Title of Invention

AN IMPROVED PROCESS TO PRODUCE LOW ASH COAL FROM HIGH ASH COAL AND SYSTEM THEREOF

Abstract

The present invention relates to an improved process to produce low ash coal from high ash coal, comprising the steps of forming a slurry of coal fines in a N-Methyl-2-pyrrolidone (NMP) including Ethylenediamine (EDA), NMP and EDA being between 6:1 to 24:1 solution, said slurry containing about 6 to 25 ml of solution per g of coal; maintaining said slurry in refluxed condition at a temperature of about 170 °C for a period of about 15 minutes to 2 hours; separating the refluxed solution in two parts by coarse filtration at 0.025 mm filter cloth a cut size of the separation being variable depending on the particle size filtrate, extract and residue to be treated; cooling the filtered coal-solvent mixture; precipitating the coal by adding acetone in the extract; separating the coal by filtration, said coal having a reduced ash content; and recovering the rest of the solvent by distillation of the acetone-solvent solution.

Full Text

FIELD OF THE INVENTION The present invention relates to an improved process to produce low ash clean coal from high ash coal. The invention further relates to a system for producing low ash clean coal from high ash coal including high recovery of solvents BACKGROUND OF THE INVENTION Concept and implementation of chemical beneficiation comes from the limitation of physical beneficiation processes. Broadly, a chemical beneficiation is possible by chemical leaching of mineral matter present in coal or, dissolving organic matter of coal in various organic solvents. As coal is a heterogeneous mixture of organic and inorganic constituents, the degree of solvolysis of coal varies with its constituents, maturity, and structural characteristics. Main advantages of the chemical beneficiation process are i) ease of recovery of solvent in the main process stream, ii) solvolytic efficiency of recovered solvents as that of fresh solvent, iii) 98-% recovery of the solvent, iv) improved coking properties of clean coal, and v) availability of industrial organic solvents. However, the operating cost of this process is high because of high cost of solvents and energy requirement in the process. There is an attempt to make this process techno- economic through improving the yield to 70-80%. However, further research may be required to make the process economically viable through reducing the cost of solvent recovery. Recovery of clean coal and its ash content depend on various operating parameters of the process and feed characteristics like faster and convenient filtration of refluxed solution at different size, solvent and co-solvent of choice, coal source (feed characteristics), particles size, coal-solvent ratio, extraction time, extraction temperature, etc. Thus, the process offers a balance between the yield and the ash contents desired in the clean coal. Since the mineral matter (non-combustible) in Indian coals (Gondwana coals) is very finely disseminated in the organic mass, it is quite difficult to remove the mineral matter by conventional physical coal washing techniques. High percentage of near gravity material in this coal, makes the scope of gravity process substantially limited. This indicate that chemical treatment may be the right approach to overcome the limitation of physical beneficiation methods. A lot of literature is available on chemical beneficiation techniques (US patent 5955375, 21/09/1999) that employ high corrosive chemicals (mostly acids and alkalis). Recovery or regeneration of these chemicals is very important to make this technology viable. A parallel approach towards lowering ash, is the process of recovering the premium organic matter from coal by solvent refining. Literature (India 1088/KOL/2007) reveals that most of the research work on this subject was carried out with an objective to produce ultra clean coal or super clean coal with ash content less than 0.2% for various high tech end uses. This known solvent refining process does not serve the objective of low ash coal requirement of steel industries because of mainly low recovery which makes the process uneconomic especially when such an ultra coal is not absolutely desired at the cost of restricting to low yields. Patent literatures described solvent extraction (India 1292/KOL/2006, India 1336/KOL/2008 techniques that employ expensive solvents. According to the existing process, coal, solvent and co-solvents are mixed thoroughly to produce coal slurry. The coal slurry is extracted in a known manner