RU2819018C2 - Method and device for regenerating cellulose solvent from spinning process - Google Patents

Abstract

FIELD: paper.

SUBSTANCE: invention relates to a method and apparatus for regenerating cellulose solvent in a method of producing moulded cellulose articles. Proposed method is implemented in several stages. First, solid moulded cellulose articles are continuously or intermittently produced, comprising obtaining a cellulose solution from dissolved cellulose and a cellulose solvent, moulding the cellulose solution into the desired geometric shape, hardening the moulded cellulose solution into the moulded cellulose article in a coagulation liquid, releasing or extracting a solvent from a moulded cellulose article using a non-solvent. Said process involves accumulation of moulded articles wastes. At the second stage, the moulded articles wastes are collected, which are then subjected to grinding, besides, the wastes can contain a solvent or a non-solvent. At the end of the process, the solvent is extracted from the crushed wastes of the moulded articles. Solid solvent-containing cellulose wastes, which are accumulated before moulding and during moulding, are mixed and ground together, or the solvent from the coagulation liquid from the first step and the extracted solvent from the last moulding step are concentrated together.

EFFECT: proposed in the invention approach enables to efficiently extract the solvent used in the moulding process.

16 cl, 9 dwg, 7 tbl, 7 ex

Description

Field of technology to which the invention relates

The present invention relates to a method for recovering cellulose solvent in a spinning process.

State of the art

Various spinning processes are known for cellulosic materials, in particular the rayon process and the lyocell process. Lyocell is the generic name given by BISFA (Bureau International for Standardization of Synthetic Fibers) for cellulosic fibers that are derived from cellulose without derivatization. While the viscose process relies on an alkaline derivative of cellulose to convert it into a soluble spinnable form, the lyocell process uses cellulose solvents that do not modify it (see Zhang et al., BioResources 13(2), 2018: 4577 -4592 with an overview of the differences between the above processes). In addition, the lyocell process requires energy-intensive solvent regeneration, which is the main reason for the high costs and low efficiency of the process (Perepelkin, Fiber Chemistry, 39(2), 2007: 163-172). As an example, US Pat. No. 8,932,471 proposes a three-stage evaporation process to evaporate water from a solvent-containing liquid appearing during the spinning process to concentrate the solvent (N-methylmorpholine-N-oxide; abbreviated as NMMO or NMMNO) for so that the resulting mixture can be used again to dissolve cellulose. This evaporation process is quite energy intensive.

An overview of the lyocell process can be found in Singha, International Journal of Materials Engineering 2012, 2(3): 10-16. Briefly, this process involves the steps of dissolving cellulose from cellulosic pulp, such as wood pulp. The solvent used may be a mixture of NMMO-water, in which the proportion of NMMO should be 76-78% for dissolution at 70°C-90°C. The resulting cellulose solution is filtered, spun using a spin bath extrusion process (a bath filled with a NMMO-water mixture with a proportion of NMMO less than the solubility limit for cellulose), the coagulated cellulose solution is washed, dried and cut into fibers of the desired length. The solvent that accumulates during the spinning and washing processes is purified (filtration, ion exchange) and, by evaporation of most of the water, brought to such a NMMO concentration that the mixture is again suitable for dissolving cellulose. A portion of fresh NMMO is added to replace NMMO that is not being regenerated.

Summary of the Invention

The problem with known methods is that solvent recovery is incomplete. An additional problem is that in the lyocell process, there are many devices in which solvent can be lost.

Thus, the aim of the invention is to develop an improved process with more efficient recovery of cellulose solvent. In particular, recycling of the aqueous cellulose solvent must be achieved in order to improve the economic efficiency of the process for producing cellulose fibers.

The invention relates to a method for extracting or regenerating cellulose solvent in the process of producing molded products from cellulose, which includes the stages:

A) continuous or batch production of solid molded cellulose products from a cellulose solution, which includes the steps of:

i) preparing a cellulose solution from dissolved cellulose and a cellulose solvent and preferably an additional non-solvent, especially preferably water,

ii) molding the cellulose solution into the desired geometric shape,

iii) solidifying the molded cellulose solution into a molded cellulose product in a coagulation liquid,

iv) releasing or extracting solvent from the molded pulp product,

wherein during a continuous or batch process waste moldings from the cellulose solution accumulate in an undesired form and not necessarily in a desired form,

B) collecting waste moldings in undesired form and not necessarily in desirable form,

C) grinding waste molded products from stage B),

D) solvent extraction from crushed waste moldings.

In addition, the invention relates to a device for carrying out this method. By way of example, the invention relates to a device for regenerating a cellulose solvent in a method for producing molded cellulose products, which includes a spinning unit with an extruder, a container for a coagulation liquid that is located downstream of the extruder, and a device for withdrawing the solidified molded cellulose products from the container. , a container for collecting hardened molded pulp products and a crusher for hardened molded pulp products. In addition, the invention relates to the use of a device for collecting and crushing hardened molded cellulose products and for carrying out the method according to the invention.

All aspects of the apparatus and method will be described together in more detail below; in this regard, the specified details always refer to both aspects: the description of the method or stages of the method refers to the device in the context of the parts of the device for the specified method or stages; the description of the device also refers to the means for carrying out the method.

Description of drawings

In fig. 1 shows the location where solvent-containing waste streams in a lyocell process can accumulate.

In fig. Figure 2 shows individual objects in mixed waste after the pre-grinding stage. Dimensions are given in cm.

In fig. Figure 3 shows cellulose waste after solvent extraction and after water removal (dewatering).

In fig. Figure 4 shows a simplified block diagram of the solvent recycling method.

Fig. 5 illustrates the total NMMNO balance for the lyocell process plant.

In fig. 6 shows a crusher.

In fig. Figure 7 shows the rotor with the cutting elements of the crusher.

In fig. 8 shows a rotor with helical cutting elements (a), a rotor with serrated cutting edges and diametrically spaced serrated opposing cutting edges (b), and a side view of the position of the rotor relative to the opposing cutting edge in the crusher (b).

In fig. 9 shows sieves for the crusher.

Detailed Description of the Invention

Cellulose solvents are relatively expensive and therefore must be intensively reused in the closed loop process. Although the lyocell process has been used successfully for many years to produce cellulosic products, a high recovery rate of >99.5% is required for it to meet economic and environmental requirements. An additional increase in solvent recovery, even to a small extent compared to the normal level, would be truly beneficial.

According to the method according to the invention, the cellulose solvent is collected and regenerated. In a molded pulp product manufacturing process such as the lyocell manufacturing process, waste that still contains solvent is accumulated at various stages. This waste can be liquid or solid (molded product waste). Solvent liquids can be extracted from molding waste, which, together with direct liquid waste from the lyocell process (or the like), can be processed to collect or recover solvent for reuse in the process.

Typically, molded products are produced continuously as well as periodically. In particular, when a continuous process is started, a lot of molding waste accumulates, which is collected and processed according to the invention. A method for producing solid molded cellulose products from a cellulose solution, such as the lyocell method, includes the steps of:

i) providing a cellulose solution of dissolved cellulose and a cellulose solvent and preferably a non-solvent, especially preferably water,

ii) molding the cellulose solution into the desired geometric shape,

iii) solidifying the molded cellulose solution into molded cellulose products in a coagulation liquid,

iv) releasing or extracting solvent from the molded pulp products, for example using a non-solvent, preferably water or an aqueous medium, and optionally washing the molded pulp products.

These stages are essential. Additional details can be found in the literature cited above and the following detailed description. As an example, typically the cellulose solution is molded by extrusion from an extruder and drawn into the air gap between the extruder and the coagulating liquid. Molding or extrusion is also known as “spinning,” especially when the fibers or filaments are to be produced as molded articles. Moreover, the present invention is not limited to fibers or filaments, and all aspects of the invention that are described for these molded articles are also applicable to other molded articles such as films, nonwovens, or hollow tubes.

These described molded articles and all pre-products and intermediate products for said molded articles corresponding to the method will be described as desired geometric shapes in the method according to the invention.

Any molded articles that do not conform to the desired geometric shape and which cannot be converted into the desired geometric shape in the process for producing said molded cellulosic articles will be described as undesirable geometric shapes in the process of the invention.

The type of molded product is often determined by the shape and type of extrusion nozzles and their openings or arrangement. As an example, the desired shape may be threads that have a uniform thickness, for example, within a tolerance range of ±10% or less.

The recirculation of the solvent according to the invention in later stages is independent of the nozzles. The molded cellulose solution can be supplied from the coagulation liquid using a recovery device, which is described, for example, in WO 2013/030400 A1. In this regard, the recovered coagulated cellulose solution (molded products) can be deflected into a coagulation liquid container, as shown, for example, in EP 18191628.9.

