EP2885249A1

EP2885249A1 - Process and apparatus for purifying process water in a hydrothermal carbonization process

Info

Publication number: EP2885249A1
Application number: EP13755983.7A
Authority: EP
Inventors: Jan Vyskocil
Original assignee: AVA-Co2 Schweiz AG
Current assignee: AVA-Co2 Schweiz AG
Priority date: 2012-08-15
Filing date: 2013-08-15
Publication date: 2015-06-24
Also published as: US20150209692A1; WO2014027059A1; DE102012107471A1; BR112015003214A2; DE202012012520U1

Abstract

Hydrothermal carbonization allows the production of charcoal from biomass. However, this biomass can at the beginning of the carbonization process contain constituents which are not suitable for carbonization. Apart from large contaminants such as broken glass, etc., these constituents are, in particular, sand and clay, with the clay not being able to be removed by simple filtration methods because of its fineness. The invention therefore provides for process water to be taken from the reaction space and subjected to purification in a sedimentation filter after the carbonization reaction has commenced and the clay is no longer held in the biomass. The process water is then sprayed back into the reaction space in order to keep the biomass/process water mixture in motion and avoid sedimentation of the clay at the bottom of the reaction space.

Description

METHOD AND DEVICE FOR PURIFYING PROCESS WATER IN A HYDROTHERMAL CARBONIZATION PROCESS The present invention relates to a method and a device for purifying process water within a hydrothermal carbonation process in which process water and biomass are introduced into a reaction space, wherein a filtration of the process water via a sedimentation filter arrangement he follows.

Such a solution is known from the prior art already from DE 10 2007 062 808 A1. According to the teaching of this document, a reactor is provided for carrying out a hydrothermal carbonization reaction in the course of which coal is to be produced from a mixture of process water and biomass. During the implementation of the hydrothermal carbonization within the reactor in this case a filtering of the reaction mixture of process water and biomass is provided, which is carried out using one or more internal hydrocyclones. This filter device is provided in the reactor in which the reaction mixture is kept agitated by means of a stirrer. The agitator is disposed within an inner tube so that a vortex is created in the reactor.

Despite the use of such a stirrer according to the teaching of this document is still to treat the problem that sedimentation of undesirable components takes place at the bottom of the reactor, so that after emptying the reactor, a release of the same from the sediments using a dry ice cleaning must be performed.

The reaction mixture, which consists of biomass and process water, basically comprises any carbon-containing material with regard to the biomass. Depending on its origin, this may contain different substances which are not suitable for carbonation, either because they are simply impurities, such as broken glass, screws, coins and the like, or because they are contained in the substances used as biomass. With regard to the latter components may be, for example, sand, silt and the like, which are held firmly in part in the biomass. In particular, sand and silt make up a considerable part of the biomass used for the hydrothermal carbonization reaction, so that it makes sense to get these components as completely as possible out of the resulting product. In particular, these components also make no contribution to the calorific value, so that results in a higher proportion of sand and silt in the resulting biochar in the result, a lower calorific value of the resulting coal product.

A partial problem has already been solved by the abovementioned document DE 10 2007 062 808 A1, by means of which a sedimentation filtration of the process water takes place with the aid of a hydrocyclone. However, it should be noted that apparently the use of a hydrocyclone for coarse or fine screening of all solids present in the process water an insufficient removal of sand and silt is achieved by the arrangement provided in said document, after despite these precautions an elaborate treatment of the reactor by Dry ice is required.

Against this background, the object of the present invention is to significantly improve the filtering of the process water, solely by the targeted removal of the components, such as sand or silt, which lower the quality, based on the biochar formed.

This object is achieved by a process for the purification of process water according to the features of claim 1. Also, this object is achieved by a device for the purification of process water according to the features of the independent claim 7. Meaningful embodiments of the method and apparatus can be taken from the respective subclaims. According to the invention, it is provided that the hydrothermal carbonization process first begins with a mixture of process water and biomass in a reaction space before removal of process water from the reaction space. With the onset of the hydrothermal carbonation reaction, fine components such as silt are released from the biomass, thus creating the opportunity to extract these components from the process water biomass mixture. After the onset of the carbonization reaction, the process water or the suspension is thus removed from the reaction space, for which purpose the reaction space in the bottom area has a process water removal, which is connected to a removal line. The sampling line directs the withdrawn process water to a sedimentation filter arrangement where filtering by sedimentation takes place.

The thus filtered process water is then fed back to the reaction space via a return line, which are arranged in the bottom region of the reaction space in a nozzle arrangement for irradiating the process water into the reaction space.

