Guy H. Harris

An improved class of universal collectors for the flotation of oxidized and/or low-rank coal

Ash minerals, including pyrite, can be separated from coal by flotation, primarily making use of the natural hydrophobicity of the carbonaceous matter in coal. However, to overcome the deleterious effect of oxygen functional groups on the coal surface, an organic collector is required. The most common industrial coal flotation collector is fuel oil, but the addition of oxygenated functional groups to the collector molecule markedly enhances the flotation of lower rank and oxidized coals. This paper summarizes the results of detailed study of the flotation response of two high-sulfur coals, Illinois No. 6 coal and Pittsburgh No. 8, using different non-ionic oxygenated surfactants as the collector. The performance of these reagents is compared with that of two oily collectors, namely dodecane and nonylbenzene, and mechanisms for the interaction of these compounds with coal are suggested.

Coal Flotation with Nonionic Surfactants

Abstract The flotation response of two high-sulfur coals to a variety of collectors was studied in detail using a 2-liter Denver flotation cell. In comparison with dodecane as the standard oily collector, the introduction of a benzene ring into the oily collector can significantly improve its collecting ability for coal. In our two series of compounds containing oxygenated functional groups, it was necessary to incorporate a benzene ring in the molecular structure in order to have an effective collector without die use of dodecane. The results showed that a much lower dosage of these nonionic surfactants was required to achieve the same coal recovery as compared with dodecane. Most important was the performance of these compounds as promoters for oxidized as well as unoxidized coal. Mechanisms of interaction of these compounds with coal are suggested

Chemical Reagents for Enhanced Coal Flotation

Designing new reagents is of vital importance for the flotation of coal, especially for processing low-rank and/or oxidized coals, which are difficult to float with commonly used fuel oil or kerosene because of the high surface oxygen content. Because of the complex nature of coal surfaces, both hydrogen bonding and aromatic-aromatic interactions were considered in searching for more effective coal collectors. The flotation of two high-sulfur coals was studied in detail, using a series of nonionic surfactants as collectors containing oxygenated as well as aromatic functional groups. Most of the work was conducted with tetra-hydrofurfuryl esters (THF) as the coal collectors, and the performance of these reagents was compared with that of two oily collectors, namely dodecane and nonylbenzene. With some of the reagents, comparable combustible matter recovery can be achieved at a fraction of the dosage of dodecane collector required. More important was the performance of these compounds as promoters for oxidized coal flotation. Finally, joint collector flotation experiments were conducted, and the results showed that a very small addition of a THF reagent before the dodecane addition greatly enhances the flotation of coal. Mechanisms of interaction of these compounds with coal are suggested.

Evaluation of flotation collectors for copper sulfides and pyrite, III. Effect of xanthate chain length and branching

Abstract The flotation of four copper sulfide minerals (chalcopyrite, chalcocite, bornite, covellite) and pyrite with xanthates shows that a minimum in the collector concentration necessary for flotation usually occurs at about C-5 (amyl) to C-8 (octyl) for the straight chain xanthates. Comparison of straight-chain and branched-chain compounds demonstrated that while short, branched chain xanthates out perform their straight chain analogs, above ∼ C-5 the branched-chain xanthates are less effective as compared to the straight chain form. When Cu2+ is added to the flotation system, it was found that a minimal amount will often produce an enhanced flotation recovery, while greater amounts will either produce essentially no effect or may cause a slight decrease in flotation.

An improved class of flotation frothers

Abstract Incorporating certain functional groups or atoms into surfactant molecules can have a dramatic impact on the surface activity of the chemicals. This paper summarizes how the introduction of sulfur atom into polyalkylene oxide frother molecules increased metal recovery, both copper and molybdenum, in the flotation of porphyrry ores. Both hydrophile–lipophile balance (HLB) numbers and collector/frother/mineral interactions are considered to play a role in enhancing recovery.

Use of xanthogen formates as collectors in the flotation of copper sulfides and pyrite

Abstract Though xanthogen formates have long been used as sulfide mineral collectors, they have been largely ignored by the research community. The flotation of chalcopyrite, chalcocite, covellite, bornite and pyrite with this class of collector has been evaluated using a variety of hydrocarbon constituent groupings, in both the xanthogen and the formate positions. In addition to being stable in acidic circuits, xanthogen formates are shown to be effective copper sulfide collectors over a broad pH range (5.0–10.5). In general, many of the nine especially synthesized xanthogen formates were found to discriminate against the flotation of pyrite. It is possible to tailor make these compounds to enhance or diminish the flotation of pyrite.

Coal surface control for advanced fine coal flotation

The primary objective of this research project is to develop advanced flotation methods for coal cleaning in order to achieve near total pyritic-sulfur removal at 90% Btu recovery, using coal samples procured from six major US coal seams. Concomitantly, the ash content of these coals is to be reduced to 6% or less. Work this quarter concentrated on the following: washability studies, which included particle size distribution of the washability samples, and chemical analysis of washability test samples; characterization studies of induction time measurements, correlation between yield, combustible-material recovery (CMR), and heating-value recovery (HVR), and QA/QC for standard flotation tests and coal analyses; surface modification and control including testing of surface-modifying reagents, restoration of hydrophobicity to lab-oxidized coals, pH effects on coal flotation, and depression of pyritic sulfur in which pyrite depression with calcium cyanide and pyrite depression with xanthated reagents was investigated; flotation optimization and circuitry included staged reagent addition, cleaning and scavenging, and scavenging and middling recycling. Weathering studies are also discussed. 19 figs., 28 tabs.

Surface Chemistry and Rheology of Pittsburgh No. 8 Coal-Water Slurry in the Presence of a New Pyrite Depressant

The preparation of Pittsburgh No.8 coal-water slurry requires a clean coal; thus, ash and pyrite must be rejected. For this purpose, Pittsburgh No. 8 coal was floated in the presence of a new family of pyrite depressant. To understand the effect of these reagents on the depression of pyrite during coal flotation, both the surface chemistry and the rheology of coal-pyrite systems must be studied. This paper summarizes the results of flotation tests at a 200 mesh of grind of Pittsburgh No. 8 coal using TEPA reagent for pyrite depression. The flotation results using TEPA show an increase of 5% in pyritic sulfur rejection (equivalent to 20% rejection of the remaining pyrite in the concentrate) at equal combustible material recovery (60%) as compared with the case when no depressant was used. Chemical and electrokinetic studies for Pittsburgh No. 8 coal and pyrite were performed to determine the effect of coal cleaning and that of this new reagent on the surface charges of coal and pyrite. The rheology of Pitt...

Principles and practice of sulphide mineral flotation

This paper presents both the fundamentals of sulphide mineral flotation and the practical aspects of sulphide ore flotation. The fundamental aspects of the flotation of sulphide minerals both in the absence and presence of thiol collectors are discussed in relation to their crystal structure, surface chemistry and electrochemical characteristics. Since the electrochemistry of the sulphide mineral/aqueous solution interface and of various sulphide mineral/aqueous thio-compound systems has been amply investigated over the past two decades, the results of these modern electrochemical studies are briefly reviewed. Mechanisms of the action of various flotation reagents, including collectors, activators and depressants, commonly used in sulphide mineral flotation are discussed in terms of the chemical and electrochemical principles presented within this paper. Simplified flow sheets of representative flotation plant operations are given to illustrate how these principles are applied for the commercial separation of sulphide minerals from their ores. Various novel techniques that take advantage of controlling the electrochemical and physical behavior of the flotation system are also presented.