DE102011055986A1 - Hydrothermal carbonization of biomass in continuous flow, comprises feeding biomass by conveyor to a reactor, in which biomass is dehydrated and carbonized, removing carbon slurry fed to outlet by filtering device used for solid separation - Google Patents

Abstract

Hydrothermal carbonization of biomass in a continuous flow, comprises feeding the biomass by a conveyor (3) to at least one reactor (5), in which the biomass is dehydrated and carbonized, removing the carbon slurry emerging through the carbonization from the reactor via at least one outlet, where the carbon slurry is fed to the outlet by a filtering device (8), which is designed for solid separation of larger particles of a defined particle size. An independent claim is also included for device for hydrothermal carbonization of biomass in continuous flow, comprising a reactor with an outlet for removal of the carbon slurry emerging through the carbonization and a filtering device.

Description

The invention relates to a method for the hydrothermal carbonization of biomass according to the preamble of patent claim 1 and to an apparatus for the hydrothermal carbonization of biomass according to the preamble of patent claim 10.

For the purposes of the invention, biomass means all renewable raw materials, i. vegetable biomass and animal derived biomass and their metabolites understood, so for example, green waste, wood chips, plant and plant residues, straw, silage, agricultural residues, paper or sewage sludge etc ..

Methods and apparatus for the hydrothermal carbonization of biomass are already known from the prior art. Hydrothermal carbonisation simulates the natural process of producing lignite. In this case, biomass is dehydrated and carbonated as starting material in a reactor under a pressure in the range between 10 bar and 35 bar and temperatures in the range between 180 ° C and 240 ° C, wherein at the reactor outlet then a coal sludge can be removed. This aqueous or viscous coal slurry contains carbon particles which can be removed from the coal slurry by a drying and / or dewatering process. These coal particles obtained after the drying and / or dewatering process produce a coal dust containing almost all of the carbon of the processed biomass and having a calorific value substantially equal to the calorific value of fossil brown coal. The hydrothermal carbonization is an exothermic reaction, i. In the dehydration and carbonation process, reaction energy is released in the form of heat.

In order to obtain as much as possible by the dehydration and Karbonisierungsprozess a coal sludge containing in addition to the pulverized coal and the liquid no or as few foreign particles, in known methods, the biomass, such as green waste, etc., freed of foreign substances before introduction into the reactor, so that these foreign substances can no longer get into the reactor. This is possible with large-volume or large-scale foreign substances with limited effort. Smaller foreign substances, such as plastic packaging or plastic films, however, usually have to be sorted out of the biomass by hand, which is extremely expensive and therefore expensive. In addition, other impurities, such as stones, sand, etc., may be contained in the biomass, whose sorting is extremely difficult or impossible at all.

Proceeding from this, it is an object of the invention to provide a method and apparatus for the hydrothermal carbonization of biomass in a continuous process, in which the cost of pre-sorting significantly reduced and thus the process is cost-optimized. The object is achieved on the basis of the preamble of independent claim 1 by its characterizing features. A device for the hydrothermal carbonization of biomass is the subject of the independent patent claim 10.

The essential aspect of the method according to the invention, in which the biomass is fed via a conveyor to at least one reactor in which the biomass is dehydrated and carbonated and is removed from the reactor at at least one outlet by the carbonization resulting from the carbonization, is that the coal slurry is led to the outlet through a filter device, which is designed for the solids separation of particles larger than a defined particle size. The separated solids are at least essentially formed by the foreign substances contained in the biomass, which are clumped due to the effect of heat in the reactor to solid particles. By means of the filter device, these solid particles are removed from the coal sludge, which has an aqueous or viscous consistency, so that the coal sludge after the filter device consists almost exclusively of carbon particles in addition to the aqueous components. These can then be extracted from the coal slurry by a subsequent drying and dewatering device. The filter device is preferably designed to filter out particles larger than 100 μm to 3 mm, particularly preferably larger than 500 μm to 3 mm.

