DE102011086223A1 - Heat transfer medium circuit with overflow tank, method for transporting heat transfer medium by means of the heat transfer medium circuit and use of the heat transfer medium circuit - Google Patents

Abstract

The invention relates to a heat transfer medium circuit with at least one heat transfer medium transport cycle for the transport of heat transfer medium and at least one heat transfer medium overflow circuit for the exchange of heat transfer medium with the heat transfer medium transport cycle. The heat transfer medium overflow circuit has at least one overflow container which can be activated as a function of an activation value of at least one operating parameter of the heat transfer medium circuit, so that the overflow container for the exchange of heat transfer medium between the heat transfer medium overflow circuit and the heat transfer medium transport Cycle is available. Likewise, a method for transporting heat transfer medium by means of the heat transfer medium circuit is specified, wherein the overflow tank is activated in dependence on the activation value of the operating parameter, so that the exchange of heat transfer medium between the heat transfer medium overflow circuit and the heat transfer medium transport cycle with the help the overflow container takes place. When the activation value of the operating parameter is reached, the overflow tank is connected to the heat transfer medium overflow circuit. The heat transfer medium is preferably a thermal oil. Use finds the heat transfer medium cycle in a solar thermal power plant for the production of electrical energy.

Description

The invention relates to a heat transfer medium circuit with overflow tank and a method for transporting heat transfer medium by means of the heat transfer medium circuit. In addition, a use of the heat transfer medium cycle is specified.

In solar thermal power plants, e.g. Solar thermal parabolic trough power plants, the radiation energy of the sun with the aid of a heat transfer fluid (HTF) and a conventional steam process is converted into electrical energy. As heat transfer media thermal oils or molten salts are used.

By starting and stopping the solar thermal power plant, a volume of the heat transfer medium varies by up to 30%, in particular in the case of thermal oils.

In order to compensate for the variation in the volume of the heat transfer medium, permanently opened overflow vessels (overflow vessels) are present. These overflow containers are subject to high requirements such as temperature and pressure resistance. In addition, these overflow containers are dimensioned such that an entire expansion volume of the heat transfer medium can be accommodated. Overall, therefore, the overflow container is a significant cost factor of a solar thermal power plant.

The object of the invention is to show how a heat transfer medium cycle is to be designed so that the expansion volume of a heat transfer medium can be compensated cost-effectively, that is, absorbed or released.

The object is solved by the independent claims. Embodiments of the invention can be found in the dependent claims.

To solve the problem, a heat transfer medium circuit with at least one heat transfer medium transport cycle for transporting heat transfer medium and at least one heat transfer medium overflow circuit for exchanging heat transfer medium with the heat transfer medium transport cycle is specified. The heat transfer medium overflow circuit has at least one overflow container which can be activated as a function of an activation value of at least one operating parameter of the heat transfer medium circuit, so that the overflow container for the exchange of heat transfer medium between the heat transfer medium overflow circuit and the heat transfer medium transport Cycle is available. The heat transfer medium has at least one substance selected from the group of thermal oil and molten salt.

To solve the problem, a method for transporting heat transfer medium by means of the heat transfer medium circuit is specified, wherein the overflow tank is activated in dependence on the activation value of the operating parameter, so that the exchange of heat transfer medium between the heat transfer medium overflow circuit and the heat transfer medium transport -Circulation using the overflow tank takes place. When the activation value of the operating parameter is reached, the overflow tank is connected to the heat transfer medium overflow circuit.

According to a further aspect of the invention, a use of the heat transfer medium circuit is specified in a solar thermal power plant. It transported with the help of the heat transfer medium circulation heat transfer medium for the production of electrical energy. In this use of the heat transfer medium circuit, the thermal energy absorbed by the heat transfer medium is used to generate water vapor via a heat exchanger. With the help of water vapor, a steam turbine is driven to generate electric power. Other applications of the heat transfer circuit are also conceivable, for example, the use of the heat transfer medium circuit for receiving waste heat from an industrial process by the heat transfer medium.

