Novel reactor system to produce microcrystalline cellulose

Abstract

A reactor system for producing microcrystalline cellulose (MCC) is disclosed. Further is disclosed a process for producing microcrystalline cellulose using the reactor system.

Description

[0001]NOVEL REACTOR SYSTEM TO PRODUCE MICROCRYSTALLINE CELLULOSE Technical fieldThe present disclosure relates to a reactor system for producing microcrystallinecellulose (MCC). In addition, the present disclosure relates to a process forproducing microcrystalline cellulose using the reactor system. Background Microcrystalline cellulose (MCC) is a particle like fiber product, originating from bio- based material containing crystalline cellulose. Microcrystalline cellulose is a purified, partially depolymerized cellulose prepared by treating alpha-cellulose, obtained as a pulp from fibrous plant material, with mineral acids. The degree of polymerization is typically less than 400. The particle size of MCC may typically be from 20 to 200 micrometer.Several methods have been described in the patent literature for producing MCC byusing different kinds of methods (alkali, acid, enzyme, hydrothermal), and reactor solutions.However, there is a need for a valorized reactor system to produce MCC where theproduct properties can be varied using simple process solutions, and wheredissolved part, which forms during the MCC reaction, is fractioned, and utilized inan efficient way. SummaryA reactor system for producing microcrystalline cellulose (MCC) is disclosed. Thesystem comprises: -a force circulation reactor 2 configured to hydrolyze a feed material 1a, 1bcomprising a biomaterial 1a and an active material 1b to produce MCC, and- a fractionation unit 4 configured to separate dissolved carbohydrates from theactive material and produce a carbohydrate stream 7, and- a process device 6 configured to circulate the active material 1b back to theforce circulation reactor 2 from the fractionation unit 4 for producing MCC. In addition, a process for producing microcrystalline cellulose using the reactor system is disclosed. Brief description of the drawings The accompanying drawings, which are included to provide a further understanding of the system of this specification, illustrate embodiments and together with the description help to explain the principles of the above. In the drawings:Fig. 1 shows an embodiment of the force circulation reactor system, where MCCproduct is manufactured.Fig. 2 shows a particle size distribution of MCC product, produced using the reactorsystem as disclosed in the current specification.Fig. 3 shows a particle size distribution of MCC product produced using the reactorsystem as disclosed in the current specification.Detailed descriptionA reactor system for producing microcrystalline cellulose (MCC) is disclosed. Thesystem comprises: -a force circulation reactor 2 configured to hydrolyze a feed material 1a, 1bcomprising a biomaterial 1a and an active material 1b to produce MCC, and- a fractionation unit 4 configured to separate dissolved carbohydrates l fromthe active material and produce a carbohydrate stream 7, and- a process device 6 configured to circulate the active material 1b back to theforce circulation reactor 2 from the fractionation unit 4 for producing MCC.The expression “dissolved carbohydrates” should be understood in this specification,unless otherwise stated as carbohydrates dissolved from the biomaterial. Thecarbohydrates dissolved from the biomaterial may include glucose, andhemicellulose, which comprises sugars such as xylan, mannose, galactose,rhamnose and arabinose. The active material may be circulated in the reactionsystem. The active material and dissolved carbohydrates may be lead from the forcecirculation reactor, through the fractionation unit. Then the active material may belead through the active material storage and then back to the force circulation reactor.The circulation of the active material has the added utility of enabling reusage of theactive material. It also provides efficient heat, mass and chemical transfer in thereactor system and it enables efficient fractionation of dissolved carbohydrates in thereactor system.The expression “force circulation reactor” should be understood in this specification,unless otherwise stated as a reactor that involves active, continuous circulation ofactive material driven by a process device. In a force circulation reactor, the activematerial may be actively circulated through the reactor and returned, to maintain uniform temperature and enhance mass transfer throughout the system.In one embodiment, the process device 6 is a pump. The process device 6produces necessary force to circulate the active material in the presented system. In one embodiment, a first process line 3 is configured to lead the active material and dissolved carbohydrates from the force circulation reactor 2 to the fractionation unit 4. In one embodiment, a second process line 5 is configured to lead the activematerial from the fractionation unit 4 to a process device 6.In one embodiment, a third process line 8 is configured to recover the MCC 11. In one embodiment, a fourth process line 9 is configured to lead the active materialfrom the process device 6 to the force circulation reactor 2.In one embodiment, the system further comprises an active material storage 13.The active material storage has the added utility of storing the active material andensuring that the active material is readily available when needed.In one embodiment, a fifth process line 12 is configured to lead the active materialfrom the fourth process line 9 to the active material storage 13 or lead the activematerial out from the system. In one embodiment, a process device 6 is configuredto circulate the active material 1b back to the force circulation reactor 2 from theactive material storage or from the fractionation unit 4 for producing MCC.In one embodiment, a sixth process line 14 is configured to lead the active materialfrom the active material storage 13 to the force circulation reactor 2.In one embodiment, the system comprises further process stages 10. In oneembodiment, the system comprises further process stages 10 configured to furtherprocess the MCC. In one embodiment, the third process line 8 is configured to lead the MCC furtherprocess stages 10 and a seventh process line 15 is configured to lead the activematerial from the further process stages 10 to the active material storage 13, to thefourth process