In a preferred embodiment, the filter device is at least temporarily cleaned in a self-cleaning process. The coal slurry removed from the reactor is preferably transported under pressure through the filter device, so that after a certain time, a layer of solid particles forming a so-called filter cake form on the filter element of the filter device that performs the filtration. This filter cake interferes with the flow per unit time through the filter and must therefore be removed from the filter element at certain intervals to avoid complete clogging or flow. The self-cleaning property of the filter device allows easier cleaning of the Filter device, without having to open this filter device or remove from the plant.

The filter device particularly preferably comprises at least one filter element and at least one scraper element, the filter device being cleaned by relative movement of the at least one scraper element relative to the at least one filter element or by relative movement of the at least one filter element relative to the at least one scraper element, i. the attached filter cake is detached from the filter element. The scraper element is preferably at least partially against the filter element and removed by the relative movement of the elements to each other the filter cake. This can be done a simple and efficient cleaning of the filter device.

In particular, the filter device may comprise at least one hollow cylindrical filter element, which is flowed through by the carbon slurry from the hollow cylinder outside to the hollow cylinder inside. The use of a hollow-cylindrical filter element results in a filter surface which is very large in relation to the volume or the size of the filter device, so that the throughput of the filter device is optimized. In addition, the filter element formed in this way can very easily be freed from the filter cake forming on the hollow cylinder outside by means of the scraper element.

In a particularly preferred embodiment, a form-fitting to the filter element scraper element is driven by motor, pneumatically or hydraulically at least partially moved along the outside of the filter element or the filter element is driven by a motor, pneumatically or hydraulically moved relative to the scraper element. The motorized, pneumatic or hydraulic drive allows cleaning of the filter without manual intervention by operating personnel. Particularly preferred is a drive by means of an electric motor, which is preferably preceded by a transmission.

The self-cleaning of the filter device can in particular be effected by the filter element being rotated relative to the scraper element. This represents a preferred embodiment in particular when using a hollow-cylindrical filter element, since the filter element is rotationally symmetrical and thereby a structurally simple and space-saving design of the filter device is possible when using the axis of symmetry as the axis of rotation.

Particularly preferably, the solids removed from the filter element by the scraper element are discharged manually or automatically from the filter device. The discharge can in this case be at least partially supported by the existing in the filter device overpressure compared to the atmospheric pressure. For this purpose, the filter housing can have a collecting section with a closable outlet, in which the solid particles removed by the self-cleaning process are collected. By opening the closable outlet, the collected solid particles can be drained from the filter device.

In a particularly preferred embodiment, the solids removed from the filter element by the scraper element are timed and / or controlled by a differential pressure control from the filter device automatically discharged. For this purpose, for example, an automatically operable valve, in particular a solenoid valve may be provided at the outlet of the collecting section, which can be opened in a time-controlled or differential-pressure controlled manner for discharge. As a result, no manual interventions by an operating personnel are necessary for discharging the solid particles removed from the filter element during the self-cleaning process.

The solids separation effected by the filter device can take place immediately after the outlet of the reactor or preferably in the conveying direction of the coal sludge after at least one heat exchanger which removes heat from the coal sludge. The filtering should also be carried out in the conveying direction before the drying and dewatering device, i. still in the aqueous or viscous state of coal sludge. Preferably, the filtration is carried out after the heat exchanger, since there a lower temperature and a lower pressure of the coal slurry allow improved filtration.

The invention further relates to a device for the hydrothermal carbonization of biomass in transit for the production of biochar with at least one reactor in which the biomass is dehydrated and carbonated, wherein the at least one reactor has an outlet for removal of the coal sludge resulting from the carbonization. The device is characterized in that following the outlet in the conveying direction of the coal slurry following a filter device is provided, which is designed for the solids separation of particles larger than a defined particle size from the coal sludge. The filter device is designed to filter out particles larger than 5 mm, in particular larger than 10 mm.

Preferably, the filter device is immediately after the outlet of the reactor or after provided at least one heat exchanger. Preference is given to the provision of the filter device after the heat exchanger, since there allow the lower temperature and the lower pressure of the coal slurry improved filtration.

Particularly preferably, the filter device is a self-cleaning filter device. Thereby, an improved flow of coal slurry through the filter device is made possible because the filter cake settling on the filter element is removed without manual intervention of the operating personnel.

