STATISTICAL ANALYSIS OF ORGANOSULFUR EXTRACTION DATA OF OHIO 5/6 COAL USING THE PERCHLOROETHYLENE COAL CLEANING PROCESS

ABSTRACT

The perchloroethylene coal cleaning process removes both organic and pyritic forms of sulfur using perchloroethylene as the solvent medium. The effect of process variables including temperature, extraction time, solvent to coal ratio and particle size of coal has been studied by a systematic 2⁴ full factorial experimental design with a single replicate. The process was found to be strongly dependent on the type of coal. Hence, this variable was controlled by choosing one single type of coal, i.e., Ohio 5/6 (1:1 mixture of Ohio 5 and Ohio 6 coals) throughout this entire investigation. The significant effects and interactions have been quantified by F-tests. The estimates of significant effects have been obtained by Yates algorithm. Residual probability and normal probability plots have been obtained to test model adequacy. Finally, a computational model has been developed to predict the organosulfur extraction efficiency of this coal at various values of process variables. The parity plots conclude that the model has a good interpolational predictive capability.     

REACTOR MODELING AND SIMULATION OF PERCHLOROETHYLENE EXTRACTION DESULFURIZATION OF COAL

Desulfurization of coal by perchloroethylene extraction is based on a complex and hybrid system of chemical reaction and solvent extraction. Batcb kinetic studies have shown that the reaction follows a pseudo-first order rate kinetics. The batch kinetic data have been used to estimate first order rate parameters. In this paper, these parameters have been used to develop models for batch, plug-flow (PFR), single and continuous stirred tank reactor (CSTR). Simulation studies have been conducted to obtain exit concentrations of these reactors. A new parameter, called "Performance Index", has been developed in order to compare the performances of various reactors. In order to arrive at relevant conclusions, simulation studies have been conducted on three different types of coals. It was found from the simulation results that the batch reactor performance coincided with the experimental data, indicating a good predictive capability of the model. It was also found that coals of different types differed in their kinetic behavior, and thus, the reactor design to achieve optimal conversion is a strong function of the type of coal. Finally, given the kinetic data for a specific type of coal, the "Residence Time Curves" for CSTR determine the most optimal reactor design. This investigation is very significant from the point of reactor design and perchloroethylene coal cleaning process development.     

REACTOR MODELING AND SIMULATION OF PERCHLOROETHYLENE EXTRACTION DESULFURIZATION OF COAL

ABSTRACT

Desulfurization of coal by perchloroethylene extraction is based on a complex and hybrid system of chemical reaction and solvent extraction. Batcb kinetic studies have shown that the reaction follows a pseudo-first order rate kinetics. The batch kinetic data have been used to estimate first order rate parameters. In this paper, these parameters have been used to develop models for batch, plug-flow (PFR), single and continuous stirred tank reactor (CSTR). Simulation studies have been conducted to obtain exit concentrations of these reactors. A new parameter, called "Performance Index", has been developed in order to compare the performances of various reactors. In order to arrive at relevant conclusions, simulation studies have been conducted on three different types of coals. It was found from the simulation results that the batch reactor performance coincided with the experimental data, indicating a good predictive capability of the model. It was also found that coals of different types differed in their kinetic behavior, and thus, the reactor design to achieve optimal conversion is a strong function of the type of coal. Finally, given the kinetic data for a specific type of coal, the "Residence Time Curves" for CSTR determine the most optimal reactor design. This investigation is very significant from the point of reactor design and perchloroethylene coal cleaning process development.     

REMOVAL OF RESIDUAL CHLORINE FROM INDIANA 5 COAL BY SUPERCRITICAL CARBON DIOXIDE EXTRACTION

The perchloroethylene coal desulfurization process has unique advantages as a precombustion coal cleaning process, that include high cleaning efficiencies, mild process conditions, minimal output of undesirable byproducts, and cost effectiveness. However, the use of perchloroethylene in the process renders an important process engineering problem of complete recovery and reuse of perchloroethylene. thus requiring a “zero discharge” condition of the solvent. Therefore, the treated coal must be stripped of any residual perchloroethylene. Carbon dioxide (CO₂) in its supercritical state has been investigated for its ability to remove chlorine from Indiana 5 coal, that has been desulfurized by the perchloroethylene (PCE) process. The reduction of CI contenttffrom a PCE treated and filtered coal has been as high as 78% The exprements have been carried out. following a statistical experimental design and the discerning characteristics of the process been identified. The solvent density and extraction conditions can be tailored in such a way as to optimally remove CI from the coal without any detrimental effects on the coal matrix. The supercritical CO₂ extraction process can be successfully implemented to the PCE coal cleaning process by replacing energy intensive steps of steam stripping and vacuum dying     