In particular, during the “start-up period” or at the “beginning” of the process, an increasing amount of molding waste accumulates, that is, a solidified or coagulated solution of cellulose in an undesirable form. In addition, during continuous operation, waste of this type can always accumulate, leading to interruption of the process to remove the (desired) molded pulp products. Waste moldings (having an undesirable shape) are typically collected, for example, in a container such as a basket, then crushed, for example, in a crusher. The solvent can then be extracted from the shredded waste moldings. Extraction may be accomplished by washing or mechanical crushing or agitation, preferably by combining washing with crushing or agitation of the crushed waste moldings. The crushing or mixing can be carried out, for example, in a screw, which, at the same time, can also crush the waste molded products.

For these steps, the invention also provides a cellulose solvent recovery device in a process for producing molded cellulose products. The apparatus may include a spinning solution receiving unit, a spinning solution filtration unit, a spinning unit with an extruder, extrusion pumps, a heat exchanger, extrusion tools, dies, a coagulation liquid container that is located downstream of a space below the extruder, or extrusion means, preferably a die, a recovery device, a cutting device, a container for collecting hardened molded pulp products, a crusher for hardened molded pulp products, a mechanical separation unit for separating solids into liquids, an ion exchange unit, a unit for concentrating an aqueous cellulose solvent, or combinations thereof. Preferably, the apparatus includes a spinning unit with an extruder, a coagulation liquid container that is located downstream of a space below the extruder, and a device for removing the hardened molded pulp products from the container. These details of the device will be explained in more detail below.

Preferably, a container is provided for collecting the hardened molded pulp products and a crusher for crushing the hardened molded pulp products. In addition, the device may have an extractor for extracting solvent from the waste moldings. Likewise, a washing unit may be provided for molded articles (as well as for waste, but especially for desired molded articles).

Typically, cellulose solutions intended for extraction are initially prepared from a suspension in a mixer, for example as described in WO 2009/098073 A1, WO 2011/124387 A1 or US Patent No. 5,948,905. Typically, cellulose is obtained from wood or wood pulp, but other sources are possible.

The cellulose is crushed and then mixed with a solvent and water. After continuous production of the suspension, part of the water is removed from the suspension under vacuum and at elevated temperature. Once the water content has been sufficiently reduced, the cellulose is dissolved in a solvent to form a solution that is applied to a spinning process (also known as a spinning solution or extrusion solution), which is filtered and then molded, such as compressed using an extruder (e.g. through spinnerets) during fiber production. The molded articles thus formed are then deposited in a bath with a coagulating liquid (usually water or water with a solvent at a concentration less than that required for dissolution). According to the invention, non-derivatized cellulose (lyocell) is preferably used, that is, it is not viscose. Even when producing an extrusion solution, waste may be generated, which is collected, for example, in filters. The filter is described, for example, in document WO 2014/085836 A1. This type of waste can be solid (cellulose suspension or solidified solution) or liquid (for example, cellulose solution obtained from filter washing).

A solvent (also called a “solubilizing agent” or “cellulose solvent”) is a reagent for dissolving cellulose. Typically, in this regard, elevated temperatures are used, for example 70°C or higher, especially 75°C or higher, or 78°C or higher. In most cases, the solvent is mixed with a non-solvent, that is, a substance that cannot dissolve cellulose, after which the mixture is still suitable for dissolving cellulose. In this regard, among other things, higher proportions of solvent in the mixture are required, for example, 60% (% by weight) or higher, depending on the solvent, these ratios can vary, and a person skilled in the art can easily determine the proportion experimentally by dilution.

The extrusion medium for the molding process is used as a cellulose solution in the method according to the invention. The concentration of cellulose is selected so that it is normal for the lyocell method. In such a context, the concentration of cellulose in the cellulose solution (obtained in step i)) may be from 4% to 23%, preferably from 6% to 20%, especially from 8% to 18%, or from 10% to 16% (all proportions are indicated in % by weight).

Preferably, the solvent is a tertiary amine oxide (amine N-oxide), particularly preferably N-methylmorpholine N-oxide.

Alternatively or additionally, the solvent may be ionic. Examples of ionic solvents of this type are described in documents WO 03/029329; WO 2006/000197 A1; Parviainen et al., RSC Adv., 2015, 5, 69728-69737; Liu et al., Green Chem. 2017, DOI: 10.1039/c7gc02880f; Hauru et al., Zellulose (2014) 21:4471–4481; Fernández et al., J Membra Sci Technol 2011, p. 4; etc. and preferably contain organic cations, such as ammonium, pyrimidium or imidazolium cations, preferably 1,3-dialkylimidazolium salts such as halides. Here too, water is predominantly used as a non-solvent for cellulose. Particular preference is given to using a solution of cellulose and butyl-3-methylimidazolium (BMIM), for example with chloride as a counterion (BMIMCl), or 1-ethyl-3-methylimidazolium (also preferably in the form of chloride, acetate or diethyl phosphate) or 1- hexyl-3-methylimidazolium or 1-hexyl-1-methylpyrrolidinium (preferably with bis(trifluoromethylsulfonyl)amide anion), and water. Other ionic solvents are 1,5-diazabicyclo[4.3.0]non-5-enium, preferably in the form of acetate; 1-ethyl-3-methylimidazolium acetate, 1,3-dimethylimidazolium acetate, 1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium diethyl phosphate, 1-methyl-3-dimethylphosphate methylimidazolium, 1-ethyl-3-methylimidazolium formate, 1-ethyl-3-methylimidazolium octanoate, 1,3-diethyl imidazolium acetate and 1-ethyl-3-methylimidazolium propionate.

Liquids or solids with solvents accumulate at various stages of the lyocell process (or the like). The solvent must be collected, extracted and/or regenerated from them so that the solvent can be used again to dissolve the cellulose in the lyocell process. Therefore, it is not necessary that the solvent be isolated as a pure substance. A suitable mixture of solvent and non-solvent is suitable for dissolving cellulose. Concentration of this type of solvent can also be considered as part of the solvent recovery process. The purpose of the method is to extract the solvent as much as possible while eliminating losses. In particular, the goal is to retain more than 99%, especially more than 99.5% (% by weight) of the solvent in the process.

In particular, solvent-containing substances are (see FIG. 1):

(1) cellulosic suspensions, for example formed from residues during the production of cellulose.

(2) cellulose solutions, for example from filters,

(3) coagulated cellulose solutions, for example waste moldings in undesirable form, which especially accumulate during process start-up,

(4) molded cellulosic products in continuous form, for example after molding, which are washed in order to extract solvent from them,

(5) molded cellulosic products in cut form, for example after molding and cutting, which are washed in order to extract solvent from them,

(6) solvent-containing wastewater that accumulates at various stages, for example, as coagulation liquid that flows from the coagulation liquid tank with molded products, spray liquids, rinsing liquids (when washing the desired moldings), extraction liquids after processing solid waste. This type of loss occurs, for example, when it runs off molded products. In order to prevent or minimize losses, a reservoir may be provided to accumulate said losses. This may also be implemented as a system of channels separated from waste containing non-solvent, limited both to the washing area and to the entire process area where the solvent is used.

All molded pulp products referred to in paragraphs (1) - (5) may be in either a desired form (eg, as regular molds during fiber production) or in an undesired form (eg, as waste). The distinction between product and waste can be made arbitrarily, depending on the quality criteria of the desired product (generally, a sticky mass that interrupts the process is always considered waste) or established according to the economics of the process (trimming). The method according to the invention is advantageously characterized by the following features:

Preferably, the solid waste is collected from (1) cellulose slurries, (2) cellulose solutions, (3) coagulated cellulose solutions, e.g. waste moldings in undesired form, (4) molded cellulose products in continuous form - if available as waste, (5) molded cellulose products in cut form - if available as waste, for the purpose of further combined processing. While there are no solids being discarded at the point. (4) and (5), extraction and/or washing liquids obtained during processing can be collected.

Optionally, the stickiness of, for example, the cellulose suspension (1) can be reduced by treatment with a non-solvent, for example water, before further processing (in particular, grinding).

Solid waste treatment can result in liquid waste, and liquid waste treatment can result in solid waste. In this regard, the solvent is washed, extracted or leached from the solid waste. The solvent-containing liquids that result from this (washing or extraction liquids) are sent for regeneration as liquid waste. Liquid waste with a sufficiently high cellulose content can be precipitated (for example from (2), for example as described in CN 104711706), and thus leads to solvent-containing solid waste, which in turn enters the production stage solid material according to the invention in order to wash out or extract solvent from it (which in turn leads to liquid waste). The solid can only be removed when sufficient or almost all of the solvent has been removed. This also applies to solvent-free liquids or fluids (eg, steam from an evaporation process to concentrate the solvent in the remaining liquid), which may be removed or otherwise used in the lyocell process.

