WO2018058162A1

WO2018058162A1 - Carrying out hydrothermal carbonization reactions in an extruder

Info

Publication number: WO2018058162A1
Application number: PCT/AT2017/060239
Authority: WO
Inventors: Christoph Pfeifer; Gregor TONDL
Original assignee: Universität Für Bodenkultur
Priority date: 2016-09-27
Filing date: 2017-09-27
Publication date: 2018-04-05
Also published as: AT519208B1; AT519208A1

Abstract

The invention relates to the use of an extruder, which comprises an extruder cylinder (1), at least one extruder screw (2) arranged therein, a feed inlet (3) for supplying biomass as feed, a water inlet (4), and a nozzle (6) for dispensing reaction products, for carrying out hydrothermal carbonization reactions. The invention is characterized in that a) a cooled section (5) is provided in the extruder cylinder (1) after the opening (3) of the feed when seen in the flow direction as a condensation barrier for condensing steam; and either b1) a second cooled section (8) which is used as an additional condensation barrier is provided upstream of the outlet (7) of the extruder nozzle (6) in order to keep process water within the extruder or b2) the extruder nozzle (6) opens into a pressure tank (9) in which the hot reaction mixture guided in the extruder is brought to a lower pressure, whereby the process water evaporates and is thus separated from the reaction products in the reaction mixture in the pressure tank (9).

Description

IMPLEMENTATION OF HYDROTHERMALES

CARBONIZATION REACTIONS IN AN EXTRUDER

The present invention relates to the implementation of hydrothermal syntheses, more specifically to the implementation of hydrothermal carbonization reactions ("HTC").

STATE OF THE ART

Hydrothermal carbonization is a chemical process for the simple production of peat-like material called charcoal or "hydrochar" by charring biomass under hydrothermal conditions, ie in the presence of water at temperatures of typically about 180-220 ° C and pressures of 10-25 bar , whereby the running in the natural brown coal formation ("coalification") processes are technically mimicked. HTC has a whole host of benefits. On the one hand, the carbon efficiency in the conversion of biomass into fuels is usually quite low (about 67% for alcoholic fermentation, about 50% for anaerobic digestion to biogas and about 30% for charring wood for the production of charcoal). By contrast, almost all of the carbon contained in the biomass can be used by HTC for fuel production. Furthermore, the reaction is highly exothermic (with a reaction enthalpy for cellulose of about -300 kJ / mol), which not only results in low energy consumption, but also about one third of the (dry) biomass contained in the calorific value already released during the carbonation and as Waste heat is available, resulting in a total positive energy balance. In addition, artificial humus can be produced in this way, which can be used for soil improvement for plant growth. The produced hydro coal can be used as a carrier for nutrients and fertilizer and causes in the soil on the one hand water storage due to the porosity of the coal and on the other hand serves as carbon source. However, it can also be assumed that there is a long-term carbon sink of several decades or centuries in the soil. Finally, the resulting solid product can also be used for the production of fuel cells, carbon nanostructures or for later gasification and combustion. For carrying out HTC reactions, pressure reactors, such as Parr reactors, are required, and for continuous operation, tubular reactors are preferably used, including, more recently, also extruders. Thus, WO 2014/145731 A1 discloses the use of a twin-screw extruder in which biomass is fed as feed material, as best illustrated in the FIG. 5A therein, which is reproduced herein as FIG. A fed via a hopper 40 in the extruder 80 Biomassefeed is added via a water inlet 60 with hot water, which was previously heated in a boiler 50 to temperatures above 300 ° C, with pressures of over 200 bar arise. The extruder cylinders 85 may be independently cooled and heated to control the HTC reactions occurring therein before the HTC product exits the extruder at the end of the cylinders.

The disadvantage of this embodiment is, on the one hand, that only a relatively low throughput can be achieved, and, on the other hand, that the reaction products sometimes have a very high water content, which makes them unsuitable for use as fuels, for example, so that an additional drying step is required. The aim of the invention was to provide an improved process for the production of HTC products such as hydro coal using an extruder.

DISCLOSURE OF THE INVENTION

This object is achieved by the present invention by providing the use of an extruder comprising an extruder barrel, at least one extruder screw disposed therein, a feed inlet for supplying biomass as feed, a water inlet and a nozzle for discharging reaction products, for carrying out hydrothermal carbonization reactions License plate that

a) in the extruder cylinder after the mouth of the feed, viewed in the direction of flow, a cooled section is provided as a condensation barrier for condensing water vapor; and b1) a second, provided as a further condensation barrier cooled section is provided in front of the outlet of the extruder die to keep the process water within the extruder; and or

b2) the extruder nozzle opens into a pressure tank, in which the guided in the extruder, hot reaction mixture is brought to a lower pressure, whereby the process water is evaporated and thus separated in the pressure tank from the reaction products in the reaction mixture.