The heat transfer medium transport cycle and the heat transfer medium overflow circuit are heat transfer medium partial circuits of the heat transfer medium circuit. The heat transfer medium partial circuits are coupled to one another such that the exchange of heat transfer medium between the heat transfer medium partial circuits can take place. The exchange of heat transfer medium between the heat transfer medium transport cycle and the heat transfer medium overflow cycle comprises a recording of heat transfer medium of the heat transfer medium transport cycle through the heat transfer medium overflow circuit and a discharge of heat transfer medium to the heat transfer medium transport cycle the heat transfer medium overflow cycle. In this case, only a single overflow container can be provided. Preferably, a plurality of such overflow containers are connected in parallel or in series.

The overflow container can be switched on depending on the activation value of the operating parameter (eg pressure and / or temperature of the heat transfer medium in the heat transfer medium transport cycle) and thus for the exchange process described are available. Likewise, the overflow container can be separated depending on the activation value of the heat transfer medium overflow circuit and thus are not available for the exchange process described. This makes it possible to design the overflow container such that it satisfies the requirements of the respective values of the operating parameter or of the operating parameters.

According to a particular embodiment, the heat transfer medium overflow circuit on at least one further overflow container, which can be activated in response to a different activation value of the operating parameter of the heat transfer medium circuit different activation value of the operating parameter of the heat transfer medium circuit, so that the further overflow container for the Exchange of heat transfer medium between the heat transfer medium overflow circuit and the heat transfer medium transport cycle is available. The overflow tank and the further overflow tank are separated from each other.

The same applies to the further overflow tank as to the overflow tank: only a single further overflow tank can be provided. Preferably, a plurality of such further overflow containers connected in parallel or in series are present.

During an installation operation of the solar thermal power plant, e.g. a parabolic trough power plant, basically two types of standstill and the resulting two different operating volumes of the heat transfer medium are to be distinguished: When using a thermal oil resulting from the daily arrival and departure a fluctuation of about 10%. This fluctuation is called "hot" oil volume. In contrast, in the case of prolonged stoppage of the equipment, e.g. Unscheduled maintenance downtime, a variation of approx. 20% to ("cold" oil volume).

When starting up the system, in the first case the "hot" oil volume and in the second case the "cold" oil volume must be led back from the heat transfer medium overflow circuit back into the heat transfer medium transport cycle.

The thermal oil in the heat transfer medium overflow circuit is usually placed under an inert gas pressure. The inert gas is, for example, nitrogen. A standstill pressure of the heat transfer medium overflow circuit is in the case of the "cold" oil volume well below the actual operating pressure in the heat transfer medium transport cycle. For this reason, it is not necessary for the return of the heat transfer medium from the overflow tank of the heat transfer medium overflow circuit in the heat transfer medium transport cycle to provide the corresponding expansion volume ("cold" oil volume) under the same pressure as in the operating case prevails in the heat transfer medium transport cycle. The inert gas pressure is comparatively low. In contrast, the "hot" oil volume for returning to the heat transfer medium transport cycle must be placed under the comparatively high pressure of the heat transfer medium transport cycle.

Preferably, the overflow containers can be activated or deactivated independently of each other. A coupling of the activation of the overflow tank or the coupling of the deactivation of the overflow tank is also possible. So one of the overflow tank can be activated and at the same time the other overflow tank deactivated.

In a particular embodiment, the heat transfer medium overflow circuit has at least one separating device for separating the overflow container from the heat transfer medium overflow circuit and / or for separating the further overflow container from the heat transfer medium overflow circuit. The separator is for example a shut-off valve. With the help of the separator ensures that heat transfer medium is not uncontrolled or unintentionally gets into an overflow tank. This is particularly important when the overflow tank is designed for lower demands (lower temperature and lower pressure of the heat transfer medium) and must be prevented that hot heat transfer medium enters this overflow tank.

