Abstract:
A plant for producing cement clinker from calcium carbonate-containing raw meal. A preheating stage preheats the raw meal, which preheating stage is heated by exhaust gases from a following sintering stage. A stage is provided for deacidification and sintering of the raw meal. A cooling stage for the sintered meal is of at least two-stage design and has a gas separation stage for separating exhaust gases from the deacidification and sintering stage which is routed in a first gas circuit from the cement clinker cooling gas. A gas/gas heat exchanger is arranged downstream of the preheating stage in the gas flow direction, through which heat exchanger heat from the combined exhaust gases which leave the preheating stage is transferred into a gas, extracted from the gas for cooling the cement clinker, routed in a second gas circuit, for drying the raw meal in a preceding grinding stage.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This is a Divisional application of U.S. Ser. No. 13/394,605 filed Mar. 7, 2012 which was a 371 of PCT/EP/2010/061748 and claiming priority to DE 10 2009 041 089.9 filed Sep. 10, 2009. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to methods for producing cement clinker, having the following steps: preheating calcium carbonate-containing raw meal in a preheating stage which is heated by exhaust gases from a sintering stage which follows in the gas flow direction, deacidifying the preheated raw meal, sintering the deacidified raw meal into cement clinker in a sintering stage, cooling the cement clinker from the sintering stage in a cooling stage which cools the cement clinker by means of a gas. 
     In the methods for producing cement which are carried out most often throughout the world, a calcium carbonate-containing initial material in the form of limestone is freed of CO2 formally by the supply of heat and is thereby converted into unslaked lime, calcium oxide, and is subsequently sintered by the supply of even more heat, in the presence of silicate-containing rock, into cement clinker which is composed of various calcium silicate phases and constitutes the principal fraction of customary cement. In this case, heat energy of between 2850 and 3350 kJ is used per kg of cement clinker. The heat quantity required for this purpose is usually generated from the combustion of carbon-containing fuel. Combustion, on the one hand, and the formal freeing of CO2 from the limestone, on the other hand, together form an intensive CO2 source, the released CO2 hitherto being introduced into the free earth&#39;s atmosphere. The CO2 emission thereby generated makes an appreciable contribution to the overall anthropogenic CO2 emission on earth. It is known since then that CO2 is the main cause of an anticipated greenhouse effect which leads to the undesirable warming of the earth&#39;s atmosphere. The endeavor, therefore, is to reduce the CO2 emission substantially. 
     In order to reduce the introduction of CO2 into the earth&#39;s atmosphere due to the production of cement, it is necessary to rely on preventing the released CO2 from escaping into the earth&#39;s atmosphere by storing it in underground caverns. Such caverns are, for example, natural gas or petroleum deposits which have for the most part been emptied. Since, in the conventional method for producing cement, very large quantities of CO2 occur, which are mixed with even much larger quantities of nitrogen from atmospheric air, storage, along with compressing the exhaust gas and transferring it to the deposit, is scarcely possible in economic terms. 
     In the hitherto known method for producing cement, it is customary to fine-grind the calcium carbonate-containing initial material into what is known as raw meal and then first to heat it in a preheater. In the preheater, the raw meal falls in countercurrent to the gas flow direction through the hot exhaust gases of a cylindrical rotary kiln, in order first to heat by the waste heat the large quantities of limestone to be burnt. Depending on the configuration of the plant, there is then provision for deacidifying the raw meal in a cylindrical rotary kiln and sintering it into limestone in one step or for carrying out deacidification and sintering in separate plant parts. The gases which heat the raw meal and are composed of nitrogen, CO2, small quantities of CO, nitrous gases and further combustion gases are then, in many plants, conducted through a heat exchanger to separate the heat still remaining in the exhaust gases and are then released into the free earth&#39;s atmosphere. 
     Since the exhaust gas quantities occurring in order to prevent CO2 emission are very large, European patent application EP 1 923 367 A1 proposes to modify the hitherto known method for producing cement. According to the proposal of the last-mentioned patent application, preheating and deacidification are to be carried out in spatially separate regions of the plant, the exhaust gases from deacidification being circulated, along with a high degree of enrichment of CO2, so that deacidification is carried out in a CO2 atmosphere. The chemical balance lies in this case on the side of unslaked lime due to the heat introduced. By contrast, as is known, the exhaust gases from a cylindrical rotary kiln are used to preheat the raw meal and are then discarded by being released. In order to utilize the residual heat from the cylindrical rotary kiln exhaust gases after heat exchange with the raw meal, the last-mentioned patent application proposes to cool down the exhaust gas with the aid of a heat exchanger in favor of heating water for energy generation, during which steam occurs in the second circuit of the heat exchanger and is to be used for driving steam turbines. 
