Obtaining of Granulated Gypsum Anhydrite on the Basis of Technogenic Wastes of Chemical and Metallurgical Complex for Use in Portland Cement Production

Alexander Ponomarenko

doi:10.18502/kms.v6i1.8059

Abstract

The composition and properties of fluorine–anhydrite and steel–refining slag which are wastes of production of hydrogen fluoride and steel were determined. It is established that fluorine–anhydrite of the current output does not meet the requirements to materials for the production of Portland cement. Therefore to improve the technical and consumer properties of fluorine-anhydrite (for increasing the amount of CaSO4 ⋅2H2O and neutralization of H2SO4) the studies of its’ conditioning processes with steel– refining slag were carried out. It was found that the mass transfer coefficient of sulfuric acid through the capillary and the degree of its neutralization by slag depend on the dispersion of fluorine–anhydrite, its porosity and initial acidity. The most effective binding of sulfuric acid occurs with the introduction of slag in stoichiometric amounts, the size of fluorine–anhydrite granules up to 20 mm and a processing time of 60 minutes. After storage in air-humid conditions for 12 hours of fluorine–anhydrite treated with slag the strength of its granules, the amount of dihydrate gypsum and toxicological properties meet the requirements. Keywords: techno–gypsum, refining slag, neutralization, conditioning, gypsum stone, Portland cement

Highlights

Selection and Peer-review under the responsibility of the TECHNOGEN-2019 Conference Committee.In cement plants natural gypsum stone or gypsum–anhydrite stone are used to control the setting time of cement, but their stocks and quality inevitably decrease over time.In addition in some regions there are no any deposits of gypsum stone, and its quarrying, preparation and transportation to cement plants require significant costs.The studies results [1–9] show that so–called techno–gypsums which are byproducts of the chemical industry can be used to regulate the setting process of Portland cement
At the enterprises for the production of hydrogen fluoride and steel hundreds of thousands tons of fluorine–anhydrite (FA) and metallurgical slags are formed every year; they are stored in waste fields or in sludge storage polluting the environment
The content of H2SO4, CaF2 and CaSO4⋅2H2O in the FA granules as well as the mechanical compressive strength of the granules were determined at regular intervals after slag treatment. This studies are based on the hypothesis that when moistening and processing granulated FA from the furnace with fine slag a thin layer of reaction products is formed, which has high adhesion, provided increased strength and water resistance of granules for transportation and storage of FA after conditioning in open areas of enterprises producing of hydrogen fluoride and cement plants

Summary

Introduction

Selection and Peer-review under the responsibility of the TECHNOGEN-2019 Conference Committee.In cement plants natural gypsum stone or gypsum–anhydrite stone are used to control the setting time of cement, but their stocks and quality inevitably decrease over time.In addition in some regions there are no any deposits of gypsum stone, and its quarrying, preparation and transportation to cement plants require significant costs.The studies results [1–9] show that so–called techno–gypsums (phosphogypsum, etc.) which are byproducts of the chemical industry can be used to regulate the setting process of Portland cement. This studies are based on the hypothesis that when moistening and processing granulated FA from the furnace with fine slag (as a result of its interaction with sulfuric acid on the surface of the FA granule) a thin layer of reaction products is formed, which has high adhesion, provided increased strength and water resistance of granules for transportation and storage of FA after conditioning in open areas of enterprises producing of hydrogen fluoride and cement plants.

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Conclusion