Abstract:
A method for retrofitting an already existing gas turbine power plant is provided. The method features at least the following steps: fluidically connecting a gas turbine to a flue gas duct which is suitable for conducting flue gas which is produced by the gas turbine; connecting the flue gas duct to a steam generating unit which is fluidically connected to a water-steam cycle, and via which water-steam cycle a power generating facility can be operated; fluidically connecting a CO2 separation apparatus to the flue gas duct for separating the CO2 from the flue gas in the flue gas duct; and electrically connecting the power generating facility to the CO2 separation apparatus, preferably for the essentially energy-autonomous operation of the CO2 separation apparatus.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the US National Stage of International Application No. PCT/EP2012/075199 filed Dec. 12, 2012, and claims the benefit thereof. The International Application claims the benefit of German Application No. 102012208221.2 filed May 16, 2012 and German Application No. 102012202729.7 filed Feb. 22, 2012. All of the applications are incorporated by reference herein in their entirety. 
     FIELD OF INVENTION 
     The present invention relates to a method for retrofitting an already existing gas turbine power plant which is to be equipped with a CO 2  separation apparatus. 
     BACKGROUND OF INVENTION 
     The separation of CO 2  gas from an exhaust gas low of a combustion system allows a reduced emission of CO 2  into the atmosphere. This, especially against the background of state and interstate regulated reductions of emitted CO 2 , is an economical cost factor which is increasingly taken into consideration in the commercial future plans of many undertakings. 
     At the same time, such a CO 2  separation method also enables the directed collection of CO 2  gas which in turn can be fed as a source material to special process engineering operations. Consequently, CO 2  can also be seen as a valuable base material. The “enhanced oil recovery” (EOR) process, for example, constitutes such a process for the technical use of CO 2 , in which CO 2  is injected into underground rock layers of oil deposits so that it is released in the crude oil which is present in these oil deposits and at the same time brings about a viscosity reduction of the crude oil. On account of the viscosity reduction, the flowability of the oil is significantly increased and can therefore be extracted more easily from the rock structures with lower flow resistance. At the same time, the CO 2  which is injected into the underground oil deposits serves for increasing the ambient pressure in the oil deposits, as a result of which a directional flow behavior of the crude oil, which has been changed with regard to its viscosity, can be achieved. 
     The CO 2  gas which is introduced into the oil deposits currently originates predominantly from refining processes of the natural gas producing industry. Over recent years, it has been proved, however, that the costly transporting of CO 2  produced in this way from the refinery sites to the oil deposits requires a sometimes large and expensive piping network. The provision of such a network, however, in turn greatly increases the costs for the CO 2  and therefore the costs for the crude oil which is extracted with the aid of the CO 2 . 
     In this respect, a changeover has already been made in part to locating the natural gas processing in local proximity to the oil deposits. Since the crude oil extraction typically also delivers natural gas as a by-product, the natural gas which is produced there can be processed comparatively cost effectively and consequently CO 2  can be produced comparatively more cost effectively. 
     Further efforts are directed towards separating CO 2  from the combustion systems, which are operated for the oil extraction, in the regions of the oil extraction for power generation. The combustion systems, on account of the strong presence of natural gas in the regions of crude oil extraction, are mostly constructed as gas turbines. To this end, the combustion system is equipped with a suitable CO 2  separation apparatus for the operation, wherein the CO 2  which is produced by means of the CO 2  separation apparatus can be further processed. Also, the CO 2  which is produced in this way can be pumped under pressure directly into the oil deposits for improved oil yield. The equipping of the combustion system with a CO 2  separation apparatus is typically carried out in this case by both components being designed and interconnected in an overall system, wherein both components are adapted to the respectively other component with regard to their operation. 
     Even if the combustion system, on account of the oxidative combustion taking place in it, can produce CO 2  in comparatively large quantities, its separation in a downstream CO 2  separation apparatus is possible only by means of an energy-intensive CO 2  separation process. This additional consumption of energy on the one hand reduces the cost effectiveness of the CO 2  which is produced in this way and, in addition, also appreciably reduces the overall efficiency of the system consisting of combustion system and CO 2  separation apparatus. 
