EP0148871A1

EP0148871A1 - A process and an apparatus for chemical treatment of bulky organic materials, such as straw and other biomass, with volatile chemicals

Info

Publication number: EP0148871A1
Application number: EP84902445A
Authority: EP
Inventors: Aksel Thorkild Bentsen; Mikael Kau; Torsten Reffstrup
Original assignee: Bioteknologisk Institut
Current assignee: Bioteknologisk Institut
Priority date: 1983-06-23
Filing date: 1984-06-25
Publication date: 1985-07-24
Also published as: AU3067484A; WO1985000133A1; DK290383D0

Abstract

Traitement chimique de matériaux organiques en vrac, notamment de paille et d'autres biomasses, par des produits chimiques volatiles, tels que NH3, SO2, HF, HCl, qui sont ajoutés aux matériaux avant, pendant ou après une compression (semi)continue, notamment dans une presse à piston (1) ou dans une extrudeuse, le mélange de réaction restant enfermé dans une chambre de réaction (6) à une température et à une pression élevées pendant une période de temps suffisante pour provoquer la conversion désirée du matériau. Grâce à ce traitement, la paille peut être convertie en une pulpe facilement digestible ou en des produits fibreux destinés à être utilisés dans la production de papier ou de carton, ou subir un traitement préalable pour compléter l'hydrolyse avec un acide aqueux ou des enzymes.Chemical treatment of loose organic materials, especially straw and other biomass, with volatile chemicals, such as NH3, SO2, HF, HCl, which are added to the materials before, during or after (semi) continuous compression, in particular in a piston press (1) or in an extruder, the reaction mixture remaining enclosed in a reaction chamber (6) at an elevated temperature and pressure for a period of time sufficient to cause the desired conversion of the material. Thanks to this treatment, the straw can be converted into an easily digestible pulp or into fibrous products intended for use in the production of paper or cardboard, or undergo a preliminary treatment to complete the hydrolysis with an aqueous acid or enzymes. .

Description

A process and an apparatus for chemical treatment of bulky organic materials, such as straw and other biomass, with volatile chemicals

The invention relates to a process for chemical treatment of bulky organic materials, such as straw and other biomass, with volatile chemicals at an elevated temperature, and an apparatus for performing the process.

Examples of useful volatile chemicals include: NH,, SO₂, HF, HCl, HBr, HI, O₂, Cl₂, CIO₂, O₃, CO, H₂, CO₂ and H₂S, alone or in mutual mixture or in mixture with specifically catalytically acting substances.

The treatment may e.g. aim at decomposing straw and similar cellulose-rich by-products with anhydrous hydrogen fluoride with a view to utilization of the released sugar components e.g. as a livestock feed additive or fermentation crude material, or by subsequent hydrolysis to produce monomeric glucose or xylose, or with ammonia to increase the feed digestibility thereof, or with sulfur dioxide to provide a fibre product which is suitable as a component in paper, cardboard, cartridge paper and sheet articles.

An immediate advantage of the use of volatile chemicals is the extremely easy recovery of unreacted reactant, which evaporates by pressure relief and/or heating and can then be recycled in a simple manner by absorption in untreated material, optionally after condensation or absorption in water or the like. A further advantage consists in the possibility of working with a relatively dry material, which minimizes the energy costs of heating the material and frequently also of drying the end product. All the processes for treating biomasses with volatile chemicals and gases described in the past are vitiated by one or more of the following drawbacks:

1. Disuniform dispersion of the reactant on the material, which it has been attempted to remedy by long reaction periods, great excess of chemicals or performance in vacuum.

2. Problems of transfer of the necessary heat, partly to ensure rapid reaction, partly to ensure evaporation of the reactant after completed reaction, because in the past mixtures of lignocellulosic biomasses containing so small amounts of chemicals that the mixture remains a poor heat conductor could not be heated effectively in a short time.

