PROCESS FOR HEAT EXTRACTION AND POWER PRODUCTION WITH HEAT RECOVERY

Abstract: Process for heat extraction and power production with heat recovery, whereby any kind of heat is supplied to a boiler (1) for transfer to a steam circuit (14), via a heat exchange medium, which is introduced in a first medium circuit (7) to at least one heat exchanger (5, 21), where heat exchange to the steam circuit is effected, whereby the first medium circuit (7) consists of a hot oil circuit, in which the oil admits effective heat exchange without simultaneous pressure increase.

Description: PROCESS FOR HEAT EXTRACTION AND POWER PRODUCTION WITH HEAT RECOVERY The present invention relates to a process for heat extraction and power production with heat recovery. The object of the proposed process is to generate in a simple and effective manner optional proportions of electric power and heat by means of a heating boiler built as simply as possible, and where the dimensions of the components incorporated in a plant can be kept small. For different reasons hot-water boilers in later years have been built, which are substantially cheaper than corresponding boilers for production of steam. With increased desire for production of steam for steam power production with turbine, the need to replace or rebuild earlier boilers for generation of hot water also increases. This in order to produce steam e.g. for steam turbine or steam engine and also heat from the condensate. A rebuilding of the earlier hot water boilers to steam boilers is expensive and for that reason a process is proposed according to the present invention which means that the objects above given can be reached and this has been achieved in giving the process the characteristics given in claim 1. The invention will be further explained in the following with reference to schematical coupling diagrams shown in the accompanying drawings. In Fig. 1 is schematically shown an embodiment in form of a coupling diagram for a system suitable for accomplishment of the process according to the invention, Fig. 2 is a corresponding view of an alternative embodiment of a system for accomplishment of the process according to the invention, Fig. 3 is a section view of an alternative embodiment of a in the system including boiler vessel for increasing the pressure of steam according to Fig.l or 2, at higher temperatures and with direct superheating of the steam in the combustion gas, and Fig. 4 shows in a schematic view how the process according to the invention can be used for heat recovery in a regenerative process. The system shown in Fig. 1 comprises a substantially conventional boiler 1, in the figure illustrated as a wood fired boiler, but that represents any boiler to which air is supplied via the duct 2, and where fuel is supplied at 3, and hot flue gases vanish via the duct 4 to a first heat exchanger, from which the cooled flue gases vanish into atmosphere or to other, not further shown part of the process. Through the boiler 1 is also led a coil 6 of a first heat exchanger circuit 7, which is connected to a boiler vessel 8 and a superheater 9. The boiler vessel 8 as well as the superheater 9 are connected to this first heat exchanger circuit 7 via separate parts of conduits provided with separate control devices 10 and 11 respectively, to allow controlling of the heat transfer to the boiler vessel and the superheater in a correct and stepless way. After the boiler vessel 8 and the superheater 9 the outgoing flows of medium are again combined to a common conduit and are brought back to the boiler 1. So far the system mainly corresponds to earlier systems, but oil is used instead of working with hot water in the first heat exchanger circuit 7, which means that the heat content of the hot oil is considerably higher when it leaves the boiler than what normally can be achieved with hot water circuits. Via a throttling device 12 an economizer 13 is also connected in the circuit 7 and the output thereof leads via the heat exchanger 5 back to the boiler 1. A hot water circuit 14 is then connected to the superheater 9, the boiler vessel 8 and the economizer 13 and it is via a pipe suppling steam on one hand to a turbine 15 for power production, and on the other hand to a condenser for heat production. Apart from that the shown hot water circuit or steam circuit can be made more compact it is otherwise quite conventional, and has a bypass line 17 arranged to make it possible to direct more steam