Abstract:
In a plant having integrated CO 2  removal, for pig iron production or synthesizing gas, at least part of the offgas or synthesis gas is discharged as export gas from the plant, optionally collected in an export gas container and subsequently thermally utilized in a gas turbine. The offgas from the gas turbine is fed to a waste heat boiler for generation of steam. To reduce the addition of high-grade fuel gases, at least part of the tailgas from the CO 2  removal plant is mixed into the export gas upstream of the gas turbine as a function of the joule value of the export gas after addition of the tailgas. The proportion of tailgas is increased when the joule value of the export gas goes above a predefined maximum joule value and the proportion of tailgas is reduced when the joule value of the export gas drops below a predefined minimum joule value.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the U.S. national stage of International Application No. PCT/EP2012/053979, filed Mar. 8, 2012 and claims the benefit thereof. The International Application claims the benefit of Austrian Application No. A369/2011 filed on Mar. 17, 2011, both applications are incorporated by reference herein in their entirety. 
     
    
     BACKGROUND 
       [0002]    Described below is a process for regulating the joule value of offgases from pig iron production plants having integrated CO 2  removal plants, wherein at least one part of the offgas is discharged from the pig iron production plant as export gas, if necessary collected in an export gas container and subsequently thermally utilized in a gas turbine, wherein the offgas from the gas turbine is supplied to a waste heat boiler for the generation of steam. The process can equally be utilized for regulating the joule value of synthesis gas from plants for synthesis gas production having integrated CO 2  removal plants, wherein at least one part of the synthesis gas is discharged from the plant for synthesis gas production as export gas, not, however, collected in an export gas container, but subsequently thermally utilized in a gas turbine, wherein the offgas from the gas turbine is supplied to a waste heat boiler for the generation of steam. Also described below is a plant for carrying out the process. 
         [0003]    There are fundamentally two known common methods for the production of pig iron, which should also include the production of pig iron products: the blast furnace process and the smelting reduction process. 
         [0004]    During the blast furnace process, firstly pig iron is produced from iron ore by coke. Furthermore, iron scrap can additionally be used. Then steel is produced from pig iron through further processes. The iron ore is mixed as lump ore, pellets or sinter together with the reducing agent (mostly coke, or also coal, e.g. in the form of a fine coal injection plant) and further components (limestone, slag formers, etc.) with the so-called burdens and subsequently charged into the blast furnace. The blast furnace is a metallurgical reactor, in which the batch column reacts in the counter flow with hot air, the so-called hot blast. By burning the carbon from the coke, the heat and carbon monoxide or hydrogen necessary for the reaction are produced, the hydrogen representing a significant part of the reduction gas and flowing through the batch column and reducing the iron ore. As a result, pig iron and slag are produced, which are periodically tapped off. 
         [0005]    In the so-called oxygen blast furnace, which is also identified as a blast furnace having top gas or furnace gas recirculation, oxygenated gas with a proportion of oxygen (O 2 ) of more than 90% by volume is blown into the blast furnace, during the gasification of coke or coal. 
         [0006]    A gas purification (e.g. dust separator and/or cyclones combined with wet scrubbers, bag filter units or hot gas filters) must be provided for the gas emitted from the blast furnace, the so-called top gas or furnace gas. Furthermore, most of the time in the oxygen blast furnace, a compressor, which may have an after-cooler, is provided for the top gas, which is recirculated in the blast furnace, as well as a device for removing CO 2 , mostly by pressure swing adsorption, as known in the related art. 
         [0007]    Further options for the embodiment of a blast furnace process are a heater for the reduction gas and/or a combustion chamber for the partial combustion with oxygen. 
         [0008]    The disadvantages of the blast furnace are the demands on the input materials and the high emissions of carbon dioxide. The iron source and the coke which is used must be hard and in lumps, such that enough cavities remain in the batch column, which guarantee that the wind, which is blown in, flows through. The CO 2  emissions represent a strong environmental burden. Therefore there are efforts to remove the blast furnace route. To be noted here are the sponge iron production based on natural gas (MIDREZ, HYL, FINMET®) as well as the smelting reduction processes (COREX® and FINEX® processes). 
         [0009]    A smelter gasifier is used during the smelting reduction process, in which hot liquid metal is produced, as well as at least one reduction reactor, in which the source of the iron ore (lump ore, fine ore, pellets, sinter) is reduced with reduction gas, wherein the reduction gas is generated in the smelter gasifier by gasification of coal (and, if necessary, of a small proportion of coke) with oxygen (90% or more). 
         [0010]    As a rule, during the smelting reduction process
       gas purification plants (on the one hand for the top gas from the reduction reactor, on the other hand for the reduction gas from the smelter gasifier),   a compressor, which may have an after-cooler, for the reduction gas, which is recirculated in the reduction reactor,   a device for removing CO 2 , mostly by pressure swing adsorption, as known in the related art   as well as, optionally, a heater for the reduction gas and/or a combustion chamber for the partial combustion with oxygen are also provided.       
 
