WO2014183768A1

WO2014183768A1 - Feed vessel

Info

Publication number: WO2014183768A1
Application number: PCT/DK2014/050132
Authority: WO
Inventors: Mogens JUHL FØNS; Torben Bonde
Original assignee: Biofuel Technology A/S
Priority date: 2013-05-13
Filing date: 2014-05-13
Publication date: 2014-11-20

Abstract

Method for the pre-treatment of ligno-cellulosic material by hydrothermal hydrolysis or thermo chemical hydrolysis, where shredded or otherwise finely divided biomass material is introduced batch-wise into an upper part of a reactor vessel through an inlet, such that the batch being introduced lands on top of a batch previously introduced into the reactor, thereby creating a column of biomass material, where the lowermost batch and thereby the column is supported inside the reactor by upper restriction means, and when the lowermost batch has been exposed to the desired treatment with respect to temperature, pressure and time, the upper restriction means are withdrawn allowing the biomass to fall downwards to be supported by lower restriction means, at which time the upper restriction means are reinserted, such that biomass material corresponding to one batch is arranged between upper and lower restriction means, and thereafter the lower restriction means are withdrawn, allowing the lowermost batch material to fall towards and exit the reactor through an outlet, where said inlet is provided with an inlet valve and said outlet is provided with an outlet valve such that the reactor vessels interior may be opened and closed by manipulating said valves with respect to the ambient environment.

Description

Feed Vessel

Field of the Invention

The present invention relates to a method of pre-treatment of ligno-cellulosic material by hydrothermal hydrolysis or thermochemical hydrolysis.

Background of the Invention

In the field of deriving ethanol from ligno-cellulosic materials such as for example straw it has long been an established procedural step to pre-treat the ligno-cellulosic material before said material is entered into the reactor where the ethanol is created and distilled. The whole exercise of converting ligno-cellulosic biomass to ethanol primarily comprises the hydrolysis of ligno-cellulosic structure to fermentable sugars followed by a fermentation and finally distillation of the fermented slurry. The hydrolysis of ligno-cellulosic material into fermentable sugars is a critical stage which is a main component in the overall process efficiency.

Generally, two different types of devices and processes, i.e. two main principles, have been used in the pre-treatment of the ligno-cellulosic material.

A first principle incorporates a vertical plug flow reactor where the material due to the influence of gravity flows downwards through the vertical plug flow reactor. "Plug" refers to the fact that batches of ligno-cellulosic material is introduced into the reactor such that inside the reactor the biomass will have a, at least in theory, layer structure such that each batch will constitute a layer, also called a plug. As new plugs are entered at the top of the flow reactor, the entire biomass inside the reactor moves downwards, when the lowermost plug is evacuated after the desired process time has been obtained.

The second main principle comprises a horizontal cooker where the material is moved horizontally through the cooker by means of typically paddles or other means of transporting the biomass inside the cooker. For both types, i.e. the vertical plug flow reactor and the horizontal cooker, it is necessary in order to achieve a sufficient heating and thereby opening of the fibres' cells in the biomass material that a substantial amount of water is used.

Typically, 80% of all pores and cavities in straw from for example wheat have a diameter of approximately 0.8 nm or less. It is therefore extremely difficult to make sure that all cells, pores and cavities are water filled and thereby exposed to the treatment in the pre-treatment process. Therefore, a substantial amount of water is required to assure a thorough and even heating of the biomass material. The water - biomass mix is referred to as slurry. Typically the biomass used in both of the above-mentioned methods requires that the slurry, i.e. the mix of ligno-cellulosic material and water, has a dry matter content of only approx. 20%. Furthermore, it is assumed that the material before being entered into the pre-treatment process has been shredded, chipped or in another manner been reduced in size in order to expose as much of the surfaces as possible.

