METHOD FOR CLEANING MINERAL SOLIDS AND WOOD MATERIALS, DEVICE FOR THIS METHOD AND USE THEREOF

Description

[0001] The invention relates to a method for cleaning mineral solids, mixtures thereof and / or wood materials, a device which can be used in this method and the use of the device for cleaning these materials.

[0002] DE3443039A1, DE102014108337A1, and EP000002412783A1 describe processes in which oil, bitumen, tar, or pitch are dissolved in solvents, thus treating the contaminated solids. The advantage of these dissolution and extraction processes is that high temperatures are not required for treatment. This saves energy and does not damage the solids or solid mixtures. The disadvantage of these processes is that large quantities of solvent are required to dissolve the hydrocarbon compounds, which then have to be further processed and purified. These additional process steps require additional equipment and thus higher investment costs. The energy required for solvent treatment represents a further cost factor, as does the solvent itself, which is an additional consumable.

[0003] DE10354242B3 describes a process for the microbiological decontamination of road demolition material contaminated with pollutants, in particular road demolition material containing pitch and containing PAHs (polycyclic aromatic hydrocarbons) and / or phenols. Another advantage of this process is that high temperatures are not required for treatment. This saves energy and prevents damage to the solids or solid mixtures. A disadvantage of this process is that microbial degradation processes are very slow. These slow degradation processes lead to very long residence times for the material being treated in the process, which in turn reduces the economic viability of the process.

[0004] DE19833430A1, DE60010533T2, E50932B, EP245655A2, EP1022391A1, and DE102009025361B4 describe processes in which road rubble or contaminated soil is thermally treated. The thermal treatment involves either direct oxidation of the organic contaminants, binders, and / or contaminants, or volatilization of these same substances at elevated temperatures followed by post-combustion of the resulting vapors and gases. The advantage of these processes is that, at sufficiently high temperatures, the organic contaminants, binders, and / or contaminants can be completely removed with relatively short residence times. A disadvantage of these processes is that the direct combustion of the organic contaminants, binders, and / or contaminants, or the post-combustion of the treatment vapors, produces large quantities of flue gases.The additional process steps for flue gas treatment, such as dedusting, denitrification, and desulfurization, require additional equipment and associated investment costs. The energy and consumables required for these processes also represent additional cost factors. The high treatment temperatures are another fundamental disadvantage of thermal-oxidative cleaning or decontamination. Section 6, Sentence 1 of the 17th Federal Immission Control Ordinance (BImSchV) stipulates that the combustion gases produced during the incineration of waste or materials must reach a minimum temperature of 850 °C after the last combustion air supply. These high temperatures can cause cracks in mineral solids and solid mixtures, which impairs their mechanical properties and makes them unusable for road construction.The reason for this is the volume expansion of quartz rock when temperatures exceed 573 °C, which is due to a change in the crystal structure and is generally referred to as quartz cracking. Quartz is present in varying proportions in a wide variety of common rock types. Therefore, excessive heating due to quartz cracking can also damage almost all mineral solids and solid mixtures. The associated loss of quality makes their return to the commercial cycle difficult. The aforementioned patent DE102009025361B4 is characterized in this context by limiting the treatment temperatures of pitch-containing road demolition material to a temperature that must not exceed 600 °C.The disadvantage, however, is that during combustion, exceeding a maximum temperature, in this case 600 °C, can only be prevented if the oxidation process is stopped, i.e., the supply of oxidizing air is interrupted. Interrupting the oxidation process, in turn, leads to an extended residence time of the material being processed in the rotary kiln, which in turn impacts the economic viability of the process. The additional mandatory post-combustion stage brings with it the disadvantages already mentioned.

[0005] In the cold mix, warm mix, or hot mix processes known from the market, reclaimed asphalt is mixed with fresh binder and fresh aggregate, and the mixture is reused as road construction material. The old binder is not removed. This type of asphalt recycling is not permitted in Germany for road demolition material containing tar-containing binder. Therefore, this type of recycling process can only be used for bituminous road demolition material. A disadvantage, however, is the remaining aged bituminous binder on the surface of the solids. The aged bitumen does not mix optimally with the fresh bitumen, so an excessive proportion of recycled asphalt leads to poor quality new asphalt.

[0006] EP254602A1 and WO2008110486A1 describe processes in which molten salts are used to separate bitumen, solids, and solid mixtures. The disadvantage here is that molten salts are very sensitive to impurities and degrade easily, altering their properties such as their melting point. Furthermore, molten salts are highly corrosive in the presence of water and / or oxygen. Both the use of an additional, rapidly degrading operating medium and the greater necessary design effort in the form of corrosion-resistant materials for the equipment parts in contact with molten salts lead to higher operating and investment costs, thus reducing the economic viability of the process.