         [0015]    The COREX® process is a two-step smelting reduction process. The smelting reduction process combines the process of the direct reduction (pre-reduction of iron to sponge iron) with a smelting process (main reduction). 
         [0016]    The equally well-known FINEX® process corresponds significantly to the COREX® process, however iron ore is introduced as fine ore. 
         [0017]    The process is not only able to be used in pig iron generation, but also in synthesis gas plants. Synthesis gases are all gaseous mixtures containing hydrogen and mostly also containing CO, which should be used in a synthesis reaction. Synthesis gases can also be produced from solid, liquid or gaseous substances. In particular these include the coal gasification (coal is transformed with water vapor and/or oxygen to hydrogen and CO) and the production of synthesis gas from natural gas (transformation of methane with hydrogen and/or oxygen to hydrogen and CO). Beneficially, in the case of the coal gasification, the export gas storage, as is provided according to pig iron production plants, can be omitted, because the high synthesis gas pressure from the gasifier (mostly &gt;20 bar g , such as approximately 40 bar g ) can also equally be used in the gas turbine, where, as a rule, a gas pressure of approximately 20-25 bar g  is needed. The tail gas, which is rich in CO 2 , from the CO 2  removal plant must, however, be compressed to the pressure of the synthesis gas flow by a compressor. 
         [0018]    If the CO 2  emissions into the atmosphere are to be reduced in the production of pig iron or in the generation of synthesis gas, these must be removed from the offgases from the pig iron or synthesis gas production and captured in a combined form (CO 2  capture and sequestration (CCS)). 
         [0019]    Until now the pressure swing adsorption (PSA), in particular also the vacuum pressure swing adsorption (VPSA), has principally been used to remove CO 2 . The pressure swing adsorption is a physical process for the selective deconstruction of gaseous mixtures under pressure. Special porous materials (e.g. zeolite, activated carbon, activated silicon oxide (SiO 2 ), activated aluminum oxide (Al 2 O 3 ) or the combined use of these materials) are used as a molecular sieve, in order to adsorb molecules according to their adsorption strengths and/or their kinetic diameter. During PSA, the fact that gases adsorb at various strengths to the surface is used. The gaseous mixture is introduced into a column under an exactly defined pressure. Now the undesirable components (here CO 2  and H 2 O) and the recyclable material (here CO, H 2  CH 4 ) flow through the column, to a great extent unobstructed. As soon as the adsorbent is completely loaded, the pressure is reduced and the column is backwashed. An electric current for the preceding compression of the gas, which is recirculated and is rich in CO 2 , is needed to operate a (V)PSA plant. 
         [0020]    The product gas flow after the pressure swing adsorption, which contains the recyclable material, still contains, for example, 2-6% by volume CO 2  in the offgases from the pig iron generation. The tail gas flow from the (V)PSA plant still, however, contains relatively high reducing gas proportions (for example CO, H 2 ), which are lost during the pig iron production. 
         [0021]    The tail gas flow after the pressure swing adsorption, which contains the undesired components, is typically composed as follows in the offgases from the pig iron production: 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Combination 
                 % by vol during VPSA 
                 % by vol during PSA 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 H 2   
                 2.2 
                 5.5 
               
               
                   
                 N 2   
                 1.5 
                 2.4 
               
               
                   
                 CO 
                 10.9 
                 16.8 
               
               
                   
                 CO 2   
                 82.1 
                 72.2 
               
               
                   
                 CH 4   
                 0.7 
                 0.9 
               
               
                   
                 H 2 O 
                 2.6 
                 2.2 
               
               
                   
                   
               
             
          
         
       
     
         [0022]    The tail gas cannot simply be thermally utilized, because for that—due to the low and/or fluctuating joule values of, for example, ±50%—it would have to be augmented with other fuels. It can, for example, be added in its entirety to the so-called export gas, which is the part of the process gas, which is removed from the process of the pig iron or synthesis gas generation and is used for other purposes, for example as a fuel in a combined gas and steam power station, which is also identified as a combined cycle power plant (CCPP). Components of the export gas in the pig iron generation can be:
       top gas and/or generator gas from a blast furnace, a reduction reactor (fluidized bed reactor) or a reduction shaft (fixed bed reactor)   so-called offgas from a reduction reactor (fluidized bed reactor)   so-called excess gas from a smelter gasifier       
 
