Abstract:
The present invention relates to a fuel system and to a process for the production of such a fuel system. The fuel System according to the present invention consists of at least two different fossil regular fuels and at least one biogenic carbon carrier, wherein the amount of the biogenic carbon carrier is at least 20% with respect to the total mass. Thus the emission of the carbon dioxide based on fossil carbon is notably reduced during the use of the fuel system according to the invention.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. National Stage Application of International Application No. PCT/EP2009/005964, filed Aug. 18, 2009. This application claims the benefit of European Patent Application No. 08014604.6, filed Aug. 18, 2008. The disclosures of the above applications are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a fuel System and to a process for the production of a fuel System according to the invention. 
         [0004]    2. Discussion 
         [0005]    Fuels generally serve as an energy carrier in the production of heat or electric current, from prior art, a number of different fuels are known among which the so-called fossil fuels predominate. 
         [0006]    Brown coal, black coal, turf, natural gas and petroleum are part of the fossil fuels which have developed as decomposition products from dead plants and animals in the course of the history of the Earth. Fossil fuels are based on the carbon cycle and contain carbon as a primary energy carrier. While the worldwide energy demand is currently satisfied for up to 81% by fossil fuels, estimates say that in the coming 25 years approximately up to 90% of the energy demand will be covered by fossil fuels. 
         [0007]    Fossil fuels have been exploited already since the 18 th  and 19 th  centuries, and they were considered as the basis for the industrial Revolution. Particularly during the past 40 years, the worldwide energy demand and hence the consumption of fossil fuels have increased to such an extent that the production of energy from fossil fuels has caused environmental problems. 
         [0008]    Fossil fuels are generally based on organic carbon compounds which release energy in the form of heat during the oxidative conversion with oxygen, as this takes place during combustion. Carbon dioxide is generated as a byproduct of this oxidative conversion. 
         [0009]    Since carbon dioxide which is released during the combustion of fossil fuels originates from carbon compounds that have been stored over millions of years, this massive combustion results in the enrichment of the earth&#39;s atmosphere with carbon dioxide. 
         [0010]    On the other hand, this carbon dioxide is frequently referred to as a so-called “greenhouse gas” which could contribute to disturbing the ecological balance on the earth. Carbon dioxide in the atmosphere is suspected to reduce the radiation of heat energy from the earth to the universe just as the glass roof of a greenhouse while the incidence of the sun&#39;s radiation on the earth is reduced only little. This effect is suspected to lead to global warming. 
         [0011]    For controlling the emission of CO 2  to the atmosphere, climate-protection goals have been fixed by the European Union in consideration of the Kyoto Protocol, and in this connection there have even been introduced so-called Emission Certificates. Since 2005, the EU membership states are obliged by the EU Emissions Trading Directive to hand in a National Allocation Plan each time at the beginning of an emissions trading period. This plan fixes an amount of greenhouse gases each bigger emitter of a country is allowed to emit within a particular period. Article 9 of these Directives provides the examination and approval of this Allocation Plan by the EU Commission on the basis of 12 criteria. This concerns above all the compatibility of a country&#39;s own goals within the scope of the Kyoto Protocol, equal treatment of enterprises and the observance of the EU competitive law. If a company&#39;s emission exceeds the allowance that has been allocated to it, the company has to buy additional emission rights from another company. This can be done for instance at the Energy Exchange EXXA. On the other hand, if a company emits less than the allowance that has been allocated to this company, it may sell excess amounts of emission to other companies. However, for in fact reducing the fraction of CO 2  in the atmosphere, the allowed emissions are reduced step by step. 
         [0012]    Major emitters of CO 2  are branches in industry and economy having a high energy demand. These are for instance power plants, petroleum refineries, coking plants, iron and steel works, the cement industry, glass industry, lime industry, brick industry, insulation material industry, ceramic industry, and cellulose and paper industry. 
         [0013]    One way for avoiding the accumulation of CO 2  in the atmosphere is the use of the so-called regenerative energy. In general, these are wind power, water power, solar power and the use of biomasses as a fuel and for the production of bio gas. However, if biomasses are used as an energy carrier, the problem exists that these biomasses have a clearly lower energy content compared to fossil fuels. On the other hand, biomasses have the advantage that they are extracted as an energy carrier from the current carbon cycle. This means, that on a scale of Earth history, carbon dioxide which is released as a result of the oxidative conversion of biomasses was generated only a short time ago and is also directly extracted again from the carbon cycle by the regrowing plants, if the biomasses are simultaneously planted again. Thus a carbon dioxide balance is achieved, and the accumulation of carbon dioxide in the atmosphere is avoided. 