to the condenser 16 for producing more heat or to be able to produce heat when the turbine is shut down. The process that is operated in the system in question is in principle a conventional steam process with the difference that heat transfer between the boiler and the steam circuit is done via at least one hot oil circuit. A great advantage with this is that the boiler 1 can be constructed in a zero-pressure embodiment, it has no fire influenced pressure parts, and the heat transfer to the steam circuit 14 is instead transferred to at least one component separated from the boiler and operating as heat exchanger e.g. the first heat exchanger 5, the superheater 9, the boiler vessel 8 and the economizer 13. These heat exchanging components are to be subjected to the pressure difference between atmosphere pressure and process pressure, which is advantageous, as these external heat exchangers can be built with considerable smaller dimensions than the boiler, which means that the total surface all together subjected to pressure can be considerable reduced. The adjustment of the temperatures in the superheaters can be controlled via the control of the flows of oil in the first and/or the second hot oil circuit. In Fig. 2 is shown an alternative embodiment of the system 2 according to Fig. 1, at which the only real difference is that a second hot oil circuit 18 is arranged between the economizer 13 and the first heat exchanger 5, whereby the heat that is supplied to the economizer 13 causes the water in the steam circuit to be preheated before it is introduced in the boiler vessel. The mass flow in the secondary oil circuit is approximately 1.7 times bigger than the steam flow. In Fig. 3 is illustrated in a simplified view how it is possible by introducing hot oil in a economizer 13, via a hot oil circuit 20, that (not shown) can be connected to a boiler 1 according to Fig. 1 , to produce a saturated steam with a temperature of approximately 300°C, after which the saturated steam is introduced into the superheater 9, where the saturated steam is superheated to approximately 475 °C, with aid of hot flue gases 19 of a temperature of approximately 600°C, but which temperature can be higher. At a plant of this kind without the direct superheating, there are at a saturated steam of 300°C and 90 bar, very small margins left over for superheating, whereas it is possible by use of further hot oil circuit, to increase the steam pressure right up to 150 to 160 bar, but it is from a practical point of view suitable to use a primary pressure of 90 to 120 bar and after that perhaps to superheat the saturated steam up to the level 475 -520°C with aid of combustion gases 19. In Fig. 4 is shown a system for heat recovery or gas purification known per se and with heat recovery by means of a regenerative process where heat is supplied at 21 to two chambers 22, 23, that e.g. contain a ceramic material and via a valve system 24, 25 alternatively are connected to the heating and to the heated medium. Also in that kind of system it is possible to bring about a regenerative heat exchange, by incorporating at least one steam coil 26 and one hot oil coil 27 furnished with a pump 28 and a boiler 29, that substantially correspond to the boiler vessel 8 and possibly also the economizer 13 according to Fig.l, whereby the superheated steam leaves the conduit 26 and is utilized for heat and/or power production, in much the same way as in the embodiments according to Fig.l or 2, whereby surplus energy can be extracted by means of the heat exchange based on oil. This type of system can very well be used in regenerative thermic combusition or oxidation e.g. in connection with diluted methane containing compounds, such as e.g. deposit gases or ventilated mine gas. It is possible to generate in a simple and effective way optional proportions of electrical power and heat with the described processes at a very high efficiency and with a production system which can be simplified, as a consequence of the use of hot oil instead of hot water or hot steam in at least one of the heat exchange circuits, and which therefor permits that a boiler included therein can be built for zero-pressure operation, at the same time as it has been possible to dimension the rest of the components of the system in an advantageous way. However the invention is not limited to the illustrated embodiments, but variants and modifications are also possible within the scope of the claims.

