Utilization Of Distiller Waste From Solvay Soda Ash Plants Based On Carbonation And Coupling Of Reaction And Separation

Distiller waste is a stubborn discharge mother liquor from soda industry.The soda ash plant’s capacity to expand its production is severely constrained by the material’s challenging separation,poor value,and heavy consumption throughout the treatment process.Hence,one of the most important issues for the green development of the soda industry is the development of an effective and high-value distiller waste treatment technology.Taking Qinghai Province as an example,the issue of how to properly dispose of distiller waste has been challenging to resolve for decades and has turned into a"bottleneck"issue that is really restricting the growth of the soda industry.This paper proposed a new strategy to fully develop the inorganic salt resources in distiller waste based on research by domestic and international scholars on the treatment and resource utilization of distiller waste.This strategy entails extracting the primary inorganic salt components in distiller waste and converting them into Ca CO₃ products with special morphology,and stercorite product with high added value,in order to realize full quantitative utilization and profitable production.This work makes related new attempts and explorations in the reaction mechanism of separation and transformation of sodium and calcium components in distiller waste in an effort to overcome the technical and financial limits of the exploitation of distiller waste for many years.The significance of this study lies in the exploration and attempt to improve the technical and economical utilization of distiller waste.The characteristics and highlights of distiller waste are its high value and resource usage,while its advantages include resource recycling,environmental friendliness,economic viability,and a wide range of potential applications.These specific works are included:（1）Aiming at the extraction and conversion of Ca²⁺,Na⁺,Cl^-,OH^-,Ca（OH）₂ and NH3·H2O in distiller waste,the whole process of full quantization utilization was put forward.Initially,heat from high-temperature flue gas is utilized to evaporate and concentrate liquid phase,producing a byproduct that contains Ca SO₄.The next step investigates the enrichment of CO₂ flux into distiller waste created in the CO2-HCO3^--CO3^2-buffer system,focusing primarily on the precipitation properties of Ca²⁺hydrate and Na⁺hydrate.Ca²⁺hydrate and CO3^2-form precipitate out more readily than Na⁺hydrate,according to molecular dynamics（MD）simulation results.Finally,the effects of classic carbonate precipitation and CO₂ absorption methods on the separation of Ca²⁺and Na⁺in distiller waste were compared.Although the former had a high ratio of Ca²⁺removal,the latter produced a higher-quality output.Thus,in the extraction phase of Ca²⁺in distiller waste,the high-value product was prepared by CO₂ absorption method initially,and carbonate precipitation is then used to transform the residual Ca²⁺.（2）Ca²⁺was partially extracted from distiller waste by using CO₂ absorption to create high-value Ca CO₃ hollow microspheres.The effects of Ca Cl₂,Ca（OH）₂,ammonia concentration,CO₂ concentration and flow rate on the product were studied.The optimal reaction condition was established by increasing the ammonia concentration in the distiller waste to 0.286 mol/L and injecting 2.5 L/（min·L）of CO₂.Also,the main topic of discussion is the Ca CO₃ hollow microspheres’creation mechanism.The findings demonstrate that the system’s suspension of Ca（OH）₂ particles serves as an adhesion center for the nucleation of Ca CO₃ in the form of non-template,facilitating the quick nucleation and development of calcite.The contact angle（θ）,interfacial energy,and interfacial tension(?_ls)during crystal formation in the liquid phase indicate that massive calcite changes into spheroids because the interface parameters are changed.Spheroids with small inner and big exterior particles undergo Ostwald ripening process,which finally results in the formation of hollow structures.（3）Conversion of Na+in distiller waste:Adding（NH₄）₂HPO₄ into the distiller waste after decalcification and synthesizing high-value and high-yield stercorite products through reaction separation and coupling method.The effects of operating temperature,reaction time,mother liquor concentration ratio and drying method on the product were investigated.The optimal synthesis conditions were determined that the concentration ratio of DW-3 was 40%,the reaction at 80℃for 20 minutes,and the crystallization at 0℃for 20 minutes.The conversion ratio of Na⁺in the solution could reach 90%,and the yield of DW-3 was 455.2 g/L.In particular,the product at 70℃produced a new phase of stercorite in the product after filtration.The yield of the product at 80℃increased to 470.4 g/L DW,and the conversion efficiency of Na also increased to 93%.The remaining high concentration salt solution（mainly NH₄Cl）can be used as the raw material of liquid fertilizer,which has the potential of direct commercialization.（4）To verify that the process route breaks through the technical and economic bottleneck of the treatment process of distiller waste was used in order to evaluate the technical economy of the entire process.The material balance and energy consumption of each section in the whole process were calculated.Furthermore,The construction and production of a plant that treats 10 tons of distiller waste per day are used as an example to comprehensively analyze the economic efficiency of the technology.Taking the construction and production of a factory that treats 10 tons of distiller waste per day as an example,the initial investment cost is about CNY 23.2 million,and the daily consumption cost is CNY 37,818.3,the total income is CNY 49,789.5 and the profit is CNY 11,971.2.The annual income is CNY 3.147 million,the return on investment is 18.83%,and the return-on-investment period is 5.31 years.This technical route offers a reference idea for this use of distiller waste.In this paper,using distiller waste as a resource has the potential to significantly reduce the environmental threat posed by this waste and the frictional contradiction of resource loss,further the development of the Solvay Soda Ash industry,and contribute to the growth of the local economy and the preservation of the natural environment.