DE19637909A1 - Scrap wood processing by multistage chemical decomposition, saccharification and fermentation - Google Patents

Abstract

Scrap wood processing comprises: (a) mechanical pretreatment to separate metallic and other inorganic material and to yield wood in the form of chips with a length < 30 mm; (b) chemically decomposing the scrap wood to separate the cellulose component from the lignin: (c1) using or disposing of the lignin; (c2) recovering a wood sugar solution; (d) alcoholic fermentation of the wood sugar solution; (e1) recovering ethanol; (e2) recovering a spent liquor from the distillation of the alcohol; (f) anaerobic fermentation of the spent liquor; (g1) recovering biogas; (g2) recovering the fermentation residue; (h) separating unwanted contaminants from the fermentation residues; (i1) disposing of the unwanted waste material; (i2) conditioning the decontaminated fermentation residues, and (j) utilising the ethanol and biogas as biofuel for the generation of energy e.g. in a block heating plant.

Description

The invention relates to a method for recycling waste wood, in particular chemically treated or coated waste wood from the building and Plant dismantling or from bulky waste sorting, as it is avoiding the Utilization of waste incineration and / or landfill capacities for appropriate waste wood disposal is required.

In connection with the enforcement of the circular economy law and the TA municipal waste is in many places looking for solutions for resource-saving and environmentally compatible disposal of untreated and with interference / damage Waste wood contaminated with substances wanted. Swellings, burns, and slagging processes that more or less perfectly Use the energy content of the waste wood and thereby remove the contaminants released at the Bind exhaust gas and / or ash treatment. This procedure is lacking predominantly in public acceptance. The majority of them are only then applicable with reasonable specific disposal costs if certain Minimum capacities are not undercut. The resulting Plant sizes in turn require larger catchment areas for the waste disposal and, if possible, receptive district heating networks for the usable heat of use. These conditions limit usability such processes for the recycling of waste wood. The crucial problem with this thermal waste treatment is process of deprivation of the plant nutrients contained in the waste wood considered from the economic cycle so that these nutrients through Chemical and / or mineral fertilizers produced using energy need to be replaced.

The environmentally compatible composting of waste wood requires energy-intensive and costly closed rotting technology ahead. Because of the limited technical possibilities for the removal of the compost from disturbance / damage the resulting mass composts increasingly lack a receptive material Market.  

The relatively low content of plant nutrients in mass composts from old wood does not justify a transport of this as Soil improvers can use compost over longer distances.

It is therefore an object of the invention to overcome the disadvantages of the known prior art Overcoming technology and creating a process by means of which environmentally friendly waste wood recycling at locations with regionally limited Catchment area is made possible. The process to be developed should also characterized by the greatest possible environmental compatibility and effective contributions to improve the environmental situation.

The energy content of the waste wood to be treated should also be predominant can be used as the content of plant nutrients, which largely should be preserved for plant nutrition. The invention also lies based on the task that can be obtained in the recycling of waste wood Amounts of energy used even without a sufficient need for useful heat on Location of the process application as comprehensive as possible for the fulfillment of To use energy supply tasks, which is the transfer of at least one Part of the usable energy that can be recovered over long distances transportable energy carriers with a relatively high energy density required.

It is also an object of the invention to provide effective conditions for Elimination of the disturbances entered into the process with the used wood and create pollutants.

Finally, the process for recycling waste wood to be developed should also include Transfer of the plant nutrients to be obtained into larger ones Distances rationally transportable form of fertilizer with high concentration allow for plant nutrients.

According to the invention the object is achieved by the features of claim 1. After that, the waste wood to be recycled is first known in itself Way to one of granular metallic and other inorganic Additions mainly freed fraction mechanically processed. The chip lengths of the mechanically processed waste wood should increase Possibility to be less than 30 mm.  

The mechanically processed waste wood is processed in a manner known per se then a process for separating the cellulose contained therein from Subjected to lignin, the separated lignin being used either to obtain required process energy or environmentally friendly for later use is deposited.

The separated cellulose part becomes during or after the Lignin separation process won a wood sugar solution that one alcoholic fermentation process is fed.

The fermented wood sugar solution is then known by means of Distillery technology distilled, using the biofuel ethanol as an ethanol-water mixture with average ethanol concentrations between 80 and 98% by volume won and stored separately.