[0007] US4881475A describes a process for cleaning contaminated soils. For this purpose, the contaminated soils are pyrolyzed in a rotating furnace, and the pyrolysis products are subsequently combusted. One advantage of using pyrolysis to remove organic impurities and contaminants is the avoidance of flue gases, which necessitate complex treatment. A disadvantage of this process is that pyrolysis takes place at atmospheric pressure. Therefore, very high treatment temperatures are necessary to completely remove very high-boiling hydrocarbons, which pose a risk of damage to the minerals due to quartz cracking. This also requires longer residence times, which reduce the economic viability of the process.

[0008] DE102012103881A1 describes a process for extracting hydrocarbons from oil shale. In a first process step, the oil shale is dried with superheated steam at a temperature between 20 °C and 300 °C and at reduced absolute pressure. In a second process step, the pre-dried oil shale is further heated in a reactor to completely or partially volatilize and / or pyrolyze the organic substances it contains. A disadvantage of this process is that the second process step is not also carried out at reduced absolute pressure. At reduced absolute pressure, the pyrolysis of the organic substances would proceed more quickly, and the overall process would be more economical due to the shorter residence times.

[0009] DE2645199C2 describes a process for separating hydrocarbons from hydrocarbon-containing substances by distillation at reduced pressure and elevated temperature through selective liquefaction of the released vapors and separate removal of the liquids. US525397 describes a process for separating chemical contaminants such as volatile and semi-volatile organic chemicals, as well as polychlorinated biphenyls, from inert materials such as soils and sludges. In this process, contaminated feed materials are exposed to a negative pressure between 66.6 mbar and 533 mbar, simultaneously heated, and the resulting vapors are continuously removed. DE4210926A1 describes a carbonization plant for the remediation of organotoxic soil, particularly oil-contaminated or tar-contaminated soil, by carbonization at 400 °C to 650 °C in a carbonization reactor, cooling, and re-disposal of the cleaned soil.The three processes mentioned above have the advantage that, by treating the starting materials at elevated temperatures and under negative pressure or vacuum conditions, shorter treatment times and / or lower treatment temperatures are required, which also has a positive impact on the economic viability of the processes. A disadvantage is that the residence times required for complete and guaranteed cleaning and / or decontamination of the mineral solids still make economic operation impractical.

[0010] DE4232353C2 describes a process for the accelerated thermal decomposition of synthetic, organic waste. The process operates at temperatures between 200°C and 600°C, at a pressure of 10 mbar to 450 bar, and with residence times of 1 minute to 24 hours. The thermal decomposition is carried out in the presence of 0.1 vol.% to 10 vol.% oxygen. The gases generated during the thermal treatment are removed from the reaction mixture by applying a vacuum and / or introducing inert gases. Similar processes are also commercially available for cleaning metal parts used in plastic injection molding. A disadvantage of the described processes is that they are limited to oxygen as the reactive gas and do not consider other process gases and vapors that have a beneficial effect on the thermal decomposition of synthetic, organic waste or on the overall process.In addition, the processes are limited to synthetic, organic substances and do not take into account other possible applications, such as the cleaning and decontamination of mineral solids and solid mixtures from natural hydrocarbons or inorganic individual substances or mixtures of substances.

[0011] A process for the gasification of organic substances and mixtures under negative pressure conditions is described in DE102008032957A1. The process takes place at temperatures ranging from 1200 °C to 1450 °C, at pressures ranging from 0.86 bar to 0.90 bar, and with the addition of an oxygen-steam mixture. The disadvantage of this process is the high treatment temperatures, which, on the one hand, would damage mineral solids or solid mixtures and thus impair their return to the economic cycle, and, on the other hand, would require particularly temperature-resistant materials, leading to high investment costs.

[0012] EP896838B1 describes a device for cleaning contaminated materials of bulk and / or pasty consistency. The device consists of at least one batch-loadable drying chamber and at least one separate batch-loadable decontamination chamber connected to a vacuum source. A mixing mechanism in the form of a paddle mixer is provided for both chambers, and each chamber is connected to its own condenser unit. A disadvantage of this process is that drying and decontamination are carried out in two separate chambers. This measure doubles the equipment required and thus also the investment costs.

[0013] WO2005113721A1 describes a method for removing coke deposits and caking on the internal surfaces of steam cracking plants by introducing a mixture of air and steam. A disadvantage of this method is that it operates at overpressure. If the method were used to treat solids and solid mixtures, the increased pressure would suppress the volatilization of organic impurities and / or contaminants, thus delaying cleaning or decontamination, which in turn would impair economic efficiency due to extended treatment times. The same is considered a disadvantage in EP1194498B1, which describes a method for deasphalting residues by recycling high-boiling materials.

[0014] DE 10 2008 006 719 A1 discloses a method and device for cleaning contaminated materials. In this method, at least one drying chamber and one decontamination chamber interact in a closed system in batch operation. Measures are taken to minimize susceptibility to flow and increase overall safety. Furthermore, process steps are integrated into the material treatment process to increase the cleaning quality.