Solvent-containing solid waste can come in a variety of forms. If they are precipitated from cellulose suspensions or solutions prior to molding (eg in a filter), the cellulose can be separated from these media (by mixing with non-solvents and/or by cooling). This usually results in fine fibrous waste. A sticky mass may form during molding, especially when starting or operating a continuous extrusion process. Preferably, shaping the cellulose solution into desired geometric shapes is accomplished by spinning into strands or threads. In this regard, molded product waste may be in the undesirable form of a clumped mass of strands or threads.

Other solid waste consists of cut waste from molded products, even those that originally had the desired shape.

According to the invention, it is possible to mix different types of molding waste from said different process steps. Preferably, solid solvent-containing waste from coagulated cellulose solutions or slurries before molding is mixed with waste moldings after molding, for example, coagulated masses or actual molded products in the desired shape. Mixing means that the grinding efficiency is increased, that is, the solid waste intended for grinding is easier to handle and thus reaches the desired crushed size more quickly, or there is less pause or clumping in the crusher. In particular, molded products in the desired shape, such as cellulose fibers, are often difficult to grind. The concentration of these fractions is reduced by mixing with other solid waste, which can then facilitate the processing of the mixed waste in the crusher. The composition of a mixture of two parts of waste molded cellulose products (depending on the form, preferably with waste in the desired form) with one or more parts of solid waste before molding, that is, which accumulates before molding (from cellulose suspensions or cellulose solutions), has a positive effect thanks to more efficient grinding. Mixtures of one part molded pulp product waste and two or more parts solid waste that accumulate prior to molding are particularly preferred and have been shown to be particularly effective. The collected solid waste is processed using a grinding device to reduce the size of the granules. In this regard, the collected solid waste can be processed separately (for example, after separation or screening), or the collected solid waste can be processed in combination. In this regard, the solid waste processed in combination may specifically be processed as a mixture, or the solid waste processed in combination may specifically be processed sequentially.

Grinding can be carried out in a single stage or in multiple stages (using pre-crusher and/or post-crusher).

Preferably, the grinding in step C) is carried out using a cutting mill. According to the invention, it has been shown that the cutter mill is particularly suitable for grinding waste moldings, as well as other solid wastes containing solvent, without consuming excess frictional energy so that the solid medium is only slightly heated. At the same time, the concentrated mechanical force acting through the cutting element is strong enough to crush even hard and fibrous waste.

Preferably, the cutting element acts against an opposing cutting element, such as a stator or an additional cutting element, so that the waste is cut between the elements. Grinding by cutting is preferred. It is particularly preferred that the cutting mill (crusher) has a rotor with projecting cutting elements, as well as a screen with holes where the cutting elements collide with the holes of the screen. The screen acts as a counter-cutting piece with counter-cutting edges, and as the cutting elements pass inside the holes, the solid waste contained in them is crushed and can be pushed out through the holes. The holes may be in the stator or, alternatively, in an additional rotor shaft. Other sieves may be used to control the granule size of the crushed material. As an example, the screen may regulate the discharge of material. Only the material that passes through the sieve holes is transported to the outside; larger particles of material remain within the cutting elements and are further crushed. According to the invention, it has been demonstrated that using a sieve of the type indicated, a particularly effective reduction of cellulosic waste from the lyocell process is possible.

A crusher having a rotor with one or more projecting cutting elements and one or more counter-cutting edges is particularly preferred, where the cutting elements slide behind the counter-cutting edges so that molded products or molding waste between the cutting elements and counter-cutting edges are crushed . Preferably, the cutting edges and/or the counter-cutting edge are serrated. The tips of the teeth are preferably formed by edges at an angle of from 160° to 30°. Preferably, a sieve is provided adjacent and/or below the rotor in order to control the particle size of the cut material. More preferably, the rotor is provided with raised friction elements or one or more cutting elements and one or more counter-cutting edges, where the cutting elements slide behind the counter-cutting edges so that the molded articles or molded waste are crushed between the cutting elements and the counter-cutting ones. edges. Molded products or molded product waste may be fed continuously or intermittently to the cutting elements for grinding. Particularly preferably, the cutting elements have a triangular or serrated shape. More preferably, the friction or cutting elements are mounted on the rotor in such a way that they are deflected from each other.

These preferred elements, and in particular their combination, result in a highly convenient method. An example of this type of crusher is the Antares cutting machine from Lindner Recyclingtech GmbH, which was originally developed for crushing wood. Surprisingly, this machine was useful for optimized grinding of pasty solid waste from the lyocell process.

Preferably, the molded articles and other solid waste (even pre-molded waste) are crushed to a size (maximum particle size) of 20 mm or less, preferably 15 mm or less. Typical sizes are from 10 mm to 20 mm.

Optionally, a downstream crusher may be used that crushes the molded articles and other solid waste to a size of 10 to 15 mm or less, preferably 10 mm or less. The post-crusher can be configured in a similar or identical manner to the pre-crusher except for the crushing dimensions.

Preferably, during the grinding step, water or an aqueous medium is supplied to the crusher. In this regard, the extraction or separation of the cellulose solvent from the molded products can also occur in a crusher.

Additional advantageous features of the crusher are discussed below in part (b), “Comminution of Waste Materials,” particularly with reference to FIG. 6-9. The crushed solids are introduced directly into the extraction vessel (eg tank). Alternatively, ground solids can be stored temporarily. Preferably, all crushed solids, regardless of their original location, that is, points (1)-(5), enter together into an extraction vessel (eg, a tank).

Preferably, the extraction is carried out with stirring, for example using a stirrer. The mixture of solid and liquid is transported by a pump to remove the water.

Water removal and extraction can be carried out in combination, in stages. This is done through one or more extraction and water removal steps. Preferably, water is used for extraction. Preferably, during extraction, the desired non-solvent, such as water, is supplied countercurrently to the solid-liquid mixture to be processed.

Preferably, all liquid waste is collected for the purpose of subsequent treatment in the method according to the invention.

Solvent-containing liquid accumulates at various stages and can be mixed for processing. Preferably, the coagulation liquid is separated from the molded pulp products from step A) iii) after transport from the coagulation liquid container, for example, by draining or pressing the molded pulp products, and collected together with the extracted solvent from step D).

In addition, the device according to the invention has a channel (for example, an open drain trough or a closed pipe) at the bottom for accumulating and transporting the coagulation liquid removed from the spinning unit, which enters a liquid liquid collection tank or an evaporator for liquids containing cellulose solvent. Said channel is preferably covered with a cover that can be walked on and moved, but which is permeable to liquids, thus minimizing the contact of the lyocell operator with the liquid containing the solvent. An example of this type of cover is a grille.

According to the method according to the invention, the liquid waste is further treated so that the solvent it contains can be recovered to its original purity, or at least to a purity sufficient for the lyocell process, and thus can be returned to the process.

Preferably, the liquid waste is collected in a tank so that it can be treated in combination with this method. The goal is to recycle the solvent into the lyocell process as much as possible.

In the first stage, the liquid waste can be filtered to remove solid residue (US 2011/0226427 A1) and/or pumped for ion exchange to remove harmful ions, such as iron or copper ions (see, for example, Han et al., Journal of Textile Research 29(6), 2008, 15-19). NMMO degradation products such as NMM (N-methylmorpholine) can be decolorized by oxidation or regenerated as NMMO. A suitable oxidation process is described in WO 2018/115443 A1.

Effective preparation of solvent-containing liquids is obtained according to the invention by a combination of additional processing (eg purification, in particular solvent concentration). Preferably, according to the invention, the concentration of the solvent is carried out by washing the solvent-containing liquids from step A) iv) and the solvent-containing extraction liquids from step D) - that is, after washing, separation or extraction. In addition, the device according to the invention may include evaporators, micro- or ultra-filtration processes, membrane or osmotic separation methods and/or crystallization apparatus. In this regard, these methods can also be used in combination or sequentially. In this regard, the method according to the invention also allows for selective use, in which a certain aqueous waste stream containing a solvent is pre-treated in the process and thereafter fed into the mixture into a subsequent concentration step.

Preferably, the extracted solvent or aqueous solvent mixture is treated in a mechanical separation process before concentration. Mechanical separation allows for the separation of other phases, such as the solid phase. An example of this type of separation process is filtration or adsorption.

The mechanical separation process can be carried out as static and/or dynamic filtration. In static filtration, the phase to be separated (retentate) is retained statically, for example in a filter, or fixed or immobilized on an adsorbent. The preferred methods of static filtration are pressure filtration (high pressure), vacuum filtration, surface filtration, layer filtration, in particular deep filtration, for example with sand filters.

