EFFECT OF SOLVENT-TO-COAL RATIO ON ORGANOSULFUR EXTRACTABIL1TY IN THE PERCHLOROETHYLENE ORGANODESULFURIZATION PROCESS

ABSTRACT

A novel reaction-extraction model for removal of organosulfur compounds from coal by the Perchloroethylene Organodesulfunzation Process has been proposed. The model treats the coal as a reactant to observe the effect of slurry composition on the rate of “lock-up” reaction where the liberated organosulfur species from coal re-enters the coal organic matrix. A series of batch organodesulfunzation extractions were conducted to observe the effect of solvent-to-coal ratio on the extent of organosulfur removal. Based on this data, kinetic parameters for the organosulfur “liberation” and “lock-up” reactions were simulated using the model. The ratio of first-order rate constant of “lock-up” reaction to that of the “liberation” reaction was found to be 4.03. Optimal design parameters and operating conditions have been obtained for a wide range of PCE-to-coal ratio for Indiana 5 coal. Mathematical models representing the optimal slurry composition as a function of the ratio of rate constants, extraction capacity, and the corresponding extraction performance have been developed. This study is very significant from the point of view of reaction and process engineering, which in turn assist in achieving an optimal and economical equipment design.     

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.     

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.     

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     

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.     

CHARACTERIZATION OP MEDIUM DISTILLATE CUT (100-230°C) OIL FROM HIGH-ASH “MINA DO LEÃO” BRAZILIAN COAL TAR

Brazilian coal tar oil has been characterized by combined spectroscopic and chromatographic methods. A coal tar cut (100-230°C) obtained from a Gasifier Plant operating with “Mina do Leau” high-ash coal was fractionated into ABN “acid-base-neutral”groups. Infrared spectra and elemental analysis of each fraction has demonstrated the success of the fractionation step. GC/MS analysis of the total cut before the ABN fractionation revealed only hydrocarbons present in the sample. However, after the pre-fractionation step several nitrogen containing compounds of environmental concern were positively identified by GC/MS in the tar bases fraction.     

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.     

催化裂化芳烃萃取油用作煤液化起始溶剂的研究

 选用一种催化裂化（FCC）芳烃抽提装置生产的芳烃萃取油作为煤液化开车起始溶剂的原料，在0.1t/d连续装置上进行的煤液化实验。利用色质联用仪解析其组成和结构，应用常温常压黏度仪考察了其成浆性。结果表明,芳烃萃取油具有多环芳烃含量高的特点, 3次加氢后的芳烃萃取油与煤液化加氢循环溶剂的结构组成十分接近。采用三次加氢萃取油制备的煤浆具有良好的成浆性、输送性和反应性，与煤液化加氢循环油参与煤液化的效果相当, 是理想的煤液化起始溶剂。     

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     

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.     

THERMAL STABILITY ANALYSIS OF THE LIQUID PHASE METHANOL SYNTHESIS REACTOR

The effect of addition of an inert liquid phase on the rate of heat generation in the catalytic synthesis of methanol from syngas has been studied. Gas compositions typical of product gases from Lurgi and Koppers-Totzek gasifiers, represented by H₂-rich and CO-rich syngas respectively, were used to experimentally verify the “slope” and “dynamic” critria in a three-phase fixed bed recycle reactor. The liquid medium, witco-40 oil, has been effective in controlling the rate of heat generation and in preventing catalyst overheating, signifying that the liquid phase synthesis is thermally far more stable than the vapor phase synthesis. The experimental thermal stability study provides crucial and valuable information in commercializing the liquid phase methanol synthesis process. The current approach of thermal stability analysis does not require any a priori assumption or predetermined reaction kinetics.     

ENHANCED HYDROCARBON EXTRACTION FROM CALOTROPIS PROCERA - A PETROCROP

With fast disappearing petroleum reserves renewable resources like biomass are of great significance. Petrocrop, Calotropis procera is a wild shrub and does not compete with food and fodder crops for land. This paper presents an investigation on enhancement of hydrocarbon extraction from Calotropis procera. An extraction yield of 8% has been obtained with toluene, as solvent. Increase in extraction to 11.5% has been achieved by modification of design of conventional “Soxhlet extractor”. Further enhancement in extraction has been achieved by pre-treatment of the biomass with alkali or acid. Pre-treatment results in extractive or hydrolytic breakdown of plant structure and hence exposes hyrocarbons to solvent attack. Alkali pretreatment of ground biomass resulted in much higher extraction. So it was studied in further detail with more alkalies of varying strength. An enhancement from 8% to 18% has been achieved by pre-treatment with IN sodium hydroxide.     

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.     

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.     

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.     

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.     

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     

过氧乙酸处理催化柴油脱硫过程的数学模拟

 用过氧乙酸溶液对催化柴油进行氧化和萃取处理，探索了柴油氧化萃取脱硫的变化规律。依据反应动力学和萃取相平衡原理，确定了过氧乙酸生成动力学方程、催化柴油中有机硫化物符合顺序氧化机制的反应动力学方程、硫化物液液相平衡方程，建立了催化柴油过氧乙酸氧化与萃取的脱硫模型方程。通过模型参数估值，建立了催化柴油脱硫数学模型。模型预测结果表明，柴油脱硫率随着双氧水过氧化氢质量分数提高呈现先提高后降低的变化趋势，随着双氧水与乙酸体积比的减小或柴油与氧化溶液体积比的降低呈提高的变化趋势，随着氧化处理时间的延长呈先增大后降低的变化趋势。