WO2009150667A2

WO2009150667A2 - Multi-port twin-compartment fly-ash hoper for disposal of fly-ash in dry state

Info

Publication number: WO2009150667A2
Application number: PCT/IN2009/000298
Authority: WO
Inventors: Datta Ashok Kumar
Original assignee: Datta Ashok Kumar
Priority date: 2008-06-13
Filing date: 2009-05-25
Publication date: 2009-12-17
Also published as: WO2009150667A4; WO2009150667A3

Abstract

This Invention relates to a "Multi-Port Twin-Compartment Hopper" (i.e. MPTC-Hopper), which coprises of Upper and Lower compartments and each compartment consists of a bin, four pyramid shaped passages, each with a port (opening) at it's apex; and two On-Off (opening/ closing) port-valves at each port for controlling out-flow of collected and/or stored fly-ash from these compartments during ash discharging and/or removal activities. Each MPTC-Hopper has temporary storage capability and is an integeral part of "ESP-hopper System", which consists of large number of MPTC-Hoppers and is duly supported by specific "Supporting Facilities". Each MPTC-Hopper would be installed below ash collecting area for a Electrostatic Precipitator (ESP) and would function as a "Fly-Ash Collecting-cum-Storage Hopper". It would be instrumental in ensuring low capital investment, low operating expenses and uninterrupted management (collection to disposal) of fly-ash in dry state as well as dispensing with "Wet-ash Disposal System".

Description

Multi-Port Twin- Compartment Fly-ash Hopper For Disposal of Fly-ash in Dry State

FIELD OF INVENTION

This invention (i.e. the innovative product) relates to "Multi-Port Twin Compartment Fly-ash Hopper (i.e. MPTC-hopper)". Each Λ/IPTC-hopper (the innovative product) functions as Fly-ash collecting-cuπvstorage hopper.

PRIOR ART

Flue-gases, generated in coal and lignite fired industries and power plants, carry large amount of Fly-ash. An "Electrostatic Precipitator (ESP)" dislodges Fly-ash from Flue-gases, which is allowed to get collected within large number of "Fly-ash Collecting Hoppers" that are installed below ash-collection area of an Electrostatic Precipitator (ESP). Thereafter, Fly-ash is evacuated from them for further storage and/ or disposal to end users.

At present, in the coal/ Ljgnite fired power plants, "E&P-hopper System" of 250 MW unit comprises 56 or 64 fly-ash hoppers , which are arranged in eight (8) rows and 7 or 8 fields. Thus, each row has 7 or 8 field-hoppers. Also, at any point of time, only one (1) of the first three (3) fields becomes a critical field. The fly-asr\ hoppers of a critical field are termed as "Critical Hoppers", because almost 80% of fly-ash gets collected within them, while remaining 20% ash gets distributed within other hoppers, which remain partially empty. Therefore, they are termed as "Non-critical Hoppers".

"Fly-ash Collecting hoppers" of the existing design in vogue, are of "Pyramid shape". Each pyramid shaped hopper has a single opening at its apex for evacuation of the collected fly-ash. The present design philosophy, regarding fly-ash collecting hoppers, leads to many limitations and operational problems during fly-ash evacuation cycles and further disposal of fly-ash in dry-state. For instance, it leads to vacuum loss, arch-formation and ash compaction problems. Although the above said problems become very serious limitations in the case of critical hoppers, yet there is no provision in the present design philosophy of fly-ash hoppers to address these limitations. Since the above said problems are caused due to design-deficiencies in Fly-ash collecting hoppers presently in vogue, the "present design philosophy" regarding "Fly-ash hoppers" needs a thorough re-look.

Therefore, in order to prevent arch-formation and ash-compaction in critical fly- ash collecting hoppers as well as to ensure availability of empty critical hoppers for collecting the dislodged fly-ash continuously, these hoppers are being normally emptied continuously. For example, a Flushing Apparatus (FA) ensures continuous evacuation df the collected fly-ash from a fly-ash collecting hopper, but it necessitates installation of a "Wet-ash Disposal system", which pumps Ash-water slurry into ash dump yards and excessively pollutes the natural resources (land, water bodies and air) with fly-ash around the coal/ lignite fired industries and power plants, besides high capital investment, high power consumption, high maintenance cost and tiigh operating cost.

Now, in view of MOEF-Notification'99, handling and disposal of Fly-ash in Dry- State has become a mandatory statutory requirement in India. Therefore, installation of Dry-ash handling systems for evacuation and disposal of fly-ash in dry state has also become a necessity in all (old and new) power plants now, besides installation of Wet-ash disposal systems. Thus, now in India, two types of ash handling systems (i.e. Wet & Dry) and wet-ash dump yards are being provided in all power plants, but even then the installation of two ash-handling systems fails to address the limitations and problems (i.e. arch-formation, ash-compaction, flow-interruptions, vacuum loss, etc.) associated with Fly-ash collecting hoppers of the present design in vogue.