3. By treatment with anhydrous hydrogen fluoride. Problems of crust formation and poor ingress of the hydrogen fluoride, which it has been attempted to remedy by pre-hydrolysis to remove preferably pentosanes, requiring subsequent drying before the treatment with the volatile reactant.

The DE Patent Specification 585 318 discloses a process for treating plant materials with gaseous hydrogen fluoride, which comprises absorbing hydrogen fluoride in the plant material in a first zone of a container, preferably at a low temperature, and decomposing the material in a second zone at a suitable temperature, and expelling the hydrogen fluoride in a third zone by heating or ejection or both, and recycling the hydrogen fluoride to the first zone to act on fresh material. Instead of one container, several interconnected containers may be used, corresponding to their respective zones, and the hydrogen fluoride may be diluted with inert gases. This process has the advantage that it can be carried out continuously, but apart from this it is vitiated by all the drawbacks stated under the above points 1-3.

H. Bergner: "Chemische Grundlagen des Strohaufschlusses in der Pelletierpresse", Arch. Tierernahrung, Berlin 1980, Bd. 30, H 1/2/3, p. 239-256, discloses a process for decomposing straw, which comprises admixing chopped straw with ammonia water or an aqueous solution of ammonium hydrogen carbonate or urea, and treating the mixture in a pelletizer press, subjecting it to a pressure of 10 to 20 MPa and a following temperature increase of up to 110°C during a residence time of about 25 sec. (p. 248). However, it will be seen from table 6 (p. 253) that the straw is admixed with 15% sliced feed (dried beet slices sprayed with molasses), and the pelletization of ammonia-treated straw can in reality only be carried out after addition of such a lubricant binder as, otherwise, no sufficient pressure can be formed. As a matter of fact, it appears from table 6 that the stated digestibilities include this sliced feed as the digestibility of untreated pure straw is 27 to 30%.

The difference in table 6 between the digestibility after treatment with NH₃ water, NH₄HCO₃ and urea and the digestibility without chemical corresponds very well to the nutritional increase of 15 to 20%, which is stated on p. 250, 2nd paragraph. But the obtained increases in digestibility are too small and show an inadequate conversion of the straw, which must i.a. be ascribed to the very short residence time in the pelletizer press.

The object of the invention is to provide a process for chemical treatment of bulky organic materials with volatile chemicals which is not vitiated by the abovementioned drawbacks of the known processes and which can be performed semi-continuously or continuously to provide high yields and with a possibility of recovering the volatile reactant. The object is moreover to provide an apparatus for performing the process.

The process of the invention is characterized by compressing the material in the absence of liquid water phase in a semi-continuously or continuously operating compressing means and feeding said material from said means into a reaction chamber in which, in the presence of the volatile chemical, it is kept enclosed and heated for a period of time sufficient to cause the intended conversion of the material.

In the process of the invention, a volatile chemical, which must have a certain solubility in the material to be treated or moisture contained in it, is added to the material before or after (semi) continuous compression of the material in a compressing device, preferably a piston press or an extruder. This eliminates headspace, i.e. air gaps, in which gaseous chemicals would otherwise accumulate and be barred from exerting their effect, in particular at a high temperature where the solubility at atmospheric pressure is poor. Moreover, the compression contributes to heating by internal friction in the material so that a desired increase in temperature is obtained. This also produces increased partial pressure of a given gas amount, ensuring great solubility and concentration in the material. The above-mentioned measures result in a great chemical activity and consequently a high reaction rate by addition of a relatively small amount of a volatile chemical to a given amount of bulky organic material, such as straw, wood flour or other biomass. However, it is not critical that the total heat supply takes place in the press or by internal friction in the feed means to the reaction chamber. The temperature in the reaction chamber may also be increased additionally e.g. by injection of steam, by conduction through the chamber walls, by electromagnetic radiation, such as through microwaves or by ohmic or inductive heating, etc.