         [0026]    The addition of tail gas from the CO 2  removal to the export gas is, then, only beneficial if the joule value of the export gas is so high that it does not drop under a value after the addition of the tail gas that is too low for the subsequent use of the export gas. 
         [0027]    A reduced joule value of the export gas subsequently decreases the efficiency of a power station supplied with the export gas, for example in a combined cycle power plant, because of the high compression of gaseous fuel and because of the lower efficiency of the gas turbine. In a steam power station or furnace the flame temperature would be reduced during the combustion. 
         [0028]    If an addition of the tail gas from the CO 2  removal to the export gas is not beneficial, this was until now combusted in its entirety on a hot flare. This does not only have the disadvantage that heat, which is produced during flaring, is lost, but also that considerable gas emissions in the form of carbon monoxide CO, hydrogen sulphide H 2 S, etc., can be produced by incomplete combustion of the tail gas in the hot flare. 
         [0029]    Another problem in using export gas from plants for the production of pig iron and synthesis gas is that the joule value of the export gas fluctuates. Therefore the export gas is captured in an export gas container having a large volume, e.g. in the size of 100,000 m 3 , before being supplied to a consumer, such as a power station, in order to homogenize the gas composition. In order to achieve a constant joule value having a fluctuation margin of +/−1-2%, until now waste nitrogen from an air deconstruction plant was added when the joule value deviated upwards from the desired constant value. Coke oven gas (for example from the pyrolysis of hard coal to coke for the blast furnace) was added when the joule value deviated downwards. 
         [0030]    A corresponding process for balancing the joule value is shown in AT 507 525 B1. According to this publication the export gas is supplied to a buffer unit, where the regulation of the joule value occurs, according to which the joule value is raised by the addition of smelter gas or natural gas and reduced by the addition of nitrogen or water vapor. 
         [0031]    In AT 507 525 B1, the accumulating tail gas from a CO 2  removal unit is collected in a particular storage unit, wherein the joule value in the captured tail gas is balanced. The tail gas, which is captured in advance, is supplied to a waste heat boiler, where steam is generated through the combustion of the tail gas, the steam driving a steam turbine and a generator. A part of the export gas can be supplied to the tail gas in the storage unit, the export gas having passed through a top gas pressure recovery turbine. 
         [0032]    When carrying out the combustion of the tail gas in the hot flare according to AT 507 525 B1, it is avoided, although it is disadvantageous, that high value gaseous fuel, such as smelter gas, which can be disposed of in the plant or specially provided natural gas, which is not available in the plant, is used for the regulation of the joule value of the export gas. 
         [0033]    Therefore described below is a process to regulate the joule value of the export gas, which manages with a small addition of high value gaseous fuel. 
       SUMMARY 
       [0034]    According to the method described below, at least one part of the tail gas from the CO 2  removal plant is added to the export gas before the gas turbine, in particular, if necessary, before the export gas container, depending on the joule value of the export gas after the addition of the tail gas, in particular after the export gas container, wherein the proportion of tail gas is increased if the joule value of the export gas rises above a predefined maximum joule value and the proportion of tail gas is lowered if the joule value of the export gas drops below a predefined minimum joule value. 
         [0035]    As a rule a desired joule value of the export gas, which depends on the gas turbine which is used, is specified, as well as a fluctuation margin, around which the actual joule value may deviate from the desired joule value in the operation. The upper end of the fluctuation margin represents the predefined maximum joule value and the lower end the predefined minimum value. If no fluctuation margin is specified, then the minimum joule value coincides with the maximum joule value. 
         [0036]    For the majority of the time in the operation, the joule value regulation is possible because of the quantity of tail gas added. It can also additionally be provided that the export gas, which is mixed with tail gas, passes through a buffer container before the gas turbine. In this buffer container a further gas, supplied before the buffer container, can be mixed with the mixture of export gas and tail gas. 
         [0037]    In this way it can be provided that, additionally, when the predefined minimum joule values before the gas turbine are not reached, for example before and/or after the buffer container, gaseous fuel is added. Gaseous fuel is identified as a gas that predominantly contains combustible gas. Typical gaseous fuels are natural gas, liquefied natural gas (LNG) and coke oven gas. 
         [0038]    If the joule value rises, it can in this way be provided that—additionally to the tail gas—non-combustible gas is added when the maximum joule value before the gas turbine is exceeded, for example before and/or after the buffer container. Non-combustible gas is identified as gas that predominantly contains non-combustible gases. Typical non-combustible gases are nitrogen or water vapor. 
         [0039]    The part of the tail gas, which is not added to the export gas, can be supplied to the smelter gas distribution system in the case of the pig iron production. The smelter gas distribution system includes all lines for gases, which accumulate in a smelter or are produced for smelting, thus, for example, gas for drying raw material (iron ore, coal) or gas, which is supplied from the smelter as fuel to a power station with a furnace. The gas distribution system is, of course, also a component part of the smelter gas distribution network for the furnace gas, the top gas or generator gas, the offgas and the excess gas. Ideally the tail gas is added to the furnace gas, as the joule value lies in the same region (the averaged joule value lies in the region of 2,000 to 4,000 kJ/Nm 3 ). The part of the tail gas, which is not added to the export gas, can also be supplied to a hot flare. 
         [0040]    In the case of failure or lack of receiving of the tail gas by the smelter gas distribution system, the tail gas can also be fed to the hot flare via a regulating valve. 
         [0041]    According to the process, the export gas can contain at least one of the following offgases:
       top gas from a blast furnace, in particular from an oxygen blast furnace having top gas recirculation,   offgas from a smelter gasifier of a smelting reduction plant, which is also identified as excess gas   offgas from at least one reduction reactor of a smelting reduction plant, which is also identified as offgas, or from a reduction shaft   offgas from at least one fixed bed reactor to preheat and or reduce iron oxides and/or compacted iron of a smelting reduction plant, which is also identified as top gas   synthesis gas from a plant for synthesis gas production.       
 
