Method for recovering saccharide from saccharified slurry, and washing device for washing residue
09850550 · 2017-12-26
Assignee
Inventors
- Shoji Tsujita (Itami, JP)
- Noriaki Izumi (Kobe, JP)
- Hironori Tajiri (Kobe, JP)
- Hiromasa Kusuda (Kobe, JP)
- Masaki Tsuzawa (Kobe, JP)
Cpc classification
International classification
Abstract
A saccharide recovering method for recovering saccharides from a saccharified slurry obtained after subjecting a slurry of cellulosic biomass to a hot water treatment and to provide a washing device for washing a saccharified slurry residue suited for conducting such a saccharide recovery method is provided. Saccharified slurry of cellulosic biomass is fed on a conveyor having a net conveyor belt, the saccharified slurry is dehydrated, washing water is sprayed to dissolve saccharides remaining in the residue into the washing liquid. The residue is washed by a plurality of washing water spraying units disposed in series in such a manner that the moving direction of the residue and the moving direction of the washing water are opposite to each other. The washing water having washed the residue is used as washing water for washing water spraying unit in the direction opposite to the moving direction of the conveyor.
Claims
1. A method for recovering saccharide from a saccharified slurry, comprising: a washing step of feeding a saccharified slurry containing C5 saccharides or C6 saccharides obtained by subjecting a slurry of cellulosic biomass to a hot water treatment in a supercritical state or subcritical state, on a conveyor having a net conveyor belt, dehydrating the saccharified slurry and spraying washing water to a dehydrated residue on the conveyor to dissolve C5 saccharides or C6 saccharides remaining in the residue in a washing liquid, wherein the washing step washes a residue by spraying washing water to the residue from a plurality of washing water spraying units disposed in series in such a manner that the moving direction of the residue and the moving direction of the washing water are opposite to each other, and the washing water having washed the residue is used as washing water of a washing water spraying unit neighboring in the direction opposite to the moving direction of the conveyor.
2. The method for recovering saccharides from a saccharified slurry according to claim 1, further comprising an adding step of adding a flocculant to the saccharified slurry before the washing step.
3. The method for recovering saccharides from a saccharified slurry according to claim 2, wherein the net conveyor belt has a mesh ranging from 0.5 mm or more and 2.0 mm or less.
4. The method for recovering saccharides from a saccharified slurry according to claim 2, wherein the number of the washing water spraying units is five or more and twenty or less.
5. The method for recovering saccharides from a saccharified slurry according to claim 1, wherein the net conveyor belt has a mesh ranging from 0.5 mm or more and 2.0 mm or less.
6. The method for recovering saccharides from a saccharified slurry according to claim 5, wherein the number of the washing water spraying units is five or more and twenty or less.
7. The method for recovering saccharides from a saccharified slurry according to claim 1, wherein the number of the washing water spraying units is five or more and twenty or less.
8. The method for recovering saccharides from a saccharified slurry according to claim 2, wherein in the adding step, one or combination of two or more of a cationic flocculant, an anionic flocculant, a nonionic flocculant and an amphoteric flocculant is added at 0.1% by mass or more and 2% by mass or less with respect to a solid content of the saccharified slurry.
9. A washing device that washes a solid residue in a saccharified slurry containing C5 saccharides or C6 saccharides obtained by subjecting a slurry of cellulosic biomass to a hot water treatment in a supercritical state or subcritical state, the washing device comprising: a conveyor having a net conveyor belt; a plurality of spraying units disposed in series on the net conveyor belt; and a plurality of water storage tanks disposed below the net conveyor so that they are situated below the respective spraying units; the washing device feeding a saccharified slurry on the net conveyor belt, dehydrating the saccharified slurry, and then spraying washing water to the residue on the net conveyor belt from the spraying unit, thereby washing the residue, wherein one of the water storage tanks is connected with one spraying unit neighboring in the direction opposite to a moving direction of the conveyor by piping, and the water storage tank stores water sprayed from the spraying unit disposed directly above, and the stored water is repeatedly used sequentially in the spraying unit neighboring in the direction opposite to the moving direction of the conveyor via a pump and piping to continuously wash the residue.