     The method referred to in the last-mentioned patent application therefore still causes the CO2 occurring during the combustion of carbon-containing fuels to escape into the atmosphere, approximately 40% of the entire fuel burnt in the plant usually being converted in the cylindrical rotary kiln. It would be ideal if the CO2 escaping here could also be captured and stored. 
     SUMMARY OF THE INVENTION 
     The object of the invention, therefore, is to increase further the degree of separation of the CO2 emissions occurring in the overall process, in order thereby to reduce the CO2 emission further. 
     The object according to the invention is achieved by combining the exhaust gases from the sintering stage with the exhaust gases from deacidification and by routing the combined exhaust gases in the open gas circuit. 
     Since both CO2 gas sources are routed in the open gas circuit, to be precise the occurrence of CO2 during deacidification, together with the occurrence of CO2 from heat generation necessary for this purpose, on the one hand, and the occurrence of CO2 from heat generation for sintering, on the other hand, it is possible to separate and store the entire CO2 emission of a plant for producing cement. Besides, including the exhaust gases from the cylindrical rotary kiln, too, has a further advantage, to be precise that nitrous gases called nitrogen oxides or else NOx, which occur during the upgrading of CO2 in the circuit necessarily reduce the concentration of atmospheric nitrogen in the circuit gas. Since less atmospheric nitrogen is present in the cylindrical rotary kiln during the generation of heat, much less atmospheric nitrogen is also burnt into nitrous gases during combustion. The occurrence of nitrous gases is much more pronounced in the cylindrical rotary kiln than during combustion in the deacidification stage, because oxidative conditions are necessary in the cylindrical rotary kiln for the desired formation of various desired calcium silicate phases as cement clinker, and under these conditions nitrogen is unavoidably oxidized into nitrous gases in the great heat of the cylindrical rotary burner. 
     However, combining the exhaust gases from the deacidification stage and the sintering stage is not possible without further changes to the known method. An apparently obvious solution, to be precise simply to include the exhaust gases from the cylindrical rotary kiln additionally into the circuit, is not readily possible for further plant-related reasons, since the exhaust gases from the preheater are used as lifting and drying air in a raw meal mill preceding the plant for producing cement clinker from raw meal. The initial material from which raw meal for producing cement clinker is generated is usually moist, for example because it comes from open cast mining, but also contains hydration water. In order, during preheating, to avoid the energy-intensive heating of entrained water, and also to facilitate the grinding process, using sifters, even during grinding care is taken to ensure that the raw meal is dry by using the preheater exhaust air in the grinding process. The grinding process is not a closed process, which means that there are many places in the grinding process where the initial material is in free contact with the earth&#39;s atmosphere during crushing. If, therefore, the exhaust gases from the cylindrical rotary kiln were included in the circuit, these would be absent during the required grinding. As a solution, it would therefore be necessary to seal off the grinding process with respect to infiltrated air, thus demanding a high outlay in terms of very complicated apparatus, or use is made here of a special variation, according to the invention, of the hitherto known method for producing cement. 
     So that the heat coming from the preheater for preheating the raw meal can be utilized for drying the initial material, it is proposed, according to the invention, to use an at least two-stage cooler for the ready-burnt cement clinker which cooler has between the two stages, for example, a middle crusher, by means of which gas separation of the two gas circuits is possible. The first stage of the cooler is included in the open gas circuit in which a highly CO2-enriched gas atmosphere is present. However, the second stage of the cooler operates with atmospheric air, as in known plants, the cooler exhaust air of this part being used for lifting and drying the initial material in the grinding stage. However, since the cooler exhaust air of the second grinding stage does not carry sufficient heat with it to dry the entire initial material, the heat from the preheater is used to reheat the cooler exhaust air conducted as grinding circulation air into the grinding circuit, after this cooler exhaust air from the grinding stage is cooled, with moisture from the initial material at the same time being absorbed. The invention therefore makes use of the fact that, on the one hand, in the method according to the invention and in the corresponding plant, heated atmospheric air from the second cooler stage is available, which is not laden with exhaust gases, in particular with CO2, and, on the other hand, the invention utilizes the heat from the preheating stage, which cannot readily be supplied to the grinding stage by being included in a dedicated open circuit, along with the enrichment of the CO2 concentration, because an undesirable introduction of infiltrated air would take place there and would reduce the effectiveness of the method with separation of CO2. 