Claims: CLAIMS 1. Process for heat extraction and power production with heat recovery, whereby any kind of heat is supplied to a boiler (1, 19, 22, 23) for transfer to a steam circuit (14, 22, 26), via a heat exchange medium, which is introduced in a first medium circuit (7, 20, 27) to at least one heat exchanger (5, 21, 29), where heat exchange to the steam circuit is effected, characterized in that, the first medium circuit (7, 20, 27) consists of a hot oil circuit, in which the oil admits effective heat exchange without simultaneous pressure increase. 2. Process according to claim 1, characterized in that, heat is generated in a boiler (1) in which heat exchange is effected against the hot oil circuit (7) recirculated through the boiler, which circuit in a separate exchanger (8, 13) converts water into a flow of saturated water steam. 3. Process according to claim 2, characterized in that, the saturated water steam is returned into a heat exchanger (9) via a steam circuit and there is superheated, from where the steam thus superheated is led away for power and/or heat generation. 4. Process according to claim 1, characterized in that, a heat carrying medium in a first heat exchanger (5) transfers heat into a first hot oil circuit (7), which via a boiler vessel (8) and a superheater (9) transfers heat to a hot water or steam circuit (14), which in turn is connectable to a power producing machine (15) and to a heat producing device (16). 5. Process according to claim 4, characterized in that, a second hot oil circuit (12) is arranged to be heated and via an economizer (13) to preheat the water in the hot water circuit (14) before it is introduced into the boiler vessel (8). 6. Process according to claim 4 or 5, characterized in that, the first hot oil conduct (7) is bifurcated in two branch conduits, which are connected to boiler vessel (8) and superheater (9) respectively, whereby the branch conduits have controllable flow regulating valves for individual adjustment of the proportions of the supplied hot oil to the boiler vessel and the superheater respectively, and which branch conduits are returned to the boiler (1) after boiler vessel and superheater respectively. 7. Process according to any of the preceding claims, characterized in that, the process is conducted in a plant for regenerative heat recovery, where at least in one heat chamber (22, 23) is positioned at least one hot oil coil (27), for extraction of surplus energy from primarily methaneous compounds with proportionately low heat content, for instance deposit gas and ventilated mine gas. AMENDED CLAIMS [received by the International Bureau on 13 November 2001 (13.11.01); original claims 1-7 replaced by new claims 1-5 (2 pages)] CLAIMS 1. Process for heat extraction and power production with heat recovery, for generating optional proportions of electric power and heat, with heat from a boiler (1, 19, 22, 23) for transfer to a steam circuit (14, 22, 26), via a heat exchange medium, which is introduced in a first medium circuit (7, 20, 27) to at least one heat exchanger (5, 21, 29), where heat exchange to the steam circuit is effected, characterized in that, the first medium circuit (1, 20, 27) consists of a hot oil circuit, in which the oil admits effective heat exchange without simultaneous pressure increase, whereby in the boiler (1) heat exchange is effected against the hot oil circuit (7) recirculated through the boiler, and which circuit in a separate exchanger (8, 13) converts water into a flow of saturated water steam, and that a heat carrying medium in a first heat exchanger (5) transfers heat into a first hot oil circuit (7), which via a boiler vessel (8) and a superheater (9) transfers heat to a hot water or steam circuit (14), which in turn is connectable to a power producing machine (15) and to a heat producing device (16).which in a . 2. Process according to claim 1, characterized in that, the saturated water steam is returned into a heat exchanger (9) via a steam circuit and there is superheated, from where the steam thus superheated is led away for power and/or heat generation. 3. Process according to claim 1, characterized in that, a second hot oil circuit (12) is arranged to be heated and via an economizer (13) to preheat the water in the hot water circuit (14) before it is introduced into the boiler vessel (8). 4. Process according to claim 3, characterized in that, the first hot oil conduct (7) is bifurcated in two branch conduits, which are connected to boiler vessel (8) and superheater (9) respectively, whereby the branch conduits have controllable flow regulating valves for individual adjustment of the proportions of the supplied hot oil to the boiler vessel and the superheater respectively, and which branch conduits are returned to the boiler (1) after boiler vessel and superheater respectively. 5. Process according to any of the preceding claims, characterized in that, the process is conducted in a plant for regenerative heat recovery, where at least in one heat chamber (22, 23) is positioned at least one hot oil coil (27), for extraction of surplus energy from primarily methaneous compounds with proportionately low heat content, for instance deposit gas and ventilated mine gas.

Inventors: KULLENDORFF ANDERS, KULLENDORFF, ANDERS
Applicants: KULLENDORFF ANDERS, KULLENDORFF, ANDERS
Application year: 2001
Main classification: F22B1
IPC codes: F22B1