JP5981259B2 - Storage method of residual distillation slurry - Google Patents

Description

  The present invention relates to a method for preserving a distillation residue slurry.

  Conventionally, a method for producing bioethanol using a biomass such as lignocellulosic biomass as a substrate is known. According to the method for producing bioethanol, after obtaining a saccharification solution by saccharifying the biomass with a saccharifying enzyme, the saccharification solution is further fermented with a fermenting bacterium to obtain a fermentation solution containing ethanol. Can do.

  Since the ethanol contained in the fermentation solution obtained by the above production method is dilute, bioethanol can be obtained by distilling and concentrating the fermentation solution. At this time, since the waste liquid left after distillation of the fermentation solution contains an organic substance that becomes a fertilizing component, use as a soil conditioner has been studied.

  As the soil improving material, for example, a waste liquid having an alcohol content of 0.5% by mass or less by distilling the fermentation solution is known (see Patent Document 1). When applied to soil, the soil conditioner can improve the soil fertility and the like with the organic matter.

  In addition, in the bioethanol production method, a technique called simultaneous saccharification and fermentation (hereinafter referred to as SSF (Simultaneous Saccharification and Fermentation)) in which saccharification with the saccharifying enzyme and fermentation with the fermenting bacterium are performed in the same tank is known. According to the SSF, a fermentation solution containing ethanol can be obtained as in the production method, and bioethanol can be obtained by distilling and concentrating the fermentation solution (for example, Patent Document 2). reference).

  Since the fermentation solution obtained by the SSF contains solids such as biomass residues, saccharifying enzymes, and the like, soot-like waste liquid (hereinafter referred to as distillation residue slurry) remains after the distillation. Since the distillation residue slurry also contains an organic substance that becomes a fertilizer, it has been studied for use as a soil conditioner.

JP 2012-17462 A JP 2010-246422 A

  However, since the distillation residue slurry contains easily decomposable organic matter, if the distillation residue slurry is stored for a long period of time, the easily decomposable organic matter is spoiled by the growth of microorganisms, and the fertilizer component is reduced. There is an inconvenience of doing.

  An object of the present invention is to provide a method capable of eliminating such inconvenience and storing the distillation residue slurry without decaying over a long period of time.

In order to achieve this object, the method for preserving a distillation residue slurry of the present invention includes a step of saccharifying a substrate made of rice straw with a saccharifying enzyme in the same tank and fermenting with a fermenting bacterium to obtain a fermentation solution And distilling the fermentation solution to obtain ethanol, a method of recovering and storing the distillation residue slurry remaining after distillation of the fermentation solution when producing bioethanol. Adding cyanamide so that the concentration of nitrogen derived from the calcium cyanamide is in the range of 0.08 to 0.8 mass%, the distillation residue slurry has a C / N ratio in the range of 2 to 20, Having a biochemical oxygen demand in the range of 30 to 150 mg / g, and the fermentation treatment has a conversion rate of sugar to ethanol generated by saccharification treatment of the substrate of 60 to 0% and so as to perform it, characterized by.

  In the method for storing a distillation residue slurry of the present invention, calcium cyanamide is added to the distillation residue slurry so that the nitrogen concentration derived from the calcium cyanamide is in the range of 0.08 to 0.8 mass%. Since the calcium cyanamide is toxic to microorganisms in the distillation residue slurry, it is possible to obtain an action of suppressing the growth of the microorganisms by making the nitrogen concentration derived from the calcium cyanamide within the above range. it can. Therefore, according to the method for storing a distillation residue slurry of the present invention, the distillation residue slurry can be stored for a long time without being spoiled.

  When adding the calcium cyanamide to the distillation residue slurry, if the nitrogen concentration derived from the calcium cyanamide is less than 0.08% by mass, an action of suppressing the growth of microorganisms in the distillation residue slurry can be obtained. Therefore, it is impossible to prevent the distillation residue slurry from decaying. Moreover, when the nitrogen concentration derived from the calcium cyanamide exceeds 0.8% by mass, not only the effect of suppressing the growth of microorganisms in the distillation residue slurry can be obtained, but also the distillation residue slurry. When it is used as a soil conditioner, it becomes excessive in nitrogen. Examples of the damage caused by excessive nitrogen include that the plant is likely to suffer from diseases and the quality is lowered, and that in the case of rice, the plant tends to fall down.

Further, in the method for storing a distillation residue slurry of the present invention, the distillation residue slurry has a C / N ratio in the range of 2 to 20 and a biochemical oxygen demand in the range of 30 to 150 mg / g. When the distillation residue slurry has a C / N ratio of less than 2 and a biochemical oxygen demand of less than 30 mg / g, it may not be able to sufficiently improve the soil even when applied to the soil. Further, if the C / N ratio exceeds 20 and the biochemical oxygen demand exceeds 150 mg / g, the distillation residue slurry may rot or generate methane gas even if the calcium cyanamide is added. There is.

