Method for the continuous purification of process water in the treatment of waste paper with a controlled content of inorganic solid materials

Abstract

The invention relates to a method and a device for continuously purifying process water which is circulated in a device for treating waste paper. The process water is fed from a unit of the device to an anaerobic reactor including a gas separator, and the purified process water is fed back to the unit of the device, wherein the unit is selected from the group consisting of a material dissolver, a sorting device, a dewatering device, an oxidation / reduction unit, a centrifugal sorter, a fine sorting device, a paper machine-forming section, a paper machine-pressing section, a waste treatment unit, a fiber recovery unit and a drying section, wherein the content of inorganic solid materials in the reactor is measured, and if this content exceeds a preset limit value, the process water is continuously fed from the reactor to a solid / liquid separation device for separation into a part poor in inorganic solid materials and a part rich in inorganic solid materials, wherein the part poor in inorganic solid materials is fed back to the anaerobic reactor and the part rich in inorganic solid materials is discharged from the device until the content of inorganic solid materials in the process water is less than the limit value.

Description

Technical Field

[0001] The invention relates to a method for the continuous purification of process water, which is circulated in a device for treating waste paper of a machine for making paper from waste paper and / or in a paper machine, wherein the process water to be purified is fed from a unit of the device and / or of the paper machine to an anaerobic reactor, the process water in the anaerobic reactor comes into contact with anaerobic microorganisms in order to degrade the impurities contained in the process water, and the purified process water is discharged from the anaerobic reactor and fed back to at least one unit of the device and / or of the paper machine. Background Art

[0002] In many technical fields, it is necessary to treat the process water that is circulated in the equipment to prevent the process water from being enriched with impurities. This also applies in particular to process water in papermaking and, more precisely, in particular to process water in papermaking from waste paper. In the past few decades, paper has been increasingly obtained from waste paper in order to reduce the energy consumption during papermaking and in particular to reduce the consumption of natural resources. In order to produce one ton of virgin fiber paper, about 2 tons of wood are required, while the wood demand during paper recycling may be sharply reduced or reduced to zero depending on the proportion of secondary fibers from waste paper relative to the total fiber amount in the recycled paper. In addition, compared with papermaking from virgin fibers, only half the energy and only one-third of fresh water are required when producing recycled paper. Nevertheless, the quality of recycled paper is as high as that of virgin fiber paper today, for example in terms of ink fastness, printing performance, whiteness and aging resistance.

[0003] When making paper from waste paper, the waste paper is first mixed with water and comminuted in a pulper or material dissolver with stirring and mixing in order to dissolve the individual fiber composites. The fibers are then purified in order to remove non-fibrous foreign matter from the fiber slurry before the fibers are optionally decolorized and finally processed into paper on a paper machine after adding a small portion of virgin fibers, if necessary. Therefore, a corresponding machine for making paper from waste paper comprises: a device for treating waste paper and a paper machine, wherein the waste paper treatment device has a waste paper dissolving unit or a pulper, in which process water is supplied to the waste paper to dissolve and comminute the fibers; a sorting device for removing dirt and a dewatering unit for removing process water. It is also known that two or more waste paper treatment devices or stages, so-called loops, are arranged in the device in order to improve the quality of the fibers processed from the waste paper. Each loop of the waste paper treatment device and the paper machine preferably comprises its own process water treatment unit, wherein the individual process water treatment units can be decoupled from each other by a dewatering device arranged between the individual loops. In order to be able to circulate the process water and thus minimize the addition of fresh water, it must be purified to the required extent.

[0004] In order to purify process water, a variety of mechanical, chemical and biological methods and corresponding reactors are known. When biological process water purification is carried out, the process water to be purified is contacted with aerobic or anaerobic microorganisms, which degrade the organic impurities contained in the process water mainly into carbon dioxide and water when using aerobic microorganisms and mainly into carbon dioxide and methane when using anaerobic microorganisms. Here, biological process water purification methods are increasingly being implemented with anaerobic microorganisms, because when anaerobic process water purification is carried out, on the one hand, oxygen does not have to be introduced into the bioreactor at high energy consumption, and on the other hand, high-energy biogas is produced during purification, which can be used to obtain energy later. According to the type and form of the biomass used, the reactors for anaerobic process water purification are divided into contact pulp reactors, UASB reactors, EGSB reactors, fixed bed reactors and fluidized bed reactors. For fixed bed reactors, microorganisms are attached to fixed carrier materials and for fluidized bed reactors, microorganisms are attached to freely movable small carrier materials, while for UASB and EGSB reactors, microorganisms are used in the form of so-called particles. Such a process and corresponding reactors are described, for example, in EP 0 170 332 A1, in EP 1 071 636 B1 and in EP 0 539 430 B1.

[0005] When anaerobic process water purification is carried out, it is particularly important to ensure that the content of inorganic solid materials and especially the content of lime in the process water contained in the anaerobic reactor is not too high. This is a great challenge in particular when purifying process water in machines for papermaking from waste paper, because waste paper contains a relatively large amount of lime in its coating, which is therefore forcibly converted into process water. It is important to prevent too high a content of inorganic solid materials and especially lime in the process water contained in the anaerobic reactor, because a high content of inorganic solid materials and especially lime can interfere with the operation of the anaerobic reactor, such as especially a UASB reactor. For the function of the microbial granules contained in the anaerobic reactor, it is important that these microbial granules have a defined specific gravity so that the organic compounds from the process water can rise in the reactor during the degradation of the biogas formed here and attached to the microbial granules, so that the biogas formed can be separated on the gas separator. After the separation of the biogas, the specific gravity must not be so great that the microbial granules have fallen to the bottom of the reactor, because otherwise the microbial granules can no longer participate in the purification process. However, due to their structure and size, the microbial granules act as crystallization nuclei for the deposition of inorganic solid materials, in particular lime, so that in the presence of a certain content of inorganic solid materials, in particular lime, inorganic solid materials, in particular lime, are deposited on the microbial granules, wherein these deposits lead to incalculable displacement of the heavy granules, so that these granules can no longer perform their function. The metabolic capacity of the anaerobic microorganisms is also reduced by, in particular, bicarbonate (HCO3 - ) causes a shift in the lime-carbonic acid-equilibrium, which further favors the precipitation of lime on the microbial granules. Despite the precipitation of lime on the microbial granules, in order to ensure the function of the microbial granules, the recirculation volume in the anaerobic reactor must be increased so that the granules are kept suspended in the reactor despite the greater specific gravity. However, the recirculation volume is limited on the one hand by the hydraulic capacity of the separator and on the other hand by the necessity of keeping the fluid in the reactor in a laminar flow state. In addition, a higher recirculation volume causes the escape of carbon dioxide due to the pressure gradient generated on the suction side and the pressure side of the pump in the recirculation line and thus causes a further shift of the lime-carbonic acid-equilibrium in the direction of lime precipitation. Summary of the invention

[0006] The object of the present invention is therefore to provide a method for the continuous purification of process water which is circulated in a device for treating waste paper of a machine for producing paper from waste paper and / or in a papermaking machine while using an anaerobic reactor, as well as a corresponding device for treating waste paper of a machine for producing paper from waste paper and / or a papermaking machine, wherein the process water is effectively purified and wherein interference with the operation of the anaerobic reactor is reliably avoided in a simple manner.

[0007] According to the invention, this object is achieved by a method for the continuous purification of process water, which is circulated in a device for treating waste paper of a machine for making paper from waste paper and / or in a paper machine, wherein the process water to be purified is fed from at least one unit of the device and / or the paper machine to a process water treatment unit having an anaerobic reactor with one or more gas separators, wherein the process water is contacted in the anaerobic reactor with anaerobic microorganisms in order to degrade impurities contained in the process water, and the purified process water is discharged from the anaerobic reactor and fed again to at least one unit of the device and / or the paper machine, wherein the at least one unit is selected from a material dissolver, a sorting device, a dewatering unit, an oxidation / reduction unit, a centrifugal separator, a fine sorting device, a paper machine forming section, a paper machine pressing section, a waste treatment unit The invention relates to a papermaking machine and a papermaking machine comprising: a processing unit, a fiber recovery unit and a drying unit, wherein in the method the content of inorganic solid materials in the process water contained in the anaerobic reactor is measured continuously or discontinuously, and, if the content of inorganic solid materials in the process water contained in the anaerobic reactor exceeds a preset limit value, the process water together with the dissolved and dispersed solid materials therein is continuously conveyed from the anaerobic reactor to a solid / liquid separation device for separation into a part poor in inorganic solid materials and a part rich in inorganic solid materials, wherein the part poor in inorganic solid materials is at least partially fed back into the anaerobic reactor and the part rich in inorganic solid materials is discharged from the device and / or the papermaking machine until the content of inorganic solid materials in the process water contained in the anaerobic reactor is below the preset limit value.