REMOVAL OF RESIDUAL CHLORINE FROM INDIANA 5 COAL BY SUPERCRITICAL CARBON DIOXIDE EXTRACTION

ABSTRACT

The perchloroethylene coal desulfurization process has unique advantages as a precombustion coal cleaning process, that include high cleaning efficiencies, mild process conditions, minimal output of undesirable byproducts, and cost effectiveness. However, the use of perchloroethylene in the process renders an important process engineering problem of complete recovery and reuse of perchloroethylene. thus requiring a “zero discharge” condition of the solvent. Therefore, the treated coal must be stripped of any residual perchloroethylene. Carbon dioxide (CO₂) in its supercritical state has been investigated for its ability to remove chlorine from Indiana 5 coal, that has been desulfurized by the perchloroethylene (PCE) process. The reduction of CI contenttffrom a PCE treated and filtered coal has been as high as 78% The exprements have been carried out. following a statistical experimental design and the discerning characteristics of the process been identified. The solvent density and extraction conditions can be tailored in such a way as to optimally remove CI from the coal without any detrimental effects on the coal matrix. The supercritical CO₂ extraction process can be successfully implemented to the PCE coal cleaning process by replacing energy intensive steps of steam stripping and vacuum dying     

EFFECT OF FILTRATION TEMPERATURE ON ORGANIC SULFUR REMOVAL FROM COAL BY PERCHLOROETHYLENE COAL CLEANING PROCESS

The perchloroethylene extraction desulfurization process removes the organic sulfur in coal via a hybrid mechanism of solvent extraction and chemical reaction. The nature and extent of the reaction is controlled by the extraction time and temperature of operation. Although the extraction temperature is kept identical for all types of coals (120°C), the organosulfur extraction time still depends upon the type of coal. If the reaction mixture is left too long in the extraction environment, the intermediate labile sulfur released by the reaction forms cross-links with the organic matter in the macromolecule of coal. This is detrimental to the process efficiency. Constant temperature has to be maintained throughout the extraction, till coal is separated from the solvent. If not, the extracted labile sulfur re-enters the coal macromolecule to form inter-penetrating polymer networks with the organic matter in coal. In this paper, it has been established that the time required for separation and isothermality of the process are crucial to maintain the reaction progressing toward sulfur and organic sulfur liberation from the macromolecule. The data presented in this paper are important from the viewpoint of process development, because the process mandates the separation of coal and solvent at the operating temperature.     

EFFECT OF FILTRATION TEMPERATURE ON ORGANIC SULFUR REMOVAL FROM COAL BY PERCHLOROETHYLENE COAL CLEANING PROCESS

Abstract

The perchloroethylene extraction desulfurization process removes the organic sulfur in coal via a hybrid mechanism of solvent extraction and chemical reaction. The nature and extent of the reaction is controlled by the extraction time and temperature of operation. Although the extraction temperature is kept identical for all types of coals (120°C), the organosulfur extraction time still depends upon the type of coal. If the reaction mixture is left too long in the extraction environment, the intermediate labile sulfur released by the reaction forms cross-links with the organic matter in the macromolecule of coal. This is detrimental to the process efficiency. Constant temperature has to be maintained throughout the extraction, till coal is separated from the solvent. If not, the extracted labile sulfur re-enters the coal macromolecule to form inter-penetrating polymer networks with the organic matter in coal. In this paper, it has been established that the time required for separation and isothermality of the process are crucial to maintain the reaction progressing toward sulfur and organic sulfur liberation from the macromolecule. The data presented in this paper are important from the viewpoint of process development, because the process mandates the separation of coal and solvent at the operating temperature.     

