Continuous recovery method for phosphorus and protein from biologically derived components

Abstract

This invention provides a commercially viable method for the continuous recovery of phosphorus and protein from bio-derived components. [Solution] A method for continuously recovering phosphorus and protein from biologically derived components comprises: a first separation step of dissolving the phosphorus component in a biologically derived component containing protein and phosphorus under acidic conditions and separating it into a first supernatant containing ionized phosphorus and a precipitate containing protein; a second separation step of generating an insoluble salt containing phosphorus in the first supernatant under basic conditions and separating it into a second supernatant; a third separation step of mixing the precipitate containing protein with the second supernatant, dissolving the protein under basic conditions and separating the third supernatant containing protein into a fourth supernatant; and a fourth separation step of separating the insoluble protein from the third supernatant under acidic conditions.

Description

Technical Field

[0001] The present invention relates to a method for continuously recovering phosphorus and protein from components derived from living organisms.

Background Art

[0002] Rice by-products such as rice washing wastewater contain useful substances such as protein and phosphorus. Protein is one of the essential nutrients for animals and can be used in the production of essential amino acids that cannot be synthesized in the body, such as functional foods. Phosphorus is a substance that can be used in various fields such as raw materials for chemical fertilizers and food additives. From the perspective of effective utilization of resources, it is desirable to recover and reuse useful substances such as protein and phosphorus from rice by-products such as rice washing wastewater.

[0003] As a method for recovering protein and phosphorus from rice by-products, Patent Document 1 can be cited. In Patent Document 1, rice by-products are made acidic to dissolve phosphorus, and a phosphorus separation step of solid-liquid separation into a first supernatant containing phosphate ions and a precipitate containing protein, a phosphorus recovery step of making the first supernatant basic to generate phosphate and separating and recovering the phosphate into the phosphate and a second supernatant, a protein separation step of mixing the precipitate containing protein and the second supernatant, making it basic to dissolve the protein and separating a third supernatant containing protein, and a protein recovery step of making the third supernatant acidic to recover the insoluble protein are provided.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] While Patent Document 1 can be implemented at the laboratory level, there is room for improvement for commercial implementation.

[0006] The present invention has been made in view of the above matters, and its object is to provide a method for the continuous recovery of phosphorus and protein from biological components that is commercially feasible. [Means for solving the problem]

[0007] The method for continuous recovery of phosphorus and protein from biologically derived components according to the present invention is: A first separation step involves dissolving the phosphorus component in a bio-derived component containing protein and phosphorus components under acidic conditions, and then performing solid-liquid separation to separate it into a first supernatant containing the ionized phosphorus component and a precipitate containing protein. A second separation step involves subjecting the first supernatant to basic conditions to generate an insoluble salt containing the phosphorus component, and then performing solid-liquid separation between the insoluble salt containing the phosphorus component and the second supernatant. A third separation step involves mixing the precipitate containing the protein with the second supernatant, dissolving the protein under basic conditions, and performing solid-liquid separation on the third supernatant containing the protein. The method comprises a fourth separation step of separating the protein, which has become insoluble in the third supernatant under acidic conditions, from a fourth supernatant through solid-liquid separation, In the first and third separation steps, a decanter-type centrifuge is used to separate the solid and liquid. In the second and fourth separation steps, solid-liquid separation is performed using a disk-type centrifuge. It is characterized by the following:

[0008] Furthermore, it is preferable to perform solid-liquid separation in the first and third separation steps using a centrifugal acceleration of 2500 to 3500 G.

[0009] Furthermore, in the second and fourth separation steps, it is preferable to perform solid-liquid separation with a centrifugal acceleration of 8500 to 9500 G.

[0010] Further, a purification step may be provided in which acidic electrolyzed water is added to the protein separated in the fourth separation step to elute water-soluble non-protein components, thereby purifying the protein.

[0011] Also, the bio-derived component may be a grain.

[0012] Also, the bio-derived component may be a rice by-product.

[0013] Further, a feed production step may be provided in which an acid is added to and neutralized with the solid component separated in the third separation step, followed by drying to obtain feed.

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a method for continuously recovering phosphorus and protein from a bio-derived component that can be commercially implemented.

Brief Description of the Drawings

[0015] [Figure 1] It is a process diagram for explaining a method for continuously recovering phosphorus and protein from a bio-derived component. [Figure 2] It is a process diagram for explaining a method for continuously recovering phosphorus and protein from a bio-derived component.