which includes coal- solvent mixture. The mixture is separated in a separation unit to produce a coarser fraction and a finer fraction. The finer fraction is fed to an evaporator unit to allow 70 to 80% of solvent recovery. The hot concentrated coal-solvent mixture is then flushed in a precipitation tank to precipitate the coal. Water as an anti-solvent is being used. Coal is precipitated and water-solvent mixture as obtained separated in a distillation column. Recovery or regeneration of these solvents and anti solvent are very important to make this technology viable. Conventionally solvent is recovered by hot precipitation of coal extracts in anti solvent, but there is no prior art available on cold precipitation. Therefore there is a need to propose a noble process to recover the solvent and anti solvent which is convenient and adapts cold precipitation. OF THE INVENTION It is therefore an object of the invention to propose an improved process to produce low ash clean coal from high ash coal. Another object of the invention is to produce an improved process to produce low ash clean coal from high ash coal, which adapts an economic and environment-friendly Anti-solvent suitable for industrial extraction of coal. A still another object of the invention is to propose an improved process to produce low ash clean coal from high ash coal, which is economic and environment-friendly. A further object of the invention is to propose an improved process to produce low ash clean coal from high ash coal, which provides better separation and ensures high recovery of solvents. A still further object of the invention is to propose an improved process to produce low ash clean coal from high ash coal, which provides better separation of extracted coal and solvent mixture. Yet another object of the invention is to propose a system for producing low ash clean coal from high ash coal including high recovery of solvents. SUMMARY OF INVENTION Accordingly, in a first aspect of the invention, there is provided An improved process to produce low ash coal from high ash coal, comprising the steps of forming a slurry of coal fines in a N-Methyl-2-pyrrolidone (NMP) including Ethylenediamine (EDA), NMP and EDA being between 6:1 to 24:1 solution, said slurry containing about 6 to 25 ml of solution per g of coal; maintaining said slurry in refluxed condition at a temperature of about 170 °C for a period of about 15 minutes to 2 hours; separating the refluxed solution in two parts by coarse filtration at 0.025 mm filter cloth a cut size of the separation being variable depending on the particle size filtrate, extract and residue to be treated; cooling the filtered coal-solvent mixture; precipitating the coal by adding acetone in the extract;; separating the coal by filtration, said coal having a reduced ash content; and recovering the rest of the solvent by distillation of the acetone-solvent solution. According to the invention, coal solvent and co-solvent are mixed thoroughly to produce a coal slurry. The coal slurry is extracted in a known manner which includes coal-solvent mixture. The mixture is separated in a separation unit to produce a coarser fraction and a finer fraction. The finer fraction is cooled in a jacketed vessel and not being fed to evaporation unit, thus this energy can be used for heating purpose in the process. The cooled extracted clean coal-solvent mixture is then flushed in a precipitation tank to precipitate the coal, where, Acetone as an anti-solvent is being used. Acetone separates the solvent from coal very effectively, and we get acetone-solvent mixture, which is easily separable at lower temperature in distillation unit, thus energy is being saved in distillation column too. And precipitated coal is separated in a rotary drum filter. The process is an economic and environment-friendly coal extraction process which is less energy intensive and economically viable. The invention process is enabled to produce low ash clean coal which provides better separation of extracted coal and solvent mixture. According to a second aspect of the invention, there is provided A system for producing low ash coal from high ash coal, comprising an extractor (1) enabled to received a coal-slurry produced by thoroughly mixing coal, solvent, and anti- solvent in a coal-solvent feed plant, temperature in the extractor (1) being gradually generated to about 200 °C, the residue time of the coal-solvent feed depending on the process parameters varies between 15 - minutes to 2-hours a first filter (2) for separating the extracted coal - solvent mixture into a coarser fraction called as a residue containing high ash , and a finer fraction known as the filtered extract; a cooler unit (3) for directly receiving the finer fraction; a precipitation tank (4) for receiving the cooled coal-solvent mixture in which the acetone acting as an anti-solvent gets the extracted coal separated from the coal-slurry solution for further precipitation; a second filter (5) for separating the precipitated coal to produce a clean coal; and a distillation unit (6) for receiving the filtrate containing solvent and anti-solvent solution to recover the solvent and the anti-solvent. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING Figure - 1 - shows a system for producing low ash clean coal from high ash coal according to the invention. DETAILED DESCRIPTION OF THE INVENTION As shown in figure - 1, the inventive system comprises an Extractor (1); a first filter (2) enabled to separate solid-liquid upto size 500 mesh a cooler (3); a Precipitation tank (4); a second filter (5) enabled to completely separate solid- liquid; and a Distillation column (6). According to the invention, acetone has been identified as the anti-solvent for convenient, environmental friendly and economical industrial coal-solvent separation operation. The coal sample is refluxed with NMP and a small amount of co-solvent (EDA) for 1 h at atmospheric pressure. Then the refluxed mixture using 500 stainless steel BSS mesh (0.25 mm) cloth is filtered. This arrangement allowed a coarser and faster filtration at 0.25 mm size in comparison to that observed by using the known Whatman filter paper. Therefore, increase in yield of clean and simultaneously increase in ash content of clean coal, have been clearly established. Thus, the identified anti-solvent is found to be advantageous to produce high yield clean coal with low ash content (5-8%) through a faster filtration process. According to the invention, an improved process to produce low ash clean coal from high ash cola in the inventive system comprises a step of thoroughly mixing coal, solvent and co-solvent in a coal - solvent feed tank (not shown). The coal slurry is then pumped from the tank into the extractor (1). A temperature around 170 - 200 °C is gradually generated in the extractor (1). Residence time in the extractor (1) may vary form 15 mins to 2 h and i.e. dictated by the techno economics of the process and its specific requirement. The extracted coal-solvent mixture is then separated through the first filter (2) which cut the mixture in two fractions for example, a coarser fraction (+0.25 mm), and a finer fraction (-0.025 mm). The coarser fraction contains high ash and is called as residue. The finer fraction or filtered extract is then fed to the cooler unit (3) directly, bypassing the evaporator unit (3). The cooled coal-solvent mixture is flushed in thee precipitation tank (4), where the acetone acts as an anti-solvent. As the solvents are strongly soluble in Acetone, the extracted coal gets separated from the solution phase and gets precipitated. This precipitated coal is separated through the second filter (5). Thus, a clean coal is obtained which contains less than 4% ash. The filtrated coal slurry consists of solvent-anti solvent (Acetone) solution which is sent to a distillation unit (6) where the solvent and the anti-solvent are recovered after distillation. EXAMPLE A sample of 10 gm coal, having - 30 mesh sizes and 27% ash content, is extracted, using NMP and EDA as a solvent and co-solvent respectively for one hour. Filtration is done through a 500 stainless steel BSS mesh (0.025 mm). Precipitation is thereafter separately done in water and acetone. An analysis is done for clean coal and residue both the clean obtained through extraction and filtration. As interesting phenomenon is observed when the acetone is used as the anti- solvent. For example, if the hot filtered coal-solvent mixture is poured in the precipitation tank, then the coal is not agglomerated, and further the separation of coal-solvent is poor. In contrast, if a filtered coal-solvent is properly mixed acetone. Comparative study of precipitation in water and precipitation in acetone is shown in table 1. Table 1 shows that precipitation in water gives less yield, i.e. 35% while precipitation in acetone gives higher yield, i.e., 43.45% of clean coal. Ash content of such an experimentation establishes that acetone is better anti- solvent than water, in terms of yield and in terms of saving of energy mainly because of low boiling point of the acetone, WE CLAIM 