A method for treating wastewater in bone gelatin production.

Abstract

This invention belongs to the field of wastewater treatment technology, specifically disclosing a method for treating wastewater in bone gelatin production. The method first treats the supernatant from the wastewater after separating calcium phosphate from the acid leaching process using an ultrafiltration membrane, obtaining a concentrated phase and a clear phase. 60-70% of the clear phase is then mixed with concentrated sulfuric acid to produce a mixture containing hydrochloric acid and calcium sulfate. This mixture is filtered to obtain solid calcium sulfate and a hydrochloric acid-containing filtrate, which is used in the acid leaching process. Using this method, chloride ions in the wastewater are converted into hydrochloric acid, which, after treatment and purification, can be returned to the acid leaching process, reducing the amount of hydrochloric acid used in production. Furthermore, calcium sulfate is also obtained. Because the supernatant from the wastewater after separating calcium phosphate from the acid leaching process is not discharged but recycled within the production system, the yield of calcium phosphate is increased, thus increasing economic benefits.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and specifically to a method for treating wastewater in bone gelatin production. Background Technology

[0002] The existing process for preparing bone gelatin from bone raw materials mainly includes steps such as bone crushing, degreasing, sorting, acid soaking, liming, and neutralization washing. The acid soaking step is the process of converting bone particles into the desired osteotin. The acid soaking step removes minerals (such as Ca3(PO4)2 and CaCO3) and other salts from the degreased bone, while simultaneously releasing collagen, thus generating osteotin. The main component of osteotin is collagen, but it also contains mucopolysaccharides and small amounts of other proteins. Currently, when producing gelatin from bone particles, the acid soaking step generally uses concentrated hydrochloric acid. Depending on the process requirements and ambient temperature, different concentrations of dilute hydrochloric acid are prepared and then added to an acid soaking tank containing a fixed mass of bone particles. Continuous acid soaking is carried out until the inorganic matter in the bone particles is removed, yielding qualified osteotin. The qualified osteotin then proceeds to the liming process. The main reactions involved in acid soaking with hydrochloric acid are:

[0003] Ca3(PO4)2+4HCl-----Ca(H2PO4)2+2CaCl2

[0004] CaCO3+2HCl-----CaCl2+H2O+CO2↑.

[0005] The wastewater from acid leaching is first treated with calcium hydroxide to extract calcium dihydrogen phosphate, yielding calcium dicalcium phosphate. The clarified supernatant then enters the wastewater treatment system, where it mixes with wastewater from the hydraulic transport of bone granules after acid leaching, wastewater from the liming process, wastewater from the neutralization process, and wastewater from the gelatin production workshop, all before being treated together in the wastewater environmental protection system. In actual operation, the wastewater treatment system meets emission standards for ammonia nitrogen, total nitrogen, and COD in the discharged wastewater. However, the chloride ion content in the treated wastewater is high, reaching over 6000 ppm. This is mainly because during acid leaching, the chlorides generated by the reaction of hydrochloric acid with inorganic matter in the bone granules dissolve in the water, resulting in a large amount of calcium chloride in the wastewater. For example, the calcium chloride content in the supernatant after calcium dicalcium phosphate extraction can reach 50-60 kg / m³. 3 It has an extremely high chloride ion content.

[0006] With the continuous improvement of environmental emission standards, the green and environmentally friendly treatment of bone gelatin wastewater will become an urgent problem to be solved. Summary of the Invention

[0007] To address one of the aforementioned technical problems in the prior art, the present invention provides a method for treating wastewater in bone gelatin production, comprising the following steps:

[0008] (1) The supernatant after separating the dicalcium phosphate product from the wastewater in the acid leaching process is treated by ultrafiltration membrane to obtain concentrated phase and clear phase respectively;

[0009] (2) Take 60-70% of the clear phase and mix it with concentrated sulfuric acid to react and produce a mixed solution containing hydrochloric acid and calcium sulfate;

[0010] (3) The mixture is filtered to obtain calcium sulfate solid and hydrochloric acid filtrate, and the hydrochloric acid filtrate is used in the acid leaching process.

