Title of Invention

A PROCESS FOR PRODUCING VALUE ADDED ASH FROM FLY ASH WITH HIGH UNBURNT CARBON AND A SYSTEM

Abstract

A fly ash processing system comprising: (a) a storage silo or facility (9) for storing high carbon fly ash, having various levels of loss on ignition, (b) connected to a screw feeder(10) on a level slightly above the fluidization zone in a fluidized bed combustor (1), (c) the fluidized bed combustor having a conventional fluidized bed of me solid fuel provided with nozzles (2) for impinging preheated air, characterized in, (d) there being a preheat start up burner (11) for preheating air received from a forced draft an (3), for preheating air stream and supplying it at pressure below the nozzles, (e) mere being provided a closed loop recycle system (4) within me fluidized bed combustor for receiving the product flue gas and separating high carbon solids and recycling same to the fluidized bed combustor while allowing flue gases with tow carbon solids to leave from the recycle system (4), (f) die recycle system being in conjunction with a heat exchanger (5) for exchanging heat with cold water (8) and to produce steam thereby cooling the flue gases, (g) the heat exchanger (5) being also connected to a dust collector (6) upstream for recovering for recovering cooled, value added product ash dust collector having a product collection system (12), and an an induced fan (7) for withdrawing clean gas from the dust collector and to pass it to the exhaust (13).