10. The washing device according to claim 9, wherein the number of the spraying units is five or more and twenty or less.
11. A washing device that washes a solid residue in a saccharified slurry containing C5 saccharides or C6 saccharides obtained by subjecting a slurry of cellulosic biomass to a hot water treatment in a supercritical state or subcritical state, the washing device comprising: a conveyor having a net conveyor belt; a plurality of water storage tanks; and a washing water spraying unit, the washing device feeding a saccharified slurry on the net conveyor belt, dehydrating the saccharified slurry, and then spraying washing water to the residue on the net conveyor belt, thereby washing the residue, wherein the plurality of water storage tanks are sequentially stacked at different heights in such a manner that part of the water storage tank neighboring in the direction opposite to a moving direction of the conveyor is lower, the net conveyor belt turns around so as to pass through the top face of every water storage tank from the water storage tank situated at the lowest position to the water storage tank situated at the highest position, and the plurality of water storage tanks stores washing water sprayed on the net conveyor belt from the washing water spraying unit disposed above the water storage tank situated at the highest position, and repeatedly sprays the stored washing water sequentially on the net conveyor belt above the water storage tank neighboring in the direction opposite to the moving direction of the conveyor, thereby continuously washing the residue.
12. The washing device according to claim 11, wherein the number of the plurality of water storage tanks is five or more and twenty or less.
Description
BRIEF DESCRIPTION OF DRAWINGS
(1)
(2)
(3)
(4)
(5)
DESCRIPTION OF EMBODIMENTS
(6) Hereinafter, preferred embodiments of the present invention will be explained in reference to the drawings. The present invention is not limited to the following description.
Embodiment 1
(7)
(8) (Preparation of Source Material Slurry)
(9) First of all, cellulosic biomass (vegetation biomass such as bagasse, beet dregs, or straw) is ground to several millimeters or smaller as a pretreatment. The ground cellulosic biomass is mixed with water and stirred to produce a slurry. The water content of the prepared source material slurry is preferably adjusted to 50% by mass or higher and 95% by mass or lower. To the source material slurry, acid such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid or acetic acid may be appropriately added as an acid catalyst. In this case, the acid concentration in the source material slurry is preferably adjusted to 0.1% by mass or higher and 10% by mass or lower.
(10) (Saccharification and Decomposition of Cellulose and/or Hemicellulose)
(11) The source material shiny is fed into a pressure vessel 1 after it is preheated as is necessary. A non-limiting concrete example of the pressure vessel 1 is an indirect heating pressure vessel. In the case of saccharifying and decomposing hemicellulose, the source material slurry is subjected to a hot water treatment at a temperature ranging from 140° C. or higher and 200° C. or lower, and under a pressure ranging from 1 MPa or higher and 5 MPa or lower in the pressure vessel 1. By this hot water treatment, hemicellulose in the cellulosic biomass is saccharified and decomposed (hydrolyzed) into C5 saccharides. In the case of saccharifying and decomposing cellulose, the source material slurry is subjected to a hot water treatment at a temperature ranging from 240° C. or higher and 300° C. or lower, and under a pressure ranging from 4 MPa or higher and 10 MPa or lower in the pressure vessel 1. By this hot water treatment, cellulose in the cellulosic biomass is hydrolyzed into C6 saccharides.
(12) Preferably, after conduction of a hot water treatment for a certain time, the slurry (saccharified slurry) is fed to a flush tank 2 from the pressure vessel 1, and the saccarified slurry is rapidly cooled to a temperature less than the subcritical state through flush evaporation to thereby stop the saccharification reaction.
(13) (Adding Step)
(14) The saccharified slurry taken out from the flush tank 2 is fed to a mixing tank 3. To the mixing tank 3, a solution containing one or combination of two or more of a cationic flocculant, an anionic flocculant, a nonionic flocculant and an amphoteric flocculant is fed from a flocculant tank 4, and mixed with the saccharified slurry. Preferably, one or combination of two or more of a cationic flocculant, an anionic flocculant, a nonionic flocculant and an amphoteric flocculant is added to the saccharified slurry so that its concentration with respect to the solid content in the saccharified slurry is 0.1% by mass or higher and 2% by mass or lower. The kind of the flocculant is not particularly limited. By adding the flocculant, solids in the saccharified slurry form a floc.