In the method for preserving a distillation residue slurry of the present invention, the fermentation treatment is performed such that the conversion rate of sugar to ethanol generated by the saccharification treatment of the substrate is 60 to 70%. In the method for storing a distillation residue slurry according to the present invention, the conversion rate of the sugar to ethanol in the fermentation treatment is set to 60 to 70%, whereby the C / N ratio and biochemical oxygen of the distillation residue slurry are set. The required amount can be within the above range.

When the conversion rate of the sugar to ethanol in the fermentation treatment is less than 60%, the content of easily decomposable organic substances in the distillation residue slurry increases, and when the distillation residue slurry is stored for a long period of time, There is a risk that fertilizing components may be reduced by decay. Examples of the easily decomposable organic substance include sugars that have not been used for fermentation, organic acids as by-products, and the like.

Moreover, it is preferable that the preservation | save method of the distillation residue slurry of this invention adds lime nitrogen to the said distillation residue slurry so that it may become a density | concentration of the range of 0.4-4 mass / volume%. Since the lime nitrogen contains the calcium cyanamide, the concentration of nitrogen derived from the calcium cyanamide in the distillation residue slurry is set to 0.08 by adding the lime nitrogen to the distillation residue slurry so that the concentration is in the above range. It can be made into the range of -0.8 mass%.

The flowchart which shows the manufacturing process of the bioethanol for obtaining the distillation residue slurry used for this invention.

  Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

  The distillation residue slurry of this embodiment is obtained by distilling a fermentation solution obtained by subjecting a substrate made of lignocellulosic biomass to saccharification with a saccharifying enzyme in the same tank, and fermenting with a fermenting bacterium, to obtain bioethanol. It is a waste liquid left after it is obtained. Then, next, the manufacturing method of the bioethanol which uses lignocellulosic biomass as a substrate is demonstrated.

  In the method for producing bioethanol, for example, rice straw is used as the lignocellulosic biomass. First, the rice straw and aqueous ammonia are mixed and stirred to obtain a substrate mixture. Next, the substrate mixture is stored for a predetermined time in a storage tank. As a result, an ammonia-containing saccharification pretreatment product in which lignin is dissociated from the substrate rice straw or the rice straw is swollen is obtained.

  In the present application, “dissociation” means that at least a part of the binding sites of lignin bound to cellulose or hemicellulose in rice straw is cut. In addition, “swelling” means that voids are generated in cellulose or hemicellulose constituting crystalline cellulose due to the ingress of liquid, or voids are generated inside cellulose fibers to expand.

  The ammonia-containing pre-saccharification product has a pH in the range of 13 to 14 as a result of the treatment with the ammonia water. Therefore, after ammonia is diffused from the ammonia-containing saccharification pretreated product to separate ammonia, an ammonia separated saccharification pretreated product is obtained, and then the pH of the ammonia separated saccharification pretreated product is adjusted. The pH of the ammonia separation saccharification pretreatment product is adjusted by adding at least one of phosphoric acid, phosphate, nitric acid or sulfuric acid, and adjusting the pH of the ammonia separation saccharification pretreatment product to a range of 3 to 7, preferably pH 4. To 4.5. The pH range is a range in which a saccharifying enzyme described later can act.

  Next, simultaneous saccharification and fermentation (SSF) is performed by adding a saccharification enzyme and fermenting bacteria such as yeast to the ammonia separation saccharification pretreatment product. In the SSF, a saccharifying enzyme and a fermenting bacterium may be added at the same time, or after first adding a saccharifying enzyme and saccharifying the ammonia separation saccharification pretreatment product for a predetermined time, a fermenting bacterium may be added. . As a result, the cellulose or hemicellulose contained in the ammonia separation saccharification pretreatment product is saccharified by the saccharifying enzyme to produce sugar, and the sugar is fermented by the fermenting bacterium to obtain a fermentation solution containing ethanol. .

  In the fermentation solution, by appropriately selecting the type of the fermenting bacterium, the conversion rate of sugar produced by saccharification of cellulose or hemicellulose contained in the ammonia-separated saccharification pretreatment product to ethanol is 60% or more. Fermented to.

  Next, by distilling the fermentation solution, the ethanol is separated and concentrated to obtain bioethanol, and a distillation residue slurry remaining as a waste liquid after the distillation is recovered. Since the SSF does not perform solid-liquid separation, the obtained fermentation solution contains solids such as biomass residues, saccharifying enzymes, and the like, and the distillation residue slurry is in a bowl shape. Moreover, the said distillation residue slurry is obtained as a waste liquid after distilling the said fermentation solution fermented so that the conversion rate of the said sugar to ethanol may be 60% or more, C / C in the range of 2-20 N ratio and biochemical oxygen demand in the range of 30-150 mg / g.

  In this embodiment, lime nitrogen is added to the distillation residue slurry so as to have a concentration in the range of 0.4 to 4% by mass / volume. The lime nitrogen contains calcium cyanamide, and decomposes in the distillation residue slurry to produce decomposition products such as cyanamide. Therefore, by adding the lime nitrogen to the distillation residue slurry so as to have a concentration in the above range, the calcium cyanamide-derived nitrogen concentration in the distillation residue slurry is in the range of 0.08 to 0.8 mass%. Become. As a result, the distillation residue slurry can be stored for a long period of time in a state suitable for a soil improvement material.