Further preferably, the filter device is constructed in several parts and has at least one filter element and at least one scraper element, wherein the filter element relative to the scraper element or the scraper element relative to the filter element is relatively movable for self-cleaning of the filter device. The scraper element is preferably at least partially against the filter element and removed by the relative movement of the elements to each other the filter cake. This can be done a simple and efficient cleaning of the filter device.

The filter element is at least partially hollow cylinder-shaped, wherein the scraper element is formed at least partially to the inner and / or outer side abutment against the lateral surface of the filter element. The use of a hollow-cylindrical filter element results in a filter surface which is optimized in size with respect to the volume or the size of the filter device, so that the throughput of the filter device is optimized. In addition, the filter element formed in this way can very easily be freed from the filter cake forming on the hollow cylinder outside by means of the scraper element.

Preferably, the filter element relative to the scraper element or the scraper element relative to the filter element is designed to be movable, by a motor, pneumatic or hydraulic drive. Particularly preferably, the filter element is rotatably mounted relative to the scraper element. This represents a preferred embodiment, in particular when using a hollow-cylindrical filter element, since the filter element is rotationally symmetrical and thereby a structurally simple and space-saving self-cleaning of the filter device is possible when using the axis of symmetry as a rotation axis.

In a preferred embodiment, the filter device has a collecting section for the solids removed by the doctoring element, wherein a manual or a time and / or differential pressure controlled automated discharge of the solids collected in the collecting section is provided. For this purpose, for example, an automatically operable valve, in particular a solenoid valve may be provided at the outlet of the collecting section, which can be opened in a time-controlled or differential-pressure controlled manner for discharge. As a result, no manual interventions by an operating personnel are necessary for discharging the solid particles removed from the filter element during the self-cleaning process.

The term "essentially" in the context of the invention means deviations from the respective exact value by +/- 10%, preferably by +/- 5% and / or deviations in the form of changes insignificant for the function.

Further developments, advantages and applications of the invention will become apparent from the following description of the embodiment and from the figures. In this case, all described and / or illustrated features alone or in any combination are fundamentally the subject of the invention, regardless of their summary in the claims or their dependency. Also, the content of the claims is made an integral part of the description.

The invention will be explained in more detail using an exemplary embodiment in conjunction with the figures. Show it:

1 an example of a device according to the invention for the hydrothermal carbonization of biomass with a single reactor in a schematic representation;

2 by way of example a schematic longitudinal sectional view of a filter device for use in the inventive method and apparatus according to the invention.

In the 1 is with the reference numeral 1 a hydrothermal carbonation (HTC) plant. The attachment 1 is here designed to perform an HTC process as a continuous process, ie, that the plant 1 a continuous or quasi-continuous operation when introducing the biomass into the reactor or when removing the coal from the reactor 5 without completely interrupting the carbonisation process inside the reactor.

The in the plant 1 Processed biomass, which in particular can be dry biomass with a solids content of ≥ 30%, becomes a biomass task 2 in the plant 1 introduced and by means of a conveyor 3 controlled or temporally intermittent preheating 4 fed. The conveyor 3 In this case, a screw conveyor, a conveyor belt, a push floor conveyor or biomass with a high water content may also be a pump. In the preheating device 4 , which is preferably a pressure-resistant, apart from the supply and discharge lines closed container, the biomass is heated, by directly introducing the Dehydratwassers into the biomass and by mixing the Dehydratwassers with the biomass, the dehydrated water at least partially by dehydration in the reactor 5 arises. This water has a temperature in the range between 180 ° C and 240 ° C and can be used optimally for heat input into the previously to be heated biomass due to its high specific mass. When supplying the Dehydratwassers is preferably the preheating 4 sealed pressure-tight.

To remove the dehydrated water from the reactor 5 is preferably in between the upper and the lower reactor section 5a . 5c lying middle reactor section 5b , a withdrawal facility 5.1 provided, via which the dehydrated water can preferably be controlled controlled by at least one valve and via an immediate fluidic connection of the preheater 4 can be supplied.