3. The Limitations of the present state of art

The major limitations and problems of the present state of the art technology are as under: i) In order to prevent arch-formation and/ or ash-compaction, the critical Fly-ash collecting hoppers are required to be emptied continuously or intermittently withdut long pauses. ii) Fly-ash collecting hoppers of present design do not permit gravity out-flow of fly-ash into a conveyor/ bins without vacuum loss problem. This problem affects system draft, which tends to extinguish boiler flame. Consequently, the provision of Flushing Apparatus (FA) below each fly-ash collecting hopper becomes a necessity, but it essentially requires wet-ash disposal system. iii) The fly-ash collecting hoppers of existing design, have the problem of repeated interruptions in ash out-flow during evacuation cycles, which is caused due to compaction of the collected fly-ash or formation of fly-ash arch within the ash collecting hoppers of critical fields. Major causes of this problem are attributable to long durations of fly-ash storage and condensation of acidic fumes within fly- ash hoppers of critical field. Consequently, the dislodged Fly-ash goes on accumulating within the critical hoppers up to the brim and over flowing fly-ash gets swept back into flue-gas stream, which adversely affects ESP efficiency. Hence, in order to prevent it, the collected fly-ash needs to be removed after short durations or to be continuously removed from the critical hoppers. iv) In the case of fly-ash collecting hoppers of the existing design, it is not possible to store fly-ash for temporary storage and shift fly-ash from one hopper to another due to vacuum loss problem. Hence, it is not possible to make a provision for temporary storage of fly-ash within the ffy-ash collecting hoppers of existing design, which necessitates installation of "Wet-ash Disposal system": v) Since Flushing Apparatus ensure continuous evacuation of fly-ash from fly-ash collecting hoppers and since ash-water slurry pumping systems, inclusive of wet-ash dump yards, ensures 100% availability/ reliability of E5P-hopper system, "Wet disposal ς>f fly-ash" has become an essential requirement since a long time, but this system alone is a cost intensive option, due to high capital investment, high operating/ maintenance cost and excessive power consumption as well as it highly pollutes the natural resources (i.e. adversely affects fertility of the landj contaminates water-bodies and poHgtes atmospheric air) in proximity of wet-ash dump yards and the coal/ Lignite fired industries and powerplants. . . vi) In order to meet the mandatory statutory requirement of MOEF Notification'99 (i.e. full utilization fly-ash in dry state by 2009), presently, two types of ash- handling systems (i.e. Wet and Dry) are being installed in old and new power plants in India. For instance, now-a-days, "Dense-Phase Air Conveying Systems" are being installed for evacuation of fiy-ash in dry state from ESP- hoppers, besides installation of "Wet-ash Disposal Systems" in old and new power plants, but provision of two ash handling systems fails to address the limitations of the fly-ash hoppers of the existing design. vii) On account of the above reason, it is high lighted that provision of two types of ' ash-handling systems (i.e. Wet & Dry) for ensuring optimum management of fly-ash (in wet and dry states) has become a CoIoS¹SaIIy expensive venture. For example, the total capital investment in two types of ash handling systems (i.e. dry and wet ash handling systems as well as wet-ash dump yards, inclusive of 64 nos. of fly-ash collecting hoppers of the present state of the art design) normally exceeds 65 crore Indian rupees for a 250 MW power plant. Moreover, the operating cost of these systems for 30 years may also exceed 60 crore Indian rupees. Thus, installation of two ash handling systems is a wasteful expenditure of colossal amount. Hence, compulsion of providing two types of ash handling systems due to various limitations of Fly-ash collecting hoppers of the present design philosophy, the serious problem of pollution of natural resources and colossally high capital investment are major factors, which demand change in the design philosophy Qf Fly-ash hoppers presently in vogue, which must eliminate the disadvantages of the present state of the art hoppers and the related technologies for ensuring economical, hassle free and pollution free disposal of fly-ash in dry state.

4. OBJECTS OF THE INVENTION

The primary object of the present invention, i.e. "Multi-Port Twin Compartment Fly-ash Hopper" (MPTC-Hopper), is to completely address the limitations and problems, which are being faced with fly-ash collecting hoppers of the present state of the art (i.e. hoppers of the present design).

The next important object of the present invention (i.e. "MPTO- hopper") is to ensure pollution free, haδsje free, economical and optimufh management of fly-ash in "Dry-State" from collection to disposal stages, in Coal/ Lignite fired industries and power plants.

Another important object of the present invention is to provide an environmental friendly technology, which becomes instrumental in dispensing with Wet-ash disposal Systems (i.e. ash-water slurry pumping systems and wet ash dump yards) presently in vogue that tend to pollute natural resources due to pumping of ash-water slurry into wet-ash dump yards and consume colossal amount of power and water.

Another object of the present invention (i.e. tylPTC-hopper) is to create a "Temporary Inbuilt Storage Capability" within each fly-ash hopper of the ESP Hopper- System, which would ensure optimum operational flexibility, 10Q% availability and 100% reliability of ESP-hopper System, during collection, evacuation, storage and disposal cycles (i.e. Fly-ash management activities) for ensuring disposal of fly- ash in dry state.

Still another object of the present invention (i.e. MPTC-hoppers) is to prevent formation of arch (arching-problem) and/ or compaction of fly-ash within fly-ash collecting hoppers as well as to ensure hassle-free, smooth out-flow of fly-ash and uninterrupted "evacuation" of Fly-ash in "Dry $tate" from both critical and non-critical fly-ash hoppers, even after very long storage periods.

Yet another object of the present invention (i.e. MPTC-hopper) is to permit evacuation of fly-ash by gravity directly into conveyors, bins/ hoppers, placed directly below the MPTC-hoppers without vacuum loss problem. Further object of the present invention (i.e. MPTC-hoppers) is tb provide an "ESP Hopper-System", which would permit "shifting" of collected fly-ash from critical hoppers to no^ήrcritical hoppers for temporary storage, because this capability would reduce duration of storage period of fly-ash in critical hoppers (i.e. it would be instrumental in preventing -longer periods pf fly-ash storage in critical hoppers); would give breathing time to critical-hopper system by ensuring availability of empty critical hoppers for allowing uninterrupted collection of fly-ash and would prevent undue loading of the ash collecting hoppers up to the brim.

Another_. object of the present invention is to ensure adequate cooling of fly-ash stored within these hoppeFS with air and/ or water cooling facilities (internal and/ or external cooling facilities).

Yet another object of. the present invention is to provide an "ESP Hopper- System", which would give enough breathing time for further handling, storage (as buffer stock) and disposal of "Cool fly-ash in Dry state" to meet the statutory requirements of MOEF Notificatioh'99 with assured operational flexibility and 100% system availability & reliability.

5. STATEMENT OF INVENTION

Although this innovative product (MPTOhopper) is also a Fly-ash collecting hopper, yet it also has. a provision for enough storage capacity within for facilitating temporary storage of fly-ash. For example, each MPTC-hopper would have total storage capacity of about16 hours as well as Jt would have a provision of about 8-hour storage capacity for temporary Storage of Fly-ash_* Moreover, it would also be possible to shift the collected fly-ash from critical hoppers to non-critical hoppers for temporary storage.

