Maria Holuszko

Separation of macerals from subbituminous coals and their response to liquefaction

ABSTRACT Separation of macerals from three Alberta subbituminous coals was investigated using float-and-sink method with dense liquids followed by the density gradient technique proposed by Dyrkacz and co-workers at Argonne National Laboratory, U.S.A. Resolutions of 90 percent or greater purity were obtained in some fractions in quantities sufficient to study their response to liquefaction. The ease of liquefaction of macerals isolated from subbituminous coals was, in descending order, liptinite, vitrinite, inertinite. Liquefaction of inertinite occurred at somewhat higher temperatures compared to that of vitrinite macerals which initiated between 350° and 400°C. Analysis of the chemical makeup of macerals from a subbituminous coal indicated that liptinite was relatively rich in hydrogen, whereas vitrinite and inertinite were relatively rich in oxygen and carbon respectively. The average densities were 1.285, 1.345 and 1.458 g/cc for liptinite, vitrinite, and inertinite respectively. X-ray diffraction and...

Coal Macerals Chemistry and Its Implications for Selectivity in Coal Floatability

Macerals are the smallest components of coal recognizable on the microscopic scale and, even when optically homogeneous, they may have variable elemental and molecular chemistry not only across different coal ranks but also in iso-rank coals. These variations in maceral chemistry may have significant impact on the behavior of the coal during processing and may also complicate predictions of this behavior. Flotation is one of the processes that is impacted by intermaceral variations. Flotation is used as a main process to upgrade the fines of higher rank coals. It depends on the surface properties of coal particles, hence their chemical composition. Most of the minerals associated with coal, with the exception of a few (elemental sulfur or some pyrites), are hydrophilic and can easily be separated if liberated from coal by flotation. The organic matter (macerals) possesses different degrees of hydrophobicity, and its response to flotation can vary depending on the surface properties that result from chemical composition of macerals and their associations with each other and minerals. This article addresses research progress in the area of chemistry of macerals and their hydrophobicity with a special reference to achieving selectivity in coal flotation.

Use of Pelletization to Assess the Effect of Particle–Particle Interactions on Coal Handleability

Although there is no widely accepted rigorous definition of handleability, the coal characteristics often referred to as handleability define whether a coal has the ability to flow unhindered through the processing and transportation systems. The handleability may be severely affected if fine coal particles aggregate. In the pelletization process, the rolling action of the drum is applied to bring the individual particles into proximity with each other so that they can aggregate and form pellets. Because of apparent similarities between these two processes, the pelletization tests are carried out in parallel to the handleability tests in this project, and the pelletization results are used to explain coal handleability properties.

Contribution of vitrinite macerals to the liquefaction of subbituminous coals

Abstract Four Alberta subbituminous coals were selected to investigate the contribution of vitrinite macerals to liquefaction. There are indications of a rectilinear correlation between conversion yields of different density fractions of coal and their vitrinite content, but it is too early to discern any conversion factor by which any maceral group may be used to predict the liquefaction behaviour of a subbituminous coal. Contrary to common belief, not all the vitrinite fraction of the feed coal is reactive. There seems to be a definite positive correlation between the percent vitrinite reacted and the liquefaction conversion yield. Much more research work is needed to further understand the contribution of vitrinite macerals to liquefaction of a subbituminous coal.

Characterization of the non-metal fraction of the processed waste printed circuit boards

Electronic waste is one the fastest growing waste streams in the world and waste printed circuit boards (PCB) are the most valuable part of this stream due to the presence of gold, silver, copper, and palladium. The metal present in PCBs is mostly recovered for the market value whereas the nonmetal fractions are often ignored. This research explored the characteristics of the non-metal fraction (NMF) obtained after the processing of milled waste PCBs with a focus on responsible end-of-life solutions, in the form of non-hazardous landfilling or incineration. The NMF was characterized using sizing, assaying, loss on ignition, calorific value measurement, and thermogravimetric analysis (TGA). The result showed that the metal content in the NMF increased with decrease in the particle size for most of the metals except antimony and the result from loss on ignition (LOI) also showed that over 50% of the coarser fraction represented organic matter compared to less than 30% for the finest fraction. The study also showed that after the recovery of metals from the waste PCBs, landfill leaching for most of the metal is reduced below the environmental limits, with lead being the only exception. The lead leachate concentration of 18 mg/L was observed, which requires further treatment prior to landfilling. With an energy value of 16 GJ/t, the NMF could provide high energy recovery if incinerated but 194 mg/kg of hazardous flame retardants present in the NMF might be released if the combustion process is not closely monitored.

Handleability Assessment of Selected Coals Using Durham Cone and Handleability Monitor

In this project the handleability of several coal samples was studied using the Durham Cone and the recently developed Handleability Monitor. The effects of the addition of fines, increased moisture and different size distributions were examined. The understanding of the behavior of fines in presence of moisture was evaluated in view of surface properties of fines. The emphasis was placed on the wettability of fines to explain some coal behavior in handling. The comparison was made between two methods.

Selection of reagents based on surface chemistry as derived from micro-FTIR mapping of coal surface to facilitate selectivity in coal flotation

In this study, the micro-FTIR analysis was used to investigate in-situ surface properties of coal and its components (macerals) and these were directly correlated to the coal hydrophobicity as measured by the contact angle before and after reagent addition to understand the suitability of the reagent for flotation. The micro-FTIR technique can provide a semi-quantitative analysis of the chemical functional groups on coal surface, exactly where the contact angle is being measured. Selected functional groups and their ratios that provide information about aromaticity, the contribution of oxygenated groups, and aliphaticity are used to evaluate the reactivity between reagents and various coal components. The observations made in relation to the susceptibility of some reagents towards certain coal components should lead the way to a smarter way of using process design in terms of reagents selection for coal flotation.

Evaluation of Chemical Reagents to Enhance the Dewatering of Fine Coal

ABSTRACT Coal dewatering of fine coal is one of the major challenges faced by the coal preparation plants. The plant studied in this research is currently producing a fine coal product with 28% moisture and is required to reduce it to below 17% before this fine stream is blended with rest of the clean coal streams. A lot of dewatering aids such as surfactants, flocculants, and superabsorbent polymers are available on the market to enhance the dewatering process. The research was designed to use various dewatering aids to reduce the moisture content of this fine product without decreasing the production rate. Several commercially available chemical reagents were used to enhance the dewatering of this coal product. These reagents were selected in such a way that they could be grouped into different categories depending on their action. The results showed that the surface tension reducing reagents (STR) have a higher capability of moisture reduction than the coal hydrophobicity modifying (CHM) reagents and commonly used in filtration flocculants. Super absorbing polymers used in the dewatering of fine coal were shown to outperform all the other reagents and seem to be suited for this plant dewatering scenario. A cost-benefit analysis is required to make necessary plant modifications if they are to be used there, however, this was not in the scope of this project.

Chapter 3 – Coal Processing and Use for Power Generation

Coal is an important source of energy and raw material for electric power production. Despite climate change legislation, growth in coal consumption thus far outpaced that of other fossil fuels in the twenty-first century. Coal is a reliable energy source, abundant, easily transported, easily traded and competitive in terms of price compared to other fossil fuels. The technology of coal preparation, coal cleaning and use in power generation is discussed. It covers issues such as coal properties and how these relate to coal performance in power generation, as well as ways to remove sulphur, mineral matter and water before coal combustion to improve the efficiency of power generation and reduce emissions from coal use.