Method for continuously recovering phosphorus and protein from biologically derived components

Abstract

This method for continuously recovering phosphorus and protein from biologically derived components comprises: a first separation step for dissolving a phosphorus component by setting the conditions to be acidic for the biologically derived components which contain protein and the phosphorus component, and performing solid-liquid separation to obtain a first supernatant containing the phosphorus component that has been ionized and a precipitate containing the protein; a second separation step for generating an insoluble salt containing the phosphorus component by setting the conditions to be basic for the first supernatant, and performing solid-liquid separation to obtain a second supernatant and the insoluble salt containing the phosphorus component; a third separation step for mixing the precipitate containing the protein with the second supernatant, dissolving the protein by setting the conditions to be basic for the obtained mixture, and performing solid-liquid separation to obtain a third supernatant containing the protein; and a fourth separation step for performing solid-liquid separation to obtain a fourth supernatant and the protein that has been insolubilized by setting the conditions to be acidic for the third supernatant.

Description

Continuous recovery method for phosphorus and protein from biologically derived components

[0001] This invention relates to a method for the continuous recovery of phosphorus and protein from biologically derived components.

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

[0003] Patent Document 1 provides a method for recovering protein and phosphorus from rice by-products. Patent Document 1 includes a phosphorus separation step in which phosphorus is dissolved in the rice by-products under acidic conditions and solid-liquid separated into a first supernatant containing phosphate ions and a precipitate containing protein; a phosphorus recovery step in which phosphate is generated in the first supernatant under basic conditions and separated into a phosphate and a second supernatant to recover the phosphate; a protein separation step in which the precipitate containing protein and the second supernatant are mixed, the protein is dissolved under basic conditions and a third supernatant containing protein is separated; and a protein recovery step in which the insoluble protein is recovered in the third supernatant under acidic conditions.

[0004] Patent No. 5819601

[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.

[0007] The present invention provides a method for the continuous recovery of phosphorus and protein from biologically derived components, comprising: a first separation step of dissolving the phosphorus component in a biologically derived component containing protein and phosphorus under acidic conditions, and separating the ionized phosphorus component into a first supernatant containing the phosphorus component and a precipitate containing the protein; a second separation step of generating an insoluble salt containing the phosphorus component in the first supernatant under basic conditions, and separating the insoluble salt containing the phosphorus component into a second supernatant; a third separation step of mixing the precipitate containing the protein with the second supernatant, dissolving the protein under basic conditions, and separating the third supernatant containing the protein into a solid-liquid mixture; and a fourth separation step of separating the insoluble protein from the third supernatant under acidic conditions into a fourth supernatant, wherein the first and third separation steps are performed using a decanter-type centrifuge, and the second and fourth separation steps are performed using a disk-type centrifuge.

[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] Furthermore, the continuous recovery method for phosphorus and protein from biological components may include 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.

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

[0012] Furthermore, the aforementioned biologically derived component may be a rice by-product.

[0013] Furthermore, the method for continuously recovering phosphorus and protein from biological components may include a feed manufacturing step in which an acid is added to the solid components separated in the third separation step to neutralize them, and then they are dried to obtain feed.

[0014] According to the present invention, a method for the continuous recovery of phosphorus and protein from biologically derived components that can be commercially implemented can be provided.

[0015] This is a process diagram illustrating a method for the continuous recovery of phosphorus and protein from biologically derived components.

[0016] The continuous recovery method for phosphorus and protein from biological components according to this embodiment (hereinafter also simply referred to as the continuous recovery method) comprises a first separation step, a second separation step, a third separation step, and a fourth separation step. The continuous recovery method enables the continuous recovery of phosphorus and protein from biological components while allowing for commercial implementation.

[0017] The raw materials for the continuous recovery method are not particularly limited as long as they are bio-derived components containing protein and phosphorus components. Bio-derived components include tissues from various plants and animals, such as crustacean shells, legumes, and grasses such as rice and wheat, and rice by-products. Rice by-products are preferred as bio-derived components. Examples of rice by-products include wastewater generated during the processing of pre-washed rice, distillation residue generated when ethanol is produced from rice washing wastewater using starch as the main component, and defatted rice bran obtained as a by-product when oil is extracted from rice bran. The continuous recovery method will be explained below using rice by-products as an example.