The removal of the process water from the reaction chamber at the bottom ensures that the natural sedimentation during the hydrothermal carbonisation process is used to feed the most sedimented process water to the filtration. Conversely, by injecting the purified process water by means of injection nozzles into the reaction space without the need for an agitator or a similar mixing device, the mixture of biomass and process water is fluidized in such a way that uniform mixing of the reaction mixture takes place on the one hand and on the other hand already particles sedimented on the bottom of the reactor are stirred up again to prevent caking on the reactor. This prevents that, similar to the prior art, a sedimentation layer forms on the bottom of the reactor, which would then have to be removed in a separate operation, for example with dry ice. The strong cooling of the reactor which accompanies the dry ice cleaning, which extremely stresses the material, can thus be interpreted clearly. lely reduced or ideally even completely eliminated. It is necessary for this purpose that the process water is irradiated during the irradiation into the reaction space with a sufficient pressure, so that due to the process water jet, a swirling of the mixture can be effected.

As a sedimentation filter to which the process water is supplied for purification, a hydrocyclone is used with some advantage, wherein it is readily possible to use several hydrocyclones in parallel or successively for cleaning. It is also readily possible to serve several reaction spaces of an HTC system simultaneously by means of such a sedimentation filter arrangement.

The Einblasdüsenanordnung in the bottom region of the reaction chamber may consist of various types of injection nozzles, which preferably radiate either vertically into the reaction space to give the process water biomass mixture a strong momentum in the air, or are arranged tangentially to the outer wall of the reaction space to a causing tangential acceleration to act on the mixture, which results in turbulence of the mixture in the reaction space. Without further ado, both types of injection nozzles may also be present in the bottom area of the reactor and irradiate the mixture in parallel or alternatively.

It is intended to supply the process water in the form of steam to the carbonation process so as to maintain the required temperature in the reaction space. If necessary, a renewed heating or evaporation can take place after a purification of the process water, so that the process water is again supplied to the reaction space in the vapor state after passing through the sedimentation filter arrangement. Again, alternatively or in series with the said sedimentation filter arrangement, a coarse filter may initially be provided, which allows prefiltration of the mixture. For example, this may be a separator column, which removes coarse unwanted components from the reaction mixture.

In particular, the sedimentation filter arrangement may consist of one or more hydrocyclones, wherein in the case of using a plurality of hydrocyclones, a parallel arrangement is desirable. This is arranged in a preferred embodiment in a filter container, which is divided into three chambers arranged above each other. The feed of the process water takes place here in a middle chamber into which the tangential inlets of the hydrocyclones open. By introducing the process water into this central inlet chamber, the process water can thus enter the respective hydrocyclone and flow there with vortex formation in the direction of a lower funnel section downwards. Due to the funnel-shaped cut of the hydrocyclone, an upward movement is formed in the center of the funnel, which, however, is not accompanied by the sedimenting, sinking components. While these components leave the hydrocyclone via an underflow leading down into a lower sediment chamber, the ascending portions of the process water are introduced into a tubular vortex finder, which is a vertically upright tube and opens out of the hydrocyclone into an upper process water chamber. From the upper process water chamber, in which only enters the purified process water together with the remaining remaining biochar, the process water is then removed and returned to the reaction chamber. The invention described above will be explained in more detail below with reference to an embodiment.

1 shows a reaction space, which for a first pre-filtering with a

Separatorsäule is connected, and 2 shows a reaction space, which is connected for a fine filtration of the process water-biomass mixture with a consisting of several hydrocyclones sedimentation filter arrangement. FIG. 1 shows a reaction space 10 into which previously a mixture of process water and biomass was introduced. In the context of a first pre-filtering shown here, a portion of the mixture, the so-called "slurry", is fed via a bottom-side removal of the reaction space 10 and an extraction line 12 connected to a separator column 40. When filling the separator column 40, the hot process water within a column section 41, while the heavier components, ie the coarse impurities do not follow this upward movement and instead sink downwards in the column section 41 and are thus introduced into a sedimentation tank 42. The process water ultimately arriving at the top of the column section 41 then becomes is returned via a return line 13 into the reaction chamber 10 and blown there back into the interior of the reaction chamber 10 via injection nozzles 14. A return of the initially coarsely filtered process water can hereby also by a run-in at the top of Reaktionsra by 10, whereby an additional swirling by means of injection nozzles 14 in the context of the prefiltering can still be dispensed with by such a raining into the reaction space 10.

FIG. 2 shows the same reaction space 10 from which, after the onset of the carbonization reaction, a mixture of process water and biomass can likewise be withdrawn via the extraction line 12. This mixture is then fed to a sedimentation filter arrangement 20, which is arranged in a filter container 21. In this case, the extraction line 12 opens into a central inlet chamber 22, from which the mixture can run into a plurality of parallel arranged hydrocyclones 30 via a tangential inlet 31. After traversing the inlet 31 of a hydrocyclone 30, due to the tangential movement of the process water to be purified, it will form a vortex within the hydrocyclone 30 and at the same time fall downwards due to gravity. It encounters a funnel section 34 of the hydrocyclone 30, which due to the smaller space available ensures that a portion of the process water in the middle of the hydrocyclone 30 rises again. At this point there is a tubular vortex finder 35, via which the purified process water can run through an upper run 33 into an overhead process water chamber 24. Due to the turbulence within the hydrocyclone 30, the heavier constituents, namely sand and silt and the like, will initially stay further outside in the hydrocyclone 30 and then sink down the funnel wall of the funnel section 34 and ultimately be brought into a sediment chamber 23 via an underflow 32 , The purified process water from the overhead process water chamber 24 is finally passed via a return line 13 to an arrangement of injection nozzles 14, via which the liberated from sand and silt process water biomass mixture is irradiated into the reaction chamber 10. In this case, the jet of the mixture is directed onto the mixture sinking by gravity and still in the reaction space 10, so that settlement of sediments within the reaction space 10 is markedly reduced. If necessary, an evaporator can be arranged in the return line in order to bring the mixture of the purified process water before being introduced into the reaction space 10 again to the temperature required for carrying out the reaction.

