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Title: Development of enhanced sulfur rejection processes

Abstract

Research at Virginia Tech led to two complementary concepts for improving the removal of inorganic sulfur from much of the Eastern US coals. One controls the surface properties of coal pyrite (FeS[sub 2]) by electrochemical-.potential control, referred to as the Electrochemically Enhanced Sulfur Rejection (EESR) Process: The second controls the flotation of middlings, i.e., particles composed of pyrite with coal inclusions by using polymeric reagents to react with pyrite and convert the middlings to hydrophilic particles, and is termed the Polymer Enhanced Sulfur Rejection (PESR) Process. These new concepts are based on recent research establishing the two main reasons why flotation fails to remove more than about 50% of the pyritic sulfur from coal: superficial oxidization of liberated pyrite to form polysulfide oxidation products so that a part of the liberated pyrite floats with the coal; and hydrophobic coal inclusions in the middlings dominating their flotation so that the middlings also float with the coal. These new pyritic-sulfur rejection processes do not require significant modifications of existing coal preparation facilities, enhancing their adoptability by the coal industry. It is believed that they can be used simultaneously to achieve both free pyrite and locked pyrite rejection.

Authors:
; ; ;
Publication Date:
Research Org.:
Virginia Center for Coal and Minerals Processing, Blacksburg, VA (United States)
Sponsoring Org.:
DOE; USDOE, Washington, DC (United States)
OSTI Identifier:
6690882
Alternate Identifier(s):
OSTI ID: 6690882; Legacy ID: DE93011460
Report Number(s):
DOE/PC/92246-T1
ON: DE93011460
DOE Contract Number:
AC22-92PC92246
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; COAL PREPARATION; DESULFURIZATION; PYRITE; REMOVAL; FLOTATION; PLANNING; PROGRESS REPORT; CHEMICAL REACTIONS; DOCUMENT TYPES; MINERALS; SEPARATION PROCESSES; SULFIDE MINERALS 010300* -- Coal, Lignite, & Peat-- Preparation-- (1987-)

Citation Formats

Yoon, R.H., Luttrell, G., Adel, G., and Richardson, P.E.. Development of enhanced sulfur rejection processes. United States: N. p., 1993. Web. doi:10.2172/6690882.
Yoon, R.H., Luttrell, G., Adel, G., & Richardson, P.E.. Development of enhanced sulfur rejection processes. United States. doi:10.2172/6690882.
Yoon, R.H., Luttrell, G., Adel, G., and Richardson, P.E.. Tue . "Development of enhanced sulfur rejection processes". United States. doi:10.2172/6690882. https://www.osti.gov/servlets/purl/6690882.
@article{osti_6690882,
title = {Development of enhanced sulfur rejection processes},
author = {Yoon, R.H. and Luttrell, G. and Adel, G. and Richardson, P.E.},
abstractNote = {Research at Virginia Tech led to two complementary concepts for improving the removal of inorganic sulfur from much of the Eastern US coals. One controls the surface properties of coal pyrite (FeS[sub 2]) by electrochemical-.potential control, referred to as the Electrochemically Enhanced Sulfur Rejection (EESR) Process: The second controls the flotation of middlings, i.e., particles composed of pyrite with coal inclusions by using polymeric reagents to react with pyrite and convert the middlings to hydrophilic particles, and is termed the Polymer Enhanced Sulfur Rejection (PESR) Process. These new concepts are based on recent research establishing the two main reasons why flotation fails to remove more than about 50% of the pyritic sulfur from coal: superficial oxidization of liberated pyrite to form polysulfide oxidation products so that a part of the liberated pyrite floats with the coal; and hydrophobic coal inclusions in the middlings dominating their flotation so that the middlings also float with the coal. These new pyritic-sulfur rejection processes do not require significant modifications of existing coal preparation facilities, enhancing their adoptability by the coal industry. It is believed that they can be used simultaneously to achieve both free pyrite and locked pyrite rejection.},
doi = {10.2172/6690882},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Mar 23 00:00:00 EST 1993},
month = {Tue Mar 23 00:00:00 EST 1993}
}

Technical Report:

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  • Research at Virginia Tech led to the development of two complementary concepts for improving the removal of inorganic sulfur from many eastern U.S. coals. These concepts are referred to as Electrochemically Enhanced Sulfur Rejection (EESR) and Polymer Enhanced Sulfur Rejection (PESR) processes. The EESR process uses electrochemical techniques to suppress the formation of hydrophobic oxidation products believed to be responsible for the floatability of coal pyrite. The PESR process uses polymeric reagents that react with pyrite and convert floatable middlings, i.e., composite particles composed of pyrite with coal inclusions, into hydrophilic particles. These new pyritic-sulfur rejection processes do not requiremore » significant modifications to existing coal preparation facilities, thereby enhancing their adoptability by the coal industry. It is believed that these processes can be used simultaneously to maximize the rejection of both well-liberated pyrite and composite coal-pyrite particles. The project was initiated on October 1, 1992 and all technical work has been completed. This report is based on the research carried out under Tasks 2-7 described in the project proposal. These tasks include Characterization, Electrochemical Studies, In Situ Monitoring of Reagent Adsorption on Pyrite, Bench Scale Testing of the EESR Process, Bench Scale Testing of the PESR Process, and Modeling and Simulation.« less
  • Pyrite becomes hydrophobic upon superficial oxidation and floats without a collector. The flotation begins to occur at potentials above the stable potentials identified by the chronoamperometry experiments conducted with freshly fractured pyrite. This finding suggests that iron polysulfide, formed during the initial stages of oxidation, is responsible for the flotation. The collectorless flotation is suppressed above the potential where the mineral is aggressively oxidized, forming iron hydroxide and soluble sulfoxy species. The collectorless flotation is less significant at pH 9.2 than at pH 4.6, possibly due to the formation of iron hydroxide. At pH 9.2, the collectorless flotation increases inmore » the presence of EDTA and hydrocarbon oil. The collectorless flotation of pyrite can be suppressed by galvanically coupling the mineral with reactive metals such as aluminum, manganese, and zinc. This effectively prevents the mineral from oxidation. The microflotation tests conducted with mono-sized pyrite samples show that the collectorless flotation can be suppressed effectively in the presence of metal powders. Bench-scale flotation experiments conducted using Denver laboratory flotation cell and a 2-inch diameter Microcel flotation column, also demonstrates that the collectorless flotation can be suppressed in the presence of the reactive metals. It has been established that the most important parameters determining the effectiveness of suppressing pyrite flotation by the galvanic coupling technique are the surface area of the galvanic contractors and the solids concentration of the slurry during conditioning.« less
  • Two complementary concepts for improving the removal of inorganic sulfur from many eastern US coals are the Electrochemically Enhanced Sulfur Rejection (EESR) and Polymer Enhanced Sulfur Rejection (PESR). The EESR process uses electrochemical techniques to suppress the formation of hydrophobic oxidation products believed to be responsible for the floatability of coal pyrite. The PESR process uses polymeric reagents that react with pyrite and convert floatable middlings (composite particles composed of pyrite with coal inclusions) into hydrophilic particles. It is believed that these processes can be used simultaneously to maximize the rejection of both well-liberated pyrite and composite coal-pyrite particles. Duringmore » the current reporting period, work was conducted in the following areas: studies of the liberation characteristics of various pyrite samples, identification of oxidation products on pyrite using XPS technique, studies of reagent adsorption on pyrite using FTIR and contact angles, identification of the most effective sacrificial anode material for depressing pyrite, and identification of the most effective polymer for depressing pyrite. Some of the more significant findings made during the current reporting periods are as follows: (1) liberation characteristics of Illinois No. 6 coal have been determined, (2) effects of pH and electrochemical potentials on the flotation of coal and mineral pyrite have been established, (3) an effective method of keeping coal pyrite under reducing conditions and, hence, preventing self-induced flotation has been developed, and (4) an effective polymeric pyrite depressant has been identified.« less
  • Research at Virginia Tech led to the development of two complementary concepts for improving the removal of inorganic sulfur from many eastern US coals. These concepts are referred to as Electrochemically Enhanced Sulfur Rejection (EESR) and Polymer Enhanced Sulfur Rejection (PESR). The EESR process uses electrochemical techniques to suppress the formation of hydrophobic oxidation products believed to be responsible for the floatability of coal pyrite. The PESR process uses polymeric reagents that react with pyrite and convert floatable middlings, i.e., composite particles composed of pyrite with coal inclusions, into hydrophilic particles. These new pyritic-sulfur rejection processes do not require significantmore » modifications to existing coal preparation facilities, thereby enhancing their adoptability by the coal industry. It is believed that these processes can be used simultaneously to maximize the rejection of both well-liberated pyrite and composite coal-pyrite particles. The technical research was initiated on October 1, 1992, and a detailed work plan and work schedule (Task 1) were developed. During this reporting period, research was conducted to evaluate the liberation characteristics of various pyrite samples (Task 2), to further characterize the oxidation behavior of pyrite using electrochemical and X-ray photoelectron spectroscopy and evaluate the use of sacrificial anode materials as a practical method of depressing pyrite (Task 5), and investigate the use of polymers containing a variety of functional groups to depress pyrite (Task 6).« less
  • Research at Virginia Tech led to two complementary concepts for improving the removal of inorganic sulfur from much of the Eastern US coals. One controls the surface properties of coal pyrite (FeS{sub 2}) by electrochemical-.potential control, referred to as the Electrochemically Enhanced Sulfur Rejection (EESR) Process: The second controls the flotation of middlings, i.e., particles composed of pyrite with coal inclusions by using polymeric reagents to react with pyrite and convert the middlings to hydrophilic particles, and is termed the Polymer Enhanced Sulfur Rejection (PESR) Process. These new concepts are based on recent research establishing the two main reasons whymore » flotation fails to remove more than about 50% of the pyritic sulfur from coal: superficial oxidization of liberated pyrite to form polysulfide oxidation products so that a part of the liberated pyrite floats with the coal; and hydrophobic coal inclusions in the middlings dominating their flotation so that the middlings also float with the coal. These new pyritic-sulfur rejection processes do not require significant modifications of existing coal preparation facilities, enhancing their adoptability by the coal industry. It is believed that they can be used simultaneously to achieve both free pyrite and locked pyrite rejection.« less