(15) (Washing Step)
(16) The saccharified slurry to which the flocculant is added is fed to a residue washing device 5, and fed onto a net conveyor belt of a conveyor having the net conveyor belt. The saccharified slurry to which the flocculant is added has a water content of about 90% by mass, and is rapidly dehydrated to have a water content of about 80 to 90% by mass by downward dropping of water from the net conveyor belt. Since the dehydration is conducted merely by means of the net conveyor belt, a vacuum pump or a blower for pressurization is not required, and the cost of equipment is low in contrast with a dehydrating method using a belt filter.
(17)
(18) As the saccharified slurry to which the flocculant is added, which is taken out from the mixing tank 3 is dropped on a net conveyor belt 12, water 13 drops downward through the net conveyor belt 12. As a result, the saccharified slurry is dehydrated, and a residue 20 remains on the net conveyor belt 12. The water is stored in the directly underlying water storage tank 15e.
(19) In the conveyor 11, since rotation axes 21a and 21b of the net conveyor belt 12 rotate counterclockwise, the net conveyor belt 12 turns around in such a manner that its upper face moves from right to left. Therefore, the residue 20 moves from right to left in the diagram.
(20) Next, a method of washing the residue 20 in a steady state of the residue washing device 5 illustrated in
(21) The washing water stored in the water storage tank 15a is stirred by the stirrer, 16a, and then fed to the washing water spraying unit 14b via a pump P1 and the path 17a as illustrated in
(22) Also regarding residues 20c to 20e, similarly to the residue 20b, washing water is sprayed from the washing water spraying units 14c to 14e in such a manner that the moving direction of the residue and the moving direction of the washing water are opposite to each other. The washing water sprayed to the residue 20e from the washing water spraying unit 14e dissolves the saccharides remaining in the residue 20e to become a washing liquid 22e containing saccharides, and is stored in the water storage tank 15e. Then it is stirred with the water 13 having dropped first, and is fed to the concentrating device 6 via a pump P5 and the piping 19.
(23) As described above, in the present invention, the residue 20a to 20e are washed with washing water sprayed from the washing water spraying units 14a to 14e in such a manner that the moving direction of the residue and the moving direction of the washing water are opposite to each other. That is, the moving direction of the residue 20 is 20e.fwdarw.20d.fwdarw.20c.fwdarw.20b.fwdarw.20a, and the moving direction of the washing water is 14a.fwdarw.14b.fwdarw.14c.fwdarw.14d.fwdarw.14e. The washing water having washed the residue 20 is used as washing water of the washing water spraying unit neighboring on the side opposite to the conveyor moving direction (the washing water spraying unit neighboring on the right in
(24) Further, since washing water in which saccharides are dissolved is reused, the amount of washing water fed to the concentrating device 6 is reduced in comparison with the conventional method of washing a dehydrated cake with washing water, and the load of the concentration step can be reduced. Further, since the residue washing operation is conducted in the conveyor 11, the washing operation can be conducted continuously. Accordingly, it is also possible to reduce the time required for the washing step in comparison with a conventional saccharide recovering method in which washing and dehydration of a dehydrated cake are repeated.
(25) The residue 20 fed to the dehydrator 9 is separated into a dehydrated cake and a filtrate (washing liquid). Non-limiting concrete examples of the dehydrator 9 include a drum filter, a belt filter, a disc filter, a filter press and a decanter. The dehydrated cake may be rendered a slurry again and fed to another saccharifying and decomposing step, or may be disposed of, if unnecessary. On the other hand, the filtrate may be used as part of the washing water fed to the residue washing device 5 as illustrated in
(26) (Concentration Step)
(27) The washing water (including the water 13 separated first from the saccharified slurry) fed to the concentrating device 6 is concentrated so that the concentration of saccharides is 10% by mass or higher that is suited for alcoholic fermentation by yeast. Non-limiting concrete examples of the concentrating device 6 include a reverse osmosis membrane device and a distillation device.