     A particular feature of the method according to the invention is that it is suitable both for the conversion of those plants in which deacidification and sintering take place in a single stage, a longer cylindrical rotary kiln, and for plants in which sintering and deacidification take place is spatially separated plant parts. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in more detail by means of the following figures in which: 
         FIG. 1  shows a sketch of a plant according to the invention for carrying out the method according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates a sketch of a flow diagram of a plant  1  according to the invention for producing cement clinker from calcium carbonate-containing initial material, which plant has two essential open gas circuits  5  and  10  separate from one another. The calcium carbonate-containing initial material for producing cement clinker runs through these two separate open gas circuits  5  and  10 , at the same time traveling in the gas flow direction in the first open gas circuit  5  and for the most part flowing through the plant part in counter current in the second open gas circuit  10 , the material flow of the calcium carbonate-containing initial material in the gas circuit  10  therefore being for the most part opposite to the gas flow direction. 
     A gas stream for drying the calcium of carbonate-containing initial material and for crushing it into raw meal in a grinding stage  15  preceding a preheating stage  35  flows in the first open gas circuit  5  which is separated from the second open gas circuit  10 , the preheating stage  35  following the grinding stage  15  in the material flow direction of the plant  1 . 
     By contrast, a gas stream, in which the calcium carbonate-containing raw meal from the first open gas circuit  5  is converted into cement clinker, flows in the second open gas circuit  10  of the plant  1 . 
     In the overall plant  1 , to produce cement clinker from calcium carbonate-containing raw meal, the calcium carbonate-containing initial material, usually a mixture, still moist from open cast mining, of limestone and of silicate-containing rock, is first fed to a grinding stage  15  at the feed point  20   a . The sketch illustrates a vertical meal as a grinding stage  15 , but, depending on the material properties of the calcium carbonate-containing initial material, roller presses for high-pressure crushing, or circulatory grinding plants with various grinding and sifting stages are also suitable as a grinding stage  15 . In the grinding stage  15 , the calcium carbonate-containing initial material is simultaneously crushed into calcium carbonate-containing raw meal to an extent such that it has a meal-like consistency and is dried by the dry cooler exhaust air  23  coming from the right at the point  22  of the grinding stage  15  in the sketch. In this case, the calcium carbonate-containing initial material to be crushed is lifted in the grinding stage  15  by the dry cooler exhaust air  23  introduced as grinding circulation air  23 ′, sifters, not depicted here, also being present within the grinding stage  15  and discharging the calcium carbonate-containing raw meal out of a grinding circuit only beyond a specific degree of fineness. After the calcium carbonate-containing raw meal has left the grinding stage  15  at the point  25  with the aid of the partially dry cooler exhaust air  23  and partially moist grinding circulation air  23 ′, it is separated from the then cooled and moist grinding circulation air  23 ′ in a cascade  26  of dust separators. At this point, the path of the calcium carbonate-containing raw meal separates from the cooled and moist grinding circulation air  23 ′ located in the open gas circuit  5 . 
     The largely dust-free moist grinding circulation air  23 ′ leaves the cascade  26  of dust separators in an upward direction and is compressed by a compressor  27  in order to compensate for the pressure drop in the following gas/gas heat exchanger  30  and the part gas outlet  28 . Since part of the moist grinding circulation air  23 ′ is extracted at the point  28   b  between the compressor  27  and gas/gas heat exchanger  30 , in order to discard the moisture from the calcium carbonate-containing initial material together with the extracted moist grinding circulation air  23 ′, and also to keep constant the gas quantity which is located in the first gas circuit  5  and which is replaced continually by new atmospheric air from the cooler air supply  28   a . However, gas loss and gas introduction in the first gas circuit  5  not only take place as a result of the extraction of the moist grinding circulation air  23 ′ at the point  28   b  and the cooler air supply  28   a , but also by means of the introduction and discharge of infiltrated air in the grinding stage  15 . Since infiltrated air is introduced into the first gas circuit  5  in the grinding stage  15 , but also moist grinding circulation air  23 ′ escapes from the first gas circuit  5 , only as much moist grinding circulation air  23 ′ is extracted between the compressor  27  and gas/gas heat exchanger  30 , as mentioned above, as is necessary for the gas quantity located in the gas circuit  5  to remain constant, since it is constantly replaced by warm and still dry cooler exhaust air  23  at the point  22 , the dry cooler exhaust air  23  coming from the second stage  45   b  of the two-stage cooler  45  in which the almost ready cement clinker is cooled by means of atmospheric air. This atmospheric air is introduced into the plant at the point  28   a . The open gas circuit  5  described here is open, which means that new gas, cooler exhaust air  23 , is introduced into the open gas circuit  5  and gas, moist grinding circulation air  23 ′, leaves the open gas circuit  5 . In this case, in the context of this disclosure, an “open gas circuit” is understood to mean a gas circuit which is continuously fed with gas and freed of gas, and also a gas circuit which is fed with gas and freed of gas batchwise or interruptedly. 