Full Text

THE PATENT ACT, 1970 COMPLETE SPECIFICATION (SECTION-10) TITLE "A PROCESS FOR PRODUCING VALUE ADDED ASH FROM FLY ASH WITH HIGH UNBURNT CARBON AND A SYSTEM Tl ICRLTOR." APPLICANT THERMAX LIMITED, HAVING REGISTERED OFFICE AT D-13, MIDC INDUSTRIAL AREA, CHINCHWAD, PUNE-411 019, MAHARASHTRA, INDIA, AN INDIAN COMPANY The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed. 2 JUL 2004 FtLEO OF THE INVENTION This invention relates to "A PROCESS FOR PRODUCING VALUE ADDED ASH FROM FLY ASH \ WITH HIGH UNBURNT CARBON AND A SYSTEM PRIOR-ART It is already known in the prior art fly ash being used for blending with cement but with a limited proportion depending upon LOI (loss on ignition) levels. Presently this is restricted in case the unburnt carbon level (LOI) in the fly ash is more than 5%. DRAWBACKS OF THE PRIOR ART: 1. Limited blending proportions of captive fly ash. 2. Increased handling / transportation costs for fly ash from thermal power plants. 3. Non-acceptable blackish colour fly ash blended cement 4. Limitations for applications other than cement. OBJECTS OF THE INVENTION: It is therefore, a primary object of this invention to propose improved method for effectively reducing the unburnt carbon (LOI) in the fly ash. It is another object of this invention to propose an improved process for recovering additional energy along with generating value added product such as ash with a very low loss on ignition from fly ash. It is further object of this invention to propose such an improved process for obtaining producing ash from fly ash which will be suited for use for cement manufacturing /asbestos manufacturing / silica extraction for use in voltaic (PV cells) / installation linings / filtration and many other applications. Jt is further object of this invention to propose such an improved process by which not onJy the processed fly ash is produced with reduced unburnt levels but also with number of other favourable parameters like fineness / specific surface area/ comprehensive strength/ lime reactivity / chemical composition etc. so as to make it absolutely suitable for cement blending / PPC manufacturing. 2_ It is thus an object of this invention to obtain value added product ash from Fly ash suited for multifarious applications. It is also another object of this invention to propose an improved system for handling Fly Ash to obtain a value added ash with low loss on ignition. It is yet another object of this invention to propose such a system, which can be easily handled, supervised and operated and in which good quality steam can be generated for further use. These and other objects of this invention will be apparent from the following paragraphs. BRIEF STATEMENT OF THE PROCESS OF THE INVENTION. According to this invention there is provided a process for producing value added product ash from Fly Ash with high unburnt Carbon using the system herein described. (a) supplying Fly Ash of different levels of loss of ignition to combustion in a fluidized bed combustor in the presence of air, (b) thereafter passing the products of combustion as flue gas through closed loop recycle system so as to separate the solids having high carbon from the solids having low carbon due to density differences, recycling the so separated solids having high carbon into the combustor, (c) passing flue gas containing low carbon solids through a heat exchange state where heat is recovered from the flue gases to produce steam, (d) followed by passing the flue gas leaving the heat exchange stage through a dust collection system so as to collect processed value added ash having low loss on ignition. (e) and venting clean flue gas devoid of Fly Ash into a stack. There is also proposed improved process for producing value added product ash from Fly Ash with high unburnt carbon which comprises, supplying Fly Ash of different levels of loss of ignition to combustion as flue gas through closed loop recycle system so as to separate the solids having high carbon from the solids having low carbon due to density differences, recycling the so separated solids having high carbon into the combustor, 3 passing flue gas containing low carbon solids through a heat exchange state where heat is recovered from the flue gases to produce steam, Followed by passing the flue gas leaving the heat exchange stage through a dust collection system so as to collect processed value added ash having low loss on ignition and venting clean flue gas devoid of fly ash into a stack. In this process the fly ash used can have different levels of loss on ignition viz. 6% to 30%. The air supplied to the fluidization stage for fluidizing Fly Ash is preheated air upto 300 ° C 4 The preheated air is introduced at a pressure of upto 800 mm wc from lower level of fluidizing system. In a preferred embodiment the fluidization combustor includes a inbed heat exchange facility in the form of heat exchanger. The inbed heat exchanger facility extracts heat from the bed and the extracted heat is recovered in the heat exchange stage for producing steam from water. The products of combustion from the fluidization stage are recycled to the top of the fluidization stage by means of a closed loop recycle system so as to recover solids having high carbon solid portion and the product gases leaving the recycle system stage having very low carbon solids in the fly ash. The hot flue gases from the recycle stage exchange heat with water in the heat exchange stage to produce steam and a stream of cool flue gases having value added ash. The value added ash produced in this process is recovered in a dust collection stage so as to recover substantially all the value added ash and to produce clean flue gases suitable for venting to the atmosphere. We have studied various aspects of the process of the invention and have been able to obtain several advantages of which the important advantages are mentioned below: ADVANTAGES OF THE NEW INVENTION : 1. Higher efficiency - thus maximum energy recovery 2. Reduced fuel cost for steam / power generation 3. Eliminates ash disposal cost 4. Eliminates ash procurement cost 5. Reduces cement manufacturing costs 6. Increased blending up to 35% in cement 5 BRIEF STATEMENT OF THE INVENTION. According to mis invention, there is provided, a fly ash processing system comprising: (a) storage silo or facility for storing high carbon fly ash, having various levels of loss on ignition, connected to a screw feeder on a level slightly above the fluidization zone inafhridized bedcombustor, me fhndized bed combustor having a conventional fhndized bed of the solid fuel provided with nozzles for impinging preheated air, characterized in, (4) there beingra~preheat start up burner for preheating air received from a forced draft fan, for preheating air stream and supplying it at pressure below the nozzles, mere being provided a closed loop recycle system within the fhndized bed combustor for receiving the product flue gas and separating high carbon solids and recycling same to the fluidized