[0015] DE 197 29 691 C1 discloses a method and device for the complete remediation of contaminated, impregnated wood in uncrushed form or the dry processing of fresh wood, with simultaneous complete, residue-free degradation of dissolved, expelled contaminants. For this purpose, contaminated, impregnated wood or fresh wood is heated in sealed containers, subsequently subjected to a vacuum, and the expelled substances are condensed and introduced into the process flow of a photocatalytic treatment plant.

[0016] CN 207254916 U discloses a device for automatically cleaning contaminated soil. The device includes an air supply, a soil processing device for contaminated soil, and an exhaust gas purification device. The device is said to have the advantages of high efficiency and low cost.

[0017] Based on the prior art, the invention is therefore based on the object of cleaning organic and / or inorganic, low-boiling, high-boiling and very high-boiling individual substances or mixtures of substances economically and effectively, ie reliably, as completely as possible and with a high degree of safety, from mineral solids and solid mixtures, or of removing and / or decontaminating them.

[0018] The object is achieved according to the invention by a method according to claim 1, a method according to claim 9, a device according to claim 10 and a use according to claim 15. Advantageous developments of the invention can be found in the subclaims.

[0019] According to the invention, a process for the purification of mineral solids and mineral solid mixtures is proposed, in which these are treated at a temperature of approximately 60 °C or more and at a reduced pressure and this treatment is carried out in the presence of a process gas and / or a process steam.

[0020] This method, especially in the embodiments described below, can also be used to clean wood materials containing organic pollutants, such as railway sleepers. For simplicity, the method according to the invention is illustrated below for mineral solids and their mixtures, although it should be noted that it can also be carried out analogously for wood materials containing organic pollutants.

[0021] Furthermore, according to the invention, a device is proposed which can be used in particular in this process, which device comprises a reactor with a jacket heater with a plurality of openings and / or nozzles for supplying the process gas and / or the process steam and a vacuum pump.

[0022] The term "cleaning of mineral solids or mineral solid mixtures" means that organic and / or inorganic, low-boiling, high-boiling and very high-boiling individual substances or mixtures of substances are removed from them or they are decontaminated from them.

[0023] The method and device according to the invention solve this problem and improve the disadvantages of the prior art by processing mineral solids and solid mixtures under reduced pressure, at elevated temperatures, and with the addition of process gases and / or process vapors. The volatilization of organic and / or inorganic, low-boiling, high-boiling, and very high-boiling individual substances or mixtures at elevated temperatures is supported by negative relative pressures. As the pressure decreases, the boiling points of the individual substances also generally decrease, causing them to transition into the vapor phase at a lower temperature.The addition of process gases and / or process vapors, in addition to the thermal decomposition of the organic and / or inorganic, low-boiling, high-boiling, and very high-boiling individual substances or mixtures of substances, which is caused by the elevated temperatures, also causes additional decomposition or cracking of the already vaporous or not yet volatilized individual substances. It should be noted that cracking can only occur with organic substances. The terms "process gas" and "process vapor" therefore refer to gases and vapors with which these effects can be achieved. High-molecular-weight compounds in particular are converted into low-molecular-weight substances through reforming with, for example, steam or oxidation with oxidizing agents such as (atmospheric) oxygen or hydrogen peroxide. These low-molecular-weight substances, in turn, have a lower boiling point and are therefore more easily volatilized.Experiments with tar-containing road rubble have led to the completely unexpected result that the addition of steam, for example, achieves very effective removal of the organic binder and improved decontamination of polycyclic aromatic hydrocarbons. The introduction of process gases or vapors can be used specifically to improve decontamination and cleaning results.

[0024] In some embodiments, the amount of process gas and / or the amount of process steam may be about 0.01 to about 50% of the mass of the material to be treated, for example about 0.1 to about 25%, e.g. about 0.01 to about 5%.

[0025] Various processes are already known from the prior art in which, by selecting or adjusting the process parameters of temperature, pressure, and residence time, a gentle and assured cleaning and / or decontamination of solids and solid mixtures is possible. Compared to the prior art, the process according to the invention is characterized by an additional treatment of the solids and solid mixtures with process gases, such as air, oxygen, ozone, carbon monoxide, inert gases such as nitrogen, and mixtures thereof, and / or process vapors such as water vapor, vaporous hydrogen peroxide, vaporous ammonia, vaporous acids and alkalis, and mixtures thereof, during the vacuum pyrolysis process. An additional cleaning or decontamination effect is achieved through a pulsed and / or continuous addition of process gases and / or process vapors. Several advantages are achieved according to the invention: (1) Under otherwise identical pressure and temperature conditions and residence times, the solids or solid mixtures are cleaned and / or decontaminated more effectively. (2) Under otherwise identical pressure and temperature conditions, the same cleaning or decontamination result can be achieved with shorter residence times. (3) Under otherwise identical temperature conditions and residence times, the same cleaning or decontamination result can be achieved at higher absolute pressures. (4) Under otherwise identical pressure conditions and residence times, the same cleaning or decontamination result can be achieved at lower temperatures.