         [0014]    However, due to their clearly lower energy content, fuels based on biomasses as known from prior art cannot be used up to present with sufficient efficiency in the big industry. Moreover, the use of biomasses as a fuel requires fuel technologies which are different from those employed in the combustion of fossil fuels such as black coal or brown coal for instance. This means that the release of a defined amount of energy would require the combustion of a clearly higher amount of biomasses than of fossil fuels on one side and that the use of biomasses as a fuel on an industrial scale would require an expensive modification of already installed fueling Systems on the other side. 
         [0015]    Apart from their energy content, biomasses which are used as a fuel are different from fossil fuels also with regard to further properties such as ash content, volatile matters, hydrogen content and water content. But all these factors play an important part in the industrial use of fuels in dependence of the respective application, so that frequently it is not possible to exchange fossil fuels for biomasses as a fuel in the field of industrial applications. 
       SUMMARY OF THE INVENTION 
       [0016]    The invention is therefore based on the object of providing a fuel which is ecologically more favorable on one side and which can be unlimitedly exploited for industrial applications on the other side. It is also an object of the present invention to provide a process for the production of such a fuel. 
         [0017]    Concerning the fuel, this object is achieved by a fuel system which is characterized in that it consists of a mixture of at least two different fossil regular fuels and at least one biogenic carbon donor, wherein the amount of the biogenic carbon donor is at least 20% with respect to the total weight. 
         [0018]    The fuel system according to the invention advantageously consists of at least two different fossil regular fuels and at least one biogenic carbon donor. 
         [0019]    Biogenic carbon donors in terms of the invention are generally understood to mean biomasses. Particularly suitable as biogenic carbon donors are regrowing raw materials like wood, natural fiber, vegetable oils, sugar, starch, dried vegetables and cereals. 
         [0020]    Fossil regular fuels which are preferably used in the fuel system according to the invention are brown coal, black coal and/or anthracite. 
         [0021]    In an embodiment of the inventive fuel system, the first fossil regular fuel has a vitrinit reflection Rm of &gt;2.0, whereat the second regular fuel has a vitrinit reflection Rm between of 0.4 to 2.0. 
         [0022]    The vitrinit reflection Rm gives an information about the maturity and the calorification of the fossil regular fuel used. Furthermore, the vitrinit reflection is associated with the combustion behaviour of the deployed fossil regular fuel so that an optimization of the combustion behaviour of the fuel system is possible by choosing fossil regular fuels having a vitrinit reflection parameter within the specified range. Thereby, the combustion behaviour of the inventive fuel system can be adapted to the combustion behaviour of pure fossil fuels, like they are typically used in e.g. powerplanes, whereat as combustion behaviour in particular the fuel value, the calorific value, as well as the ash residue should be understood. This enables the use of the inventive fuel system in existing firing systems without further plant specific modification. Hence, the inventive fuel system enables an ecological optimization of the firing systems without the need to make plant specific modifications. 
         [0023]    According to a further embodiment of the inventive fuel system, at least three fossil regular fuels are used, whereat one having a vitrinit reflection Rm&gt;3.0, a second having a vitrinit reflection Rm within the range of &gt;2.0 and 3.0, and the third has a vitrinit reflection Rm within the range of 0.4 and 2.0. 
         [0024]    This further embodiment of the inventive fuel system enables in particular a adaption of the hardgrove index, so that the fuel system can be adapted with respect to this parameter to the plant specific conditions, like e.g. coal mills, too. 
         [0025]    Additionally, this embodiment enables a meticulous adaption of the sulfur content of the fuel system, so that the fuel system can be adapted to the plant specific conditions with respect to the sulfur content, like e.g. flue gas desulfurization systems. 
         [0026]    The fuel system according to the invention provides a fuel which meets the requirements of fossil fuels concerning its fuel-technological properties while showing a clearly lower emission of CO 2  from fossil carbon carriers, based on the releasable energy content. 
         [0027]    The biogenic carbon carrier fraction in the fuel system according to the invention is at least 20% by weight, referred to the total mass. 
         [0028]    Thus the fuel system shows an effective content of fossil carbon which is reduced by at least 11% compared to fossil fuels, referred to the calorific value, with the percentage of fossil fuels being put in a relation to the calorific value for calculating the effective content of fossil carbon. 
         [0029]    In a further embodiment of the inventive fuel system, the fuel system comprises beside the fossil fuel and the biogenic carbon carrier a refining product of the group consisting of coke, petrol coke, lignite coke, and charcoal. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0030]    An embodiment of a process for producing a fuel system of the above-described kind comprises the steps of:
   1. selecting a first fossil regular fuel having a low content of volatile matters, and a vitrinit reflection Rm&gt;2.0, a second fossil regular fuel having a medium content of volatile matters, and a vitrinit reflection Rm between 0.4 and 2.0, and a biogenic carbon carrier;   2. mixing the first fossil regular fuel with the second fossil regular fuel;   3. mixing the mixture obtained in step 2 with the biogenic carbon carrier;
 