During the pre-treatment process the slurry, i.e. a combination of water and dry matter, is typically heated such that the process is carried out at temperatures in the range of typically 150-220°C. Often, enzymes or other chemicals are added in order to improve the hydrolysis, i.e. the separation of sugars from either the complex sugars or from the lignin in the ligno-cellulosic material.

In WO 2009 012779 an apparatus is disclosed having a relatively high moisture/water content in order to enable the slurry, i.e. the combined material, to flow through the plug flow reactor. This naturally requires high thermal energy consumption in order to elevate the temperature of the entire slurry into the process temperature range of 150-220°C.

If the water content was reduced in either of the two main principles, i.e. a vertical plug flow reactor or the horizontal cooker, this would cause congestion and stoppage inside both process devices. In the vertical plug flow reactor the outlet valve would be congested in that the slurry material would form a bridge/firm plug and block the discharge point as typically the cross-sectional area of the main pre-treatment vessel decreases towards the discharge point. The same is true for the horizontal cooker where the means for transporting inside the cooker first of all would have an increased load to carry, but also at the same time the discharge point would be congested due to the viscosity of the slurry mass.

Also for both pre-treatment devices the valves being used to open and close the discharge point wold have a substantial wear in that the valve would have to cut off the slurry stream from the reactor to further processing.

Object of the Invention

Consequently, it is the object of the present invention to provide a solution and improvements to the processes and devices mentioned above and provide an improved method using less energy, creating less wear and with an increased yield.

Description of the Invention

The invention provides this by a method for the pre-treatment of ligno-cellulosic material by hydrothermal hydrolysis or thermo chemical hydrolysis, where shredded or otherwise finely divided biomass material is introduced batch-wise into an upper part of a reactor vessel through an inlet, such that the batch being introduced lands on top of a batch previously introduced into the reactor, thereby creating a column of biomass material, where the lowermost batch and thereby the column is supported inside the reactor by upper restriction means, and when the lowermost batch has been exposed to the desired treatment, the upper restriction means are withdrawn allowing the biomass to fall downwards to be supported by lower restriction means, at which time the upper restriction means are reinserted, such that biomass material corresponding to one batch is arranged between upper and lower restriction means, and thereafter the lower restriction means are withdrawn, allowing the lowermost batch material to fall towards and exit the reactor through an outlet, where said inlet is provided with an inlet valve and said outlet is provided with an outlet valve such that the reactor vessels interior may be opened and closed by manipulating said valves with respect to the ambient environment.

Due to this process and in particular the fact that upper and lower restriction means are provided it is possible to dose the material which is to be evacuated from the reactor vessel such that clogging, congestion etc. is avoided in the outlet means. Thereby it becomes possible to substantially lower the amount of liquid, typically water, which needs to be added to the dry matter in order to achieve the high temperature in all the cells/pores of the ligno-cellulosic material in order to pre-treat the ligno-cellulosic material making available the sugar content for the further processing and fermentation in the ethanol deriving process. Water is also added in order to create a slurry which can be moved through the process system.

The batch material introduced into the reactor vessel will contrary to what is known in the art not be a slurry, but be more in the shape of a granular loose material and as set out in a further advantageous embodiment of the invention the dry matter portion of the material introduced into the reactor vessel will be 50-75%. Therefore, the lowermost batch retained by the lowermost restriction means will after the uppermost restriction means has been inserted again in order to retain the stack of batches, i.e. plugs, be removed whereby a substantially loose material will drizzle and drift towards the outlet.

In a further advantageous embodiment the valves are opened and closed at predetermined times in the process according to a predetermined program stored in a control unit. Especially, in a preferred embodiment sets out that the outlet valve is opened while there is pressure inside the reactor vessel, and the inlet valve is only opened when the pressure inside the vessel has reached a lower pressure.

In this manner the material released by the lowermost restriction means will due to the pressure difference between the inside of the reactor vessel and the downstream production facility be sucked out due to the pressure difference, and thereby any tendency to build up a plug, congestion or the like in the outlet means, i.e. the outlet valve, are effectively avoided.