(28) Preferably, the washing water is stored in a thickener to remove a sediment before it is fed to the concentrating device 6. By removing the sediment, soiling of the concentrating device 6 can be prevented. To the thickener, it is preferred to add either one or a combination of two or more of a cationic flocculant, an anionic flocculant, a nonionic flocculant and an amphoteric flocculant so that its concentration relative to the solid content in the thickener is 0.1% by mass or higher and 2% by mass or less. The sediment recovered from the thickener may be fed to the mixing tank 3 and thus the flocculant added to the mixing tank 3 may be reduced.
(29) (Fermentation Step)
(30) The washing water (saccharified solution) concentrated by the concentrating device 6 is fed to a fermentation tank 7. In the fermentation tank 7, saccharides (C5 saccharides and C6 saccharides) are converted to ethanol by the use of yeast. In the fermentation step, a known alcohol fermentation method can be employed.
(31) (Distillation Step)
(32) Next, the alcoholic fermented solution after the fermentation step is fed to a distillation device 8, and ethanol is concentrated. In the distillate obtained in the distillation step, ingredients other than the solid and ethanol have been removed. In the distillation step, a known distillation step that is known as a production method of distilled liquor can be employed.
Embodiment 2
(33)
(34) Next, a washing method of the residue 37 in a steady state of the residue washing device 31 illustrated in
(35) In a bottom part of the water storage trough 34e, the sprinkling port 35c is disposed, and the stored washing liquid is sprayed to a residue 37d on the net conveyor belt 36 at a lower stage. The residue 37d is washed with the washing water sprayed from the sprinkling ports 35e, and the remaining saccharides are dissolved in the washing liquid. The washing water containing saccharides passes through the net conveyor belt 36, and is stored in the water storage tough 34d.
(36) Also regarding the residues 37c to 37a, washing water is sprayed from the sprinkling ports 35d to 35b, respectively as is the case with the residue 37d. The washing water sprayed to the residue 37a is stored in the water storage trough 34a, and then stored in the water storage tank 33 via piping 38 connected with the sprinkling port 35a. Then, the washing water in the water storage tank (including water separated from the residue 37 of the saccharified slurry) is fed to the concentrating device 6.
(37) In the residue washing device 31 illustrated in
(38) <Simulation of Saccharide Recovery>
(39) Assuming that the flow rate and the solid concentration of a source material slurry are 100 t/h and 10% by mass, respectively and the saccharide concentration of a saccharified slurry is 10% by mass (concentration in the liquid), the saccharide flow rate is calculated as 9 t/h.
(40) (Conventional Art)
(41) Saccharide recovery in the case of dehydrating a saccharified slimy by a dehydrator and recovering the filtrate under the above assumption was simulated. Assuming that the solid concentration of the dehydrated cake is 30% by mass, the flow rate of the dehydrated cake is 33.31/h, and the saccharide flow rate of the saccharide liquid remaining in the dehydrated cake is 2.33 t/h. The saccharide flow rate of the filtrate is 6.67 t/h, and the saccharide recovery is calculated as 6.67/9×100=74.1%.
(42) Next, saccharide recovery in the case of adding washing water to the dehydrated cake at a flow rate of 23 t/h to give a shiny again, and dehydrating the slurry again by a dehydrator and recovering the filtrate was simulated. Since the filtrate of the second dehydrator contains saccharides at a flow rate of 1.03 t/h, we assumed that the filtrate returned to the saccharified slurry before being put into the dehydrator and mixed them. The mixture that is rendered a slurry again has a flow rate of 56 t/h, a solid concentration of 18% by mass, a saccharide concentration of 4.47% by mass, and a saccharide flow rate of 2.07 t/h. The flow rate of the second dehydrated cake is 33 t/h, and the saccharide flow rate of the saccharide liquid remaining in the dehydrated cake is 1.04 t/h. The saccharide flow rate of the second filtrate is 1.03 t/h. Saccharide recovery integrated from the first filtrate is calculated as (9−1.04)/9×100=88.4%
(43) Next, using five dehydrators, the dehydrated cake was washed four times in the same manner as described above, and the saccharide recovery integrated from the first filtrate was calculated as 94.9%. However, the dehydrator is determined as not being practical because it is expensive, and raises the cost of equipment although it achieves high saccharide recovery.