[0008] According to the invention, the content of inorganic solids together with dissolved and dispersed solids in the process water contained in the anaerobic reactor is measured and, if the content of inorganic solids together with dissolved and dispersed solids in the process water contained in the anaerobic reactor exceeds a predefined limit value, the process water together with the dissolved and dispersed solids in the process water is continuously fed from the anaerobic reactor to a solid / liquid separation device for separation into a fraction depleted in inorganic solids and a fraction enriched in inorganic solids, wherein the fraction depleted in inorganic solids is at least partially fed back into the anaerobic reactor and the fraction enriched in inorganic solids is discharged from the device and / or the paper machine until the content of inorganic solids in the process water contained in the anaerobic reactor falls below the predefined limit value, thereby ensuring in a process-technically simple and particularly reliable manner that the operation of the anaerobic reactor is prevented from being disturbed by deposits of solids and in particular lime deposits on anaerobic microorganisms or anaerobic microorganism granules. As a result, a particularly high efficiency of the anaerobic purification is ensured even over very long operating times, without requiring maintenance work, such as manual removal of pulp and solids from the anaerobic reactor, or expensive additional purification stages, such as pressure-release flotation for decalcifying the process water. For these reasons, the method according to the invention allows efficient and reliable continuous purification of process water that is circulated in a device for treating waste paper of a machine for making paper from waste paper and / or in a papermaking machine.

[0009] According to the invention, in the method for purifying process water circulated in an apparatus and / or a paper machine, when the content of inorganic solid materials in the process water contained in the anaerobic reactor exceeds a preset limit value, the process water from the anaerobic reactor is continuously fed to the solid / liquid separation device until the content of inorganic solid materials in the process water contained in the anaerobic reactor is less than the preset limit value. Here, "process water contained in the anaerobic reactor" refers to the mixture contained in the anaerobic reactor, i.e. the process water contained therein, including all dissolved and dispersed substances therein, such as organic compounds, inorganic compounds and microorganisms (particles).

[0010] In principle, the invention is not particularly restricted with regard to the manner in which the content of inorganic solids in the process water contained in the anaerobic reactor is measured. In particular, the content of inorganic solids can be determined as described in DIN 38409-1 "German unit method for the examination of water, wastewater and sludge; general functional and material parameters (group H); determination of total dry residue, filtrate dry residue and annealing residue (H1)" from January 1987 and in DIN 38409-2 "German unit method for the examination of water, wastewater and sludge; general functional and material characteristic parameters (group H); determination of filterable material and annealing residue (H2)" from March 1987.

[0011] A simple and nevertheless reliable measurement of the content of inorganic solids in the process water contained in the anaerobic reactor can preferably be achieved by measuring the content of inorganic solids in the anaerobic reactor by sampling the process water contained in the anaerobic reactor, filtering the sample, drying the residue obtained during the filtration in an oven at 105° C. until no more mass loss occurs in order to obtain a dried solid residue, measuring the mass of the dried solid residue, thermally treating the dried solid residue in an oven at 550° C. until no more mass loss occurs in order to obtain a heat-treated solid residue, and measuring the mass of the heat-treated solid residue, wherein the content of inorganic solids in the process water contained in the anaerobic reactor at the time of sampling is the quotient of the mass of the heat-treated solid residue and the mass of the dried solid residue. The filtration can be carried out in particular with an ashless filter having a pore size of 15 to 30 μm and preferably a pore size of 20 to 25 μm. Suitable filters are, for example, ashless black and white paper tape filters. During drying at 105° C., moisture is removed from the residue obtained during filtration, so that a dry solid material residue containing both organic and inorganic solid materials is obtained. During subsequent heat treatment at 550° C., the organic solid materials contained in the dry solid material residue are decomposed and removed in the form of gas, so that the heat-treated solid material residue consists of inorganic solids and mainly lime.

[0012] The content of inorganic solids in the process water contained in the anaerobic reactor can also be measured continuously by continuously removing a measuring flow of the process water from the anaerobic reactor and filtering it, wherein the filtrate is continuously or automatically guided at predetermined intervals through a continuous oven, such as a continuous oven, in which the filtrate is dried, for example, at 105° C., until no more mass loss occurs, in order to obtain a dried solid residue, from which the mass is measured in a continuous balance arranged downstream of the continuous oven. This dried solid residue is then heat-treated in the continuous oven at 550° C., wherein the length of the continuous oven, i.e., its passage time, is set so that the dried solid residue is heated until no more mass loss occurs, in order to obtain a heat-treated solid residue, the mass of which is then measured in a downstream continuous balance. The content of inorganic solids is then determined by a control device as described above and the method is controlled as a function of the continuously determined values.

[0013] In order to minimize the influence of the sampling of samples on the particularly active microorganisms (particles) which are present during the anaerobic process mainly in the middle reactor region with respect to the height of the anaerobic reactor and which have not settled from the sediment to the reactor bottom, it is provided in a further development of the concept of the invention that a sample of the process water contained in the anaerobic reactor is taken from the lower region of the anaerobic reactor with respect to the height of the anaerobic reactor. The sample is preferably taken from the lower 20%, particularly preferably from the lower 10% and particularly preferably from the lower 5% of the anaerobic reactor or from solid material settled on the reactor bottom.

[0014] Preferably, the microorganisms in the anaerobic reactor are present as microorganism granules.

[0015] For the same reasons, it is preferred according to the invention to remove process water, which is continuously supplied to the solid / liquid separation device when a preset limit value is exceeded, from the lower region of the anaerobic reactor in relation to the height of the anaerobic reactor. In this embodiment, it is also preferred to remove process water from the lower 20%, particularly preferably from the lower 10%, and particularly preferably from the lower 5%, of the anaerobic reactor in relation to the height of the anaerobic reactor.

[0016] In order to allow solid materials dispersed in the process water to settle on the reactor bottom without unnecessary lifting of sediments due to the inflow and the flow conditions set in the anaerobic reactor, according to another preferred embodiment of the invention, the lower region of the anaerobic reactor is at least partially conical in cross section. Due to the slope of the reactor wall of the reactor bottom formed in the lower region, the solid materials are facilitated to sink to the lowest region of the reactor bottom, thereby minimizing the lifting caused by the inflow of process water and the flow conditions in the anaerobic reactor.

[0017] Good results are achieved in particular if the lower region of the anaerobic reactor is designed as a cone, wherein the cone preferably extends over 1 to 50%, particularly preferably 1 to 20% and particularly preferably 1 to 10% of the height of the anaerobic reactor.

[0018] Instead of one cone, a plurality of cones can also be provided in the lower region of the anaerobic reactor. In this alternative embodiment, the lower region of the anaerobic reactor is preferably designed in a zigzag manner when viewed in cross section, wherein the zigzag region preferably extends over 1 to 50%, particularly preferably 1 to 20%, and particularly preferably 1 to 10% of the height of the anaerobic reactor. Thus, in this embodiment, the reactor bottom comprises a plurality of adjacent conical regions, so that the total area of ​​the inclined surface of the reactor wall of the reactor bottom is larger than in the previous embodiment, in which the reactor bottom is designed as a cone.

[0019] Preferably, the limit value for the content of inorganic solid materials in the process water contained in the anaerobic reactor is preset to a value between 30 and 45 weight %, preferably between 34 and 40 weight %, particularly preferably between 36 and 38 weight % and most preferably to approximately 37 weight %.

[0020] According to another particularly preferred embodiment of the invention, it is provided that the process water from the anaerobic reactor is continuously fed to the solid / liquid separation device and the part depleted of inorganic solids is at least partially fed back to the anaerobic reactor until the content of inorganic solids in the process water contained in the anaerobic reactor is at least 1% lower, preferably at least 2% lower, particularly preferably at least 5% lower and most preferably at least 10% lower than a predefined limit value. The feeding of the process water from the anaerobic reactor to the solid / liquid separation device is then terminated until the limit value is exceeded again.

[0021] In an improved solution of the inventive concept, it is proposed that the process water is separated in the solid / liquid separation device in such a way that the portion of the process water lacking in inorganic solid materials is at least 70% by volume, preferably at least 80% by volume and particularly preferably at least 90% by volume, with respect to the volume flow of the process water supplied from the anaerobic reactor to the solid / liquid separation device, and the portion of the portion enriched in inorganic solid materials is the remainder of 100% by volume. This achieves that the maximum portion of the process water lacking in solid materials is or can be directed back into the anaerobic reactor. This is important because the process water is preferably taken from the lower region of the anaerobic reactor as described above and is therefore not yet sufficiently purified with respect to the organic impurities dissolved therein. On the contrary, the process water that has been sufficiently purified is discharged from the upper region of the anaerobic reactor.

[0022] For the reasons stated above, it is also preferred that the process water is separated in the solid / liquid separation device in such a way that the content of inorganic solid materials in the part enriched in inorganic solid materials is at least 25%, preferably at least 50%, particularly preferably at least 75% and at most preferably at least 100% higher than the content of inorganic solid materials in the part poor in inorganic solid materials.