[0026] The latter point is particularly advantageous in the thermo-chemical processing of solids and solid mixtures, where exceeding a certain temperature would lead to damage to the solids and solid mixtures and thus complicate their return to the economic cycle (example: treatment of tar-containing road demolition waste; keyword "quartz crack").

[0027] One or a combination of several of the aforementioned advantages leads to an overall increased economic efficiency of the process according to the invention compared to the processes known from the prior art. Furthermore, the pulsed and / or continuous addition of the process gas and / or process steam also reduces the deposition of coke residues on the surfaces of the solids and solid mixtures that is otherwise common in pyrolysis.

[0028] The method and device according to the invention offer a further advantage in the processing of reclaimed asphalt: By removing the binding agent from the mineral solids and solid mixtures, the quality of the mineral solids required for road construction can be significantly increased, provided the recycled content in new asphalt is maintained. The recycled content is limited in conventional cold, warm, and hot mixing processes because aged bitumen does not mix optimally with the fresh bitumen, which is why an excessive proportion of recycled asphalt leads to poor quality in the new asphalt.

[0029] In the process according to the invention for the thermo-chemical processing of mineral solids or solid mixtures, organic and / or inorganic, low-boiling, high-boiling and / or very high-boiling individual substances and / or mixtures of substances are volatilized and the mineral solids or solid mixtures are thus cleaned and / or decontaminated.

[0030] In the process according to the invention, the solids or solid mixtures to be processed can be introduced into the reactor, e.g., a pyrolysis reactor, in coarsely crushed form, for example, with a grain size of approximately 500 mm or less, e.g., approximately 200 mm or less, or e.g., approximately 100 mm or less. The grain size can be determined by conventional sieving.

[0031] The process according to the invention can be carried out continuously, semi-continuously and in batch mode.

[0032] In some embodiments, there may be no oxygen or only substoichiometric amounts of oxygen in the reactor.

[0033] In some embodiments, the mineral solid may be selected from road demolition material, particularly tar-containing road demolition material, and contaminated soils.

[0034] The process according to the invention is carried out at a temperature of about 60°C or more, for example about 60°C to about 1200°C, e.g. about 250°C to about 600°C, e.g. about 250°C up to the temperature at which a loss of quality of the solids is to be expected. In some embodiments, the process can be carried out at a temperature of about 250°C to about 600°C. If the return of the mineral solids or solid mixtures to the economic cycle without loss of quality is intended, the processing can particularly preferably take place between about 250°C and the temperature at which a change in the physico-chemical properties of the mineral solids and solid mixtures and the associated loss of quality is to be expected (e.g. "quartz jump" at about 573°C), or at a maximum of about 20°C above this temperature.

[0035] The heating of the mineral solids can be done directly or indirectly.

[0036] In some embodiments, the process according to the invention can be carried out at a reduced pressure, ie at a pressure which is lower than normal pressure, ie at absolute pressures, for example, between about 0.01 mbar and about 1013 mbar or about 40 mbar to about 800 mbar or about 50 mbar to about 500 mbar, or in other words at negative relative pressures.

[0037] In the process according to the invention, evacuation and heating of the reactor interior can take place simultaneously or sequentially.

[0038] The residence time of the mineral solids or solid mixtures to be treated in the reactor is between approximately 0.5 seconds and approximately 24 hours, or approximately 0.5 seconds to approximately 3 hours, or approximately 0.5 seconds to approximately 20 minutes, for example, between approximately 0.5 seconds and a residence time at which the content of impurities and / or contamination falls below a specified tolerable value. The residence time is understood to be the time the solid to be treated remains in the reactor. This typically corresponds to the time during which the process according to the invention is carried out in the reactor, i.e., the solid is treated with the process gas and / or process steam at the specified temperature and negative pressure.

[0039] During the thermo-chemical processing of the mineral solids and solid mixtures in the negative pressure range, process gases such as, but not limited to, air, oxygen, ozone, carbon monoxide, etc., and / or inert gases such as, but not limited to, carbon dioxide, nitrogen, etc., as well as mixtures thereof, and / or process vapors such as, but not limited to, water vapor, vaporous hydrogen peroxide, vaporous ammonia, vaporous acids or alkalis, as well as mixtures thereof, are introduced into the reactor interior.

[0040] Product gases and product vapors can be expelled from the mineral solids or solid mixtures and removed from the reaction chamber by the applied negative pressure and / or by purging with an inert gas, such as nitrogen, CO 2 , noble gases, etc., or by purging with process gases and / or process vapors.

[0041] Furthermore, in a preferred embodiment, the reactor can first be purged with an inert gas and heated before the process gas and / or the process steam are introduced.