On account of the above said unique features of MPTC-hoppers, they would not face all those problems, which are being faced by Fly-ash collecting hoppers of the existing design. Hence, the present invention pertains to development of a fly-ash hopper (i.e. Multi-Port Twirl Compartment hopper) of unique design, which would ensure hassle free and economical management ^• of fly-ash in "Dry-State" from collection to disposal stages; would ensure optimum operational flexibility; would have storage capability of about 16 hours and a provision for temporary storage within for about eight (8) Hours duration; would ensure 100% availability and reliability of ESP- hopper system; would be instrumental in elimination of Wet-ash disposal system (Ash- water Slurry Pumping system and Ash Dump Yards); and would fulfill the mandatory statutory requirements of MOEF Notification'99 with single ash handling system for disposal of fly-ash in dry state.

MPTC-hoppers (56 or 64 Nos. in a 250 MW unit) would become part and parcel of an "ESP hopper-system" to be located below Electrostatic Precipitators (ESPs) in coal/ lignite fired industries and power plants.

Moreover, in order to ensure economical and optimum management of Fly-ash in dry-state (i.e. collection, evacuation, shifting, storage and disposal of fly-ash in dry state) as well as for ensuring hasste free and effective functioning of ESP-hopper System, following "Supporting Facilities and Ash-handling Systems" have been envisaged:

i) Internal Fly-ash Handling System (essential requirement) ii) Underground Storage Facility (optional requirement) iii) External Ash Handling system (essential requirement)

Iv) Covered Storage Yard (essential requirement) v) Wagon/ truck Filling station (essential requirement) vi) Bag Filling stations (optional requirement)

6. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein:

Fig-1 : Layout drawing of the present invention (MPTC-Hopper) and Air-cooling system.

Fiq-2: Supporting Facilities for Management of Fly-ash in Dry-state, complete with MPTC-hoppers, Internal & External Ash handling system, Covered Storage Yard (CSY) and Wagon/ truck Filling Station (FS).

Fiq-3: Schematic flow diagram of ESP- Hopper System and Internal Ash

Handling System (Link-conveyors & Elevators) for fly-ash evacuation and temporary storage within MPTC-hoppers.

Fiq-4: Layout of ESP-hopper system and Underground Fly-ash Storage

Hoppers (UGH), an Underground Storage Facility. 7. SUMMARY OF THE INVENTION

The proposed invention pertains to "Multi-Port Twin Compartment Fly-ash Hopper (i.e. MPTC-Hopper)". A large number of Fly-ash hoppers (i.e. MPTC-hoppers) are to be installed below Electrostatic Precipitators. It is termed as ΕSP-hopper System". In order to ensure optimum functioning of the entire "Dry Fly-ash Management System", provision of above mentioned "Supporting Facilities" has been envisaged. The major components of MPTC-hoppers and related supporting facilities are briefly described below:

i) Multi-Port Twin Compartment Hopper (Ref. Fiq-1)

Design Philosophy

The present invention, "Multi-port Twin Compartment Fly-ash Hopper (i.e. MPTC-hopper)" has been designed according to a unique innovative design philosophy, which would prevent arch formation or compaction of collected fly-ash within MPTC-hoppers; would ensure hassle-free, uninterrupted and smooth out-flow of fly-ash from critical and non-critical hoppers during evacuation cycles; would prevent fiHing-up of hoppers up to the brim and prevent sweeping of collected fly-ash from the ash collecting hoppers back into the flue-gas stream; would ensure evacuation of fly- ash in dry state from ESP-hoppers by gravity via conveyors without any vacuum loss problem; would permit shifting of fly-ash from critical hoppers to non-critical hoppers for temporary storage within them; would ensure total storage capacity of about 16 hours per MPTC-hopper; would have provision for temporary storage of fly- ash (within each MPTC-hopper) for a period of about eight (8) hours and 6 to 8 shifts within the ESP hopper-system; would allow air and/ or water cooling of fly-ash stored within these hoppers (internal and/ or external cooling facilities); would ensure economical and hassle free fly-ash management in dry state; would be instrumental in meeting mandatory statutory requirements of MOEF Notification'99 as well as in preventing pollution of natural resources caused due to pumping; of ash- water slurry into ash ponds by dispensing with Wet-ash disposal systems (i.e. Ash- water Slurry Pumping Systems and Ash dump yards) presently in vogue.

With regard to "uniqueness of the design philosophy" of the innovative design of fly-ash hoppers, it is claimed that each MPTC-hopper would have huge storage capacity of about -16 hours and the ESP-hopper system (comprising MPTC-hoppers) would have a provision for temporary storage for 6 to 8 shifts. Also, it would be easily possible to shift fly-ash from critical hoppers to non-critical hoppers for temporary storage to give enough breathing time to the hoppers of the critical fields. The above said features are the uniqueness of the design philosophy of the proposed MPTC- Hoppers & the ESP Hopper-system, which would become instrumental in dispensing with Wet-ash disposal systems.

Major Components of each MPTC-Hopper (ref: Fiq-1)

A "Multi-Port Twin Compartment Hopper" consists of two Compartments, which are isolated by ON-Off Port-valves. Main components of each "Multi-Port Twin Compartment Hopper" are as under: i) Upper Compartment (UC):

The Upper compartment consists of a Bin and four (4) or more Pyramid shaped Passages (PP) for fly-ash evacuation. Each passage (PP) has an opening (or port) at its apex for evacuation.

