Abstract:
A method and installation for the cremation of bodies in coffins. The coffin is placed in a crematorium furnace in the wall of which at least one burner is disposed. Conbustion occurs in a chamber of the crematorium furnace without naturally-occurring air and with the burning of the coffin supplying energy along with part of the recirculated flue gas in which oxygen has been added. The flue gas fed back to the crematorium furnace is recirculated uncooled. The temperature at the crematorium furnace is maintained by the burning coffins and the oxygen-enriched recirculated flue gas.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method for the cremation of bodies in coffins m a crematorium furnace, in whose walls at least one burner is arranged, which is supplied with fuel, and wherein the removal of the flue gas being generated during the cremation takes place via a conduit, and an installation for the cremation of bodies in coffins. 
     BACKGROUND OF THE INVENTION 
     Today, such methods for cremation are subject to increased requirements for protecting the environment (i.e., 17th Federal Emission Protection Ordinance). This means that there are maximum values for the noxious material burden, which may not be exceeded. In accordance with the prior art, there is only the possibility of subjecting the flue gas released into the chimney to flue gas scrubbing. However, this is expensive. Often, it is not possible because of space considerations in the existing installations which are to be retrofitted. 
     Moreover, at the start of the combustion process, large amounts of carbon monoxide are generated by the burning of the coffin, which is made of wood, since because of the available portion of oxygen in the air used for the combustion, the amount of oxygen which would be required for the complete combustion of the carbon being generated in is phase of the cremation process is not available, even though at present operations are performed with air numbers of up to 3.5. Thus, at the start of burning, large loads of non-consumed CO are released. This is particularly unfortunate because CO leads to the formation of cancer-causing dibenzofuranes and dibenzodioxins. 
     Typically, the thermal output of such crematorium furnaces is approximately 550 to 600 KW, which corresponds to a net output of 60 standard cubic meters (Nm 3 ) of natural gas per hour. This means that at an air number of 3.5 approximately 2200 Nm 3  of flue gas per hour are being produced. The downstream-connected flue gas scrubbing components must be dimension correspondingly large. 
     The retrofitting of exiting installations which is demanded today is also problematic, because the existing crematoria are classified as historical monuments, so that structural changes are very difficult or even impossible to undertake. 
     The considerable amount of flue gas heat being created causes a further problem. While in some countries the waste heat is commercially used, this is not the case, for example in Germany, for reasons of piety. 
     A further problem of the flue gas in general lies in that nitrous oxides (NOx) are generated in the course of combustion with the use of natural air because of the heavy nitrogen content of the air (approximately 75%), and this at high air numbers in particular. This also makes the later cleaning of the waste gas necessary. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to further develop a method of the type mentioned at the outset in such a way that the noxious waste gases are reduced and the energy used increased. In the case of a retrofit, this should be achievable by possibly also increasing the efficiency of existing cremation installations. 
     This object is attained in accordance with the present invention in that cremation takes place in a crematorium furnace without a supply of natural air, in that at least half the flue gas leaving the crematorium furnace is conducted without being cooled to the crematorium chamber for creating a flue gas cycle, and in that oxygen is admixed with the flue gas in the flue gas cycle. The present invention fiber relates to several advantageous further developments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Exemplary embodiments in their advantageous further development will be described in greater detail in what follows, making reference to the drawings. Represented are in: 
     FIG. 1 is a first exemplary embodiment of a crematorium furnace for practicing the method, 
     FIG. 2 is a second exemplary embodiment of a crematorium furnace for practicing the method, and 
     FIG. 3 is a flexible lock, which can be used with the two exemplary embodiments in FIGS.  1  and  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a crematorium furnace  1 . It is designed as a so-called “double-deck” furnace. A coffin  2  with a body therein has been placed into it. The coffin has been put on supports  3 . The coffin  2  is introduced through a flexible lock  50  (see FIG. 3 for details of this). Two burners  5  and  6  terminate in the walls of the furnace, which are supplied with support energy (for example natural gas) through a conduit  7 , and with a mixture of oxygen and recirculated flue gas through a conduit  8 . The mixer is prepared in a mixer  9 . The mixer  9  is supplied with pure oxygen from an oxygen source, for example a reservoir  11 , via a conduit  10 , and with recirculated flue gas via a line  12  and a control flap  13 . A conduit  25 , from which the conduit  12  branches off, is the flue gas exhaust conduit of the crematorium furnace  1 . 