The mechanical separation process can also or alternatively be implemented as dynamic filtration. With dynamic filtration, there are two mobile phases that are separated, for example, by a membrane. An example is membrane filtration, preferably as cross-flow filtration or tangential flow filtration. In this regard, both mobile phases are usually fluids, in particular liquids. Membrane technology for processing solvents, in particular NNMO and/or ionic liquids, is described, for example, in the article “Regeneration of ionic liquids from wastewater using nanofiltration” (Journal of Membrane Science and Technology 2011, pp. 4-8; DOI:10.4172 /2155-9589.p4-001 and in the document EP 0 448 924 (both incorporated by reference). This technology is preferably used in the invention.

The preferred filtration method is preferably dynamic filtration, microfiltration, ultrafiltration, nanofiltration or reverse osmosis. Typical pore size for a filter or membrane in this filtration method is 0.5-0.1 µm for microfiltration, 0.1-0.01 µm for ultrafiltration, 0.01-0.001 µm for nanofiltration, and 1-0.1 nm for reverse osmosis.

The phases to be separated can also be isolated without filtration, for example by sedimentation or centrifugation, in particular to remove solids. Accordingly, preferably in the process according to the invention, the separated or extracted solvent or aqueous solvent mixture is introduced into a precipitation tank prior to enrichment. More preferably, the separated or extracted solvent or aqueous solvent mixture is fed to a centrifuge and/or separator until concentrated. Moreover, the isolated or extracted solvent or aqueous solvent mixture can be fed into a filter press before being concentrated. Additionally or alternatively, the separated or extracted solvent or aqueous solvent mixture may be fed to a centrifuge and/or separator prior to concentration to further separate contaminant material such as solids therein. Preferably, a combination of sedimentation tank, filter press, centrifuge and/or separator is used.

Particularly preferably, the isolated or extracted solvent or aqueous solvent mixture is processed using a rotary microfilter until concentrated.

In all embodiments, the extraction and/or filtration steps can be performed batchwise and/or continuously.

Subsequently, the solvent or aqueous solvent mixture is preferably subjected to ion exchange, for example using an ion exchanger. In this regard, for example, after a (batch and/or continuous) extraction and/or filtration step, the solvent or aqueous solvent mixture enters the cation and/or anion exchange unit.

These concentration steps may be carried out to achieve dissolution of a cellulosic solvent that is suitable for dissolving or suspending cellulose. Preferably, a concentration of at least 50% (% by weight), particularly preferably 50% or higher, or 70% or higher, of the solvent in the solution is obtained, in particular when using N-methylmorpholine-N-oxide as the solvent. Dissolution or suspension processes for which a concentrated solution is suitable are early stages of the lyocell process as described above. Briefly, cellulose is suspended in a mixture of solvent and non-solvent and brought into solution by removing the non-solvent. The amount of common solvents in this mixture is 50% or higher, for example 58% to 78% (all % by weight). For example, a practical cellulose solution may contain 5-16% cellulose, 55-80% solvent, in particular NMMO, and the balance, preferably 18-30%, non-solvent, in particular water (all % by weight). Therefore, minute traces of components such as salts are not taken into account.

Concentration preferably involves evaporation of the non-solvent, which is preferably water. Evaporation is a preferred implementation in the case of amine oxides, in particular NMMO, as solvent. Additionally or alternatively, solvent concentration may involve crystallization. This is particularly advantageous when using ionic solvents. The device according to the invention may contain a concentration device, in particular an evaporator to evaporate the non-solvent from liquids containing cellulose solvent (US 8 932 471; US 2011/0226427 A1), or a crystallization unit (Liu et al., see above).

Thus, the device according to the invention can be used for the preparation of suspensions of cellulose in aqueous solvents and/or for the preparation of solutions of cellulose in aqueous solvents.

Furthermore, the invention relates to a cellulose product which is obtained by the process according to the invention, in particular by using a purified, concentrated aqueous solvent. The cellulose product is obtained by extruding a cellulose solution (molding as described in the invention).

Preferably, the cellulose product is a continuous cellulose filament product or a cellulose staple fiber product or a cellulose film product. Before or after concentration, the solvent-containing liquid can be purified by ion exchange. For this purpose, a cation and/or anion exchanger is used, in particular to remove iron and copper ions from the liquid.

Solvent-containing liquids accumulate at various stages and can be mixed for processing. Preferably, the coagulation liquid that flows or is squeezed out of the molded pulp products from step A) iii) after being transported from the coagulation liquid container is collected with the extracted solvent from step D) and/or is further processed, in particular for the purpose of concentration. The coagulation liquid is kept in the container during a continuous process. A collection tank for accumulating cellulose solvent flowing out of the container as a result of transporting the molded cellulose products outside may be combined with the said container. A pipeline can go from this tank to a common storage tank. In the lyocell process, a cellulose solution is formed, for example by extrusion or spinning, and introduced into a coagulation liquid. This causes a solvent exchange between the molded cellulose solution and the coagulation liquid. In such a context, the molded articles formed in this manner are in turn removed from the coagulation liquid, whereby various losses of the solvent-containing coagulation liquid may occur. These losses are eliminated, for example, by accumulating liquid that flows out. As an example, after removal from the container containing the coagulation liquid, a retrieval unit may be provided in which the molded articles are deflected around one or more rollers and removed. Solvent-containing liquid that is drained may collect here.

Steps A) i) to iv) are carried out in one or more spinning units. Each unit contains an extruder that supplies the cellulose solution to separate or combined coagulation fluid containers. Preferably, a plurality of spinning units are combined, as shown, for example, in WO 02/12599 A1. Preferably, the coagulation liquid flowing from the spinning unit is collected through the channel, mixed together with the solvent from step D) and further processed together, in particular for concentration. More preferably, the solvent-containing aqueous coagulation liquid flowing from the spinning unit is collected through a channel or channel system and mixed together with the solvent or aqueous solvent mixture from step iv) and sent for purification, concentration and recycling. Losses of atomized solvent from the block may reach the bottom. From here, the solvent-containing liquid is collected through the channel and moved. To this end, the device according to the invention has a channel (eg an open trough or a closed pipe) at the bottom for accumulating and transporting the coagulation liquid flowing from the spinning unit, which leads to a liquid collecting container or to an evaporator for liquid containing cellulose solvent. Preferably, this channel is covered with a cover that can be walked on but is permeable to liquid so that the lyocell operator's contact with the solvent-containing liquid is minimized. An example of this type of cover is a grille.

The present invention will now be further explained through embodiments that are described below.

In fig. 1 shows the location where solvent-containing waste streams in a lyocell process can accumulate. The lyocell process is roughly divided into the stages of mixing raw materials, dissolving the pulp, filtration, spinning (or, in general, molding), solvent extraction/washing of molded products/cutting of molded products, drying of molded products, and further processing (such as rolling, crimping, and etc.) - depending on the processing option from the starting cellulosic material (such as wood pulp) to the final molded products. Waste in the specified individual stages is labeled and registered. The diagram shows a tank with a channel that covers the collection of wastewater containing solvent (particularly since a storage tank and collection channels are used to collect the wastewater). Therefore, solvent-containing products and wastes are: (1) cellulose suspensions, (2) cellulose solutions, (3) coagulated cellulose solutions, (4) molded pulp products in continuous form, (5) molded pulp products in cut form, ( 6) solvent-containing wastewater.

(1) Cellulose suspensions

Cellulose suspensions are mixtures of the main components of cellulose, water and a solvent, such as N-methylmorpholine-N-oxide (NMMNO). Moreover, stabilizers and other substances that are important for the process are added. Cellulose suspensions appear as waste in the area of the feed mixing unit and also during the dissolution operation. Possible compositions of cellulose suspensions are shown in Table 1.

Table 1. Examples of cellulose suspensions of various compositions

Cellulose concentration NMMNO concentration Water concentration Symbol c_Cell c_NMMNO c_H ₂ O Units [mass. %] [mass. %] [mass. %] Letter a b c Example No. 1 5.7 75.3 19.0 2 6.5 69.2 24.3 3 7.7 71.1 21.2 4 8.3 71.0 20.7 5 9.0 69.7 21.3 6 10.0 64.3 25.7 7 10.5 59.2 30.3 8 10.5 61.8 27.7 9 10.5 65.2 24.4 10 10.5 67.2 22.4 eleven 10.5 69.4 20.1 12 11.9 64.7 23.4 13 12.5 62.3 25.2 14 13.2 61.1 25.7 15 15.9 58.0 26.1

(2) Cellulose solutions

The cellulose is dissolved by removing water from the suspension and thus concentrating the solvent. Cellulose solutions appear as waste in the block area for dissolution, filtration and spinning (eg spinning). Possible compositions of cellulose solutions are shown in Table 2.

