Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
  • F23J1/00—Removing ash, clinker, or slag from combustion chambers
  • F23J1/02—Apparatus for removing ash, clinker, or slag from ash-pits, e.g. by employing trucks or conveyors, by employing suction devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
  • F23J2700/00—Ash removal, handling and treatment means; Ash and slag handling in pulverulent fuel furnaces; Ash removal means for incinerators
  • F23J2700/001—Ash removal, handling and treatment means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
  • F23J2900/00—Special arrangements for conducting or purifying combustion fumes; Treatment of fumes or ashes
  • F23J2900/01002—Cooling of ashes from the combustion chamber by indirect heat exchangers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
  • F23J2900/00—Special arrangements for conducting or purifying combustion fumes; Treatment of fumes or ashes
  • F23J2900/01003—Ash crushing means associated with ash removal means

Definitions

• the present invention relates to a plant and to a method for the dry extraction and cooling of combustion residues coming from a combustion chamber, in particular for large quantities of heavy ashes originating, for example, from fossil fuel used in thermo-electric energy-producing plants.
• the known cooling systems do not succeed in implementing, in an effective and efficient way, the dry cooling or mainly dry cooling of the heavy ashes and the disposal of the latter and of the related cooling air, above all if such ashes are in large quantities and at high temperature.
• the dry cooling or mainly dry cooling of the heavy ashes and the disposal of the latter and of the related cooling air above all if such ashes are in large quantities and at high temperature.
• even when such cooling and disposal are succeeded to be obtained they are achieved with considerable plant complications and with consequent very high implementation and handling costs.
• the technical problem underlying and solved by the present invention is to provide a system and method for the dry extraction and cooling of combustion residues coming from a solid fuel combustion chamber which allow obviating to the drawbacks just mentioned with reference to the known art.
• the present invention provides some important advantages which will be appreciated in full in the light of the detailed description reported hereinafter.
• the main advantage consists in that the invention allows, in case of coals with high ash content, to carry out an adequate and effective dry cooling of the ash itself without exceeding the above-mentioned limit of 1.0-1.5% of cooling air introduced in the combustion chamber from the bottom. Such advantage is particularly important in the above-mentioned case of coals with high content of heavy ashes.
• the cooling air quantity introduced into the system can be adjusted based upon a combination of measures of ash quantity and/or temperature.
• the present invention mainly relates to an additional cooling system for the dry extraction of heavy ashes produced by solid fuel boilers, apt to reduce the ash temperature.
• the system mainly comprises, arranged subsequentially:
• an in-line cooling device having the function of placing in contact several times the ash with additional air in countercurrent in order to increase the possible exchange without necessarily increasing the air quantity coming back into the combustion chamber - as mentioned above, such additional air is then preferably sent upstream of the air heater or in atmosphere upon captation of fines.
• - figure 1 shows a general layout exemplifying a first embodiment or preferred operation mode of the invention system, providing to send the cooling air coming from a gravitational air/ash exchanger into the fume duct associated to the combustion chamber, upstream of the air heater;
• - figure 2 shows a general layout exemplifying a second embodiment or preferred operation mode of the invention system, providing that the air coming from a gravity air/ash exchanger is moved by an auxiliary fan and discharged into the atmosphere;
• FIG. 3 shows a general layout exemplifying a third embodiment or preferred operation mode of the invention system providing to send the - A - cooling air coming from a gravity air/ashes exchanger into the fume duct associated to the combustion chamber, upstream of the dust removal system;
• - figures 4a and 4b refer to the gravity air/ash exchanger of the previous figures equipped with an air-dosing system, showing a side view and a front view thereof, respectively.
• a system for extracting and cooling combustion residues of the kind used for example in solid fossil fuel thermo-electric plants and according to a first preferred embodiment of the invention, is designated as a whole with 1.
• the system 1 is particularly suitable to handle large flow of heavy ashes, produced, for example by the combustion of coals or lignites with high content of ashes.
• the dffferent component of the system 1 will be described hereinafter by referring to the path followed by the combustion residues from the extraction thereof from the bottom of the combustion chamber (or boiler), designated with 100, to the disposal thereof.
• the system 1 Immediately downstream of the combustion chamber 100, or better of a transition hopper 105 thereof, the system 1 provides a first extraction and/or transport unit, in particular a dry extractor 2 mainly made of steel with high thermal resistance.