Embodiments for Carrying Out the Invention

[0016] The method for continuously recovering phosphorus and protein from a bio-derived component according to the present embodiment (hereinafter, also simply referred to as the continuous recovery method) includes a first separation step, a second separation step, a third separation step, and a fourth separation step. The continuous recovery method can continuously recover phosphorus and protein from a bio-derived component while enabling commercial implementation.

[0017] The raw material for the continuous recovery method is not particularly limited as long as it is a biological component containing protein and phosphorus components. Biological components are tissues of various animals and plants, such as the shells of crustaceans, grains of the legume family, rice, wheat, etc. of the Poaceae family, and rice by-products. As the biological component, rice by-products are preferred. Examples of rice by-products include, for example, the rice washing wastewater generated during the processing of non-washed rice, the distillation residue generated when ethanol is produced using the solid component mainly composed of starch from the rice washing wastewater as the raw material, and defatted rice bran obtained as a by-product when oil is extracted from rice bran. Hereinafter, taking rice by-products as an example, the continuous recovery method will be described.

[0018] (The first separation step) In the first separation step, the phosphorus component contained in the rice by-products is dissolved and separated. Specifically, by making the rice by-products under acidic conditions, the phosphorus component is dissolved (ionized). To make the acidic conditions, an acidic solution such as hydrochloric acid can be added to the rice by-products. Since the phosphorus component shows good solubility under strong acidic conditions, it is preferable to set the pH of the rice by-products to 2.5 - 3.5. Then, solid-liquid separation is performed into the supernatant in which the phosphorus component is dissolved and the precipitate containing protein.

[0019] The solid-liquid separation in the first separation step is performed using a decanter centrifuge. A decanter centrifuge is a centrifuge that performs solid-liquid separation by sedimenting solids, where in the gravitational field, the liquid stays at the lower part inside the rotating cylinder, while in the centrifugal force field, it stays on the entire circumference of the inner surface of the rotating cylinder. A decanter centrifuge has the characteristic of being able to perform continuous large-capacity processing while roughly separating solids and liquids. Also, the centrifugal acceleration of the decanter centrifuge is not limited as long as solid-liquid separation is possible, but for example, it is 2500 - 3500G.

[0020] (The second separation step) In the second separation step, the dissolved phosphorus component is separated by converting it into insoluble salts. Specifically, the supernatant containing the phosphorus component separated in the first separation step is subjected to basic conditions to generate insoluble salts containing phosphorus, such as phosphates and phytic acid. The ionized phosphorus component in the supernatant forms insoluble salts containing phosphorus under basic conditions. This can be achieved by adding an alkaline solution such as NaOH to the supernatant containing phosphorus to create basic conditions. Since rice by-products contain metal ions such as potassium and magnesium, phosphate ions and phytic acid combine with these metal ions to form insoluble salts such as potassium phosphate, magnesium phosphate, and phytic acid. Therefore, it is not necessary to separately add auxiliary raw materials such as MAP (magnesium ammonium phosphate) or HAP (calcium hydroxyapatite), which are generally used for phosphorus recovery. Then, by solid-liquid separation of the generated insoluble salts containing phosphorus from the supernatant, phosphates can be separated and recovered.

[0021] The solid-liquid separation in the second separation step is performed using a disk-type centrifuge. A disk-type centrifuge has a structure in which multiple conical disks are stacked around a rotating shaft, allowing for large-scale and high-speed separation even in a small space. Furthermore, disk-type centrifuges can also separate liquids with small specific gravity differences, and have the characteristic of being extremely high separation performance. The centrifugal acceleration of a disk-type centrifuge is not limited as long as solid-liquid separation is possible, but for example, it is 8500 to 9500 G.

[0022] Furthermore, in the recovery of insoluble salts containing phosphorus components, the separated insoluble salts can be recovered by drying them using known drying methods such as freeze-drying or spray-drying. This allows for the recovery of powdered insoluble salts containing phosphorus components. It is preferable to use a dryer suitable for subsequent applications.

[0023] (Third separation step) In the third separation step, the protein is dissolved and separated from the precipitate containing the protein separated in the first separation step. Specifically, water is first added to the precipitate separated in the first separation step and mixed. Then, the protein contained in the precipitate is dissolved by creating basic conditions. Basic conditions can be achieved by adding a basic substance such as NaOH. Furthermore, if a granular alkaline substance such as NaOH is used, the volume of the solution will not increase. After the protein has dissolved, the supernatant containing the dissolved protein can be separated from the solid component by solid-liquid separation of the supernatant and the precipitate. Note that the supernatant separated in the second separation step may be used as the water to be added. In this case, if an excess of basic substance was added in the second separation step, it is not necessary to add another basic substance in the third separation step. Mixing the supernatant separated in the second separation step with the precipitate separated in the first separation step creates basic conditions and dissolves the protein.

