METHOD AND APPARATUS FOR THE PRODUCTION OF UNBURNED BIOCHAR WITH THERMAL TREATMENT

Abstract

The invention relates to a method and apparatus for producing, with thermal treatment, biochar not intended to produce energy by combustion, as a heat sink, using a conveyor system (3) housed essentially in a Thompson Converter type process space (2).The raw material to be processed (x) is transported to the process space (2) by the conveyor system (3), located in a close position, in the longitudinal direction (s) of the process space, where the pyrolysis gas (y), generated from the raw material to be processed (x) present in the conveyor apparatus (3) as a result of the heat transferred from the process space, is directed to the combustion chamber (4) present in the process space to burn the gas, where the generated exhaust gas (y') is extracted from the process space by means of a discharge system (5) and the resulting unburned biochar (x') is extracted from the conveyor system for further processing.The amount of PAH compounds contained in the unburned biochar to be produced (x') is reduced / eliminated by steam (z') by supplying water (z) into the inside of the conveyor system (3); subsequently, the water (z) is conveyed into the inside of the conveyor system (3) from its discharge end (II) to transport the steam flow (z') together with the pyrolysis gas (y) in a counterflow with respect to the longitudinal direction (s) of the process space towards the supply end (I) of the conveyor system.

Description

METHOD AND APPARATUS FOR THE PRODUCTION OF UNBURNED BIOCHARCOAL WITH THERMAL TREATMENT The invention relates to a method and apparatus, as set forth in the preambles of the separate applications filed, for the manufacture, with heat treatment, of biochar not intended to produce energy by combustion, i.e., it is functional as a carbon sink. The use of a traditional Thompson converter involves supplying the raw material to be processed to one or more screw conveyors located within a processing chamber. The raw material is conveyed longitudinally by these conveyors while being indirectly heated. The carbonized raw material, heated by the heat transfer from the conveyors, is discharged from one end of the conveyors onto a collection conveyor that directs the carbonized raw material out of the processing chamber.In this solution, the pyrolysis gas generated within the screw conveyors traditionally migrates in the same direction as the raw material being processed, from one end of the screw conveyor discharge to a collection chamber. From there, it continues through a connecting duct to a combustion furnace located beneath the screw conveyor for combustion. The exhaust gas exits the combustion furnace into the screw conveyor space, where the heat contained in the exhaust gas is transferred to the screw conveyors by convection before being removed from the process space via a discharge unit. Activating the type of device mentioned requires that the combustion furnace be thoroughly heated, for example, with solid fuel, to a sufficiently high temperature before starting the actual carbonization process. This allows the pyrolytic gas to combust and the process to operate in a self-sufficient manner. Therefore, the solution described is laborious and time-consuming, especially with regard to initial startup. Solutions of the above type are also currently possible in those implementations where the combustion furnace is equipped, e.g., with a kerosene burner to maintain an auxiliary flame, a larger implementation that would cause that pyrolytic gas, transported in the opposite direction to the direction of movement of the screw conveyor, to be directed to a combustion furnace to be combusted with the flame of the aforementioned burner. The most notable drawback of the aforementioned type of equipment is its modest volumetric efficiency [W / m³], resulting from convective or indirect heat transfer applied to the screw conveyors. Firstly, this considerably lengthens the cold start period before the continuous carbonization process can begin. Secondly, a significant drawback is that preheating a furnace requires either the use of solid fuel for a considerable period or the continuous use of an auxiliary flame produced by a separate fuel to facilitate combustion of the pyrolysis gas. Therefore, current technology is not capable of providing a carbon separation process that can be implemented with reasonable investment and operating costs. For example, the application of the international patent WO Patent 2011 / 004073 discloses a method for separating coal by thermal treatment, where the material to be processed is conveyed by a feeding mechanism to a conveyor system connected to a process space that is essentially of the Thompson converter type. The material to be processed is designed to move longitudinally through the process space via a conveyor system close to the space, where the pyrolysis gas formed by heat transfer from the process space to the material to be processed contained in the conveyor system is transported within the conveyor system in the opposite direction to the transport direction and exits the conveyor system to combust in a combustion chamber available in the process space.The exhaust gas produced is discharged from the process space via a discharge mechanism, and the heat-treated material is discharged from the conveyor system via discharge elements for further