Title of Invention

A CONTINUOUS PROCESS FOR THE PRODUCTION OF CUSTOMIZED COAL TAR PITCH

Abstract

A method for continuous production of clean tar of consistent quality by selective horizontal decanter centrifuge and subsequently the said clean tar is used to produce customized binder pitch, impregnating pitch and zero QI (Quinoline Insoluble) pitch deploying vertical bowl separator. The present invention is also directed to separation of very fine particles of size in the range of zero to less than 5 microns, known as spheroids and cenospheres, produced during cracking reactions at coke ovens at high temperatures followed by polymerization and poly-condensation reactions, employing vertical bowl separator, removing both carbonaceous and non-carbonaceous refractory particles from the tar. The clean tar so obtained is further distilled to produce zero QI pitch and also customized binder pitch and impregnating pitch for industrial application such as the graphite electrodes for the aluminium industries and the like. The present process is capable of producing clarified tar up to 10-15 m3/hr, and that of clean tar with < 1% QI up to 3-5 m3/hr.

Full Text

FIELD OF THE INVENTION: The present invention relates to a process of preparing coal tar pitch and, in particular, a process for producing customized coal tar pitch having consistently good quality of customized binder pitch and zero Quinoline Insoluble (QI) pitch from crude coal tar. Imporatntly, the process of the invention would favour producing clean tar with the removal of sludge and moisture. Advantageously, the invention directs to separation of very fine particles of size in the range of zero to less than 5 microns, known as spheroids and cenospheres, produced during cracking reactions at coke ovens at high temperatures followed by polymerization and poly-condensation reactions, employing vertical bowl separator, removing both carbonaceous and non-carbonaceous refractory particles from the tar. The clean tar so obtained is further distilled to produce pitch of desired characteristics and also customized binder pitch and impregnating pitch for industrial application such as the graphite electrodes for the aluminium industries and like. The present process is capable of producing clarified tar up to 10-15 m3/hr, and that of clean tar with BACKGROUND ART: The quality of pitch produced from coal tar and the residue of petroleum distillation of crude oil differ widely in quality. Pitch produced from coke oven plants varies to a great extent in quality with respect to Quinoline Insoluble (QI) and Toluene Insoluble (TI). Coal tar based pitch has been found to be excellent raw material for carbon-carbon composites, carbon fibers and carbon-nano tubes. Besides, pitch produced from coal tar has been found to be an excellent input material for customized binder pitch, impregnating pitch and zero QI pitch. The customized and impregnating pitches are produced with the required level of QI. It has been observed that producing customized and impregnating pitches on a commercial scale in Integrated steel plants is not very consistent because of the wide variations in terms of the quality of tar having contaminations of carry over from coke ovens with the sizes 50 microns and above. The separation of these particulates from tar is not an easy task because of the fluctuations of the quality of the input tar and other process parameters. Zero QI pitch is a quality pitch containing 2 Moreover, the distilled solvent cannot be re-utilized in dilution of the tar as the contamination of the solvent keeps on increasing making it unworthy of use. Coal tar pitch presently being produced in India does not meet customers' requirement of quality due to lower level of QI in crude tar (9% and coking value (CV)>53%. Production of Zero QI pitch on a continuous basis has never been attempted because of the inherent problem relating to the quality of tar produced from coke ovens. The quality of pitch by and large depends on the quality of tar produced, because tar contains carryovers of the coke ovens known as sludge. Moreover, sludge separation from crude tar is not very effective in the conventional static decanters for sludge removal. Therefore, it is worthwhile to remove sludge and moisture of the crude tar before it is transferred to final cooler and processed for dehydrated tar for pitch production. Sludge separation after the decanter tar tank is essential for the production of customized, impregnating and zero QI pitch for a number of different applications. The processing of clean tar is exclusively required for dehydration purposes for its onward processing for pitch production. The pitch produced in India following existing process, did not comply with the customers' requirement from the point of view of quality parameters determined by selective contents of QI, TI, and the associated Coking Value (CV). There was therefore a persistent need for developing a process for producing clean tar free of any sludge or moisture from crude tar and also to separate out very fine, even less than 5 micron in size, carbonaceous and non-carbonaceous particulates, from said clean tar such as to favour onward production of customized binder pitch and zero QI pitch, for advantageous use in graphite electrodes for aluminium industries and the like. OBJECTS OF THE INVENTION: The basic object of the present invention is therefore directed to a continuous process of producing clean tar from crude tar through removal of sludge and other fine particulates, and its dehydration and distillation at selective temperature, for its onward use to produce zero QI pitch having 3 A further object of the present invention is directed to the process of production for customized binder pitch and impregnating pitch by making use of said clean tar free of sludge/contaminations due to carbonaceous and non-carbonaceous fine particulates. A further object of the present invention is directed to the process of production for customized binder pitch, impregnating pitch and zero QI pitch by making use of said clean tar, wherein said clean tar free of any sludge/carbonaceous or non-carbonaceous fine particulates of size less than 5 microns is obtained , and processed for said zero QI and customized binder pitch. A further