[0024] The solid-liquid separation in the third separation step is performed using a decanter-type centrifuge. The decanter-type centrifuge is the same as described above.

[0025] (Fourth separation step) In the fourth separation step, the proteins contained in the supernatant separated in the third separation step are made insoluble and separated. Specifically, the supernatant containing the proteins separated in the third separation step is subjected to acidic conditions, separating the insoluble proteins from the supernatant. To create acidic conditions, an acidic solution such as hydrochloric acid is added to the supernatant containing the proteins to adjust the pH of the supernatant to 3.5-5.0. The carboxyl groups and amino groups in the proteins are separated by the pH of the solution; at alkaline pH levels, they become -COO - And -NH2, and at acidic pH levels, -COOH and -NH3 +Therefore, the net charge (sum of positive charges - sum of negative charges) can be negative, zero, or positive depending on the pH of the solution, and the pH at which the net charge becomes zero is called the isoelectric point of the protein. In general, the solubility of water-soluble proteins in water is minimized at the isoelectric point. At the isoelectric point, the solution becomes electrically neutral, and the electrostatic repulsion between protein molecules weakens, causing solubility to decrease. As a result, the molecules aggregate and precipitate. After the protein precipitates, the protein can be separated and recovered by solid-liquid separation of the precipitated protein from the supernatant.

[0026] The solid-liquid separation in the fourth separation step is performed using a disk-type centrifuge. The disk-type centrifuge is the same as described above.

[0027] Furthermore, for protein recovery, the separated protein fraction can be recovered by drying it using known drying methods such as freeze-drying or spray-drying. This allows for the recovery of powdered protein. In order to minimize the deterioration of the quality of the recovered protein, it is preferable to use a spray-drying dryer.

[0028] Furthermore, it is preferable to recover the protein separated in the fourth separation step after the purification step. This is because the protein fraction separated in the fourth separation step contains a considerable amount of water-soluble non-protein components other than protein, specifically minerals, carbohydrates, amino acids, and other amine compounds.

[0029] In the purification process, acidic electrolyzed water is added to the protein fraction separated in the fourth separation step to elute the water-soluble non-protein components contained in the protein fraction. The pH in the purification process is adjusted to the pH of the isoelectric point of the protein by adding an alkali such as NaOH. After the purification process, solid-liquid separation is performed to separate the supernatant containing water-soluble non-protein components from the protein. This solid-liquid separation is performed using a disk centrifuge. After separating the protein, the above drying process is performed to obtain a protein with fewer impurities.

[0030] The system may also include a feed manufacturing process for producing feed from the solid components separated in the third separation process. The solid components separated in the third separation process contain dietary fiber, and if the raw material is defatted rice bran, they also contain protein, making them a valuable resource for animal feed. Since these solid components are strongly alkaline, feed can be obtained by neutralizing them with an acid and then drying them. Hydrochloric acid or the like can be used as the acid, and drying can be done using a known dryer such as a rotary kiln.

[0031] Next, referring to the process diagrams of the continuous recovery method for phosphorus and protein from biological components shown in Figures 1 and 2, we will explain the specific flow of the continuous recovery method. Below, we will explain an example using defatted rice bran as the biological component. In this process, the entire process is continuous, and in addition to the input of defatted rice bran, etc., into the stirring tank 1 described later, the operation of stirring tanks 1 to 5, pumps 51 to 66, centrifuges 11 to 15, dryers 31 to 33, heat exchanger 41, hot water boiler 42 and in-line mixer 43, and pH adjustment in each process are all operated based on control by a control device not shown.

[0032] (First separation step) In addition to the defatted rice bran, which is the raw material, water and hydrochloric acid are added to the stirring tank 1. The contents of the stirring tank 1 are subjected to acidic conditions, causing the phosphorus component of the defatted rice bran to dissolve and ionize. The capacity of the stirring tank 1 is, for example, 1.5 to 2 m³. 3 The raw material input is set to 400-600 kg / h, the water input to 4,000-5,000 L / h (including the recycled water described later), and the residence time to approximately 15-20 minutes.

[0033] The reaction products in the stirring tank 1 are transported to the centrifuge 11 by the pump 51. The centrifuge 11 is the decanter-type centrifuge described above. In the centrifuge 11, the reaction products are separated into a first supernatant containing phosphorus and a precipitate containing protein. The former is discharged to the buffer tank 21, and the latter to the buffer tank 22. The centrifuge 11 is set to discharge the protein-containing precipitate at a rate of 1,100 to 1,200 kg / h with a water content of 65 to 75%.