         [0047]    A plant for carrying out the process includes at least
       one pig iron production plant having an integrated CO 2  removal plant or one plant for synthesis gas production having an integrated CO 2  removal plant,   one export gas line, with which a part of the offgas or synthesis gas can be discharged as export gas from the pig iron production plant or for synthesis gas production,   if necessary, one export gas container, in which the export gas can be collected, as well as   one gas turbine, in which the export gas can be thermally utilized,   one waste heat boiler, in which the offgas from the gas turbine can be used for the production of steam.       
 
         [0053]    The plant is characterized in that the CO 2  removal plant is connected to the export gas line such that at least one part of the tail gas from the CO 2  removal plant can be added to the export gas before the gas turbine, in particular, if necessary, before the export gas container, and such that a measuring instrument for measuring the joule value of the export gas is provided after the addition of the tail gas, in particular after the export gas container. 
         [0054]    According to the variations in process described above, it can be provided that a buffer container is provided—if necessary after the export gas container and—before the gas turbine. 
         [0055]    At least one supply line can be provided before and/or after the buffer container, as well as at least one supply line for non-combustible gas. 
         [0056]    In the case of pig iron production, a line can be provided for the part of the tail gas, which is not added to the export gas, the line flowing into the smelter gas distribution system, such as into the furnace gas distribution system, or into a hot flare. 
         [0057]    As a rule, at least one line flows into the export gas line, with which
       top gas from a blast furnace, in particular from an oxygen blast furnace with top gas recirculation,   offgas from a smelter gasifier of a smelting reduction plant,   offgas from at least one reduction reactor or reduction shaft of a smelting reduction plant,   offgas from at least one fixed bed reactor for heating and/or reducing iron oxides and/or compacted iron of a smelting reduction plant,   synthesis gas from a plant for synthesis gas production can be fed into the export gas line.       
 