H) Lower Compartment (LC):

The Lower compartment consists of a Bin and four (4) or more pyramid shaped passages (PP) for fly-ash evacuation. Each passage (PP) has an opening (or port) at its apex for evacuation. iii) ON-Off Port Valves (UPV & LPV):

One (1) or two (2) Port-Valves have been envisaged at the apex (opening) of each passage (PP). These are ON-Off valves, which isolate the upper and lower compartments of MPTC-hopper and prevent vacuum loss problem during fly-ash evacuation cycles. iv) Cooling Facilities (CFV:

Air-cooling facility has been envisaged within and/ or out-side upper and lower compartments (UC & LC) of MPTC-hoppers, while water-cooling facility (an optional requirement) has been envisaged out-side the lower compartments (LC). v) Facility to Shift Fly-ash into Lower Compartment (LC):

Two openings (TSO) have been envisaged at top of Lower compartment (LC) of each MPTC-hopper to receive Fly-ash via Link-conveyors for temporary storage of fly-ash within the Lower Compartment (LC). vi) Ash Sweeping Rotor (ASR):^'

One (1) Ash sweeping rotor (ASR) has been envisaged within each bin of Lower compartment (LC)₁ but it is an optional requirement. It would shift fly- ash towards the active openings of lower compartments (LC) and would also ensure smooth out-flow of ash without any interruption during evacuation activities. It would also break arch-formation and prevent compaction of fly- ash within Lower Compartments.

ϋ) ESP-Hopper System (Ref: Fϊg-3)

An Electrostatic Precipitator (ESP) dislodges fly-ash from the Flue-gases flowing within. The dislodge fly-ash gets collected into "Fly-ash Hoppers", which are, installed below an ESP in coal/ Lignite fired industries and power plants. The "ESP hopper-system" consists of a large number of fly-ash hoppers (i.e. MPTC-hoppers). It operates according to modular concept and each module represents an independent row of fly-ash tioppers. For instance, ESP hopper-system, for a 250 MW unit, comprises of eight (8) modules (i.e. rows) and each module (row) has seven (7) or eight (8) field-hoppers. Thus, an ESP-hopper system in a 250 WIW unit consists of 56 or 64 Fly-ash hoppers arranged in the matrix-pattern of 7 or 8 fields and 8 rows. In the case of 500 MW units, there are 16 modules (rows) and each module has 8 or 9 fields. Fly-ash hoppers (i.e. MPTC-hoppers) in each row are termed as Field-hoppers. Thus, there are 7 or 8 field-hoppers per row and 8 hoppers per field.

Hi) Supporting Facilities (Ref: Fig-2)

"Supporting Facilities" for an "ESP-Hopper System", comprising MPTC-hoppers, consist of Internal and External ash handling systems. The internal and external ash handling systems together represent a "single ash handling system" for each unit (250 or 500 MW unit) in the coal/ lignite fired industry/ power plant, which would ensure hassle free evacuation, shifting, storage and disposal of fly-ash in Dry-state by road, rail or bags. Underground Fly-ash storage hoppers are part of the internal ash handling system, while Covered Storage Yards (CSY) and Wagon/ truck/ bag filling stations (FS) are parts of the external ash handling system. The ESP-hopper system and the above said supporting facilities together make this invention effective in ensuring economical and hassle free handling and disposal of fly-ash in dry state.

Internal Ash Handling System (Ref: Fjq-3 & Fig-4)

Internal ash handling system is an integral part of the ESP-hopper system. Therefore, it remains confined to ESP-Area. It consists of ^"a combination of "Link- conveyors and Elevators". It is an essential requirement. It would be able to handle hot fly-ash without any problem. Two (2) link conveyors have been envisaged for each MPTC-hopper. An "Underground storage facility", which consists of underground hoppers (UGH) to be located below ESP-hopper system, has also been envisaged as part of the internal ash handling system, but it is an optional requirement.

The major activities of the internal ash handling systqm arfc "Fly-ash Evacuation" from ESP-hopper system as well as "Shifting of fly-ash" from lower cornpartmέnts of critical hoppers to those of non-critical hoppers for "Temporary Storage". These . activities have -been envisaged for ensuring optimum operational flexibility of ESP-hopper system and 100% availability of critical hoppers for fly-ash collection.

External ash handling system (Ref: Fig-2)

External ash handling system is installed outside the ESP-Area. It would consist Of a set of Belt-conveyors and Bucket elevators; a Covered Stock Yards (CSY); and Wagon, truck and/ or bag filling stations. .

"Covered Stock Yards (CSY)" are essential features of ^'. the external ash handling system. The "Covered Stock_, Yards" are buffer stock yards, which are to be designed to have 10 to 20 days fly-ash storage (holding) capacity to cater for daily production of fly-ash in power plants during low demand or no demand periods.

8. DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:

Reference may be made to the accompanying drawings (Fiq-1 to fjgj4).

1. Multi-Port Twin Compartment Hopper (Ref: Fig-1) Major Components

A "Multi-Port Twin Compartment Hopper" consists of two (2) Compartments (i.e. Upper compartment and Lower compartment). Each compartment is made up of a Bin and Four (4) pyramid shaped passages with an opening at the apex for out-flow of ash. One (1) or two (2) ON-Off Port- valves (PV) have been envisaged at the apex of each passage. The Upper and Lower compartments are isolated by Port-valves (PV). The port-valves of the upper Compartment (UC) and those of Lower Compartment (LC) have been termed as Upper and Lower port-valves (i.fe. UPV & LPV) respectively.

Total height of a MPTC-hopper with two compartments, multi- passages and Port-va|ves (PV) would be 9.0m to 9.5m. Total headroom requirement below the ESP, for accommodating the MPTC-hoppfers complete with Internal Ash handling systern, would depend upon the "grid dimensions" of ESP-hopper system. For instance, for Grid-dimensions of 6.0m x 5.5m, the total head-room requirement would be 11.0 m.

Significance & functions of various components of MPTC-hopper (refiFig-1):

i) Upper Compartment (UC):

The Uppec compartment consists of a Bin and four (4) or more Pyramid shaped Passages (PP). Each passage (PP) has art opening (or port) at its apex for evacuation of fly-ash and each port has one (1 ) or two (2) ON-Off Pύrt-valves, i.e. upper port-valves (UPV).

