DE10208487A1 - Using superheated hot air heat involves passing heat from hot air to sand in heat exchanger, passing heat from sand to compressed air, and feeding compressed air to turbine combustion chamber - Google Patents

Abstract

A solar tower power plant has a radiation receiver (11) through which air flows and which is mounted on a tower (10) and supplies hot air to a hot air / sand heat exchanger (16). In it, sand is warmed up by heat exchange with the hot air and fed to a hot store (21). The hot storage device (21) is connected to a sand-air heat exchanger (25) in which the sand gives off its heat to air under high pressure. The air thus heated is fed to the combustion chamber (38) of a gas turbine (39).

Description

The invention relates to a method for using the heat highly heated hot air and a solar tower power plant with one high-temperature hot air supplying radiation receiver.

In the older (not prepublished) patent application DE 101 49 806 describes a solar tower power plant. At a Solar tower power plant concentrates a heliostat field made of mirrors, which track the position of the sun, the solar radiation a radiation receiver, which is arranged on a tower. A volumetric radiation receiver consists of one air-permeable porous material with large volume-related Surface in which the concentrated solar radiation is absorbed the material warms up to temperatures that can be above 1000 ° C. Due to the porous material Ambient air sucked, which is correspondingly high Temperatures warmed. Through the convective transmission of the Thermal energy to the heat transfer medium air becomes the receiver material cooled. The hot air is downstream Thermal power process supplied and for example for steam generation used.

One of the difficulties is, from the heated air, which can have a temperature of the order of 1000 ° C, dissipate the heat in such a way that it is technically usable. It are hardly any building materials that can withstand the high air temperatures withstand.

The present invention is based on the object Process for using the heat of superheated hot air specify with which it is possible to heat the superheated air with high efficiency and in technically easy to realizing way to transfer to a heat consumer.

• - Wärmeabgabe von der hocherhitzten Heißluft an rieselfähigen Sand in einem Heißluft-Sand-Wärmetauscher,
• - Wärmeabgabe von dem Sand an unter mindestens 20 bar stehende Druckluft,
• - Zuführen der erwärmten Druckluft zu der Brennkammer einer Gasturbine.

This object is achieved according to the invention with a method of the type specified in claim 1. This method is characterized by the following steps:

• - heat emission from the highly heated hot air to free-flowing sand in a hot air-sand heat exchanger,
• - heat emission from the sand to compressed air under at least 20 bar,
• - supplying the heated compressed air to the combustion chamber of a gas turbine.

Here, the solar-heated sand, which is essentially is depressurized and is at most exposed to a discharge pressure, introduced into a compressed air system. By heating the Compressed air will increase the overall efficiency by 10 to 15% in the case of heating atmospheric air. Except for one There is a significant increase in efficiency Reduction of plant costs due to the lower air volume.

The method according to the invention is based on the fact that initially a heat transfer from the high temperature hot air free-flowing sand takes place. The energy density of sand, quartz sand in particular, is 1000 times higher than that Energy density of the heated air. It follows that the necessary dimensions of the pipes are smaller than at Air transport. By increasing the energy density of hot air too hot sand it is possible that the downstream Components can be cooled, resulting in less expensive designs allows. This is because the specific surfaces decrease in the order of magnitude of the increase in energy density and thus the cooling capacity and thus the energy losses are small become.

The sand is used as a heat energy medium between the superheated uncompressed hot air and compressed air. Quartz sand is incompressible, so when entering it Printing system no compression work needs to be done. The Heat transfer between air and sand is very high and can can be realized technically with low pressure losses.

The use of sand as an energy carrier also enables energy storage, with a hot storage device being provided by storing the heated sand for so long until its warmth is needed.

The invention further relates to a solar tower power plant with a radiation receiver, through which air flows, mounted on a tower, the hot air to a hot air-sand heat exchanger for heating of free-flowing sand. This solar tower power plant exhibits according to the invention a sand-air heat exchanger for the delivery of Heat the heated sand in pressurized air.