At the same time the pressure difference will facilitate a very quick removal of the material for further processing.

Once the lowermost outlet valve has been opened, pressure inside the reactor vessel will equalize with the ambient pressure, and at this point the inlet valve may be open in order to introduce new material, i.e. a new batch position on top of the uppermost batch in the stack of biomass material inside the reactor. Once the batch is in place, both the upper and lower valves are closed, and the heating means are activated, typically in the shape of injection of steam whereby both the temperature and the pressure will increase inside the reactor vessel.

The temperature and pressure will facilitate the access to the sugars stored in the biomass material, such that the fermentation process following the pre-treatment will be more effective. By having a very high dry matter content, typically 50-75% of the material introduced into the reactor vessel the necessary thermal energy needed to heat the material to the desired process temperature which typically is in the interval 150°C-250°C is achieved with much less energy due to the very reduced water content which needs to be heated. This in turn reduces the reaction time inside the pre- treatment vessel, and as such the overall method may be carried out faster and with less energy consumption.

The invention is also directed to an apparatus for the pre-treatment of ligno-cellulosic material by hydrothermal hydrolysis or thermochemical hydrolysis according to the method of claim 1, where said apparatus comprises a substantially vertical reactor vessel, said reactor vessel being suitable to be exposed to a pressure, where inlet means and an inlet valve are arranged in an upper part of said vessel, and where outlet means and an outlet valve are arranged in a lower section of said vessel, where heating means is provided for heating the interior of the vessel, and where upper and lower restriction means are arranged inside the reactor vessel, where said restrictor means are arranged with a mutual vertical distance, and where the restrictor means are moveable between a retracted position where the restrictor means does not interfere with the vessel's cross section and an engaged position where the restrictor means substantially obstructs the vessel's cross section.

The apparatus for pre-treatment is specifically designed such that it will achieve the advantages described above with reference to the inventive method.

One particular embodiment of the inventive apparatus shall be emphasized in this context, namely the embodiment where the vessel is provided with means for accommodating said restrictor means inside the pressurized part of the reactor vessel. By this arrangement the reactor vessel's wall is not penetrated by the restriction means and as such expensive and sensitive pressure secure seals are not necessary when operating the restrictor means. This in turn facilitates the construction of a more stable apparatus in that the pressure tightness and the integrity of the apparatus and thereby the long life and reliability is ensured. This must also be seen in combination with the fact that as opposed to prior art devices using a slurry the inlet and outlet valves are, due to the characteristics of the materials used within the present invention, i.e. having a relatively high dry matter content, will never be obstructing the inlet or outlet valves, and as such the wear on these valves will be negligible ensuring a very long service life, as opposed to prior art processes using a slurry where the in- and outlet valves will have to break of (i.e. interfere in) a continuous slurry stream..

Further advantageous embodiments are described in the further dependent claims.

Description of the Drawing

The invention will now be explained with reference to the accompanying drawings in which

Figure 1 illustrates an apparatus suitable for carrying out the method according to the present invention

Figure 2 illustrates an example of the restrictor means

Figure 3 illustrates an alternative embodiment of the reactor vessel

Detailed Description of the Invention

In figure 1 is schematically illustrated an apparatus suitable for carrying out the method according to the present invention. The apparatus 1 comprises a substantially vertically arranged reactor vessel 2 where the reactor vessel 2 is suitable to be exposed to a pressure. The pressure typically arises from the heat treatment to which the ligno-cellulosic material is exposed and preferably the heat treatment is obtained by injecting steam into the reactor vessel 2.

The reactor vessel 2 has inlet means with an inlet valve 5 arranged in an upper part of the vessel 2 as well as outlet means and an outlet valve 6 arranged in a lower section of the vessel 2. Although the heating means are advantageously in the shape of steam other heating means such as for example infrared heating sources or microwaves may also be contemplated within the present invention. Furthermore, upper a lower restriction means 9, 10 are provided inside the reactor vessel. The restrictor means 9, 10 are arranged at a predetermined mutual vertical distance 8. The restrictor means 9, 10 are movable between a retracted position (not illustrated) and an engaged position as illustrated in figure 1.