(44) (Present Invention)
(45) Next, regarding the saccharide recovering method of Embodiment 1, the saccharide recovery from the washing water was simulated under the same assumption as described above. Twelve washing water spraying units were disposed in series, and the filtrate flow rate was assumed as 73 t/h every time. The solid concentration of the residue on the net conveyor belt was assumed as 12% by mass. The saccharide concentration and the saccharide flow rate of the residue washed twelve times were calculated as 2.67% by mass and 1.96 t/h, respectively. The saccharide flow rate of the twelfth washing water (filtrate) was calculated as 1.95 t/h. Assuming that the residue after twelve washings is mixed with washing water (not containing saccharides) at a flow rate of 23 t/h, and filtrated by a dehydrator, the filtrate of the dehydrator is calculated to have a flow rate of 73 t/h, a saccharide concentration of 2.04% by mass, and a saccharide flow rate of 1.49 t/h. The flow rate of the dehydrated cake is 33 t/h, and the saccharide flow rate of the saccharide liquid remaining in the dehydrated cake is 0.47 t/h. The filtrate of the dehydrator is assumed to be used as the residue washing water of the twelfth time. The saccharide recovery from the filtrate (washing water) by the residue washing device under this assumption was calculated as (9−0.47)/9×100=94.7%.
(46) As described above, the saccharide recovering method of Embodiment 1 showed high saccharide recovery comparable with that by the conventional saccharide recovering method that recovers saccharides from a dehydrated cake by using five dehydrators. The cost of one residue washing device having twelve washing water spraying units is comparable with the cost of one dehydrator. This leads to the consideration that according to the present invention it is possible to recover saccharides efficiently with lower costs compared to the conventional saccharide recovering method according to the present invention.
(47) Table 1A and Table 1B show the relationship between the number of times of washing of the residue and the saccharide concentration of the filtrate (washing water that is sprayed to the residue and recovered) in the aforementioned simulation regarding the saccharide recovering method of Embodiment 1. As shown in Table 1A and Table 1B, the saccharide concentration of the filtrate of the first time washing was 9.68% by mass in the case of the residue washing device that executes washing twenty times (namely, the residue washing device having twenty washing water spraying units). The saccharide concentration of the filtrate of the second time washing decreased to 9.28% by mass, and the saccharide concentration of the filtrate decreased as the number of times of washing increased. And the saccharide concentration in the liquid contained in the dehydrated cake decreased to 1.38% by mass.
(48) Among the residue washing devices that were performed at the numbers of times of washing of 2, 5, 10, 12, 15 and 20, the saccharide concentrations contained in the liquid amount differ from each other, as evidenced by 5.32% by mass, 3.57% by mass, 232% by mass, 2.04% by mass, 1.73% by mass and 1.38% by mass, although the liquid amounts contained in the respective dehydrated cakes are identical. This proved that the remaining saccharide in the dehydrated cake reduces as the number of times of washing of the residue washing device increases. Accordingly, as shown in Table 2A and Table 2B that will be later described, the saccharide recovery increases as the number of times of washing of the residue washing device increases.
(49) It was revealed that when the number of times of washing (namely, the number of washing water spraying units) is five or more, the saccharide concentration of the filtrate of the first washing exceeds 9% by mass, and when the number of times of washing is ten or more, it is as high as about 9.4% by mass or more, and the load of the concentrating device of the subsequent stage can be reduced.