     Consequently, it is desirable to propose a suitable method for retrofitting an already existing gas turbine power plant with a CO 2  separation apparatus, wherein the retrofitting method shall not limit the power output, especially the electric power output of the gas turbine. It is also desirable to retrofit an already existing gas turbine power plant in such a way that an efficient separation of CO 2  from the flue gas of the gas turbine power plant is made possible. Retrofitting of a gas turbine power plant which allows an essentially energy-autonomous operation of a CO 2  separation apparatus which is fluidically connected thereto is to be especially preferably made possible. 
     SUMMARY OF INVENTION 
     These objects upon which the invention is based are achieved by means of a method for retrofitting an already existing gas turbine power plant according to the independent claims. 
     In particular, the invention is achieved by means of a method for retrofitting an already existing gas turbine power plant, wherein the method features at least the following steps:—fluidically connecting a gas turbine ( 5 ) to a flue gas duct ( 2 ) suitable for conducting flue gas which is produced by the gas turbine ( 5 );—connecting the flue gas duct ( 2 ) to a steam generating unit ( 10 ) which is fluidically connected to a water-steam cycle ( 11 ), and via which water-steam cycle ( 11 ) a power generating facility ( 12 ) can be operated;—fluidically connecting a CO2 separation apparatus ( 20 ) to the flue gas duct ( 2 ) for separating the CO2 from the flue gas in the flue gas duct ( 2 ), and—electrically connecting the power generating facility ( 12 ) to the CO2 separation apparatus ( 20 ), preferably for the essentially energy-autonomous operation of the CO2 separation apparatus ( 20 ). 
     In this case, and subsequently, an electrical connection is to be understood in its broadest possible sense. In particular, an electrical connection is to comprise a direct, as well as an indirect, electrical connection. 
     Also, it is possible according to the embodiment that the power generating facility is connected to additional electric energy-consuming components so that these can be operated in an economical manner. Such components are partially described further below. 
     In this case, and subsequently, the term gas turbine power plant is also to be understood in a broad form. In particular, gas turbine power plants according to the invention also include gas turbine-based combustion systems which are used in the oil extraction industry as well as in the chemical industry. The gas turbine power plants according to the invention, however, are not provided in a combined cycle arrangement but are designed as a single-cycle or simple-cycle power plant. 
     In addition, the gas turbine power plants according to the invention are conventional and not adapted to later extensions in a way that they could be equipped with a CO2 separation apparatus without further technical modifications, for example, i.e. the gas turbine power plants according to the invention are particularly not capture-ready power plants. 
     According to the invention, the method for retrofitting an already existing gas turbine power plant allows a suitable connection of various functional components of the power plant in such a way that an energy-efficient operation with simultaneous separation of CO2 from the flue gas of the gas turbine can be achieved. To this end, the gas turbine is first provided with a flue gas duct in such a way that the flue gas which is produced by the gas turbines during combustion can be suitably discharged. By connecting the flue gas duct to a steam generating unit, the heat which is contained within the flue gas can be transferred in a suitable manner to a water-steam cycle. This water-steam cycle, moreover, is designed for operating a power generating facility. 
     After heat transfer has been carried out by means of the steam generating unit, the flue gas is to be fed to a CO2 separation apparatus, for which reason fluidically connecting the flue gas duct to such a CO2 separation apparatus has to be undertaken. As a result of electrically connecting the power generating facility to the CO2 separation apparatus, the electric energy-consuming components of the CO2 separation apparatus can be supplied with electric energy in a particularly energy-efficient manner. The electric energy, which originates from extraction of the heat from the flue gas by means of the steam generating unit, consequently allows operation of the CO2 separation apparatus without having to fall back on the electric energy which has been generated by operation of the gas turbine in the power plant. 
     Above all, the method for retrofitting an already existing gas turbine power plant makes provision for an additional power generating source, specifically the power generating facility which is especially provided solely for the provision of electric energy for the components of the CO2 separation apparatus. 