processing. In this regard, the pyrolysis gas is first combusted by a continuous gas burner mechanism, and secondly, heat transfer from the conveyor system into the process space is primarily achieved through direct radiation from the gas burner flame and the walls of the combustion space. z / PZLn / Lznz / e / Yi / u However, even this solution does not allow the production of unburned biochar in such a way that the contained PAH compounds are at a sufficiently low level. The present method and apparatus, according to the invention, aim to offer a decisive improvement with respect to the aforementioned problems and, therefore, to considerably improve the prior art available. To achieve this objective, the method and apparatus of the invention are characterized essentially by what has been presented in the characterization clauses of the separate applications filed for this purpose. The most important benefits obtained through the method and apparatus of the invention should be considered, including the simplicity and effectiveness of its operating principle, and the availability of the apparatus suitable for its implementation and use. Thanks to the invention, it is possible to produce unburned biochar containing a very small amount of PAHs, ideally none at all. This can be achieved by heat-treating a raw material within a conveyor system using steam generated from water supplied to the system. The invention can be implemented in an extremely simple and technically efficient manner by employing, firstly, a continuously operating conveyor system equipped with a discharge and supply element that is substantially airtight.In this way, the supply of oxygen to the pyrolysis gas within the conveyor system can be avoided, where the aforementioned gas, as it moves towards the end of the conveyor system supply in a counterflow principle with respect to the raw material to be processed that is directed longitudinally along the same, is effectively cooled as the contained heat is transferred to the raw material to be processed by moving it in the opposite direction and allowing the pyrolysis gas to be conducted at an ideal temperature to the gas burner for combustion. The use of a sufficiently large combustion chamber in the process space allows, firstly, the combustion of exhaust gases with a residence time of two seconds at a temperature above 850 °C, as required by the EU waste incineration directive. Furthermore, the existing conditions in a rear section of the combustion chamber are favorable for a selective non-catalytic nitrogen reduction (SNCR) reaction, e.g., at a temperature of 800–1100 °C and in an oxidizing atmosphere. The apparatus constructed using a method of the invention has optimal volumetric efficiency, since heat transfer to a conveyor system occurs within the process space from the flame of one or more gas burners using direct radiation (radiative heat transfer being proportional to the fourth power of the temperature). This facilitates the start-up of an unburned biochar production process, as the surface temperatures of the conveyor system increase considerably faster with direct radiation from a gas flame than with convective heat transfer. Therefore, this invention allows for the assembly of an apparatus that is considerably smaller and more compact than current equivalent products, and whose service, investment, and maintenance costs are also, naturally, more affordable than those of traditional solutions. Other preferred representations for a method and apparatus of the invention are presented in the dependent applications filed thereon. zyczLn / Lznz / e / YiAi In the following description, the invention will be reviewed in detail with reference to the attached Figure 1, which illustrates a general operating principle for the apparatus that operates using a method of the invention. First, the invention relates to a method for the thermal treatment production of unburned biochar, with the same functionality as a heat sink; the aforementioned method includes introducing a raw material to be processed (x) with supply elements (la) inside a conveyor system (3), which is present in a Thompson Converter type process space (2) and in a close position, to move the raw material to be processed (x) through the process space (2) in a longitudinal direction (s) of the process space, where the pyrolysis gas (y), generated from the raw material to be processed (x) existing in the conveyor apparatus (3) as a result of the heat transferred from the process space, is conducted from the conveyor mechanism to be burned in the combustion chamber (4) of the process space.The resulting exhaust gas (y') is extracted from the process space by means of a discharge mechanism (5) and the unburned biochar produced (x') is extracted from the conveyor apparatus with discharge elements (Ib) for further processing. z / pzLn / Lznz / e / YiAi With particular reference to the attached example process flow diagram, the pyrolysis gas (y) is burned using a preferably continuously operating gas burner system (7), and heat transfer from the conveyor system (3) to the process space (2) is primarily conducted by direct radiation from a flame of the gas burner system (7) and from the combustion chamber walls (4). Furthermore, the pyrolysis gas (y) is conveyed by the conveyor system (3) in a counterflow with respect to the longitudinal direction (s) of the process space towards a supply end (I) of the