IMPREGNATION AND RECOVERABILITY OF ELEMENTAL SULFUR IN COAL USING THE PERCHLOROETHYLENE DESULFURIZATION PROCESS

During the perchloroethylene extraction process, C-S bond cleavage reactions occur, which liberate labile sulfur from the organic matrix of coal into the solvent medium i.e., perchloroethylene, where it is dissolved and extracted. In this paper, the effect of impregnation of elemental sulfur in raw coal on its forms of sulfur analyses has been investigated. The effect of the same sulfur-impregnated coal on its organosulfur extractability has also been explored. Studies were conducted to observe whether the impregnated elemental sulfur was fully recoverable by the perchloroethylene extraction process. It was observed that sulfur can be very easily impregnated into the microstructure of coal. On the basis of tests on raw and impregnated coals, based on ASTM D-2492 standard, the impregnated sulfur reflects mostly in the form of organic sulfur. The impregnated sulfur which appears in the form of organic sulfur is fully recoverable via the perchloroethylene extraction     

IMPREGNATION AND RECOVERABILITY OF ELEMENTAL SULFUR IN COAL USING THE PERCHLOROETHYLENE DESULFURIZATION PROCESS

ABSTRACT

During the perchloroethylene extraction process, C-S bond cleavage reactions occur, which liberate labile sulfur from the organic matrix of coal into the solvent medium i.e., perchloroethylene, where it is dissolved and extracted. In this paper, the effect of impregnation of elemental sulfur in raw coal on its forms of sulfur analyses has been investigated. The effect of the same sulfur-impregnated coal on its organosulfur extractability has also been explored. Studies were conducted to observe whether the impregnated elemental sulfur was fully recoverable by the perchloroethylene extraction process. It was observed that sulfur can be very easily impregnated into the microstructure of coal. On the basis of tests on raw and impregnated coals, based on ASTM D-2492 standard, the impregnated sulfur reflects mostly in the form of organic sulfur. The impregnated sulfur which appears in the form of organic sulfur is fully recoverable via the perchloroethylene extraction     

ENVIRONMENTAL AND ECONOMIC ISSUES IN THE USE OF PERCHLOROETHYLENE AS THE SOLVENT IN PERCHLOROETHYLENE COAL CLEANING PROCESS

The Perchloroethylene coal cleaning process effectively removes both organic and inorganic forms of sulfur in coal. Complete recyclability of the solvent is the key to both economic and environmental issues concerning the use of perchloroethylene in this process. Recyclability of the solvent has been fully established by repeated batch operation as well as FTIR structural investigations of solvent molecules. In the current investigation, the solvent has been subjected to various analyses after each stage in the operation i.e., before extraction, after extraction and after distillation. The organic desulfurization is based on an extraction-reaction mechanism and is catalyzed by the mineral matter inherently and naturally present in coal. This paper also aims at studying the role played by the solvent (perchloroethylene) in the extraction process as well as in the catalytic reaction occurring in the system. This paper also presents data on the effect of re-using 'sulfur-rich mother liquor', rich in extracted sulfur, on the organosulfur extraction efficiency. These data are very important from the point of view of process engineering and economics.     

ENVIRONMENTAL AND ECONOMIC ISSUES IN THE USE OF PERCHLOROETHYLENE AS THE SOLVENT IN PERCHLOROETHYLENE COAL CLEANING PROCESS

ABSTRACT

The Perchloroethylene coal cleaning process effectively removes both organic and inorganic forms of sulfur in coal. Complete recyclability of the solvent is the key to both economic and environmental issues concerning the use of perchloroethylene in this process. Recyclability of the solvent has been fully established by repeated batch operation as well as FTIR structural investigations of solvent molecules. In the current investigation, the solvent has been subjected to various analyses after each stage in the operation i.e., before extraction, after extraction and after distillation. The organic desulfurization is based on an extraction-reaction mechanism and is catalyzed by the mineral matter inherently and naturally present in coal. This paper also aims at studying the role played by the solvent (perchloroethylene) in the extraction process as well as in the catalytic reaction occurring in the system. This paper also presents data on the effect of re-using ‘sulfur-rich mother liquor’, rich in extracted sulfur, on the organosulfur extraction efficiency. These data are very important from the point of view of process engineering and economics.     