In the context of the invention, air is heated under hot air with a temperature of more than 650 ° C, especially more understood as 800 ° C. Under pressurized air or Compressed air is air of more than 20 bar, especially more than 30 bar, preferably more than 40 bar, understood.

In an advantageous development of the invention, that the gas turbine is followed by a waste heat boiler which Feed water of a steam turbine heats up. That way the waste heat of the gas turbine for steam generation within one Coupled steam power process can be used, which from the essential components: waste heat boiler, steam turbine, There is a condenser and feed water pump. However, in the waste heat boiler only part of the preheating of live steam and superheated steam generated for the steam turbine.

The following are with reference to the drawings Embodiments of the invention explained in more detail.

Show it:

Fig. 1 is a schematic diagram of a first embodiment of a solar tower power plant with a downstream gas turbine cycle and steam turbine circuit,

Fig. 2 shows an embodiment of the hot air-sand counterflow heat exchanger, and

Fig. 3 shows another embodiment of the hot air-sand counterflow heat exchanger.

Referring to FIG. 1, the solar tower power plant on a tower 10, on which a radiation receiver 11 is arranged. The radiation receiver 11 consists of a high temperature-resistant material, in particular ceramic, which is porous and thus air-permeable. Solar radiation 12 falls on the radiation receiver and is reflected and bundled onto the radiation receiver by a heliostat field arranged on the earth. The radiation receiver 11 is a thermal absorber which is heated by the solar radiation 12 to temperatures of over 1000 ° C. A fan 13 draws air through a line 14 through the radiation receiver 11 . As a result of the suction effect, cold outside air 15 is sucked into the radiation receiver, where it warms up. The hot air passes through line 14 into a hot air-sand counterflow heat exchanger 16 and leaves it after cooling through line 17 . The air is then blown as cooled air 18 at a temperature higher than that of the outside air 15 in front of the suction surface of the radiation receiver 11 .

The air is fed to the hot air-sand heat exchanger 16 as hot air from below. The hot air rises in the interior of the heat exchanger 16 . A sand line 20 opens into the interior of the hot air-sand heat exchanger 16 , through which cold sand is fed, which sinks in the interior in counterflow to the rising hot air. The hot air gives off its heat to the sand. The sand heated in this way falls into a hot store 21 which is arranged in the lower region of the tower 10 . The hot accumulator 21 is a container which is lined with heat-resistant material and in which the sand is contained at a temperature of, for example, 800 ° C.

The hot sand can be discharged from the hot storage 21 through a sand line 22 to a sand-air heat exchanger 25 which is part of a gas turbine cycle 19 . The sand-air heat exchanger 25 is also a counterflow heat exchanger, in which the sand trickles down under the force of gravity, while air under high pressure rises and thereby takes heat from the hot sand. At the bottom of the sand-air heat exchanger 25 , the sand is removed via a sand line 26 and fed to a fluid bed cooler 27 . The fluid bed cooler contains heat exchanger coils 28 , 29 through which a liquid or vaporous heat transfer medium flows and which form an evaporator or superheater. The sand gives off its remaining heat to these heat exchanger coils. The cold sand is transferred from the sand cooler 27 to a cold store 31 through a sand line 30 , in which cold sand is kept ready at a temperature of, for example, 150 ° C. The outlet 32 of the cold store 31 is connected to the sand line 20 . A conveying device (not shown) for conveying the sand by means of air is contained in the sand line 20 . The sand is thus conveyed in a closed circuit, which contains the hot storage 21 , the cold storage 31 and the hot air-sand heat exchanger 16 .

Pressurized air is fed to the sand-air heat exchanger 25 via a compressed air line 35 , which air was sucked in from the ambient air by a compressor 36 and compressed to a pressure of over 40 bar. The sand-air heat exchanger 25 is under this high air pressure. The compressed air is fed to the heat exchanger from below and leaves it at the top, where it flows in counterflow to the sand that is trickling down and is heated in the process. A deduster 36 in the form of a cyclone is connected downstream of the sand-air heat exchanger. The dust separated from the compressed air is fed to the sand line 26 via a dust line 33 .