[0042] The material in the reactor interior can be moved, for example by moving the reactor and / or with the help of stirring or mixing devices.

[0043] Pyrolysis vapors can be fully or partially condensed in a condenser unit and separated from the product gases, thereby obtaining a condensate.

[0044] The condensate can be collected in a container.

[0045] The collected condensate can be recycled or disposed of in a material and / or thermal manner.

[0046] The condensation energy released during the condensation of the vapors and / or the sensible energy of the product vapors and product gases can be used to dry the mineral solids and solid mixtures to be processed, to generate the process vapors and / or other types of thermal integration known to those skilled in the art.

[0047] The product gases can be thermally recycled, used as process gas or inert gas for purging the reactor, collected and / or disposed of.

[0048] In some embodiments, the treatment with the process gas and / or the process steam may be carried out in the presence of a catalytically active material (catalyst) for cleavage and cracking reactions.

[0049] As already mentioned above, the present invention further relates to a device, in particular for carrying out the method according to the invention, wherein the device according to the invention comprises a reactor with a jacket heater with a plurality of openings and / or nozzles for supplying the process gas and / or the process steam and a vacuum pump (10).

[0050] In some embodiments, the reactor may be rotatably mounted. For example, the reactor may be a rotary kiln.

[0051] In some embodiments, the rotatably mounted reactor may have at least one driver in the interior for moving the mineral solid or solid mixture.

[0052] In some embodiments, a wall of the reactor and / or a driver may be formed at least partially from catalytically active material (catalyst) for fission and cracking reactions, or an inner surface of the reactor and / or a surface of the driver may be at least partially coated with such a catalytically active material.

[0053] In some embodiments, the orifice and / or nozzle may be located in a portion of the jacket heater that contacts the mineral solid or mixture once per revolution during cleaning.

[0054] In some embodiments, the device according to the invention may further comprise a condenser unit for condensing product gases and / or product vapors. The condenser unit may, for example, be a shell-and-tube heat exchanger. A collecting tank for the condensates may be attached to the condenser unit.

[0055] The reactor, all connecting lines and other units can be sealed from the environment, i.e. there is no or negligible mass transfer between the interior of the reactor and the environment.

[0056] The method of introducing the process gases and / or vapors into the reactor interior can be designed to ensure intensive contact between the process gases and / or vapors and the mineral solids or solid mixtures to be treated. Additional internals or stirring / mixing devices can be used to further intensify the contact between the mineral solids or solid mixtures and the process gases and / or vapors.

[0057] The effects of the method according to the invention are described below.

[0058] The heating of mineral solids or solid mixtures containing organic impurities and / or contaminants to the temperatures specified above of approximately 60 °C to, for example, approximately 1200 °C in the absence of oxygen initially causes evaporation of water and low-boiling organic substances, and with increasing temperature also evaporation of higher-boiling organic substances and increasingly also thermal decomposition or decomposition of the organic substances.

[0059] The negative relative pressures during processing lower the boiling points, so that water and organic and / or inorganic substances enter the vapor phase at lower temperatures. The negative relative pressures have no effect on the mineral solids or solid mixtures. In particular, the temperature at which the quartz transition occurs is not affected by negative pressure conditions.

[0060] The addition of process gases such as air or O2 and / or process vapors such as steam during the thermo-chemical processing of mineral solids or solid mixtures achieves additional, positive volatilization effects. The organic substances are further broken down and reduced in size not only due to the elevated temperatures, but also through reactions with process gases and / or process vapors. As a rule, the boiling point of the organic substances decreases with the molecular weight, so that even at moderate temperatures, very high-boiling organic impurities and contaminants can be volatilized by treatment with process gases and process vapors and thus removed from the mineral solids and solid mixtures.In addition, solid, carbonaceous residues from pyrolysis, namely pyrolysis coke, can be removed from the surface of the mineral solids and solid mixtures or at least reduced by reaction with process gases and vapors. The addition of steam also lowers the partial pressure of the organic and / or inorganic low-boiling, high-boiling, and very high-boiling individual substances and / or mixtures in the reaction chamber, leading to improved evaporation or volatilization of these substances.

[0061] The addition of process gases and vapors increases the economic efficiency of the process and enables the reliable removal of organic impurities and contaminants. Due to the additional positive decomposition and volatilization effects created by the added process gases and vapors, the process parameters temperature, pressure, and / or residence time can be selected more economically. This allows the temperature to be lowered, resulting in energy savings.

[0062] The same applies to higher absolute pressure. Shorter residence times for the material being processed allow more material to be processed in the same amount of time. If none of the three process parameters are changed, the addition of process gases and vapors will result in improved cleaning and decontamination results, ensuring that impurities and contaminants are removed to a desired or specified level. Altering two or more of the above-mentioned parameters is also conceivable for increased efficiency and assured cleaning and / or decontamination.

