Analysis of Intermolecular Complexes of Coal’s Organic Mass in the Search for Composite Flotation Reagents

Cyclic oxygen-bearing compounds and products of petroleum processing are considered as potential composite reagents. In searching for highly effective composite reagents differing in structure and elementary composition, one possible criterion is the energy of the hydrogen bond in intermolecular complexes between the reagent and the coal’s organic mass. The hydrogen-bond energy in intermolecular complexes between the reagent (cyclic siloxanes) and the coal’s organic mass is much higher than that in intermolecular complexes between water and the coal’s organic mass. That is responsible for the reagents’ high flotational activity. The use of distillation residues from the production of octamethylcyclotetrasiloxane improves the extraction of combustible mass in the concentrate in comparison with that currently attained at coal-enrichment facilities. In addition, the reagent consumption is decreased. Products of petroleum processing whose group chemical composition includes cyclic organosilicon compounds are recommended for industrial tests at Russian coal-enrichment facilities.     

Assessment of the flotation activity of reagents in terms of the hydrogen bond energy in molecular complexes with active sites of the coal surface

The hydrogen bond energy of molecular complexes between a flotation reagent and coal’s organic mass is calculated for the first time. The electron density distribution in molecules of 2-methyl-1,3-dioxane and 2-methyl-1,3-dioxa-2-silacyclohexane is determined. It is shown that the silicon atom in the molecule of 2-methyl-1,3-dioxa-2-silacyclohexane increases the electron density at oxygen atoms from ?0.279 to ?0.424 and ?0.432 in positions 1 and 3 of the molecule, respectively. This increases the hydrogen bond energy of the reagent in molecular complexes with water and model compounds of the coal’s organic mass. In molecular complexes of 2-methyl-1,3-dioxa-2-silacyclohexane with model compounds of the coal’s organic mass, the hydrogen bond energy is considerably higher than in corresponding complexes of 2-methyl-1,3-dioxane. As a result, the adsorption of 2-methyl-1,3-dioxa-2-silacyclohexane on the coal surface is 35–45% greater than for 2-methyl-1,3-dioxane. Consequently, the coal grains become more hydrophobic, and their flotation is improved. With the same consumption of reagents, the use of 2-methyl-1,3-dioxa-2-silacyclo-hexane rather than 2-methyl-1,3-dioxane increases the concentrate yield and reduces the losses of the coal’s organic mass with the wastes. Analogous flotation properties of coal are found for other cyclic acetals and their silicon analogs. Experimental data confirm that the hydrogen bond energy in complexes between the flotation reagent and the coal’s organic mass may be used to assess its effectiveness.     

Effective foaming agents for coal flotation: A quantum-chemical approach

The effectiveness of the following compounds as foaming agents is evaluated: heteropolar ketones and sulfoxides whose molecules contain oxygen and sulfur; and petrochemical products such as butanol bottoms and T-80. The use of methylhexyl sulfoxide instead of butanol bottoms increases the extraction of the coal’s combustible component in the concentrate from 87.1–90.9% to 93.9–95.25%, with simultaneous decrease in reagent consumption by ~20%. That may be attributed to the excellent foaming properties of methylhexyl sulfoxide and its ability to render the coal particles hydrophobic. The flotational activity of compounds with different functional groups in the molecule may be compared on the basis of the energy of the hydrogen bond in molecular complexes of the reagent with the coal’s organic mass. In molecular complexes of methylhexyl sulfoxide with model compounds in the coal’s organic mass, the energy of the hydrogen bond is considerably greater than that for the corresponding molecular complexes of methylhexyl sulfoxide with model compounds in the coal’s organic mass. That ensures 35–45% increase in the adsorption of methylhexyl sulfoxide on the coal surface in comparison with methylhexyl ketone and also results in more hydrophobic coal grains, which undergo more effective flotation.     

Intensification of coal flotation by means of oxyethylated reagents

Coals supplied for coking are enriched until the mineral content is 7–9%. With greater mechanization of coal extraction, the content of fine classes (<0.5 mm) in regular coal sent for enrichment is 15–35%. Flotation provides an effective means of enriching fine coal. However, flotation is expensive (on account of the reagent cost) and environmentally problematic. In addition, because oil-industry wastes of variable group chemical composition are used as the reagents, flotation is associated with considerable loss of organic mass of the coal and chemical compounds with the waste. The use of activators is a promising means of increasing coal extraction in the concentrate, with simultaneous decrease in the consumption of expensive flotation reagents.     