Table 2. Examples of cellulose solutions arising from these cellulose suspensions

Cellulose concentration NMMNO concentration Water concentration Symbol c_Cell c_NMMNO c_H ₂ O Units [mass. %] [mass. %] [mass. %] Letter a b c Example No. 1 6.1 80.2 13.7 2 7.5 79.9 12.6 3 8.5 78.8 12.7 4 9.3 79.2 11.5 5 10.2 78.7 11.1 6 12.0 77.1 10.9 7 13.4 75.7 10.9 8 12.9 76.4 10.7 9 12.5 78.0 9.5 10 12.2 78.1 9.7 eleven 11.8 78.2 10.0 12 14.1 76.5 9.4 13 15.1 75.4 9.5 14 16.1 74.8 9.1 15 19.7 71.9 8.4

(3) Coagulated cellulose solutions

The solvent present in the cellulose solution is extracted by adding water and the cellulose is precipitated (coagulation occurs when the cellulose solution is introduced into the coagulation liquid). In addition to the main process, where this effect is essential for molding the pulp product, it is also used to bind various wastes with water or to reduce their stickiness. Depending on the location where the waste accumulates and the original solution, cellulose solutions coagulated in this way have very different compositions. Coagulated cellulose solutions arise from the processing of cellulose solutions from waste (2) in the area of the block for dissolution, filtration and spinning (eg spinning). Possible compositions of coagulated cellulose solutions are shown in Table 3.

Table 3. Examples of cellulose solutions coagulated in water

Cellulose concentration NMMNO concentration Water concentration Symbol c_Cell c_NMMNO c_H ₂ O Units [mass. %] [mass. %] [mass. %] Letter a b c Example No. 1 6.7 62.1 31.2 2 7.9 51.2 40.9 3 14.2 57.3 28.5 4 22.5 32.9 44.6 5 6.2 75.3 18.5 6 12.3 70.0 17.7 7 12.5 74.3 13.2 8 16.7 63.8 19.5 9 13.9 64.8 21.3 10 11.6 55.7 32.7 eleven 24.8 40.3 34.9 12 28.7 16.2 55.1 13 22.4 29.4 48.2 14 17.3 15.8 66.9 15 16.4 19.0 64.6

(4) Cellulose fiber products in continuous form

Cellulose fiber products (or in general, molded products) in continuous form are produced in the lyocell process as an intermediate product and also as a final product.

Waste in this form appears in the extrusion (spinning) unit, as well as in subsequent processes of solvent extraction, washing and product processing (for example, cutting). Possible compositions of cellulose fiber products, both continuous and cut, are shown in Table 4.

(5) Cellulose fiber products (molded products) in cut form

Molded pulp products in cut form are obtained through product processing steps (eg cutting) from continuous molded pulp products (4). Possible material compositions correspond to cellulose fiber products in continuous form and are included in Table 4.

After solvent extraction in a conventional product, no portion of the potentially extracted solvent can remain in the cellulose fiber product. Solvent-free solid waste can be disposed of. If solvent remains in the waste after extraction, for example in an exceptional case or in the event of a work stoppage, this waste may be recycled along with other solvent-containing solid waste.

Table 4. Examples of products from cellulose fibers at various stages of the process. They are valid for both continuous and cut cellulosic fiber products

Cellulose concentration NMMNO concentration Water concentration Symbol c_Cell c_NMMNO c_H ₂ O Units [mass. %] [mass. %] [mass. %] Letter a b c Example No. 1 15.4 43.0 41.6 2 17.3 27.9 54.8 3 19.4 22.4 58.2 4 22.1 14.3 63.6 5 20.4 10.9 68.7 6 21.4 5.4 73.2 7 21.8 2.1 76.1 8 26.3 1.2 72.5 9 28.0 <1 72.0 10 38.4 <1 61.6 eleven 43.8 <1 56.2 12 53.7 <1 46.3 13 56.9 <1 43.1 14 53.4 3.0 43.6 15 42.6 9.7 47.7

(6) Wastewater containing solvent

Solvent-containing wastewater can occur intentionally or unintentionally in a wide variety of areas of lyocell process units. Specific collection and recycling of said wastewater is an essential element of the solvent loop and is carried out regularly to ensure high solvent recovery.

Thus, in areas of lyocell process units where solvent-containing wastewater may be generated, special requirements are placed on the wastewater and the channel network in order to specifically collect said wastewater. The affected areas of the blocks are made impervious to liquid, for example by using seals and wear-resistant concrete or a special floor covering.

The main sources of wastewater containing solvent are the backwash and regeneration operations during the filtration and purification stages of the cellulose solution and solvent in the process. Other sources include industrial plant cleaning operations and solvent-containing wastewater generated during solvent recovery from solid waste.

The various possible compositions for secondary wastewater streams containing solvent are shown in Table 5.

Table 5. Examples of solvent-containing wastewaters with or without solids. Typically the solids contain cellulose, but this is not always the case, especially for wastewater produced from treatment unit components.

Solids concentration NMMNO concentration Water concentration Symbol c_solids c_NMMNO c_H2O Block [mass. %] [mass. %] [mass. %] Letter a b c Example No. 1 0.0 83.4 16.6 2 0.0 53.4 46.6 3 0.0 45.7 54.3 4 0.0 24.6 75.4 5 <1 26.7 73.3 6 <1 22.4 77.6 7 <1 14.3 85.7 8 0.0 12.4 87.6 9 <1 10.2 89.8 10 0.0 3.4 96.6 eleven 0.0 1.5 98.5 12 3.4 10.5 89.5 13 6.7 12.4 87.6 14 <1 <1 99.0 15 0.0 <1 100.0

According to the invention, when recycling solvent in the lyocell process, efficiency is improved by renewing and treating various types of solvent-containing residual materials, waste and wastewater.

According to the invention, a method is disclosed which provides the following steps for the preparation of waste or residual materials, as well as mixtures of residual materials and wastewater:

(a) Accumulation of solid, solvent-containing wastes (such as those cited above in paragraphs (1)-(5)). These wastes can be further processed separately or after collecting together some or all of the waste materials from (1) to (5).

(b) Grinding of waste materials specified in paragraph (a). Since water is used in this step, some or all of the solvent can be extracted again, and this extraction liquid can be sent to the solvent preparation step. The specified waste materials (1)-(5) can be crushed separately or together.

(c) Extracting cellulose solvent from crushed waste materials or mixtures of materials, preferably in a general method that can be used in the same way for all solid waste materials (1) - (5).

(d) Removing water from the residual solids extracted in step (c), with optional subsequent washing and purification of the substances. In this regard, steps (c) and (d) of the process can be repeated as many times as possible until the desired residual solvent content in the solid residues is achieved. Ultimately, these solids are removed from the process as waste.

(e) Collection and treatment of all solvent-containing wastewater. This includes both the wastewater produced in steps (a)-(d) and all solvent-containing wastewater (6) collected in the lyocell plant. Depending on the degree of contamination of wastewater, it can be purified from solid contamination separately in one or more filters. Preferably, all collected solvent containing wastewater is treated together in one or more fine filtration steps.

(f) The wastewater filtered in step (e) of the process enters the cation and anion exchanger in order to remove ionic contaminants that interfere with the lyocell process (eg iron or copper ions).

(g) The clean solvent-containing wastewater from process step (f) enters a concentration unit where the solvent content is again increased to the original concentration used in the lyocell process.

Because the solvent recycling rate is increased so effectively, the process according to the invention is extremely environmentally friendly and contributes to the economic efficiency of the lyocell process.

(a) Collection of waste materials

The above wastes (1)-(5) accumulate in various locations, as can be seen in FIG. 1, and as described, have different properties. In order to prepare these waste materials for the next process step (b), a variety of optional process steps may be used:

- Preparation of coagulated cellulose solutions (3) from cellulose solutions (2) by moistening or immersing in non-solvents, preferably water. This eliminates the stickiness of materials and makes them easier to transport.

- Cooling of waste ((1), (2) and (3)), which is usually hot, with chilled water. This helps harden the medium and makes grinding easier.

- Rough separation of inorganic and organic residual materials, in case of presence of inorganic or metallic impurities in the mixture.

- Portioning waste into easily transportable containers. This provides an easy temporary decoupling between batch receipt and continuous waste treatment. In addition, said separation makes it possible to systematically select the grinding sequence in the next process step.

- Mixing of waste molded pulp products, in particular fibers ((4) and (5)), with waste solutions ((2) and (3)), either directly in connection with collection, or by alternative input to the grinding stage (b) way.

The purpose of mixing is to increase the grinding effect of the grinding device for components that are difficult to grind, such as waste cellulose fibers. The composition of a mixture of two parts waste cellulose fibers ((4) and (5)) with one or more parts waste solutions ((2) and (3)) has a positive effect on more efficient grinding. Particularly preferred are mixtures of one part waste cellulose fibers and two or more parts waste solutions.

The amount of various wastes (1) - (5) that accumulate depends greatly on the type of plant and the resulting pulp product. Examples of possible waste distributions during the production of cellulose staple fiber are shown in Table 6 and Table 7.