The movement of the restriction means 9, 10 is illustrated by the arrows 9a, 10a. The restrictor means 9, 10 will be explained in more detail with reference to figures 2a, b and c.

When using the apparatus 1 as illustrated in figure 1 in a method according to the present invention the biomass material 1 1 is introduced into the pressure vessel, for example through a feeding vessel 4. The biomass material, i.e. the ligno-cellulosic material is fed through the inlet valve 5 in a batch- wise fashion, such that the biomass material inside the reactor vessel 2 will have a layered structure as illustrated by the dashed lines separating the layers or plugs 11 '-1 l^vl. Each batch in this manner constitutes a substantially separate plug 11 '-1 l^vl and by arranging the restrictor means 9, 10 at vertical distance 8 roughly corresponding to the thickness of a plug, it is ensured that by manipulating the restrictor means as will be explained below each plug will have the same process time inside the pre-treatment reactor vessel 2 and a limited amount of material will be removed from the reactor vessel 2.

Removal of material having reached the desired condition, i.e. having been exposed to temperature pressure in order to liberate the surfaces of the material thereby providing access to sugars is released from the biomass material 11 inside the reactor vessel by removing the lowermost restriction means 10 such that the material in the plug 11 ' will fall down towards the bottom part 12 of the reactor vessel 2. By further opening the outlet valve 6 the higher pressure inside the vessel 2 will force the granular/shredded relatively dry material out through the outlet valve 6 in this instance being collected in a collection tank 14 before being conveyed on to fermentation and release of sugars etc.

Once the restrictor means 10 has been withdrawn the plug 11 ' will fall downwards due to the influence of gravity as explained above. Thereafter, the restrictor means 10 is reinserted in the position illustrated in figure 1. Be removing the upper restrictor means 9 the entire stack of plugs 11 will move downwards, such that a new lowermost plug will be resting on the lowermost restrictor means 10 thereby being the new plug 11 ' . During this process the outlet valve 6 may be opened such that the pressure inside the vessel is more or less equalized. The outlet valve 6 may also have been closed after the desired amount of material has been released in order not to waste pressure/heat and thereby energy inside the reactor vessel. Tests clearly indicate that the biomass column as illustrated in figure 1 will move downwards irrespective of the pressure inside the vessel. However, when the outlet valve 6 is open, the pressure inside the reaction vessel 2 will be dramatically reduced. It will therefore be possible to open the inlet valve 5 in order to introduce a new batch of material on top of the already existing stack of plugs inside the reactor valve. The feed vessel may also be pressurized at a desired pressure such that a pressure equilibrium is established between the feed and pre-treatment vessels.

Turning to figure 2 an example of the restrictor means 9, 10 is illustrated. In this embodiment the restrictor means comprises a plurality of bars 20 which as explained with reference to figure 1 may be moved in and out of engagement as illustrated by the arrows 9a, 10a. In the embodiment illustrated in figure 2 the restrictor means 20 are in the shape of substantially round bars, but any cross-section of the bars may be used, and in further embodiments the bars may be replaced by paddles such that one or more paddles may create the necessary blockage in order to hinder the plugs 11, see figure 1, in moving downwards through the reactor vessel.

In figure 3 is illustrated an alternative embodiment of the reactor vessel 2' where the pressurized volume 19 inside the pressurized vessel 2' has been designed to accommodate the restriction means 9', 10' . In this manner no sensitive seals or couplings need to be provided in the wall of the pressurized reactor vessel which eventually would fail and thereby reduce the service life of the reactor vessel 2' and thereby the entire apparatus.