Thus, a method and a device for purifying process water, which provides for removal of the process water, external purification and injection of the purified process water in the bottom area of the reaction space, with the effect of avoiding sedimentation in the bottom area of the reaction space, are described above is improved, the result of the filtering by the bottom-side removal of the process water and at the same time the construction of the sedimentation filter arrangement is simplified by the lying outside the reaction space arrangement. REFERENCES I LISTE LIST reaction room

ground

withdrawal line

Return line

Injector

Sedimentationsfilteranordnung

filter container

inlet chamber

sediment chamber

Process water chamber

hydrocyclone

inlet

underflow

headwaters

funnel section

Vortex finder

separator column

column section

sedimentation tank

Claims

P A T E N T A N S P R E C H E

1. A process for purifying process water within a hydrothermal carbonization process, in which process water and biomass are introduced into a reaction space (10),

characterized in that in a bottom region of the reaction space (10) process water via a removal line (12) from the reaction chamber (10) out of a sedimentation filter assembly (20) fed to the filtration and the subsequently purified process water to the reaction chamber (10) is fed back by is radiated directly onto the biomass loosely contained therein by means of a nozzle arrangement in the bottom region of the reaction space (10). 2. The method according to claim 1, characterized in that the filtration takes place by means of a sedimentation filter arrangement (20) which comprises at least one hydrocyclone (30), preferably a plurality of hydrocyclones (30).

3. The method according to any one of claims 1 or 2, characterized in that starting with a removal of process water from the reaction chamber (10) and its supply to the sedimentation filter assembly (20) only after the onset of a Karbonisierungsreaktion in the reaction space (10). 4. The method according to any one of the preceding claims, characterized in that the process water by means of a Einblasdüsenanordnung, which is preferably arranged in a bottom (1 1) of the reaction space (10), tangentially and / or vertically into the reaction space (10) is irradiated. 5. The method according to any one of the preceding claims, characterized in that the process water evaporates after passing through the sedimentation filter assembly (20) and in the vaporized state the reaction chamber (10) is fed again. Method according to one of the preceding claims, characterized in that the process water additionally, preferably in the context of a pre-filtration, using a coarse filter, preferably a separator column (40), is cleaned.

Apparatus for purifying process water within a hydrothermal carbonization process, comprising a reaction space (10) in which a carbonation reaction takes place and a sedimentation filter arrangement (20) for purifying the process water,

characterized in that a process water extraction in the Bodenbe range of the reaction space (10) is arranged, which by means of a withdrawal line (12) with the outer sedimentation filter assembly (20) is connected, wherein in addition a return line (13) of the sedimentation filter assembly (20) to the Reaction space (10) is provided which is connected in the bottom region of the reaction space (10) with a nozzle arrangement for blowing the process water into the reaction space (10).

Device according to claim 7, characterized in that the sedimentation filter arrangement (20) comprises at least one hydrocyclone (30).

Apparatus according to claim 8, characterized in that the sedimentation filter arrangement (20) comprises a plurality of hydrocyclones (30) housed in a filter vessel (21) with three superimposed chambers (22, 23, 24), each hydrocyclone (30) a tangential inlet (31) opening into a central inlet chamber (22), an underflow (32) opening out of a lower funnel section (34) of the hydrocyclone (30) into a lower sediment chamber (23) and a tube via a tubular vortex finder ( 35) in an upper process water chamber (24) opening upper run (33).

10. The device according to one of claims 7 to 9, characterized in that the reaction space (10) is substantially cylindrical, preferably in the bottom region funnel-shaped, formed, wherein the process water extraction and / or the nozzle assembly in a bottom (1 1) of the reaction space which is preferably the geodetically lowest point of the reaction space (10) are arranged.

11. Device according to one of claims 7 to 10, characterized in that the nozzle arrangement is formed of a plurality of tangentially to the walls of the reaction space and / or perpendicular in the reaction space pointing injection nozzles (14).

12. Device according to one of claims 7 to 1 1, characterized in that the return line (13) is associated with an evaporator for the evaporation of the purified process water.

13. The device according to one of claims 7 to 12, characterized in that the reaction space (10) parallel or sequential to the sedimentation filter assembly (20) an additional coarse filter, preferably in the form of a separator column (40) is assigned, wherein the return of the process water From this additional coarse filter can optionally be done via the nozzle assembly or via the reaction space (10) top side associated inlet.