[0011] As a specific technical solution of the present invention, the ultrafiltration membrane flux is 5-10 L / (m²). 2 ˙h), aperture 1000 Daltons.

[0012] As a specific technical solution of the present invention, in step (2), the amount of concentrated sulfuric acid used is determined by the following steps:

[0013] S1: Calculate the amount of concentrated sulfuric acid to be used based on the calcium ion concentration and chloride ion concentration in the clear phase, respectively:

[0014] The amount of concentrated sulfuric acid used, M1, is calculated based on the calcium ion concentration using the following formula:

[0015] M1(m 3 ) = V 步骤(2)清相 ×0.95×Ca 2+ Concentration ÷ 40 ÷ 1.84;

[0016] Where: 0.95 is the correction constant, Ca 2+ The unit of concentration is tons per 100m³ 3 V 步骤(2)清相 The unit is m 3 ;

[0017] The amount of concentrated sulfuric acid used, M2, is calculated based on the chloride ion concentration. The formula is as follows:

[0018] M2(m 3 ) = V 步骤(2)清相 ×(Cl - Concentration -0.25) ÷ 71 ÷ 1.84;

[0019] Where: 0.25 is the correction constant, Cl - The unit of concentration is tons per 100m³ 3 V 步骤(2)清相 The unit is m 3 ;

[0020] S2: Add concentrated sulfuric acid based on the smaller of the calculated amounts of M1 and M2.

[0021] As a specific technical solution of the present invention, the calcium sulfate solid is washed with the residual clear phase to obtain the calcium sulfate product.

[0022] As a specific technical solution of the present invention, when there is still residue after washing the calcium sulfate solid with the clear phase, the remaining clear phase is used to react with calcium oxide to prepare calcium hydroxide, and the calcium hydroxide is used to extract dicalcium phosphate product from the wastewater of the acid leaching process.

[0023] As a specific technical solution of the present invention, the hydrochloric acid filtrate is purified to obtain a dilute hydrochloric acid product, which is used in the acid leaching process.

[0024] As a preferred embodiment, the purification includes primary plate and frame filtration, sulfate removal treatment, and secondary plate and frame filtration.

[0025] As a specific technical solution of the present invention, the reagent used for the sulfate removal treatment is barium chloride.

[0026] As a preferred embodiment, the sulfate removal treatment includes:

[0027] (1) After the hydrochloric acid-containing filtrate is filtered once by plate and frame filter, the concentration of sulfate ions is measured and the sulfate ion content is calculated.

[0028] (2) According to Ba 2+ SO4 2- Barium chloride was weighed in a molar ratio of 1:1.

[0029] (3) Add barium chloride to the hydrochloric acid filtrate after the first plate and frame filtration, stir and react, and then send the reaction mixture to the plate and frame filter for a second plate and frame filtration to obtain solid barium sulfate product. The resulting filtrate is dilute hydrochloric acid, which is sent to the acid leaching process for use.

[0030] As a preferred embodiment, the supernatant after separating the dicalcium phosphate product from the wastewater in the acid leaching process is first adjusted to pH 4.0-4.2, and then subjected to ultrafiltration treatment using an ultrafiltration membrane.

[0031] In a preferred embodiment, the concentrated phase obtained from the ultrafiltration treatment is used as animal feed. Ultrafiltration primarily removes oils and proteins from the supernatant to form a concentrated phase, reducing total nitrogen, COD, and suspended solids. The concentrated phase obtained after ultrafiltration of the supernatant can be used as feed.