[0023] Good results are particularly obtained if the process water is separated in the solid / liquid separation device in such a way that the content of inorganic solid materials in the part rich in inorganic solid materials is 1.5 to 5.0 kg / l, preferably 2.0 to 3.0 kg / l, particularly preferably 2.3 to 2.7 kg / l and at most preferably about 2.5 kg / l and the content of inorganic solid materials in the part poor in inorganic solid materials is 0.1 to 1.5 kg / l, preferably 0.5 to 1.5 kg / l and particularly preferably 0.5 to 1.0 kg / l.

[0024] The control or regulation of the aforementioned parameters can be carried out manually or preferably automatically. In the case of manual control or regulation, after a preset limit value is exceeded, the process of continuously removing process water from the anaerobic reactor and feeding it to the solid / liquid separation device and returning the portion depleted of inorganic solid materials at least partially to the anaerobic reactor can be manually started, and the process of continuously removing process water from the anaerobic reactor and feeding it to the solid / liquid separation device and returning the portion depleted of inorganic solid materials at least partially to the anaerobic reactor can be manually stopped as soon as a subsequently extracted sample shows a content of inorganic solid materials in the process water contained in the anaerobic reactor that is below a preset limit value. In the case of automatic control or regulation of the aforementioned parameters, the content of inorganic solid materials in the process water contained in the anaerobic reactor, measured on the sample, is preferably transmitted to an electronic control unit, which automatically starts the process of continuously discharging process water from the anaerobic reactor and conveying the process water to a solid / liquid separation device when a preset limit value for the content of inorganic solid materials in the process water contained in the anaerobic reactor is exceeded, and automatically ends the process of continuously discharging process water from the anaerobic reactor and conveying the process water to a solid / liquid separation device when the content of inorganic solid materials in the process water contained in the anaerobic reactor is below a preset threshold value at or below the limit value.

[0025] In order to prevent the introduction of air harmful to anaerobic microorganisms by returning the portion lacking in inorganic solid materials to the anaerobic reactor, it is proposed in an improved solution of the concept of the present invention that the solid / liquid separation device is at least constructed so that the process water supplied from the anaerobic reactor to the solid / liquid separation device and the portion lacking in inorganic solid materials in the solid / liquid separation device do not come into contact with air. In addition, for the above reasons, the pipeline connecting the anaerobic reactor and the solid / liquid separation device for discharging process water from the anaerobic reactor and supplying the process water to the solid / liquid separation device and the return pipeline connecting the solid / liquid separation device and the anaerobic reactor for returning the portion lacking in inorganic solid materials to the anaerobic reactor are preferably constructed in an airtight manner.

[0026] In order to achieve the purpose of effectively separating the process water continuously supplied from the anaerobic reactor to the solid / liquid separation device into a part poor in inorganic solid materials and a part rich in inorganic solid materials, according to another particularly preferred embodiment of the present invention, the separation is carried out in a solid / liquid separation device comprising one or more centrifugal separators.

[0027] Good results are achieved in particular if the process water supplied continuously from the anaerobic reactor to the solid / liquid separation device is separated into a fraction depleted in inorganic solids and a fraction enriched in inorganic solids in the solid / liquid separation device comprising one or more cyclones. In the cyclones, the separation of the two fractions is carried out in that the supplied process water together with the solids dissolved and dispersed therein is set in a rotational motion in the cyclone, due to which the mass-heavy fraction is thrown onto the inner wall of the cyclone due to the centrifugal force, from which it sinks downward in the cyclone and can be discharged there, while the mass-less fraction remains inside the cyclone without contacting the inner wall of the cyclone and can therefore be discharged from the cyclone at the top due to the flow conditions prevailing in the cyclone.

[0028] Furthermore, in another preferred embodiment, it is provided that the lower region of the cyclone has a heavy portion chamber. This heavy portion chamber is connected to the lower outlet of the cyclone separator via a first automatic on / off slide valve A in its upper region. The lower region of this heavy portion chamber has a second automatic on / off slide valve B, which is used to discharge the ash-enriched portion. During operation, the first slide valve A is opened and the second slide valve B is opened, so that the ash-rich portion is enriched in the heavy portion chamber. At specific time intervals, the first slide valve A is closed and the second slide valve B is opened, so that the heavy portion chamber is emptied. A flushing device can also be provided in the heavy portion chamber, which automatically flushes the chamber after emptying before the second slide valve B is closed again and the slide valve A is opened, so as to repeat the cycle. The discontinuous emptying of the chamber helps to reduce the amount of waste.

[0029] The conveying of the process water to the solid / liquid separation device can be carried out by means of a pump. In order to keep the operating costs of the method according to the invention as low as possible, it is particularly preferred according to the invention to arrange the solid / liquid separation device and to adjust the filling height in the anaerobic reactor in such a way that the process water is conveyed to the solid / liquid separation device from the anaerobic reactor at least to a considerable extent and very particularly preferably only by gravity. This can be achieved, for example, in the following way, that the height difference between the liquid level in the anaerobic reactor and the position where the process water is conveyed to the solid / liquid separation device is so great that the difference between the static pressure in the anaerobic reactor and the static pressure in the solid / liquid separation device is sufficiently large. In view of this, it is preferred that the above-mentioned pressure difference is at least 0.2 MPa corresponding to 2 bar and at most preferably at least 0.3 MPa corresponding to 3 bar.

[0030] In a development of the concept according to the invention, it is provided that the part depleted in inorganic solid material is completely fed back into the anaerobic reactor.

[0031] The return of the portion depleted in inorganic solid material into the anaerobic reactor can be achieved in a structurally simple manner by feeding the portion depleted in inorganic solid material into the inlet to the anaerobic reactor. It is therefore preferred that the portion depleted in inorganic solid material is at least partially and very particularly preferably completely returned through the inlet to the anaerobic reactor.

[0032] Due to the efficiency of removing solid materials and in particular lime from the process water in the anaerobic reactor, the method according to the invention is particularly suitable for purifying process water in waste paper production, where, due to the lime contained in the waste paper, a large amount of lime can accumulate in the process water without effective removal of lime. According to the invention, the process water to be purified is fed from at least one unit of the device and / or paper machine to the process water treatment unit and therein to the anaerobic reactor contained in the process water treatment unit, and the process water purified in the anaerobic reactor is discharged from the anaerobic reactor and is fed back from the process water treatment unit to at least one unit of the device and / or paper machine, wherein the at least one unit is selected from one or more units of a material dissolver, a sorting device, a dewatering unit, an oxidation / reduction unit, a centrifugal separator, a fine sorting device, a paper machine-forming section, a paper machine-pressing section, a waste treatment unit, a fiber recovery unit and a drying section. This includes drawing the process water from the unit and feeding it to the process water treatment unit and feeding the purified process water from the process water treatment unit back to the same unit. However, as an alternative, it is also possible to extract the process water from the first unit and feed it to the process water treatment unit, and to return the purified process water from the process water treatment unit to a second unit different from the first unit. For example, the process water can be extracted from a sorting device of the device and directed to the process water treatment unit, and the purified process water from the process water treatment unit can be directed back to the material dissolver. In addition, it is also possible and preferred to discharge process water from multiple units of the device and / or paper machine and feed it to the process water treatment unit, and then to return the purified process water from the process water treatment unit to one unit of the device, preferably a material dissolver or a sorting device or a centrifugal separator of the paper machine. In addition, the process water can also be discharged from two or more different units and fed to the process water treatment unit, and the purified process water from the process water treatment unit can be directed back to two or more different units. According to the invention and therefore also in each of the aforementioned embodiments, at least one and preferably all units from which process water is supplied to the process water supply unit and at least one and preferably all units to which the purified process water in the anaerobic reactor is returned are selected from one or more units of a material dissolver, a sorting device, a dewatering unit, an oxidation / reduction unit, a centrifugal sorter, a fine sorting device, a paper machine-forming section, a paper machine-pressing section, a waste treatment unit, a fiber recovery unit and a drying section.The return of the process water purified in the anaerobic reactor of the process water treatment unit into at least one unit of the device and / or the paper machine can take place directly, i.e. without any further devices between the anaerobic reactor and the unit, or indirectly, by first subjecting the process water purified in the anaerobic reactor to one or more further purification stages, such as, for example, decalcification or filtration.

