[0001] The invention relates to a method for producing carbon briquettes from organic matter by a thermal treatment thereof, in which method matter to be processed is brought by a feed arrangement to a conveyor arrangement connected to a process space that is substantially of a Thompson Converter type. The matter to be processed is made to move in the process space in a longitudinal direction thereof by means of a conveyor arrangement closed in relation to the space. Pyrolysis gas formed by heat transfer from the process space into the matter to be processed contained in the conveyor system is conveyed into a combustion space provided in the process space for combustion of the gas, flue gas thereby formed being discharged from the process space by means of a discharge arrangement, and thermally treated matter is discharged from the conveyor arrangement for further processing.

[0002] The use of a conventional Thompson Converter type apparatus for the above purpose is based on the feeding of the matter to be processed to one or more screw conveyors provided in the process space of the apparatus, by which conveyor/s the matter to be processed is transferred in the longitudinal direction of the process space while being heated indirectly at the same time. The matter carbonized inside the screw conveyors by heat transferred from the conveyors to the matter to be processed is discharged from one end of the conveyors to a collecting conveyor that transfers the carbonized matter out of the process space. In a solution such as this the pyrolysis gas created inside the screw conveyors is conventionally carried within the matter to be processed in the travel direction thereof from the discharge end of the screw conveyors to a collection chamber and further on a connecting conduit to a combustion furnace below the screw conveyor space, where it is burned. Fuel gas leaves the combustion furnace to enter a screw conveyor space, where the heat contained in the fuel gas is transferred by convective heat transfer into the screw conveyors before being discharged from the process space through a discharge assembly.

[0003] The activation of this type of apparatus requires the combustion furnace to be heated throughout to a sufficiently high temperature e.g. by means of solid fuel burned therein before the actual carbonization process is started to allow the pyrolysis gas to be burned and to make the system then work in what is known as a self-sustained manner. For this reason the solution in question is laborious and slow particularly as regards initial start-up.

[0004] There are also current solutions of the above type in which the combustion furnace is provided with a kerosene burner to maintain an aux- iliary flame, thus providing a further implementation in which pyrolysis gas conveyed to a direction opposite to the transfer direction of the screw conveyor arrangement is carried to the combustion furnace for combustion in the burner flame.

[0005] The use of an apparatus such as the one above particularly for producing carbon for the purpose of making carbon briquettes is in practice not economical, because the calorific value of manufactured carbon for use as carbon briquettes in particular is significantly lower than the corresponding calorific value of mineral coal, for example. The reason for this is that in carbonization carried out by conventional technology the gases released from it in connection with pyrolysis contain matter of a valuable calorific value which cannot be made use of in the carbonized matter but only in the combustion of pyrolysis gas. On the other hand, an essential disadvantage is that the preheating of the furnace space requires using either solid fuel for a relatively long period of time or continuous use of an auxiliary flame produced by separate fuel to allow pyrolysis gas to be burned. Hence current technology does not enable a carbon separation process of reasonable investment and operating costs particularly for producing carbon briquettes to be implemented.

[0006] An object of the invention is to provide a decisive improvement to the above problems and thereby significantly raise the level of the art prevailing in the field. For this purpose the method of the invention is primarily characterized in that for separating tar contained in the pyrolysis gas formed in the process space, the gas is processed by a separation arrangement before it is burned in the combustion space so as to produce carbon briquettes from the thermally treated matter by grinding it and mixing therein tar separated from the pyrolysis gas and by compressing these ingredients into briquettes.

[0007] Among the most important advantages of the method of the invention to be mentioned are the simplicity and efficacy of its operating principle, of the equipment suitable thereto and the use thereof. The method of the invention enables producing carbon briquettes of a calorific value comparable to that of mineral carbon by processing organic matter in a technically extremely simple and efficient manner by applying as a preferred embodiment a continuous conveyor arrangement provided with a feed and discharge member that is substantially gas tight in relation to the environment. This allows to prevent oxygen supply to the pyrolysis gas within the conveyor arrangement, whereby the gas travelling towards the feed end of the conveyor arrangement according to the principle of countercurrent flow is efficiently cooled as the heat contained therein is transferred into matter to be processed travelling to the opposite direction, thus allowing the pyrolysis gas to be conveyed at an ideal temperature to a heat exchanger and/or small separation arrangement. The volume efficiency of the apparatus implemented according to the invention is optimal when heat transfer to the conveyor arrangement takes place in the process space by direct radiation heat from the flame of the gas burner/burners (the radiation heat transfer being proportional to the fourth order of the temperature), thus speeding up the initiation of the carbon separation process because direct radiation from the gas flame increases the surface temperatures of the conveyor system significantly more rapidly than convective heat transfer. The method of the invention thus enables producing carbon briquettes of a calorific value substantially corresponding to that of mineral carbon by an apparatus which is compact and significantly smaller than corresponding, currently available apparatuses and naturally also significantly more affordable in terms of investment, service and maintenance costs than prior art solutions.

[0008] Other preferred embodiments of the method of the invention are disclosed in the dependent claims drawn to the method.

[0009] In the following, the invention will be illustrated in detail with reference to the accompanying drawings, in which

Figure 1 shows, by way of an example, a perspective view of an apparatus whose operation is based on the method of the invention;

Figure 2 shows a longitudinal section illustrating the operating principle of a similar apparatus; and

Figure 3 shows a preferred Pl diagram of an apparatus in which the method of the invention is applied.

