Carbonised fluidised fly ash (CFFA); a new product for mining engineering purposes (discussion of possible applications)

The article presents and summarises the current state of research and laboratory results on the carbonation of fly ash with carbon dioxide in the context of its use in mining engineering. Based on previous publications and patent applications, the possibilities of using carbonated fly ash from fluidised bed boilers for the following applications were discussed: securing excavations particularly susceptible to fire hazards, shotcreting and securing longwalls and supports, constructing cases, securing decommissioned shafts, and others, which means wherever the use of cement is required. It was pointed out that the removal of excess free calcium oxide makes it possible to use carbonated fly ash in mining applications for placement in workings requiring increased tightness. It was also stated that carbonation allows the removal of hydrogen from fluidised fly ash (FFA) obtained during co-combustion. The research highlighted the potential and importance of granulating carbonised FFA in expanding the applications of this innovative product in mining engineering

Transformations of calcium sulphates in solidified carbonated volatile fluidized ashes

Carbonation of volatile fluidized ashes with the use of carbon dioxide can be a means to their transformation into a product with a possible application as an additive to cement and concrete. Currently, due to its physical-chemical characteristics and particularly because of the high concentration of free calcium oxide, the possible applications of this product are highly limited, perhaps even none existent. A significant reduction or even the complete elimination of CaO can be achieved by its transformation into calcium carbonate. In carbonated volatile fluidized ashes, two components relevant to the binding time of mortar, as well as its durability, can be found: calcium carbonates and calcium sulphates. During the investigation it was assumed that calcium carbonate, being poorly water-soluble, would not react with the remaining components of the porous water of the volatile fluidized ash. Crystalline phases of calcium sulphates, anhydrite, gypsum and bassanite occurring in bound volatile fluidized ashes after carbonation demonstrate the possibility of crystallization in the presence of calcium carbonate. In particular, a change in the concentration of bassanite indicates that this phase, as a precursor to the crystallization of gypsum, may play a significant role in the process of binding carbonated volatile ashes

Process Kinetics of the Carbonation of Fly Ashes: A Research Study

The aim of the paper is to present the results of research on the carbonation process kinetics of coal combustion ashes originating from fluidized bed boilers used in power plants. Based on the thermogravimetric analysis (TGA), the hypothesis that carbon dioxide is bounded by the mineral substances (calcium compounds) in the fly ashes was confirmed. Determining the kinetic parameters of the carbonation of fly ashes requires simultaneously taking into consideration the kinetics of the drying process of the sample. The drying process of the sample masks the effect of the reaction of CO2 with calcium compound. Unlike the ashes generated in pulverized fuel boilers, fly ashes contain irregular amorphic mineral components or poorly crystalized products of complete or partial dehydroxylation of claystone substance present in shale formations constituting the gangue as well as anhydrite (CaSO4), a desulfurization product. The content of free calcium oxide (CaO) in such ashes ranges from a few to several percent, which is a significant obstacle considering their use in cement and concrete production as type II admixtures understood to be inorganic grained materials of pozzolanic or latent hydraulic properties. The paper presents effective mechanisms which reduce the content of free CaO in ashes from Fluidized Bed Combustion (FBC) boilers to a level that allows their commercial utilization in the cement industry

Evaluation of the possibility of using granulated carbonated volatile fly ash from fluidized beds (G-CVFA) in underground mining techniques

The application of fluidized fly ash in underground mining excavations is limited due to its significant content of free calcium and calcium sulfate. In order to increase the amount of utilized fly ash from fluidized beds, it should be converted to a product with properties that meet the requirements for mining applications. This research presents the results of an attempt to adapt fluidized fly ashes for use in underground mining techniques, by means of carbonation and granulation. Carbonation was performed with the use of technical carbon dioxide and resulted in the reduction of free calcium content to a value below 1%. Granulation on the other hand, resulted in obtaining a product with good physical and mechanical parameters. The performed mineralogical and chemical studies indicate that trace amounts of "binding" phases, such as basanite and/or gypsum are present in the carbonized ash. The addition of water, during the granulation of carbonized fluidized fly ash, resulted in changes in the mineral phases leading to the formation of ettringite and gypsum as well as the recrystallization of the amorphous substance. It was confirmed that the carbonization and granulation of flying fluidized ashes positively affects the possibility of using these ashes in underground mining excavations

System wspomagający ocenę emisji CO2 ze zwałowisk odpadów powęglowych

This article show the database application – part of the system COOL’s – that collects, stores and publishes the data about the state of coal waste dumps. This application implements the adaptive and scalable model of acquisition of data from different devices. Also the universal model of different type/domain/unit values representation is in the database.Artykuł opisuje aplikację bazodanową – część systemu COOL’s – która zajmuje się akwizycją, przechowywaniem i udostępnianiem informacji o stanie zwałowisk odpadów powęglowych. Podczas implementacji wspomnianych modułów zastosowano ciekawe i możliwe do adaptacji rozwiązania związane z pobieraniem danych z urządzeń pomiarowych oraz przechowywaniem ich w uniwersalnej strukturze bazy danych

Modelling of Gas Flow in the Underground Coal Gasification Process and its Interactions with the Rock Environment

The main goal of this study was the analysis of gas flow in the underground coal gasification process and interactions with the surrounding rock mass. The article is a discussion of the assumptions for the geometric model and for the numerical method for its solution as well as assumptions for modelling the geochemical model of the interaction between gas-rock-water, in terms of equilibrium calculations, chemical and gas flow modelling in porous mediums. Ansys-Fluent software was used to describe the underground coal gasification process (UCG). The numerical solution was compared with experimental data. The PHREEQC program was used to describe the chemical reaction between the gaseous products of the UCG process and the rock strata in the presence of reservoir waters