FRICTION AND WEAR TESTING FOR COAL SLURRY FUEL DEVELOPMENT

Friction and wear characteristics of coal slurries in transportation and atomization/firing systems are areas of concern in considering their use as substitutes for neat liquid fuels. The main wear phenomena encountered in slurry fuel usage are erosive and sliding wear of metal surfaces in contact with the coal slurry. Laboratory experiments have been devised and carried out to characterize and better understand these slurry wear mechanisms. The dependence of wear on the characteristics of the coal slurry and the properties of the wear surfaces have been studied. Coal slurries prepared from an Ohio coal desulfurized using a novel perchloroethylene extraction process have been studied. A Cameron-Flint reciprocating slider tribometer has been used to study sliding wear phenomena. Erosive wear has been investigated using an impingement type wear tester. The importance of impingement angle of coal slurry on platelet formation during erosion has been determined. Results of This angle corresponding to peak erosion is lover than for the softer 1020 steel, and can be attributed to the hardness of the steels.

Wear tests on 1020 steel were carried out using coal slurries formulated from run-of-mine coal and coal freed of mineral matter and organic sulfur by the perchloroethylene coal cleaning process (Lee et al., 1989). It was observed that run-of-mine coal created two kinds of indentations on the 1020 steel - larger indentations attributable to large mineral matter particles, and smaller indents. Only smaller indents were present in the wear tests with a slurry prepared with cleaned coal, which was largely freed of mineral matter.     

FRICTION AND WEAR TESTING FOR COAL SLURRY FUEL DEVELOPMENT

ABSTRACT

Friction and wear characteristics of coal slurries in transportation and atomization/firing systems are areas of concern in considering their use as substitutes for neat liquid fuels. The main wear phenomena encountered in slurry fuel usage are erosive and sliding wear of metal surfaces in contact with the coal slurry. Laboratory experiments have been devised and carried out to characterize and better understand these slurry wear mechanisms. The dependence of wear on the characteristics of the coal slurry and the properties of the wear surfaces have been studied. Coal slurries prepared from an Ohio coal desulfurized using a novel perchloroethylene extraction process have been studied. A Cameron-Flint reciprocating slider tribometer has been used to study sliding wear phenomena. Erosive wear has been investigated using an impingement type wear tester. The importance of impingement angle of coal slurry on platelet formation during erosion has been determined. Results of This angle corresponding to peak erosion is lover than for the softer 1020 steel, and can be attributed to the hardness of the steels.

Wear tests on 1020 steel were carried out using coal slurries formulated from run-of-mine coal and coal freed of mineral matter and organic sulfur by the perchloroethylene coal cleaning process (Lee et al., 1989). It was observed that run-of-mine coal created two kinds of indentations on the 1020 steel - larger indentations attributable to large mineral matter particles, and smaller indents. Only smaller indents were present in the wear tests with a slurry prepared with cleaned coal, which was largely freed of mineral matter.     

EFFECT OF MOISTURE IN COAL ON ITS ORGANIC SULFUR EXTRACTABILITY

The extent of organic sulfur removed by the perchloroethylene desulfurization process depends upon several factors including the type of coal, the amount of catalyst present in it, and the temperature of organosulfiir extraction. Moisture in coal also plays a very important role in this extraction process. In this paper, the role played by moisture and its subsequent effect on the process efficiency has been investigated. It has been found that the moisture in coal affects the extraction process in two ways. Firstly, in presence of water, the temperature of the operation is reduced. This affects the organosulfiir extraction efficiency adversely. Secondly, the naturally available catalytic ingredients in coal, essential for the organosulfiir extraction, are soluble in water. Therefore, in presence of water, the catalytic potency of these catalytic species is lost, and thus reducing the organosulfiir extractability. The data presented in this paper are also important from the point of view of process development, because it has been experimentally established that the moisture content in coal has to be sufficiently reduced in order to improve the overall process efficiency.     

EFFECT OF MOISTURE IN COAL ON ITS ORGANIC SULFUR EXTRACTABILITY

Abstract

The extent of organic sulfur removed by the perchloroethylene desulfurization process depends upon several factors including the type of coal, the amount of catalyst present in it, and the temperature of organosulfiir extraction. Moisture in coal also plays a very important role in this extraction process. In this paper, the role played by moisture and its subsequent effect on the process efficiency has been investigated. It has been found that the moisture in coal affects the extraction process in two ways. Firstly, in presence of water, the temperature of the operation is reduced. This affects the organosulfiir extraction efficiency adversely. Secondly, the naturally available catalytic ingredients in coal, essential for the organosulfiir extraction, are soluble in water. Therefore, in presence of water, the catalytic potency of these catalytic species is lost, and thus reducing the organosulfiir extractability. The data presented in this paper are also important from the point of view of process development, because it has been experimentally established that the moisture content in coal has to be sufficiently reduced in order to improve the overall process efficiency.     