Composition of the Clarodurain Lithotypes of Kuzbass Coal and Its Flotation Concentration

Vital differences of the chemical composition and basic technological properties and the flotation concentration of the petrographic lithotypes of laminated coal of the Balakhon series of Kuzbass are considered. It is shown that the efficiency of flotation of the lithotypes is determined by the special features of the distribution and combination of the organic and mineral components of coals. Low-ash semi-dull lithotype with a high yield of concentrate is floated with a traditional nonpolar reagent based on kerosene. The efficiency of flotation of high-ash bright lithotype increases with the use of flotation agents with heteropolar properties.     

Determining the cause-and-effect relationships responsible for coal Properties 4. Assessing the influence of mineral impurities on the organic mass of coal

Coal may be regarded as an organic–mineral complex formed by the accumulation of sediments and their metamorphic transformation to sedimentary rock. On that basis, Kuznetsk Basin coal may be analyzed in terms of the corresponding genetic characteristics of gelification and reduction and the chemical composition of its ash. The influence of mineral impurities on the organic mass of coal may best be assessed on the basis of integral characteristics: the oxide moduli in assessing mineral impurities; and the genetic benefit K^gb for the organic mass. The genetic benefit provides information regarding the molecular structure and mineral composition of the coal.     

Surfactants in coal technology

The principal uses of surfactants and related compounds in coal technology are the control of coal dust, the purification of coal from admixtures by flotation, the dispersion of coal in water for transportation through pipelines and as a fuel system, the dispersion of coal in fuel with subsequent burning of the coal/oil mixture, demineralization of coal, freeze-conditioning agents and side-car release agents for railroad transport of coal. These applications have been reviewed in this order. This overview demonstrates that the use of surfactants in coal technology is rapidly growing with the increasing interest in utilizing coal as a source of energy and that basic studies are in progress to explain the underlying surface chemical phenomenon.     

Desulfurization of mezino coal using combination of ‘flotation’ and ‘leaching with potassium hydroxide/methanol’

Mezino coal contains a high percentage of ash and both organic and inorganic sulfur. The ash and sulfur contents can be reduced using physical–chemical and chemical methods. ‘Froth flotation’ is a physical–chemical method that is capable of reducing inorganic sulfur and the ash content of coal. In this research, reducing the ash content of mezino coal by 83%, inorganic sulfur by 72% and its total sulfur content by 63% using flotation in alkaline pH and in the presence of copper ion was successful. The coal flotation obtained was 73%. The coal concentration obtained from flotation was leached using potassium hydroxide/methanol mixture and its total sulfur and ash contents were reduced by approximately 33 and 8%, respectively. Hence, using the combination of the two mentioned methods, the total sulfur and ash contents of coal were reduced by 82.50 and 82.34%, respectively. It is an unprecedented and welcome result compared to the previous work.     

Group chemical composition of coal batch and reactivity of coke. 3. Phase composition of the primary products of coal pyrolysis

The action of the group chemical composition of coal’s organic mass on its phase composition in the plastic state and hence on the coke quality is quantitatively described and experimentally verified.     

Coal surface conditioning for electrostatic separation

In analogy with froth flotation using chemical agents to enlarge the difference of hydrophobicity, this study was undertaken to examine the feasibility of enlarging the differences in surface work function of coal components to improve the electrostatic separation. Two coal specimens from Alberta having medium ash and low sulfur contents were used. Chemical agents having different physical and chemical properties were investigated in both batch and continuous operation. The results show that either maceral or ash forming mineral separations can be improved by surface treatment with organic chemicals. Improvements of more than 10% were observed. The results also show that some aromatic chemicals are better for coal maceral separation while some aliphatic agents improve ash forming mineral separation.     

Interaction of the coal surface with water

The quantum-chemical characteristics of molecules in coal’s organic mass, water, and complexes formed in the interaction of the coal surface with water are calculated. Results obtained by semiempirical root-mean-square calculation indicate that water and the compound simulating the structure of coal’s organic mass are rigid. The functional groups of the coal’s organic mass capable of displacing the electron density are nucleophilic centers and are capable of forming electrophilic centers.     

Application of the electrochemical oxidation products of humic substances to the flotation treatment of high-ash coal sludge (short communication)

It was found that the low-molecular-weight compounds formed on the electrochemical oxidation of the lignohumic acids of pine possess surface-active properties, which facilitate the more effective flotation separation of the organic and mineral components of coal-clay sludge in comparison with the products of the humic acids of weathered sapromyxite coal.     

Production of Flotation Agents for Coal Cleaning by the Oxidative Modification of Waste Motor Oils

Data on the effects of different oxidative modification methods on the composition and flotation properties of spent mineral motor oils are reported. It was found that the preliminary ozonization of waste oils, in contrast to their thermal oxidation and treatment with hydrogen peroxide, increased the efficiency of the flotation of coking coal. The flotation properties of ozonized waste oils are improved due to a decrease in the viscosity and the appearance of heteropolar compounds in their composition, as a result of which the reagent acquires the complex properties of a collector and a foaming agent.     