[0018] (First Separation Step) In the first separation step, the phosphorus component contained in the rice by-product is dissolved and separated. Specifically, the phosphorus component is dissolved (ionized) by placing the rice by-product under acidic conditions. To create acidic conditions, an acidic solution such as hydrochloric acid can be added to the rice by-product. Since the phosphorus component shows good solubility under strongly acidic conditions, it is preferable to set the pH of the rice by-product to 2.5 to 3.5. Then, solid-liquid separation is performed to separate the supernatant containing the dissolved phosphorus component from the precipitate containing protein.

[0019] The solid-liquid separation in the first separation step is performed using a decanter-type centrifuge. A decanter-type centrifuge is a type of centrifuge that separates solids by causing them to settle, while the liquid remains at the bottom of the rotating cylinder in a gravitational field, and the solid remains around the entire inner surface of the rotating cylinder in a centrifugal field. Decanter-type centrifuges have the characteristic of being able to roughly separate solids and liquids while also being able to process large volumes continuously. Furthermore, the centrifugal acceleration of a decanter-type centrifuge is not limited as long as solid-liquid separation is possible, but is, for example, 2500 to 3500 G.

[0020] (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. Basic conditions can be created by adding an alkaline solution such as NaOH to the supernatant containing the phosphorus component. Since the rice byproduct contains 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. For this reason, 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 the insoluble salt containing phosphorus, the separated insoluble salt can be recovered by drying it using known drying methods such as freeze-drying or spray-drying. This allows for the recovery of the insoluble salt in powder form containing phosphorus. 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, first, water is added to the precipitate separated in the first separation step and mixed. Then, by making this mixture alkaline, the protein contained in the precipitate dissolves. To make it alkaline, a basic substance such as NaOH can be added. 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. 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 makes it alkaline, and the protein in the precipitate dissolves.

[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 to separate 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 to 5.0. The carboxyl groups and amino groups in the proteins are affected by the pH of the solution; at alkaline pH levels, they become -COO － to-NH ２ Therefore, at the acidic pH, -COOH and -NH３ ＋ Therefore, the net charge (sum of positive charges minus 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 purification process is carried out by adding an alkali such as NaOH to adjust the pH to the isoelectric point of the protein. 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-type centrifuge. After separating the protein, the above drying process is performed to obtain a protein with fewer impurities.

[0030] Furthermore, the continuous recovery method may 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. For drying, a known dryer such as a rotary kiln can be used.

[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, the specific flow of the continuous recovery method will be explained. In the following, an example using defatted rice bran as the biological component will be described. 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 inline 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 transported 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 the buffer tank 21, is introduced into the stirring tank 2 by the pump 52. NaOH is further added to the stirring tank 2. The contents of the stirring tank 2 are subjected to basic conditions, and the ionized phosphorus components form insoluble salts. The capacity of the stirring tank 2 is 1.5 to 2 m³. ３ The dwell time is set to approximately 20 to 25 minutes.

[0035] The reaction products in the stirring tank 2 are transported to the centrifuge 12 by the pump 53. The centrifuge 12 is the disc-type centrifuge described above. In the centrifuge 12, the transported reaction products are 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 to 700 kg / h, with a water content of 75 to 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-drying 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 one minute.

[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 the 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 through 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, in addition to the precipitate containing the transported protein, warm water is introduced and stirred and mixed. Also, the supernatant transported from buffer tank 23 described above is added. The introduction of warm water and the supernatant is set to about 4,000 to 5,000 L / h in total. The mixture in buffer tank 22 is carried out to stirring tank 3 by pump 56. In stirring tank 3, further NaOH is added to make the condition basic. Thereby, the protein in the precipitate is dissolved. Stirring tank 3 has a capacity of 10 to 15 m ３ and is set to have a residence time of about 100 to 150 minutes.

[0039] The reactant in stirring tank 3 is transported to centrifuge 13 by pump 58. Centrifuge 13 is the decanter centrifuge described above. By centrifuge 13, it is separated into solid components and a supernatant containing dissolved protein. The former is discharged to buffer tank 25 and the latter is discharged to buffer tank 26. Centrifuge 13 is set, for example, so that the discharge amount of the supernatant containing protein is 4,500 to 5,000 kg.

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

[0041] (Fourth Separation Step) On the other hand, the supernatant containing protein transported to buffer tank 26 is transported to stirring tank 4 by pump 60. In stirring tank 4, further HCl is added so that the content of stirring tank 4 is under acidic conditions. It is adjusted so that the pH becomes the isoelectric point of the protein, and the dissolved protein becomes insoluble and aggregates. Stirring tank 4 has a capacity of 1.5 to 2 m ３ and is set to have a residence time of about 20 to 25 minutes.

