OPTIMIZED PROCESS AND SYSTEM FOR THE PRODUCTION OF A HEATED FLUID BY MEANS OF COMBUSTION OF A FUEL

Abstract

An optimized process and system for the production of a heat exchange fluid heated by means of combustion of a fuel are described, said process comprising the steps of: burning a fuel in a combustion chamber, thus generating a flow of exhaust gas, said flow comprising solid particulate matter and/or combusted or uncombusted particles; introducing said flow of exhaust gas into a unit suitable for the forced abatement of the solid particulate matter and/or combusted and uncombusted particles, thus obtaining a purified exhaust gas flow and a solid precipitate which comprises solid particulate matter; transferring the flow of purified gas to a generator of a heated heat exchange fluid, inside which a heat exchange fluid flows; carrying out an indirect heat exchange, thus obtaining a flow of cooled purified exhaust gas and a heated heat exchange fluid.

Claims

1-15. (canceled)

16. A process for the production of a heat exchange fluid heated by the combustion of a fuel, said process comprising the steps of: a) burning said fuel in a furnace which comprises a combustion chamber, thus generating a flow of exhaust gas comprising suspended solid particulate matter; b) transferring said flow of exhaust gas to at least one cyclone, which is located outside said combustion chamber; c) subjecting said flow of exhaust gas to a forced abatement of said solid particulate matter inside said at least one cyclone, thus obtaining a purified exhaust gas flow and a solid precipitate which comprises said solid particulate matter; d) transferring said purified exhaust gas flow to a heat exchange unit inside which a heat exchange fluid flows; and e) carrying out an indirect heat exchange between said purified exhaust gas flow and said heat exchange fluid, thus obtaining a flow of cooled purified gas and a heated heat exchange fluid.

17. The process according to claim 16, wherein said steps a-d are carried out in adiabatic conditions.

18. The process according to claim 16, wherein said exhaust gas flow and said purified exhaust gas flow have a temperature higher than 300 C.

19. The process according to claim 16, wherein said steps b) and c) are carried out by means of at least two cyclones.

20. The process according to claim 16, wherein said steps b) and c) are carried out by means of a multi-cyclone.

21. The process according to claim 16, said process comprising the steps of: transferring said cooled exhaust gas flow to a pre-heater to generate a flow of heated air; transferring to said furnace and feeding to the combustion chamber of said furnace said flow of heated air, as a flow of combustive air.

22. The process according to claim 16, said process comprising a further step of transferring said heated heat exchange fluid from said heat exchange unit to a system for the generation of electricity.

23. A system for the production of a heat exchange fluid heated by the combustion of a fuel, said process comprising the following units: a furnace comprising a combustion chamber suitable for the combustion of a fuel with generation of an exhaust gas comprising suspended solid particulate matter; at least one cyclone in fluid communication with said furnace for the abatement of said suspended solid particulate matter, wherein said at least one cyclone comprises a upper part, comprising an inlet opening for the entry of said gas flow from said furnace and an outlet opening for the exit of a purified gas flow, and a bottom part, comprising a hopper for the collection of precipitated solid particulate matter; a generator of a heated heat exchange fluid, in fluid communication with said at least one cyclone for receiving said purified gas flow and arranged downstream with respect to said at least one cyclone, wherein said generator of a heated heat exchange fluid comprises a heat exchange zone, in which a heat exchange unit is located, and a discharge opening for the exit of a cooled exhaust gas flow.

24. The system according to claim 23, wherein said at least one cyclone consists of at least two cyclones.

25. The system according to claim 23, wherein said at least one cyclone consists of a multi-cyclone.

26. The system according to claim 23, wherein said system further comprises the following units: an additional generator of a heated heat exchange fluid, in fluid communication with said discharge opening, for receiving said purified gas flow, wherein said additional generator of a heated heat exchange fluid comprises an additional heat exchange zone, in which an additional heat exchange unit is located, and an additional discharge opening for the exit of a further cooled exhaust gas flow.

27. The system according to claim 23, wherein said furnace comprises an inlet mouth of said combustion chamber for the supply of fuel into said combustion chamber, and an opening for the introduction of a flow of combustive air into said combustion chamber.

28. The system according to claim 27, wherein said system further comprises the following units: a pre-heater in fluid communication with said discharge opening or with said additional discharge opening for the exit of a cooled exhaust gas flow from said generator or from said additional generator of a heated heat exchange fluid, wherein said pre-heater is capable to receive said cooled exhaust gas flow and to generate a flow of heated air; a header in fluid communication with said pre-heater and with said opening for the introduction of a flow of combustive air into said combustion chamber, wherein said header is capable to transfer said flow of heated air to said opening for a flow of air, as a flow of combustive air.