conveyor system to transfer the heat present in the pyrolysis gas to the raw material to be processed (x), moving in the longitudinal direction (s) of the process space and supplying cooled pyrolysis gas (y) to the gas burner mechanism (7).The amount of PAH compounds contained in the unburned biochar to be produced (x') is reduced / eliminated by steam (z') by supplying water (z) into the inside of the conveyor system (3); subsequently, the water (z) is conveyed into the inside of the conveyor system (3) from its discharge end (II) to transport the steam flow (z') together with the pyrolysis gas (y) in a counterflow with respect to the longitudinal direction (s) of the z / pzLn / Lznz / e / YiAi process space towards the supply end (I) of the conveyor system. With reference to the attached process flow diagram, it is also particularly important that, when applying a method of the invention, the expulsion of the pyrolysis gas (y') takes place in the longitudinal direction (s) of the process space (2) before the supply (la) of the raw material to be processed (x). Conducting the aforementioned operations in the wrong order substantially impairs the usability of the process, where, for example, the pipes involved in the aforementioned operations could easily become clogged, and when the process is carried out at high capacity, the mass can rise to the gas pipe. Furthermore, it is especially important for the sound operation of a method of the invention that the surface level of the raw material to be processed within the conveyor system be carefully controlled, which is absolutely necessary, especially with regard to managing pressure and tar buildup.Another crucial aspect is the management of the pyrolysis gas, including its temperature and humidity. Without a water supply, the gas lines will quickly become clogged because the raw material will be dry. Humidifying the raw material is a challenging operation that could lead to a reduction in production capacity. This is avoided by supplying atomized water (z), as shown in the attached process flow diagram, to the pyrolysis gas (y') to manage its humidity and temperature. When a steam flow (z') is directed, together with the pyrolysis gas (y), in a counterflow relative to the longitudinal direction (s) of the process space towards the supply end (I) of the conveyor system, the process between the steam and the raw material to be processed reaches its highest possible degree of efficiency; subsequently, in another preferred representation of the method, the unburned biochar (x') to be produced is cracked and cooled by the action of the steam before being extracted from the conveyor system (3). In another preferred representation for a method of the invention, the raw material to be processed (x) is treated in the process space (2) with the conveyor system (3) which is located at an overpressure relative to it and is provided with supply and discharge elements (la, 1b) which are fundamentally airtight with respect to the environment, which is usually preferably implemented using one or more continuously adjustable electric screw conveyors, such as variable speed driven ones (3a) or similar. By supplying the conveyor system (3) with the raw material to be processed, it is possible to use, e.g., the method and supply system according to Finnish patent no. 119125, especially to implement the supply of the raw material to be processed from above; thus, it will originate, firstly, in a continuous manner and, secondly, in such a way that the process gases cannot escape in an uncontrolled manner from inside the conveyor system or from the process space into the environment. In another preferred representation, the conveyor system (3) is heated immediately in the most effective manner after being introduced into the process space (2) by one or more gas burners (7, 7a) mounted on an inlet wall (2a) of the process space, in codirectional relation to the conveyor system. In another preferred embodiment, the conveying capacity of a conveyor (3), such as that of one or more screw conveyors (3a), can be substituted in the longitudinal direction (s) of the process space, particularly to reduce the thickness of the raw material layer (x) from the supply end (I) of the conveyor system (3) to its discharge end (II). Therefore, the conveyor system (3) can preferably be implemented, e.g., with a screw conveyor (3a) equipped at its upstream end with a smaller pitch and at its downstream end with a larger pitch. It is also possible to implement the air supply for an air burner mechanism (7), such as one or more parallel gas burners (7a), with a separate combustion air fan. Alternatively, it is also possible, in conjunction with the gas burner (7a), to preferably use, for example, an exhaust fan to draw the pyrolysis gas (y) through an exhaust nozzle leading to the gas burner. In another preferred embodiment, a method of the invention can also process dissimilar raw materials (x, w) by transferring them, as shown, e.g., in the accompanying process flow diagram, within the conveyor system using separate supply elements (la); subsequently, the supplied raw materials are fused together as they are pushed by the screw conveyor (3a) into the processing space. In this context, it is also possible to proceed in such a way that several raw materials are mixed together in a separate mixing space and supplied to the conveyor system (3) using a single supply