     Furthermore, it is naturally also possible to make the electric energy which is generated in this way also available to even more electric energy-consuming components which suitably interact either with the flue gas duct or with the components which are connected thereto. 
     The retrofitting of an already existing gas turbine power plant allows an extension of the power plant with regard to its functionality. Thus, during operation of the gas turbine power plant not only electric energy is generated but CO2 is also accumulated in a directed manner and can be made available for oil extraction, for example. To this end, the CO2 is discharged from the CO2 separation apparatus and fed to the oil deposits in a suitable form. Since gas turbine power plants are typically also operated in the regions of oil extraction for providing electric energy, CO2 can be produced directly on site, i.e. in proximity to the oil deposits. Consequently, an energy-inefficient and cost-intensive transporting of CO2 over longer distances is dispensed with. 
     Moreover, the gas turbine power plants are not restricted with regard to their electric efficiency when retrofitted so that these, without limitations, can still deliver the quantities of electric energy for which they were originally designed. The electric energy which is required for CO2 separation can be provided totally, or at least predominantly, by means of the power generating facility. 
     According to a first especially preferred embodiment of the method according to the invention for retrofitting, it is provided that the step of electrically connecting the power generating facility to the CO2 separation apparatus comprises, or is, a connection to at least one pump of the CO2 separation apparatus. Accordingly, the method allows operation of the pumps incorporated by the CO2 separation apparatus by means of the quantities of electric energy which is generated by means of the power generating facility. The consumption of electric energy which is generated elsewhere is therefore unnecessary. In this case, reference is also to be made to the fact that in a CO2 separation apparatus pumps can typically be the components which consume the most electric energy. By supplying these pumps alone with electric energy from the power generating facility the overall efficiency of the gas turbine power plant comprising the CO2 separation apparatus can be noticeably increased. 
     According to a further embodiment of the method according to the invention it is provided that the CO2 separation apparatus includes at least one absorber section and at least one desorber section, the two being fluidically interconnected, wherein especially the step of fluidically connecting a CO2 separation apparatus to the flue gas duct comprises, or is, a fluidic connection to the at least one absorber section. According to the embodiment, the CO2 separation apparatus therefore includes an absorber section in which the CO2 is washed out of the flue gas of the gas turbine typically by means of a scrubbing agent. For recovery of the scrubbing agent, or for separation of the thus removed CO2 from the scrubbing agent, the scrubbing agent is thermally treated in the desorber section. The thermal treatment typically requires temperatures of at least 100° C. or above and after desorption of the CO2 from the scrubbing agent allows a directed separation of both substances. The gaseous CO2 can be discharged in a suitable form. The scrubbing agent is made available in turn for further CO2 absorption in the absorber section and is once again fed to this. 
     A detailed representation of the individual processes in such a CO2 separation apparatus, which includes at least one absorber section and at least one desorber section, can be gathered from DE 102012202703.3. 
     This document, moreover, is also to be expressly incorporated by reference into the present application. 
     According to a further embodiment of the method according to the invention, in addition a step of thermally connecting the water-steam cycle to the CO2 separation apparatus, especially a step of thermally connecting the water-steam cycle to a desorber section of the CO2 separation apparatus, is also included. The thermal connection allows thermal energy to be extracted from the water-steam cycle and fed to the CO2 separation apparatus. The CO2 separation apparatus can be operated in a particularly energy-efficient manner as a result of providing the additional thermal energy. In particular, if the CO2 separation apparatus includes at least one absorber section and also at least one desorber section, a thermal dissipation of thermal energy from the water-steam cycle is suitable for operation of the desorber section. Since the desorber section has to be supplied with thermal heat during operation, the thermal energy which is extracted from the water-steam cycle can consequently be made available in a suitable manner to the desorber section. At the same time, the thermal connection of the water-steam cycle to the CO2 separation apparatus can constitute a suitable heat sink in the water-steam cycle which in the first place enables an operation of the steam generating unit which is connected to the water-steam cycle. 