29. The system according to claim 23, wherein said heat exchange fluid is water or a diathermic oil.

30. The system according to claim 23, wherein said system further comprises an inlet pipe for transferring said heat exchange fluid to said heat exchange unit or to said additional heat exchange unit, and an outlet pipe for transferring said heated heat exchange fluid from said heat exchange unit or from said additional heat exchange unit to a system for the generation of electricity or to a utility in industrial or civil applications.

31. The process according to claim 18, wherein said temperature is higher than 400 C.

32. The process according to claim 19, wherein said at least two cyclones operate in parallel.

33. The system according to claim 23, wherein said heat exchange unit is a conventional heat exchanger.

34. The system according to claim 24, wherein said at least two cyclones are arranged in parallel.

35. The system according to claim 26, wherein said additional heat exchange unit is a conventional heat exchanger.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0072] FIG. 1 shows in schematic form a system for the production of a heat exchange fluid heated by means of combustion of a fuel according to the present invention.

[0073] FIG. 2 shows in schematic form a different embodiment of system for the production of a heat exchange fluid heated by means of combustion of a fuel according to the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0074] FIG. 1 shows a system, denoted overall by 1, for the production of a heated heat exchange fluid by means of combustion of a fuel comprising a furnace 2, a cyclone 10 downstream of said furnace and a generator of a heated heat exchange fluid 20, downstream of the cyclone 10.

[0075] The furnace 2 comprises in turn a combustion chamber 4 and an inlet mouth 3 of the combustion chamber which is structured so as to facilitate the introduction of fuel into the combustion chamber.

[0076] Furthermore, the combustion chamber 4 comprises in turn a combustion zone and an opening 7 for the introduction of an air flow into the combustion chamber 4.

[0077] The combustion chamber 4 may have, situated inside it, an igniting system, preferably a grate-type igniter, which is capable to ensure distribution of the fuel and on which ignition of the fuel takes place; this igniting system is not shown since it is entirely conventional.

[0078] The combustion chamber also comprises a zone 5 for conveying the flow of exhaust gas which is generated following the combustion of the fuel, this conveying zone 5 being situated above the combustion zone 4 and being formed so as to convey said flow towards an outlet opening 6 for transferring the exhaust gas flow to the cyclone 10 situated downstream of the combustion chamber 4 and in fluid communication therewith.

[0079] The cyclone 10 is a cyclone for abatement of suspended solid material transported by a gas flow. The cyclone 10 has substantially the form of an overturned cone and is formed so as to have a upper part 11 which has a cross-section with a predefined diameter; this upper part 11 comprises an entry opening 12 for the exhaust gas flow, an internal cylinder for conveying an exhaust gas flow purified upon exiting the cyclone 10 (not shown since entirely conventional) and an outlet opening 18 for exit of the purified exhaust gas flow and transferring said flow to a generator 20 of a heated heat exchange fluid, situated downstream of and in fluid communication with the cyclone 10.

[0080] The cyclone 10 also comprises a bottom part 13 situated underneath the upper part 11; this bottom part 13 has a cross-section with a smaller diameter than the upper part 11. Moreover, the bottom part 13 comprises in turn a hopper 14 shaped so as to facilitate the sliding and collection of the precipitated solid material from the upper part 11.

[0081] The generator 20 of a heated heat exchange fluid, arranged downstream with respect to the cyclone 10 as evident from the drawings, comprises in particular an inlet opening 21 for the introduction of the purified exhaust gas flow into a heat exchange zone 22, the latter in turn comprising a heat exchange unit 23, inside which a heat exchange fluidpreferably water or diathermic oilflows, and a discharge opening 24 for the exit of a cooled exhaust gas flow.

[0082] Preferably, the heat exchange unit 23 is a conventional heat exchanger.

[0083] In an equally preferable manner, the system 1 according to the present invention may further comprise an inlet pipe 29 for transferring a heat exchange fluid to the heat exchange unit and in fluid communication therewith.

[0084] In a similar manner, said system 1 may further comprise an outlet pipe 28, in fluid communication with the heat exchange unit 23, for transferring the heated heat exchange fluid, preferably heated diathermic oil or steam, from the heat exchange unit 23 to a system for the generation of electricity, not shown since entirely conventional, or to a utility in an industrial or civil application.