[0034] (Second separation step) The supernatant containing phosphorus components, transported to buffer tank 21, is transferred to agitated tank 2 by pump 52. NaOH is further added to agitated tank 2. The contents of agitated tank 2 become alkaline, and the ionized phosphorus components form insoluble salts. The capacity of agitated tank 2 is 1.5-2 m³. 3 The dwell time is set to approximately 20-25 minutes.

[0035] The reaction product in the stirring tank 2 is transported to the centrifuge 12 by the pump 53. The centrifuge 12 is the disc-type centrifuge described above. In the centrifuge 12, the reaction product is separated into a supernatant and an insoluble salt containing phosphorus components. The former is discharged to the buffer tank 23, and the latter to the buffer tank 24. The centrifuge 12 is set, for example, to discharge insoluble salt at a rate of 500-700 kg / h, with a water content of 75-85%.

[0036] The insoluble salt containing phosphorus, transported to the buffer tank 24, is then transported to the dryer 31 by the pump 55. In the dryer 31, the insoluble salt containing phosphorus is dried, and granular insoluble salt is recovered. The insoluble salt recovered here mainly consists of phytic acid, magnesium phosphate, and potassium phosphate. The dryer is, for example, a spray dryer with a drying temperature of 220-280°C, an exhaust air temperature of 80-120°C, and an airflow of 110-150 Nm³. 3 The condition is set to approximately / minutes.

[0037] Furthermore, the supernatant transported to the buffer tank 23 is transported by the pump 54 through the three-way valve 71 to the stirring tank 1 or buffer tank 22 as reused water. The supernatant transported to the buffer tank 22 is heated by the heat exchanger 41 during transport. Hot water is circulated to the heat exchanger 41 from the hot water boiler 42 via the pump 57, thereby heating the supernatant.

[0038] (Third separation step) In buffer tank 22, the transported protein-containing precipitate is mixed with hot water, which is then stirred and agitated. The supernatant transported from buffer tank 23 is also added. The combined flow rate of hot water and supernatant is set to approximately 4,000-5,000 L / h. The mixture in buffer tank 22 is then transferred to stirring tank 3 by pump 56. NaOH is further added to stirring tank 3 to create basic conditions. This dissolves the protein in the precipitate. Stirring tank 3 has a capacity of 10-15 m³. 3 The dwell time is set to approximately 100-150 minutes.

[0039] The reaction product in the stirring tank 3 is transported to the centrifuge 13 by the pump 58. The centrifuge 13 is the decanter-type centrifuge described above. The centrifuge 13 separates the solid components from the supernatant containing dissolved protein, discharging the former to the buffer tank 25 and the latter to the buffer tank 26. The centrifuge 13 is set, for example, so that the discharge volume of the supernatant containing protein is 4,500 to 5,000 kg.

[0040] HCl is added to the solid components in the buffer tank 25, and the mixture is transported to the inline mixer 43 by the pump 59. The solid components are neutralized by the inline mixer 43. The neutralized solid components are discharged to the dryer 32. The dryer 32 is, for example, a rotary kiln. By drying the solid components in the dryer 32 to a moisture content of about 5-10%, feed can be produced.

[0041] (Fourth separation step) Meanwhile, the supernatant containing protein, which has been transported to the buffer tank 26, is transported to the stirring tank 4 by the pump 60. Further HCl is added to the stirring tank 4, making its contents acidic. The pH is adjusted to the isoelectric point of the protein, causing the dissolved protein to become insoluble and aggregate. The stirring tank 4 has a capacity of 1.5-2 m³. 3 The dwell time is set to approximately 20-25 minutes.

[0042] The contents of the stirring tank 4 are transported to the centrifuge 14 by the pump 61. The centrifuge 14 is the disc-type centrifuge described above. The centrifuge 14 separates the supernatant and protein into solid and liquid components, with the former being discharged to the buffer tank 27 and the latter to the buffer tank 28. The centrifuge 14 is set so that the protein is discharged with a water content of approximately 75-85%.

[0043] The supernatant discharged into the buffer tank 27 is then discharged by the pump 62 and treated as waste liquid.

[0044] Acidic electrolyzed water is added to the protein transported to buffer tank 28, and the protein is then transported to stirring tank 5 by pump 63. In stirring tank 5, water-soluble non-protein components attached to the protein are eluted. To suppress the dissolution of the precipitated protein, the pH is adjusted to the isoelectric point of the protein.

[0045] The contents of the stirring tank 5 are transported to the centrifuge 15 by the pump 64. The centrifuge 15 is the disc-type centrifuge described above. The centrifuge 15 separates the supernatant containing water-soluble non-protein components from the protein, and the former is discharged to the buffer tank 29, and the latter to the buffer tank 30. The centrifuge 14 is set so that the protein is discharged with a water content of approximately 75-85%.