The upper compartment is to be connected to the bottom of the ESP (below ash collection area) for collection of dislodged fly-ash. Thus, the dislodged fly-ash gets collected within the upper compartment (UC). Total storage capacity of about 8 hours has been envisaged for this compartment (bin + four passages). The collected fly-ash is discharged from the upper compartment (UC) into the lower compartment (LC) for temporary stojage, cooling and evacuation.

ii) Lower Compartment (LC):

The Lower compartment also consists of a Bin and four (4) or more passages of pyramid shape (PP) for fly-ash evacuation. Each passage (PP) has an opening (or port) at its apex for evacuation and each port has one (1) or two (2) ON-Off Port-valves (LPV).

The lower compartment of each MPTC-hopper receives fly-ash directly from the upper compartment for temporary storage and cooling. Moreover, the fly-ash is also shifted from the lower compartments of critical hoppers into the lower compartments of non-critical hoppers for temporary storage. Thus, lower compartments can receive fly-ash from two sources, i.e. upper compartments and lower Compartments of critical hoppers.

Thus, the lower compartment (bin + four passages) of each MPTC- hopper functions as a temporary storage facility. This unique feature of MPTC- hoppers allows "Shifting of Fly-ash from lower compartments of one hopper to those of other hoppers in the same row". This capability allows "Shifting of fly- ash" from lower compartments of critical hoppers into those of non-critical hoppers, which ensures emptying of lower compartments of critical hoppers once or twice a shift and gives enough breathing time to critical MPTC-hoppers, because it prepares lower compartments of critical MPTC-hoppers to receive fly-ash from the respective upper compartments of critical MPTC-hoppers in the next fly-ash discharging-cycle.

In other words, the ash "Shifting-capability" ensures optimum operational flexibility in fly-ash hopper-evacuation system. For instance, this capability empties lower compartments of critical hoppers once or twice a shift and makes them ready to receive collected fly-ash from the upper compartments. Consequently, this capability ensures 100% availability of upper compartments of critical MPTC-hoppers for ash collection and prevents overflowing of upper compartments. Moreover, the shifted fly-ash is allows to remain stored within the lower compartments of non-critical hoppers for about 4 to 6 shifts prior to evacuation. Consequently, this capability naturally cools the fly- ash stored within the lower compartments of non-critical hoppers. Hence, this capability also provides enough breathing time for maintenance of the port- valves (PV) and internal and external ash handling systems.

Thus, provision of Upper and Lower compartments in MPTC-hoppers, which are the unique feature of the MPTC-hoppers, make the entire fly-ash management system (for dry disposal of fly-ash) very versatile and flexible in its operations as well as it holds the key that addresses vacuum loss problem, arch-formation problem, ash compaction problem and repeated interruptions in fly-ash evacuation. Indirectly, these features also become instrumental in dispensing with Wet-ash disposal system presently in vogue, because these provisions give enough breathing to the upper compartments (UC) of the critical hoppers to continuously collect the dislodged fly-ash without any problem of over flowing of ash.

iii) ON-Off Port Valves (UPV & LPV):

Two (2) Port-Valves (ON-Off valves) have been envisaged at the apex (opening) of each passage (PP) of the upper and lower compartments of MPTC-hoppers. The upper port-valves (UPV) isolate the upper and lower compartments of MPTC-hopper. During the evacuation cycle of the lower compartment, the lower port-valves (LPV) are to be kept in the open mode, while the upper port valves (UPV) remain in tightly closed mode. Thus, the port- valves (UPV & LPV) ensure evacuation of fly-ash from MPTC-hoppers without any vacuum loss problem. iv) Water or Air Cooling Facility (CF):

Adequate cooling facilities have envisaged for cooling the collected and/ or stored fly-ash within each compartment (i.e. UC & LC). Air-cooling facility has been envisaged within and/ or out-side these compartments (UC & LC)₁ while water-cooling facility (optional) has been envisaged out-side the lower compartments. (LC):

With regard to the Air-cooling facility, the external air-cooling facility envisages ducting material to cover the Upper & Lower compartments from the bin up to apex (opening) of to the passages (PP), excluding the port-valves (Ref: Fig-2). Separate ducting has been envisaged for each compartment. An air discharge pipes has been envisaged for each compartment for discharging hot air directly into the atmosphere from the air-ducts.

In the case of Internal Air-cooling facility, vertically arranged air-pipes with nozzles (4 to_.6 nos. per air-pipe) starting from top of the bin of the lower compartment up to Ash-sweeping Rotor (ASR) have been envisaged within the lower bin. It is an optional requirement. An "Exit-air pipe with a non-return valve and an ON-Off valve" has also been envisaged for removing hot air from the lower compartment during the cooling cycle of the Lower compartment.

Cooling cycle is the operating period of the Internal Air-cooling facility and it commences when upper and lower port-valves (UPV & LPV) are in closed mode. The period of cooling cycle is 2 or 4 hours per cycle/ shift and it depends upon the numbers of "Working Cycles" per shift. For instance, in the case of single working cycle per shift, the cooling period is 4 hours. In this period cool-air is blown via nozzles into the bins of lower compartments of critical hoppers and hot air is allowed to escape via the exit pipe. The blowing of cool air, within the mass of fly-ash stored in the bin of lower compartments of critical hoppers, ensures faster cooling of the fly-ash. In addition to the above cooling facility, Air fluidizing has been envisaged for all the passages of upper and lower compartments of MPTC-hoppers.

iii) Facility to Shift Flv-ash into Lower Compartment (LC):

Two openings for temporary storage (TSO) of fly-ash within the Lower Compartment (LC) have been envisaged at the top of the Lower Compartment (LC) of each MPTC-hopper for receiving Fly-ash via Link-conveyors. This provision permits periodic evacuation of fly-ash from the lower compartments (LC) of critical hoppers for shifting it into those of non-critical hoppers via the above said two openings (TSO). During the evacuation cycle, the fly-ash stored in the lower compartment of critical hoppers is shifted to those of the non-critical hoppers via these openings. The period of shifting the fly-ash from critical hoppers to non-critical hoppers depends upon the number of evacuation activities/ shift. In other words, the shifting period is equal to the duration of evacuation activity for fly-ash removal from the lower compartment of critical hoppers.

vi) Ash Sweeping Rotor (ASR):

One (1) Ash sweeping rotor (ASR) has been envisaged within each bin of Lower compartment (LC), which would shift fly-ash towards its active openings and ensure smooth out-flow of ash without any interruption during evacuation activity. It would also break arch-formation and prevent compaction of fly-ash within Lower Compartments, but it is an optional requirement.