After the at least partial preheating of the biomass is preferably the pressure within the preheater 4 , which has already risen by the supply of Dehydratwassers, to a pressure at least equal to the pressure inside the reactor 5 increased, with pressures of 10 bar to 33 bar are preferred. The pressure increase takes place by means of a pressure generator 9 or one with the pressure generator 9 coupled pressure accumulator. After increasing the pressure in the preheater 4 The preheated biomass or the mixture of biomass with the dehydrated water through the inlet 5.2 the reactor 5 fed. In the event that in the preheater 4 the same pressure as in the reactor 5 prevails, the biomass is due to gravity in the reactor 5 brought in. An increase in the pressure in the preheating device is preferred 4 about the pressure in the reactor 5 so that clogging of the outlet of the preheater 4 or the inlet 5.2 of the reactor 5 effectively avoided.

After introducing the biomass into the reactor 5 This biomass is subjected to the hydrothermal carbonization, whereby water molecules are split off from the biomass in the dehydration process and thereby coal particles are formed, located in the lower reactor section 5a deposit.

In a preferred embodiment, the biomass introduced into the reactor is likewise added to catalysts which bring about acidification or alkalization of the biomass, the degree of addition of such catalysts determining the structure of the resulting coal particles. Furthermore, by suitable addition of catalysts, the carbonation process can be accelerated.

From the outlet 5.3 of the reactor 5 an aqueous coal slurry is removed, which is used for residual heat utilization via a heat exchanger 10 to be led. About the heat exchanger 10 In this case, the coal sludge is at least partially deprived of the heat energy contained therein. This heat energy becomes a heat storage 11 supplied so that it acts as an intermediate buffer for the extracted heat energy. The cooling of the biomass simultaneously reduces the pressure of the biomass compared to the ambient pressure.

The coal slurry is then passed through a filter device 8th guided, preferably the heat exchanger 10 is provided downstream, so that the already at least largely cooled coal sludge the filter device 8th flows through it while the impurities contained in the coal sludge are deposited. Such foreign substances may be contained in the biomass plastics, metals, etc. Preferably, a further impurity sorting in the field of biomass task 2 or the conveyor 3 intended to be sorted out by means of coarse foreign substances from the biomass to be processed. The through the filter device 8th Filtered coal slurry becomes a drying and dewatering device 12 fed, in which the coal slurry is converted into dust-like coal particles or coal dust. This coal dust can either be injected directly into a storage facility or fed to a pelletizer in which the carbon particles are crosslinked by the addition of starch, in particular corn and / or potato starch and pressed into pellets.

Depending on the biomass used, the liquid produced during the dewatering process can either be used directly as a fertilizer or precipitated and used when using phosphate-containing or heavy metal-containing biomass, so that these phosphates and heavy metals are at least largely removed from the liquid. Part of the drying and dewatering device 12 liquid withdrawn from the coal slurry can continue to be used in-process and to the pressure generator 9 be supplied, so that the liquid for increasing the pressure in the preheater 4 can be used.

Preferably, this is the plant 1 with a heater 13 connected, for example, a biomass furnace, a combined heat and power plant or a fossil Fuel using heater may be. The from the heater 13 resulting gases, in particular flue gases are the reactor 5 or the reactors 5 . 5 ' over flue gas pipes 13.1 fed. Inside the reactors 5 . 5 ' each is at least one heat exchanger 6 provided, which is in particular a tube heat exchanger and a plurality of preferably vertically arranged tube elements 6.1 has, with the flue gas pipes 13.1 are connected and flowed through by the flue gas. This causes heating of the biomass or liquid contained in the interior of the reactor. After flowing through the heat exchanger 6 the flue gases from the reactors 5 . 5 ' guided and preferably a heat exchanger 7 supplied by means of the flue gas residual heat energy is withdrawn and the heat storage 11 is supplied.

Preferred is in the flue gas ducts 13.1 between the heater 13 and the reactors 5 . 5 ' a mixing device is provided which allows a mixing of the flue gas with a controlled amount of cold air or fresh air. As a result, the flue gas temperature or the heat input into the reactors 5 . 5 ' over the heat exchanger 6 controlled. The required heat input into the reactors 5 . 5 ' depends significantly on the biomass used or the dry content of this biomass, with biomass with a higher dry content requires a lower heat input than biomass with an increased dry content. Due to the controlled supply of flue gas the respective required heat demand can be taken into account depending on the processed biomass.