In addition, there is a high-protein stillage, which is excellent suitable for biogas production using anaerobic fermentation technology. The sensible warmth of the quantities of ethanol obtained and the amount that accumulates Distillery distillation can be used to recover Use heat and for the fulfillment of heat supply tasks within or outside the individual process steps of the invention Process can be used. The partially cooled stillage is either at an average temperature between 53 and 58 ° C thermophilic or at a average temperature between 34 and 39 ° C using mesophile Fermented anaerobic reactor technology.

This produces biogas with an NH₄ content between 60 and 70 vol% and temporarily stored if necessary.

At the same time, it becomes predominantly odorless and nutritious Fermentation residue with average dry matter contents between 3.5 and 6 mass% won, which is temporarily stored in open or closed containers. The sensible warmth of the digestate is also for the recovery of Usable heat, for example for space heating purposes, can be used.

Then the fermentation residue, preferably in the storage containers, on appropriately freed from contaminants and / or contaminants. That of contaminants depleted digestate is subjected to a quality assessment and the taken from the respective storage container.

The separated contaminants and / or pollutants are used the known disposal routes.

The amount of digestate taken from the respective storage tank in different ways before use as an organic fertilizer conditioned.  

The conditioning consists at least in an effective homogenization of the resulting digestate from various waste wood batches to ensure little fluctuating quality parameter.

However, the conditioning can also consist of using Filtration processes a filtrate suitable as process water for reuse and a solid phase with high dry matter contents and at the same time high kept in plant nutrients. Via press filtration, briquette and / or thermal drying measures or additional mixing with dry additives the dry matter content of the conditioned Fermentation residue can be raised to over 85% by mass. The intended Conditioning also includes graining the Fermentation residue.

While the resulting biogas to generate the required process heat on Location of the process application, preferably by means of Combined heat and power plant technology, is used energetically, the energetic takes place Utilization of the bioethanol obtained with about 1,000 times that of biogas higher energy density, if necessary, at least partially in external force and / or combined heat and power applications.

With this combination of methods known per se, the posed Invention task to be fully accomplished.

The process can be efficient even in comparatively small plant sizes and with significant cost advantages over known process technologies applied and without impermissible air and water pollutant emissions operate.

The required process energy requirement is entirely based on the energy content of the waste wood to be recovered covered, whereby considerable energy surpluses from the regenerative energy source to realize waste wood for external use are. The reduction of the waste to be disposed of to the extent of the The process of eliminating contaminants and pollutants carries the objective waste and environmental requirements in full account.

The majority of the carbon bound in the waste wood to be recycled is converted into biofuels on the effective way of cogeneration can be used energetically with high efficiency and low loss can. The plant nutrients contained in the waste wood remain in particular the phosphor, potassium, magnesium, nitrogen and Calcium compounds completely for plant nutrition and in particular plant-available form.  

This can be a further contribution to the preferred biological and ecological cheap crop production.

During the energetic on-site recycling of the biogas resulting heat quantities to cover the process heat requirement and one possibly limited other at the respective location Usage heat needs can be used, if necessary, the Total amount of bioethanol that can be obtained regardless of location to the alternative Use useful energy without having to rely on a thermal energy requirement Location of the process application to be bound.

Conditioning the fermentation residues enables this if necessary Providing fertilizers, the nutrient concentration of which is several times that in the nutrient concentration contained in the dry wood mass used.

In a special embodiment variant of the method, the mechanical Preparation of the waste wood at least three stages by producing pre-chopped old waste wood with chip lengths of less than 500 mm, followed by a magnet cutting and shredding the metal-depleted waste wood to chip lengths of less than 30 mm, preferably less than 5 mm.

Furthermore, it is advantageously possible for the secondary shredding of the use metal-depleted old wood screen hammer mills.

In a preferred embodiment of the method it is provided that for Digestion of waste wood and selected contaminants, diluted mineral acids, preferably sulfuric acid or hydrochloric acid, and the undigested lignin is separated from the rest of the medium.

However, it is also possible to digest the old wood and select it Interfering substances organic solvents, preferably methanol and / or ethanol use, the separation of the dissolved lignin and the dissolved contaminants simultaneous recovery of the solvent and then the remaining cellulose portion of the waste wood by using mineral acid hydrolyze and saccharify.