     According to a further embodiment of the method according to the invention, a further step of fluidically connecting the CO2 separation apparatus to a CO2 supply network, which is particularly designed as a step of fluidically connecting a desorber section of the CO2 separation apparatus to a CO2 supply network, can be included. The CO2 supply network in this case serves for supplying the oil extraction industry with suitable quantities of CO2. As a result of a direct feed of the CO2 into the supply network in question, the CO2 can be made available to the oil extraction industry in a direct and especially inexpensive manner. 
     According to a further embodiment of the method according to the invention, in addition a cooling circuit is fluidically connected to the water-steam cycle and its electric energy-consuming components are electrically connected to the power generating facility, or its thermal energy is made available to the CO2 separation apparatus. This cooling circuit can be designed as a thermal connection of the water-steam cycle to the CO2 separation apparatus, for example, as described above. This cooling circuit can also be designed as an external cooling circuit which can provide refrigeration capacity. In particular, the cooling circuit can also comprise cooling towers which are suitable for supplying the cooling circuit with suitable refrigeration capacity. 
     According to a further preferred embodiment of the invention, in addition a refrigerating machine is fluidically connected downstream to the CO2 separation apparatus, which refrigerating machine is designed for condensing water out of the gas flow issuing from the CO2 separation apparatus during operation. The refrigerating machine consequently enables the provision of liquid water, which is discharged from the CO2 separation apparatus, during operation. The water which is condensed out in the refrigerating machine in this case originates for the most part from the combustion process in the gas turbine, in which fuel, preferably natural gas, is combusted, forming CO2 and water. On account of the comparatively large quantities of natural gas which are consumed in the power plant during operation of the gas turbine, water can be produced in industrially usable quantities. This, after being condensed out in the refrigerating machine, is made available for further process engineering or power plant engineering operations. It is also conceivable that the water which is condensed out in this way can be passed on for human utilization. 
     According to a further preferred embodiment of the method according to the invention, a heat exchanger is connected to the flue gas duct and is designed for transferring heat from the flue gas in the flue gas duct to the gas flow issuing from the CO2 separation apparatus. Consequently, on the one hand heat can be extracted from the flue gas which is fed to the CO2 separation apparatus, as a result of which it can be cooled to a temperature which is suitable for operation of the CO2 separation apparatus. At the same time, heat can be fed to the gas flow issuing from the CO2 separation apparatus so that this gas flow can discharge from a chimney, for example, by means of convective air circulation. In this case, the temperature level of the flue gas which is fed to the CO2 separation apparatus is typically between 30° C. and 100° C., preferably between 30° C. and 50° C., wherein this temperature level basically remains constant during passage of the flue gas through the CO2 separation apparatus. After thermal treatment of the gas flow, issuing from the CO2 separation apparatus, in a previously described refrigerating machine, the temperature can be lowered to about 10 to 25° C. On account of this relatively low temperature level in comparison to the ambient temperature, additional heat has to be added to the gas flow so that by means of a chimney, for example, it can be convectively fed to air layers of the environment which lie above ground level. 
     According to a further aspect of the method according to the invention for retrofitting, a cooling device is connected to the flue gas duct, which cooling device is provided especially between the steam generating unit and the CO2 separation apparatus and is designed for extracting heat from the flue gas which is present in the flue gas duct and for energetically supplying a refrigeration process therewith. The cooling device is consequently suitable for providing additional cooling capacity. This cooling capacity can be demanded by components which are connected to the gas turbine power plant or can also be made available to additional external components. The cooling device is especially designed as an adsorption refrigerating machine, as an absorption refrigerating machine and/or as a steam-jet refrigerating machine. Depending upon the demanded cooling capacity, a greater or lesser quantity of thermal energy is extracted from the flue gas in the flue gas duct. 
     According to a further preferred embodiment of the invention, the power generating facility comprises a back-pressure turbine which is coupled to a generator. Since such a back-pressure turbine can be used in a particularly energy-efficient manner for electric power generation, provision is especially preferably made for such a back-pressure turbine. 