2 shows a filter device 8th that can be used to filter coal sludge. The filter device 8th consists essentially of a housing 8.6 that a first connection 8.4 for the feed line of the coal sludge and a second connection 8.5 for the course of the coal sludge. The connections 8.4 . 8.5 are over a filter element 8.1 fluidly coupled together, ie the coal sludge must flow through the filter device 8th from the first connection 8.4 to the second connection 8.5 the filter element 8.1 happen. This filter element 8.1 has a variety of openings 8.1.1 on whose opening size is greater than 100μm, preferably greater than 500μm. Thus, particles that are larger than this opening size, through the filter device 8th be filtered out.

The filter element 8.1 des preferably has a hollow cylindrical shape, wherein on the cylinder jacket surface, the openings 8.1.1 are provided. This is the filter element 8.1 flows through from the outside to the inside. The filtered particles deposit on the outside of the filter device and form a filter cake. This filter cake is at least temporarily and / or depending on operating parameters, for example, at certain intervals or controlled by a pressure difference measurement removed by a self-cleaning process, so that clogging of the filter device is effectively prevented.

In the embodiment shown, the hollow cylindrical filter element 8.1 rotatably in the housing 8.6 the filter device 8th held and can via a drive 8.7 around the cylinder vertical axis HA of the filter element 8.1 be set in rotary motion. The filter element 8.1 lies in the upper area on the outer circumference against an annular sealing element 8.8 so that a direct transfer of coal sludge from the first port 8.4 to the second connection 8.5 without passing the filter element 8.1 is prevented. Against the outside of the filter element 8.1 is also a scraper element 8.2 at the during the rotational movement of the filter device 8.1 on the outside of the filter element 8.1 scrapes and thereby removes the deposited filter cake. This will make the openings 8.1.1 of the filter element 8.1 released again, allowing the flow of the filter device 8th is improved.

The housing 8.6 points in the area below the filter element 8.1 a catching section 8.3 on, for receiving the from the scraper element 8.2 worn filter cake is used. The catchment section 8.3 has an outlet for emptying it 8.3.1 on, through the opening of the filtered particles can be discharged. At this outlet 8.3.1 is preferably a valve 8.3.2 provided for the emptying of the collecting section 8.3 can be opened. The emptying can be done manually or automatically, in particular via a solenoid valve, which is opened time-controlled or controlled by a differential pressure measurement.

The invention has been described above by means of an embodiment. It is understood that numerous modifications and changes are possible without departing from the inventive concept.

LIST OF REFERENCE NUMBERS

1

HTC plant

2

biomass task

3

Conveyor

4

preheater

5

reactor

5a

lower reactor section

5b

middle reactor section

5c

upper reactor section

5.1

removal device

5.2

inlet

5.3

outlet

6

heat exchangers

6.1

tube element

7

heat exchangers

8th

filtering device

8.1

filter element

8.1.1

opening

8.2

scraper element

8.3

capturing section

8.3.1

outlet

8.3.2

Valve

8.4

first connection

8.5

second connection

8.6

casing

8.7

drive

8.8

sealing element

9

pressure generator

10

heat exchangers

11

heat storage

12

Drying and dewatering device

13

heater

13.1

Flue gas line

HA

vertical axis

Claims (17)