wherein in Step 3 20% by weight, with respect to the total mass, of the biogenic carbon carrier is admixed to the mixture obtained in step 2.
   
 
         [0034]    Preferably, the selected first regular fuel includes a volatile water and ash-free fraction (waf)≦10% by weight. Appropriate regular fuels of this kind are, e.g. anthracite and/or lean coal. 
         [0035]    Preferably, the selected second regular fuel includes a volatile water and ash-free fraction between &gt;10% by weight and &lt;40% by weight. Suitable regular fuels of this kind are for example forge coal, fat coal, gas coal, long-flame coal, bituminous coal, pre-dried black lignite or pre-dried dull brown coal, 
         [0036]    As biogenic carbon carriers solid biomasses, for example wood, wood pellets, wood chips, natural fibers, cereals, sugar and or dried vegetables are admixed in step 3 of the process according to the invention. 
         [0037]    In a further embodiment of the inventive method, the first fossil regular fuel is obtained by mixing two fossil regular fuels having different vitrinit reflections prior to step 1, whereat one fossil regular fuel has a vitrinit reflection Rm&gt;3.0 and the other fossil regular fuel has a vitrinit reflection Rm between &gt;2.0 and 3.0. 
         [0038]    A further embodiment of the invention can provide that the solid biomasses are impregnated with a substantially liquid biogenic carbon carrier, such as e.g. vegetable oils, vegetable fat and/or alcohol, before being admixed to the mixture of fossil regular fuels obtained in step 2. Alternatively, it can be provided that a substantially liquid biogenic carbon carrier is admixed to the mixture of regular fuels and biogenic carbon carriers obtained in step 3. 
         [0039]    For avoiding agglutination or adhesion during the transportation or conveying of the fuel System, one embodiment of the invention may provide that the fuel System obtained by the process according to the invention is finally mixed with a dust or a powdery additive. Such additives can be sawdust, legume shred or coal dust. The addition of such an additive avoids agglutination or adhesion of the fuel system especially in the case of adding substantially liquid biogenic carbon carriers, and the fuel system which is obtained further remains in an absolute condition for its transportation and conveying in the usual prior art facilities. The fuel System according to the invention which has been obtained by the process according to the invention is particularly suitable for power plant fueling in electric power and/or heat production, for paper production, for the production of glass and mineral melts, and as a domestic fuel. 
         [0040]    The fuel system according to the invention and the process for its production are described in the following by way of examples which are not in any way limiting to the invention. 
         [0041]    In the following table 1, examples of the main characteristics of different fossil fuels and biogenic carbon carriers are shown. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                   
                 anthracite 
                 fat  
                 wood 
               