     The installation furthermore contains another mixer  14 . Recirculated file gas is also supplied to it via a conduit  15 . It receives oxygen via a conduit  16 . The conduit  15  is also connected with the conduit  25 , which conducts the flue gas removed from the crematorium furnace  1 , and with the oxygen source  11  via the conduit  16 . The position of a control flap  17  provided downstream of the branch of the conduit  15  determines the proportion of recirculated flue gas. The amount of recirculated flue gas can be set such that it is approximately 75%. This corresponds approximately to the proportion of nitrogen in natural air. Thus, a mixture of artificial air, so to speak, is created. An amount of flue gas, preponderantly consisting of CO 2 , which is determined by the amount of flue gas generated during combustion, is removed through conduits  26 ,  27 ,  28 . Because no natural air, and therefore no nitrogen from the air, is a part of the combustion process anymore, only nitrogen, which might possibly be present in the fuel, can add to the formation of nitrous oxides. In this way, the amount of nitrous oxides being generated is considerably reduced in this way. 
     The amount of flue gas which is forced to escape out of the combustion cycle, is first conducted through the conduit  26  to a heat exchanger  18 , and from there reaches a so-called “flow stream” reactor  19 , which is supplied with an active scrubbing agent (for example “SORBALIT”) (a mixture of calcium hydride and pulverized open hearth coke) via nozzles  20  through a conduit  21 . Inter alia, the heat exchanger  18  is used for cooling the flue gas sufficiently, so that the highest permissible operating temperature of the reactor  19  is not exceeded. The pulverulent absorption agent supplied via the nozzles  20  is then cleaned again in a textile or “baghouse” filter  22  before the scrubbed flue gas escapes through a chimney  23 . 
     As can already be seen from this description, a portion of the flue gas being generated during combustion in the crematorium furnace  1  and which can be adjusted by means of the position of the control flaps  13  and  17 , is returned to the crematorium furnace, namely first via the conduit  25 , the control flap  13 , the conduit  12 , the mixer  9 , the conduit  8  and the burners  5 , or respectively  6 , and then via the conduit  25 , the conduit  15 , the mixer  14  and the conduit  24 . 
     Differently from known combustion installations, the amount of oxygen required for burning the support energy (for example natural gas) is made available at the burners  5 , or respectively  6 , by the supply of artificially generated oxygen of a purity of at least 90% from an oxygen source  11 , for example a reservoir, via the conduit  10  and the mixer  9 . 
     The availability of “artificial” or “synthetic” air (i.e. the described mixture of recirculated flue gas and admixed oxygen) is moreover provided in a mixer  14 , from which it reaches the crematorium furnace  1  directly—ie. without combustion in a burner—. This supply is used to satisfy the considerable need for oxygen, which cannot be satisfied by burning the wood of a coffin  2 , in particular in the starting phase of the cremation process, and which normally, ie. when combustion takes place by the supply of air, cannot be satisfied by the limited proportion of oxygen in the air. As mentioned, with conventional crematorium furnaces in the starting phase this leads to a very high proportion of CO (carbon monoxide), since with natural air the amount of available oxygen is limited by the O 2  portion of the air of 21%. By making the oxygen available in an adjustable manner directly at the location where the wood of the coffin  2  is burned, the proportion of CO being generated is considerably lowered. The required energy for combustion is moreover supplied with the carbon portion of the wooden coffin, so that therefore at these locations and in this phase of the process no outside energy supply by means of a burner is required. On the one hand, this reduces the provision (amount) of supplied support energy (natural gas) by means of the burners and, on the other hand, lowers the proportion of carbon monoxide in the flue gas, or respectively reduces it to zero. 
     The reason why during this entire process not only pure oxygen is made available, but is admixed with recirculated flue gas, lies in that otherwise the temperature in the furnace chamber would become too high. The recirculated flue gas, predominantly composed of CO 2 , assumes the cooling function as well as the heat transport function of the substituted nitrogen. 
     The flue gas return takes place without cooling. The result of this is that the additionally required heating of the furnace chamber by means of supplying support energy to the burners  5  and  6  can accordingly be set by means of correspondingly larger switch-on cycles. It is therefore possible to even turn off the burners partially, namely at the time when—at the start of the combustion process—the coffin  2  itself begins to burn. Thus, the maintenance of a high temperature by recirculation of the uncooled flue gas, as well as the simultaneous provision of oxygen, allow the temporary maintenance of the combustion process without activating the burners, i.e. without support energy. By means of this it is possible to save considerably more energy, both in connection with the support energy as well as in connection with the oxygen. Because of this a simultaneous reduction of the carbon dioxide being generated takes place, the latter being problematical in view of the environment because of the so-called greenhouse effect. 
     This increased utilization of the heat by means of a large return of heat in the cycle also compensates for the fact that, for reasons of piety, no utilization of the heat by heating other installations or by operating a cooling machine takes place with cremation installations of this type, even though appropriate additional installations represent advantageous fiber developments of the present invention. However, utilization of the waste heat during non-heating periods is problematical in any case. 