     In the gas/gas heat exchanger  30 , the remaining fraction of the cooled and moist grinding circulation air  23 ′ is heated by the heat which, together with the combined exhaust gases  32  from the preheating stage  35 , escapes from the preheating stage  35  in the second open gas circuit  10 . In this case, the combined exhaust gases  32  are freed in a dust separator  33  of raw meal and of cement clinker particles from the right-hand plant part which have possibly passed into the dust separator  33 , and the combined exhaust gases  32  run in the second open gas circuit  10  through the gas/gas heat exchanger  30  where they discharge the heat transported by them to the cooled grinding circulation air  23 ′ into the first gas circuit  5 . 
     The combined exhaust gases  32  and the cooled moist grinding circulation air  23 ′ which flow through the gas/gas heat exchanger  30  differ greatly from one another in their composition, because the moist grinding circulation air  23 ′ largely has the composition of atmospheric air, with the exception of the moisture absorbed from the calcium carbonate-containing initial material. By contrast, the combined exhaust gases  32  have a very high CO2 fraction which comes, on the one hand, from the gas fraction of the deacidification gas CO2  32   a  for the deacidifying reaction of the limestone according to CaCO3⇄CaO+CO2 and, on the other hand, from the gas fraction of the combustion gas  32   b  which comes from the combustion of carbon-containing fuel according to C+O2⇄CO2 in the burner  56  of the sintering stage, here a cylindrical rotary kiln  40 , and finally from the gas fraction of the combustion gases  32   c  from the combustion of carbon-containing fuel according to the above equation in the burner  60  of the calciner  55 . 
     After the reheated moist grinding circulation air  23 ″ has left the gas/gas heat exchanger  30 , it flows to the point  41  where it is combined with the fresh dry cooler exhaust air  23 , of virtually the same temperature, which flows in from the right out of the second stage  45   b  of the two-stage cooler  45 , after the dry cooler exhaust air  23  has been freed by the dust separator  46  of cement clinker dust from the two-stage cooler  45 , since the cement clinker dust coming from the two-stage cooler  45  is highly abrasive and would prematurely wear the grinding stage  15  by abrasion. The heated moist grinding circulation air  23 ″ and the fresh cooler exhaust air  23  are then compressed by a compressor  47 , and the gas circuit  5  of the dry cooler exhaust air  23 , of the moist grinding circulation air  23 ′ and of the grinding circulation air  23 ″ having virtually the same composition as atmospheric air is closed at this point. 
     The above-described calcium carbonate-containing raw meal which has been separated by the dust separator  26  from the grinding circulation air  23 ′ used as drying and lifting gas is fed by a suitable transport device, not shown here, to the preheating stage  35 , the calcium carbonate-containing raw meal running through the preheating stage  35  from the top downward in countercurrent, at the same time running through the cyclone stages  48 ,  49  and  50  and at the same time being heated to near the temperature of the combined exhaust gases  32  which the combined exhaust gases  32  have in the second lowest cyclone stage  50  of the preheating stage  35 . The heated calcium carbonate-containing raw meal falls from the second lowest cyclone stage  50  into the lower part of the calciner  55  and is lifted by the exhaust gases from the cylindrical rotary kiln  40 , since in the cylindrical rotary kiln  40 , a burner  56  heats the cylindrical rotary kiln  40  by combusting a mixture  57   a  of primary fuel with primary air, the primary air ideally being oxygen-enriched and correspondingly nitrogen-depleted air. In addition to the exhaust gases from the combustion of the mixture  57   a , secondary air  58  from the first stage  45   a  of the two-stage cooler  45  is forced into the cylindrical rotary kiln  40  and leaves the cylindrical rotary kiln  40  via the calciner  55  together with the exhaust gases  32   b  from combustion. 