[0063] The removal of the resulting product gases and vapors from the reactor enables the separation of the gas / vapor mixture outside the reactor and prevents recondensation and the associated recontamination of the mineral solids and solid mixtures during their cooling.

[0064] The movement of the material in the reactor interior ensures that the heat is distributed more evenly in the bed of mineral solids and solid mixtures, that unreacted material is transported to the reaction surface where the transition to the vapor phase takes place more easily and that the contact with the process gases and process vapors is intensified.

[0065] By condensing the pyrolysis vapors in a condenser unit, they are separated from the product gases. This allows both product gases and product liquids to be further utilized separately and optimally.

[0066] The thermal integration of sensible or latent heat improves the efficiency of the process and thus also its economic viability.

[0067] Thermal utilization of product gases can save primary energy sources, and their use as process gas or inert gas can save operating resources. Both measures lead to cost reductions and thus improved economic efficiency.

[0068] The process and device for the thermo-chemical processing of mineral solids were developed and can be used for the removal of organic and / or inorganic, low-boiling, high-boiling, and very high-boiling individual substances or mixtures of substances from mineral solids or solid mixtures. An example of a feedstock is pitch- or tar-containing road demolition material. The process separates the tar- or pitch-containing organic binder and the pollutants it contains, such as polycyclic aromatic hydrocarbons (PAHs) and phenols, from the aggregate, thus cleaning and decontaminating the aggregate. The process does not damage the aggregate, thus preventing any loss of quality and allowing the mineral solids to be reused as road construction material or for other applications.

[0069] The process can also be applied to bituminous road demolition material. Although this material is not contaminated with PAHs and therefore does not require decontaminating, the mineral solids are coated with an aged binder. Separation of the aged binder and the associated purification of the mineral solids may be desirable in some cases.

[0070] The process according to the invention can also be applied to other impurities and contaminants besides road binders. Using this process, all hydrocarbons can be removed from mineral solids. As long as individual substances or mixtures of substances are volatilizable, i.e., if they can be converted into the vapor or gas phase under certain process conditions, it is possible to separate them from solids or solid mixtures using this process. Depending on the boiling points of the respective substances, this also applies to individual inorganic substances or mixtures of substances.

[0071] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0072] Fig. 1 an inventive device for decontamination of mineral solids.

[0073] The method according to the invention is described below by way of example with reference to the device according to the invention according to Fig. 1 described.

[0074] In one possible process implementation, tar-containing road rubble is thermo-chemically processed in batch mode using steam and oxygen. A possible reactor and process design is presented based on the Fig. 1 explained.

[0075] Reactor 1 is a drum reactor equipped on one side with a loading and unloading opening 2 for filling and unloading solids or solid mixtures. Since pyrolysis is carried out in reactor 1, it can also be referred to as a pyrolysis reactor. The loading and unloading opening 2 can be cleaned and closed easily, quickly, and safely using a cleaning and sealing device.

[0076] The reactor 1 can be tilted upwards or downwards for filling and emptying. The possible tilting movement is shown in Fig. 1represented by arrows 3. During treatment, the reactor 1 can be set into a rotational movement around its axis, represented by an arrow 4. On the inside of the reactor, impellers 5 are provided, which, together with the rotational movement, ensure movement and mixing of the tar-containing road rubble. In addition, the inside of the reactor and the impellers are coated with catalytically active material for steam reforming. Several openings and / or nozzles 6 are provided on the reactor shell for the addition of the process gases and process vapors. The openings and / or nozzles 6 are not evenly distributed over the entire shell, but are only present in a section of the shell that, during operation, comes into contact with the tar-containing road rubble once during each rotation. Supply lines for steam and oxygen are connected to the openings or nozzles and rotate with the reactor 1.The feed line 7 is fed via a rotary tube feedthrough 8, which is located outside the reactor 1 on the side opposite the loading and unloading opening 2. Because the pipes are not located on the same side as the loading and unloading opening 2, the gas and vapor supply lines do not need to be removed after each batch. An exhaust line 9 for product gases and vapors is provided at the loading and unloading opening 2.

[0077] In the exemplary embodiment, the reactor 1 is initially in a position with the loading and unloading opening 2 facing upwards. The reactor 1 is filled with coarsely pre-shredded, tar-containing road rubble up to approximately one-third of the reactor volume via the loading and unloading opening 2. The grain size can be approximately 500 mm or less, e.g., approximately 200 mm or less, or approximately 100 mm or less. The loading and unloading opening 2 is cleaned with the cleaning device and then sealed gas-tight with the closure device.

