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     

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.     

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.     

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.     

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.     

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.     

PERCHL0R0ETHYLENE EXTRACTION DESULFURIZATION OF WEATHERED COALS

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.     

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.     

EFFECT OF PYRITIC SULFUR AND MINERAL HATTER ON ORGANIC SULFUR REMOVAL FROM COAL

The perchloroethylene coal cleaning process uses perchloroethylene as the solvent to remove both organic and inorganic forms of sulfur without any significant loss to its calorific value. The process removes these forms of sulfur in two sequential unit steps. The objective of this investigation was to determine the exact sequence of operations in the Process. Hence, organosulfur was removed before and after depyriting and demineralizing the coal. The extent of total sulfur as well as organic sulfur removal were compared in both cases. It was found that the desulfurization is more efficient when organosulfur is extracted before pyritic sulfur and not vice versa, in the sequential removal of organic and inorganic forms of sulfur. The data presented in this paper reestablishes a fact that the mineral matter content in coal is quintessential to its organosulfur extractability.     

EFFECT OF PYRITIC SULFUR AND MINERAL HATTER ON ORGANIC SULFUR REMOVAL FROM COAL

Abstract

The perchloroethylene coal cleaning process uses perchloroethylene as the solvent to remove both organic and inorganic forms of sulfur without any significant loss to its calorific value. The process removes these forms of sulfur in two sequential unit steps. The objective of this investigation was to determine the exact sequence of operations in the Process. Hence, organosulfur was removed before and after depyriting and demineralizing the coal. The extent of total sulfur as well as organic sulfur removal were compared in both cases. It was found that the desulfurization is more efficient when organosulfur is extracted before pyritic sulfur and not vice versa, in the sequential removal of organic and inorganic forms of sulfur. The data presented in this paper reestablishes a fact that the mineral matter content in coal is quintessential to its organosulfur extractability.     

PERCHLOROETHYLENE EXTRACTION DESULFURIZATION OF LOW SULFATE COALS

ABSTRACT

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.     

超临界CO2驱提高致密油藏采收率实验研究

针对玛湖地区致密油藏衰竭式开发后期采油速度快速递减的问题,提出利用超临界CO₂驱替开发致密油藏的研究思路,通过开展超临界CO₂萃取致密油实验、最小混相压力实验及长岩心驱替实验,探究了超临界CO₂驱替提高致密油采收率的作用机理、开发特征及影响因素,优选了注气速度、CO₂转注时机等重要操作参数。实验结果表明:CO₂萃取轻质组分能力随萃取次数的增加而减弱;注气速度对最终采收率影响较大,最优注气速度为0.10 cm³/min;原油与超临界CO₂最小混相压力为34.18 MPa;当前油藏压力条件为最佳CO₂转注时机。该研究成果对致密油藏高效开发具有一定指导意义。     

CHARACTERIZATION OF DESULFURESATION EXTRACTS FROM MIDWESTERN U.S. COALS

Coals from Midwestern States were extracted using two different processes, viz., a supercritical extraction process and a perchloroethylene coal refining process. The objectives of these processes are the selective removal of sulfur and nitrogen compounds from high-sulfur coals. The solvent extracts were analyzed using gas chromatography/mass spectrometry as well as wet chemical analysis. The extracted organosulfur compounds varied, depending upon the extraction process, extraction conditions, type of solvent, type of coal, and degree of weathering. The experimental results are compared among the types of coal as well as among the different processes, from viewpoints of chemical and molecular interaction.     

WASHABILITY CURVES FOR PYRITE REMOVAL IN COAL USING PERCHLOROETHYLENE AS HEAVY MEDIUM

Pyritic sulfur is removed from raw, high sulfur coal by gravitational separation using a suitable solvent, or heavy medium. This is possible due to the inherent difference in the specific gravity of clean coal and the mineral matter in it. The effectiveness of perchloroethylene (PCE) as a heavy medium was experimentally evaluated. The most important factors governing the efficiency of this process are the quantity of clean coal yield and depyriting efficiency. It was found that the pyritic sulfur removal efficiency as well as the clean coal yield depended strongly on its particle size distribution and mineral matter content. This paper presents valuable data on the effect of particle size of coal on clean coal yield as well as pyritic sulfur removal efficiency. A “master” curve is obtained to determine a workable size range which gives the most optimal yield of clean and depyrited coal.     