     In addition to the exhaust gases  32   b  and the secondary air  58  from the cylindrical rotary kiln  40 , the tertiary air  59  which likewise comes from the first stage  45   a  of the two-stage cooler  45 , also lifts the heated calcium carbonate-containing raw meal out of the second lowest cyclone stage  50  in the calciner  55 . There, the calcium carbonate-containing raw meal is deacidified in an endothermic reaction in the additional heat from the burner  60  which burns a mixture  61   a  of secondary fuel and of an oxygen-enriched and correspondingly nitrogen-depleted air, gaseous CO2 being released and CaO remaining as a solid suspended in the combined exhaust gases  32 . The combined exhaust gases  32  are therefore composed of the exhaust gases  32   b  and of the secondary air  58  from the cylindrical rotary kiln  40 , of the tertiary air  59 , of exhaust gases  32   c  from the combustion of the mixture  61   a  and of released deacidification exhaust gas CO2  32   a  from the deacidifying reaction. For the complete burnout of the mixture  61   a , which ideally oxidizes flamelessly in the calciner  55 , the suspension composed of the combined exhaust gases  32  and of the deacidified raw meal is intimately mixed in a swirl chamber  62  before it is conducted into the lowest cyclone stage  63 . In this lowest cyclone stage  63 , the combined exhaust gases  32  are separated from the largely deacidified raw meal from the calciner  55 . 
     The largely deacidified raw meal subsequently leaves the lowest cyclone stage  63  and falls from there into the cylindrical rotary kiln entry chamber  65  where it passes, protected from the rising exhaust gases of the cylindrical rotary kiln  40 , into the cylindrical rotary kiln  40 , is sintered there into cement clinker and then leaves the cylindrical rotary kiln  40  and falls into the first stage  45   a  of the two-stage cooler  45 . In the first stage  45   a  of the two-stage cooler  45 , the coarse-grained sintered cement clinker is cooled by the combined exhaust gases  32  recirculated in the gas circuit  10  and cooled in the heat exchanger  30 , the combined exhaust gases  32  heating up sharply and passing, on the one hand, as secondary air  58  into the cylindrical rotary kiln  40  and, on the other hand, as tertiary air  59  into the calciner  55  and thus leaving the first stage  45   a  of the two-stage cooler  45  again. In this case, the two-stage cooler  45  separates the gases located in the first stage  45   a  from the gases in the second stage  45   b  of the two-stage cooler  45 . Such separation is possible, for example, by means of what is known as a middle crusher, as a gas separation stage, in which the still coarse-grained clinker has to pass through a clinker crusher  45   c , the open gas circuits  5  and  10  being largely separated by a partition. A minimal gas slip, which occurs due to gas entrained by the coarse cement clinker to be crushed, has in this case to be taken into account. 
     The combined exhaust gases  32  which are separated from the largely deacidified raw meal in the lowest cyclone stage  63  run subsequently through the cyclone stage  50 , thereafter the cyclone stage  49  and finally the cyclone stage  48 . After the cyclone stages  50 ,  49  and  48 , the combined exhaust gases run through the dust separator  33 , and from there from the gas/gas heat exchanger  30  which, as described above, transfers the heat from the combined exhaust gases  32  to the moist and cooled grinding circulation air  23 ′, and the combined exhaust gases  32  are compressed in a compressor  70  to compensate the pressure loss hitherto experienced and from their pass via a part gas outlet  75  back into the first stage  45   a  of the two-stage cooler  45  where the gas circuit  10  is closed. 
     The highly CO2-enriched gas located in the gas circuit  10  leaves the plant  1  at the point  57   b / 61   b  through the part gas outlet  75 , this gas being delivered constantly by the exhaust gases  32 ,  32   a ,  32   b ,  32   c  from the combustion of the mixtures  57   a  and  61   a  in the burners  56  and  60  and by the deacidifying reaction of the carbonate-containing raw meal. 
     Only as much highly CO2-enriched combined exhaust gases  32  is taken off from the part gas outlet  75  as is introduced into the open gas circuit  10  as a result of the introduction of combustion and deacidification gases, in order to keep the gas quantity in the gas circuit  10  constant. In this case, in the context of this disclosure, as regards the gas circuit  10  too, an “open gas circuit” is understood to mean a gas circuit which is continuously fed with gas and freed of gas, and also a gas circuit which is fed with gas and freed of gas batchwise or interruptedly. The gases taken off in the part gas outlet  75  are then discarded by storage, instead of being released into the atmosphere. 
     A particular feature of the plant described here and of the corresponding method is that, instead of the exhaust gases from the preheater being used to dry the initial material in a preceding grinding stage, exhaust air from a clinker cooler is used for the almost ready cement clinker, the heat from the preheater being discharged to this cooler exhaust air not laden with harmful exhaust gases. The exhaust gases coming from the preheater are routed in the circuit of the plant, with the result that the degree of separation of the overall CO2 occurring in the process is greatly increased, as compared with known plants for producing cement clinker with separation of the CO2 occurring. 
     As is apparent from the foregoing specification, the invention is susceptible of being embodied with various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. It should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art. 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 LIST OF REFERENCE SYMBOLS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                  1 
                 Plant 
               