[0042] The contents in the stirring tank 4 are transported to the centrifuge 14 by the pump 61. The centrifuge 14 is the disk type centrifuge described above. By the centrifuge 14, solid-liquid separation is performed into the supernatant and the protein, and the former is discharged to the buffer tank 27 and the latter is discharged to the buffer tank 28. The centrifuge 14 is set so that the water content rate of the protein is discharged at about 75 to 85%.

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

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

[0045] The contents in the stirring tank 5 are transported to the centrifuge 15 by the pump 64. The centrifuge 15 is the disk type centrifuge described above. By the centrifuge 15, solid-liquid separation is performed into the supernatant containing the water-soluble non-protein components and the protein, and the former is discharged to the buffer tank 29 and the latter is discharged to the buffer tank 30, respectively. The centrifuge 14 is set so that the water content rate of the protein is discharged at about 75 to 85%.

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

[0047] The protein discharged to 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 water content rate of the protein is dried to 10% or less.

[0048] In the above, rice by-products are taken as an example of the bio-derived component for explanation. However, when other bio-derived components are used as the raw material, in addition to adjusting the pH under acidic conditions, the pH under basic conditions, and the isoelectric point pH, regarding the input amounts of the raw material and water, the residence time in the stirring tanks 1 to 5, etc., they can be appropriately changed according to the raw material.

[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.

[0053] This invention allows for various embodiments and modifications without departing from the broad spirit and scope of the invention. Furthermore, the embodiments described above are for illustrative purposes only and do not limit the scope of the invention. In other words, the scope of the invention is indicated not by the embodiments, but by the claims. Various modifications made within the scope of the claims and the equivalent scope of the meaning of the invention are considered to be within the scope of this invention.

[0054] This application is based on Japanese Patent Application No. 2024-206922, filed on 28 November 2024. The entire specification, claims, and drawings of Japanese Patent Application No. 2024-206922 are incorporated herein by reference.

[0055] 1-5 Agitation tanks 11-15 Centrifugal separators 21-30 Buffer tanks 31-33 Dryers 41 Heat exchangers 42 Hot water boilers 43 In-line mixers 51-66 Pumps 71 Three-way valves

Claims

1. A method for continuous recovery of phosphorus and protein from a biological component, comprising: a first separation step of dissolving the phosphorus component in a biological component containing protein and phosphorus under acidic conditions, and separating the ionized phosphorus component into a first supernatant containing the phosphorus component and a precipitate containing the protein; a second separation step of generating an insoluble salt containing the phosphorus component in the first supernatant under basic conditions, and separating the insoluble salt containing the phosphorus component into a second supernatant; a third separation step of mixing the precipitate containing the protein with the second supernatant, dissolving the protein under basic conditions, and separating the protein into a third supernatant containing the protein; and a fourth separation step of separating the insoluble protein into a fourth supernatant under acidic conditions, wherein solid-liquid separation is performed using a decanter-type centrifuge in the first and third separation steps, and solid-liquid separation is performed using a disk-type centrifuge in the second and fourth separation steps.

2. The method for continuous recovery of phosphorus and protein from biological components according to claim 1, characterized in that the first separation step and the third separation step are performed with a centrifugal acceleration of 2500 to 3500 G for solid-liquid separation.

3. The method for continuous recovery of phosphorus and protein from biological components according to claim 1, characterized in that the second and fourth separation steps are performed with a centrifugal acceleration of 8500 to 9500 G for solid-liquid separation.

4. The method for continuous recovery of phosphorus and protein from biological components according to claim 1, further comprising a purification step of adding acidic electrolyzed water to the protein separated in the fourth separation step to elute water-soluble non-protein components and purify the protein.

5. The method for continuous recovery of phosphorus and protein from a bio-derived component according to claim 1, characterized in that the bio-derived component is a grain.

6. The method for continuous recovery of phosphorus and protein from a bio-derived component according to claim 1, characterized in that the bio-derived component is a rice by-product.

7. A method for continuous recovery of phosphorus and protein from biological components according to claim 5 or 6, characterized by comprising a feed manufacturing step of adding an acid to the solid components separated in the third separation step to neutralize them and drying them to obtain feed.

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