bed combustor while allowing flue gases with low carbon solids to leave from the recycle system, therecycle system being in conjunction with a heat exchanger for exchanging heat with cold water and to produce steam thereby cooling me fluegases, the heat exchanger being also connected to a dust collector upstream for recovering for recovering cooled, value added product ash dust collector having a product collection system, and an an induced fan for withdrawing clean gas from the dust collector and to pass it to the exhaust. Hie fluidized bed is preferably provided with an in bed heat exchanger for additional heat recovery from within the bed, which in bed heat exchanger, is connected in closed circuit with the above mentioned heat exchanger. The invention will now be described with reference to the accompanying drawing, Where figure 1 shows the schematic of the proposed system. (1) is the normal known conventional fluidized bed combustor with or without in bed heat exchanger IBH (2) extracting heat from the bed and capable of combusting wide range of fly ashes with different levels of loss onignition.(LOI) Fly ash is stored in a high carbon fly ash silo (9), and fed to the combustor by any known means, a screw feeder (10), and the air is supplied with the assistance of blower (3) and pre heated by start burner (11).. The product of combustion (flue gas) is men passed through recycle system (4) and the separated solids having high carbon are then discharged back into the combustor. The flu gas containing low carbon solids men exchanges heat m a heat exchanger (5), ecover the energy in the form of steam/The water is pumped using pump (8) into the heat exchanger (5), The cooled flue gas is men passed through dust collection equipment (6) in order to collect product fry ash (12) having low loss on ignition (LOI). Finally the clean flu gas is vented to stack (13) through ID fan (7). WE CLAM, (1) A fly ash processing system comprising: (a) a storage silo or facility (9) for storing high carbon fly ash, having various levels of loss on ignition, (b) connected to a screw feeder(10) on a level slightly above the fluidization zone in a fluidized bed combustor (1), (c) the fluidized bed combustor having a conventional fluidized bed of me solid fuel provided with nozzles (2) for impinging preheated air, characterized in, (d) there being a preheat start up burner (11) for preheating air received from a forced draft an (3), for preheating air stream and supplying it at pressure below the nozzles, (e) mere being provided a closed loop recycle system (4) within me fluidized bed combustor for receiving the product flue gas and separating high carbon solids and recycling same to the fluidized bed combustor while allowing flue gases with tow carbon solids to leave from the recycle system (4), (f) die recycle system being in conjunction with a heat exchanger (5) for exchanging heat with cold water (8) and to produce steam thereby cooling the flue gases, (g) the heat exchanger (5) being also connected to a dust collector (6) upstream for recovering for recovering cooled, value added product ash dust collector having a product collection system (12), and an (h) an induced fan (7) for withdrawing clean gas from the dust collector and to pass it to the exhaust (13). (2) A fly ash processing system as claimed in claim 1, wherein the fluidized bed is preferably provided with an in bed heat exchanger for additional heat recovery from within the bed which in bed heat exchanger is connected in closed circuit with the above mentioned heat exchanger (5). (3) A process for producing value added product ash from fly ash with high unburnt carbon using a system as claimed in claim 1, which comprises: (a) supplying fly ash of different levels of loss of ignition to combustion in a fluidized bed combustor in the presence of air. - 7- (b) thereafter passing the products of combustion as flue gas through closed loop recycle system so as to separate the solids having high carbon from the solids having low carbon due to density differences, recycling the so separated solids having high carbon into the combustor, (c) passing flue gas containing low carbon solids through a heat exchange state where heat is recovered from the flue gases to produce steam, (d) followed by passing the flue gas leaving the heat exchange stage through a dust collection system so as to collect processed value added ash having low loss on ignition and (e) venting clean flue gas devoid of Fly Ash into a stack. (4) A process as claimed in Claim 3, wherein, the fly ash used has different levels of loss on ignition viz. 6% to 30%. (5) A process as claimed in claims 3 and 4, wherein the air supplied to the fluidization stage for fluidizing Fly Ash is preheated air upto 300 °C. (6) A process as claimed in claims 3 to 5 wherein the preheated air is introduced at a pressure of upto 800 mm Hg from lower level of fluidizing system. In a preferred embodiment the fluidization combustor includes a inbed heat exchange facility in the form of heat exchanger. (7) A process as claimed in claims 3 to 6 wherein the inbed heat exchanger facility extracts heat from the bed and the extracted heat is recovered kin the heat exchange stage for producing steam from water. (8) A process as claimed in claims 3 to 7 wherein the products of combustion from the fluidization stage are recycled to the top of the fluidization stage by means of a closed loop recycle system so as to recover solids having high carbon solid portion and the product gases leaving the recycle system stage having very low carbon solids in the fly ash. (9) A process as claimed in claims 3 to 8 wherein the hot flue gases from the recycle stage exchange heat with water in the heat exchange stage to produce steam and a stream of cool flue gases having value added ash. 8 (10) A process as claimed in claims 3 to 9 wherein the value added ash produced in this process is recovered in a dust collection stage so as to recover substantially all the value added ash and to produce clean flue gases suitable for venting to the atmosphere. (11) A Fly Ash processing system substantially as herein described with reference to the accompanying drawings. (12) A process for producing value added product ash from Fly Ash with high unburnt carbon substantially as herein described. DATED THIS 1st DAY OF JANUARY 2004 (K. RAJAGOPALAN)) Agent for the applicant

Documents:

2-mum-2003-cancelled pages(12-7-2004).pdf

2-mum-2003-claims(granted)-(12-7-2004).doc

2-mum-2003-claims(granted)-(12-7-2004).pdf

2-mum-2003-correspondence(13-5-2005).pdf

2-mum-2003-correspondence(ipo)-(28-6-2004).pdf

2-mum-2003-drawing(12-7-2004).pdf

2-mum-2003-form 1(2-1-2003).pdf

2-mum-2003-form 19(12-3-2004).pdf

2-mum-2003-form 2(granted)-(12-7-2004).doc

2-mum-2003-form 2(granted)-(12-7-2004).pdf

2-mum-2003-form 26(2-1-2003).pdf

2-mum-2003-form 3(2-1-2003).pdf

2-mum-2003-form 5(2-2-2005).pdf

2-mum-2003-power of attorney(3-4-2003).pdf

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