Process and system for pyrolysing organic materials and material mixtures

Abstract

The invention relates to providing a pyrolysis process for producing pyrolysis coke from organic material, which process functions continuously and is scalable. The pyrolysis takes place in a rotary kiln (2) by direct contact with a hot gas as the thermal transfer medium without the addition of an agent for partial oxidation, wherein the hot gas is generated in a combustion chamber (6) by combusting pyrolysis gas, wherein the combustion air is preheated in an air preheater (10) in order to ensure ignition. In the process, the hot gas is generated as a thermal transfer medium in a combustion chamber (6) by partially combusting a partial amount of the pyrolysis gas with a controllable amount of preheated air; is added to the rotary kiln at the coke discharge; and is conveyed through the rotary kiln counter to the flow of the material to be pyrolysed, the feedstock (1). The partial flow of pyrolysis gas to be partially combusted is removed from the overall flow immediately after the pyrolysis, that is to say after charging (3) the feedstock, and is conveyed by means of a conveyor element (5), steam ejector or mechanical fan to the combustion chamber (6). The air is pre-heated advantageously by the exhaust gas of the remainder of the pyrolysis gas to be combusted in the combustion chamber (7) in the flue-gas air pre-heater (10). The feedstock to be pyrolysed can be, but does not have to be, pre-dried.

Description

Process and system for the pyrolysis of organic substances and mixtures The invention relates to a method and a system for the pyrolysis of organic substances and mixtures of substances, in which the organic substances are pyrolyzed in a pyrolysis reactor designed as a rotary kiln by contact with a hot gas as a heat transfer medium due to direct heat exchange without the addition of an agent for partial oxidation, in which furthermore the hot gas as a heat transfer medium is generated in a combustion chamber from pyrolysis gas by combustion, which is previously preheated to a high temperature to ensure ignition, according to the preamble of claims 1 and 9. Pyrolysis is a thermochemical process in which organic materials, substances, or mixtures of substances are decomposed by heat in the absence of oxygen or with a limited amount of it. Pyrolysis of biomass, i.e., heating in the absence of oxygen, leads to a high coke yield when carried out slowly for longer than about 30 minutes, whereas rapid pyrolysis primarily results in condensable products such as wood tar. However, this process is primarily focused on the production of pyrolysis coke, meaning the biomass to be pyrolyzed spends a long time in the pyrolysis reactor [1]. The production of pyrolysis coke from wood is a millennia-old technique for obtaining a reducing agent for ore smelting. Pit furnaces, charcoal kilns, and retorts represent batched, i.e., non-continuous processes that are well-known and have formed the standard for centuries, and in some cases still do today. One example is the Reichert retort, part of the Degussa process; seven of these are still in operation today at proFagus in Bodenfelde / Weser, the last large-scale plant in Germany (https: / / profaqus.de / unternehmen / F2). In contrast to traditional In retort processes, in which the retort is heated from the outside, it is heated directly with the help of hot gas, which is obtained from the combustion of volatile components of the pyrolysis and flows through the retort from top to bottom through the substrate to be coked. Continuous processes, on the other hand, have only been known since the 1940s [3,4]. Continuous processes are gaining in relevance due to the increasing demand for biochar not only for new, immediate applications, but also for the storage of solid carbon, thus permanently removing it from the atmosphere. A process still in use today is the Lambiotte retort, which, as mentioned, originated from the French SIFIC process in the 1940s and is still licensed, but no longer manufactured, by Lambiotte & Cie. Brussels (www.lambiotte.com / carbonization [5], www.baltcarbon.lv [6]). This is a cylindrical reactor, with a moving bed of biomass flowing vertically from top to bottom. In the upper section, a hot gas consisting of recirculated pyrolysis gas is passed from bottom to top in cocurrent with the pyrolyzing substrate. Air is added to the hot gas for partial, i.e., incomplete combustion, in order to increase the heat content of the hot gas and thus adapt it to the requirements of the process. In the lower part, “cold gas” flows in countercurrent to the pyrolysis coke, i.e. purified pyrolysis gas freed from condensates for the purpose of cooling the pyrolysis coke under strict exclusion of atmospheric oxygen.Biomass feed and pyrolysis coke discharge are controlled by gate valves to minimize air ingress into the system. The Lambi otte retort represents a significant simplification of the somewhat older French SIFIC process [3], in which hot gas is generated in a side-mounted combustion chamber halfway up the retort. This gas then flows upwards in countercurrent to the substrate and is discharged at the top. Lam bi otte retorts built to date, with a clear diameter of 3.0 m and a cylindrical length of 18 m, are limited to producing 2,200 t / a of pyrolysis coke. However, in larger reactors, it would be difficult to distribute the introduced biomass evenly across the cross-sectional area to ensure a uniform flow of hot gas through the bed. The required penetration depth and mixing of the air required for partial oxidation with the hot gas cannot be satisfactorily achieved in this way. Both are essential, however, for producing pyrolysis coke of consistent, high quality. The reactor is fed and unloaded by periodic loading and unloading using a lock system. The development of continuous processes, however, has shifted away from retort-like moving-bed systems. A number of continuous processes now exist, even if one disregards the rapid fluidized-bed pyrolysis, which produces little pyrolysis coke and predominantly condensable liquid products. There are two main approaches: Firstly, the reactors have internal mechanical conveying devices, such as screws; secondly, there are rotary kilns, which either have a jacket heated by hot gas, electrically, or by other means, or are penetrated by static heating elements, as well as hybrids of both. From the patent specification DE10 2005 045166 B4 [7] a process for the production of biocoke is known, in which the biomass to be pyrolyzed is conveyed through a heated reactor by means of mechanical forced conveyance and pyrolyzed in the process. The reactor is heated indirectly, i.e. from the outside, to pyrolysis temperatures of around 600 °C or higher. For this purpose, hot exhaust gas, which is obtained by the combustion of the pyrolysis gas, flows through the outer jacket. This process works without partial oxidation, i.e. by adding far substoichiometric amounts of air. The process has been introduced commercially for various plant material and sewage sludge, materials that can be fed into the reactor in a fine particle size. Another process is described in patent AUOO 2013 308399 B2 [8]. This can be carried out as a batch process or continuously, both of which are commercially available. The conveying technology through the reactor is not described in detail there. However, in contrast to the previously described process, the key feature here is that air is added along the length of the reactor for partial oxidation, thus eliminating the need for external heating. These are just two examples of numerous other processes in which transport through the pyrolysis reactor is accomplished using internal conveying elements. All of these have the disadvantage that these conveying elements are limited in size. Firstly, they must be made from very high-quality and therefore expensive steels, and secondly, above a certain size, they can no longer be easily removed for maintenance purposes. These are just two of several problems that prevent these processes from being scalable within a single process line; instead, this must be accomplished across several process lines arranged in parallel. Furthermore, when using air for partial oxidation, uniform distribution across the entire gas stream is more or less difficult and complex, depending on the process. This disadvantage is apparently avoided with externally heated rotary kilns - rotary kilns heated from the inside with heating tubes such as the Siemens smoldering incineration process for domestic waste