The organic solvent used can be removed after the lignin has been separated off and any contaminants contained in the wood digestion or used energetically.  

It can be provided that the lignin obtained in the process is energetically added recycling and / or recycling.

The mineral acid cellulose digestion is known per se in such Process conditions carried out that extensive sales in one fermentable wood sugar solution is achieved. The wood sugar solution obtained is subjected to alcoholic fermentation with the addition of yeasts.

The wood sugar solution obtained is before and / or during the The fermentation process involves flocculation and / or precipitation in the wood sugar Additive causing additives contained solution, whereby expediently the flocked and / or the sedimented contaminants be distilled from the fermented wood sugar solution.

The fermented wood sugar solution can advantageously be one or more stages distill using an alcohol-water mixture with at least 85% by volume Ethanol is obtained.

It is also possible that the stillage obtained during the intermediate storage until the subsequent anaerobic fermentation, the flocculation and / or precipitation of Additives causing interfering substances contained in the stillage and the contaminants are separated from the stillage before anaerobic fermentation.

In a further embodiment of the invention, it has proven to be advantageous Fermentation substrate in addition to the stillage containing other biogenic organic substances Substrates from agricultural, commercial and / or municipal sources, for example animal excrement, waste fats, food residues industry, organic waste or sewage sludge. Besides that, too Forage residues, biotope biomass, set-aside areas and fallow land as well Harvest residues are added to the fermentation substrate as cofermentates.

The anaerobic fermentation is preferred in a partially mixed Anaerobic reactor performed. The fermentation substrate will flocculate and / or cases of interfering substances contained in the fermentation substrate Additives added and the contaminants as part of the separately to be obtained Base sludge discharged from the anaerobic reactor.  

Basically, to remove contaminants from the anaerobic reactor discharged fermentation residue this flocculation in the storage container and / or Cases of additives causing interfering substances contained in the digestate add and remove the contaminants from the storage container as sediment.

Another method variant provides for the separated contaminant-containing ones Summarize substrates, mechanically and / or thermally dewater and before a subsequent material and / or energy recovery and / or Landfill undergo an additional aerobic decomposition process, whereby it to a further reduction in the mass of the contaminant concentrate to be disposed of is coming.

If necessary, the digested residue can be removed mechanically and / or be thermally dewatered, which is why hydrocyclones are preferred, Vacuum drum filters, band filter presses, chamber filter presses, briquetting presses and the like can be used.

For the purpose of improved storage and application capability, the contaminated and at least partially dewatered digestate with porous and / or nutrient-containing additives and mixed by pressing, pelleting and / or agglomerate into a non-baking granular form.

The method according to the invention can advantageously be carried out in one Design variant in such a way that at least subsets of the obtained Ethanol before the energetic utilization in the combined heat and power plant at least be used once as a solvent in wood digestion.

Embodiments

The invention will be explained in more detail below with exemplary embodiments. Show in the attached drawing

FIG. 1 shows the diagram of a variant of the method when using the mineral acid pulping;

Fig. 2 is a diagram of a variant of the method with the use of mineral acids and organic solvents for the pulping;

Fig. 3 is a diagram of a variant of the method with the Störstoffentfrachtung during pulping;

Fig. 4 is a diagram of a variant of the method with the impurity entfrachtung during storage of the wood sugar solution;

Fig. 5 is the diagram of a variant of the method with the impurity entfrachtung during alcoholic fermentation process;

Fig. 6 is the diagram of a variant of the method with the impurity entfrachtung during distillation;

Fig. 7 is the diagram of a variant of the method with the impurity entfrachtung during storage of Ethanolschlempe;

Fig. 8 is the diagram of a variant of the method with the impurity entfrachtung during anaerobic fermentation;

Fig. 9 is a diagram of a variant of the method with the impurity entfrachtung during storage of the fermentation residue;

Fig. 10 shows the scheme of a variant of the method using the impurity entfrachtung in conditioning the fermentation residue.

example 1

Referring to FIG. 1 untreated waste wood is comminuted mm from a demolition site by means of an upstream first shredder to span lengths of up to 300, immediately thereafter past a cross-belt magnetic separator by means of belt conveyors and a given doppelrotorigen Siebhammermühle with a 4 mm gap rust. The hammer mill discharge has a maximum chip length of 13 mm.