     According to a further embodiment of the invention, the gas turbine is not modified with regard to its electric power output when being retrofitted. This circumstance is sometimes essential for advantageous efficiency during operation of the system consisting of gas turbine and CO2 separation apparatus. 
     It is also possible that according to a further embodiment the operating parameters of the gas turbine are not adjusted with regard to the retrofit, especially with regard to the operation of the steam generating unit and the operation of the CO2 separation apparatus. Consequently, the operation of the CO2 separation apparatus requires relatively few adjustments, or no adjustments, of the process during operation of the gas turbine. The CO2 production by means of the CO2 separation apparatus is therefore carried out basically independently of the operation of the gas turbine and temporally downstream. This embodiment consequently enables a simplified connection between gas turbine and CO2 separation apparatus. 
     In the following, the invention shall be explained with reference to further figures. In this case, the figures show only schematic representations which shall not limit the concrete realization of the invention according to one embodiment. 
     In addition, the figures are to be understood only by way of example and therefore in turn do not limit the generality in which the present invention is claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In this case, in the drawing: 
         FIG. 1  shows a first embodiment of the system which is created by means of the inventive method for retrofitting an already existing gas turbine power plant. 
         FIG. 2  shows a flow diagram for representing the sequence of individual steps according to an embodiment of the method according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
       FIG. 1  shows a first embodiment of a system, having gas turbine  5  and CO 2  separation apparatus, which is created by means of the method according to the invention for retrofitting an already existing gas turbine power plant  1 . To this end, a flue gas duct  2  has been connected to a gas turbine  5  and is suitable for discharging the flue gas which issues from the gas turbine  5 . The flue gas is directed by means of the flue gas duct  2  to a steam generating unit  10  which by means of thermal contact extracts thermal energy from the flue gas and transfers this thermal energy to a water-steam cycle  11 . The fluid flow in the water-steam cycle  11  is maintained by a pump (not provided with a designation in the present case) and after passing through the steam generating unit  10  is fed to a back-pressure turbine  13 . By expansion in the back-pressure turbine  13  and also by release of thermal energy for providing mechanical energy in the back-pressure turbine  13 , a generator  14 , connected to said back-pressure turbine  13 , is driven. The electric energy which is generated during operation of the generator  14  is fed via a suitable electrical connection to a separation apparatus  20 . The water-steam cycle  11 , moreover, has a cooling circuit  15  which is designed for drawing heat from the water-steam cycle  11  and feeding this to the separation apparatus  20 . The CO 2  separation apparatus  20  can use this heat for heating suitable parts, especially for heating suitable parts in a desorber section  25 . At the same time, the cooling circuit  15  within the water-steam cycle  11  constitutes a suitable heat sink. 
     After release of thermal energy by means of the flue gas to the steam generating unit  10 , the flue gas in the flue gas duct  2  comes into thermal contact with a cooling device  60  and makes this heat capacity available for producing refrigeration capacity. The cooling device  60  is especially constructed as an adsorption or absorption refrigerating machine. 
     Fluidically downstream, thermal energy is also extracted from the flue gas in the flue gas duct  2  by means of a heat exchanger  50 , wherein the heat which is extracted in this way is transferred to the gas flow issuing from the CO 2  separation apparatus  20 . The heat is especially transferred to a gas flow issuing from a refrigerating machine  40 , which refrigerating machine  40  is fluidically connected downstream to the CO 2  separation apparatus  20 . 
     If, as a result of the previously described thermal conditioning steps, the flue gas in the flue gas duct should still not have been sufficiently cooled for operation of the CO 2  separation apparatus  20 , it is also possible to provide additional components which are connected to the flue gas duct  2  and can extract heat from the flue gas flowing therein. 