In order to fulfill the stated objectives, the above said features would cater for the following unique requirements of ESP-hopper system: i) Availability of "Empty" Lower compartment to allow the upper compartment to discharge the collected fly-ash into it. Consequently, the upper compartment would also be available for further collection of dislodged fly-ash. ii) "Hassle-free and uninterrupted Unloading" of Fly-ash into Link-conveyors by gravity without Vacuum loss problem. iii) Shifting of fly-ash from critical hoppers to non-critical hoppers for temporary storage within lower compartments and cooling. iv) Breaking Fly-ash Arch-formation and mitigating ash compaction problem.

2. ESP-Hopper System (Ref: Fig-3)

An "ESP-hopper System" consists of a large number of fly-ash collecting hoppers (MPTC-hoppers). "ESP-Hopper System" operates according to modular concept and each module represents an independent row of hoppers. For instance, an "ESP hopper-system", in the case of a 250 MW unit, comprises eight (8) modules (i.e. rows of hoppers) and each module (row) has seven (7) or eight (8) field-hoppers. Thus, a 250 MW unit has 7 or 8 fields and 8 rows. In the case of 500 MW units, there are 16 modules (rows) and each module has 8 or 9 fields. Thus, an "ESP-hopper System comprises 56 or 64 "Multi-Port Twin-Compartment Fly-ash Hoppers (MPTC- hoppers)" for each 250 MW unit and 64 to 72 fly-ash hoppers for each 500 MW unit. 3. Supporting Facilities For Fly-asn Management in urv oiate

In order to ensure hassle free ahd effective functioning of ESP-hopper System; to prevent any bottle-neck in the fly-ash disposal system for supplying fly-ash in dry state to the end-users/ ash-brick industries; and to ensure economical and optimum management of Fly-ash (i.e. collection, evacuation, shifting, storage and disposal _. of fly-ash) in dry state, following "Supporting Facilities" have been envisaged (Fig: 1 to 4): i) Internal Fly-ash Handling System (an essential requirement) ii) Underground Stprage Facility (UGH, an optional requirement) iii) External Asrj Handling system (essential requirement) iv) Covered Storage Yard (CSY, an essential requirement) v) Wagon/ truck Filling station (an essential requirement) vi) Bag Filling stations (an optional requirement, hot shown) vii) Cooling Facilities for MPTC-hoppers (an essential requirement)

Internal ash handling system is ah integral part of the ESP-hopper system. It remains confined to ESP-Area. Its major activities would be hassle free evacuation of fly^Lash from lower compartments of MPTC-hoppers and shifting of fly-ash from critical hoppers to non-critical hoppers as well as evacuation of cool fly-ash from non-critical, hoppers for feeding the external ash handling system for further transportation of fly- ash in dry state to "Covered Storage. Yard" for storage as buffer stock.

An "Underground Storage Facility" (Ref: Fig-4), which consists of underground hoppers (UDH), has also been envisaged. The underground hoppers are to be located below the "ESP-Hopper System". This facility becomes essential, when acquisition of large area of land is a serious problem or when the cost of land is very high, but it is an optional requirement. In such a case, the "Underground storage facility" also becomes an integral part of the "ESP-Hopper System". It would consist of 56 to 64 underground hoppers (UGH) to be directly located below "MPTC-hoppers" and would be designed to cater for 10 to 12 days (i.e. 30 to 36 shifts) storage capacity. This facility further improves operation versatility and reliability of the "ESP-hopper System".

"External ash handling system" (Ref: Fig-2) is installed outside the ESP-Area. It would ensure hassle free transportation of fly-ash in dry state for storage in Covered Storage Yard and disposal of fly-ash in Dry-state by road, rail or bags. Thus, "Covered Storage Yards (CSY)" as well as "Wagon, truck and/ or bag Filling Stations (FS)" are essential features of the external ash handling system. The "Covered Storage Yards" are buffer stock yards, which are to be designed to have 10 to 20 days fly-ash storage (holding) capacity to cater for daily production of fly-ash in power plants during low demand or no demand periods.

Demerits & Limitations of MPTC- Hopper System

Major limitations of the MPTC-hpppers and ESP-hopper System are as under: i) Each MPTC-hopper complete with port-valves is appreciably more expensive than the fly-ash collecting hoppers of existing design, ii) Each MPTC-hopper has appreciably more overall height than the fly-ash collecting hoppers of existing design, iii) Total Headroom requirement for each MPTC-hopper is more than that of fly-ash collecting hoppers of existing design, iv) In order to prevent vacuum toss problem, preventive maintenance of port-valve assemblies is an essential Requirement, y) Air-cooling facility, for MPTC-hoppers, is an additional essential requirement.