object of the present invention is directed to the process of production for customized binder pitch, impregnating pitch and zero QI pitch by making use of said clean tar, wherein said continuous process is developed to produce clarified/clean tar up to 10-15 m3/nr and that of clean tar with SUMMARY OF THE INVENTION: The basic aspect of the present invention is directed to a continuous process for the production of customized coal tar pitch comprising: sludge separation from crude tar involving horizontal decanter centrifuge ; subjecting the clean tar thus obtained to dehydration in dehydration tanks to provide dehydrated tar; and subjecting the dehydrated tar to vertical centrifuge to thereby produce customized coal tar pitch of desired characteristics. A further aspect of the present invention directed to a continuous process for the production of customized coal tar pitch wherein the crude tar is preheated before subjecting to decanter sludge separation treatment. According to a still further aspect of the present invention directed to a continuous process for the production of customized coal tar pitch anyone of comprising selectively 4 carrying out the stage of horizontal decanter centrifuge based on the quality of the coal tar. A still further aspect of the present invention directed to a continuous process for the production of customized coal tar pitch wherein the following operative parameters are selectively monitored for generating the customized pitch: a) gravity forces on the suspended solids to determine the rpm of the centrifuge; b) the differential speed of the conveyor bowl separating the sludge; c) the flow rate of the liquid; d) degree of fill inside the decanter; and e) temperature of tar as a function of the viscosity. According to yet another important aspect of the present invention directed to a continuous process for the production of customized coal tar pitch wherein, i) the rpm of the centrifuge is varied between 2500-4000; ii) the differential speed of the conveyor bowl separating the sludge is varied between 10-30 rpm; iii) the flow rate of the liquid is in the range of 5 to 9 m3/hr; iv) the degree of fill inside the the decanter is determined based on the diameter of crescent disc placed at the outlet of the clarified tar preferably in the range of 90 to 120 mm. v) the temperature of the tar as a function of viscosity is maintained in the range of 50 to 80°C. A still further aspect of the present invention directed to said continuous process for the production of customized coal tar pitch wherein the clean tar is taken to dehydration tanks through final cooler for onward pitch processing and the dehydrated tar is distilled for the production of the pitch. A still further aspect of the present invention directed to a continuous process for the production of customized coal tar pitch wherein the said vertical centrifuge is adapted to favour production of customized, impregnating and zero Ql pitch depending upon the adjustment of factors influencing the separation of particle size 5 i) difference in specific gravity; ii) size and shape of the particles; iii) viscosity; iv) time in centrifugal field; v) clarifier bowl; vi) purifier bowl; vii) floating of bowl; viii)adjustment of the time between the closing and opening of the bowl; and ix) temperature of the clarified tar. Another important aspect of the present invention directed to said continuous process for the production of customized coal tar pitch as claimed in anyone of claims 1 to 7 comprising generation of clarified tar upto 10-15m3/nr and clean tar with The present invention and its objects and advantages are described in greater details with reference to the following accompanying figures. BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES: Figure 1: is the schematic illustration of the processing of crude tar using decanter centrifuge for separation of sludge. Figure 2: is the schematic illustration of the vertical bowl separator used for separating finer particulates from clean tar to obtain zero QI pitch/customized binder pitch. DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES: It is well known in the art of manufacturing pitch from crude tar that the quality of pitch produced from coal tar and the residue of petroleum distillation of crude oil differ widely in quality. Coal tar based pitch is found to be excellent raw material for various applications like the carbon-carbon composites, carbon fibres and carbon-nano tubes etc. 6 The pitch produced from coke oven plants varies to a great extent in quality with respect to QI and TI. An attempt has been made, according to the present invention, to prepare the input feed material i.e. clean tar for the production of quality pitch to the satisfaction of customers' requirement. Reference is first invited to accompanying Figure 1, which is the schematic illustration of the processing of crude tar using decanter centrifuge for separation of sludge. This is achieved by the use of horizontal decanter centrifuge usage of which can conveniently remove particulates /sludge of size 70 microns and above. By optimizing the process variables of the horizontal canter centrifuge, it has been possible to produce clean tar for onward use for producing desired zero QI pitch and the like. The separation of solids from liquids as in the case of tar and sludge plays a pivotal role in the process of tar handling and processing. Decanter centrifuge performs these crucial functions exceptionally well. Sludge formation and separation is facilitated by suitable rate of steam purging. The following parameters are adjusted/controlled based on the quality of tar produced from coke ovens: gravity forces on suspended solid particles, which is a function of rpm of the centrifuge which was varied between 2500-4000. - The differential speed of the conveyor belt transporting the separated sludge was maintained in the range of 10-30 rpm. - The flow rate of the liquid tar is maintained in the range of 5-9m3/hr. Degree of fill inside the decanter - degree of fill is decided by the diameter of crescent disc placed at the outlet of the clarified tar (90-120mm) - Temperature of the tar as a function of viscosity, maintained in the range of 50- 80°C, with the help of preheaters. The clean tar