  The lime nitrogen may be granular or powdery. When the lime nitrogen is granular, decomposition of the lime nitrogen in the distillation residue slurry proceeds slowly, so that the concentration in the distillation residue slurry is in the range of 0.6 to 4 mass / volume%. By adding, the residual distillation slurry can be stored for a longer period of time. Further, when the lime nitrogen is in a powder form, decomposition of the lime nitrogen in the distillation residue slurry is facilitated, and therefore a small concentration of 0.4 to 4 mass / volume% by the distillation residue slurry. By adding so as to be, it is possible to prevent the distillation residue slurry from decaying.

  Moreover, since the said lime nitrogen contains a fertilizer component itself, the fertilizer component in this distillation residue slurry can be increased by adding to the said distillation residue slurry so that it may become the density | concentration of the said range. Therefore, the distillation residue slurry can promote the growth of plants in the applied soil.

  Next, examples and comparative examples of the present invention are shown.

  First, the residual distillation slurry obtained by the ethanol production method using the SSF was prepared using rice straw as lignocellulosic biomass as a substrate. The distillation residue slurry is obtained by distilling a fermented solution fermented so that the conversion rate of sugar produced by saccharification of cellulose or hemicellulose contained in the ammonia separation saccharification pretreatment product into ethanol is in the range of 60 to 70%. It is a waste liquid left after.

  The distillation residue slurry had a C / N ratio in the range of 10-15 and a biochemical oxygen demand in the range of 90-150 mg / g. Moreover, the said distillation residue slurry contained 1.0 mass% of nitrogen, 0.3 mass% of phosphoric acid, and 0.4 mass% of potassium as a fertilizer.

  Next, the distillation residue slurry was sterilized by treating at a temperature of 121 ° C. for 20 minutes.

  Next, the amount of addition was varied and granular lime nitrogen was added to the sterilized residual slurry after sterilization to prepare a plurality of sample solutions. Each of the sample solutions had a lime nitrogen concentration of 3.75 mass / volume% (Example 1), 1.25 mass / volume% (Example 2), and 0.63 mass / volume% (Example 3). 0.31 mass / volume% (Comparative Example 1), 0.16 mass / volume% (Comparative Example 2), 0.08 mass / volume% (Comparative Example 3), 0 mass / volume% (Comparative Example 4) It was made to become.

  As a result, each sample solution has a nitrogen concentration derived from calcium cyanamide contained in lime nitrogen of 0.750 mass% (Example 1), 0.250 mass% (Example 2), 0.125 mass% ( Example 3), 0.063 mass% (Comparative Example 1), 0.031 mass% (Comparative Example 2), 0.016 mass% (Comparative Example 3), and 0 mass / volume% (Comparative Example 4). Has been.

  Next, each said sample solution was left to stand in the thermostat set to 30 degreeC. Then, after 3 days, the growth of white mold was observed as an index of decay in each sample solution. The white mold indicates that the more the amount is, the more the decay is progressing. The results are shown in Table 1.

  From Table 1, lime nitrogen was added to the distillation residue slurry after sterilization so as to be 0.63 to 3.75 mass / volume%, and the concentration of nitrogen derived from calcium cyanamide contained in the lime nitrogen was 0.125. In the sample solutions of Examples 1 to 3 which are adjusted to 0.750% by mass, no white mold growth is observed, and it is clear that spoilage can be prevented.

  On the other hand, lime nitrogen is added to the sterilized residual slurry after sterilization so as to be 0.31 mass / volume% or less so that the nitrogen concentration derived from calcium cyanamide contained in the lime nitrogen is 0.063 mass% or less. In the sample solutions of Comparative Examples 1 to 4, white mold is propagated, and it is clear that it is not possible to prevent decay.

Claims (2)

Bioethanol is produced by saccharifying a substrate made of rice straw with a saccharifying enzyme in the same tank, fermenting with a fermenting bacterium to obtain a fermentation solution, and distilling the fermentation solution to obtain ethanol. In the method of recovering and storing a distillation residue slurry left after distillation of the fermentation solution,
Adding calcium cyanamide to the distillation residue slurry so that the concentration of nitrogen derived from the calcium cyanamide is in the range of 0.08 to 0.8 mass%,
The distillation residue slurry has a C / N ratio in the range of 2-20 and a biochemical oxygen demand in the range of 30-150 mg / g, and the fermentation process results from a saccharification process of the substrate. Performing the conversion of sugar to ethanol to 60-70 % ,
A method for preserving a distillation residue slurry.
  The preservation method of the residual distillation slurry according to claim 1, wherein lime nitrogen is added to the residual distillation slurry so as to have a concentration in a range of 0.4 to 4% by mass / volume. Method.

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