line 9 or to the fifth process line 12. In one embodiment, the fractionation unit 4 is microfiltration unit, nanofiltration unit,ultrafiltration unit, reverse osmosis system, or membrane filtration unit.In one embodiment, the further process stages 10 include washing, bleaching,drying, and / or dry grinding. In one embodiment, the further process stages 10 includewashing unit, bleaching unit, drying unit, and / or dry grinding unit.The viscosity of the pulp material may be determined according to standard ISO53:31:2010. Degree of polymerization (DP) means relative polymerization length ofcellulose and it may be determined from intrinsic viscosity value according to SCAN-CM 15:88. The term “P-factor” means time temperature factor and it may bedetermined using the Handbook of pulp (2006) by Herbert Sixta.The term “D-ratio” means how narrow is the MCC’s particle size distribution. A smallvalue means that the size distribution is very narrow, and a high value means widedistribution. Commercial MCC product D-ratios are typically between 2.0 – 3.5.D-ratio is calculated: (d90 – d10) / d50, and different d-values refer to the sizedistribution d-values measured using laser diffraction method.The biomaterial 1a, typically bleached chemical pulp, may be shredded to a form ofpieces, or fed to the force circulation reactor 2 in a form of pulp sheet if dry rawmaterial is used. In the case of so-called pipe pulp, material may be densified before force circulation reactor 2 in a wash press on in a similar known pulp dewateringdevice to form fiber cake pieces which are fed to force circulation reactor 2.In one embodiment, the active material can be fed to the force circulation reactor 2simultaneously or sequentially in any order. In one embodiment, the biomaterial 1a isfed first and then the active chemical 1b is added. In one embodiment, after feedingof the biomaterial, such as chemical pulp 1a to force circulation reactor 2, activechemical 1b is fed to the system. In one embodiment, the active material 2 is an acid.In one embodiment, the acid is sulfur acid or hydrochloric acid. Acid type, and amountmay be chosen as disclosed in the patent publications WO2011154600 and / orWO2011154601. Thus, the amount of acid is typically from 0.2 to 10%, from 0.2 to5%, from 0.2 to 2% or from 0.5 to 1.5% on the dry weight of the cellulose.Suitable acids for the hydrolysis are both organic and inorganic acids. The organicacid may be a formic acid or an acetic acid. Preferred inorganic acids are mineralacids, such as sulfuric acid, sodium bisulfate, sodium bisulfite, hydrochloric acidand / or nitric acid.Hydrolysis process may start in force circulation reactor 2 by heating reactor solutionto an elevated temperature using direct or indirect heating system. Typically, heatingis done by using steam which is a general method in a known process industry. Whenthe heating process starts, active material may be circulated in the reactor system viathe first process line 3, through the fractionation unit 4, to the second process line 5,via process device 6, to the fourth process line 9 and back to the force circulationdigester 2. Thus, in the microcrystalline cellulose manufacturing system as disclosedin the current specification, the active material is moving, and solid pulp material staysin the reactor. Process device 6 controls flow amount of the active material in thereactor system. By increasing flow amount in the reactor system formation ofconcentration gradients is prevented. This enables very efficient hydrolysis process.Suitable hydrolysis conditions are disclosed in the patent publicationsWO2011154600 and / or WO2011154601. The hydrolysis temperature may typicallybe at least 80°C, at least 100°C, at least 125°C, between 100 to 185°C, 140 to 185°C,120 to 180°C, 150 to 180°C, 155 to 175°C or 120 to 160°C. The hydrolysis time istypically from 5 to 240 minutes, 5 to 180 minutes, or 15 to 150 minutes.After the heating of the reactor system, hydrolysis process may be started, the activematerial 1b, such as an acid, in the system reacts with the biomaterial 1a, such aschemical pulp. Some carbohydrate fractions are dissolved in an early stage of theprocess, and some later. So, the reactor solution flowing via the first process line 3 tothe fractionation unit 4 starts to consist dissolved carbohydrate components. Thefractionation unit 4 separates dissolved carbohydrates from the active material andproduces a carbohydrate stream 7. Fractionation could start in any stage of process, in the beginning to separate easily dissolved components, or in the end of process to separate all dissolved components. It is also possible to circulate the active materialin several hydrolysis cycles via active material storage in the reactor to increase concentration of the dissolved carbohydrates and after achieving an acceptable level,process it through the fractionation unit.When chemical pulp of certain degree of polymerization (DP) is reached, the pulp isthen hydrolyzed to MCC product. The degree of polymerization (DP) is typically below 450, or below 350 or under the level where cellulose fibers are broken down to particleform. Benefit of the reactor system as disclosed in the current specification is thepossibility to circulate reactor solution in the system having minimal flow resistance due to natural acid nature of the process even with the high packing degrees.The reactor system as disclosed in the current specification enables:- efficient circulation of active material in the reactor system,- reusage of the active material,- efficient heat, mass and chemical transfer in the reactor system,- efficient fractionation of dissolved carbohydrate in the reactor system,- and preventing need of any mechanical actions during the cooking likemixing, moving of cooked material, conveyer, etc.In the end of the hydrolysis, active material may be pumped via the fifth process line12 to the active material storage 13, to be used again to next hydrolysis via the sixthprocess line 14, or out from the system to be used elsewhere to other purposes.Formed MCC product may be processed via the third process line 8 to other processstages.It may also be possible to process MCC and the active material together out from thedigester chamber via the third process line 8 to the further process stages 10 andseparate the active material there, e.g., in the first washer, and process it back to thefourth process line 9, or to the active material storage 13 via the fifth process