(50) TABLE-US-00001 TABLE 1A Saccharide concentration in filtrate at each number of times of washing (% by mass) First Second Third Fourth Fifth Sixth Seventh Eighth Ninth Tenth Eleventh Twelfth time time time time time time time time time time time time Second time 8.65 6.99 — — — — — — — — — — washing Fifth time 9.11 8.01 6.91 5.80 4.69 — — — — — — — washing Tenth time 9.43 8.74 8.04 7.33 6.63 5.92 5.20 4.49 3.77 3.04 — — washing Twelfth time 9.51 8.90 8.29 7.68 7.06 6.44 5.82 5.20 4.57 3.94 3.31 2.67 washing Fifteenth time 9.59 9.08 8.57 8.06 7.54 7.03 6.51 5.99 5.46 4.94 4.41 3.87 washing Twentieth time 9.68 9.28 8.88 8.48 8.08 7.67 7.27 6.86 6.45 6.04 5.62 5.21 washing
(51) TABLE-US-00002 TABLE 1B Saccharide concentration in Saccharide concentration in filtrate at each number of times of washing (% by mass) liquid content remaining in Thirteenth Fourteenth Fifteenth Sixteenth Seventeenth Eighteenth Nineteenth Twentieth dehydrated cake time time time time time time time time (% by mass) Second time — — — — — — — — 5.32 washing Fifth time — — — — — — — 3.57 washing Tenth time — — — — — — — 2.32 washing Twelfth time — — — — — — — 2.04 washing Fifteenth time 3.34 2.80 2.27 — — — — 1.73 washing Twentieth time 4.79 4.37 3.95 3.53 3.10 2.67 2.24 1.81 1.38 washing
(52) Table 2A and Table 2B show the relationship between the number of times of washing of the residue and the saccharide flow rate of the filtrate in the above simulation regarding die saccharide recovering method of Embodiment 1.
(53) TABLE-US-00003 TABLE 2A Saccharide flow rate of filtrate at each number of times of washing (t/h) First Second Third Fourth Fifth Sixth Seventh Eighth Ninth Tenth Eleventh Twelfth time time time time time time time time time time time time Second time 7.76 5.10 — — — — — — — — — — washing Fifth time 8.17 5.85 5.04 4.23 3.42 — — — — — — — washing Tenth time 8.46 6.38 5.87 5.35 4.84 4.32 3.80 3.27 2.75 2.22 — washing Twelfth time 8.53 6.50 6.05 5.60 5.16 4.70 4.25 3.79 3.34 2.88 2.42 1.95 washing Fifteenth time 8.60 6.63 6.26 5.88 5.51 5.13 4.75 4.37 3.99 3.60 3.22 2.83 washing Twentieth time 8.68 6.77 6.48 6.19 5.90 5.60 5.31 5.01 4.71 4.41 4.11 3.80 washing
(54) TABLE-US-00004 TABLE 2B Saccharide flow rate in liquid content Saccharide flow rate of filtrate at each number of times of washing (t/h) remaining in Saccharide Thirteenth Fourteenth Fifteenth Sixteenth Seventeeth Eighteenth Nineteenth Twentieth dehydrated cake recovery time time time time time time time time (t/h) (%) Second time — — — — — — — — 3.88 86.2 washing Fifth time — — — — — — — — 2.60 90.8 washing Tenth time — — — — — — — — 1.69 94.0 washing Twelfth time — — — — — — — — 1.49 94.7 washing Fifteenth time 2.44 2.05 1.65 — — — — — 1.26 95.5 washing Twentieth time 3.50 3.19 2.88 2.57 2.26 1.95 1.64 1.32 1.01 96.4 washing
INDUSTRIAL APPLICABILITY
(55) The method for recovering saccharified from a saccharified slurry and the washing device of the present invention are useful in bioenergy fields as a production method and a washing device for decomposing cellulosic biomass and producing a saccharified solution.
REFERENCE SIGNS LIST
(56) 1 pressure vessel 2 flush tank 3 mixing tank 4 flocculant tank 5 residue washing device (Embodiment 1) 6 concentrating device 7 fermentation tank 8 distillation device 9 dehydrator 11 conveyor 12 net conveyor belt 13 water 14a to 14e washing water spraying unit 15a to 15e water storage tank 16a to 16e stirrer 17a to 17d piping 18 washing water tank 19 piping 20 residue 21a, 21b rotation axis 22a to 22e washing water 31 residue washing device (Embodiment 2) 32 conveyor 33 water storage tank 34a to 34e water storage trough (water storage tank) 35a to 35e sprinkling pod 36 net conveyor belt 37, 37a to 37e residue 38 piping