Collection and storage of waste materials takes place in any transportable container. There are no special requirements for the equipment used.

Table 6. Daily amount of waste during normal operation relative to normal hourly production (NHP) of spinning solution in the production line.

Loading Minimum amount of waste relative to NHP, % Maximum amount of waste relative to NHP, % Expected amount of waste relative to NHP, % Cellulose suspensions (1) 0 10 0 - 5 Cellulose solutions (2) 0 50 5 - 15 Coagulated cellulose solutions (3) 0 thirty 3 - 8 Continuous cellulose fibers (4) 0 5 0.3 - 0.8 Cut cellulose fibers (5) 0 5 0 - 0.5

Table 7. Daily amount of waste during the start-up period relative to normal hourly production (NHP) of spinning solution in the production line

Loading Minimum amount of waste relative to NHP, % Maximum amount of waste relative to NHP, % Expected amount of waste relative to NHP, % Cellulose suspensions (1) 10 100 20 - 50 Cellulose solutions (2) 100 400 150 - 200 Coagulated cellulose solutions (3) 100 400 100 - 150 Continuous cellulose fibers (4) 1 20 3 - 8 Cut cellulose fibers (5) 1 5 12

(b) Shredding of waste materials

Shredding of the waste materials specified in (a) shall be carried out separately or after combining some or all of the wastes.

The grinding of waste materials can be carried out in one or more stages, with the aim of obtaining a final granule size in the range between 5 and 15 mm in order to obtain a sufficiently large surface area for the subsequent extraction process.

The following process steps have been shown to be advantageous for comminution:

- The crusher simultaneously thoroughly mixes the residual waste. Mixing the different types of waste, which are described in (a), Collection of Waste Materials, increases the grinding efficiency for waste cellulose fibers.

- Pre-grinding to a waste granule size of less than 50 mm, preferably less than 30 mm, in particular less than 20 mm, can be carried out using a slow-moving crusher in a specific energy-saving and safe operating mode. An example of material obtained in this connection is shown in FIG. 2.

This method with a slowly rotating rotor shaft has a certain advantage, since these devices introduce only a small amount of frictional energy, and thus the waste materials are not at risk of thermolysis, which can lead to decomposition of NMMO and a fire hazard.

- During grinding, an aqueous solvent or pure water can be added to the waste so that even as the surface area increases, coagulation of the waste materials occurs and the cellulose solvent is extracted already at the grinding stage.

Subsequent comminution with a fast moving cutting device, such as a shear crusher, can reduce said pre-comminuted material particularly effectively to a target granule size of between 2 and 15 mm, preferably about 10 mm. Additionally, this subsequent comminution may be carried out in a humid environment where a cutting pump jet may be used to force a stream of extraction water along with the solid material through the cutting means. This type of medium supply is particularly advantageous since the water flow simultaneously has a cooling effect and also acts as an extraction solvent (process step (c)).

For pre-shredding, slow-moving grinding devices such as, for example:

- GSL Slow Speed Granulator from ZERMA Zerkleinerungsmaschinenbau GmbH

- ZPS Single Shaft Shredder from AMIS Maschinen-Vertriebs GmbH

- ANTARES Single Shaft Shredder from Lindner Recyclingtech GmbH

- M&J FineShred from Metso Waste Recycling.

For subsequent grinding, fast-moving grinding devices such as, for example:

- cutting mill ALPINE Rotoplex from Hosokawa Alpine AG

- fine cutting mill CS-Z from Netzsch Lohnmahltechnik GmbH.

Hammer mills (e.g. for pre-grinding):

CEMTEC Cement and Mining Technology GmbH; Gebr. Jehmlich GmbH; J. Rettenmaier & Söhne GmbH + Co. KG; MINOX Siebtechnik GmbH SIEBTECHNIK GmbH;

Granulators, tearing machines, grate crushers (mills) from companies:

Alexanderwerk GmbH; AMIS Maschinen Vertriebs GmbH; Automatik Plastics Machinery GmbH; BKG Bruckmann &Kreyenborg; Coperion GmbH; Dreher GmbH & Co KG, ECON GmbH; EREMA Ges.m.b.H. Gala K. + K.-Maschinen GmbH; Getecha GmbH; HB-Feinmechanik GmbH & Co. KG; Herbold Meckesheim GmbH; HOSOKAWA Alpine AG, Lindner Recycling Tech; Nordson XALOY Europe GmbH; Noris Plastic GmbH & Co. KG; Pallmann Maschinenfabrik GmbH & Co. KG; Plasma GmbH; Reduction Engineering GmbH; Rolf Schlicht GmbH; UNTHA Recyclingtechnik GmbH; Wanner Technik GmbH; Wittmann Robot.

In fig. 6 shows a crusher (1) according to the invention with a material collection chamber (2), which can be filled with the material to be crushed (3) by dosing or in batches. The material dispenser (4) may be located on a material collection chamber (2), which is substantially covered and may be provided with a feeding device (5). A side-mounted rotating rotor (6) is mounted in a material collection chamber (2), which is inserted into the housing (7) and in the material collection chamber (2), there is a feed pressure regulator (8) that can move in the direction of the rotor to maintain pressure onto the material (3) that will be crushed. The control device (9) for the feed pressure regulator (8) is included in such a way that the feed pressure regulator can be rotated around the axis (10) and thus the material to be crushed can move towards the rotor (6) in batches and can press on the rotor , which is equipped with cutting elements (12).

In such a context, the feeding and pressing of material (3) provides a controlled amount of material that can create a load on the rotor (6).

If the rotor (6) cannot process the amount of material (3) supplied by the feed pressure regulator (8), the feed thereby exerting pressure because the crushed material (13) is not transported fast enough from the rotor housing (7), the feed pressure is reduced regulator (8) so that the rotor can rotate freely due to the reduction in applied pressure (free grinding). If the rotor power decreases, the feed pressure regulator (8) is used to supply material (3) to the rotor (6).

The degree of grinding of the material (13) can be adjusted using a perforated sieve or plate (14) located below the rotor (6). In fig. 9 shows that plates with square (b) or round (a) holes are used, the diameter or size (for square or other shaped holes: center of the smallest and largest holes) being preferably chosen between 3 and 50 mm, particularly preferably between 5 and 30 mm, in particular between 8 and 20 mm.

The rotor (6) may be provided with cutting elements (12), such as hook-shaped choppers, blades or cutting plates, or cutting edges around the entire periphery, arranged in a spiral (Fig. 8b) or sinusoidally wound, the cutting elements being attached to the rotor blade holders screws, or in fact can also be rigidly welded. In fig. 7 shows a rotor with crusher cutting elements, which are constructed from individual offset elements. Preferably, the cutting edges and/or counter-cutting edges are serrated. The cutting edge and the counter-cutting edge are actually positioned diametrically with the closest possible separation from each other, which is convenient for cutting, or with virtually no separation, so that they can move past each other for the purpose of cutting. The serrated design optimizes cutting and prevents backsliding of materials being cut. Preferably, the tips of the teeth are formed with edges at an angle of from 160° to 30°.

Grinding of the incoming material is carried out between cutting elements (12), which rotate with the rotor, and fixed counter-cutting edges (11), which optionally rotate, such as counter-cutting blades or stator cutting edges.

After shredding the waste, carried out between the rotating cutting elements (12) and the counter-cutting edges (11), the cut material is immediately forced through the perforated plate (14), which determines the size of the cut material, in accordance with the size of the perforations in the plate, and can be continuously released . Using a transport means (16) located below the rotor housing (7) and an outlet shaft (15), such as, for example, a conveyor belt, a conveyor auger, a chain conveyor, or a vacuum unit, the ground product can optionally be transferred further to the additional stage. grinding or for solvent extraction or for washing.

The grinding according to the invention and the preparation of the material for further processing of the cut material, such as leaching, washing and solvent recovery, can be carried out in a single shaft crusher or in a multi-spindle crusher in a horizontal and/or vertical design.

Likewise, the method of the invention can be used for coarse grinding in a pre-grinding step followed by a single (or multiple) fine grinding step. The size of the crushed particles (large, small) can be determined by the size of the perforations.

The crusher according to the invention can be used for any cellulosic material and is not limited to the use of lyocell materials. Thus, material from other molding processes such as the rayon process or the cupro process can also be used. In these embodiments, the cellulosic material may be derivatized cellulose, such as cellulose xanthate or alkali cellulose. In the rayon process, wood pulp is converted to alkali cellulose in several process steps by treatment with sodium hydroxide and, through other subsequent reaction with carbon disulfide, it is derivatized into cellulose xanthate. After derivatization, the final viscose spinning solution is obtained by further adding sodium hydroxide and diluting with water, which is pumped through spinnerets into a spinning bath containing acid.