         [0063]    With the process or the device described below, high value gaseous fuel, such as natural gas, liquefied natural gas or coke oven gas, can be saved and at the same time the joule value of the export gas can be adjusted at the gas turbine and thus a greater efficiency of the gas turbine can be achieved. By adding the tail gas from the CO 2  removal plant to the export gas, less to absolutely no tail gas is flared. The energy of the tail gas can therefore, for the most part, be converted to electrical energy and the gas emissions of the hot flare due to uncombusted tail gas will be reduced or at best will be completely avoided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0064]    These and other aspects and advantages will become more apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings of which. 
           [0065]      FIG. 1  is a schematic block diagram of a plant having a blast furnace 
           [0066]      FIG. 2  is a schematic block diagram of a plant having a FINEX® plant 
           [0067]      FIG. 3  is a schematic block diagram of a plant having a COREX® plant 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0068]    Reference will now be made in detail to the preferred embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
         [0069]    In  FIG. 1  an oxygen blast furnace having top gas recirculation  1  is depicted, in which iron ore from the sinter plant  2  as well as coke (not depicted) is supplied. Gas  3 , which contains oxygen and has an oxygen content &gt;90% by volume, is introduced into the ring line  4 , and, equally, heated reduction gas  5  is introduced into the reduction gas oven  6  together with cold or pre-heated oxygen O 2  in the blast furnace  1 . Slag  7  and pig iron  8  are removed from below. On the upper side of the blast furnace  1  the top gas or furnace gas  9  is extracted and is pre-treated in a dust separator or cyclone  10  and purified once again in a wet scrubber  11  (or a bag filter or hot gas filter system). The top or furnace gas, which is purified in this way, can on the one hand be extracted directly as export gas  12  from the blast furnace system and supplied to an export gas container  13 . On the other hand it can be supplied to a CO 2  removal plant, which is carried out here as a plant for the pressure swing adsorption of CO 2 , identified in short as a PSA plant  14 , wherein the purified top or furnace gas is compressed beforehand in a compressor  15  to, for example, 2- 6 bar   g  and is cooled in an after-cooler  16  to, for example, 30-60° C. 
         [0070]    The PSA plant  14  is known in the related art and therefore does not have to be further illustrated here. 
         [0071]    Here, the tail gas  20  is may be at least partially supplied to the export gas  12  before the export gas container  13  and is mixed with it. In the case of an adsorption plant for the removal of CO 2 —completely or partially—it could either be released back into the atmosphere after a H 2 S purification and/or supplied to a further compressor to liquefy CO 2 , in order to then transport it and store it, for example underground, or in order to use it as a replacement for nitrogen in the iron production. In the case of a (V)PSA for the removal of CO 2  and a sequestration, a further preparation plant is normally required to concentrate the CO 2  flow. 
         [0072]    The pressure energy content of the export gas  12  can also be used in a top gas pressure recovery turbine  35 , which in this example is arranged before the export gas container  13  and the supply line for the tail gas  20 . A corresponding diversion for the export gas  12  around the top gas pressure recovery turbine  35  is provided, in case the export gas  12 —for example in the case of a maintenance shut down of the top gas pressure recovery turbine—should not be fed through the top gas pressure recovery turbine  35 . The pressure of the export gas  12  is measured with a pressure gauge  17  after the top gas pressure recovery turbine  35  and before the supply line for the tail gas  20  and, depending on the measured pressure or on the level in the export gas container, a valve  18  in the line  21  for the export gas to the hot flare  19  is actuated: if the pressure of the export gas  12  or the level in the export gas container exceeds a predefined value, then at least a part of it is fed to the hot flare  19  and combusted there and the rest continues into the export gas container  13 . 
         [0073]    The export gas from the export gas container  13  is supplied to a combined cycle power plant  24  as a fuel, optionally via a buffer container  25  and optionally via a filter  26 . The export gas is supplied to a gaseous fuel compressor  27  and then to a gas turbine  28 . The waste heat from the gas turbine is used in the waste heat boiler  29  for a steam circulation with a steam turbine  30 . 
         [0074]    Export gas  22  that is not needed for the combined cycle power plant  24  can be removed after the export gas container  13  and supplied to the smelter gas distribution network, where is can be used for other purposes, for example for drying raw materials (drying coal, fine coal or ore) or it can be used as fuel for thermal use (e.g. steam power stations, boilers, etc.). The extraction of export gas  22  that is not needed can be carried out via a regulating valve, which is not depicted here, in the line for the export gas  22  that is not needed. 