The operating parameter may be a heat transfer medium pressure, below which the heat transfer medium is in the heat transfer medium transport cycle. In a particular embodiment, the operating parameter is a heat transfer medium temperature of the heat transfer medium of the heat transfer medium circuit. As an operating parameter, the heat transfer medium temperature of the heat transfer medium of the heat transfer medium circuit is used.

Preferably, the overflow tank is a low temperature overflow tank. The activation value is below a predetermined separation temperature. The further overflow tank, however, is a high-temperature overflow tank. The further activation value is above the predetermined separation temperature. If the heat carrier temperature is below the separation temperature, the overflow container is activated for the reception or discharge of heat transfer medium. On the other hand, is the heat transfer temperature above the Separation temperature of the further overflow tank is activated for receiving or delivering heat transfer medium. By this separation, it is possible to design the "cold" overflow tank with a much lower design pressure and a much lower design temperature and thus to save considerable investment costs. In addition, the entire receiving volume of the overflow container can be reduced by the thus achieved lower heat transfer medium mean temperature in the system, resulting in a further reduction of investment costs.

The separation temperature is preferably selected from the range of 150 ° C to 300 ° C. For example, the separation temperature is 240 ° C. A separation temperature of below 150 ° C or above 300 ° C is also conceivable.

The heat transfer medium has at least one substance selected from the group of thermal oil and molten salt. The molten salt has, for example, a salt mixture of various nitrates. In particular in connection with the use of thermal oils, the presented heat transfer medium cycle is advantageous because of the considerable volume changes of the thermal oils.

Reference to an embodiment and the associated figure, the invention will be described in more detail below. The figure is schematic and does not represent a true to scale illustration.

1 shows an embodiment of a solar thermal power plant with a heat transfer medium circuit.

2 shows a second embodiment of a solar thermal power plant with a heat transfer medium circuit.

The solar thermal power plant 1000 is a parabolic trough power plant. It is a heat transfer medium cycle 1 with a heat transfer medium transport cycle 11 for the transport of heat transfer medium 2 available ( 1 and 2 ). The heat transfer medium is a thermal oil. In an alternative embodiment, the heat transfer medium is a molten salt.

Other components of the heat transfer transport circuit are a thermal storage 112 , a steam generator 113 and a heater 114 , In addition, there are pumps 115 available.

The heat transfer medium takes in the solar field 111 solar energy and converts it into thermal energy. About the heat transfer medium, this thermal energy using the heat transfer medium transport cycle to the steam generator 113 transported. There is generated by means of thermal energy in the heat transfer medium water vapor, which is used to operate a steam turbine.

With the heat transfer medium transport cycle 11 is a heat transfer medium overflow cycle 12 for the exchange of heat transfer medium with the heat transfer medium transport cycle 11 coupled. The coupling takes place via the expansion tank 3 ,

The heat transfer medium overflow cycle 12 has several, in series or parallel connected overflow tank (low temperature overflow tank) 121 on ( 1 ). Alternatively, these overflow containers are connected in parallel ( 2 ). These can be dependent on an activation value of an operating parameter of the heat transfer medium cycle 1 to be activated. In one embodiment, the operating parameter is the heat transfer medium temperature in the heat transfer transport cycle 11 , Additionally or alternatively, the operating medium used is the heat transfer medium pressure in the heat transfer medium transport cycle.

In addition, the heat transfer medium overflow cycle 12 several, in series ( 1 ) or parallel ( 2 ) connected further overflow tank (high temperature overflow tank) 122 on. These may depend on a further activation value of an operating parameter of the heat transfer medium cycle 1 to be activated.

Other components of the heat transfer medium overflow circuit are pumps 123 to support the transport of heat transfer medium in the heat transfer medium overflow circuit. In addition, in front of the series connected overflow tank 121 Shut-off valves (separators) 124 , with the help of which the overflow tank 121 can be decoupled from the heat transfer medium overflow circuit. Likewise, further shut-off valves 125 alternatively (eg 2 ) or additionally provided, with the help of which the high-temperature overflow tank 122 from the heat transfer medium overflow cycle 11 can be separated.