     The flue gas which is thermally conditioned in this way is fed to the CO 2  separation apparatus  20 . The flue gas is especially fed to an absorber section  24  which is fluidically connected to a desorber section  25 . In the absorber section  24 , the inflowing flue gas is suitably treated with a scrubbing agent so that the CO 2  is separated from the flue gas. After separation has been carried out, the compound consisting of scrubbing agent and CO 2  is fed to the desorber section  25  by means of a suitable pump  21 , wherein the desorber section  25  thermally treats the compound of scrubbing agent and CO 2  in such a way that both substances are separated. This is carried out at temperatures of approximately 100° C. or above. After separation of both substances has been carried out, the CO 2  can be transferred via a suitable discharge line from the CO 2  separation apparatus  20  into a CO 2  supply network  30 . The regenerated scrubbing agent is fed in turn from the desorber section to the absorber section  24  in order to again absorb, i.e. wash out, CO 2  there. 
     The gas flow issuing from the CO 2  separation apparatus  20  is fed according to the embodiment to a refrigerating machine  40  which again extracts thermal energy from the gas flow to such an extent that the water present in the gas flow condenses out. Consequently, the dew point for water of the gas flow issuing from the CO 2  separation apparatus  20  is fallen short of. 
     The condensed water can be extracted via a suitable drain line. The drain line can also feed the water for intermediate storage to a storage tank, which is not additionally shown, from which a desired quantity of water can also be extracted when the refrigerating machine  40  is not in a position to deliver the demanded quantities at short notice. So, the quantity of liquid water which is produced by the refrigerating machine  40 , for example, can also depend upon the ambient temperature. If, for example, water is required to an increasing extent in the event of relatively high ambient temperature, such as during the daytime with full exposure to sunlight, it is advisable to collect water at a time of day at which the ambient temperatures are lower and consequently the provision of liquid water by means of the refrigerating machine  40  can be carried out more efficiently. This is the case during the night-time hours, for example. The water which is collected in this way can especially be fed back again into the CO 2  separation apparatus  20  during a daytime operation with full exposure to sunlight in order to compensate liquid losses there. 
     For operation of the refrigerating machine  40 , electric energy can be supplied to this via a suitable supply line. This electric energy can be provided especially by means of the generator  14  which interacts with the back-pressure turbine  13  for power generation. 
     The gas issuing from the refrigerating machine  40  is again thermally conditioned in the heat exchanger  50  so that its temperature level is increased. During this, heat from the flue gas which is provided for feeding to the CO 2  separation apparatus  20  is transferred to the gas flow issuing from the refrigerating machine  40 . A transfer of heat is necessary since the gas issuing from the refrigerating machine  40  does not have sufficient heat in order to be able to be discharged via a chimney, for example. 
       FIG. 2  shows a flow diagram for explaining a first embodiment of the method according to the invention for retrofitting an already existing gas turbine power plant  1 . According to a first step, a gas turbine  5  is connected to a flue gas duct  2 . This connection enables the directed discharging and conducting of the flue gas issuing from the gas turbine  5 . According to a second step, the flue gas duct  2  is connected to a steam generating unit  10  which is fluidically connected to a water-steam cycle  11  and is provided for operating a power generating facility  12 . Consequently, thermal heat can be extracted from the flue gas in the flue gas duct  2  and can be transferred to the water in the water-steam cycle  11 . This thermal heat is converted in a thermal water-steam process into electric energy by means of the power generating facility  12 . According to a third step, the flue gas duct is fluidically connected to a CO 2  separation apparatus  20 , wherein the CO 2  separation apparatus  20  is preferably suitable for removing CO 2  from the flue gas. The removal enables the directed collection and also the directed discharge of the CO 2  which is produced in this way. According to a further subsequent step of the method according to the embodiment, the power generating facility  12  is electrically connected to the CO 2  separation apparatus  20 . Consequently, the electrical components which are comprised by the CO 2  separation apparatus can be supplied and operated by means of the electric current from the power generating facility  12 . This in turn increases the efficiency of the overall power plant process since no electric energy has to be supplied from outside for operating the electrical components of the CO 2  separation apparatus  20 . Rather, the energy for operating the CO 2  separation apparatus  20  originates from the flue gas of the gas turbine  5 , which would anyway be fed in an unused state to the environment. This especially relates to gas turbines  5  which are operated in the sense of a single-cycle arrangement. 
     Further embodiments are gathered from the dependent claims.