[0078] The filled reactor is rotated at a low speed, for example at about 0.5 to about 10 revolutions per minute (rpm), e.g. about 0.5 to about 5 rpm or e.g. about 0.5 to about 2 rpm 4. At the same time, the reactor and all downstream system components are evacuated to a pressure between about 20 and about 750 mbar using the vacuum pump 10 and the reactor is heated to a temperature of about 350 °C to about 550 °C using a jacket heater 11. Small recesses for the feed lines 7 to the openings or nozzles 6 are provided on the jacket heater 11. Evacuation and heating of the reactor take place quickly, for example in more than about 0 to about 120 minutes, such as more than about 0 to about 30 minutes or more than about 0 to about 5 minutes, in order to achieve economical throughput times. From an internal reactor temperature of approximately 150 °C, steam is added via the openings or nozzles 6 with each revolution.Instead of injecting water into the reactor, moist starting material can be used or the starting material can be moistened beforehand. This is also possible with acids and alkalis. Towards the end of the treatment time, oxygen is added instead of steam. The process steam and process gas are always added when the jacket area, where the openings or nozzles 6 are located, is on the underside of the reactor 1 and thus the solid bed to be treated is directly above them. In this way, the process steam and process gas flow through the bed of mineral solids from bottom to top, ensuring intensive contact between the steam and the tar-containing road rubble and avoiding short-circuit flows.

[0079] Depending on the polycyclic aromatic hydrocarbon (PAH) load, the tar-containing road rubble remains in the reactor until the PAH and phenol content in the mineral solids bed reliably drops to a value below the legally prescribed maximum limit. The product gases and vapors generated during the heating and evacuation phase and the treatment phase are drawn out of the reactor via the opening in the closure flange 9 by the applied negative pressure. In the exemplary embodiment, the addition of steam supports, on the one hand, the decomposition of the organic and / or inorganic, low-boiling, high-boiling, and very high-boiling binder components and, on the other hand, the expulsion and removal of product gases and vapors from the mineral solids and the reactor by reducing the partial pressure of the hydrocarbon compounds and by the resulting flushing flow.

[0080] The product gases and vapors pass through reactor 1 into a condenser unit 12. In the exemplary embodiment, the condensation unit 12 is a shell-and-tube heat exchanger through whose shell space the product gases and vapors flow and are condensed. Water flows through the tubes of the shell-and-tube heat exchanger as the cooling medium. This water is heated by the latent and sensible energy of the product gases and vapors and is used as feedwater for the process steam generator 13. Preheating the feedwater increases the overall efficiency of the plant.

[0081] Alternatively, condensation can advantageously take place in the tube bundle and not in the shell space of the heat exchanger.

[0082] A vacuum-tight condensate collection tank 14 is attached to the underside of the shell-and-tube heat exchanger and can be separated from the shell-and-tube heat exchanger by a valve 15. A second valve 16 vents the vacuum-tight condensate collection tank 14, allowing it to be easily and safely removed from the condenser unit 12 and replaced. The condensate collected in the collection tank 14 can be handed over to a specialist disposal company.

[0083] Between the condenser unit 12 and the vacuum pump 10 is a unit for separating dust, uncondensed vapors, and pollutants 17. The separation of solids and vapors protects the pump and prevents vapors from condensing in the exhaust line of the vacuum pump 10 and causing malfunctions. The vacuum pump 10 generates the negative pressure, which, on the one hand, leads to accelerated volatilization of the tar constituents and / or fission products and, on the other hand, draws the product gases and vapors from the reactor. The product gas leaving the vacuum pump 10 is fed to a furnace, and the resulting heat is used for steam generation 13 or pre-drying the tar-containing road rubble.

[0084] After the thermo-chemical treatment is complete, reactor 1 is disconnected from the rotary kiln feedthroughs 8, 18. The loading and unloading opening 2 is opened, and reactor 1 is tilted so that it faces downward. As reactor 1 continues to rotate, its contents are emptied while still warm onto a conveyor, which transports the material either directly to an asphalt mixing plant or to a storage area. Once reactor 1 is completely emptied, it is tilted back so that the loading and unloading opening 2 faces upward, allowing it to be refilled.

[0085] The invention is further explained by means of the following experiments, the test conditions and results being shown in Table 1. Table 1: Material Tar-containing road demolition Solid after treatment Solid after treatment Solid after treatment Added gas / steam - - N2 H2O O2 Process temperature °C - 450 450 450 Process pressure mbar (abs) - 50 50 50 Residence time at process temperature min - 0 0 0 Naphthalene mg / kg TS 0,1 0,10 0, 10 0,10 Acenaphthylen 0,1 0,10 0, 10 0,10 Acenapthene 58,1 0,80 0,58 0,14 Fluoren 44,9 2,65 0,51 0,14 Phenanthren 238 12,89 3, 91 3,25 Anthracene 81,5 3,03 0,95 0,34 Fluoranthen 448 26,59 7, 48 11,54 Pyren 226 21,76 5, 62 8,25 Benzo(a)anthracene 189 14,67 5,02 7,19 Chrysanthemums 148 14,71 4,35 7,48 Benzo(b)fluoranthen 105 17,21 6,59 2,14 Benzo(k)fluoranthen 78,8 5,97 2, 48 0,78 Benzo(a)pyren 111 17,33 6,07 1,41 Dibenzo(a,h)anthracene 70,8 1,15 1,18 0,38 Benzo(g,h,i)perylen 81,8 7,91 4,46 1,12 Indeno(1,2,3-c,d)pyren 55,6 10,61 4,94 1,15 Total PAH mg / kg TS 1936,7 157, 49 54,35 45,50 Phenol index mg / L 0,021 0,036 0,019 0,0073

