temperature was 25°C,the capture pressure was 1atm,etc.,and the above experiments were performed in the relevant reactors to determine the best liquid-solid ratio,reaction time and other parameters.The above studies were performed in the relevant reactor to determine the relationship between CO₂ capture of the optimal liquid-solid ratio,reaction time,pressure,temperature,and other parameters and capture efficiency.Studies have shown that the lower the liquid-solid ratio,the better the effect of decomposition products on carbon dioxide capture;with the increase of reaction time,the capture efficiency increases rapidly until saturation,the best capture time is 24min;the higher the reaction temperature,the more unfavorable CO₂ capture efficiency;increased pressure has little effect on carbon dioxide capture.?3?The hydrogen sulfide produced in the capture experiment is toxic and hazardous,and it is a flammable hazardous product.The hydrogen sulfide gas generated in this process was then returned to the tube furnace as a reducing agent for the thermal decomposition of phosphogypsum.Studies have shown that hydrogen sulfide gas reduces Gibbs free energy in the thermal decomposition process to a certain extent,and can accelerate the reaction rate in the reaction process,to a certain extent,shorten the reaction time Thus,it has not only solved the harm of exhaust emissions to the human body and the environment,but also achieved the cycle of experiments.