thus obtained and collected in a tank is transported by pump means through pipelines for the subsequent processing in vertical bowl separator as illustrated in the accompanying Figure 2. The clean tar was subjected to heating for the removal of moisture at a temperature range of over 120°C to 130°C. The hot dehydrated clean tar at about 130°C is taken to a vertical bowl/centrifuge separator for the separation of the even finer particulates of size 7 The clean tar is taken to dehydration tanks through final cooler for onward processing of pitch. Dehydrated tar is distilled for the production of pitch. Use of vertical centrifuge is beneficial for the production of customized, impregnated and zero QI pitch, depending upon the adjustments of the factors influencing the separation of finer particle sizes difference in specific gravity maintained in the range of 0.8-1.5gms /cc at 30°C. Size and shape of the particles maintained uniform and closer size fraction between 10-50 microns. - Viscosity maintained at lower range such as that of low viscosity tar material has been used. Retention time in centrifugal field maintained for 15-30 minutes. Passing the tar through clarifier bowl, (please indicate in figure, not shown in the accompanying figure 2) Clarified tar passed through the purifier bowl. (-Do-) Floating of the bowl, adjusted by the pressure of the water tank height and instant of valve opening. - Adjustment of the time between the closing and opening of bowl maintained in the range of 5-15 minutes. - Temperature of the clarified tar maintained in the range of 90-150°C. It is thus possible by way of the present invention to obtain clean/clarified tar by using horizontal decanter centrifuge to separate the solid contaminants/sludge from the crude tar and said clean tar in turn is utilized in the subsequent stage employing a vertical bowl separator/centrifuge, to remove further even smaller solid particulates, after dehydration and distillation, to lower the level of QI and TI, favoring producing customer binder pitch, impregnating pitch and the zero QI pitch, having important applications in different industries. 8 WE CLAIM: 1. A continuous process for the production of customized coal tar pitch comprising: sludge separation from crude tar involving decanter centrifuge ; subjecting the clean tar thus obtained to dehydration in dehydration tanks to provide dehydrated tar; and subjecting the dehydrated tar to vertical centrifuge to thereby produce customized coal tar pitch of desired characteristics. 2. A continuous process for the production of customized coal tar pitch as claimed in claim 1 wherein the crude tar is preheated before subjecting to decanter sludge treatment. 3. A continuous process for the production of customized coal tar pitch as claimed in anyone of claims 1 or 2 comprising selectively carrying out the stage of horizontal decanter centrifuge based on the quality of the coal tar. 4. A continuous process for the production of customized coal tar pitch as claimed in claim 3 wherein the following operative parameters are selectively monitored for generating the customized pitch: a. gravity forces on the suspended solids to determine the rpm of the centrifuge; b. the differential speed of the conveyor bowl separating the sludge; c. the flow rate of the liquid; d. degree of fill inside the decanter; and e. temperature of tar as a function of the viscosity. 5. A continuous process for the production of customized coal tar pitch as claimed in claim 4 wherein i) the rpm of the centrifuge is varied between 2500-4000; ii) the differential speed of the conveyor bowl separating the sludge is varied between 10-30 rpm; iii) the flow rate of the liquid is in the range of 5 to 9 m3/hr; iv) the degree of fill inside the the decanter is determined based on the diameter of crescent disc placed at the outlet of the clarified tar preferably in the range of 90 to 120 mm. 9 v) the temperature of the tar as a function of viscosity is maintained in the range of 50 to 80°C. 6. A continuous process for the production of customized coal tar pitch as claimed in anyone of claims 1 to 5 wherein the clean tar is taken to dehydration tanks through final cooler for onward pitch processing and the dehydrated tar is distilled for the production of the pitch. 7. A continuous process for the production of customized coal tar pitch as claimed in anyone of claims 1 to 6 wherein the said vertical centrifuge is adapted to favour production of customized, impregnating and zero QI pitch depending upon the adjustment of factors influencing the separation of particle size selectively based on : i) difference in specific gravity; ii) size and shape of the particles; iii)viscosity; iv)time in centrifugal field; v)clarifier bowl; vi)purifier bowl; vii)floating of bowl; viii)adjustment of the time between the closing and opening of the bowl; and ix)temperature of the clarified tar. 8. A continuous process for the production of customized coal tar pitch as claimed in anyone of claims 1 to 7 comprising generation of clarified tar upto 10-15m3/hr and clean tar with 9. A continuous process for the production of customized coal tar pitch substantially as hereindescribed and illustrated with reference to the accompanying figures. 10 A method for continuous production of clean tar of consistent quality by selective horizontal decanter centrifuge and subsequently the said clean tar is used to produce customized binder pitch, impregnating pitch and zero QI (Quinoline Insoluble) pitch deploying vertical bowl separator. The present invention is also directed to separation of very fine particles of size in the range of zero to less than 5 microns, known as spheroids and cenospheres, produced during cracking reactions at coke ovens at high temperatures followed by polymerization and poly-condensation reactions, employing vertical bowl separator, removing both carbonaceous and non-carbonaceous refractory particles from the tar. The clean tar so obtained is further distilled to produce zero QI pitch and also customized binder pitch and impregnating pitch for industrial application such as the graphite electrodes for the aluminium industries and the like. The present process is capable of producing clarified tar up to 10-15 m3/hr, and that of clean tar with

