The invention is related to refining of coal of by organic solvents in general, and to a process of separation of coal from organic solvent completely for recovering the said solvent, which is used for extraction.
The current process operation involves separation of coal from the organic solvents. Organic-refining or, solvent-refining or, solvent extraction of coal is a well-established technology. Abundant literature is available on the subject. However, the primary objective in most of those cases is to provide a process to produce ultra clean coal or super clean coal with ash contains less that 4%. The ash content of this parent coal (Run of Mine) is 25%. Exploratory study revealed that it is possible to extract 50% of parent coal through this process of extraction of coal under reflux conditions at atmospheric pressure. The coal contains almost 4% ash.
The yield and the ash content of super clean coal are satisfactory and it encourages for up scaling the process to bench scale set up the main concerning factor apart from yield is the economic viability of the process. The process consumes significant amount of heat for extraction. Again recovery of the of the solvent has been achieved by the consumption of large amount of heat. Combination of the above two heat inputs drives the process towards infeasibility. Now if the two heat consumptions are arranged in priority basis then heat consumption for extraction has come forth as the extraction process is solely depends upon the extraction temperature this is why it is often called as thermal extraction. So only the heat requirement for solvent recover has left for minimization. Effective or optimize design of solvent recovery such a way it minimize the heat requirement for solvent recovery and thus established the process economy.
To overcome the drawbacks of the prior art, the following innovative remedial measures were undertaken:—
Primary object of invention is to propose a method of recover of organic solvents required (for the extraction) in refining of coal.
Another object of invention is to propose an innovative approach to separate coal from organic solvent as completely as possible with minimizing energy required.
Still another object of the invention is to introduce a techno economic chemical coal benefication process without using any evaporation unit for producing clean coal and to increase recovery of solvents.
According to the innovative design, coal is separated from “coal extract” by ultra filtration. The “coal extract” is formed by the thermal treatment of coal with organic solvent. The hot coal “coal extract” is then cooled and passed through the membrane having diameter 0.2 micron or may be less than that. The filtrate coming from membrane is free from coal which is proved by the addition of water. If the permeate contains coal then addition of water, coal happens to be precipitated which does not happen at all. This observation strongly claims the inexistence of coal in permeates. It proves that the “coal extract” can be well separated by membrane operation and it produces pure solvent as permeate from membrane and the thick clarified solution from top of the membrane, which is then sent to the other unit for usual operation. The new process has been developed which is very flexible to produce clean coal of desired ash level (0.1 to 10%) with satisfactory yield.
The invention will now be described with help of the accompanying drawing which depict on exemplary embodiments of the invention. However, there can be several other embodiments, all of which are deemed covered by this description.
I) Feed Preparation Zone 1.
II) Extraction Zone 2
III) Solvent Recovery Zone 3
The amount of water needed in precipitation tank is very less as 80% of solvent is already removed. This slurry (water+solvent+coal) becomes filtered by another rotary drum filter and the super clean coal is then sent to product washing unit. The filtrate contains water and organic mixture which is fed to the distillation unit and water and 19% organic solvent is being separated. So this methodology gives us almost 99% solvent recovery with negligible energy consumption, thus established the process economy.
IV) Final Product and Residue Washing Zone 4
So in this way the whole process operation as claimed 99% solvent recovery with minimum the energy requirement, is accomplished with 50% super clean coal having ash percentage less than 4%.
As the optical density of pure NMP is zero and the coal extract having 4, it proves that “coal extract” must contain very fine particles which can be separated by applying membrane.
The following results are the strong evidence of coal suspension in organic solvent. Actually the coal extract is very fine coal particle distribution in liquid organic phase. The particle size distribution has started approximately from 25 micron to nano size or may be less than that. The major portion of coal particle can be separated by passing through membrane. The coal extract has been passed through ceramic membrane having pore diameter of 0.2 micron. The permeate coming from the membrane is totally free of coal and this has been proved, as there is no further precipitation observed by adding sufficient amount of water. If coal is there in permeate then after adding water coal will be separated out as it was happened in our earlier process.
The important safety measures comprises:
The main advantages of the invention achieved
Number | Date | Country | Kind |
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1981/KOL/08 | Nov 2008 | IN | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IN2009/000381 | 7/6/2009 | WO | 00 | 4/13/2010 |