               
                 Parameter (raw) 
                 coal 
                 coal 
                 pellets 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 water in % by weight 
                 4.00 
                 ′9.01 
                 8.00 
               
               
                 ash in % by weight 
                 8.50 
                 20.50 
                 0.46 
               
               
                 volatile matters in % by weight 
                 5.20′ 
                 21.26 
                 78.20 
               
               
                 sulfur in % by weight 
                 1.60 
                 0.93 
                 0.06 
               
               
                 hydrogen in % by weight 
                 2.50 
                 3.05 
                 5.87 
               
               
                 carbon in % by weight 
                 80.25 
                 57.85 
                 46.00 
               
               
                 fuel value Ho J/g 
                 30675 
                 22705 
                 18216 
               
               
                 calorific value Hu J/g 
                 30027 
                 21833 
                 17645 
               
               
                 calorific value Hu cal/g 
                 7172 
                 5215 
                 3999 
               
               
                   
               
             
          
         
       
     
       Example 1 
       [0042]    33% by weight of a low volatile anthracite coal were mixed with 33% by weight of a medium volatile fat coal in a mixing drum, until a homogeneous mixture was obtained. 33% by weight of wood pellets were added to the obtained mixture in the mixing drum, and mixing was continued, until a substantially homogeneous mixture was obtained. In the analytical examination the obtained mixture showed a water content of 7.00% by weight, an ash content of 9.8% by weight, a volatile material fraction (waf) of 34.89% by weight, a sulfur content of 0.86% by weight and a total carbon content of 61.37% by weight, with 46.03% by weight of the total carbon content of 61.37% by weight being fossil carbon and 15.33% by weight being biogenic carbon. The obtained mixture showed a fuel value H 0  of 23865 J/g and a calorific value Hu of 5462 cal/g. 
         [0043]    The obtained mixture showed an excellent combustion behavior and could be combusted in a stoker-fired furnace previously operated with fossil fuels, without any modification of the Installation. 
         [0044]    Referred to the energy content of anthracite coal, the mixture contained a fossil carbon fraction that was less by 20.11%. Compared to the energy content of a medium volatile fat coal, the mixture showed a content of fossil carbon that was less by 13.94%. 
       Example 2 
       [0045]    In the manner described in example 1, 40% by weight of a low volatile anthracite coal were mixed with 30% by weight of a medium volatile fat coal and 30% by weight of wood pellets as a biogenic carbon carrier. The obtained mixture showed a wafer content of 6.70% by weight, an ash content of 9.69% by weight, a volatile matter fraction (waf) of 31.92% by weight, a sulfur content of 0.94% by weight, and a hydrogen content of 3.68% by weight. The total carbon fraction in the mixture amounted to 63.26% by weight, with 49.46% by weight thereof being fossil carbon and 13.80% by weight thereof being biogenic carbon. The mixture achieved a fuel value H 0  of 24546 J/g and a calorific value Hu of 5633 cal/g. Referred to the calorific value of anthracite coal, the mixture showed a fossil carbon fraction that was reduced by 17.28% and by 12.06% referred to a medium volatile fat coal. 
       Example 3 
       [0046]    In the manner described in the examples 1 and 2, 60% by weight of a low volatile coal were mixed with 10% by weight of a medium volatile coal and 30% by weight of a biogenic carbon carrier. The obtained mixture showed a water content of 5.70% by weight, an ash content of 7.29% by weight, a volatile matter fraction (waf) of 28.71% by weight, a sulfur content of 1.07% by weight and a hydrogen content of 3.57% by weight. The total carbon content amounted to 67.74%) by weight, with 53.94% by weight thereof being fossil carbon and 13.80% by weight being biogenic carbon. The mixture achieved a fuel value H 0  of 26140 J/g and a calorific value Hu of 6024 cal/g. Compared to the low volatile coal, the mixture showed a fossil carbon content that was reduced by 16.06% and compared to the medium volatile coal a fossil carbon content that was reduced by 11.18%.