Documents:

00263-kol-2007 correspondence-1.1.pdf

00263-kol-2007 p.a.pdf

0263-kol-2007 abstract.pdf

0263-kol-2007 claims.pdf

0263-kol-2007 correspondence others.pdf

0263-kol-2007 description(complete).pdf

0263-kol-2007 drawings.pdf

0263-kol-2007 form-1.pdf

0263-kol-2007 form-2.pdf

0263-kol-2007 form-3.pdf

263-KOL-2007-(15-07-2013)-CLAIMS.pdf

263-KOL-2007-(15-07-2013)-CORRESPONDENCE.pdf

263-kol-2007-CORRESPONDENCE.pdf

263-kol-2007-EXAMINATION REPORT.pdf

263-kol-2007-FORM 18-1.1.pdf

263-kol-2007-form 18.pdf

263-kol-2007-GRANTED-ABSTRACT.pdf

263-kol-2007-GRANTED-CLAIMS.pdf

263-kol-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

263-kol-2007-GRANTED-DRAWINGS.pdf

263-kol-2007-GRANTED-FORM 1.pdf

263-kol-2007-GRANTED-FORM 2.pdf

263-kol-2007-GRANTED-FORM 3.pdf

263-kol-2007-GRANTED-SPECIFICATION-COMPLETE.pdf

263-kol-2007-PA.pdf

263-kol-2007-REPLY TO EXAMINATION REPORT.pdf

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