Here, during coagulation of the viscose solution, one viscose thread is formed in the hole of the spinneret. By means of drawing steps and further processing by combining individual threads, rayon threads are obtained, which are wound on bobbins, or staple fibers are obtained by further cutting continuously twisted rayon threads. Downstream of the spinning process, desired and undesired products are obtained which can be processed according to the invention.

If the method according to the invention is used in the viscose process, the main problem is not solvent recovery, but the environmentally acceptable disposal of spinning waste and residual fibers, in particular using auxiliary grinding. Similar process steps are used in cellulose derivatization using the cupro process. In the cupro process, wood pulp is dissolved in an ammonia solution of tetraamine copper (II) hydroxide. The resulting solution and the resulting molded products in the desired and undesired forms are treated as waste according to the invention, in particular by grinding. Examples of molded articles in each embodiment include yarns, staple fibers, films, membranes.

Of course, the use of the lyocell method is preferable, since there is a synergistic effect with solvent regeneration. It is even possible to add liquids during the grinding process. By adding water, a solvent or non-solvent, or other precipitating agents, the waste to be crushed in the grinding step can on the one hand be processed for subsequent precipitation and extraction of material and/or on the other hand can be cooled at the same time.

In this regard, the invention also relates to an impact crusher with projecting grating or cutting elements and one or more counter-cutting edges, where the cutting elements slide after the counter-cutting edges in such a way that molded products or waste molded products are crushed between the cutting edges. elements and counter-cutting edges. Said molded articles or molded article waste preferably contain cellulose, in particular after a solution molding process, for example in the lyocell process, the rayon process or the cupro process.

The invention also relates to a method for grinding said molded articles or waste molded articles using a crusher. Preferably, the crusher has a feed pressure regulator that presses the molded products or waste molded products to be crushed against the rotor or grate or cutting elements. Preferably, the crusher includes any one or more of the above features, or all of the features. Preferably, the cutting edges and/or counter-cutting edges are serrated. Preferably, a sieve is provided near and/or below the rotor in order to regulate the size of the cut material.

(c) Solvent extraction of cellulose

The cellulose solvent extraction is the same for all solids processed in step (b) of the process. Typically the extraction is carried out at a temperature between 15°C and 30°C and for granule sizes less than 30 mm, the required holding time is from 0.5 to 2 hours. In this regard, it is advantageous to use constant stirring and suspension of the solid.

The following optional steps can be taken to speed up the extraction:

- Increasing the average extraction temperature from 40°C to 70°C increases the rate of material extraction and reduces the required holding time by approximately a quarter. This is particularly advantageous when this temperature increase can be achieved by recovering heat from a waste heat stream that is otherwise not used.

- Reducing the granule size reduces the required holding time.

- When the extraction is carried out in multiple stages, following the counter-current principle, this reduces the requirements for each individual extraction stage, since there is no likelihood that part of the waste, which still contains solvent, will immediately leave the extraction tank in the next stage of the process.

Preferably, the extraction is carried out in an open or closed container, vessel or reservoir. The mixture of solvent and solid is driven, either by stirring or by generating a flow using a pump. Optionally, the temperature can be deliberately increased either by preheating the incoming solvent, or indeed by introducing steam directly into the process.

(d) Removal of water (dehydration)

The solid extracted or partially extracted in step (c) of the process is separated from the solvent-containing water during dehydration. The resulting dry matter is essential for the efficiency of the extraction stage. The solid thus dehydrated can now either be fed into the contact step with fresh extractant or, at a relatively low solvent content, can be jetted out of the process as waste. An example of this type of waste is shown in Fig. 3. The specified concentration of solvent in solid waste should be less than 3%, taking into account the recovery rate. Additional reduction in solvent concentration may be beneficial, depending on the required investment volume according to the process regulations.

The solids recovered in step (d) of the process can be fed into other types of processes. For example, the isolated cellulose components can be used as compost material, as a construction additive in road construction, for drainage backfill or for sealing.

In the first stage of dewatering, the goal is to roughly separate the solid from the solvent. Since the solid as well as the filtrate will be sent to an additional processing step, there are no specific requirements for fine separation. Continuously operated solid-liquid separators are therefore particularly suitable, such as for example:

- PSS separator from FAN Separatoren GmbH

- PSS separator from Erich Stallkamp ESTA GmbH

- MDF rotary microfilter from ABZ Zierler GmbH

- Belt press from Flottweg SE

In the final stage of dewatering, the goal is to remove as much solvent-free solid waste as possible from the liquid and thereby reduce the solids content of the filtrate to a minimum. In general, in this regard, the above devices can be used, but preferred devices are, for example: a chamber filter press from Welders Filtration Technology NV SA; or settling centrifuge from Flottweg SE.

Ultrafiltration units:

Aqua-System Technologie GmbH; Krones AG; OSMO Membrane Systems GmbH;

Microfiltration units:

Annen Verfahrenstechnik GmbH; Atec Automatisierungstechnik GmbH; ECOFLUID Handels GmbH; Hydro-Elektrik GmbH; Lanz-Anliker AG; Lenzing Technik GmbH; Tetra Pak Processing GmbH; WAG Wasseraufbereitung GmbH;

Reverse osmosis units:

AS Schmertmann GmbH; Decker Verfahrenstechnik GmbH; Enviro-FALK GmbH Prozesswasser-Technik; MembraPure Gesellschaft für Membrantechnik GmbH;

Manufacturers of ultrafiltration membranes/microfiltration membranes:

KOCH Membrane Systems GmbH / John Zink KEU GmbH; MICRODYN-NADIR GmbH; MTS & Apic Filter GmbH & Co. KG; SOMA GmbH & Co. KG;

Reverse osmosis membranes:

CWG® Watertechnology GmbH; Kalle Wassertechnik; KOCH Membrane Systems GmbH / John Zink KEU GmbH; OSMO Membrane Systems GmbH; POREX Membrane.

(e) Collection and treatment of all wastewater containing solvent

The wastewater generated in process steps (a) to (d) is preferably collected together with any solvent-containing wastewater (6) generated in the lyocell block.

Optionally, depending on the degree of contamination of individual wastewater streams, they can be purified separately, in one or more filters, from large solid contaminants. The goal is for the maximum average solids content of the collected solvent containing wastewater to be 1000 mg/L or less, for example 20 to 1000 mg/L, preferably 200 mg/L or less, and particularly preferably 50 mg/L l or less.

The collected solvent-containing wastewater is purified (preferably together) through one or more fine filtration steps. This filtration step can be carried out using one or more different filtration devices, in which micro-sieve or multi-layer filters are particularly convenient. The purpose of filtration is to protect the downstream process from contamination by particulate matter. Depending on the selectivity, at this stage of filtration, components that give color can be extracted; which is especially preferable.

Typically, wastewater is collected in a tank that is liquid-tight and chemical-resistant. Individual process wastewater streams can be pre-filtered as described. Examples of suitable filtration equipment, depending on the degree of contaminant, are: end-gap filters, basket filters, or for coarser contaminants, any of the solid-liquid separators listed in (d). The collected wastewater is then finely filtered to protect downstream processes. Examples of commonly used devices are: multilayer filters, microfilters and membrane filters.

(f) Deionization

At this stage of the process, ionic impurities are removed using one or more anion and cation exchangers. Typically, deionization is carried out in separate anion and cation exchangers, where a sequence of ion exchangers in the configuration of an anion exchanger followed by a cation exchanger can be advantageous to the process.

The average residence time for the filtrate in the ion exchange section provided in accordance with the method is between 2 and 20 minutes, particularly preferably between 8 and 12 minutes. Deionization is carried out to ensure the reliability of the lyocell method, since harmful ions are removed.

(g) Solvent concentration/enrichment

In the next part of the method, the cellulose solvent is sent for concentration, for example, to a multi-stage evaporation unit. In this regard, at least such a concentration of solvent must be obtained that the solution is again suitable for dissolving or suspending cellulose. However, the concentration of the solution should not yet be reached, since non-solvent is removed from the cellulose suspension into the solution. Preferably, at least 50% (by weight) of solvent is obtained. Alternatively, a higher concentration may be obtained for the purpose of handling a smaller volume (for subsequent dilution with a non-solvent). Preferably, more than 70%, preferably 83% to 85% (by weight) of the evaporated cellulose solvent is subsequently added as fresh solvent in the process step of obtaining a cellulose suspension for further use.

Recycle streams of aqueous solvent are used as fresh solvent in a continuously operating solution production. Thus, the method according to the invention ensures the return of organic residual or starting materials, as well as waste water accumulated in the process for the production of cellulose fibers, to their original usable state, and provides a closed solvent loop.

In addition, the fact that the process is carried out with environmentally sustainable degradable raw materials or residual materials leads to an equilibrium that is harmonious with respect to CO ₂ emissions and which is environmentally neutral, since the recovered solvent-free solid cellulose can be composted without hesitation.