The volatile chemical, including the recovered chemical, is preferably added by absorption in the bulky organic material in a mixer before feeding into the compression means, but may also be injected directly into the reaction chamber.

According to the type of the volatile chemical, it may be added in a liquid state, in a gas state or dissolved in a solvent from which it readily evaporates. For example it is necessary that the process is a dry one, i.e. with dried organic material and anhydrous chemicals, if HF and HCl are to evaporate sufficiently from the treated material, and therefore HF is used preferably in an anhydrous liquid state or gas state, and HCl preferable in a gas state. On the other hand, the process may very well be a wet one, i.e. with wet material, but in the absence of liquid water phase, with e.g. NH₃ and SO₃, and these are therefore preferably used as an aqueous solution or as a gas.

Depending upon the used volatile chemical, the reaction mixture is heated to 80 to 250°C, preferably 100 to 190°C. At these temperatures, the volatile chemical is substantially present as a reactive gas, and for the desired temperature to be maintained it may be advantageous that the heating in the reaction chamber takes place at an elevated gas pressure. Such an elevated pressure may be 1 to 60 bar gauge pressure. In the process of the invention it is particularly advantageous to heat the reaction mixture sufficiently to evaporate most of the non-chemically bound volatile reactant after completed reaction.

An advantageous embodiment of the process of the invention consists in performing it in a closed system with a lock device for the product after the reaction chamber and recovering the non-chemically bound volatile reactant after completed reaction and recycling it to treat fresh organic material, optionally after condensation or absorption in water or the like.

To treat bulky organic material with ammonia the process of the invention is performed particularly expediently in that the material is admixed with ammonia water in an amount which adds to the material at least 3% by weight of ammonia, based on dry matter, and does not contain more water than can be absorbed in the material, and is then compressed in a piston press, from which the reaction mixture is fed by the piston strokes into a reaction chamber in which it is heated by injection of steam and kept enclosed and heated for a sufficient period of time to cause the intended conversion of the material with, the ammonia. If desired, gaseous ammonia may moreover be injected into the reaction chamber. The reaction chamber preferably contains a conveying means whose velocity is so adapted to the velocity of the piston press that the reaction chamber is kept completely filled with the reaction mixture, which is given an adequate residence time in the reaction chamber to cause the intended reaction of the material with the ammonia.

I f the react ion chamber has a discharge opening to the atmosphere, it is possible to maintain an elevated gas pressure and thus a temperature of between 100 and 110°C in the vicinity of the steam injection at the feed end, while the temperature will drop to the range of 80. to 100°C at the discharge opening.

If the reaction chamber is provided with a lock means to maintain an elevated gas pressure in the reaction chamber, it is possible to maintain a constant temperature of 100 to 190°C or more in the reaction chamber.

To treat bulky organic material with hydrogen fluoride the process of the invention is performed particularly expediently by impregnating the material, after drying to a water content of maximum 5% by weight, with at least 30% by weight of anhydrous, liquid or gaseous HF, based on dry matter, with spontaneous heating and then compressing it in an extruder, from which the reaction mixture in the form of a plastic mass is pressed through a reaction chamber with a narrow cross-section in one dimension and with external heating, in which it is kept enclosed and heated for a sufficient period of time for the hydrogen fluoride to cause the intended conversion of the material. By compression and heating to temperatures in the range of 80 to 120°C the reaction mixture becomes a plastic mass which can be pressed through the reaction chamber by the extruder pressure alone. Thus, no conveying means in the reaction chamber and no measures for maintaining an elevated gas pressure are required.

When the reacted plastic mass emerges from the outlet slit, it spontaneously releases HF so that it becomes sufficiently brittle to allow grinding. An advantageous feature in connection with the embodiment of the invention described here is accordingly that the product is ground and kept heated for evaporation of substantially all the hydrogen fluoride.

The HF treated product thus obtained may be subjected to subsequent hydrolysis in an aqueous acid medium or by means of enzymes to provide glucose and xylose in a good yield.