CHARACTERIZATION OF DESULFURESATION EXTRACTS FROM MIDWESTERN U.S. COALS

ABSTRACT

Coals from Midwestern States were extracted using two different processes, viz., a supercritical extraction process and a perchloroethylene coal refining process. The objectives of these processes are the selective removal of sulfur and nitrogen compounds from high-sulfur coals. The solvent extracts were analyzed using gas chromatography/mass spectrometry as well as wet chemical analysis. The extracted organosulfur compounds varied, depending upon the extraction process, extraction conditions, type of solvent, type of coal, and degree of weathering. The experimental results are compared among the types of coal as well as among the different processes, from viewpoints of chemical and molecular interaction.     

COBENEFICIATION OF COALS IN PERCHLOROCTHYLENE EXTRACTION DESULFURIZATION

The perchloroethylene (PCE) coal refining process has been investigated for its process feasibility, operational reproducibility, organic sulfur selectivity, process efficiency, minimization of residual chlorine by steam stripping and process optimization. It was found that some coals result in a better organosulfur extraction than others. It was also confirmed that the PCE extraction process was a hybrid system of chemical reaction and physical solvation. It was further established that the coals giving a higher organosulfur extraction contain some naturally available ingredients, which promote the extraction process. Coals giving a much lower organosulfur extraction lack these species. This paper focuses on demonstration of the process feasibility of cobeneficiating both types of coals, together. In this novel process, both types of coal are blended together in fixed proportions and subjected to the PCE process. This process of cobeneficiating coals is industrially significant because of its cost effectiveness. It not only removes the organosulfur from one type of coal, but also significantly improves the organosulfur extraction from the other.     

COBENEFICIATION OF COALS IN PERCHLOROCTHYLENE EXTRACTION DESULFURIZATION

ABSTRACT

The perchloroethylene (PCE) coal refining process has been investigated for its process feasibility, operational reproducibility, organic sulfur selectivity, process efficiency, minimization of residual chlorine by steam stripping and process optimization. It was found that some coals result in a better organosulfur extraction than others. It was also confirmed that the PCE extraction process was a hybrid system of chemical reaction and physical solvation. It was further established that the coals giving a higher organosulfur extraction contain some naturally available ingredients, which promote the extraction process. Coals giving a much lower organosulfur extraction lack these species. This paper focuses on demonstration of the process feasibility of cobeneficiating both types of coals, together. In this novel process, both types of coal are blended together in fixed proportions and subjected to the PCE process. This process of cobeneficiating coals is industrially significant because of its cost effectiveness. It not only removes the organosulfur from one type of coal, but also significantly improves the organosulfur extraction from the other.     

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     

超临界CO2萃取法处理油基钻屑工艺实验

为了进一步优化油基钻屑无害化处理技术，提高资源可回收性，研究了一种利用超临界CO₂萃取法处理油基钻屑的工艺。在室内建立实验研究装置，对超临界CO₂萃取法处理油基钻屑工艺进行了对比研究。实验成功萃取出钻屑中的基础油，处理后的干钻屑含油率最低可达0.13%，表明该工艺在技术上可行，且萃取出的基础油固相含量低、无异味，满足二次配制钻井液的要求。此外，根据实验结果，分析了压力、温度、时间、钻屑含水率、夹带剂等因素对于萃取效果的影响，推荐了该工艺工业化应用的关键参数:萃取压力为10 MPa，萃取温度为35 ℃，萃取时间为1 h，萃取系统CO₂最低循环压力为4.5～5.7 MPa，冷却制冷温度为1～5 ℃，不使用夹带剂，为该工艺在现场的应用推广提供了技术支持。