element. In another preferred embodiment, nitrogen reduction is carried out in the process space, performed, for example, by the so-called SNCR (selective non-catalytic reduction) method, employing an additional nozzle mechanism (Is) to supply the combustion chamber 4 with a medium containing ammonia, such as urea spray, aqueous ammonia solution, or the like. By placing the aforementioned nozzle system at a point marking the end of a gas flame combustion zone, the medium sprayed by the nozzle mechanism evaporates, so that the resulting ammonia mixes and has sufficient time to have a significant effect on the exhaust gases for a substantial nitrogen reaction to occur. Additionally, in one method of the invention, it is also ensured, preferably, for example, by means of a lambda sensor, that the combustion is continuously supplied with excess air. In another preferred representation of the invention, supplying additives to the unburned biochar to produce (x') is carried out by mixing water (z) to be conveyed to the transport system (3). On the other hand, the invention also refers to an apparatus for implementing the aforementioned method, which includes: - supply elements (la) for introducing raw material for processing (x) into a conveyor system (3) that is present in, and close to, a Thompson Converter-type process space (2), for moving the raw material for processing (x) through the process space (2) in the longitudinal direction (s) of the process space, - a flow arrangement (8) for directing the pyrolysis gas (y), generated from the raw material for processing (x) present in the conveyor apparatus (3) as a result of the heat transferred from the process space, out of the conveyor apparatus for combustion in the combustion chamber (4) of the process space, - a discharge mechanism 5 for extracting the resulting exhaust gas (y') from the process space,- discharge elements (Ib) for extracting the unburned biochar produced (x') from the conveyor system for further processing and - a gas burner system (7) preferably operating continuously to burn the pyrolysis gas (y), wherein the heat transfer from the conveyor system (3) to the process space (2) is adapted to occur by direct radiation primarily from a flame of the gas burner system (7) and from the walls of the combustion chamber (4). Furthermore, the flow of pyrolysis gas (y) passing through the conveyor system (3) occurs in a counterflow towards a supply end (I) of the conveyor system to transfer the heat present in the pyrolysis gas to the feedstock to be processed (x).moving it in the opposite direction (s) and to supply cooled pyrolysis gas (y) to the gas burner mechanism (7). The apparatus also includes a supply mechanism (1c) for directing water (z) into the conveyor system (3) to reduce / eliminate with steam (z') the amount of PAH compounds contained in the unburned biochar to be produced (x'), the supply system (1c) being adapted to direct water into the conveyor system (3) to its discharge end (II) of the conveyor system to transport the steam flow (z') together with the pyrolysis gas (y) in the longitudinal direction (s) of the process space towards the supply end (I) of the conveyor system. With regard to the accompanying process flow diagram, in a preferred embodiment of the invention, a discharge pipe (la') is provided for pyrolysis gas in an upward longitudinal direction from the raw material supply system (la). The accompanying process flow diagram also shows a supply arrangement (le) for providing nebulized water to the pyrolysis gas (y') to regulate its humidity and temperature. Furthermore, the apparatus preferably includes a cooling mechanism (Id) for cooling the unburned biochar produced (x') with a water / steam circulation system, preferably implemented on the counterflow principle. In another preferred representation of the apparatus, it comprises a conveyor system (3), housed in the process space (2) which is located at an overpressure relative to it and is provided with supply and discharge elements (la, Ib) which are essentially airtight with respect to the environment, the benefits of which have already been described above. It is obvious that the invention is not limited to the representations presented or described above, but can be varied according to the basic concept of the invention to meet the intended uses and applications. In this respect, it is clear, firstly, that with regard to the combustion process, the method can be managed by using conventional automation and control technology per se, e.g., with oxygen analyzers and temperature sensors required in the combustion of pyrolysis gas and / or by employing, for example, a preheating burner. Accordingly, for processing the raw material, it is possible to equip the screw conveyor system with the necessary monitoring systems to facilitate optimal carbonization and final temperature, e.g., by stepless control of the screw conveyor system's operation.Naturally, it is also possible that the apparatus to which a method of the invention is applied may preferably be equipped, e.g., with optical flame monitoring analyzers, e.g., with a torch tube (12) according to the illustrations, which is connected to the conveying system and through which the pyrolysis gas can be released, if necessary, by combustion with an independent burner, wherein the torch tube would function as a discharge valve and allow for a quick emergency shutdown of the apparatus.