The magnetically separated and re-shredded waste wood is temporarily stored and batched to a percolator and there with the addition of diluted Sulfuric acid and superheated steam at pressures of up to 12 bar and temperatures up to 185 ° C during a treatment time of 8 to 15 hours open minded. The resulting acidic wood sugar solution is first the Percolator removed before it discharges the remaining granular Lignin cake comes as a solid fuel for hot steam generation Commitment comes.

The acidic wood sugar solution is made using an aqueous suspension of Calcium hydroxide neutralized in a mixing vessel and then one heat-insulated storage tank supplied, which may be used additional temperatures mean temperatures around 70 ° C are kept.

The by-product from the neutralization of the wood sugar solution is a gypsum that can be used in construction.

The stored wood sugar solution is sent to the storage tank in batches removed and in a spiral heat exchanger to temperatures between 35 and cooled to 40 ° C. The cooled wood sugar solution then arrives together with conventional fermentation yeasts in coolable fermentation reactors, in which one Average temperature of 35 ° for a period between 48 and 72 Hours of alcoholic fermentation is maintained. From the respective Fermentation reactor is the fermented wood sugar solution continuously one Distiller supplied using hot water with a Temperature of about 115 ° C from the cogeneration plant operated in one stage becomes. During the escaping ethanol vapor after condensing and Cool with an ethanol concentration of approximately 85% by volume in a storage tank is stored temporarily, the resulting ethanol stillage gets into one heat-insulated intermediate tank after being in a countercurrent heat exchange some of the sensible heat to the fermented Has released wood sugar solution.

In a non-insulated deep tank, further biogen-organic wet wastes in the form of a mixture of cattle manure with approx. 8% by mass dry matter, slaughterhouse wastes with an average of 22 % by mass dry matter and process water, which is obtained during the conditioning of the digestate, e.g. at temperatures between 15 and stored at 8 ° C. A mixture of one part by mass of ethanol stillage and one part by mass of cattle slurry is introduced in batches into the partially mixed anaerobic reactor, which is operated thermophilically at an average temperature of 55 ° C.

The anaerobic reactor receives the heating energy that may be required from one central hot water tank operated between 60 and 95 ° C, which at the same time serves to cool the engine of the combined heat and power plant.

The biogas generated in the anaerobic reactor contains an average of 65 vol% methane and is stored temporarily in a foil gas storage.

The digestate leaving the anaerobic reactor after an average residence time of 28 days has an average dry matter content of 4 % by mass and is fed into one of three mutually feedable digestate stores.

When feeding and entering the digestate into the respective Fermentation residue stores become commercially available polyelectrolytes added with the help of it in the digestate to sediment the the cattle manure of copper and zinc compounds entered in the system is coming. At regular or irregular intervals, the generated sediments from the respective digestate storage and as Disposed of contaminant concentrate.

After each fermentation residue store has been completely filled, a comprehensive qualitative assessment is carried out with proof of complete freedom from pollutants and with the determination of the content of important plant nutrients, in particular the compounds of phosphorus, potassium, magnesium, nitrogen and calcium. If necessary, filtrate is extracted from the certified fermentation residue with the help of a belt filter press and temporarily stored in an uninsulated process water deep tank for fluidizing dry substance-rich cofermentates. In contrast, the solid phase produced with an average of 35 mass% dry matter content is stacked in a weatherproof roll hall until it is removed as a high-quality biological multi-nutrient fertilizer. On nearby arable and grassland areas, the certified and homogenized, non-thickened digestate is applied directly at the optimal times in terms of agrotechnology, preferably by raining. Several machine sets are installed in the plant-based combined heat and power unit, whereby individual combustion engines are designed for the use of biogas and other combustion engines for the use of ethanol. In the combined heat and power plant, hot water at approx. 130 ° C and hot water at approx. 95 ° C for the other machine cooling are obtained in addition to electrical energy for internal use and for the feed-in from the exhaust gas cooling and stored in separate water tanks to cover the process heat requirement.

Unused quantities of the ethanol obtained are used for the external cogeneration plant.

Example 2

Referring to FIG. 2 untreated waste wood mechanically pre-treated as in Example 1.