In this way, the reaction products are freed from most of the process water already on their exit from the extruder, so that in most cases no additional drying step needs to be carried out. Depending on the water content of the biomass used as a feed, different reaction routes are to be preferred. To biomass already having a very high water content, e.g. above 50%, as is the case with sewage sludge, manure or the like, it may not be necessary to add additional water in order to give the biomass a suitable consistency for the HTC reactions. Such a feed is metered directly into the extruder, preferably by means of a pump, and a return of the water by means of the first or only condensation barrier in the extruder is prevented.

Whether a second condensation barrier is also provided at the end of the extruder again depends on the water content of the biomass. When the water content is very high, it is advantageous to remove the water continuously, for which purpose a combination of features a) and b2) is to be preferred, which allows a completely continuous reaction. At low water content, a certain amount of water is usually added to the biomass, which is why in preferred embodiments of the invention in a separate, optionally heatable, mixing vessel prepared an aqueous solution, suspension or slurry of biomass and fed as feed into the extruder. In this case too, it is possible to work in a completely continuous manner by continuously withdrawing the process water from the reaction products by means of a combination of a) and b2). The completed Process water separated according to the present invention is preferably recycled to the mixing vessel and reused to produce fresh biomass solution, suspension or slurry. In cases where the biomass either has a medium high water content such that no or only a small amount of water is to be added, the present invention may consist of a combination of feature a) and feature b1), so that the water due to the effect the second condensation barrier is kept in the reactor for a certain time, so as to adjust a desired consistency or viscosity of the biomass, before it is discharged from the extruder by switching off the cooling of the second cooled section together with the reaction products, which is a semi-continuous or even continuous process depending on whether the reaction product discharged intermittently together with the process water is discarded or subjected to a drying step and recovered.

In certain preferred embodiments, according to the present invention, both feature b1) and feature b2) can be realized, wherein again by switching off the cooling of the second cooling section serving as a condensation barrier, the process water can be intermittently discharged from the extruder, but always enters the pressure tank together with the reaction products, where it is readily separated from the latter and is particularly preferably recycled again. In this way, in turn, consistently and continuously, a substantially dry product is obtained, which can be used, for example, as a fuel.

Preferably, the extruder is a single screw extruder because at high water content of the biomass, eg above 50% or even above 70%, and correspondingly low viscosity of the reaction mixture in the extruder, the slip of a twin screw extruder would be too high to allow continuous delivery of the reaction mixture to care. According to the present invention, the interior of the cylinder in which the hydrothermal carbonization reactions take place is preferably subdivided into a plurality of reaction zones which can be heated and / or cooled separately from one another in order to specifically run different reactions therein. As a result, the method according to the invention can be adapted more flexibly to a varying biomass feed.

The heating of the reaction zones is preferably carried out electrically, the cooling, however, preferably by means of oil and / or water cooling. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in more detail below by means of specific embodiments and with reference to the accompanying drawings, which show the following:

Fig. 1 is an illustration of a prior art extruder used to carry out HTC reactions;

Fig. 2 is an illustration of a comparatively simple embodiment of the present invention;

Fig. 3 shows a pressure tank connected to an extruder according to the present invention;

Fig. 4 shows another embodiment of the present invention; and

Fig. 5 is an illustration of a particularly preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is based on the idea of controlling the whereabouts of the process water contained in the HTC process. The inventors have found that it is necessary to provide a condensation barrier between the feed inlet and the reaction zone (s) of the extruder, at which point the steam can be rejected. If this is to be kept entirely within the extruder for a certain time, then another condensation barrier at the end of the extruder cylinder or shortly before is required. On the other hand, however, the water can also be drained together with the HTC product, as long as immediately there is a separation of the water vapor to obtain low water content products or even substantially dry HTC products.

2 shows an illustration of a comparatively simple embodiment of the invention and shows an extruder cylinder 1 with an extruder screw 2, a feed inlet 3, which simultaneously serves as water inlet 4, since both are fed to a mixing container 10, mixed and - here: depressurized - be introduced into the extruder. The biomass feed comes from a storage container 14, from which it reaches the mixing container 10 by means of a further screw conveyor (indicated by arrows).

The extruder barrel 1 is subdivided over its length into four reaction zones Z1 to Z4, and the bars 5 and 8 symbolize the abovementioned condensation barriers serving as vapor barriers. Barrier 5 is realized in the example shown here concretely in that zone 1 by means of outer and inner cooling jackets, with the cooling liquid, here: water, via lines 5a and 5b at a significantly lower temperature, e.g. 70 ° C, is held as the three downstream reaction zones Z2 to Z4. In fact, zone Z1 serves as condensation barrier 5 in this case.