Claims

CLAIMS 1. First, the invention relates to a method for the thermally treated production of unburned biochar, with the same functionality as a heat sink; the aforementioned method includes introducing a raw material to be processed (x) with supply elements (la) inside a conveyor system (3), which is present in a Thompson Converter-type process space (2) and in a close position, to move the raw material to be processed (x) through the process space (2) in a longitudinal direction (s) of the process space, where the pyrolysis gas (y), generated from the raw material to be processed (x) existing in the conveyor apparatus (3) as a result of the heat transferred from the process space, is conducted from the conveyor mechanism to be burned in a combustion chamber (4) of the process space,the resulting exhaust gas (y') being extracted from the process space by means of a discharge mechanism (5) and the unburned biochar produced (x') is removed from the conveyor system with discharge elements (Ib) for further processing, wherein the pyrolysis gas (y) is burned with a preferably continuously operating gas burner system (7) and the heat transfer for the conveyor system (3) in the process space (2) is directed by essentially direct radiation from a flame of the gas burner system (7) and from the walls of the combustion chamber (4),and where the pyrolysis gas (y) is conveyed by the conveyor system (3) in a counterflow relative to the longitudinal direction (s) of the process space towards a supply end (I) of the conveyor system to transfer the heat present in the pyrolysis gas to the feedstock to be processed (x) moving in the longitudinal direction (s) of the process space and to supply the cooled pyrolysis gas (y) to the gas burner system (7), characterized in that the amount of PAH compounds contained in the unburned biochar to be produced (x') is reduced / eliminated by steam (z') by supplying water (z) into the interior of the conveyor system (3),and being conveyed into the conveyor system (3) from its discharge end (II) to transport the steam flow (z') together with the pyrolysis gas (y) in a counterflow relative to the longitudinal direction (s) of the process space towards the supply end of the conveyor system (I).

2. The method corresponding to application 1, characterized in that the pyrolysis gas (y') produced is extracted in the longitudinal direction (s) from the z / pzLn / Lznz / e / YiAi process space (2) before the supply (la) of the raw material to be processed (x).

3. The method corresponding to application 1 or 2, characterized in that the unburned biochar to be produced (x') is cracked and cooled by the action of water vapor before its extraction from the conveyor system (3).

4. The method corresponding to any of the above applications 1-3, characterized in that the raw material to be processed (x) is treated in the process space (2) with the conveyor system (3), which is under overpressure and is provided with supply and discharge elements (la, Ib) that are fundamentally airtight with respect to the environment.

5. The method corresponding to any of the above applications 1-4, characterized in that the supply of additives to the biochar to produce unburned (x') is carried out by mixing water (z) to be conveyed to the transport system (3).

6. An apparatus for producing unburned biochar with heat treatment, comprising the aforementioned apparatus: z / pzLn / Lznz / e / YiAi - supply elements (la) for introducing raw material for processing (x) into a conveyor system (3) that is present in, and close to, a Thompson Converter-type process space (2), for moving the raw material for processing (x) through the process space (2) in the longitudinal direction (s) of the process space, - a flow arrangement (8) for directing the pyrolysis gas (y), generated from the raw material for processing (x) present in the conveyor apparatus (3) as a result of the heat transferred from the process space, out of the conveyor apparatus for combustion in the combustion chamber (4) of the process space, - a discharge mechanism (5) for extracting the resulting exhaust gas (y') from the process space,- discharge elements (Ib) for the extraction of the unburned biochar produced (x') from the conveyor system for further processing and - a gas burner system (7) preferably operating continuously to burn the pyrolysis gas (y), wherein the heat transfer from the conveyor system (3) to the process space (2) is adapted to occur by direct radiation primarily from a flame of the gas burner system (7) and from the combustion chamber walls (4), and wherein the pyrolysis gas (y) is conveyed by the conveyor system (3) in a counterflow towards the supply end (I) of the conveyor system to transfer the heat present in the pyrolytic gas to the feedstock to be processed (x), moving in the opposite direction (s) and to supply the cooled pyrolysis gas (y) to the gas burner system (7),characterized in that the apparatus also includes a supply mechanism (1c) for directing water (z) into the conveyor system (3) to reduce / eliminate with water vapor (z') the amount of PAH compounds contained in the unburned biochar to be produced (x'), the supply system (1c) being adapted to direct water (z) primarily to its discharge end (II) of the conveyor system to transport the steam flow (z') together with the pyrolysis gas (y) in a counterflow with respect to the longitudinal direction (s) of the process space towards the supply end (I) of the conveyor system.

7. The apparatus corresponding to application 6, characterized in that the supply arrangement (1c) is adapted to discharge the pyrolysis gas (y') that will be produced in the longitudinal direction (s) of the process space (2) before the supply (la) of the raw material to be processed (x).

8. The apparatus corresponding to application 6 or 7, characterized by including a conveyor system (3), housed in the process space (2) which is located at an overpressure relative to it and is provided with supply and discharge elements (la, Ib) which are fundamentally airtight with respect to the environment.