               
                   
                  5 
                 Open gas circuit 
               
               
                   
                 10 
                 Open gas circuit 
               
               
                   
                 15 
                 Grinding stage 
               
               
                   
                 20a 
                 Feed point 
               
               
                   
                 22 
                 Point, incoming cooler exhaust 
               
               
                   
                   
                 air 
               
               
                   
                 23 
                 Cooler exhaust air, dry 
               
               
                   
                 23′ 
                 Grinding circulation air, moist 
               
               
                   
                 23″ 
                 Grinding circulation air, moist, 
               
               
                   
                   
                 heated 
               
               
                   
                 25 
                 Point, outgoing raw meal 
               
               
                   
                   
                 Cascade, dust separator 
               
               
                   
                 26 
                 Compressor 
               
               
                   
                   
                 Part gas outlet 
               
               
                   
                 27 
                 Cooler air supply 
               
               
                   
                 28 
                 Point, outgoing cooler exhaust 
               
               
                   
                   
                 air 
               
               
                   
                 28a 
                 Gas/gas heat exchanger 
               
               
                   
                 28b 
                 Combined exhaust gases 
               
               
                   
                 30 
                 Deacidification gas CO 2   
               
               
                   
                 32 
                 Combustion exhaust gas 
               
               
                   
                 32a 
                 Combustion exhaust gas 
               
               
                   
                 32b 
                 Dust separator 
               
               
                   
                 32c 
                 Preheating stage 
               
               
                   
                 33 
                 Cylindrical rotary kiln 
               
               
                   
                 41 
                 Point, combination of cooler 
               
               
                   
                   
                 exhaust gases 23, 23′ 
               
               
                   
                   
                 Two-stage cooler 
               
               
                   
                 45 
                 First stage 
               
               
                   
                 45a 
                 Second stage 
               
               
                   
                 45b 
                 Clinker crusher, gas 
               
               
                   
                 45c 
                 separation stage 
               
               
                   
                   
                 Dust separator 
               
               
                   
                 46 
                 Compressor 
               
               
                   
                 47 
                 Cyclone stage 
               
               
                   
                 48 
                 Cyclone stage 
               
               
                   
                 49 
                 Cyclone state 
               
               
                   
                 50 
                 Calcinor 
               
               
                   
                 55 
                 Burner 
               
               
                   
                 56 
                 Mixture, fuel 
               
               
                   
                 57 
                 Point, outgoing gas 
               
               
                   
                 57b 
                 Secondary air 
               
               
                   
                 58 
                 Burner 
               
               
                   
                 60 
                 Mixture, fuel 
               
               
                   
                 61 
                 Point, outgoing gas 
               
               
                   
                 61b 
                 Swirl chamber 
               
               
                   
                 62 
                 Cyclone stage 
               
               
                   
                 63 
                 Cylindrical rotary kiln entry 
               
               
                   
                 65 
                 chamber 
               
               
                   
                 70 
                 Compressor 
               
               
                   
                   
                 Part gas outlet