Merits of MPTC-Hopper Design

The merits of the MPTC-hoppers, ESP-hopper-system and Supporting Facilities envisaged jointly off-set the above said demerits. The glaring merits in this regard are highlighted below: i) Each MPTC-hopper is free from arch-formation and ash compaction problems as well as it permits uninterrupted evacuation of fly-ash via Link-conveyors without vacuum loss problem, ii) It is possible to shift Fly-ash from one MPTC-hopper to another for temporary storage. This capability would ensure 100% availability of MPTC-hoppers for collection of dislodged ash. iii) It is possible to store fly-ash within lower compartments of MPTC-hoppers for temporary storage. Consequently, ESP-hopper System has provision of temporary storage for 4 to 6 shifts, iv) Link-conveyors are capable of handling hot fly-ash and require normal maintenance. Provision of "Two Link-conveyors" per row of hoppers has been envisaged for shifting ash from critical hoppers to non-critical hoppers and evacuation of ash from non-critical hoppers. They are essential requirements for optimum functioning of MPTC-hoppers, because they ensure optimum reliability in.management of dry fly-ash within and around ESP-hopper system, v) "Covered Storage Yards" ensure 100% reliability for the proposed "Fly-ash

Management System" during low or no demand periods. in view of the above said merits, it is claimed that MPTC-hoppers would become instrumental in dispensing with Wet-ash Disposal System (Ash-water slurry Pumping systems and Wet- ash dump yards) in new ventures. It would also result huge saving in capital and operating costs.

9. Working Principle of FIv-ash Management System

i) Working Principle of MPTC-Hoppers and Supporting Facilities

Fly-ash dislodged by ESP is allowed to get collected within Upper Compartments (UC) of MPTC-hoppers. In the case of fly-ash hoppers of critical field of ESP-hopper System, the dislodged fly-ash is allowed to collect for three (3) to six (6) hours per shift depending upon the number of working cycles per shift. Thereafter, collected fly-ash is discharged into Lower Compartments for temporary storage for three (3) to six (6) hours per shift. During this period, the fly-ash stored in the lower compartments is also shifted into lower compartments of non-critical hoppers in the same row for temporary storage for longer period ranging from four (4) to six (6) shifts.

Link-conveyors & Elevators, the part & parcel of "Internal Ash handling system", shift the fly-ash from critical hoppers into lower compartments of non- critical hoppers for temporary storage as well as they evacuate stored fly-ash from lower compartments of non-critical hoppers for feeding the "External ash handling system" for storage within "Covered Storage Yards" for still longer durations. The fly-ash stored within "Covered Storage Yards" is shifted to wagon/ truck Filling Stations (FS) for disposal of dry fly-ash by rail/ road to end users). During low or no demand periods, the daily production of the Fly-ash is stored within "Covered Storage Yards".

With regard to underground storage hoppers (UGH), the underground storage facility, the fly-ash is directly unloaded into underground hoppers (UGH) from lower compartments of critical and non-critical hoppers (located directly above). The underground Link-conveyors are also part and parcel of internal ash handling system, which remove fly-ash from underground hoppers (UGH) for feeding the external ash handling system for further storage or disposal by road/ rail. The belt-conveyors of the external Ash handling system, in tnrs case, are also installed underground at lower elevation than the Link-conveyors.

Operating Cycles for MPTC-hoppers & Port-valves (UPV & LPV)

With regard to "Working Cycle" of MPTC-hoppers, four operating cycles have been envisaged (i.e. Ash Collecting cycle, Discharging cycle_r Cooling Cycle and Evacuation cycle). One complete "Working Cycle" comprises four operating cycles of varied durations.

During "Ash Collecting cycles", the dislodged fly-ash is allowed to collect into upper compartment (UC) only and not into Lower Compartment (LC). In this cycle, both upper & lower port-valves (UPV & LPV) remain in closed mode. This cycle is followed by "Discharging cycle".

During "Discharging cycle", the dislodged fly-ash and fly-ash already collected within upper compartment (UC) fall down by gravity into the lower compartment (LC) .for temporary storage. During this operating cycle, upper port-valves (UPV) of upper compartment (UC) remain in open-mode, while lower port-valves (LPV) of lower compartment (LC) remain in close-mode. Upper and lower port-valves (UPV & LPV) are closed as soon as the "Discharging cycle" ends, which is followed by "Cooling Cycle".

During "Cooling Cycle", the "Inner Air-cooling System" operates and blows cool air within the mass of the fly-ash- stored in the lower compartments of critical hoppers for ensuring effective and faster cooling of stored fly-ash. During this cycle, both upper and lower port-valves (UPV & LPV) remain in closed mode.

"Evacuation Cycle" commences as soon as the "Cooling cycle" ends. During "Evacuation Cycle" the lower port-valves are kept in open-modes and upper port-valves remain in close-mode as well as the "Inner Air-cooling System" is shut down. During this cycle, the fly-ash is unloaded by gravity from lower compartments (LC) of critical hoppers into respective "Link-conveyors" for shifting the fly-ash into those of non-critical hoppers for temporary storage or for feeding the external ash handling system for further storage into "Covered Storage Yards". This cycle is followed by "Ash Collecting cycle". Hi) Operating Periods for Port-valves (UPV & LPV)

"Operating Periods" of the above four operating cycles per shift (or day) for the critical MPTC-hoppers depend upon the number of ash collecting, discharging, cooling and evacuation cycles envisaged per shift (or per day). For instance, in the case of two (2) "Working-Cycles" per shift (i.e. four (4) hour duration each), "Ash Collecting period" is three (3) hours, "Discharging period" is one (1) hour; "Cooling period" is two (2) hours; and "Evacuation period" is one (1) hour. In the case of one (1) "Working-Cycle" pet shift, "Ash Collecting, Discharging, Cooling and Evacuation periods" are six (6) hours, two (2) hours, four (4) hours and two (2) hours respectively. Soon after evacuation cycle, both the port-valves are closed.

The above rule is not applicable for non-critical hoppers. In this case, upper port-valves (UPV) remain in closed mode for very long durations as the rate of fly-ash collection in upper compartments is very low. During "Discharging Cycles", these valves are kept in open mode for about two (2) to three (3) hours after two (2) dr three (3) days for discharging the collected fly-ash into lower compartments. Moreover, the fly-ash, which is shifted from critical hoppers, is also allowed to remain within lower compartments of non-critical hoppers for 30 to 45 hours for cooling (by external air-cooling system) and temporary storage, prior to removal for feeding the external ash handling system. During the above cooling period, both upper & lower port-valves (UPV & LPV) are kept in close mode, but upper port-valves (UPV) are opened (in between the cooling period) for 2 to 3 hours to allow unloading of collected fly-ash from upper compartments into lower compartments after 2 or 3 days during "Discharging Cycles". During the ash removal activities from the lower compartments of non-critical hoppers, the lower port-valves (LPV) are opened and upper port-valves (UPV) remain in closed mode.