[0033] Another subject of the invention is a device and / or a paper machine for treating waste paper for a machine for making paper from waste paper, in particular for carrying out the aforementioned method, wherein the device and / or the paper machine comprises a process water treatment unit for purifying process water circulated in the device and / or the paper machine and also comprises at least one of the following units, which are selected from one or more of the following units: a material dissolver, a sorting device, a dewatering unit, an oxidation / reduction unit, a centrifugal sorter, a fine sorting device, a paper machine forming section, a paper machine pressing section, a waste treatment unit, a fiber recovery unit and a drying section, and wherein the process water treatment unit for purifying process water circulated in the device and / or the paper machine comprises:

[0034] i) an anaerobic reactor comprising one or more gas separators, the anaerobic reactor being used for anaerobically purifying process water, the anaerobic reactor having at least one supply line for conveying the process water to be purified into the anaerobic reactor and at least one discharge line for discharging the purified process water from the reactor, wherein the process water treatment unit is connected to at least one of the at least one units so that during operation of the device and / or the paper machine, the process water to be purified is conveyed from the at least one unit to the process water treatment unit and therein to the anaerobic reactor, and the purified process water after the process water treatment step is fed back into the at least one unit, and

[0035] ii) a solid / liquid separation device for separating process water discharged from the anaerobic reactor into a part poor in inorganic solid materials and a part rich in inorganic solid materials, the solid / liquid separation device comprising a discharge line for the part rich in inorganic solid materials and a return line for at least partially returning the part poor in inorganic solid materials to the anaerobic reactor, wherein another line leads from the anaerobic reactor to the solid / liquid separation device for conveying process water discharged from the anaerobic reactor.

[0036] Preferably, the device and / or paper machine according to the invention also includes a control device, which is capable of receiving measured data about the content of inorganic solid materials in the process water contained in the anaerobic reactor and into which limit values ​​and optional threshold values ​​can be input, wherein the control device is designed so that it automatically starts the process of continuously discharging process water from the anaerobic reactor and conveying the process water to the solid / liquid separation device when a preset limit value for the content of inorganic solid materials in the process water contained in the anaerobic reactor is exceeded, and automatically ends the process of continuously discharging process water from the anaerobic reactor and conveying the process water to the solid / liquid separation device when the limit value or the input threshold value for the content of inorganic solid materials in the process water contained in the anaerobic reactor is fallen below.

[0037] In an improved solution of the present invention, it is proposed that the device and / or paper machine further comprises iii) a measuring mechanism for measuring the content of inorganic solid materials in the process water contained in the anaerobic reactor. The measuring mechanism can include an oven and a balance so that the measuring method described above can be implemented. In particular, the oven can be a continuous oven, such as a continuous oven, and the balance can be a continuous balance. A continuous balance measures the mass flow, that is, the weighing process is not carried out point by point but permanently within the range of a predetermined measuring section. An example of a continuous balance is a Coriolis flow meter. As an alternative, the measuring mechanism can also include a combination of a mechanism for continuously measuring the total solid material content of the process water contained in the anaerobic reactor and a mechanism for continuously measuring the content of organic solid materials in the process water contained in the anaerobic reactor, wherein the difference between the total solid material content and the content of organic solid materials determined thereby corresponds to the content of inorganic solid materials. The means for continuously measuring the content of organic solid materials can include, for example, a near infrared (NIR) spectrometer, wherein the means for continuously measuring the content of total solid materials is a dispersion density meter, a transmission meter, or the like.

[0038] Good results are particularly achieved if the pipeline leading from the anaerobic reactor to the solid / liquid separation device opens into the anaerobic reactor in the lower region relative to the height of the anaerobic reactor, preferably in a reactor part which surrounds the lower 20%, particularly preferably the lower 10% and particularly preferably the lower 5% of the anaerobic reactor.

[0039] According to a particularly preferred embodiment of the invention, the lower region of the anaerobic reactor is at least partially conical.

[0040] According to one variant, the lower region of the anaerobic reactor is designed as a cone, wherein the cone extends over 1 to 50%, preferably 1 to 20% and particularly preferably 1 to 10% of the height of the anaerobic reactor.

[0041] According to an alternative variant, it is preferred that the lower region of the anaerobic reactor is designed in a zigzag manner when viewed in cross section, wherein the zigzag region extends over 1 to 50%, particularly preferably 1 to 20% and very particularly preferably 1 to 10% of the height of the anaerobic reactor.

[0042] Furthermore, the anaerobic reactor preferably has one or more gas separators in the middle upper region of the anaerobic reactor, preferably at a height between 30 and 90% and particularly preferably between 60 and 90% of the height of the anaerobic reactor, which are designed in such a way that they prevent the anaerobic microorganism granules from flowing further upward in the anaerobic reactor and thus cause the gas adhering to the surface of the anaerobic microorganism granules to separate and be discharged from the anaerobic reactor through the gas separators. A clean water overflow is preferably arranged above the gas separator but below the liquid level, which is connected to a discharge line for purified process water.

[0043] The solid / liquid separator is preferably designed to be gas-tight such that during its operation, the process water supplied from the anaerobic reactor and the fraction of the solid / liquid separator that is poor in inorganic solid materials do not come into contact with air.

[0044] In an improved solution of the present invention, it is proposed that the solid / liquid separation device includes one or more centrifugal separators.

[0045] Particularly good results are achieved if the solid / liquid separation device comprises one or more cyclone separators.

[0046] According to another particularly preferred embodiment of the present invention, the solid / liquid separation device is arranged in such a way and the filling height in the anaerobic reactor can be adjusted in such a way that when the device and / or the paper machine is in operation, the process water can be conveyed from the anaerobic reactor to the solid / liquid separation device via the pipeline solely by gravity.

[0047] The return line for the fraction depleted in inorganic solid material preferably opens into the supply line to the anaerobic reactor.

[0048] Furthermore, the invention relates to a machine for making paper from waste paper, comprising a device for treating waste paper as described above and a papermaking machine as described above, wherein the device comprises one, two or more stages, wherein each stage comprises a dewatering unit and at least one further unit selected from one or more of the group consisting of a material dissolver, a sorting device and an oxidation / reduction unit, wherein each stage and the papermaking machine respectively comprise a process water treatment unit as described above.

[0049] Preferably, the paper machine comprises at least one unit selected from a centrifugal classifier, a fine classifying device, a paper machine-forming section, a paper machine-pressing section, a waste handling unit, a fiber recovery unit and a drying section, preferably at least two, further preferably at least three, particularly preferably at least four, further preferably at least five, further preferably at least six and preferably at most all of these units.

[0050] Here, the process water treatment unit is connected to at least one unit of at least one stage of the device for treating waste paper and / or to at least one unit of the paper machine so that when the machine is running, the process water to be purified is conveyed from at least one of the units to the anaerobic reactor and after the process water treatment step, the purified process water is directed back to at least one of the units. In addition, it is preferred that the process water treatment unit also includes one or more of a material recovery unit, a pre-acidification reactor, a lime removal unit and a filtration unit in addition to an anaerobic reactor, a solid / liquid separation device and an optional measuring device. Preferably, the process water treatment unit includes two, further preferably three and preferably at most all four of the aforementioned additional units. A preferred order of these units, viewed from upstream to downstream, is a material recovery unit, a pre-acidification reactor, an anaerobic reactor, a lime removal unit and a filtration unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The present invention will be described in more detail below with reference to the accompanying drawings, in which:

[0052] Figure 1 The schematic diagram of a machine according to the invention for producing paper from waste paper according to an exemplary embodiment of the invention is shown, which comprises a device according to the invention for purifying process water which is circulated in the device.

[0053] Figure 2 Shown in Figure 1 A more detailed schematic diagram of the device according to the invention for purifying process water contained in a machine according to the invention for producing paper from waste paper is shown in FIG.

[0054] Figure 3A schematic diagram of a device according to the invention for purifying process water is shown according to a further exemplary embodiment. DETAILED DESCRIPTION

[0055] exist Figure 1 The device shown in FIG. 1 comprises a waste paper treatment device 100 and a paper machine 200 arranged downstream of the waste paper treatment device 100 and connected to the waste paper treatment device 100. Here, the waste paper treatment device 100 comprises two substantially decoupled from each other and connected to the waste paper treatment device 100. Figure 1 The stages or loops 101a and 101b are outlined by dashed-dotted boxes.

[0056] Said Paper handling device The first stage 101a of 100 comprises a raw material inlet 102, a pulper or material dissolver 105, a sorting device 110a and a dewatering unit 115a, which are arranged in sequence and are respectively connected to each other. In the meaning of the present invention, "pulper or material dissolver 105" does not only refer to Figure 1 The schematically shown arrangement of one device component also refers in particular to a device combination comprising a plurality of individual device components, which includes all components or assemblies necessary for the dissolution of the material. This also applies to the sorting device 110a, the dewatering unit 115a and all other Figure 1 The components shown in .

[0057] The material dissolver 105 and the sorting device 110a are connected to a waste treatment unit 118a via pipelines, respectively.