The apparatus of the invention for chemical treatment of bulky organic materials, such as straw and other biomass, with volatile chemicals is characterized in that it comprises a semi-continuously or continuously operating compressing means connected with a reaction container adapted to keep the mixture of compressed material and chemical enclosed and heated for a period of time sufficient to cause the intended conversion of the material.

The compressing means may e.g. be selected from among piston presses, worm extruders, ring matrix presses, hydraulic presses and continuous roller systems. However, it is also possible to combine the compressing means and the reaction container in the form of a continuous plate press with heated pressing planes or a system of co-acting, material-enclosing belt systems with heating of the belts.

The apparatus of the invention can advantageously also comprise a mixing means for mixing finely divided organic materials and chemicals in connection with the compressing means.

In the drawing:

Fig. 1 shows an embodiment of an apparatus according to the invention intended for treatment of bulky organic materials with ammonia;

Fig. 2 shows an embodiment of an apparatus according to the invention for treatment of bulky organic materials with hydrogen fluoride.

In Fig. 1 the organic material is continuously introduced into the feed chamber 2 of a piston press 1 and is sprayed with ammonia water through a supply line 3. The mixture is compressed in the nozzle 4 and moved by the piston stroke into a reaction container 6 in which steam and ammonia gas are injected through a supply line 5. The mixture is conveyed through the reaction chamber by a conveyor worm 7 and discharged through a discharge opening 8. The discharge opening can advantageously communicate with an escape means (not shown) to maintain an elevated gas pressure and thus a high constant temperature through the entire reaction container.

In Fig. 2 the organic material impregnated with HF is continuously introduced into a worm extruder 9, in which it is compressed by a worm 10 extended with a cylindrical mandrel 11 which protrudes into a transition member 12 connecting the extruder 9 with a reaction container, and which terminates just in front of an inlet opening to a reaction chamber 14 disposed between two heating jackets 13 in the reaction container. The reaction mixture, which has become a plastic mass by the impact of compression and heat, is pressed by the extruder worm 10 out through the transition member 12 round the displacement mandrel 11 and further through the reaction chamber 14 where its reaction is completed under heating from the heating jackets 13. The reacted product emerges from an outlet slit 15 provided with a slit width regulator 16 to regulate the counterpressure in the reaction chamber. The following exampels serve to illustrate the invention more fully; examples 1 and 2 show an increase in the digestibility of straw by continuous treatment with NH₃, and examples 3 and 4 show continuous pre-treatment of barley straw with HF with a view to subsequent complete hydrolysis with aqueous acid.

EXAMPLE 1

Chopped barley straw with a moisture content of 15% is mixed with 12555 of 25.0 ammonia water and 6% αf water in a mixing chamber which terminates in the entry to a piston press with a 5 cm nozzle. The reaction mixture is compressed in the piston press and conveyed by the piston strokes into a cylindrical reaction chamber with a diameter approximately 5 times as great, provided with a conveyor worm.

In the reaction chamber a mixture of steam and gaseous ammonia is moreover injected adjacent to the mouth of the piston press, thereby heating the material to 100 to 110°C. The piston press and conveyor worm rates are so adapted that the reaction chamber is kept completely filled with material without the presence of liquid water phase, and the residence time in the reaction chamber is about 7 min., during which period the temperature drops to 80 to 90°C at the opening to the atmosphere.

The enzyme digestibility of the treated straw was increased from 27% to 42%. by the experiment described here. When the NH₃-treated straw was allowed to afterreact in an insulated container at 90 to 93°C for an hour, the enzyme digestibility of the material was increased to 46%, and when additionally left to stand at the same temperature for an hour the enzyme digestibility was increased to 50%. EXAMPLE 2

The process is identical with the one described in example 1, with the difference that the reaction chamber is provided with a lock device, and that such a great gas pressure is maintained in the reaction chamber that the temperature is constantly in the range of 100 to 120°C during a residence time of about 10 min. This gives NH₃-treated straw with an enzyme digestibility of about 45% in a continuous flow.