The activation value for the overflow tanks 121 is below a predetermined separation temperature of about 240 ° C. When the heat transfer medium temperature is below the separation temperature, the overflow tanks become 121 activated for the reception or delivery of heat transfer medium. These are shut-off valves 124 available. If, on the other hand, the heat transfer medium temperature is above the separation temperature, the shut-off valves will become 124 closed. Only the other overflow tanks (high temperature overflow tank) 122 are available for the exchange of heat transfer medium with the heat transfer medium transport cycle.

Claims (13)

Heat transfer medium cycle ( 1 ) with - at least one heat transfer medium transport cycle ( 11 ) for the transport of heat transfer medium and - at least one heat transfer medium overflow circuit ( 12 ) for the exchange of heat transfer medium with the heat transfer medium transport cycle ( 11 ), wherein - the heat transfer medium overflow circuit ( 12 ) at least one overflow container ( 121 ), which in dependence on an activation value of at least one operating parameter of the heat transfer medium circuit ( 1 ) can be activated so that the overflow tank ( 121 ) for the exchange of heat transfer medium between the heat transfer medium overflow circuit ( 12 ) and the heat transfer medium transport cycle ( 11 ) is available. Heat transfer medium circuit according to claim 1, wherein the heat transfer medium overflow circuit ( 12 ) at least one further overflow container ( 122 ), which depends on a different from the activation value of the operating parameter of the heat transfer medium circuit further activation value of the operating parameter of the heat transfer medium circuit ( 1 ) can be activated, so that the further overflow container ( 122 ) for the exchange of heat transfer medium between the heat transfer medium overflow circuit and the heat transfer medium transport circuit ( 11 ) is available. Heat transfer medium circuit according to claim 2, wherein the overflow container ( 121 ) and the further overflow container ( 122 ) can be activated independently of each other. Heat transfer medium circuit according to one of claims 1 to 3, wherein the heat transfer medium overflow circuit at least one separating device ( 124 . 125 ) for separating the overflow container from the heat transfer medium overflow circuit and / or for separating the further overflow container from the heat transfer medium overflow circuit. Heat transfer medium circuit according to one of claims 1 to 4, wherein the operating parameter is a heat transfer medium temperature of the heat transfer medium of the heat transfer medium circuit ( 1 ). Heat transfer medium circuit according to claim 5, wherein the overflow container ( 121 ) is a low-temperature overflow tank and the activation value is below a predetermined separation temperature. Heat transfer medium circuit according to claim 6, wherein the further overflow container ( 121 ) is a high temperature overflow tank and the further activation value is above the predetermined separation temperature. The heat transfer medium circuit according to claim 6 or 7, wherein the separation temperature is selected from the range of 150 ° C to 300 ° C. Heat transfer medium circuit according to one of claims 1 to 8, wherein the heat transfer medium comprises at least one selected from the group thermal oil and molten salt substance. Method for transporting heat transfer medium by means of a heat transfer medium circuit according to one of Claims 1 to 9, the overflow container ( 121 ) is activated as a function of the activation value of the operating parameter, so that the exchange of heat transfer medium ( 2 ) between the heat transfer medium overflow circuit ( 12 ) and the heat transfer medium transport cycle ( 11 ) with the help of the overflow tank ( 121 ) he follows. Method according to claim 10, wherein the further overflow container ( 122 ) is activated as a function of the further activation value of the operating parameter, so that the exchange of heat transfer medium between the heat transfer medium overflow circuit ( 12 ) and the heat transfer medium transport cycle ( 11 ) with the help of the further overflow tank ( 122 ) he follows. A method according to claim 10 or 11, wherein the operating temperature is a heat transfer medium temperature of the heat transfer medium ( 2 ) of the heat transfer medium circuit ( 1 ) is used. Use of the heat transfer medium circuit according to one of claims 1 to 9 in a solar thermal power plant ( 1000 ), is transported by means of the heat transfer medium circuit heat transfer medium for the production of electrical energy.

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