[0058] Furthermore, the first stage 101a of the waste paper processing plant 100 comprises a process water treatment unit 116a, to which the process water produced in these plant parts is supplied from the waste material processing unit 118a, the sorting device 110a and the dewatering unit 115a via corresponding pipelines. The process water treatment unit 116a comprises: a material recovery unit 120a; a pre-acidification reactor 121a; an apparatus for purifying process water according to the invention, which comprises an anaerobic reactor 125a doped with anaerobic microorganisms and a solid / liquid separation device 126a (for separating the process water discharged from the anaerobic reactor 125a into a part poor in inorganic solid materials and a part rich in inorganic solid materials), the solid / liquid separation device having a discharge pipeline 127a for the part rich in inorganic solid materials and a return pipeline 128a for returning the part poor in inorganic solid materials to the anaerobic reactor 125a; and a lime removal unit 130a and a filter unit 140a. Here, the lime removal unit 130a is designed as a pressure relief flotation mechanism. The device for purifying process water, which includes an anaerobic reactor 125a and a solid / liquid separation device 126a, is Figure 2 1 and described in more detail below. A return line 145a leads from the filter unit 140a back to the material dissolver 105. In addition to or instead of the material recovery unit 120a, a depulping unit (not shown) can be provided in the waste paper processing device 100.

[0059] For the sake of completeness, it is to be noted that the filter unit 140a is optional and can also be omitted, i.e. the filtrate can be fed directly back from the lime removal unit 130a into the return line 145a. Furthermore, a centrifugal separator can be arranged upstream or downstream of the separator 110a. Furthermore, the material recovery unit 120a can be combined with a depulping unit which is designed, for example, as a microflotation device.

[0060] Different from the first stage 101a, the second stage 101b of the waste paper processing device 100 includes a sorting device 110b connected to a dewatering unit 115a, an oxidation unit or a reduction unit 112, and a dewatering unit 115b, which are arranged in sequence and connected to each other. In addition, the second stage 101b has a process water treatment unit 116b, which is similarly constructed to the process water treatment unit 116a of the first stage 101a, that is, it includes a lime removal unit 130b designed as a pressure relief flotation mechanism, wherein the filter unit 140b of the second stage 101b of the waste paper processing device 100 is connected to the sorting device 110b via a return line 145b and is connected to the return line 145a from the filter unit 140a of the first stage 101a of the waste paper processing device 100 via a branch line 170a. When the sorting device 110b and the oxidation unit or reduction unit 112 are connected to the waste treatment unit 118b via corresponding pipelines, the dehydration unit 115b is directly connected to the material recovery unit 120b of the process water treatment unit 116b. In addition, a pipeline leads from the oxidation unit or reduction unit 112 to the material recovery unit 120b.

[0061] For the sake of completeness, it is to be noted that the filter unit 140b is also optional and can also be omitted. In addition, a centrifugal separator can be arranged before or after the separator 110b. In addition, the material recovery unit 120b can be combined with a depulping unit which is designed, for example, as a microflotation device.

[0062] The paper machine 200 includes a centrifugal classifier 202, a fine classifier 204, a paper machine-forming section 206, a paper machine-pressing section 208, and a drying section 210, which are arranged in sequence and connected to each other. The centrifugal classifier 202 and the fine classifier 204 are connected to a waste processing unit 212, and the paper machine-forming section 206 and the paper machine-pressing section 208 are connected to a fiber recovery unit 214. Furthermore, the waste treatment unit 212 and the fiber recovery unit 214 are connected to a process water treatment unit 216 via corresponding pipelines, and the process water treatment unit is composed of: a depulping unit 220; a pre-acidification reactor 221; an apparatus for purifying process water according to the present invention, which includes an anaerobic reactor 225 mixed with anaerobic microorganisms and a solid / liquid separation device 226 (for separating the process water discharged from the anaerobic reactor 225 into a part poor in inorganic solid materials and a part rich in inorganic solid materials), the solid / liquid separation device having a discharge pipeline 227 for the part rich in inorganic solid materials and a return pipeline 228 for returning the part poor in inorganic solid materials to the anaerobic reactor 225; and a lime removal unit 230 and a filter unit 240. In addition, a return pipeline 270 leads from the filter unit 240 of the paper machine 200 to the pipeline 170 of the second stage 101b of the waste paper treatment device 100. The fiber recovery unit 214 and the depulping unit 220 can also be combined in a plant component which is designed, for example, as a microflotation device.

[0063] Furthermore, a fresh water supply line 280 is provided in the region of the paper machine 200, via which fresh water can be supplied to the paper machine. The fresh water supply line 280 can lead into the paper machine 200 at a plurality of locations, for example into the supply line to the centrifugal separator 202 and / or into the paper machine forming section 206 and / or the paper machine pressing section 208, so that the exact position of the fresh water supply line 280 is not limited to the following. Figure 1 Furthermore, a process water line 300 is provided in the device, via which excess process water can be discharged from the device. The process water line 300 can also be arranged at different locations in the device, for example at the line 170, so that the exact location of this process water line 300 is not specified. Figure 1. The process water line 300 for excess process water leads to a mechanical depulping unit 305, downstream of which a cooling unit 310 and a biological treatment unit 315 are arranged. From the biological treatment unit 315, a line leads either to a public (or joint) sewage treatment plant for further purification or to a public body of water 400, for example to a river; however, if necessary, a branch stream or the entire treated process water can also be led back to the paper machine or the material handling facility.

[0064] exist Figure 2 The device for purifying process water according to the present invention, which is shown in more detail in FIG. 1 , comprises an anaerobic reactor 125a and a solid / liquid separation device 126a configured as a cyclone separator 126a. A conveying line 500 leads into the anaerobic reactor 125a in the lower region, via which the process water is conveyed from the pre-acidification reactor 121a to the anaerobic reactor 125a. In addition, microbial granules 502 from anaerobic microorganisms are located in the anaerobic reactor 125a, which degrade the organic pollutants contained in the process water into carbon dioxide and methane. A plurality of gas separators 504 are arranged in the upper region of the anaerobic reactor 125a to prevent the microbial granules with attached bubbles from further floating in the anaerobic reactor 125a and to separate the bubbles attached to the microbial granules from the microbial granules. A clean water overflow 508 is arranged above the gas separator 504 but below the liquid level 506. In addition, a gas discharge line 510 from the anaerobic reactor 125a and a discharge line 512 for purified process water are introduced into the upper region of the anaerobic reactor 125a. The lower region of the anaerobic reactor 125a is constructed as a cone 514 and the pipeline 129 for conveying process water is introduced into the solid / liquid separator 126a at the lower tip of the cone 514. A valve 516 is provided in the pipeline 129, which is controlled by a control mechanism (not shown). The pipeline 129 leads to the solid / liquid separator 126a constructed as a cyclone separator 126a, in which the process water together with the solid materials dissolved and dispersed therein are separated into a part lacking in inorganic solid materials and a part enriched in inorganic solid materials by centrifugal force. The inorganic solids-rich fraction is drawn off from the lower region of the cyclone 126a and discharged from the system via a discharge line 127a, while the inorganic solids-poor fraction is guided into the conveying line 500 via a return line 128a.

[0065] exist Figure 1 and 2During operation of the illustrated system, waste paper is continuously introduced via the raw material inlet 102 into the material dissolver 105 of the first stage 101a of the waste paper treatment plant 100, where the waste paper is mixed with process water supplied via the return line 145a and comminuted for fiber recovery. When the fibers obtained in the material dissolver 105 are continuously transferred as a fiber suspension to the sorting device 110a, the process water produced in the material dissolver 105, which may contain fiber residues, is firstly guided to the waste treatment unit 118a and from there, after separation of the waste, to the material recovery unit 120a of the process water treatment unit 116a of the waste paper treatment plant 100. In the sorting device 110a, light or heavy foreign matter larger than the fibers is removed from the fiber suspension, for example, by means of a screen barrier and typically in multiple stages. For example, coarse dirt in the form of plastic films and plastic flakes. In addition, flotation can also be carried out in the sorting device 110a in order to remove pigments, inks and pigment particles (de-inking). In addition, fines and ash can be separated during material washing. In the dewatering unit 115a, which is arranged downstream of the sorting device 110a and is preferably designed as a dewatering filter and / or a screw press, the fiber suspension is thickened by removing process water so that it reaches the sorting device 110b of the second stage 101b of the waste paper processing device 100 from the dewatering unit 115a as a thickened fiber suspension. A substream of the process water produced in the sorting device 110a is directed to a waste material treatment unit 118a, while another substream of the process water produced in the sorting device 110a is directed together with the process water produced in the dewatering unit 115a of the first stage 101a via corresponding pipelines directly to a material recovery unit 120a of a process water treatment unit 116a of the first stage 101a of the waste paper treatment device 100, where fiber materials contained in the process water are separated from the process water and the fiber materials are fed back to the treatment process. Preferably, the material recovery unit 120a is designed as a pressure relief flotation mechanism.