[0086] In pilot-scale experiments, tar-containing road rubble with a PAH load of 1,936.7 mg / kg dry matter was treated at a temperature of 450 °C and an absolute pressure of 50 mbar. The residence time in the reactor after evacuation and heating to the process temperature of 450 °C was 0 min. Starting at a process temperature of 150 °C, the specified gases or vapors were intermittently injected into the reactor.

[0087] Treatment with H 2 O vapor and with O 2 provided significantly better cleaning results than the addition of N 2 , under otherwise identical conditions.

[0088] Of course, the invention is not limited to the embodiments illustrated in the figures. The above description is therefore not to be considered restrictive, but rather explanatory. The following claims are to be understood as meaning that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. If the description or the claims define 'first' and 'second' features, this serves to distinguish similar features without establishing a priority.

Claims

1. Method for purifying mineral solids and mixtures of mineral solids, which are treated in a reactor at a temperature of about 60°C or more and at a negative pressure, the treatment being carried out in the presence of a process gas and / or a process steam, characterized in that the reactor is first rinsed with an inert gas and heated and then the process gas and / or the process steam is introduced.

2. Method according to claim 1, characterized in that the mineral solid is selected from broken-up road material and polluted soils.

3. Method according to claim 1 or 2, characterized in that the temperature is about 60°C to about 1200°C or about 250°C to about 600°C or about 250°C up to the temperature at which a quality loss of the solid or mixture of solids has to be expected.

4. Method according to any one of the preceding claims, characterized in that the negative pressure is about 0.01 mbar to about 1013 mbar or about 40 mbar to about 800 mbar or about 50 mbar to about 500 mbar.

5. Method according to any one of the preceding claims, characterized in that the treatment of the mineral solid and the mixture of mineral solids is carried out for about 0.5 seconds to about 24 hours or for about 0.5 seconds to about 3 hours or for about 0.5 seconds to about 20 minutes.

6. Method according to any one of the preceding claims, characterized in that the process gas is selected from air, oxygen, ozone, carbon monoxide and the mixtures thereof and / or in that the process steam is selected from water vapor, vaporous hydrogen peroxide, vaporous ammonia, vaporous acids, vaporous basic solutions and the mixtures thereof.

7. Method according to any one of the preceding claims, characterized in that generated pyrolysis vapors are at least partially condensed and separated by means of a condenser unit (12) so as to obtain a condensate.

8. Method according to any one of the preceding claims, characterized in that the treatment with the process gas and / or the process steam takes place in the presence of a catalytically active material.

9. Method for purifying wood material with organic pollutants, such as railroad ties, which are treated in a reactor at a temperature of about 60°C or more and at a negative pressure, the treatment being carried out in the presence of a process gas and / or a process steam, characterized in that the reactor is first rinsed with an inert gas and heated and then the process gas and / or the process steam is introduced.

10. Device for purifying wood material with organic pollutants, such as railroad ties, mineral solids and mixtures of mineral solids by the method according to any one of claims 1 to 9, the device comprising a reactor (1) with a jacket heating (11) having a plurality of openings and / or nozzles (6) for supplying a process gas and / or a process steam and a vacuum pump (10), characterized in that a wall of the reactor (1) and / or at least one driver (5) is formed from a catalytically active material for decomposition and cracking reactions or an inner surface of the reactor (1) and / or a surface of the drivers (5) is at least partially coated with a catalytically active material for decomposition and cracking reactions.

11. Device according to claim 10, characterized in that the reactor (1) is rotatably mounted, or in that the reactor (1) is a rotary kiln.

12. Device according to claim 11, characterized in that the interior of the rotatably mounted reactor (1) has at least one driver (5) for moving the mineral solid or mixture of solids.

13. Device according to any one of claims 10 to 12, characterized in that the openings and / or nozzles (6) are present in a section of the jacket heating (11), which during the purification comes into contact with the mineral solid or mixture of mineral solids once per each revolution.

14. Device according to any one of claims 10 to 13, characterized in that the device further includes a condenser unit (12), by means of which product gases and / or product vapors are condensed, in particular the condenser unit (12) being a shell-and-tube heat exchanger.

15. Use of the device according to any one of claims 10 to 14 for purifying mineral solids, for example broken-up road materials or polluted soils, or wood material with organic pollutants, such as railroad ties.