Thereafter, ethanol is used in one using the organic solvent Stirring vessel to dissolve the lignin contained in the waste wood, which subsequent recovery of the ethanol from the alcoholic lignin solution is available for energetic or material uses. The lignin the cellulose mass is then removed from the percolator for the purpose of Saccharification supplied, whereupon the process proceeds as in Example 1.

Example 3

Referring to FIG. 3 contaminated waste wood mechanically pre-treated as in Example 1 only with coal tar oil.

Thereafter, the extraction of the Lignins and the contaminant coal tar oil from the crushed wood mass causes.

Thereupon the recovery of the ethanol is not only with the separation of lignin but also with the concentration of the contaminant Coal tar oil associated. While the residual products of the Coal tar oil is properly disposed of the further recycling process of the waste wood as in example 2.

Example 4

According to FIG. 4, waste wood treated with various wood preservatives is mechanically pretreated and chemically digested as in Example 1.

When storing the wood sugar solution obtained, the medium various common flocculants and precipitants added. The sediments generated are transferred to the wood sugar solution before being transferred to withdrawn from the alcoholic fermentation process and disposed of as a contaminant concentrate. The further recycling process of the waste wood takes place as in example 1.  

Example 5

According to Fig. 5 contaminated with pollutants waste wood is treated as in Example 1 mechanically and chemically. To separate the contaminants contained in the alcoholic fermentation process, flocculants and / or precipitants are added to the wood sugar solution, with the aid of which the mechanically unmoved contents of the fermentation container sediment-rich sinking layers, which are removed as regular contaminant concentrate during regular mechanical cleaning of the fermentation container and properly disposed of.

The further recycling process of the waste wood is carried out as in Example 1.

Example 6

Referring to FIG. 6 contaminated with pollutants waste wood is treated analogously to Example 5. However, flocculants and / or precipitants are only added to the fermented wood sugar solution before the distillation process after the alcoholic fermentation process. A first part of the contaminant concentrate is withdrawn from the distillation apparatus parallel to the stillage.

The downstream anaerobic reactor receives due to the lack of use of cofermentates no further pollutant load, so that a second part of the Concentrate of the contaminants entered with the old wood in the storage of Fermentation residues is separated.

Example 7

According to Fig. 7 contaminated with impurities waste wood is treated as in Example 6.

However, a first part of the one with the old wood is entered Pollutant load not during distillation but afterwards Intermediate storage of the ethanol stillages obtained as a concentrate.

Example 8

According to Fig. 8 contaminated with impurities waste wood is treated as in Example 7. The entire load of contaminants is concentrated using the anaerobic reactor as a sedimentation vessel without the need to post-treat the digestate for the purpose of removing contaminants during the anaerobic fermentation process.

If necessary, the contaminants are the anaerobic reactor or the Anaerobic reactor directly connected basic sludge sedimentation tank taken as a contaminant concentrate and thus from the recovery process diverted.

Example 9

According to FIG. 9, waste wood contaminated with impurities is treated as in Example 8. The entire remaining contaminant load is only removed from the digestate when it is stored in the digestate container and is extracted there as a properly disposable contaminant concentrate.

Example 10

Referring to FIG. 10 contaminated with impurities waste wood is treated as in Example 9. In addition to the discharge of impurities when storing the digestate in the digestate container, another contaminant discharge takes place in connection with the process of dewatering the digestate.

Claims (24)

1. Process for recycling waste wood, characterized by the process steps

• a) mechanical processing of the waste wood into a fraction with chip lengths of less than 30 mm, which is largely freed from granular metallic and other inorganic admixtures;
• b) separating the cellulose content in the waste wood from the lignin;
• c1) recycling or depositing the lignin;
• c2) obtaining a wood sugar solution;
• d) alcoholic fermentation of the wood sugar solution;
• e1) obtaining ethanol;
• e2) obtaining a stillage;
• f) anaerobic fermentation of the stillage;
• g1) extraction of biogas;
• g2) recovery of digestate;
• h) removal of impurities from the digestate;
• i1) disposal of the contaminants;
• i2) conditioning of the digested residue removed from the contaminants;
• j) energetic utilization of the biofuels ethanol and biogas using cogeneration technology;
• 2. The method according to claim 1, characterized in that the mechanical processing of the waste wood at least three stages by producing pre-shredded waste wood with chip lengths of less than 500 mm, subsequent magnetic cutting and shredding of the metal-depleted waste wood to chip lengths of less than 30 mm, preferably to less than 5 mm.