REMOVAL OF RESIDUAL CHLORINE IN COAL BV STEAM STRIPPING

As a part of process engineering study of the perchloroethylene (PCE) coal desulfurization process, the minimization of residual chlorine content after the desulfurization process has been studied in detail. The residual chlorine in the coal is removed by a novel process, which involves the use of steam as the displacing agent. Steam, when passed through a bed of the PCE treated coal, washes away the residual solvent in coal. Two designs, viz. fluidized bed and packed bed steam strippers are discussed in detail. This paper presents the results of the design implementations and discusses the advantages and disadvantages of each design. It was found that the chlorine content of the coal treated in the packed bed steam stripper was not only decreased to a level lower than before steam stripping, but to a level lower than that of the raw samples before the PCE extraction.     

SUPERCRITICAL EXTRACTION OF ORGANOSULFUR FROM COAL USING ACETONE-VATER MIXTURES

Binary mixtures of acetone and water at their supercritical conditions have been investigated for their ability to remove organic sulfur from high sulfur Midwestern coals. The reduction of organic sulfur from Ohio 5/6 and Indiana 5 coals has been as high as 61% (based on a BTU basis) The experiments have been carried out following a statistical experimental design and the optimal process conditions and discerning characteristics of the process have been identified. The solvent composition and the extraction conditions can be tailored in such a way as to selectively remove sulfur and further increase the calorific value of the treated coal.     

REMOVAL OF RESIDUAL CHLORINE IN COAL BV STEAM STRIPPING

ABSTRACT

As a part of process engineering study of the perchloroethylene (PCE) coal desulfurization process, the minimization of residual chlorine content after the desulfurization process has been studied in detail. The residual chlorine in the coal is removed by a novel process, which involves the use of steam as the displacing agent. Steam, when passed through a bed of the PCE treated coal, washes away the residual solvent in coal. Two designs, viz. fluidized bed and packed bed steam strippers are discussed in detail. This paper presents the results of the design implementations and discusses the advantages and disadvantages of each design. It was found that the chlorine content of the coal treated in the packed bed steam stripper was not only decreased to a level lower than before steam stripping, but to a level lower than that of the raw samples before the PCE extraction.     

PERCHL0R0ETHYLENE EXTRACTION DESULFURIZATION OF WEATHERED COALS

Abstract

The perchloroethylene extraction process has proven to be an effective pre- combustion coal desulfurization process which offers a complete process package including wet grinding, organic sulfur removal, pyrite and mineral matter separation, solvent recovery, and byproducts and sulfur recovery. In this paper, coal weatherability was investigated for various Midwestern and Eastern U.S. coals, and its effect on organosulfur extractability by the perchloroethylene process was identified. Both “natural” and “artificial” weathering of these coals were experimentally investigated. A statistically significant difference in the extraction efficiency between fresh and weathered coals vas observed. A strong relation between the extractability and degree of weathering of the coal was established. The results provide a valuable insight into the process engineering of this process.     

STATISTICAL ANALYSIS OF REACTION RATE DATA OF LIQUID PHASE SYNTHESIS OF DIMETHYL ETHER FROM METHANOL

The liquid phase catalytic dehydration of methanol to dimethyl ether (DME) is a key reaction step in the single-step synthesis of DME from CO-rich syngas in a slurry reactor. The effect of process variables including temperature, pressure, impeller speed, and feed methanol flow rate on DME synthesis rate has been studied by a systematic 24 full factorial experimental design with single replicate. The significant effects and interactions have been quantified by F-tests. The estimates of significant effects have been obtained by Yates' algorithm. Residual probability and normal probability dots have been obtained to test model adequacy. Finally, a computational model has been developed to predict the DME synthesis rate alt various values of process variables. The model has excellent interpolational predictive capability as evidenced by parity plots.