Further details, features and advantages of the invention will become apparent from the following description of an exemplary embodiment, illustrated with the aid of the figures.

In fig. 4 is a diagrammatic representation of a simplified block diagram showing a diagram of the method according to the invention, as well as a design of a device according to the invention suitable for carrying out the method according to the invention. In addition to the main components of the method according to the invention or the device according to the invention, FIG. 4 also illustrates additional elements as components of the preferred embodiments.

A list of examples of the different types of devices that can be used has been compiled. This list is not exhaustive, and individual devices can be replaced by other units with which the method achieves a similar effect at any time.

In order to evaluate the degree of solvent recovery, in particular N-methylmorpholine-N-oxide, in a lyocell production unit, a simple balance can be established using the method of the invention.

In fig. Figure 5 shows the solvent circulation circuit in the lyocell method:

- Stream A contains all waste solids ((1)-(5)) containing solvent, as well as waste water (6).

- Stream S represents the sum of the compressed waste solids appearing in step (e) of the process and which leaves the recovery and recovery unit.

- Stream F is the sum of the wastewater streams that leave the receiving and regeneration unit.

- The two V streams represent other, not yet described, solvent losses. These losses include, among others, losses due to thermal decomposition, and losses of the resulting cellulosic product. In the future, the calculation is carried out with the sum of all significant losses in the form of one flow.

- Stream M represents the fresh solvent stream that is needed to compensate for solvent losses.

- The N stream is a concentrated solvent stream that is reused in the production process.

From this balance the following function is derived for the RGR recovery rate:

RGR = 1 - F _F - F _S - F _V

in which the loss coefficients F _F , F _S and F _V are defined as follows:

where, for example, , in units of kg/h, means the mass flow of solvent (eg N-methylmorpholine-N-oxide) that is on average in stream F in FIG. 5. Thus, the coefficient F _F describes the ratio of the solvent flux that is lost in the lyocell process wastewater relative to the total solvent used, F _S describes the ratio of the solvent flux that is lost in the lyocell process solid waste relative to the total solvent used, and F _V describes the ratio of all solvent flows that are not included in the F _F or F _S factors and that are lost in the lyocell process, relative to the total solvent used.

In the context of this process, the solvent flow F is highly dependent on the configuration of the ion exchange step (f) of the process. The empirical value of the resulting loss factor F _F is approximately 0.0033.

The flux V of the undetermined total losses, in the context of this method, depends on the configuration of the concentration stage (g).

The loss factor F _S is solely dependent on the solvent remaining in the solid waste of process step (d), which depends on process steps (a) to (d) and the selected process variant and the process devices used.

As an example of a successful configuration for the method of the invention, the loss factor can be calculated as follows:

The estimates given in Table 6 for individual waste streams provide average daily solid waste quantities of approximately 8% to 25% of the normal hourly spinning solution output during normal operation.

From this, in step (e) of the process, washed, compressed solid waste is obtained which still contains residual solvent.

This amount can be calculated using the following formula:

wherein means the total average waste flow S, in kg/h, and is the average solvent concentration, expressed as a percentage by mass, in a specified waste stream S.

To maximize the average value of solid waste collected in step (a) of the process, under normal operation 25% per day of the normal hourly spinning output will result in a loss factor value F _S of less than 0.0001 for the residual solvent concentration 3% in waste from process step (d).

Claims (27)

1. A method for regenerating a cellulose solvent in a method for producing molded cellulose products, which includes the stages: A) continuous or batch production of solid molded cellulose products from a cellulose solution, which includes the steps of: i) obtaining a cellulose solution from dissolved cellulose and cellulose solvent, ii) molding the cellulose solution into the desired geometric shape, iii) solidifying the molded cellulose solution into a molded cellulose product in a coagulation liquid, iv) releasing or extracting solvent from the molded pulp product using a non-solvent, wherein during a continuous or batch process waste moldings from the cellulose solution accumulate in an undesired form and not necessarily in a desired form, B) collecting waste moldings in undesired form and not necessarily in desirable form, C) grinding the molded waste from step B), optionally containing a solvent and/or containing a non-solvent, D) solvent extraction from crushed waste moldings, characterized in that solid solvent-containing cellulosic waste, which accumulates before and during molding, is mixed and ground together, or in that the solvent from the coagulation liquid from step A) iii) and the extracted solvent from step D) are concentrated together. 2. The method according to claim 1, characterized in that at stage i) a non-solvent, preferably water, is additionally used to obtain a cellulose solution. 3. The method according to claim 1, characterized in that at stage iv) water or an aqueous medium is used as a non-solvent. 4. The method according to claim 1, characterized in that the molding of the cellulose solution in step ii) is an extrusion of the spinning solution, or spinning into strands, threads or films, where the waste molded products are in an undesirable form in the form of a sticky mass of strands, threads or films. 5. The method of claim 1, wherein the desired or undesired molding waste after molding, either alone or with solid solvent-containing cellulosic waste that accumulates before molding or after grinding, is mixed and ground together. 6. The method according to claim 1, in which the grinding in stage C) is carried out under the influence of mechanical force, preferably in a crusher. 7. The method according to claim 6, characterized in that for grinding a crusher is used with a rotor having one or more protruding cutting elements and one or more counter-cutting edges, where the cutting elements slide after the counter-cutting edges in such a way that molded products or molded waste are crushed products between the cutting elements and the counter-cutting edges, and the molded products or waste molded products are continuously or periodically fed to the cutting elements for grinding by means of a pressure maintaining device. 8. Method according to claim 1, characterized in that the cellulose solvent is N-methylmorpholine-N-oxide or an ionic solvent, preferably with an ammonium, pyrimidium or imidazolium cation, especially preferably 1,3-dialkylimidazolium, especially preferably butyl-3- methylimidazolium or 1-ethyl-3-methylimidazolium. 9. The method according to claim 1, characterized in that the solvent or mixture of an aqueous solvent from the washing containing the solvent and the cutting liquids from step A) iv) and the liquids containing the aqueous extraction solvent from step D) is concentrated after dissolution or extraction; preferably in order to obtain a cellulose solvent solution which is suitable for dissolving or suspending cellulose, or preferably at a concentration of at least 50% (% by weight) of the solvent in the solution, especially in the case of N-methylmorpholine-N-oxide as the solvent. 10. The method according to claim 9, wherein the concentration includes evaporation of a non-solvent, preferably water; or solvent crystallization, and/or dynamic separation process. 11. The method according to claim 1, characterized in that the coagulation liquid from which the molded pulp products are separated from step A) iii) after transportation from the container with the coagulation liquid is collected together with the extracted solvent from step D). 12. The method according to claim 1, characterized in that the coagulation liquid is in a container and a storage tank for collecting cellulose solvent flowing from the container due to transport of molded pulp products associated with the container. 13. The method according to claim 1, characterized in that steps A) i)-iv) are carried out in one or more spinning units, where the solvent-containing aqueous coagulation liquid flowing from the spinning unit is collected through a channel or channel system and mixed together with the solvent or mixture of aqueous solvent from stage iv), and is sent for purification, concentration and recycling. 14. A device for regenerating the cellulose solvent in the method of producing molded cellulose products, which includes a unit for obtaining a spinning solution, a filtration unit for the spinning solution, a spinning unit with an extruder, extrusion pumps, heat exchangers, extrusion devices, dies, a container for coagulation liquid, which is located after the space below the extrusion devices, preferably a die, a recovery device, a cutting device, a container for collecting the hardened molded pulp products, a crusher for the hardened molded cellulose products, a mechanical separation unit for separating solids into liquid, an ion exchange unit, a unit for concentrating the aqueous cellulose solvent or a combination thereof, wherein said device further includes one or more storage tanks for collected aqueous solvent during transport of the desired molded articles or molded articles that are obtained by molding into geometric shapes, or a solution of cellulose in undesirably shaped molded cellulose articles that accumulates from one or multiple containers of coagulation liquid during a continuous process for isolating a cellulose solvent or an aqueous cellulose solvent; and a channel at the bottom for systematically collecting and supplying solvent-containing liquid from the spinning solution receiving unit, the spinning solution filtration unit, the spinning unit, and from the evaporation unit into a liquid collection container. 15. A device according to claim 14 with an evaporator for evaporating non-solvent from liquids containing cellulose solvent. 16. Device according to claim 14 or 15, characterized in that the grinding occurs in at least two stages, preferably including the stages of coarse grinding and fine grinding, and the grinding is optionally carried out in a dry and/or wet state, preferably using hammer crushers, centrifugal crushers with screens with holes or cutting units, tearing units and/or grating units, preferably with a rotor having a protruding grid or cutting elements, as well as a screen with holes, the grid, breaking or cutting elements being directed above the openings of the screen.