EXAMPLE 3

2 kg of chopped and dried barley straw ( 2% water content) are impregnated in a plastics bag with 800 g (40% by weight) of liquid HF. During impregnation the reaction mixture is spontaneously heated to 55 to 60°C, and the effective volume of the mixture falls to about 1/5. The straw thus impregnated forms a flowing product which is fed to a worm extruder, where the worm is extended with a cylindrical ring mandrel and the worm housing is provided with a transition member guiding the compressed straw mass to a reaction chamber in which the HF-treated straw is heated additionally. By compression and heating the HF-containiπg straw becomes a plastic mass which is moved by the compression worm pressure alone through the reaction chamber with a residence time of 2 min.

At a temperature in the compression zone of 70 to 75°C and in the reaction chamber of 110 to 120°C the straw product is obtained as a black paste which becomes brittle upon spontaneous evaporation of HF and appears as a black-brown powder with an HF content of 1 to 1.5% of the straw dry matter quantity after grinding and additional evaporation of HF in an oven at 60 to 80°C.

Subsequent hydrolysis with 1.5% sulfuric acid at 104°C for 30 min. released 312. of the straw dry matter as glucose and 152. of the straw dry matter as xylose.

EXAMPLE 4

In an enclosure of HF resistant material, provided with stirring, were placed 400 g of dry, beater ground barley straw. From an adjacent container in which 160 g of anhydrous HF were placed, the air was circulated between the two containers, and the HF gas was absorbed in the straw within 30 minutes.

The HF impregnated material appeared as a dry, flowing product, which was converted to a black-brown powder after compression, heating, degassing of HF and grinding like in example 3.

Subsequent hydrolysis like in example 3 gave a yield of glucose of 32% and a yield of xylose of 17% based on straw dry matter.

Claims

P A T E N T C L A I M S

1. A process for chemical treatment of bulky organic materials, such as straw and other biomass, with volatile chemicals at an elevated temperature, c h a r a c t e r i z e d by compressing the material in the absence of liquid water phase in a serai-continuously or continuously operating compressing means and feeding said material from said means into a reaction chamber in which, in the presence of the volatile chemical, it is kept enclosed and heated for a period of time sufficient to cause the intended conversion of the material.

2. A process according to claim 1, c h a r a c t e r i z e d by adding the volatile chemical before or during the compression of the material.

3. A process according to claim 1, c h a r a c t e r i z e d by adding a volatile chemical to the reaction chamber.

4. A process according to claim 1, c h a r a c t e r i z e d in that the reactive gas is selected from among NH₃, SO₂, HF, HC1, HBr, HI, O₂, Cl₂, ClO₂, O₃, CO, H₂, CO₂ and H₂S.

5. A process according to claim 1, c h a r a c t e r i z e d in that the compressing means is a piston press or an extruder.

6. A process according to claim I, c h a r a c t e r i z e d by heating the reaction mixture to 80 to 250°C, depending upon the volatile chemical used.

7. A process according to claim 1, c h a r a c t e r i z e d by heating the reaction mixture to 100 to 190°C.

8. A process according to claim 1, c h a r a c t e r i z e d in that the volatile chemical is a reactive gas, and that the heating in the reaction chamber is effected at an elevated pressure.

9. A process according to claim 8, c h a r a c t e r i z e d by maintaining a gauge pressure of 1 to 60 bars in the reaction chamber.

10. A process according to claim 1, c h a r a c t e r i z e d by heating the reaction mixture sufficiently for most of the non-chemically bound volatile reactant to evaporate after the reaction.

11. A process according to claim 1, c h a r a c t e r i z e d by performing it in a closed system with a lock device for the product after the reaction chamber and recovering the non-chemically bound volatile reactant after completed reaction and recycling it to treat fresh organic material, optionally after condensation or absorption in water or the like.