[0066] exist Figure 1In the device shown, the process water produced in the waste treatment unit 118a is led to the material recovery unit 120a. The process water from which the fiber material is removed is continuously led from the material recovery unit 120a to the pre-acidification reactor 121a, in which the process water is hydrolyzed and acidified. Subsequently, the process water is led to the device for purifying process water according to the present invention, which includes an anaerobic reactor 125a mixed with anaerobic microorganisms and a solid / liquid separation device 126a (the solid / liquid separation device is used to separate the process water discharged from the anaerobic reactor 125a into a part lacking in inorganic solid materials and a part rich in inorganic solid materials), the solid / liquid separation device having a discharge line 127a for the part rich in inorganic solid materials and a return line 128a for returning the part poor in inorganic solid materials to the anaerobic reactor 125a. In the anaerobic reactor 125a of the microbial granules 502 from anaerobic microorganisms, the organic impurities contained in the process water are mainly decomposed into carbon dioxide and methane by the action of anaerobic microorganisms. The gas formed in this way is mostly attached to the microbial granules 502 whose density is reduced thereby in the form of bubbles, so that the microbial granules 502 with attached bubbles rise in the anaerobic reactor 125a. Here, these microbial granules reach the gas separator 504 arranged in the upper area of ​​the anaerobic reactor 125a, in which the biogas is separated from the microbial granules 502 and then discharged from the anaerobic reactor 125a through the gas discharge line 510. The purified process water rises further in the anaerobic reactor 125a by the upward directed flow caused by the injection of process water, where the process water is drawn out through the clean water overflow 508 and discharged via the discharge line 512 for the purified process water and is supplied to the lime removal unit 130a and further to the filter unit 140a. Inorganic solid materials, such as lime in particular, originating from waste paper are not decomposed by the microbial granules 502 and therefore accumulate in the anaerobic reactor 125a. The microbial granules 502 act as crystallization nuclei for the deposition of inorganic solid materials and in particular lime due to their structure and size, so that inorganic solid materials and in particular lime are deposited on the microbial granules 502 with a certain content of inorganic solid materials and in particular lime with the disadvantages described in detail above. In order to prevent this, according to the present invention, a process water sample is taken from the anaerobic reactor 125a at a specified time, and the content of inorganic solid materials in the process water sample is measured.This is done by filtering a sample of the process water, drying the residue obtained during the filtration in an oven at 105° C. until no more mass loss occurs in order to obtain a dried solid material residue, measuring the mass of the dried solid material residue, thermally treating the dried solid material residue in an oven at a temperature of 550° C. until no more mass loss occurs in order to obtain a heat-treated solid material residue, and measuring the mass of the heat-treated solid material residue. The content of inorganic solid material in the process water is then easily calculated as the quotient of the mass of the heat-treated solid material residue and the mass of the dried solid material residue. Certain values ​​are entered into a control device (not shown) into which a limit value for the content of inorganic solid material in the process water, for example 37% by weight, has already been entered at the beginning of the method. The control device compares the measured solid material content with the limit value. If the measured inorganic solid content in the process water is higher than the limit value, the valve 516 arranged in the conveying line 129 is controlled by the control device so that the process water is continuously discharged from the anaerobic reactor 125a and conveyed to the solid / liquid separation device 126a. In the solid / liquid separation device 126a designed as a cyclone separator 126a, the process water is separated into a part poor in inorganic solids and a part rich in inorganic solids. The part poor in inorganic solids is returned to the anaerobic reactor 125a via a return line 128a, while the part rich in inorganic solids is discharged from the device via a discharge line 127a. Here, the method is preferably implemented so that the process water is separated in the cyclone separator 126a, so that the part poor in inorganic solids has, for example, an inorganic solid content of 0.7 to 1.0 kg / l, and the part rich in inorganic solids has, for example, an inorganic solid content of 2.5 kg / l, and the portion poor in inorganic solids is 90% by volume of the volume flow of the process water introduced into the cyclone separator 126a and the portion rich in inorganic solids is 100% by volume of the volume flow of the process water introduced into the cyclone separator 126a. As soon as a later measurement of another sample of the process water shows a value below the limit value, the control device switches off the valve 516, so that process water is no longer supplied to the solid / liquid separation device 126a or the cyclone separator 126a. The purified process water, ie freed from chemical and biological contamination, is conveyed from the anaerobic reactor 125a via a line 512 to a downstream deliming unit 130a and then to a filter unit 140a, which is designed, for example, as a sand filter unit, in order to remove residual particulate matter from the process water.Furthermore, a desalination unit (not shown) may be arranged downstream of the filter unit 140 a .

[0067] In the process water treatment unit 116a of the first stage 101a of the waste paper processing plant 100 , the cleaned and decalcified process water is fed back into the pulper or material dissolver 105 via the return line 145a .

[0068] The thickened fiber stock discharged from the dewatering unit 115a of the first stage 101a of the waste paper processing device 100 enters the sorting device 110b and from there into the oxidation unit or reduction unit 112 before the fiber stock is thickened in the dewatering unit 115b of the second stage 101b, in order to remove as much process water as possible from the fiber stock. Similar to the first stage 101a of the waste paper processing device 100, a substream of the process water produced in the sorting device 110b and the process water produced in the oxidation unit or reduction unit 112 is led to the waste material processing unit 118b, and the process water produced there is led to the material recovery unit 120b. Another branch of the process water produced in the oxidation unit or reduction unit 112 and the process water produced in the dewatering unit 115b are directly led to the material recovery unit 120b of the process water treatment unit 116b of the second stage 101b of the waste paper processing device 100, and are purified and decalcified in the process water treatment unit 116b. The process water treated in this way is mostly returned to the sorting device 110b from the filter unit 140b via the pipeline 170 and the return pipeline 145b, while any excess process water is returned to the first stage 101a of the waste paper processing device 100 via the branch pipeline 170a and is led to the return pipeline 145a leading to the material dissolver 105.

[0069] In the paper machine 200, the thickened fibrous stock suspension continuously conveyed from the dewatering unit 115b is processed into paper by means of a centrifugal classifier 202, a fine classifier 204, a paper machine forming section 206, a paper machine press section 208, and a drying section 210, wherein fractions having a higher or lower specific gravity than water are separated in the centrifugal classifier 202. While the process water produced in the centrifugal classifier 202 and the fine classifier 204 is directed to the waste treatment unit 212, the process water produced in the paper machine forming section 206 and the paper machine press section 208 is directed to the fiber recovery unit 214. While the waste is dewatered in the waste treatment unit 212, the process water from the paper machine forming section 206 and the paper machine press section 208 is pre-depulped and separated from the fibers in the fiber recovery unit 214. The process water produced in the waste treatment unit 212 and in the fiber recovery unit 214 is continuously led to the process water treatment unit 216 of the paper machine 200 and flows there in sequence through the depulping unit 220, the pre-acidification reactor 221, the anaerobic reactor 225, and if a limit value is exceeded, the solid / liquid separation device, the lime removal unit 230 and the filter unit 240 operate like the corresponding plant parts of the process water treatment units 116a, 116b of the waste paper treatment plant 100 described above. As an alternative, the process water produced in the waste treatment unit 212 can be discharged from the plant as waste water and only the process water produced in the fiber recovery unit 214 is continuously led through the process water treatment unit 216 of the paper machine 200. The purified and decalcified process water extracted from the filter unit 240 is mostly returned to the centrifugal separator 202 of the paper machine 200 via the return line 270 and the branch line 270b, while any excess process water is guided via the branch line 270a to the line 170 leading out of the filter unit 140b of the second stage 101b of the waste paper processing device 100.

[0070] A completely closed process water circuit is possible in principle, but may lead to an enrichment of impurities in the long term, which ultimately impairs the economic viability of the plant. A relatively small amount of fresh water, relative to the amount of water evaporated in the drying section, is continuously fed to the process, preferably the paper machine 200, via the fresh water feed line 280. In production with special requirements for a low impurity content, such as salt, there is the possibility of removing a corresponding amount of process water from the process via the process water line 300 and further purifying it via the depulping unit 305, the cooling unit 310 and the biological treatment unit 315 before the water flow is discharged as waste water into a public sewer or water body 400. In addition, the process water optionally discharged from the waste treatment units 118a, 118b, 212, as mentioned above, can also be removed from the process via the process water line 300 and purified via the depulping unit 305, the cooling unit 310 and the biological treatment unit 315 and fed back into the process.

[0071] exist Figure 1 In the embodiment, the device comprises a two-stage material handling. Of course, in particular when making multi-layer paper, two or more parallel material handlings can also be arranged.

[0072] Figure 2 The anaerobic reactor 125a shown has a lower region which is designed as a cone. Figure 3 In the embodiment shown in FIG. 1 , the anaerobic reactor 125a can also have a lower region with multiple cones. Figure 3 As shown in , in this alternative embodiment, the lower region of the anaerobic reactor is zigzag-shaped when viewed in cross section. Thus, in this embodiment, the reactor bottom comprises a plurality of adjacent conical regions, so that the total area of ​​the slope of the reactor wall of the reactor bottom is larger than in the previously described embodiment, in which the reactor bottom is configured as a cone.