line 12.Further process stages 10 can include washing, bleaching, drying, dry grinding and / orother relevant stages to form ready product, pure white, free flowing MCC powder. The biomaterial used as a starting material in the process as disclosed in the currentspecification may be any cellulosic material that can be hydrolyzed under thespecified conditions. Thus, the cellulosic material does not necessarily have to be a pure cellulosic material. Suitable cellulose containing feed stock materials include, for example, bleached or unbleached wood pulps (such as, e.g., kraft pulp, sulfite pulp, neutral sulfite pulp, acid sulfite pulp, dissolving pulp, soda-AQ pulp or organosolv pulp, mechanical pulp, thermomechanical pulp (TMP), chemithermomechanical pulp(CTMP)) made from hardwood (e.g., different birch, eucalyptus and willow spieces)or softwood (e.g., different pine and spruce species), or made from agriculturallygrown cellulose containing plants and their by-products and residues (the by-products and residues including but not limited to hulls, husks, roots, straws, stems and peelings), or made from other non-wood annual plants (such as, e.g., cotton, grass, bagasse, hemp, flax, sisal, abaca or bamboo), cellulose containing waste streams (such as, e.g., used paper, paperboard, cardboard and cellophane), textile waste which contains cotton or other cellulose-based textile fibres (such as, e.g., viscoseand lyocell), and cellulose pulps made from side streams from food and beverageindustries (including but not limited to brewery spent grain, by-products from oat milkproduction and by-products from the grain mills). In one embodiment, the biomaterialis bleached chemical pulp. Due to the large variety of different suitable raw materials as disclosed in the currentspecification mechanical, pneumatical, thermal, hydrothermal or chemical pre- andafter-treatments or combinations of any of these may be used in conjunction with the system as disclosed in the current specification.The fractionation unit 4 may typically be a unit and / or a device which fractionates anddensifies dissolved carbohydrates. The fractionation unit may be an ultrafiltration unit, a nanofiltration unit, a membrane filtration unit, a centrifuge, a separator, achromatograph, and an ion exchange resin for carbohydrates.In one embodiment, the process for producing microcrystalline cellulose (MCC) comprises:- hydrolyzing a feed material 1a, 1b comprising a biomaterial 1a and an activematerial 1b to produce MCC in a force circulation reactor 2, and- separating dissolved carbohydrates from the active material and producing acarbohydrate stream 7, and- circulating the active material 1b back to the force circulation reactor 2 for producingMCC. EXAMPLES Reference will now be made in detail to the described embodiments, examples of which are illustrated in the accompanying drawings. The description below discloses some embodiments in such a detail that a person skilled in the art is able to utilize the system based on the disclosure. Not all steps of the embodiments are discussed in detail, as many of the steps will be obvious for the person skilled in the art based on this specification.Fig. 1 illustrates an example of the reactor system. The reactor system comprises aforce circulation reactor 2 configured to hydrolyze a feed material 1a, 1b comprisinga biomaterial and an active material to produce MCC. A first process line 3 leadsthe active material and dissolved carbohydrates of the biomaterial from the forcecirculation reactor 2 to a fractionation unit 4. The fractionation unit 4 is configuredto separate dissolved carbohydrates from the active material and produce acarbohydrate stream 7. Further, then a second process line leads the active materialfrom the fractionation unit 4 to a process device 6. The process device 6 isconfigured to circulate the active material in the reaction system. A third process line8 recovers the MCC 11. Then a fourth process line 9 leads the active material fromthe process device 6 to the force circulation reactor 2. A fifth process line 12 leadsthe active material from the fourth process line 9 to an active material storage 13 orleads the active material out from the system. A sixth process line 14 leads theactive material from the active material storage 13 to the force circulation reactor 2.Optionally, the system comprises further process stages 10, wherein the third process line 8 leads the MCC further process stages 10 and a seventh process line15 leads the active material from the further process stages 10 to the active materialstorage 13, to the fourth process line 9 or to the fifth process line 12. Fig 2. Illustrates a particle size distribution of MCC product, produced using the reactor system of as disclosed in the current specification. Fig. 3 Illustrates a particle size distribution of MCC product produced using the reactor system as disclosed in the current specification. Example 1 162.4 kg of bleached softwood kraft pulp was hydrolysed in a pilot scale force circulation reactor, having volume of 3.5m3. Acid amount loaded to hydrolysis was 2.5%, calculating from the cellulose oven dry amount. Active material, which was all the time circulating in reactor system having volume flow of 11m3 / h, was heated to 145°C, and kept there 44 minutes. Reactions consistency inside the reactor wasaround 5%. After reaction time, the active material was cooled down using heatexchanger system. Results was microcrystalline cellulose product having DP value166. Average particle size (d50-value) was 40 μm, d10-value 11 μm, and d90-value113 μm. So called d-ratio was 2.55. Particle size distribution of pilot scale MCChydrolysis is shown in Figure 2. Example 2Around 300 kg of bleached hardwood kraft pulp was hydrolyzed in a pilot scale forcecirculation reactor, having volume of 3.5m3. Acid amount loaded to hydrolysis was 2.0%, calculating from the cellulose oven dry amount. The active material, which was all the time circulating in reactor system having volume flow of 11m3 / h, was heated to 145°C, and kept there 60 minutes. Reactions consistency inside thereactor was around 10%. After reaction time, the active material was cooled downusing heat exchanger system. Results was microcrystalline cellulose product havingDP value 250. Average particle size (d50-value) was 61 μm, d10-value 20 μm, andd90-value 196 μm. So called d-ratio was 2.89. Particle size distribution of pilot scaleMCC hydrolysis is shown in Figure 3.