3. The method according to claim 1 and 2, characterized in that that for the shredding of the metal-depleted waste wood Screen hammer mills can be used. 4. The method according to claims 1 to 3, characterized in net, that diluted to digest the old wood and selected contaminants Mineral acids, preferably sulfuric acid or hydrochloric acid, are used and the undigested lignin from the rest of the medium is separated. 5. The method according to claims 1 to 4, characterized in net, that to digest the old wood and selected contaminants organic Solvents, preferably methanol and / or ethanol, are used and then the remaining cellulose portion of the waste wood Use of mineral acid is hydrolyzed. 6. The method according to claim 5, characterized in that the organic solvent used from lignin and dissolved contaminants is separated before it enters the wood digestion is recycled or used energetically.   7. The method according to claims 1 to 6, characterized in net, that the lignin obtained is used energetically. 8. The method according to claims 1 to 7, characterized in net, that with mineral acid digestion cellulose a substantial turnover for Wood sugar solution is made. 9. The method according to claims 1 to 8, characterized in net, that the wood sugar solution obtained after the addition of yeasts one subject to alcoholic fermentation. 10. The method according to claims 1 to 9, characterized in net, that the wood sugar solution obtained before and / or during the Fermentation process the flocculation and / or felling in the Additives that cause contaminants contained in wood sugar solution added and the contaminants before distilling from the fermented Wood sugar solution to be separated. 11. The method according to claims 1 to 10, characterized draws, that the fermented wood sugar solution is distilled in one or more stages and an alcohol-water mixture with at least 85% by volume of ethanol is won.   12. The method according to claims 1 to 11, characterized draws, that the medium to be treated is flocculated and / or precipitated contained chemical disruptors and / or pollutants Additives are added. 13. The method according to claim 12, characterized in net, that the additives are added to the wood sugar solution and that accumulating contaminant concentrate in the storage container for the wood sugar solution is taken as a sediment. 14. The method according to claim 12, characterized in net, that the additives of the wood sugar solution during the alcoholic Fermentation are added and the resulting contaminant concentrate Fermentation reactor is removed as sediment. 15. The method according to claim 12, characterized in net, that the additives of the fermented wood sugar solution before Distillation process are added and the resulting Contaminant concentrate is separated from the distillation residue. 16. The method according to claim 12, characterized in net, that the additives of the resulting stillage during the Intermediate storage until the subsequent anaerobic fermentation are and the resulting contaminant concentrate the storage container for the Stillage is removed as sediment.   17. The method according to claim 12, characterized in net, that the additives are added to the anaerobic reactor and that Contaminant concentrate the resulting sludge in a separate Treatment stage is withdrawn. 18. The method according to claim 12, characterized in net, that the additives are added to the digestate and that Contaminant concentrate taken from the fermentation residue container as sediment becomes. 19. The method according to claim 12, characterized in net, that the additives are added to the digestate when conditioning and the contaminant concentrate to the filtrate as Sediment is removed. 20. The method according to claims 1 to 19, characterized draws, that the fermentation substrate in addition to the stillage, other biogenic organic substances containing substrates from agricultural, commercial and / or municipal sources, for example animal excrement, used fats, Residues from the food industry, organic waste or sewage sludge, be added. 21. The method according to claims 1 to 20, characterized draws, that anaerobic fermentation takes place in a partially mixed anaerobic Reactor with separate sludge discharge is carried out.   22. The method according to claims 1 to 21, characterized draws, that the deposited substrates containing interfering substances are combined, mechanically and / or thermally dewatered and before a subsequent one material and / or energy recovery and / or landfill one aerobic rotting process. 23. The method according to claims 1 to 22, characterized draws, that the digested residues are mechanically and / or thermally removed is drained. 24. The method according to claims 1 to 23, characterized draws, that the contaminated and at least partially dewatered digestate mixed with porous and / or nutrient-containing additives and through Pressing, pelleting and / or agglomerating into a non-baking granular Form is transferred. 25. The method according to claims 1 to 24, characterized draws, that at least aliquots of the ethanol obtained before energetic utilization in the cogeneration plant at least once as Solvents are used when digesting wood.