[0073] Reference numerals list

[0074] 100 Waste paper processing device

[0075] 101a The first stage of waste paper processing plant

[0076] 101b Second stage of waste paper treatment plant

[0077] 102 Raw material entrance

[0078] 105 Pulper / Material Dissolver

[0079] 110a, 110b sorting device

[0080] 112 Oxidation unit / reduction unit

[0081] 115a, 115b Dehydration unit

[0082] 116a, 116b Process water treatment unit for material / waste paper treatment plant

[0083] 118a, 118b Waste treatment unit

[0084] 120a, 120b Material recovery unit

[0085] 121a, 121b pre-acidification reactor

[0086] 125a, 125b anaerobic reactor

[0087] 126a, 126b solid / liquid separation device / cyclone separator

[0088] 127a, 127b discharge pipeline

[0089] 128a, 128b return pipeline

[0090] 129 Pipeline for conveying process water to the solid / liquid separation device

[0091] 130a, 130b Lime elimination unit

[0092] 140a, 140b Filter unit

[0093] 145a, 145b return pipeline

[0094] 170 pipeline

[0095] 170a branch pipe

[0096] 200 Paper Machine

[0097] 202 Centrifugal separator

[0098] 204 Fine sorting device

[0099] 206 Paper Machine - Forming Section

[0100] 208 Paper Machine - Pressing Section

[0101] 210 Drying Section

[0102] 212 Waste treatment unit

[0103] 214 Fiber Recovery Unit

[0104] 216 Process water treatment unit for paper machine

[0105] 220 Depulping Device

[0106] 221 Pre-acidification reactor

[0107] 225 Anaerobic Reactor

[0108] 226 Solid / Liquid Separation Device / Cyclone Separator

[0109] 227 Discharge line

[0110] 228 Return line

[0111] 230 Lime Removal Unit

[0112] 240 Filter Unit

[0113] 270 Return line

[0114] 270a, 270b branch pipeline

[0115] 280 Fresh water delivery pipeline

[0116] 300 Process water pipeline

[0117] 305 Mechanical depulping units

[0118] 310 Cooling Unit

[0119] 315 Biological Processing Unit

[0120] 400 Public waters

[0121] 500 Delivery pipeline

[0122] 502 Microbial particles

[0123] 504 Gas Separator

[0124] 506 Liquid Level

[0125] 508 Clean water overflow

[0126] 510 Gas exhaust line

[0127] 512 Discharge line for purified process water

[0128] 514 Cone / conical area

[0129] 516 Valve

Claims

1. A method for the continuous purification of process water, the process water being circulated in a device (100) for treating waste paper of a machine for making paper from waste paper and / or in a paper machine (200), wherein the process water to be purified is fed from at least one unit of the device (100) and / or the paper machine (200) to a process water treatment unit, the process water treatment unit having an anaerobic reactor (125a, 125b, 225) including one or more gas separators (504), the process water in the anaerobic reactor (125a, 125b, 225) being brought into contact with anaerobic microorganisms in order to degrade impurities contained in the process water, and the purified process water being discharged from the anaerobic reactor (125a, 125b, 225) and fed back to at least one unit of the device (100) and / or the paper machine (200), wherein: At least one unit is selected from one or more of a material dissolver (105), a sorting device (110a, 110b), a dewatering unit (115a, 115b), an oxidation / reduction unit (112), a centrifugal sorter (202), a fine sorting device (204), a paper machine-forming section (206), a paper machine-pressing section (208), a waste treatment unit (118a, 118b, 212), a fiber recovery unit (214) and a drying section (210), wherein in the method the content of inorganic solid materials in the process water contained in the anaerobic reactor (125a, 125b, 225) is measured continuously or discontinuously, and if the content of inorganic solid materials in the process water contained in the anaerobic reactor (125a, 125b, 225) is If the content of inorganic solid materials in the process water exceeds a preset limit value, the process water is continuously conveyed from the anaerobic reactor (125a, 125b, 225) to the solid / liquid separation device (126a, 126b, 226) so as to be separated into a part poor in inorganic solid materials and a part rich in inorganic solid materials, wherein the part poor in inorganic solid materials is at least partially guided back into the anaerobic reactor (125a, 125b, 225) and the part rich in inorganic solid materials is discharged from the device (100) and / or the paper machine (200) until the content of inorganic solid materials in the process water contained in the anaerobic reactor (125a, 125b, 225) is lower than the preset limit value.

2. The method according to claim 1, characterized in that The process water to be continuously supplied to the solid / liquid separation device (126a, 126b, 226) is taken from the anaerobic reactor (125a, 125b, 225) from the lower area of ​​the anaerobic reactor (125a, 125b, 225) relative to the height of the anaerobic reactor (125a, 125b, 225).

3. The method according to claim 2, characterized in that The process water to be continuously fed to the solid / liquid separation device (126a, 126b, 226) is taken from the lower 20% of the anaerobic reactor (125a, 125b, 225).

4. The method according to claim 2, characterized in that: The process water to be continuously fed to the solid / liquid separation device (126a, 126b, 226) is taken from the lower 10% of the anaerobic reactor (125a, 125b, 225).

5. The method according to claim 2, characterized in that: The process water to be continuously fed to the solid / liquid separation device (126a, 126b, 226) is taken from the lower 5% of the anaerobic reactor (125a, 125b, 225).

6. The method according to any one of claims 1 to 5, characterized in that When viewed in cross section, the lower region of the anaerobic reactor ( 125 a , 125 b , 225 ) is designed in a zigzag shape.

7. The method according to claim 6, characterized in that The sawtooth-shaped region extends over 1 to 50% of the height of the anaerobic reactor (125a, 125b, 225).

8. The method according to claim 6, characterized in that The sawtooth-shaped region extends over 1 to 20% of the height of the anaerobic reactor (125a, 125b, 225).

9. The method according to claim 6, characterized in that The sawtooth-shaped region extends over 1 to 10% of the height of the anaerobic reactor (125a, 125b, 225).

10. The method according to any one of claims 1 to 5, characterized in that When viewed in cross section, the lower region of the anaerobic reactor (125a, 125b, 225) is configured as a cone (514).

11. The method according to claim 10, characterized in that The cone (514) extends over 1 to 20% of the height of the anaerobic reactor (125a, 125b, 225).

12. The method according to claim 10, characterized in that The cone (514) extends over 1 to 10% of the height of the anaerobic reactor (125a, 125b, 225).

13. The method according to any one of claims 1 to 5, characterized in that The limit value for the content of inorganic solid materials in the process water contained in the anaerobic reactor (125a, 125b, 225) is predetermined to be a value between 30 and 45% by weight.

14. The method according to claim 13, characterized in that The limit value for the content of inorganic solid materials in the process water contained in the anaerobic reactor (125a, 125b, 225) is predetermined to be a value between 34 and 40% by weight.

15. The method according to claim 13, characterized in that The limit value for the content of inorganic solid materials in the process water contained in the anaerobic reactor (125a, 125b, 225) is predetermined to be a value between 36 and 38% by weight.

16. The method according to any one of claims 1 to 5, characterized in that The process water from the anaerobic reactor (125a, 125b, 225) is continuously fed to the solid / liquid separation device (126a, 126b, 226), and the portion lacking in inorganic solid materials is at least partially directed back into the anaerobic reactor (125a, 125b, 225) until the content of inorganic solid materials in the process water contained in the anaerobic reactor (125a, 125b, 225) is at least 1% lower than the preset limit value.

17. The method according to claim 16, characterized in that The portion depleted in inorganic solids is at least partially directed back into the anaerobic reactor (125a, 125b, 225) until the content of inorganic solids in the process water contained in the anaerobic reactor (125a, 125b, 225) is at least 2% below the preset limit value.

18. The method according to claim 16, characterized in that The portion depleted in inorganic solids is at least partially directed back into the anaerobic reactor (125a, 125b, 225) until the content of inorganic solids in the process water contained in the anaerobic reactor (125a, 125b, 225) is at least 5% lower than the preset limit value.

19. The method according to claim 16, characterized in that The portion depleted in inorganic solids is at least partially directed back into the anaerobic reactor (125a, 125b, 225) until the content of inorganic solids in the process water contained in the anaerobic reactor (125a, 125b, 225) is at least 10% below the preset limit value.

20. The method according to any one of claims 1 to 5, characterized in that The process water is separated in the solid / liquid separation device (126a, 126b, 226) in such a way that, with respect to the volume flow of the process water supplied to the solid / liquid separation device (126a, 126b, 226), the portion of the part depleted in inorganic solid materials is at least 70% by volume and the portion of the part enriched in inorganic solid materials is 100% by volume.