12. A process according to claim 1 for treatment of bulky organic materials with ammonia, c h a r a c t e r i z e d in that the material is admixed with ammonia water in an amount which adds to the material at least 3% by weight of ammonia based on dry matter, and not more water than can be absorbed in the material and is then compressed in a piston press, from which the reaction mixture is fed by the piston strokes to a reaction chamber in which it is heated by injection of steam and which contains a conveying means whose velocity is so adapted to the velocity of the piston press that the reaction chamber is kept completely filled with the reaction mixture, which is given a sufficient residence time in the reaction chamber to cause the intended conversion of the material with the ammonia.

13. A process according to claim 12, c h a r a c t e r i z e d by additionally injecting gaseous ammonia into the reaction chamber.

14. A process according to claim 12, c h a r a c t e r i z e d by maintaining a temperature of 80 to 110°C in the reaction chamber, the temperature being 100 to 110°C at the feed end.

15. A process according to claim 12, c h a r a c t e r i z e d in that the reaction chamber is provided with a lock device to maintain ari elevated gas pressure, and that a constant temperature of 100 to 190°C is maintained in the reaction chamber.

16. A process according to claim 1 for treatment of bulky organic materials with hydrogen fluoride, c h a r a c t e r i z e d by impregnating the material, after drying to a water content of maximum 5% by weight, with at least 30% by weight of anhydrous, liquid or gaseous HF, based on dry matter, with spontaneous heating and then compressing it in an extruder, from which the reaction mixture in the form of a plastic mass is pressed through a reaction chamber with a narrow cross-section in one dimension and with external heating, in which it is kept enclosed and heated for a sufficient period of time for the hydrogen fluoride to cause the intended conversion of the material.

17. A process according to claim 16, c h a r a c t e r i z e d by maintaining a temperature of 80 to 120°C in the reaction chamber.

18. A process according to claim 16, c h a r a c t e r i z e d by grinding the product and keeping it heated for evaporation of substantially all the hydrogen fluoride.

19. A process according to claim 16, c h a r a c t e r i z e d by subjecting the product to hydrolysis in an aqueous acid medium or by means of enzymes.

20. An apparatus for chemical treatment of bulky organic materials, such as straw and other biomass, with volatile chemicals, c h a r a c t e r i z e d in that it comprises a semicontinuously or continuously operating compressing means connected with a reaction container adapted to keep the mixture of compressed material and chemical enclosed and heated for a period of time sufficient to cause the intended conversion of the material.

21. An apparatus according to claim 20, c h a r a c t e r i z e d in that the compressing means is selected from among piston presses, worm extruders, ring matrix presses, hydraulic presses and continuous roller systems.

22. An apparatus according to claim 20, c h a r a c t e r i z e d in that the compressing means and the reaction container are combined in the form of a continuous plate press with heated pressing planes or a system of co-acting, material-enclosing belts with heating of the belts.

23. An apparatus according to claim 20, c h a r a c t e r i z e d in that it further comprises a mixing means for mixing finely divided organic material and chemicals in connection with the compressing means.

24. An apparatus according to claim 20 for treatment of bulky organic materials with ammonia, c h a r a c t e r i z e d in that it comprises a piston press whose nozzle terminates at one end of a cylindrical reaction container which is provided with introduction means for steam for heating and optionally for gaseous ammonia and with a conveyor worm for conveying the reaction mixture from the mouth of the nozzle to a discharge opening at the opposite end of the reaction container.

25. An apparatus according to claim 24, c h a r a c t e r i z e d in that the discharge opening of the reaction container communicates with a lock device to discharge the product while retaining an elevated gas pressure in the reaction container..

26. An apparatus according to claim 20 for treatment of bulky organic materials with hydrogen fluoride, c h a r a c t e r i z e d in that it comprises a worm extruder whose outlet leads into a reaction container which has an internal reaction chamber with a narrow cross-section in one dimension and a heating jacket on each side of the reaction chamber.