[0017] should only be considered marginally here, since these can have a detrimental effect simply due to the mechanical interaction of these heating elements with the pyrolysis material. However, there are limits to scalability here too: If it is realistically assumed that the residence time in order to obtain a constant, equivalent product must be constant regardless of the throughput, if it is further assumed that the residence time is at least proportional to the quotient of the volume of the pyrolysis reactor and the volume flow of the input material, then the volume of the reactor, in an analysis that abstracts from the shape of the reactor, grows to the third power, while the heating surface grows quadratically. In a more concrete analysis using a circular-cylindrical rotary kiln, whose length is to be kept constant in order to maintain a constant residence time with a constant inclination, the clear cross-sectional area grows proportionally to the throughput, but the diameter and thus the surface area (px D) only grows with the square root of the throughput. It follows that the increase in the heat input area does not keep pace with the growth in throughput upon scaling.This disadvantage could be avoided with heating tubes that are guided through the furnace but do not rotate, as mentioned above, because the number of heating tubes could be increased proportionally to the increase in the cross-sectional area. However, as already mentioned, the disadvantage remains that pyrolysis material can become stuck to these heating tubes. A further characteristic of the aforementioned processes is that they require feedstock pre-dried to at least 75% dry matter content. This requirement may be omitted if these processes include partial oxidation of the material to be pyrolyzed. However, the latter generally comes at the expense of the pyrolysis coke yield. The specifications for the feedstock to be pyrolyzed are not clearly defined in the invention described in DE-PS 698 12 932 T2 [9] (translation of EP 0 985 009 B1

[0010] ). Here, the heat supply is reduced to a tube arranged axially in the rotary kiln, within which the at least partial combustion of the pyrolysis gas takes place, which is staged over the entire length and functions as a radiant heat exchanger. The staged combustion over the length creates a temperature profile for optimal control of the pyrolysis. The pyrolysis gas is fed from a "reversing chamber" at the outlet of the rotary kiln The air is extracted, and the combustion air is supplied through an air lance extending into this tube, which serves as a radiant heat exchanger. The key feature here is that the inner wall is heated by radiant heat, and this heat is transferred to the material being pyrolyzed. The required length of the slender air lance extending into the heat exchanger tube is considered a disadvantage. Furthermore, it is foreseeable that both the lance and the heat exchanger tube must be made of very high-quality and expensive materials, which are particularly susceptible to oxidizing conditions from the inside and reducing conditions from the outside. A simpler method for conducting pyrolysis would be to directly expose the feedstock to a hot gas stream. While this would require dilution of the pyrolysis gas by the hot gas, this disadvantage is less significant if the desired pyrolysis product is pyrolysis coke, while the pyrolysis gas is merely combusted, and the pyrolysis apparatus becomes simpler compared to other pyrolysis processes. Direct exposure of material to be gasified allothermally to a hot gas is known from DE-PS 197 36867 C2

[0011] . However, this method aims at allothermal gasification with full conversion of the organic material; pyrolysis coke is not the desired product. The implementation of pyrolysis by direct heat transfer from a hot gas to the material to be pyrolyzed is indirectly described in DE-PS 10 2009 014884 B4