Claims

1. Method for the pre-treatment of ligno-cellulosic material by hydrothermal hydrolysis or thermo chemical hydrolysis, where shredded or otherwise finely divided biomass material is introduced batch-wise into an upper part of a reactor vessel through an inlet, such that the batch being introduced lands on top of a batch previously introduced into the reactor, thereby creating a column of biomass material, where the lowermost batch and thereby the column is supported inside the reactor by upper restriction means, and when the lowermost batch has been exposed to the desired treatment, the upper restriction means are withdrawn allowing the biomass to fall downwards to be supported by lower restriction means, at which time the upper restriction means are reinserted, such that biomass material corresponding to one batch is arranged between upper and lower restriction means, and thereafter the lower restriction means are withdrawn, allowing the lowermost batch material to fall towards and exit the reactor through an outlet, where said inlet is provided with an inlet valve and said outlet is provided with an outlet valve such that the reactor vessels interior may be opened and closed by manipulating said valves with respect to the ambient environment or alternatively where the lowermost batch and thereby the column is supported inside the reactor by restriction means, and when the lowermost batch has been exposed to the desired treatment, the restriction means are withdrawn allowing the biomass of the lowermost batch to fall towards and exit the reactor through an outlet, where said inlet is provided with an inlet valve and said outlet is provided with an outlet valve such that the reactor vessels interior may be opened and closed by manipulating said valves with respect to the ambient environment or alternatively that when the lowermost batch has been exposed to the desired treatment, the upper restriction means are withdrawn allowing the biomass to fall downwards to be supported by the lower restriction means, at which time the upper restriction means are reinserted, such that biomass material corresponding to one batch is arranged between upper and lower restriction means, and thereafter the lower restriction means are withdrawn, allowing the lowermost batch material to fall towards and exit the reactor through an outlet and where after the lowermost batch has been allowed to fall downwards, the lower restriction means are inserted again.

2. Method according to claim 1 wherein when the valves are opened and closed at predetermined times in the process according to a predetermined program stored in a control unit.

3. Method according to claim 2 wherein the outlet valve is opened while there is pressure inside the reactor vessel, and the inlet valve is only opened when the pressure inside the vessel has reached a lower pressure.

4. Method according to claim 1 or 2 where the upper and/or lower restriction means are bars being arranged perpendicularly to the vertical axis of the vessel, and where means are provided for inserting and retracting said bars, such that the bars either extends across the entire cross-section of the vessel or are substantially withdrawn from the cross-section.

5. Method according to any preceding claim where the process time for the lowermost batch of material is between 1 and 30 minutes, where the temperature inside the vessel is between 150°C and 250°C and the pressure is up to 8 bars.

6. Method according to claim 1 where the batch material introduced into the reactor vessel comprises 50% to 75% dry matter.

7. An apparatus for the pre-treatment of ligno-cellulosic material by hydrothermal hydrolysis or thermochemical hydrolysis according to the method of claim 1, where said apparatus comprises a substantially vertical reactor vessel, said reactor vessel being suitable to be exposed to a pressure, where inlet means and an inlet valve are arranged in an upper part of said vessel, and where outlet means and an outlet valve are arranged in a lower section of said vessel, where heating means is provided for heating the interior of the vessel, and where upper and lower restriction means are arranged inside the reactor vessel, where said restrictor means are arranged with a mutual vertical distance, and where the restrictor means are moveable between a retracted position where the restrictor means does not interfere with the vessel's cross section and an engaged position where the restrictor means substantially obstructs the vessel's cross section.

8. Apparatus according to claim 7, where the heating means is a source of steam.

9. Apparatus according to claim 7 or 8 wherein the vessel is provided with means for accommodating said restrictor means inside the pressurized part of the reactor vessel.

10. Apparatus according to any preceding claim wherein each restrictor means is in the shape of a plurality of bars arranged in parallel and in one plane or where the restrictor means is in the shape of a plate member where the upper and lower restrictor means may be freely chosen as one or the other.