     The totality of the processes requires regulation as a function of the course of the combustion process. The latter takes place in a very fluctuating manner since, as mentioned, burning of the coffin takes place first. Then the cremation of the body starts. But this process to a large extent is an evaporation process, not a combustion process, since the human body consists to a large extent of water. It is therefore necessary in the starting phase to make much more oxygen available—as mentioned—than in the later phase of the combustion process, while at the same time considerable energy is made available in the first phase by burning the coffin  2 , so that no additional supply of support energy is required. A control unit  30  is provided for regulating these processes, which is connected with one or several temperature sensors  31  and the CO sensor  37  and therefore detects at least the temperature in the crematorium furnace  1 . The output of the burners  5  and  6  is regulated as a function of this via the control lines  32 ,  33 , and the amount of recirculated flue gas by setting the control flaps  13 ,  17  via control lines  34 ,  35 . If required, it is possibly provided to set the amount of oxygen released from the oxygen source  11  to the conduits  10 , or respectively  16 , separately and independently via the control unit. In the process, the CO in the flue gas is continuously measured by a CO sensor  37 . The regulating variable affects the oxygen supply, or respectively concentration, in the furnace chamber. 
     A further advantage of the way to proceed proposed here results from dimensioning. While with conventional cremation the flue gas flow is approximately 2200 to 2500 NmrAh of flue gas, with the described cycle conditions it can be reduced by approximately one fourth, i.e. to 400 to 600 Nm 3 /h of flue gas. This allows a considerable reduction in new installations with a simultaneous increase in output. Moreover, retrofitting of existing installations in made considerably easier. The length of combustion is considerably reduced by the method in accordance with the present invention. While with conventional cremation the combustion in the starting phase is more a swelling process (CO formation), with the present invention the combustion process is considerably accelerated by the concentrated supply of oxygen. This is of great importance in view the increasing number of cremations. 
     In the normal case, the provision of artificially produced oxygen in reservoirs takes place in liquid form with an evaporation unit. However, it is also possible to provide an on-site installation for oxygen generation in accordance with the pressure change absorption, or respectively, diaphragm principles. 
     A further advantage of the represented way to proceed rests in a reduced amount of required operating means. The usually required catalytic nitrous oxide removal, for example by adding activated charcoal, “SORBALIT”, etc. can be considerably reduced. Since combustion takes place without air, and therefore the generation of nitrous oxides approaches zero, scrubbing of the waste gas in the reactor  19  is essentially only used for removing the dibenzodioxin and dibenzofurane created in the cremation of the coffin and the body, as well as the poisonous materials created in the combustion of heavy metal, for example mercury (part of amalgam fillings), etc. 
     FIG. 2 shows a further exemplary embodiment, which differs from the exemplary embodiment represented in FIG. 1 to the extent that the recirculation of flue gas takes place via the flap  13  and the mixer  9  to the burner  5 , or respectively  6 , only at a point downstream of the heat exchanger  18 . This allows the employment of conventional burners, since cooled flue gas enters these. It is therefore not required to design the burners  5  and  6  for higher temperatures as in FIG.  1 . Otherwise the flue gag circulation continue to take place via the conduit  15 , the mixer  14  and the conduit  24 . 
     FIG. 3 shows the flexible lock  50 . Its purpose ensues from the following method requirements when a coffin  2  has been burned, after approximately 60 to 90 minutes, the door  40  of the crematorium furnace  1  is opened (for example, lifted or pushed laterally by means of a motor). A further coffin  2  is introduced into the crematorium furnace  1  via a conveying device. If this is done without special precautions, natural air enters the crematorium chamber  1  in the process and can lead to the formation of nitrous oxides during the subsequent cremation. If preparations are made to prevent the entry of air into the crematorium chamber I during the charging process, the recirculation of the flue gas without the addition of O 2  and without operating the burners  5 ,  6  can be permitted to continue also during this changing process, i.e. the temperature in the crematorium chamber  1  can be kept at a high level (650 to 1000 degrees C) without negative consequences resulting therefrom, while at the same time a further energy saving effect is achieved by avoiding a reheating phase. Moreover, time is saved by this. 
     In the exemplary embodiment of FIG. 3 the flexible lock  50  is constituted in that—as already known per se—the coffin  2  rests on a slab  51 . This slab can be displaced back and forth in the direction toward the door  40  (see the arrow  52 ), as well as up and down (see the arrow  54 ) by a lifting device  53 . With the door  40  open, the coffin  2  is introduced into the crematorium chamber  1  by an appropriate movement of the slab  51  and placed on supports  3 . The present invention now provides that a flexible bellows  56  is provided between the slab support  55  and the crematorium furnace in the area of the door  40 , so that a closed space  60  is created around the coffin  2  during the charging process. Loading of the slab  51  with the coffin  2  is performed after a closure  57 , which is only schematically indicated, is released. The space  60  inside the bellows  56  is connected via an air conduit  61  with an exhaust pump  62 . in this way it can be provided that, in comparison to atmospheric pressure, a defined underpressure prevails in the space  60 , which assures that no air from the space  60  is transferred into the crematorium furnace  1  when the door  40  is open.