• a dry extractor 2 mainly made of steel with high thermal resistance.
• Such extractor 2 is of an already known type and described for example in EP 0 252 967, herein incorporated by means of this reference.
• the extractor 2 gathers the heavy ashes which precipitate downwards into the combustion chamber 100 through the transition hopper 105 mentioned above.
• Extractor 2 at the side walls of its own casing, has a plurality of entrance holes for the outer cooling air, distributed in a substantially regular way along the development of the extractor 2 itself and each one designated with 13.
• Such entrances 13 preferably are equipped with means for regulating cooling air - flow, for example one or more gate valves, apt also to wholly interdict one or more selected entrances.
• Cooling air is sucked through the entrances 13 inside the extractor 2 and in countercurrent with respect to the ashes' transportation because of the depression existing in the combustion chamber 100. More in detail, the air enters thanks to the depression existing in the transition hopper 105, on the bottom thereof there is a depression adjusted by the control system of the combustion chamber 100 (generally around 300-500 Pa under the atmospheric pressure). Such cooling air involving the extractor 2 enters then the boiler 100 from the bottom thereof.
• the ashes Downstream of the extractor 2 the ashes are fed to a breaker or crusher 3, which triturates the coarsest fractions thereof so as to increase the thermal exchange surface and thus to improve the potentials of such exchange and therefore the cooling process.
• the ashes Downstream of the crusher 3, the ashes are conveyed to a second extraction and/or transport unit, in particular a steel-belt conveyor-cooler 4.
• a second extraction and/or transport unit in particular a steel-belt conveyor-cooler 4.
• the ash continues to be cooled by means of air in countercurrent resucked from the outside through additional entrances 13 arranged onto the side walls of the conveyor 4 itself in a way analogous to what already illustrated for the first extractor 2.
• additional entrances 13 arranged onto the side walls of the conveyor 4 itself in a way analogous to what already illustrated for the first extractor 2.
• the air is resucked from the mentioned-above depression existing in the combustion chamber 100 and also such entrances can be equipped with means for flow - regulation of the already described kind.
• the cooling air involving such second conveyor 4 enters the boiler from the bottom thereof.
• a duct for the passage for the cooling air can be provided between the conveyor 4 and the extractor 2 for the bypass of the crusher 3. v
• the system 1 is equipped with a dry cooling system, implemented among other things by the air entrances 13.
• such cooling system Downstream of the second conveyor 4 such cooling system comprises an air/ash dry gravitational thermal exchanger, preferably of the plate-like type 19, designated as a whole with 5 and shown in greater detail in the figures 4a-4b.
• the plates 19 preferably are made of wear-resistant metal.
• the system 1 can provide an additional crusher 10, which can be selectively driven in case of need.
• an additional cooling air entrance 17 is then provided, equipped with means for cooling air - flow regulation as well, of the already described kind.
• the system 1 further provides a third extraction and/or transport unit, in particular a third conveyor 6 ending into a silo 11 for discharging the ashes* for their disposal and/or possible reuse thereof.
• an additional air entrance 14 is provided, equipped with means for cooling air - flow regulation as well, of the already ' described type.
• the ash crushed by the crusher 3 and in case if necessary by the crusher 10 mixes intimately with the air introduced in countercurrent by the entrances 14 and 17 during the falls from plate to plate, by increasing the thermal exchange and thus increasing the heat quantity transmitted by the ash to the air.
• the system 1 then comprises means for sensing the temperature and/or volumetric and/or ponderal flow of the ashes which in the present example are arranged at the ending portion or the exhaust of the conveyor 4 and/or on the main extractor 2 or more preferably at the ashes' discharge at the conveyor 6.
• the system 1 further comprises control means, in communication with said sensor means and apt to control the cooling system mentioned above as well as the extraction and/or transport units 2, 4 and 6.
• the system 1 then comprises feeding means apt to send part of the cooling air - and in particular the additional air introduced through the entrances 17 and 14 and which crosses the exchanger 5 - downstream of the ashes' . cooling process, into the atmosphere or in a fume duct 101 associated to the combustion chamber 100.
• said additional air necessary to cool the ashes in the gravity air/ash exchanger 5 and introduced through the additional entrances 14 and 17 can follow three different paths depending upon the specific embodiment or considered construction configuration.
