LIGAND ASSISTED DESULFURIZATION OF LIGNITE USING THE PERCHLOROETHYLENE COAL REFINING PROCESS

ABSTRACT

The perchloroethylene coal refining process was used on North Dakota lignite coal. Effects of extraction time, perchloroethylenexoal ratio and artificial weathering were studied to determine their effects on the removal of organic sulfur. The artificial weathering conditions used were found to be too harsh and caused a decrease in the amount of organic sulfur removed, unlike normal weathering conditions. Additional studies were done involving various ligands, and showed that the addition of certain ligands during the process aided in the extraction of organic sulfur from the coal.     

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     

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     

PROCESS ENGINEERING STUDIES OF THE PERCHLOROETHYLENE COAL CLEANING PROCESS

ABSTRACT

The perchloroethylene coal cleaning process has proven to be very effective in removing both organic and pyritic sulfur from high-sulfur coals. The process removes 30%- 70% of the organic sulfur and 90%- 99% of the pyritic sulfur with very little loss (<1.0 wt%) of hydrocarbons and their heating value. The process has been investigated on a bench- scale and a fully continuous, mini-pilot scale (5 kg/hr). This paper discusses scientific and technological issues related to the process engineering and the reaction chemistry of the process. The objective of this paper is to report the status of the process development and to address the important issues of the process commercializability.     

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.     

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

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.     

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.     

煤气化工艺水煤气脱硫方案的选择

介绍煤化工企业硫回收装置原料气中烃类对硫磺产品的影响,详细剖析烃类在制硫反应炉中的分解过程,对含烃酸性气脱硫方案选择提供指导。     

KINETIC MODELING OF PERCHLOROETHYLENE EXTRACTION DESULFURIZATION OF COALS

ABSTRACT

The kinetic modeling of the perchloroethylene reaction-extraction process has been carried out on the basis of batch extraction data. In this paper, modeling results of both second order as well as the pseudo-first order model has been presented. Multiple parameter estimates have been found which minimize the model-data discrepancies. Novel methods have been devised to illustrate multiple estimates of the kinetic parameters. Ill-posedness of the kinetic modeling problem bas been analyzed using the expression for extractability and the Hessian matrix of the model-data discrepancy function. Root Mean Square Errors (RMSE) for various types of coals have been evaluated to represent the model-data discrepancy function It was found that the RMSE was between 2-8% of the estimated initial concentration of ex tract able organic sulfur, depending upon the type of coal. A novel method, called “RMSE Contours” has also been developed to present the sensitivity of parameters to the kinetic models. The second order model has been compared with the simpler pseudo-first order model. It has been successfully     

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.     

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.     

KINETICS OF PERCHLOROETHYLENE EXTRACTION DESULFURIZATION OF COALS

The perchloroethylene coal cleaning process selectively removes the organic sulfur from coal via a hybrid mechanism of chemical reaction and physical solvation It was found that the chemical reaction was catalyzed by the inorganic species present in the coal. In this paper, a kinetic study was experimentally carried out to determine rate constants of the reaction. It was confirmed that the extent of organosulfur extraction depended strongly on the type of coal, and also that there is a critical extraction time which is required as the minimum time for each type of coal. Isothermal batch kinetic studies were done for various types of coal. A relation was established between the type of coal and its kinetics and hence the minimumtime for extraction.     

KINETICS OF PERCHLOROETHYLENE EXTRACTION DESULFURIZATION OF COALS

ABSTRACT

The perchloroethylene coal cleaning process selectively removes the organic sulfur from coal via a hybrid mechanism of chemical reaction and physical solvation It was found that the chemical reaction was catalyzed by the inorganic species present in the coal. In this paper, a kinetic study was experimentally carried out to determine rate constants of the reaction. It was confirmed that the extent of organosulfur extraction depended strongly on the type of coal, and also that there is a critical extraction time which is required as the minimum time for each type of coal. Isothermal batch kinetic studies were done for various types of coal. A relation was established between the type of coal and its kinetics and hence the minimumtime for extraction.     

KINETIC MODELING OF PERCHLOROETHYLENE EXTRACTION DESULFURIZATION OF COALS

The kinetic modeling of the perchloroethylene reaction-extraction process has been carried out on the basis of batch extraction data. In this paper, modeling results of both second order as well as the pseudo-first order model has been presented. Multiple parameter estimates have been found which minimize the model-data discrepancies. Novel methods have been devised to illustrate multiple estimates of the kinetic parameters. Ill-posedness of the kinetic modeling problem bas been analyzed using the expression for extractability and the Hessian matrix of the model-data discrepancy function. Root Mean Square Errors (RMSE) for various types of coals have been evaluated to represent the model-data discrepancy function It was found that the RMSE was between 2-8% of the estimated initial concentration of ex tract able organic sulfur, depending upon the type of coal. A novel method, called “RMSE Contours” has also been developed to present the sensitivity of parameters to the kinetic models. The second order model has been compared with the simpler pseudo-first order model. It has been successfully     

PERCHLOROETHYLENE EXTRACTION DESULFURIZATION OF LOW SULFATE COALS

The perchloroethylene coal refining process utilizes perchloroethylene (PCE) as its solvent in all phases of the precombustion desulfurization process, including wet grinding, organic sulfur removal, gravitational separation of pyrites and mineral matter, and recovery of elemental sulfur (S₈). The Process is capable of producing compliance coal which emits less than 1.2 lb SO_X/MBTU when burnt, starting from 5 mass percent sulfur Midwestern and Eastern U.S. coals. However, the process efficiency was found to be very strongly dependent upon the degree of weathering or the level of coal oxidation. In this paper, perchloroethylene extraction data of fresh, low-sulfate coals are summarized and critically assessed. The extraction efficiency of the organic sulfur removal ranged from 5 to 30 percent for fresh coals, while that for weathered coals ranged from 30 to 60 percent. This study provides a valuable insight into the chemical reaction mechanism of perchloroethylene desulfurization process.