煤基直接碳燃料电池硫处理工艺探索

煤炭是我国的主要能源,以燃烧煤为主的煤炭利用过程产生了大量的温室气体CO2、含硫化合物气体等。通过煤基直接碳燃料电池发电,理论热力学效率接近100%,而且可以实现CO2的零排放,是煤高效、低碳洁净利用的关键技术,其大规模推广应用却受到原煤含硫化合物引起的硫中毒的制约。通过对现有煤脱硫工艺进行分析,提出洗选→化学氧化→电化学氧化→离子液体萃取→溶剂萃取→高温固硫(PCESTO)阶段联合处理工艺对原煤进行脱硫处理,可以有效降低煤中硫含量,定向转化直接碳燃料电池中硫的存在形式,减少和消除硫对直接碳燃料电池电极的毒化作用。     

Organic Compounds in Glass Modification Technology (A Review)

The specifics of application of organic compounds in glass modification technology (aliphatic alcohols and ketones, organic acids and their salts, and organosilicon compounds) compared to the use of inorganic compounds are considered. It is demonstrated that treatment of the glass surface with organic compounds can improve mechanical, chemical, calorimetric, biochemical, and other properties of glasses.     

Conditioning of coal-enrichment waste with high moisture and ash content

The processing of coal-enrichment waste with high moisture and ash content is considered. Existing methods—filtration and thermal drying—are very complex and energy-intensive and have considerable environmental impact. An alternative is adsorption on lignite coke produced in the Krasnoyarsk region by thermal oxidation. Termokoks-KS lignite coke, which is low in ash and sulfur, resembles activated charcoal in its absorption properties. Experiments show that, when mixed with coal wastes, it produces a fuel blend characterized by lower ash content, satisfactory friability, and high energy yields. An industrial technology for such conditioning of coal wastes is described.     

Soil and Water Decontaminaton by Extraction with Surfactants

Abstract

Samples of soil from contaminated sites and industrial sludges and residues were treated in the laboratory by extraction with water solutions containing surfactants and other additives. The contaminants included coal tar, PCBs, hydrocarbons, chlorinated hydrocarbons, nitrotoluenes and heavy metals. Some of the samples contained highly complex mixtures of organic and heavy metal contaminants. Reduction of the contaminant levels to less than 1 ppm was typically attained by the extraction treatment. The contaminant-laden wash liquors were purified by ultrafiltration, followed by air flotation. The cost of treatment by a commercial-scale, integrated process, consisting of the extraction and wash liquor purification steps, was estimated to be in the range of $50 – $80 per ton of treated soil, depending on soil matrix properties, chemical composition of the contaminants, and other site-specific factors.     

The enrichment of fine particles of coal by aggregation part II. The use of the selective aggreagation method

Tests on aggregation enrichement of fine particles of coal are presented. The selective aggregation process, named ‘shear flocculation’ by Warren [7, 8], was conducted in a cylindrical beaker. The aggregation of the coal grains results from the action of shear forces while the feed is mixing with the collector (diesel oil). The aggregates formed were then separated from gangue by aeration in a flotation machine. This allows for almost complete recovery of coal. Preliminary aggregation of coal grains made it possible to eliminate the frothing agents usually needed in such a process.     

Composition, structure, and properties of coal from the 2.2 Ulug bed of the Elegestsk deposit in Ulug-Khemsk coal basin

Coal from the 2.2 Ulug bed of the Elegestsk deposit in Ulug-Khemsk coal basin is investigated in terms of international quality certification. According to State Standard GOST 25543-88, the coal is of rank Zh and technological group 2Zh. The coal’s code according to the international system and State Standard GOST 30313-95 is 08 0 01 8 38 05 04 36. Attention is paid to the composition and structure of the coal, which are associated with elevated clinkering properties at high vitrinite reflectance, as well as maximum yield and fluidity of thermostable liquid products in the coal’s plastic mass. These features indicate that the coal’s organic mass contains considerable quantities of thermally unstable hydroaromatic and aliphatic structures. On account of the low oxygen content in the organic mass of coal from the Ulug bed, with high quantities of carbon and hydrogen, much of the hydrogen formed on thermal destruction reacts with the radicals formed, which prevents their polycondensation, and considerable quantities of relatively low-molecular liquid products of the plastic mass are produced. The mineral component is characterized by low content of silicon and aluminum oxides (51.65%) and relatively high content of iron oxide (15.96%) and calcium oxide (15.07%). Accordingly, the base/acid ratio I _b and basicity index B _b are high: 0.692 and 6.29, respectively. The Donets Basin has no counterparts of this coal. Coal from the 2.2 Ulug bed of the Elegestsk deposit in Ulug-Khemsk coal basin may be regarded as a valuable component of coal batch.