         [0075]    A first measuring instrument  23  for measuring joule value is provided after the export gas container  13  and after the extraction line of the export gas  22  that is not needed. Depending on the measured value thereof, a fan  31  is regulated, which is arranged in a line  32  for tail gas. This line  32  branches off from the line for tail gas  20  before this flows into the line for export gas  12  and leads to the line for the export gas  22  that is not needed. If the joule value of the export gas rises above a predefined maximum joule value, then the power of the fan  31  is reduced, such that less tail gas is sucked into the line  32  and thus less tail gas reaches the export gas  22  that is not needed. Therefore more tail gas reaches the export gas container  13  and the joule value of the export gas drops. 
         [0076]    Instead of the fan  31 , a regulating valve can also simply be used, which is regulated because of the measured value of the first measuring instrument  23  for measuring the joule value and which increases the supply of tail gas  20  to the export gas  12  and thus in the export gas container  13 . 
         [0077]    If, however, the joule value of the export gas drops below a predefined minimum joule value, then the power of the fan  31  is increased (or a corresponding regulating valve is completely or partially opened), such that more tail gas is sucked or fed into the line  32  and thus more tail gas reaches the export gas  22  that is not needed. Therefore less tail gas reaches the export gas container  13  and the joule value of the export gas increases. 
         [0078]    In emergencies, a regulating valve, which is not depicted here, can also be opened, which introduces the tail gas into the hot flare  19  for combustion. 
         [0079]    The pressure at the foot of the hot flare  19  is smaller than approximately 5 kPa g . In turn, this pressure is smaller than the pressure of the export gas  12 , which as a rule lies between 8 and 12 kPa g , wherein the pressure is lowered to a pressure of 7-9 kPa g  in the export gas container  13  because of pipe line pressure loss to the extent of, for example, 1-3 kPa g . 
         [0080]    As the line system, including that for the tail gas  20  as well as the line  32 , remains connected to the line system for the export gas  12  during the entire operation, the desorption pressure for the PSA plant  14  also does not change. Thus there is no worsening in the operation of the PSA plant  14  due to the process described herein. 
         [0081]    As the regulation of the joule value by the fan  31  or the regulating valve for the tail gas does not always have to be sufficient, a further buffer container  25  is, if necessary, additionally arranged after the export gas container  13  and after the first measuring instrument  23  for measuring joule value, in which buffer container  25  the export gas  12 , which is, if necessary, already mixed with the tail gas  20 , can be mixed with further gases. Hereto a supply line  33  for gaseous fuel (e.g. natural gas, liquefied natural gas, coke oven gas) as well as a supply line  34  for non-combustible gas  34  (e.g. nitrogen, like waste nitrogen from an air deconstruction plant, or water vapor) are arranged between the first measuring instrument  23  for measuring joule value and the buffer container  25 . With these supply lines gaseous fuels can now be added, in the case that the joule value cannot be raised above the predefined minimum joule value even without the addition of the tail gas. Analogically, non-combustible gas can be added, if the joule value cannot drop below the predetermined maximum value even with the addition of the entire tail gas. 
         [0082]    A second measuring instrument  36  for measuring joule value is provided after both of these supply lines, however before the buffer container  25 . This controls whether the joule value can be adjusted between a predefined minimum and maximum joule value through the supply lines  33 ,  34  lying before it. In the case that it cannot, gaseous fuel or non-combustible gas can be once again added by supply lines  33 ,  34 , which are arranged after the buffer container  25 . The joule value, which is achieved in this way, is calculated with a third measuring instrument  56  for measuring joule value. This measuring instrument  56  is provided after the supply lines  33 ,  34 , which are arranged after the buffer container  25  and before the gas compressor  27  and here also before the filter  26 . 
         [0083]    The typical joule value of the tail gas from a PSA plant  14  lies at 700-900 kcal/Nm 3  and the joule value of the offgas from a FINEX® plant, which is removed as export gas  12 , lies at 1300-1800 kcal/Nm 3 . The joule value needed for the gas turbine  28  lies in the region of the joule value of the export gas and the typical, permissible fluctuation margin of the joule value for 1300 kcal/Nm 3  lies at +/−20 kcal/Nm 3 . In this case the predefined minimum joule value would amount to 1280 kcal/Nm 3  and the predefined maximum joule value to 1320 kcal/Nm 3 . The joule value needed for the gas turbine  28  depends on the type of gas turbine. 
         [0084]    The export gas mixed with tail gas is purified as a precaution before the gas turbine  27  and, if necessary, after the buffer container  25  in a separator  26  for solids. 
         [0085]      FIG. 2  shows a connection between a FINEX® plant, on the one hand, and a combined cycle power plant  24  together with upstream export gas containers  13 , on the other hand, wherein the latter are constructed exactly the same as those in  FIG. 1 . 
         [0086]    The power station  24  is supplied with export gas  12  by a FINEX® plant, which can be temporarily stored in an export gas container  13 . Export gas  22  that is not needed for the power station  24  can again be supplied to the smelter gas distribution network, for example to drying raw material. 