[0012] : Here, dewatered sewage sludge is passed through a rotary kiln in countercurrent to an oxidizing hot gas, so that two zones are formed in the flow direction of the sewage sludge, first an oxygen-free, "reducing" zone, then an "oxidizing" zone, in which the pyrolysis coke burns out with the help of the oxygen contained in the hot gas, thus is not obtained as a product. In principle, it should be noted that such a plant has been in operation since the 1980s in the waste incineration plant in Oftringen / AR (Switzerland) is engaged in the disposal of sewage sludge, so that the invention described in the aforementioned patent application has been filed for patent under the generic term "Process for the elimination of heavy metals from sewage sludge from industrial or municipal plants." However, this raises the problem of the oxidizing zone in which the coke, i.e. the product, is burned. Another approach for carrying out pyrolysis by direct heat transfer from a hot gas is provided by the disclosure of patent application US 2014 / 0166465 A1

[0013] : Here, too, hot flue gas is passed through a rotary kiln in countercurrent to the material to be pyrolyzed. This hot flue gas is generated by combusting all of the pyrolysis gas leaving the rotary kiln at the head end, extracting heat from the flue gas thus produced in a heat exchanger, cleaning the flue gas thus cooled in several stages, and branching off a partial stream from the flue gas before it is released into the atmosphere. This branched partial stream is then reheated in the aforementioned heat exchanger, as stated, by cooling the exhaust gas after the pyrolysis gas has been completely burned, and is finally fed to the rotary kiln at the foot end. The burner shown in

[0013] is only used for the initial heating during start-up operation. The first disadvantage here is the gas-to-gas heat exchanger, which is installed downstream of the pyrolysis gas combustion. This is exposed to very high temperatures, at least as far as the fresh flue gas is concerned, and must therefore be made of very high-quality material and, depending on the pyrolysis material, is also exposed to corrosion under these conditions. Furthermore, clogging by fly ash must be expected. Finally, the heat exchanger becomes very large if pyrolysis is to be carried out at high temperatures. Another disadvantage is that the pyrolysis process, due to the use of exhaust gas from a complete combustion, nor oxygen, which leads to partial combustion of the pyrolysis material or the pyrolysis coke product. Accordingly, due to these disadvantages, the process described in

[0013] is not used for pyrolysis, but only for the much milder process of roasting ("torrefaction") up to 400 °C. For this purpose, material is used that is previously pre-dried to 10% residual moisture, as can be seen from the chapter "Examples" in [13}, paragraphs

[0049] -

[0067] emerges. In addition, European patent application EP 3 831 912 A1 should also be mentioned

[0014] . However, the focus here is not on the production of pyrolysis coke, but rather pyrolysis is the first stage of at least two-stage combustion of the solid. The gas-side process largely corresponds to that in

[0013] . However, the quantities and oxygen contents of the recirculated exhaust gases differ, since in

[0014] the objective is not to obtain pyrolysis coke or a roasted product. According to the invention, ash is removed from the pyrolysis stage in

[0014] . For this purpose, the recirculated exhaust gas or the primary air supplied to the pyrolysis stage must contain oxygen (

[0014] , claim 5). Another possibility is to carry out pyrolysis by heat transfer in direct contact with a hot medium. This consists in pyrolysis in a reactor in which the material to be pyrolyzed is brought into contact with a hot bulk material. The pyrolysis coke produced is then separated from this bulk material after passing through and completing pyrolysis. This procedure is disclosed, for example, in DE-PS 103 33279 B4 (hot raw meal,

[0015] ) or DE-PS 199 45771 CI (circulating, ceramic heat transfer bodies,

[0016] ). In the latter, pyrolysis is a sub-step. In

[0015] , the hot bulk material raw meal, which is readily available in cement works and the like, was used as an attractive heat transfer medium, and in