[0046] The supernatant liquid discharged into the buffer tank 29 is then discharged by the pump 65 and treated as waste liquid.

[0047] The protein discharged into the buffer tank 30 is transported to the dryer 33 by the pump 66. In the dryer 33, the protein is dried and granular protein is recovered. It is desirable to set the dryer so that the moisture content of the protein is reduced to 10% or less.

[0048] In the above explanation, rice by-products were used as an example of bio-derived components. However, when using other bio-derived components, adjustments to pH under acidic conditions, pH under basic conditions, and isoelectric point pH, as well as the amount of raw materials and water added, and the residence time in stirring tanks 1-5, can be appropriately changed depending on the raw materials.

[0049] In the continuous recovery method according to this embodiment, as described above, a decanter-type centrifuge is used in the first and third separation steps, and a disk-type centrifuge is used in the second and fourth separation steps. The disk-type centrifuge has superior separation performance compared to the decanter-type centrifuge. On the other hand, the decanter-type centrifuge has superior processing capacity and processing speed compared to the disk-type centrifuge.

[0050] In the second and fourth separation steps, the phosphorus component and protein, which become the final product after separation and drying, are separated, respectively. Therefore, a disk-type centrifuge with excellent separation performance is used to obtain phosphorus components and proteins with fewer impurities.

[0051] Furthermore, in the first and third separation steps, a decanter-type centrifuge, which offers superior processing capacity and speed, is used. If a disk-type centrifuge were used in the first and third separation steps, solid-liquid separation would become the rate-limiting step, leading to a decrease in the overall process speed. This is particularly noticeable when a disk-type centrifuge is used in the first separation step, causing a bottleneck in the flow of materials to be processed in the second through fourth separation steps.

[0052] In the continuous recovery method according to this embodiment, in order to maintain the quality of the recovered phosphorus and protein as products, while increasing the processing capacity and processing speed and enabling commercial implementation, a decanter-type centrifuge is used in the first and third separation steps, and a disk-type centrifuge is used in the second and fourth separation steps. [Explanation of symbols]

[0053] 1-5 Agitation tanks 11-15 Centrifugal separator 21-30 Buffer Tank 31~33 Dryer 41 Heat exchanger 42 Hot water boiler 43 Inline Mixer 51-66 Pumps 71 Three-way valve

Claims

1. A first separation step involves dissolving the phosphorus component in a bio-derived component containing protein and phosphorus components under acidic conditions, and then performing solid-liquid separation to separate it into a first supernatant containing the ionized phosphorus component and a precipitate containing protein. A second separation step involves generating an insoluble salt containing the phosphorus component by subjecting the first supernatant to basic conditions, and then separating the insoluble salt containing the phosphorus component from the second supernatant using a solid-liquid separation method. A third separation step involves mixing the protein-containing precipitate with the second supernatant, dissolving the protein under basic conditions, and performing solid-liquid separation on the third supernatant containing the protein. The method comprises a fourth separation step of separating the protein, which has become insoluble in the third supernatant under acidic conditions, from a fourth supernatant through solid-liquid separation, In the first and third separation steps, solid-liquid separation is performed using a decanter-type centrifuge. In the second and fourth separation steps, solid-liquid separation is performed using a disk-type centrifuge. A method for the continuous recovery of phosphorus and protein from biologically derived components, characterized by the features described above.

2. In the first and third separation steps, solid-liquid separation is performed with a centrifugal acceleration of 2500 to 3500 G. A method for continuously recovering phosphorus and protein from biologically derived components as described in feature 1.

3. In the second and fourth separation steps, solid-liquid separation is performed with a centrifugal acceleration of 8500 to 9500 G. A method for continuously recovering phosphorus and protein from biologically derived components as described in feature 1.

4. The method further includes a purification step in which acidic electrolyzed water is added to the protein separated in the fourth separation step to elute water-soluble non-protein components and purify the protein. A method for continuously recovering phosphorus and protein from biologically derived components as described in feature 1.

5. The aforementioned bio-derived component is a grain. A method for continuously recovering phosphorus and protein from biologically derived components as described in feature 1.

6. The aforementioned biological component is a rice by-product. A method for continuously recovering phosphorus and protein from biologically derived components as described in feature 1.

7. The feed manufacturing process includes adding an acid to the solid components separated in the third separation step to neutralize them, and then drying them to obtain feed. A method for continuous recovery of phosphorus and protein from biologically derived components according to feature 5 or 6.

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