Process for the hydrothermal carbonization of biomass in transit, in which biomass is conveyed through a conveyor ( 3 ) at least one reactor ( 5 ), in which the biomass is dehydrated and carbonated, and in which the carbonaceous sludge resulting from the carbonization is fed to at least one outlet ( 5.3 ) from the reactor ( 5 ), characterized in that the coal sludge after the outlet ( 5.3 ) by a filter device ( 8th ) is guided, which is designed for the solids separation of particles larger than a defined particle size. Method according to claim 1, characterized in that the filter device ( 8th ) is at least temporarily cleaned in a self-cleaning process. Method according to claim 1 or 2, characterized in that the filter device ( 8th ) comprising at least one filter element ( 8.1 ) and at least one scraper element ( 8.2 ) by relative movement of the at least one scraper element ( 8.2 ) relative to the at least one filter element ( 8.1 ) or by relative movement of the at least one filter element ( 8.1 ) relative to the at least one scraper element ( 8.2 ) is cleaned. Method according to one of the preceding claims, characterized in that the filter device ( 8th ) at least one hollow cylindrical filter element ( 8.1 ), which is traversed by the carbon slurry from the hollow cylinder outside to the hollow cylinder inside. A method according to claim 3 or 4, characterized in that a to the filter element ( 8.1 ) form-adapted scraper element ( 8.2 ) motor-driven, pneumatically or hydraulically driven at least in sections along the outside ( 8.1a ) of the filter element ( 8.1 ) or that the filter element ( 8.1 ) driven by a motor, pneumatically or hydraulically with respect to the scraper element ( 8.2 ) is moved. Method according to one of claims 3 to 5, characterized in that for self-cleaning of the filter device ( 8th ) the filter element ( 8.1 ) relative to the scraper element ( 8.2 ) is rotated. Method according to one of claims 3 to 6, characterized in that the of the filter element ( 8.1 ) by the scraper element ( 8.2 ) removed solids manually or automatically from the filter device ( 8th ). A method according to claim 7, characterized in that the of the filter element by the scraper element ( 8.2 ) timed and / or controlled by the pressure difference between the pressure of the coal sludge before the filter device ( 8th ) and the pressure of the coal sludge after the filter device ( 8th ) controlled from the filter device ( 8th ). Method according to one of the preceding claims, characterized in that the solids separation by the filter device ( 8th ) immediately after the outlet ( 5.3 . 5.3 ' ) of the reactor ( 5 . 5 ' ) or after at least one of the coal sludge heat withdrawing heat exchanger ( 10 ) he follows. Device for the hydrothermal carbonization of biomass in transit with at least one reactor ( 5 ) in which the biomass is dehydrated and carbonated, the at least one reactor ( 5 ) an outlet ( 5.3 ) for the removal of coal sludge resulting from the carbonization, characterized in that on the outlet ( 5.3 ) in the conveying direction of the coal slurry following a filter device ( 8th ) is provided, which is designed for the solids separation of particles greater than a defined particle size from the coal sludge. Apparatus according to claim 10, characterized in that the filter device ( 8th ) immediately after the outlet ( 5.3 ) of the reactor ( 5 ) or after at least one heat exchanger ( 10 ) is provided. Apparatus according to claim 10 or 11, characterized in that the filter device ( 8th ) is a self-cleaning filter device. Device according to one of claims 10 to 12, characterized in that the filter device ( 8th ) is constructed in several parts and at least one filter element ( 8.1 ) and at least one scraper element ( 8.2 ), wherein for self-cleaning of the filter device ( 8th ) the filter element ( 8.1 ) relative to the scraper element ( 8.2 ) or the scraper element ( 8.2 ) opposite the filter element ( 8.1 ) is relatively movable. Device according to claim 13, characterized in that the filter element ( 8.1 ) is at least partially hollow cylinder-shaped and the scraper element ( 8.2 ) at least in sections to the inner and / or outer side abutment against the lateral surface of the filter element ( 8.1 ) is trained. Apparatus according to claim 13 or 14, characterized in that the filter element ( 8.1 ) relative to the scraper element ( 8.2 ) or the scraper element ( 8.2 ) opposite the filter element ( 8.1 ) is designed to be movable, by a motor, pneumatic or hydraulic drive. Device according to one of claims 13 to 15, characterized in that the filter element ( 8.1 ) relative to the scraper element ( 8.2 ) is mounted rotatably. Device according to one of claims 13 to 16, characterized in that the filter device ( 8th ) a collecting section ( 8.3 ) for the scraper element ( 8.2 ) has removed solids and a time-controlled and / or a differential pressure-controlled discharge of the in the collecting section ( 8.3 ) is provided solids.

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