[0016] the possibility of reforming the gas produced in pyrolysis with steam in another reactor to obtain a hydrogen-rich gas. The disadvantage here is the high technical The effort required for mechanical conveying, screening, etc., of a hot bulk material, as well as the requirement of a suitable industrial environment, are significant. Therefore, this approach is not pursued here. The present invention is based on the object of providing a simple, continuously operating process for the production of pyrolysis coke, which is fundamentally scalable as required with regard to throughput and thus production capacity and avoids the aforementioned disadvantages: mechanical transport elements located in the reactor such as screws, apron conveyors, etc., indirect heat exchange with its disadvantages, partial oxidation of the pyrolysis material or the pyrolysis coke and the necessity of using complex pre-dried material. This object is achieved by the features of claims 1 and 9. The invention advantageously provides that the pyrolysis gas is previously extracted as a controllable partial flow from the total flow of pyrolysis gas directly after pyrolysis and is recirculated by means of a conveyor device (5) into the aforementioned combustion chamber 6, wherein the combustion of this partial flow is incomplete, wherein the air content is controllable, wherein the hot exhaust gas of this combustion chamber (6) is fed as a whole to the rotary kiln (2) on the discharge side of the pyrolysis coke and is passed through the rotary kiln (2) in countercurrent to the material to be pyrolyzed, The pyrolysis reactor can be a thermally insulated pyrolysis reactor. The advantage of the present invention is that the heat required to carry out the pyrolysis can be provided by means of a non-oxidizing hot gas in direct heat exchange, in such a way that the resulting coke is not burned partially, but not at all. The process according to the invention is to be operated continuously, although the feed materials do not have to be added continuously, but can also be added batchwise at intervals such that the intervals are significantly shorter than the residence time of the material to be pyrolyzed, so that the composition of the pyrolysis gas is constant over the operating period, subject to only slight fluctuations. The central component is the pyrolysis of the feed materials in a rotary kiln, which preferably includes impeller elements integrated into the inner wall to convey the pyrolysis material, as well as blades in the feed material inlet area for repeated turning over if the material is not dried and therefore may not flow sufficiently. Otherwise, however, no internal components are preferably provided. However, the rotary kiln is preferably lined with bricks and insulated. The primary goal here is to minimize heat losses, ideally to zero, if this is possible at a reasonable cost. In the rotary kiln, a hot gas, preferably essentially oxygen-free, is passed countercurrently to the pyrolysis material, causing both the pyrolysis and the initial drying of the pyrolysis material. However, an oxidation zone is generally not provided in the rotary kiln. The supply of heat to the pyrolysis process is achieved by a variable first partial flow of the pyrolysis gas, not from flue gas that may still contain oxygen from the combustion of pyrolysis gas as in [13, 14], which is taken from the main flow immediately after passing through the feedstocks fed into the rotary kiln and leaving the rotary kiln, is conveyed back to the end of the rotary kiln and there is partially combusted by adding preferably highly heated air and is thus heated to the required inlet temperature before it re-enters the rotary kiln to release its heat back to the pyrolysis process. It is essential that the partial combustion takes place outside the Pyrolysis process takes place so that no pyrolysis coke burns. Complete burnout of the recirculated pyrolysis gas is not the goal; rather, what is preferably required is a sufficient quantity of an oxygen-free, non-oxidizing gas, which may still contain unburned material, even in high concentrations, but in which no residual oxygen is present to provide the heat for drying, heating, and pyrolysis of the feedstock—the latter provided the pyrolysis is not already slightly exothermic. The desired temperatures of the hot gas at the rotary kiln outlet and of the mixture of pyrolysis gas and hot gas cooled after the pyrolysis reaction at the kiln inlet determine the heat made available for pyrolysis and thus also the quantity of gas. The task of partial combustion, i.e., the incomplete combustion of pyrolysis gas, outlined above, is best achieved by a burner muffle, which, in a preferred embodiment, extends the rotary kiln downstream after the discharge of the finished pyrolysis coke, but does not rotate itself. Within the burner muffle, stable ignition can be achieved through suitable flow guidance with the help of swirling of the pyrolysis gas, as well as the highly preheated air and, associated with this, flame stabilization through backflow, thus completely consuming the oxygen. This consuming does not have to be perfect: While post-combustion in the rotary kiln does not interfere with pyrolysis to a small extent, it is not the desired effect.Due to local immiscibility, very low oxygen concentrations can occur and coexist with combustibles even in the present case, on the order of well below 1%, which can even be carried through pyrolysis if this immiscibility can be maintained. The conveying device can be a blower, preferably a radial blower, and / or a steam jet ejector. The recirculation itself is the most technically demanding task within the overall process: The pyrolysis gas has just passed through the feedstock, is still hot, may contain dust, and will certainly contain condensable material. Furthermore, the pyrolysis gas is flammable and can therefore form ignitable mixtures. It must be compressed to approximately 20–50 hPa overpressure relative to atmosphere to create the path to the lower end of the rotary kiln with the burner muffle and coke discharge, which is provided without any internals. A jet pump or ejector powered by steam generated from the waste heat of the pyrolysis gas burned at the end of the process to generate heat is ideal for this purpose and is generally considered feasible. Alternatively, a radial fan can be used, which can convey gases at temperatures up to 400°C. Such a fan would have to be certified according to the ATEX Directive, which explicitly applies only to atmospheres at ambient temperature, assuming Zone 2, since ignitable or potentially explosive mixtures (GEA) cannot form during normal operation. When using a steam injector instead of a fan, it should be noted that the recirculated gas also contains water vapor, thus the calorific value is lower than when using a fan. This may limit the acceptable moisture content of the biomass. The second partial stream of the pyrolysis gas is preferably the amount of pyrolysis gas that is not recirculated. The second partial stream of the pyrolysis gas is preferably discharged into another combustion chamber and burned there. The resulting waste heat can be used: firstly, it can be used to preheat the air for partial combustion to approximately 500 °C; secondly, it can be used to generate steam or hot water for use inside or outside the plant, or to perform another type of waste heat utilization. However, this can be done without direct reference to the process according to the invention. However, since this gas can have a very low calorific value when very humid If biomass is used in pyrolysis, a suitable combustion technology may need to be used, with high air preheating, recuperation or similar. The volume of the first and / or second partial stream can be adjustable. An overall advantage of this process is that both the recirculated volumes, thus the amount of hot gas, and the inlet and outlet temperatures of the hot gas can be adjusted within a wide control range: First, the volume of recirculated gas, i.e., the first partial stream, can be adjusted using the conveying device (e.g., the steam ejector or blower). Then, by appropriately adjusting the air volume for partial combustion, the inlet temperature of the hot gas into the rotary kiln can be adjusted. The outlet temperature of the pyrolysis gas mixture from the kiln is then adjusted by further adjusting the recirculation volume and then the air volume for partial combustion. Overall, this is a cascading control system.With their help, the pyrolysis conditions can then be adjusted very precisely to the product requirements of the pyrolysis coke, which is expected to be more precise than with all other processes according to the state of the art outlined and, above all, significantly less sluggish. A further advantageous embodiment may consist in the partial combustion being placed in a first stage upstream of the steam ejector or the radial blower mentioned above, so that it is possible to allow a lower outlet temperature of the pyrolysis gas from the rotary kiln and thus reduce the extent of partial combustion and the amount of recirculated gas, but still largely prevent possible tar deposits in the recirculation. Another advantageous design option is to connect the blower and the ejector in parallel, to use the more energy-efficient blower in normal operation, and in the event of a blower failure or in a In case of danger, switch immediately to the steam ejector in order to suppress mixture formation from the outset. Finally, the process offers the particularly uncomplicated possibility of adding steam to the hot gas in order to achieve increased activation or surface formation in the pyrolysis coke produced. Finally, a further advantageous embodiment is that a set of regenerators connected in parallel can be used for air preheating, which are alternately heated with exhaust gas from the pyrolysis gas combustion chamber and then cooled by preheating the combustion air for the combustion chamber in the pyrolysis gas circuit. According to the present invention, a system for the pyrolysis of organic substances and mixtures of substances is also provided, comprising at least one pyrolysis reactor designed as a rotary kiln, in which organic substances or mixtures of substances can be pyrolyzed by contact with a hot gas as a heat transfer medium due to direct heat exchange without the addition of an agent for partial oxidation, at least one combustion chamber in which the hot gas as a heat transfer medium can be generated by the combustion of pyrolysis gas with the supply of air introduced into the combustion chamber, at least one air preheater designed to preheat the air therein before it is fed into the combustion chamber, wherein at least one conveying device is provided, wherein at least a first partial flow of the pyrolysis gas emerging from the pyrolysis reactor can be fed into the conveying device and introduced into the combustion chamber by means of the conveying device,wherein the proportion of air that can be introduced into the combustion chamber is controllable in such a way that the combustion of the first partial flow of the pyrolysis gas carried out in the combustion chamber with the supply of air is incomplete, wherein the pyrolysis reactor has a discharge side at which the pyrolyzed material is discharged, and wherein the material from the combustion chamber, escaping hot gas can be fed to the pyrolysis reactor designed as a rotary kiln on the discharge side, whereby the hot gas can be passed as a heat transfer medium in countercurrent to the material to be pyrolyzed through the pyrolysis reactor designed as a rotary kiln. The material to be pyrolyzed is the organic substances and mixtures of substances intended for pyrolysis. The pyrolysis reactor can be a thermally insulated pyrolysis reactor. The organic substances or mixtures of substances to be pyrolyzed in the pyrolysis reactor can be moist and not dried, with the moisture content preferably being a maximum of 50%. The first partial flow of the pyrolysis gas can be partially combusted incompletely in a first stage upstream of the combustion chamber in the flow direction by supplying air, whereby the first stage of partial combustion can be arranged upstream of the blower in the flow direction. The conveying device can be a blower, preferably a radial blower, and / or a steam jet ejector. As a conveying device, a mechanical blower, preferably a radial blower, and a steam jet ejector can be connected in parallel, of which at least one blower is in operation, but both blowers can also be operated simultaneously. The air preheating can be carried out with the aid of at least a second partial flow of the exhaust gas of the outflowing, burned pyrolysis gas with the aid of at least one regenerator, wherein preferably at least two regenerators are arranged in parallel, which can be switched at intervals between heating with the said hot exhaust gas and the heat transfer to the air to be heated. If the conveying device is designed as a steam ejector, the steam for operating the steam ejector can be generated using the waste heat from the combustion of a second partial stream of the outflowing pyrolysis gas. The combustion chamber for generating the hot gas can be designed as a burner muffle and preferably arranged directly on the discharge side of the pyrolysis reactor designed as a rotary kiln on its axis, wherein the burner muffle preferably does not rotate. In the following, embodiments of the invention are explained in more detail with reference to the drawings. They show schematically: Fig. 1 a system according to the invention Fig. 2 an alternative embodiment Fig. 1 shows a possible embodiment of the subject matter of the invention. The feedstock 1 is fed into the preferably insulated and brick-lined rotary kiln 2 via a feed device that is not process-specific but should merely be as sealed as possible from the atmosphere. The blading 3, which can preferably be provided in the inlet or feed area of ​​the pyrolysis reactor 2 designed as a rotary kiln, helps distribute the pyrolysis material across the cross-section of the rotary kiln 2. The discharge side of the pyrolysis reactor 2 is provided at the end of the rotary kiln. There, the pyrolysis coke stream 4 can be withdrawn and conditioned for further distribution or use. The latter, like the feed of the feedstock, is not process-specific. A partial flow of the gas stream or pyrolysis gas leaving the pyrolysis reactor 2, designed as a rotary kiln, at the inlet and feed area of ​​the feed material is conveyed by means of the controllable conveying device 5, which can also be called a conveying element and can be designed as a steam ejector or blower, as described in more detail below in Fig. 2, to the end of the rotary kiln, where, before re-entering the rotary kiln, the combustion chamber 6, which does not rotate with the rotary kiln, is located. There, with the addition of highly preheated air, preferably 500 °C or warmer, the hot gas is generated. This hot gas flows through the rotary kiln in countercurrent to the feed material, thus causing the pyrolysis of the feed material. A second partial stream of the pyrolysis gas, which can also be referred to as non-recirculated material, is combusted in another combustion chamber 7, where highly preheated air is also used. This applies in particular when moist feedstock 1 is used, whereas with dried feedstock, preheating can be lower or even unnecessary. The hot flue gas can then flow through the hot gas air preheater (LUVO) 10, which provides the combustion air for the entire process and is supplied with ambient air 8 via the combustion air blower 9. The LUVO can also be designed as a multi-line regenerator and arranged in the bypass to the main flue gas line, see below.The flue gas from the combustion of the effluent pyrolysis gas then passes through a steam generator 12, which converts feedwater 11 into externally usable steam 14, the motive steam 23 for the steam ejector 