Claims

CLAIMS:

1. A reactor system for producing microcrystalline cellulose (MCC) comprising:- a force circulation reactor (2) configured to hydrolyze a feed material (1a, 1b)comprising a biomaterial (1a) and an active material (1b) to produce MCC,and -a fractionation unit (4) configured to separate dissolved carbohydrates fromthe active material and produce a carbohydrate stream (7), and- a process device (6) configured to circulate the active material (1b) back tothe force circulation reactor (2) from the fractionation unit (4) for producingMCC.

2. The reactor system of any one of the preceding claims, wherein the processdevice (6) is a pump.

3. The reactor system of any one of the preceding claims, wherein the reactorsystem further comprises a first process line (3) configured to lead the activematerial and dissolved carbohydrates from the force circulation reactor (2) to the fractionation unit (4).

4. The reactor system of any one of the preceding claims, wherein the reactorsystem further comprises a second process line (5) configured to lead theactive material from the fractionation unit (4) to the process device (6).

5. The reactor system of any one of the preceding claims, wherein the reactorsystem further comprises a third process line (8) configured to recover theMCC (11).

6. The reactor system of any one of the preceding claims, wherein the reactorsystem further comprises a fourth process line (9) configured to lead theactive material from the process device (6) to the force circulation reactor (2).

7. The reactor system of any one of the preceding claims, wherein the reactorsystem further comprises an active material storage (13).

8. The reactor system of any one of the preceding claims, wherein the reactorsystem further comprises a fifth process line (12) configured to lead theactive material from the fourth process line (9) to an active material storage(13) or lead the active material out from the system.

9. The reactor system of any one of the preceding claims, wherein the reactorsystem further comprises a sixth process line (14) configured to lead theactive material from the active material storage (13) to the force circulationreactor (2).10.The reactor system of any one of the preceding claims, wherein the system comprises further process stages (10).11.The reactor system of any one of the preceding claims, wherein the third process line (8) is configured to lead the MCC further process stages (10) and a seventh process line (15) is configured to lead the active material fromthe further process stages (10) to the active material storage (13), to thefourth process line (9) or to the fifth process line (12). 12.The reactor system of any one of the preceding claims, wherein the fractionation unit (4) is microfiltration unit, nanofiltration unit, ultrafiltrationunit, reverse osmosis system, or membrane filtration unit.13.The reactor system of any one of the preceding claims, wherein the further process stages (10) include washing, bleaching, drying, and / or dry grinding.14.A process for producing microcrystalline cellulose using the reactor system of any one of claims 1 - 13.

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