However, all four reaction zones Z1 to Z4 are also equipped with an electric heater, and the zones Z2 to Z4 are provided via lines 13 with a different cooling medium, such as e.g. Oil, cooled, in order to be able to control the temperatures in it exactly and at a higher level than in zone Z1. The reaction mixture is conveyed further by means of rotation of the screw 2 and finally reaches the extruder nozzle 6 together with the outlet 7, where at the latest the second condensation barrier 8 (shown here only diagrammatically) would have to be provided. This can be done, for example, by cooling the extruder die 6 itself or by providing another cooled section, e.g. another cooled reaction zone, take place immediately in front of the nozzle 6.

Alternatively, the process water of the present invention may be discharged from the extruder 1 at the die head 7 together with the generated HTC product if the mixture immediately thereafter enters a pressure tank 9 in which the reaction mixture is allowed to expand and be reduced to a lower pressure, whereby the process water is evaporated and separated from the HTC products. Such an arrangement is shown schematically in Fig. 3, wherein the looped arrow symbolizes the separated water vapor.

FIG. 4 shows a preferred embodiment of the invention which is similar to that in FIG. Again, a cooled zone Z1 serving as a condensation barrier 5 is provided. The second condensation barrier 8 is missing in this representation, since the reaction mixture passes analogously to FIG. 2 into a (not shown here) pressure tank 9. In contrast to Fig. 2, the feeding of the feed, i. However, in the embodiment of Fig. 4 is not depressurized, but via a pump 1 1 and a pressurized hopper 15, which allows higher throughputs than in non-pressurized feed supply of prepared in the mixing vessel 10 mixture of biomass and water. Finally, FIG. 5 shows a particularly preferred embodiment of the invention, in which again the feed supply takes place under pressure via pump 11 and filling funnel 15, and finally the mixture passes into a pressure tank 9. In contrast to FIG. 4, however, here a zone cooled twice by means of cooling liquid at 5a and 5b is provided as condensation barrier 5 upstream of the first reaction zone Z1, the cooling water from 5a cooling only the additional zone 5, while that from FIG. 5b also cooling of reaction zone Z1 is used. The zones Z2 to Z4, however, are again cooled only by means of oil via line 13.

Above all, however, in the embodiment shown here, the water vapor separated from the HTC products in the pressure tank 9 can be recycled into the mixing container 10, which is advantageous especially in the case of the carbonization of biomass with a low water content.

Claims

1 . Use of an extruder, comprising an extruder barrel (1), at least one extruder screw (2) arranged therein, a feed inlet (3) for feeding biomass as feed, a water inlet (4) and a nozzle (6) for discharging reaction products, for discharge hydrothermal carbonation reactions, characterized in that

a) in the extruder cylinder (1) after the confluence (3) of the feed, seen in the flow direction, a cooled section (5) is provided as a condensation barrier for condensing water vapor; and either

b1) in front of the outlet (7) of the extruder nozzle (6) a second cooled section (8) serving as a further condensation barrier is provided in order to keep the process water within the extruder; or

b2) the extruder nozzle (6) opens into a pressure tank (9) in which the hot reaction mixture led into the extruder is brought to a lower pressure, whereby the process water evaporates and separated in the pressure tank (9) of the reaction products in the reaction mixture becomes; or both.

2. Use according to claim 1, characterized in that both feature b1) and feature b2) are realized, wherein the cooling of the second, serving as a condensation barrier cooled section (8) can be switched off, whereby the process water each for a defined period of time within the Extruder is held, but intermittently drained from it.

3. Use according to claim 1 or 2, characterized in that in a separate, optionally heatable, mixing vessel (10) an aqueous solution, suspension or slurry of biomass produced and fed as a feed in the extruder.

4. Use according to claim 2 or 3, characterized in that the feed supply into the extruder by means of a pump (1 1) takes place.

5. Use according to one of claims 1 to 3, characterized in that the process water according to feature b2) separated from the reaction products, then recycled to the mixing vessel (10) and used there again for the production of fresh biomass solution, suspension or slurry.

6. Use according to one of claims 1 to 5, characterized in that the extruder is a single-screw extruder.

7. Use according to one of the preceding claims, characterized in that the interior of the cylinder (1) in which the hydrothermal carbonation processes take place is subdivided into a plurality of reaction zones (Z1 to Z4) which are separately heatable and / or coolable ,

8. Use according to claim 7, characterized in that the heating of the reaction zones (Z1 to Z4) takes place electrically.

9. Use according to claim 7 or 8, characterized in that the cooling of the reaction zones (Z1 to Z4) by means of oil and / or water cooling takes place.