1. An improved process to produce low ash coal from high ash coal, comprising the steps of: (i) forming a slurry of coal fines in a N-Methyl-2-pyrrolidone (NMP) including Ethylenediamine (EDA), NMP and EDA being between 6:1 to 24:1 solution, said slurry containing about 6 to 25 ml of solution per g of coal; (ii) maintaining said slurry in refluxed condition at a temperature of about 170 °C for a period of about 15 minutes to 2 hours; (iii) separating the refluxed solution in two parts by coarse filtration at 0.025 mm filter cloth a cut size of the separation being variable depending on the particle size filtrate, extract and residue to be treated; (iv) cooling the filtered coal-solvent mixture; (v) precipitating the coal by adding acetone in the extract;; (vi) separating the coal by filtration, said coal having a reduced ash content; and (vii) recovering the rest of the solvent by distillation of the acetone-solvent solution. 2. The process as claimed in claim 1 wherein said coal comprises run of mine coal. 3. The process as claimed in claim 2 wherein said particles size is preferably between - 2mm and - 0.5 mm, more preferably between 0-25 mm. 4. The process as claimed in claim 1 wherein a moderate ash clean having ash content 5. The process as claimed in claim 4 wherein said moderate ash clean coal having ash content furnace injection in iron and steel industries and power generation. 6. The process as claimed in claim 1 wherein acetone is used as the anti- solvent which is an economic and environment-friendly anti-solvent suitable for industrial extraction of coal. 7. A system for producing low ash coal from high ash coal, comprising: - an extractor (1) enabled to received a coal-slurry produced by thoroughly mixing coal, solvent, and anti-solvent in a coal-solvent feed plant, temperature in the extractor (1) being gradually generated to about 200 °C, the residue time of the coal-solvent feed depending on the process parameters varies between 15 - minutes to 2-hours; - a first filter (2) for separating the extracted coal - solvent mixture into a coarser fraction called as a residue containing high ash , and a finer fraction known as the filtered extract; - a cooler unit (3) for directly receiving the finer fraction; - a precipitation tank (4) for receiving the cooled coal-solvent mixture in which the acetone acts as an anti-solvent to get the extracted coal separated from the coal-slurry solution for further precipitation; - a second filter (5) for separating the precipitated coal to produce a clean coal; and - a distillation unit (6) for receiving the filtrate containing solvent and anti- solvent solution to recover the solvent and the anti-solvent. 8. An improved process to produce low ash coal from high ash coal as substantially described and illustrated herein with reference to the accompanying drawings. 9. A system for producing low ash coal from high ash coal as substantially described and illustrated herein with reference to the accompanying drawings. The present invention relates to an improved process to produce low ash coal from high ash coal, comprising the steps of forming a slurry of coal fines in a N-Methyl-2-pyrrolidone (NMP) including Ethylenediamine (EDA), NMP and EDA being between 6:1 to 24:1 solution, said slurry containing about 6 to 25 ml of solution per g of coal; maintaining said slurry in refluxed condition at a temperature of about 170 °C for a period of about 15 minutes to 2 hours; separating the refluxed solution in two parts by coarse filtration at 0.025 mm filter cloth a cut size of the separation being variable depending on the particle size filtrate, extract and residue to be treated; cooling the filtered coal-solvent mixture; precipitating the coal by adding acetone in the extract; separating the coal by filtration, said coal having a reduced ash content; and recovering the rest of the solvent by distillation of the acetone-solvent solution.

Documents:

950-KOL-2009-(23-01-2013)-ABSTRACT.pdf

950-KOL-2009-(23-01-2013)-CLAIMS.pdf

950-KOL-2009-(23-01-2013)-CORRESPONDENCE.pdf

950-KOL-2009-(23-01-2013)-FORM-1.pdf

950-KOL-2009-(23-01-2013)-FORM-2.pdf

950-kol-2009-abstract.pdf

950-kol-2009-claims.pdf

950-KOL-2009-CORRESPONDENCE 1.1.pdf

950-kol-2009-correspondence.pdf

950-kol-2009-description (complete).pdf

950-kol-2009-drawings.pdf

950-KOL-2009-FORM 1 1.1.pdf

950-kol-2009-form 1.pdf

950-kol-2009-form 18.pdf

950-kol-2009-form 2.pdf

950-kol-2009-form 3.pdf

950-kol-2009-form 5.pdf

950-kol-2009-specification.pdf

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