21. The method according to claim 20, characterized in that The process water is separated in the solid / liquid separation device (126a, 126b, 226) in such a way that the proportion of the part poor in inorganic solid materials is at least 80% by volume of the volume flow of the process water supplied to the solid / liquid separation device (126a, 126b, 226).

22. The method according to claim 20, characterized in that The process water is separated in the solid / liquid separation device (126a, 126b, 226) in such a way that the proportion of the part poor in inorganic solid materials is at least 90% by volume relative to the volume flow of the process water supplied to the solid / liquid separation device (126a, 126b, 226).

23. The method according to any one of claims 1 to 5, characterized in that The process water is separated in the solid / liquid separation device (126a, 126b, 226) in such a way that the content of inorganic solid materials in the inorganic solid material-enriched part is at least 25% higher than the content of inorganic solid materials in the inorganic solid material-depleted part.

24. The method according to claim 23, characterized in that The process water is separated in the solid / liquid separation device (126a, 126b, 226) in such a way that the content of inorganic solid materials in the inorganic solid material-enriched part is at least 50% higher than the content of inorganic solid materials in the inorganic solid material-depleted part.

25. The method according to claim 23, characterized in that The process water is separated in the solid / liquid separation device (126a, 126b, 226) in such a way that the content of inorganic solid materials in the inorganic solid material-enriched portion is at least 75% higher than the content of inorganic solid materials in the inorganic solid material-depleted portion.

26. The method according to claim 23, characterized in that The process water is separated in the solid / liquid separation device (126a, 126b, 226) in such a way that the content of inorganic solid materials in the part rich in inorganic solid materials is at most at least 100% higher than the content of inorganic solid materials in the part poor in inorganic solid materials.

27. The method according to any one of claims 1 to 5, characterized in that The solid / liquid separation device (126a, 126b, 226) includes one or more centrifugal separators.

28. The method according to claim 27, characterized in that The solid / liquid separation device (126a, 126b, 226) includes one or more cyclone separators.

29. An apparatus (100) for processing waste paper and / or a papermaking machine (200) for a machine for making paper from waste paper, wherein: The device (100) and / or the paper machine (200) comprises a process water treatment unit (116a, 116b, 216) for purifying process water, the process water being circulated in the device (100) and / or the paper machine (200), and the device and / or the paper machine also comprises at least one or more units selected from the group consisting of a material dissolver (105), a sorting device (110a, 110b), a dewatering unit (115a, 115b), an oxidation / reduction unit (112), a centrifugal classifier (202), a fine sorting device (204), a paper machine-forming section (206), a paper machine-pressing section (208), a waste treatment unit (118a, 118b, 212), a fiber recovery unit (214) and a drying section (210), and wherein the process water treatment unit (116a, 116b, 216) comprises: i) an anaerobic reactor (125a, 125b, 225) comprising one or more gas separators (504), the anaerobic reactor being used for anaerobically purifying process water, the anaerobic reactor having at least one conveying pipeline (500) for conveying the process water to be purified into the anaerobic reactor (125a, 125b, 225) and at least one discharge pipeline for discharging the purified process water from the anaerobic reactor (125a, 125b, 225), wherein the process water A water treatment unit (116a, 116b, 216) is connected to at least one of the at least one units so that during operation of the device (100) and / or the paper machine (200), process water to be purified is supplied from at least one of the process water treatment units (116a, 116b, 216) to the anaerobic reactor (125a, 125b, 225) and the purified process water is fed back to the at least one unit after the process water treatment step, and ii) a solid / liquid separation device (126a, 126b, 226) for separating process water discharged from the anaerobic reactor (125a, 125b, 225) into a part poor in inorganic solid materials and a part rich in inorganic solid materials, the solid / liquid separation device having a discharge pipeline (127a, 127b, 227) for the part rich in inorganic solid materials and a return pipeline (128a, 128b, 228) for at least partially returning the part poor in inorganic solid materials to the anaerobic reactor (125a, 125b, 225), wherein another pipeline leads from the anaerobic reactor (125a, 125b, 225) to the solid / liquid separation device (126a, 126b, 226) for conveying the process water discharged from the anaerobic reactor (125a, 125b, 225), characterised in that the device and / or the paper machine further comprises (iii) a measuring device for measuring the content of inorganic solid materials in the process water contained in the anaerobic reactor (125a, 125b, 225), Furthermore, the device and / or the paper machine also comprises a control device, which is capable of receiving measured data about the content of inorganic solid materials in the process water contained in the anaerobic reactor (125a, 125b, 225) and into which limit values ​​and selectable threshold values ​​can be input, wherein the control device is designed so that when the input limit value for the content of inorganic solid materials in the process water in the anaerobic reactor (125a, 125b, 225) is exceeded, the control device automatically starts to remove the process water from the anaerobic reactor (125a, 125b, 225). a, 125b, 225) and conveying the process water to the solid / liquid separation device (126a, 126b, 226), and when the inorganic solid material content in the process water contained in the anaerobic reactor (125a, 125b, 225) falls below the limit value or the input threshold value, the control mechanism automatically ends the process of continuously discharging the process water from the anaerobic reactor (125a, 125b, 225) and conveying the process water to the solid / liquid separation device (126a, 126b, 226).

30. The device (100) and / or the paper machine (200) according to claim 29, characterized in that When viewed in cross section, a lower region of the anaerobic reactor (125a, 125b, 225) is designed in a zigzag manner, wherein the zigzag region extends over 1 to 50% of the height of the anaerobic reactor (125a, 125b, 225).

31. The device (100) and / or the paper machine (200) according to claim 30, characterized in that: The sawtooth-shaped region extends over 1 to 20% of the height of the anaerobic reactor (125a, 125b, 225).

32. The device (100) and / or the paper machine (200) according to claim 30, characterized in that: The sawtooth-shaped region extends over 1 to 10% of the height of the anaerobic reactor (125a, 125b, 225).

33. The device (100) and / or the paper machine (200) according to any one of claims 29 to 32, characterized in that: When viewed in cross section, a lower region of the anaerobic reactor (125a, 125b, 225) is designed as a cone (514), wherein the cone (514) extends over 1 to 50% of the height of the anaerobic reactor (125a, 125b, 225).

34. The device (100) and / or the paper machine (200) according to claim 33, characterized in that The cone (514) extends over 1 to 20% of the height of the anaerobic reactor (125a, 125b, 225).

35. The device (100) and / or the paper machine (200) according to claim 33, characterized in that in, The cone (514) extends over 1 to 10% of the height of the anaerobic reactor (125a, 125b, 225).

36. The device (100) and / or the paper machine (200) according to any one of claims 29 to 32, characterized in that The solid / liquid separation device (126a, 126b, 226) includes one or more centrifugal separators.

37. The device (100) and / or the paper machine (200) according to claim 36, characterized in that The solid / liquid separation device (126a, 126b, 226) includes one or more cyclone separators.

38. The device (100) and / or the paper machine (200) according to any one of claims 29 to 32, characterized in that The one or more gas separators (504) are arranged in the anaerobic reactor (125a, 125b, 225) at a height between 30 and 90% relative to the height of the anaerobic reactor (125a, 125b, 225).

39. The device (100) and / or the paper machine (200) according to claim 38, characterized in that The one or more gas separators (504) are arranged in the anaerobic reactor (125a, 125b, 225) at a height between 60 and 90% relative to the height of the anaerobic reactor (125a, 125b, 225).

40. The device (100) and / or the paper machine (200) according to any one of claims 29 to 32, characterized in that The one or more gas separators (504) are configured such that the anaerobic microbial granules (502) hinder further upward flow in the anaerobic reactor (125a, 125b, 225) and thus cause the following result: the gas adhering to the surface of the anaerobic microbial granules (502) is separated and discharged from the anaerobic reactor (125a, 125b, 225) via the gas separator.

41. The device (100) and / or paper machine (200) according to any one of claims 29 to 32, characterized in that The device (100) and / or the paper machine (200) is designed to carry out the method according to any one of claims 1 to 28.

42. A machine for making paper from waste paper, comprising the device (100) for treating waste paper and a papermaking machine (200) according to any one of claims 29 to 41, characterized in that: The device (100) comprises one, two or more stages, wherein each stage comprises a dewatering unit (115a, 115b) and at least one additional unit, wherein the additional unit is selected from one or more units of a material dissolver (105), a sorting device (110a, 110b) and an oxidation / reduction unit (112), wherein each stage and the paper machine (200) respectively comprises a process water treatment unit (116a, 116b, 216) having the characteristics associated with the process water treatment unit according to any one of claims 29 to 41.

43. The machine according to claim 42, characterized in that The paper machine (200) includes at least one unit selected from a centrifugal classifier (202), a fine classifying device (204), a paper machine-forming section (206), a paper machine-pressing section (208), a waste handling unit (212), a fiber recovery unit (214) and a drying section (210).

44. The machine according to claim 43, characterized in that The paper machine (200) comprises all these units.

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