         [0087]    In this example, the FINEX® plant has four reduction reactors  37 - 40 , which are formed as fluidized bed reactors and are loaded with fine ore. Fine ore and additives  41  are supplied for drying the ore  42  and, from there, firstly to the fourth reactor  37 , then they reach the third  38 , the second  39  and finally the first reduction reactor  40 . Instead of four fluidized bed reactors  37 - 40 , there could also be only  3  present. 
         [0088]    The reduction gas  43  is led in the counter flow to the fine ore. It is introduced at the floor of the first reduction reactor  40  and is emitted from the upper side thereof. Before it enters the second reduction reactor  39  from below, it can be further heated with oxygen O 2 , as well as between the second  39  and third  38  reduction reactors. 
         [0089]    The offgas  44  from the reduction reactors is purified in a wet scrubber  47  and further used as export gas  12  in the downstream combined cycle power plant  24 , as described above. 
         [0090]    The reduction gas  43  is produced in a smelter gasifier  48 , in which on the one hand coal in the form of lumps of coal  49  and of coal in powder form  50 —this together with oxygen O 2 —is supplied, in which, on the other hand, the iron ore is added, which is pre-reduced in the reduction reactors  37 - 40  and formed into hot compacted iron (HCI) in the iron compacting  51 . In the process, the compacted iron reach a storage container  53  via a conveyer system  52 , which is formed as a fixed bed reactor, where the compacted iron is, if necessary, preheated and reduced with roughly purified generator gas  54  from the smelter gasifier  48 . Here, cold compacted iron  65  can be added. Subsequently, the compacted iron or iron oxides are charged from above in the smelter gasifier  48 . Low reduced iron (LRI) can equally be removed from the iron compacting  51 . 
         [0091]    The coal in the smelter gasifier  48  is gasified, which produces a gas mixture which is mainly CO and H 2 , and is removed as a reduction gas (generator gas)  54  and partial flow is supplied to the reduction reactors  37 - 40  as a reduction gas  43 . The hot metal, which is smelted in the smelter gasifier  48 , and the slag are removed, see arrow  58 . 
         [0092]    The generator gas  54 , which is removed from the smelter gasifier  48 , is firstly led into a separator  59 , in order to be removed with delivered dust and in order to recirculate the dust in the smelter gasifier  48  via dust burners. A part of the generator gas purified by rough dust is further purified by a wet scrubber  60  and extracted as excess gas  61  from the FINEX® plant. A part can also be supplied to the PSA plant  14 . 
         [0093]    A further part of the purified generator gas  54  is equally further purified in a wet scrubber  62 , supplied to a gas compressor  63  for cooling and then supplied again to the generator gas  54  for cooling after the smelter gasifier  48 , after being mixed with the product gas  64 , which is extracted from the PSA plant  14  and rid of CO 2 . Through this recirculation of the gas  64 , rid of CO 2 , the reducing components, which are contained therein, can still be used for the FINEX® process and, on the other hand, the required cooling of the hot generator gas  54  from around 1050° C. to 700-870° C. can be ensured. 
         [0094]    The top gas  55  emitted from the storage plant  53 , where the compacted iron or iron oxides are heated and reduced with de-dusted and cooled generator gas  54  from the smelter gasifier  48 , is purified in a wet scrubber  66  and then equally at least partially supplied to the PSA plant  14  for the removal of CO 2  and at least partially added to the offgas  44  from the reduction reactors  37 - 40 . The gas supply line to the storage plant  53  can also be omitted. 
         [0095]    A part of the offgas  44  from the reduction reactors  37 - 40  can also be added directly to the PSA plant  14 . The gases, which are supplied to the PSA plant  14  are compressed beforehand in a compressor  15 . 
         [0096]    The tail gas  20  from the PSA plant  14  can be added completely or partially to the export gas  12  or added to the smelter gas distribution network via the export gas  22  that is not needed, or supplied to the hot flare  19  for combustion, as has already been described in  FIG. 1 . The construction and function of the plant from the export gas container  13  onwards are equally covered by that of  FIG. 1 . 
         [0097]      FIG. 3  shows the connection between a plant for smelting reduction on the one hand, and an export gas container  13  with a combined cycle power plant  24  on the other hand, wherein the latter are constructed exactly the same as those in  FIG. 1 . 
         [0098]    The power station  24  is supplied with export gas  12  by a COREX® plant, the export gas  22  being able to be temporarily stored in an export gas container  13 . Export gas  22  that is not needed for the power station  24 , can be once again supplied to the smelter gas distribution network, for example, for drying raw materials. 
         [0099]    In this example, the COREX® plant has a reduction shaft  45 , which is formed as a fixed bed reactor and is loaded with lump ore, pellets, sinter and additives, see reference sign  46 . The reduction gas  43  is led in the counter flow to the lump ore  46  etc. It is introduced at the floor of the reduction shaft  45  and emitted at the upper side thereof as top gas  57 . The top gas  57  from the reduction shaft  45  is further purified in a wet scrubber  67  and a part is extracted from the COREX® plant as export gas  12  and a part is rid of CO 2  and supplied once again to the reduction shaft  45  via the PSA plant situated in the COREX® plant. 