[0010] The invention relates to a method for making carbon briquettes from organic matter by thermal treatment thereof, in which method matter to be processed x is brought by a feed arrangement 1 to a conveyor arrangement 3 connected to a process space 2 that is substantially of a Thompson Converter type. The matter to be processed x is made to move in the process space 2 in a longitudinal direction s thereof by means of a conveyor arrangement 3 closed in relation to the space, whereby pyrolysis gas y formed by heat transfer from the process space into the matter to be processed x contained in the conveyor system is conveyed into a combustion space 4 provided in the process space for combustion of the gas, flue gas y' thereby formed being discharged from the process space by means of a discharge arrangement 5 and thermally treated carbonized matter x' is discharged from the conveyor arrangement for further processing. To separate the tar contained in the pyrolysis gas y formed in the process space, the gas is processed before combustion in the combustion space 4 by a separation process 6 to produce carbon briquettes from the thermally treated matter x' by grinding it and mixing therein tar p separated from the pyrolysis gas y and by compressing these ingredients into briquettes.

[0011] As a preferred embodiment of the method of the invention, pyrolysis gas y is conveyed according to the principle illustrated in Figure 2 within the conveyor arrangement 3 by countercurrent towards a feed end I of the conveyor arrangement for transferring the heat contained in the pyrolysis gas to matter to be processed x that is moving to the opposite direction s and for feeding cooled pyrolysis gas y to a small separation arrangement 6.

[0012] As a further preferred embodiment, the pyrolysis gas (y) is cooled by a heat exchanger arrangement (7) before being fed to the small separation arrangement (6).

[0013] As a further preferred embodiment of the method of the invention, the matter to be processed x is handled in connection with the process space 2 by a continuous conveyor arrangement 3 provided with feed and discharge members 1 a, 1 b that are substantially gas tight in relation to the environment, the arrangement being implemented by means of one or more screw conveyors 3a or the like that are driven by an electric motor o and steplessly regulated by means of a frequency converter, for example.

[0014] The matter to be processed may be fed to the conveyor system 3 by using the method and feed arrangement of Finnish Patent 119125, for example, particularly for implementing overfeed of the matter to be processed, firstly, in a continuous manner and, secondly, according to the principle of the Pl diagram of Figure 3, for example, in such a way that process gases are prevented from escaping from the conveyor arrangement or the process space into the environment in an uncontrolled manner. [0015] With a particular reference to the Pl diagram of Figure 3 provided as an example, the tar p contained in the pyrolysis gas y is separated according to a preferred embodiment by an electrostatic precipitator (ESP).

[0016] With a further reference to the preferred implementation of Figure 3, the thermally treated carbonized matter x' is removed from the process space 2 and then ground in step A, tar p obtained from the small separation arrangement 6 being mixed therein at the same time. As a further preferred embodiment, the ground, carbonized matter x' and the tar p mixed together are compressed into briquettes in step B by one or more briquette presses.

[0017] As a yet further preferred embodiment, the pyrolysis gas y is cooled to about 30 ⁰ C before being fed to the small separation arrangement 6. Correspondingly, thermally treated carbonized matter x' is removed from the process space 2 preferably at a temperature of 450°.

[0018] The density of the carbon briquettes to be produced is preferably 700 to 800 kg/m ³ and their calorific value is at least 31 Mj/kg.

[0019] As a yet further preferred embodiment and with a particular reference to the principle disclosed in Figure 2, the transfer power of the conveyor arrangement 3, such as one or more screw conveyors 3a, is changed in the longitudinal direction s of the processing space so as to particularly reduce the layer thickness of the matter to be processed x from the feed end I of the conveyor arrangement 3 towards its discharge end II. In that case the conveyor arrangement 3 is preferably implemented by a screw conveyor 3a provided with one or more lower pitches at the front end thereof and one or more higher pitches at the rear end thereof.

[0020] With a further reference to the implementation of Figure 2, air supply to the gas burner arrangement 7, such as one or more parallel gas burners 7a, is implemented by a separate combustion air blower 9. On the other hand, an ejector blower 10 is applied, also in a preferred manner, in con- nection with one or more gas burners 7 belonging to the gas burner arrangement 3 for sucking pyrolysis gas y through an ejector nozzle 11 into the gas burner.

[0021] Further, as shown in the accompanying drawings, the method of the invention allows also mutually different types of matter x, w to be processed simultaneously by introducing them into the conveyor system by two longitudinally successive feeders 1 ; 1a, as shown in the accompanying drawings, the matter transferred from the feeders becoming then mixed as the screw conveyor 3a pushes them towards the process space. In this connection it is naturally also possible to use e.g. a solution of the Pl diagram shown in Figure 3, the different materials being mixed in a separate mixing space and conveyed by one conveyor to the conveyor arrangement 3.

[0022] It is obvious that the invention is not restricted to the embodiments presented or explained above, but may be modified within the basic inventive idea according to each purpose of use and application. Hence it is evident, firstly, that in the method of the invention conventional control technol- ogy and automation known per se, such as oxygen analyzers and temperature sensors needed in the combustion of pyrolysis gas and/or a preheating burner as in the exemplary Pl diagram of Figure 3, for example, may be utilized in the combustion process. Similarly, a screw conveyor arrangement provided with necessary control arrangements for enabling optimal carbonization and final temperature by stepless regulation of the operation of the screw conveyor arrangement, for example, may be used in the processing of the matter to be processed. It is naturally preferred to provide an apparatus applying the method of the invention with optical flame monitoring analyzers, for example, and with a "torch tube" 12 connected to the conveyor arrangement, as in the drawings, to allow pyrolysis gas to be released, when necessary, by combustion in a separate burner, as shown in the Pl diagram of Figure 3, the torch tube thus serving as a relief valve enabling rapid emergency switch-off of the apparatus.