It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims.

Claims

I Claim

1. "Multi-Port twin Compartment Hopper" (i.e. MPTC-ϊiopper), which comprises Upper and Lower Compartments &nd each compartment consists of a bin; four pyramid shaped passages, each with a port (opening) at its apex; and two On-OfF port-valves attach port (opening) for controlling (i.e. by closing or opening the port) out-flow of collected and/ or stored fly-ash from these compartments ^"during ash discharging and/ or removal activities, is to be installed below ash collecting area of an Electrostatic Precipitator (ESP).

2. Each "MPTC-hopper", as claimed in claim-1, is an integra.1 part of an "ESP-hύpper System", which consists of large number of Λ/iPTC-hoppers (say 56 to 64 nos. in a 250 MW unit) as well as each "MPTC-hopper", functioning as a "Fly-ash Collecting-cum-Stόrage Hopper", would ensure economical, hassle- free and optimum management (i.e. evacuation, storage, handling and disposal) of fly-ash_, in dry state and would become instrumental in meeting statutory requirement of MOEF-Notification'99, which stipulates that in order to ensure 100% utilization of fly-ash in dry state by end users (i.e. partial replacement of cement in RCG/ ash brick-industries), disposal of fly-ash in dry state is a mandatory requirement.

3. Upper compartment of each "MPTC-hopper", as claimed in claim-1, would collect dislodged fly-ash within bin and four passages, during ash collecting cycle, when all its (upper) port-valves (UPV) are in closed mode as well as it would discharge the collected fly-ash into Lower-Compartment for temporary storage, during ash "discharging cycle", when all the (upper) port- valves (UPV) of upper Compartment are in open modes and all (lower) port- valves (LPV) of Lower compartment are in closed mode.

4. Lower Compartment of each "MPTC-hopper", as claimed in claims-1 & 3, to be located below the upper compartment, has been envisaged to make a provision for "Temporary storage of F1y-ash^B within each MPTC-hόpper with eight (8) hour storage capacity and 30 to 40 hours temporary storage capacity within ESP-hopper system as well as each MPTC-hopper is capable of receiving fly-ash from two sources, i.e. from the respective upper-compartment during discharging cycle as well as from lower compartment of critical-hopper during evacuation cycle for temporary storage into lower compartment of one of the (5 to 7) non-critical hoppers in the same row.

5. "MPTC-hoppers with upper and lower compartments", as claimed in any of the preceding claims, being free from vacuum loss, arch-formation and ash compaction problems, would ensure hassle-free and uninterrupted evacuation (i.e. discharging of ash from upper compartment and removal of fly-ash from lower compartment) of fly-ash from critical and non-critical MPTC-hoppers of "ESP-hopper System".

6. "MPTC-hoppers and ESP-hopper System", as claimed in a_,ny of the preceding claims, would require following "Supporting Facilities", which have been envisaged to perform following integrated functions:

External Air-pooling Facility would cool fly-ash collected in upper compartments as well as fly-ash stored in lower compartments of all MPTC-hoppers of ESP- hopper System, while Internal Air-cooling facility would cool the fly-ash stored in lower compartments of critical hoppers only during "Cooling cycle"; Internal Ash handling system comprising of Link-conveyors and Elevators (confined to ESP- ash collecting area), would evacuate ash from lower compartments of MPTC- hoppers, shift ash from critical hoppers to lower. compartments of non-critical hoppers for temporary storage and feed Underground storage facility as well as it would also feed External Ash handling system, which would transport fly-ash in dry state for storage in Covered Storage Yard (as buffer stock) and/ or to Wagon/ truck/ bag filling stations for disposal of cool fly-ash in dry state.

7. "MPTC-hoppers and ESP-hopper System", as claimed in any of the preceding claims, essentially require ON-Off Port-Valves (UPV & LPV) to be installed at apex of the pyramid shaped passages for controlling out-flow of fly_rash from upper and lower compartments of MPTC-hoppers during Working cycles of "MPTC-hoppers", which' comprise of "ash collecting, discharging, cooling and evacuation cycles". During "ash collecting cycle, all the port-valves (UPV) of upper compartment remain in closed mode; during "discharging cycle", all the port-valves of upper compartment (UPV) are in open mode, while all the port- valves (LPV) of lower compartment are in closed mode; during "cooling cycle", an me port-valves of upper and lower compartments (UPV & LPV) remain in closed mode; and during "evacuation (shifting) cycle, all the port-valves (UPV) of upper compartment are in closed mode, while one or more port-valves (LPV) of lower compartment are in open mode. Operating Periods of these four operating cycles depend upon the number of "Working cycles per shift". For example, when period of working cycle is eight (8) hours (i.e. one working cycle/ shift), the periods of collecting, discharging, cooling and evacuation cycles are 6, 2, 4 and 2 hours respectively.

8) "MPTC-hoppers and ESP-hbpper System", as claimed in any of the preceding claims, on account of their capability of storing fly-ash in Lower compartments for temporary storage, would become instrumental in dispensing with "Wet-ash Disposal Systems" (i.e. Ash-water slurry Pumping Systems and Ash Dump- Yards to store ash-water slurry) presently in vogue .and ensuring installation of only one (1) type of ash-handling system instead of two types of ash handling systems (Wet & Dry) that are being provided now in old and new power plants for ensuring 100% system reliability and for meeting statutory requirements of MOEF-Notification'99, as well as on account of the above said advantages, installation of MPTC-hoppers would be instrumental in ensuring colossal amount of savings in terms of power & water, capital investment and operating costs, besides preventing pollution of Natural resources.

9. "Multi-Port Twin Compartment Hopper", inclusive of "ESP-hopper System and "Supporting Facilities" as herein described with reference to the accompanying drawings.