The hot compressed air is fed via a compressed air line 37 to the combustion chamber 38 of a gas turbine 39 as combustion air.

The outlet line 40 of the gas turbine 39 is connected to a waste heat boiler 41 . The waste heat boiler 41 is a heat exchanger which emits the residual heat of the gas turbine to a steam turbine circuit 45 which, in a closed circuit, contains a steam turbine 46 , a condenser 47 , a feed water pump 48 and a heating coil 49 belonging to the waste heat boiler 41 .

In the pressure system of the sand-air heat exchanger 25 , the compressed air coming from the compressor 36 is heated in countercurrent to about 800 ° C. by the heated sand. With the pressure level, the specific efficiency of the gas turbine 39 increases and the size of the system decreases. The gas turbine 39 drives a generator (not shown) for generating electrical energy.

The steam generation is optionally distributed between the fluidized bed cooler 27 and the waste heat boiler 41 . In the fluidized bed cooler 27 , the sand is cooled from a temperature level between 400 and 600 ° C. for steam generation to 80 to 150 ° C. before it is fed to the cold store 31 . The fluid bed cooler 27 can either be pressurized or operated without pressure. Accordingly, a pressure lock can alternatively be arranged in front of or behind the fluid bed cooler 27 . The pressure lock causes the sand pipe in question z. B. the sand line 26 is depressurized.

Fig. 2 shows an embodiment of the hot air-sand heat exchanger 16. This has an upright cylindrical housing 51 , which has a funnel-shaped bottom 52 at the bottom, from which a vertical line 53 leads into the upper end of the hot store 21 . The roof 54 of the container 31 contains a cold air collecting space 55 . The hot air line 14 leads into the lower region of the container 51 . In the container 51 there is a horizontal perforated plate 57 for uniform distribution of the rising hot air flow over the entire cross section of the container. The rising hot air gives off its heat to the falling sand and leaves the container as cold air through the upper end of the container. The sand is introduced through the sand line 20 into the upper end of the container 51 and distributed there with sand nozzles from which it drips down. The sand only sinks under gravity in free fall in the container 51 and is guided from the bottom 52 into the hot sand line 53 .

FIG. 3 shows a hot air-sand heat exchanger 16 which has a plurality of inclined baffles 60 in the interior of a cylindrical, vertical housing 51 , which form a cascade consisting of inclined surfaces on which the sand 61 , which is supplied through the sand line 20 , falls. Between two baffles there is a stretch of free fall 62 , in which the sand trickles down. The baffles 60 have such a slope that the sand slides on them. After leaving the last guide plate 60 , the sand falls onto the funnel-shaped bottom 62 from where it is led into the hot sand line 53 . During the descent in the housing 51 , the sand 61 is increasingly heated in countercurrent by the rising hot air.

Claims (6)

1. Procedure for using the heat of superheated hot air, with the steps - Heat emission from the hot air to free-flowing sand in a hot air-sand heat exchanger ( 16 ), - heat emission from the sand to compressed air under at least 20 bar, - Feeding the heated compressed air to the combustion chamber ( 38 ) of a turbine ( 39 ). 2. Solar tower power plant with a mounted on a tower ( 10 ) air-flow radiation receiver ( 11 ), which supplies hot air to a hot air-sand heat exchanger ( 16 ) for heating free-flowing sand, and with a sand-air heat exchanger ( 25 ) for delivery of heat from the heated sand to pressurized air. 3. Solar tower power plant according to claim 2, characterized in that the sand-air heat exchanger ( 25 ) is followed by a deduster ( 36 ). 4. Solar tower power plant according to claim 2 or 3, characterized in that the sand-air heat exchanger ( 25 ) supplies pressurized hot air to a gas turbine ( 39 ). 5. Solar tower power plant according to claim 4, characterized in that the gas turbine ( 39 ) is followed by a waste heat boiler ( 41 ) that heats the feed water of a steam turbine ( 46 ). 6. Solar tower power plant according to one of claims 2-5, characterized in that the sand-air heat exchanger ( 25 ) is connected in series with a fluid bed cooler ( 27 ).