5, if used, and optionally into activation steam 13 for the pyrolysis coke in the rotary kiln 2. Finally, the flue gas leaves the plant via the flue gas cleaning system 15, the induced draft fan 16, and the chimney 17. There are no explicit specifications for these last three components, nor for the boiler; they are defined solely by the fulfillment of their function. Fig. 2 also shows some advantageous embodiments of the process. At the inlet of the rotary kiln, i.e., immediately upstream of the feed material inlet, is the pre-combustion chamber 21, in which the temperature of the outflowing mixture of hot gas and pyrolysis gas is raised to approximately 400°C by initial partial combustion. This prevents the condensation of tars and the like in the further flow path of this gas mixture. This makes it possible to lower the gas temperature at the start of the rotary kiln, so that the heat required for pyrolysis, including material drying, is distributed over a wider temperature range, thus significantly reducing the amount of gas that needs to be recirculated. Furthermore, the recirculation of the gas required for the operation of the pyrolysis can alternatively be effected by the blower 22 or the steam ejector 5. The steam ejector 5 is operated by the motive steam 23, which is also generated in the waste heat boiler 12. Since the ejector is a passive element, it can be made of any material and can therefore be operated on the pyrolysis gas side even at very high temperatures. In principle, it can be burned off without damage even in the case of tar deposits. Fig. 2 shows an advantageous configuration in that the ejector is connected in parallel to the radial blower: Thus, in undisturbed normal operation, the process could optionally be operated with the radial blower instead of the steam ejector, since this allows mixture formation in the sense of ais excluded, while in the event of a malfunction, if such mixture formation cannot be excluded, it can be pumped with the help of the ejector, so that safe operation can be carried out temporarily or even completely. Two further advantageous designs are shown with the bypass 24 and the regenerator LUVO 25. The bypass 24 allows flexible use of the air preheating. The multi-pass regenerator LUVO 25 with A heat storage system filled with stones or similar materials does not require complex materials, especially when compared to a recuperative heat exchanger, which requires high-temperature-resistant and correspondingly expensive steels. Consequently, very high air preheating temperatures exceeding 500°C can be achieved. The vessels of the regenerative LUVO (R-LUVO) are alternately heated either with flue gas or, after switching to supply air / combustion air, cooled by the combustion air stream, releasing heat. If the regenerative LUVO (R-LUVO) is left entirely in the main exhaust gas flow and not connected in a bypass to the main exhaust gas flow, the R-LUVO requires an internal bypass so that steam can always be fully generated in the downstream steam generator 12. Example The embodiment shown below refers to the standard variant shown in Fig. 1, which is operated with "wet" biomass as feedstock. A mechanical blower is assumed here as the conveying device 5. For simplicity, we assume a biomass with the following composition (all wt.%): 50% water content, 1% ash (corresponding, for example, to freshly felled wood with a small amount of bark), and, based on the ash-free dry matter, 50% carbon (C), 5.5% hydrogen (H), 44% oxygen (O), 0.3% nitrogen (N), 0.2% sulfur (S), and no chlorine. The composition of the ash content and the trace elements it contains are not considered as they are not relevant here. This is introduced into the process at a rate of 3,100 kg / h of original substance. With an annual operation of 8,000 h, this corresponds to an annual quantity of 25,000 t / a of input biomass. The coke yield is 29%, based on the dry matter, i.e. 449.5 kg / h. The rotary kiln is designed for a gas velocity of 1 m / s to minimize dust entrainment. It is lined to ensure mechanical stability against the solid biomass and coke. A lightweight refractory brick or soft insulation can be arranged beneath the lining. The inside diameter is 3.4 m in this example with wet biomass. For the corresponding amount of dried biomass with 15% moisture content, 2.2 m would be sufficient. In anticipation of the following considerations, it should be noted that these diameters already take into account the increased gas quantity due to recirculation. With a rotary kiln gradient of 2° from the horizontal and a target residence time of 90 minutes, this would result in a b D of 4.71 and thus a length of 16 m for the rotary kiln with wet material, 11 m for dried material. Of course, the The larger of the two rotary kilns, which was designed for wet material, can also process dried material. Now, the amount of hot gas that is passed through the rotary kiln in countercurrent to the biomass must be determined. For this purpose, the heat requirement for pyrolysis is calculated. This consists of heating the water contained therein, its evaporation, and further heating to the outlet temperature from the rotary kiln, in the example 350 °C, which requires approximately 1,332 kW; heating the dry matter to the desired pyrolysis temperature, here 600 °C, which requires approximately 331 kW; and compensating for the heat losses of the rotary kiln, in this case 1.5% of the chemical input power of the biomass, in this case 122 kW. From this heat quantity, the slight exothermicity of the pyrolysis process, assumed here to be 1,200 kJ / kg dry matter, resulting in 517 kW, as well as the contribution of the air preheating for partial combustion to 500 °C, iteratively determined to be 197 kW. There remain 1.367 kW, which must be available as sensible heat in the temperature range between the hot gas inlet, assumed here to be 750 °C, and the outlet of the mixture of pyrolysis gas and hot gas, assumed here, as mentioned, to be 350 °C. Assuming an exemplary pyrolysis coke elemental composition of 82.5% C, 2.3% H, 14.61% O, 0.39% N, and 0.2% S, the initial calculation yields a pyrolysis gas – molar balance of biomass less the resulting coke – with a calorific value of 12.36 MJ / kg dry, of which approximately 36% must be combusted. The partial combustion in the recirculated gas mixture must correspond to this. However, the actual resulting pyrolysis gas is significantly "thinner" due to the partial combustion, see below. Here, too, it should be noted that the drier the input material, the smaller the difference is, simply because less partial combustion is required. This means that 1,327 kg / h of air preheated to 500 °C must be fed into the combustion chamber at the exit end of the rotary kiln. The amount of gas to be recirculated is 6,364 kg / h, so that 3,977 kg / h of gas It can be extracted and used to generate process heat (air preheating) and other useful heat through complete combustion in a boiler with a flue gas and air preheater. This still corresponds to a thermal output of 4.3 MW. It should be noted that this gas only has a relatively low calorific value of 3.7 MJ / kg, so it must be burned with highly preheated air (500 °C). The combustion chamber is designed to achieve stable combustion with the help of strong internal recirculation and loss minimization through thermal insulation. References [1] P. Quicker, K. Weber, Biochar, Springer Vieweg Wiesbaden 2016, Chapter 3.2 83ff. [2] https: / / profaqus.de / unternehmen / [3] W. Emrich, Handbook of Charcoal Making, Kluwer Dordrecht 1985; Chap. 3, 107ff. [4] P. Quicker, K. Weber (eds.), Biochar, Springer Vieweg Wiesbaden 2016, 95f. [5] www.lambiotte.com / carbonization [6] www.baltcarbon.lv [7] DE10 2005 045166 B4, Method for generating thermal energy with a FLOX burner [8] AUOO 2013 308399 B2, Efficient drying and pyrolysis of carbon-containing material. [9] DE 698 12932 T2, Method and device for heating a rotary kiln for the gasification and pyrolysis of organic substances