• the cooling air introduced through the additional entrances 14 and 17 is resucked, downstream of the countercurrent crossing of the exchanger 5, by the depression of the fume duct 101 upstream of an exchanger 102 associated to the boiler 100.
• Such exchanger 102 usually existing in the known systems, is used to pre-heat the combustion air. Said cooling air, heated by the ashes, is then sent in such exchanger 102 (fume side) and used for preheating the boiler combustion air.
• said feeding means comprises then a duct 20 connecting the entrance of the exchanger 5 with the fume duct 101.
• duct 20 must be selectively adjusted and however interdicted/enabled by means of an automatic valve 15 (or equivalent means) arranged along its development thereof.
• the duct 20 then connects, or better is apt to connect, the exchanger 5 with the economizers' area of the combustion system, under negative pressure too with respect to the one of the exchanger 5 itself.
• the air crosses a cyclone dust collector 7 arranged in line onto the duct 20 and apt to discharge said exceeding fine dusts onto the third conveyor 6.
• a valve with double clapet (not illustrated) or an equivalent pressure control means can be installed, for example a differential pressure transmitter measured upstream of and downstream of the entrance to the gravity air/ash exchanger 5 which, upon acting on the valve 15 of the duct 20, brings the pressure difference back to zero.
• the air flow entering the gravitational air/ash exchanger 5, that is in the present example the one fed into the system through the entrances 14 and 17, can be adjusted by the above-mentioned control means based upon the ash temperature and/or quantity detected by the sensors mentioned above, also based upon thresholds which can be set selectively by an operator managing the system 1.
• the additional cooling air entering the gravitational exchanger 5, downstream of thereof and of the possible dust remover 7, follows a path different from the one described by referring to the first embodiment.
• the air instead of being sucked by the depression existing in the fume line 101 of the thermo-electric plant, is sucked by a dedicated fan 16 or by equivalent means along a duct 200 equipped with adjusting means 150 analogous to those already described and then discharged into the atmosphere after having passed through a dedicated filter 9 arranged upstream of the fan 16.
• a fan work is necessary helping the air to cross at first the third conveyor belt 6 and then the gravity air/ash exchanger 5.
• the additional cooling air entering the exchanger 5, upon possible passage into the cyclone 7 mentioned above for the fines' 1 separation, is brought to a system for treating the combustion fumes 104 associated to the boiler 100, by entering the fume duct 101 downstream of the air exchanger (heater) 102 mentioned above.
• the duct of the above-mentioned feeding means has been designated with 201 and the related adjusting means with 151.
• the system 1 has a great operating versatility and therefore the capability of handling even very large flow of ashes and this without the problems associated to the introduction of an excessive cooling air - flow from the bottom of the boiler 100.
• such versatility is obtained by allowing the controlled introduction of even very large quantities of cooling air and feeding the additional cooling air - flow (in particulart the ratio exceeding 1 ,0 - 1 ,5 %of the total combustion air) in the fume duct or outwards since it is not appropriate to introduce said air - flow in the boiler from its bottom.
• the invention has also as object a method for extracting and dry cooling combustion residues as described so far with reference to the system 1.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Gasification And Melting Of Waste (AREA)
• Air Supply (AREA)
• Manufacture And Refinement Of Metals (AREA)

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• 2006
  • 2006-08-22 BR BRPI0621955-1A patent/BRPI0621955A2/pt not_active IP Right Cessation
  • 2006-08-22 US US12/438,125 patent/US20100170425A1/en not_active Abandoned
  • 2006-08-22 AU AU2006347455A patent/AU2006347455A1/en not_active Abandoned
  • 2006-08-22 MX MX2009001890A patent/MX2009001890A/es not_active Application Discontinuation
  • 2006-08-22 CA CA002661623A patent/CA2661623A1/en not_active Abandoned
  • 2006-08-22 EA EA200900335A patent/EA014862B1/ru not_active IP Right Cessation
  • 2006-08-22 EP EP06796268A patent/EP2057415A1/en not_active Withdrawn
  • 2006-08-22 CN CNA2006800556529A patent/CN101506579A/zh active Pending
  • 2006-08-22 JP JP2009525176A patent/JP2010501822A/ja active Pending
  • 2006-08-22 WO PCT/IT2006/000626 patent/WO2008023394A1/en active Application Filing

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