[0085] Differently, FIG. 2 shows a particular embodiment according to the present invention in which the system 1 further comprises an additional generator 40 of a heated heat exchange fluid in fluid communication with the aforementioned discharge opening 24.

[0086] The additional generator 40 is capable to receive this cooled exhaust gas flow and comprises in turn an inlet mouth 31 and a heat exchange zone 41 in which there is located an additional heat exchange unit 38 inside which a heat exchange fluid flows, and an additional discharge opening 39 for the exit of a further cooled exhaust gas flow.

[0087] Correspondingly, said system 1 shown in FIG. 2 may further comprise an outlet pipe 37, in fluid communication with the additional heat exchange unit 23, for transferring the heated heat exchange fluid, preferably heated diathermic oil or steam, from the additional heat exchange unit 23 to a system for the generation of electricity, not shown since entirely conventional, or to a utility in an industrial or civil application.

[0088] Moreover, the embodiment shown in FIG. 2 shows a pre-heater 30 in fluid communication with the discharge opening 39 of the additional generator 40 and able to receive the cooled exhaust gas flow and generate a flow of heated air to be transferred to the combustion chamber 4 of the furnace 2.

[0089] More specifically, the pre-heater 30 communicates with a header 35 in fluid communication with the opening 7 for the introduction of an air flow into the combustion chamber 4.

[0090] Moreover, the pre-heater 30 also has a discharge opening 31 for releasing the cooled exhaust gas flow downstream of the system.

[0091] Operation of the system according to the present invention may be further explained as follows, with reference to a non-limiting embodiment.

[0092] The fuel is introduced into the furnace 2, then the fuel is ignited, generating an exhaust gas flow containing suspended solid particulate matter which is transferred to a pair of cyclones 10, which can be arranged in parallel, where a centrifugal force is imparted and a downwards spiral movement is induced.

[0093] The flow charged with suspended solid material thus undergoes an abatement step with consequent precipitation of these solids suspended in and transported by the flow.

[0094] Thereafter, the purified exhaust gas flow thus generated and output from the cyclones is transferred to a unit 20 for generating a heated heat exchange fluid (specifically, a steam generator) located downstream of the pair of cyclones 10.

[0095] More specifically, the unit 20 used for generating a heated heat exchange fluid comprises a series of tube heat exchangers 23 inside which water from aqueduct circulates. Following the indirect heat exchange performed between the purified exhaust gas flow and the water circulating inside the pipes of the heat exchanger a steam flow and a cooled exhaust gas flow are produced.

[0096] A check carried out inside the steam generating unit 20 confirmed that the outer surface of the pipes of the superheating units was substantially intact and that there was no significant deposition of solid material thereon.

[0097] Thanks to the process according to the present invention and the system described above in detail it is possible to overcome the problems of the prior art, as mentioned above, preventing first and foremost the transmission of suspended solid particulate matter and dust, generated during combustion and transported by the exhaust gas flow to the heat exchange units situated in the unit for generating a heated heat exchange fluid.

[0098] In fact, according to the present invention, it is possible to obtain this technical advantage owing to an abatement step performed by means of at least one cyclone arranged between a furnace, inside which a combustion step is carried out, and a unit for generating a heated heat exchange fluid, inside which an indirect heat exchange between this gas flow and a heat exchange fluid occurs.

[0099] This abatement step carried out by means of at least one cyclone, compared to a conventional abatement chamber, gives rise to numerous technical advantages including: [0100] shorter maintenance stoppage times; indeed long and excessively frequent emptying of the zone for storage of the precipitated solid material is not required, since the at least one cyclone allows constant expulsion of said material, without a general stoppage of the system; [0101] the exhaust gas flow entering the at least one cyclone has a speed which is entirely comparable to the speed of a purified exhaust gas flow exiting the same unit, thus ensuring faster response times and a greater throughput; [0102] more efficient and improved abatement resulting in an exhaust gas flow which is purified compared to the gas flow entering the at least one cyclone.

[0103] Furthermore, with the process and the system according to the present invention it is possible to obtain decidedly higher temperatures compared to the similar processes and systems present on the market; indeed, since the exhaust gas flow entering the unit for generating a heated heat exchange fluidwhich contains an entirely negligible amount of suspended solidsmay be transferred to the heat exchange units which are situated in said unit for generating a heated heat exchange fluid, there is no risk that, during the life cycle of the system, the high-temperature ash may adhere massively to the pipes of the heat exchange units.