[0010] EP 0985 009 Bl, Method and Apparatus for Heating a Rotary Kiln designed for Gasification and Pyrolysis of Organic Material

[0011] DE 197 36867 C2, Process for the allothermal gasification of organic substances and mixtures of substances

[0012] DE-PS 10 2009 014884 B4, Process for the elimination of heavy metals from sewage sludge from industrial or municipal plants

[0013] US Disclosure 2014 / 0166465 Al, System and Process for Conversion of Organic Matter into Torrefied Product.

[0014] EP application EP 3 831 912 A1, method and device for burning solid fuels.

[0015] DE-PS 103 33279 B4, Process and device for the pyrolysis and gasification of organic substances and mixtures containing organic components.

[0016] DE-PS 199 45771 Cl; Process for the gasification of organic substances and mixtures of substances.

[0017] U. Richers, B. Bergfeldt, The Siemens low-temperature carbonization process, Karlsruhe Research Center, Scientific Report FZKA5826. List of reference symbols: 1 - Input material 2 - Rotary kiln 3 - Blades in the inlet 4 - Pyrolysis coke discharge 5 - Conveyor for conveying the pyrolysis gas partial flow for hot gas generation, steam ejector (Fig. 2) 6 - Combustion chamber for hot gas generation 7 - Main combustion chamber for combustion of the effluent pyrolysis gas 8 - Combustion air from the environment 9 - Combustion air blower 10 - Flue gas LUVO 11 - Feed water 12 - Waste heat boiler 13 - Steam to activate the pyrolysis coke 14 - Steam for release as useful energy 15 - Exhaust gas purification 16 - Induced draft fan 17 - Chimney 21 - Pre-combustion chamber 22 - Blower, alternative, for conveying pyrolysis gas 23 - Driving steam for the ejector 24 - Bypass circuit 25 - Multi-pass, regenerative LUVO (R-LUVO)

Claims

Patent claims:

1. A process for the pyrolysis of organic substances and mixtures of substances, in which the organic substances (1) are pyrolyzed in a pyrolysis reactor (2) designed as a rotary kiln by contact with a hot gas as a heat transfer medium due to direct heat exchange without the addition of an agent for partial oxidation, in which the hot gas as a heat transfer medium is also generated in a combustion chamber (6) from pyrolysis gas by combustion, wherein the air is previously preheated in an air preheater (10) to ensure ignition, characterized in that this pyrolysis gas was previously taken as a controllable partial flow from the total flow of pyrolysis gas directly after pyrolysis and recirculated into the aforementioned combustion chamber 6 by means of a conveying device (5, 22), the combustion of this partial flow is incomplete, wherein the air proportion is controllable,the hot exhaust gas of this combustion chamber (6) is fed as a whole to the rotary kiln (2) on the discharge side of the pyrolysis coke and is passed through the rotary kiln (2) in countercurrent to the material to be pyrolyzed, 2. Process according to claim 1, characterized in that the pyrolysis can be carried out with a moist, non-dried organic substance or mixture of substances as feedstock, provided that the moisture content is not more than 50%.

3. Method according to one of claims 1 to 2, characterized in that the partial combustion is carried out in several stages, one of which is located upstream of the conveyor device (5, 22) used for recirculation.

4. Method according to one of claims 1 to 3, characterized in that the conveying device (5, 22) is a blower, preferably a radial blower, and / or a steam jet ejector.

5. Method according to claim 4, characterized in that a mechanical blower, preferably a radial blower, and a steam jet ejector are connected in parallel as the conveying device (5, 22), of which at least one blower is in operation, but both blowers can also run simultaneously.

6. Method according to one of claims 1 to 5, characterized in that the air preheating from at least a partial flow of the exhaust gas of the outflowing, burned pyrolysis gas takes place with the aid of at least one regenerator, wherein preferably at least two regenerators are arranged in parallel, which are switched at intervals between heating with the said hot exhaust gas and the heat transfer to the air to be heated.

7. Method according to one of claims 1 to 6, characterized in that when the conveying device is designed as a steam ejector, the steam for operating the steam ejector used for recirculating the partial flow of the pyrolysis gas was generated using the waste heat from the combustion of the outflowing pyrolysis gas.

8. Method according to one of claims 1 to 7, in which the combustion chamber 6 for generating the hot gas is designed as a burner muffle and is arranged directly on the coke discharge side of the rotary kiln on its axis, but does not rotate.

9. System for the pyrolysis of organic substances and mixtures of substances, with at least one pyrolysis reactor (2) designed as a rotary kiln, in which organic substances or mixtures of substances (1) are pyrolyzed by contact with a hot gas as a heat transfer medium due to direct heat exchange without the addition of an agent for partial oxidation, at least one combustion chamber (6) in which the hot gas as a heat transfer medium can be generated by the combustion of pyrolysis gas with the supply of air introduced into the combustion chamber, at least one air preheater (10) which is designed to preheat the air in it before it is fed into the combustion chamber, characterized in that at least one conveying device is provided, wherein at least a first partial flow of the pyrolysis gas emerging from the pyrolysis reactor can be fed into the conveying device and introduced into the combustion chamber (6) by means of the conveying device (5, 22), wherein the proportion of air that can be introduced into the combustion chamber (6) can be regulated such that the combustion of the first partial flow of the pyrolysis gas carried out in the combustion chamber (6) with the supply of air is incomplete,wherein the pyrolysis reactor (2) has a discharge side at which the pyrolyzed material is discharged, and wherein the hot gas emerging from the combustion chamber (6) can be fed to the pyrolysis reactor (2) designed as a rotary kiln at the discharge side, wherein the hot gas can be conducted as a heat transfer medium in countercurrent to the material to be pyrolyzed through the pyrolysis reactor (2) designed as a rotary kiln.

10. System according to claim 9, characterized in that the organic substances or mixtures of substances (1) to be pyrolyzed in the pyrolysis reactor (2) are moist and not dried, the moisture content being a maximum of 50%.

11. System according to one of claims 9 to 10, characterized in that the first partial flow of the pyrolysis gas is incompletely partially combustible with the supply of air in a first stage in the flow direction upstream of the combustion chamber (6), wherein the first stage of the partial combustion is arranged in the flow direction upstream of the blower.

12. System according to one of claims 9 to 11, characterized in that the conveying device (5, 22) is a blower, preferably a radial blower, and / or a steam jet ejector.

13. System according to claim 12, characterized in that a mechanical blower, preferably a radial blower, and a steam jet ejector are connected in parallel as the conveying device, of which at least one blower is in operation, but both blowers can also be operated simultaneously.

14. System according to one of claims 9 to 13, characterized in that the air preheating is carried out with the aid of at least a second partial flow of the exhaust gas of the outflowing, burned pyrolysis gas with the aid of at least one regenerator, wherein preferably at least two regenerators are arranged in parallel, which are switched at intervals between heating with the said hot exhaust gas and the heat transfer to the air to be heated.

15. Method according to one of claims 9 to 14, characterized in that when the conveying device is designed as a steam ejector, the steam for operating the steam ejector can be generated with the aid of the waste heat from the combustion of a second partial stream of the outflowing pyrolysis gas.

16. Method according to one of claims 9 to 15, in which the combustion chamber (6) for generating the hot gas is designed as a burner muffle, and preferably directly on the discharge side of the rotary kiln formed pyrolysis reactor (2) is arranged on its axis, wherein the burner muffle preferably does not rotate.

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