         [0100]    The reduction gas  43  for the reduction shaft  45  is produced in a smelting gasifier  48 , into which, on the one hand, coal in the form of lumps of coal  49  and coal in powder form  50 —this together with oxygen O 2 —is supplied, into which, on the other hand, the iron ore, which is pre-reduced in the reduction shaft  45 , is added. 
         [0101]    The coal in the smelter gasifier  48  is gasified, which produces a gas mixture, which is mainly CO and H 2 , and is removed as top gas (generator gas)  54 , and a partial stream is supplied to the reduction shaft  45  as reduction gas  43 . The hot metal smelted in the smelter gasifier  48  and the slag are removed, see arrow  58 . 
         [0102]    The generator gas  54 , which is removed from the smelter gasifier  48 , is led into a separator  59 , in order to be removed with delivered dust and in order to recirculate the dust in the smelter gasifier  48  via a dust burner. 
         [0103]    A part of the top gas  54 , which is purified by rough dust, is further purified by a wet scrubber  68  and extracted as excess gas  69  from the COREX® plant and added to the top gas  57  or to the export gas  12 . 
         [0104]    A part of the purified top or generator gas  54  after the wet scrubber  68  is supplied to a gas compressor  70  for cooling and then further supplied to the top or generator gas  54  after the smelter gasifier  48  for cooling. Through this recirculation the reducing components contained therein can still be used for the COREX® process and, on the other hand, the required cooling of the hot top or generator gas  54  from approx. 1050° C. to 700-900° C. can be ensured. 
         [0105]    A part of the top gas  57 , which can also contain excess gas  69 , is compressed by a compressor  15  and cooled in an after-cooler  16 , before it is supplied to the PSA plant  14 . The product gas from the PSA plant  14 , which is rid of CO 2 , is at least partially supplied to the cooled gas after the wet scrubber  68  and therefore again to the generator gas  54 . 
         [0106]    The product gas from the PSA plant  14 , which is rid of CO 2 , can, if necessary, also be partially heated in a heating unit  71  and added to the reduction gas  43 , and after the addition of generator gas  54 . A part of the top gas  57  can, however, also be heated in the heating unit  71  and then added to the reduction gas  43 . 
         [0107]    Here, the tail gas  20  is again at least partially supplied to the export gas  12  before the export gas container  13  and mixed with this. It could also—completely or partially—either be released once more into the atmosphere after a H 2 S purification and/or can be supplied to a further compressor to liquefy CO 2 , in order to then transport it and to store it, for example underground, or in order to use it as a replacement for nitrogen in the iron production. 
         [0108]    The pressure of the export gas  12  after the supply line for tail gas  20  is measured with a pressure gauge  17  and a valve  18  in the line  21  for export gas to the hot flare  19  is actuated depending on the measured pressure or on the level of the export gas storage: if the pressure of the export gas  12  exceeds a predefined pressure or a predefined level in the export gas storage, then at least a part thereof is led to the hot flare  19  and combusted there, and the rest continues into the export gas container  13 . 
         [0109]    The export gas from the export gas container  13  is supplied to a combined cycle power plant  24  as fuel, and optionally via a buffer container  25  and optionally via a filter  26 . The export gas is supplied to a gaseous fuel compressor  27  and then to the gas turbine  28 . The waste heat from the gas turbine is used in the waste heat boiler  29  for a steam circulation with a steam turbine  30 . 
         [0110]    The plant and the function of the plant according to  FIG. 3  after the removal of the export gas from the COREX® plant are the same as those from  FIG. 1 . 
         [0111]    In  FIG. 3  a regulating valve  72  is additionally provided for export gas  12 , with which the quantity of export gas  12 , which is extracted from the COREX® plant, can be regulated. 
         [0112]    If the process is used on the synthesis gas of a plant for synthesis gas production, this takes the place of the plant for iron production in the exemplary embodiments above. At least a part of the synthesis gas then forms the export gas, for which no export gas container  13  is provided and the joule value of which is regulated by adding tail gas from a CO 2  removal plant situated in the plant for synthesis gas production. The corresponding plant, having supply lines  33 ,  34  for gaseous fuel and non-combustible gas and having a power station  24 , is then the same for the synthesis gas as that from the  FIGS. 1-3 . The CO 2  rich tail gas from the CO 2  removal plant must be compressed to the export gas pressure (=synthesis gas pressure) by a compressor for the addition to the export gas. 
         [0113]    A description has been provided with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the claims which may include the phrase “at least one of A, B and C” as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in  Superguide v. DIRECTV,  358 F3d 870, 69 USPQ2d 1865 (Fed. Cir. 2004).