[0032] The wastewater treatment method provided by this invention for bone gelatin production separates the supernatant from the acid leaching process wastewater after separating dicalcium phosphate from the wastewater. This process avoids mixing the supernatant with other wastewater generated during bone gelatin processing and transferring it to a wastewater treatment system, thus completely resolving the issue of high chloride ion content in the wastewater discharged from the wastewater treatment system. Using this method, chloride ions in the wastewater are converted into hydrochloric acid, which, after purification, can be returned to the acid leaching process, reducing the amount of hydrochloric acid used in production. Furthermore, calcium sulfate is also obtained. Because the supernatant from the acid leaching process wastewater after separating dicalcium phosphate is not discharged but recycled within the production system, the yield of dicalcium phosphate is increased, leading to greater economic benefits. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0034] definition

[0035] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly used in the field to which this invention pertains.

[0036] The following embodiments are provided to aid in understanding the present invention. However, it should be understood that these embodiments are for illustrative purposes only and do not constitute any limitation. The actual scope of protection of the present invention is set forth in the claims. It should be understood that any modifications and changes can be made without departing from the spirit of the present invention.

[0037] Example 1

[0038] This embodiment provides a method for treating the supernatant after separating dicalcium phosphate from wastewater in the acid soaking process during bone gelatin industrial production.

[0039] Previously, the supernatant from the acid pickling process after separating dicalcium phosphate from the wastewater was mixed with wastewater from the bone gelatin processing, wastewater from the liming process, wastewater from the neutralization process, and wastewater from the glue-making workshop, and then sent to the wastewater environmental protection system for treatment. In actual operation, the wastewater environmental protection system ensured that the ammonia nitrogen, total nitrogen, and COD in the discharged wastewater met the discharge standards, and the chloride ion content in the treated wastewater was maintained at around 6000 ppm.

[0040] On a daily basis, the supernatant generated after separating dicalcium phosphate from the wastewater in the acid leaching process is approximately 1300 m³. 3 After merging with other wastewater, the daily wastewater treatment system processes approximately 6000 m³ of wastewater. 3 .

[0041] During the experiment, approximately 1300m will be generated. 3 The supernatant after separating dicalcium phosphate from the wastewater in the acid leaching process is treated separately. During this process, the wastewater environmental protection treatment system ensures that the ammonia nitrogen, total nitrogen, and COD in the discharged wastewater meet the emission standards, and the chloride ion content in the treated wastewater is reduced to approximately 550 ppm.

[0042] The generated approximately 1300m 3 The method for treating the supernatant after separating dicalcium phosphate from the wastewater in the acid leaching process includes the following steps:

[0043] The pH of the supernatant was first adjusted from 4.4-4.5 to 4.0-4.2 using a metering pump, and then it entered the ultrafiltration membrane for ultrafiltration. The ultrafiltration membrane flux used was 8 L / (m²). 2 (˙h), pore size 1000 Daltons. After ultrafiltration, concentrated phase and clear phase are obtained separately, the concentrated phase is about 100 μm. 3 As animal feed, approximately 1200m³ 3 The calcium ion concentration in the clear phase was 2.157 tons / 100m³. 3 The chloride ion concentration is 3.950 tons / 100m³. 3 .

[0044] Take 800m 3 The clear phase is pumped into a continuous reactor and mixed with 98% concentrated sulfuric acid. The amount of concentrated sulfuric acid used is determined by the following steps:

[0045] S1: Calculate the amount of concentrated sulfuric acid to be used based on the calcium ion concentration and chloride ion concentration in the clear phase, respectively:

[0046] The amount of concentrated sulfuric acid used, M1, is calculated based on the calcium ion concentration using the following formula:

[0047] M1(m 3 ) = V 步骤(2)清相 ×0.95×Ca 2+ Concentration ÷ 40 ÷ 1.84;

[0048] Where: 0.95 is the correction constant, Ca 2+ The unit of concentration is tons per 100m³ 3 V 步骤(2)清相 The unit is m 3 ;

[0049] The calculation shows that:

[0050] M1(m 3 )=800×0.95×2.157÷40÷1.84=22..27;

[0051] The amount of concentrated sulfuric acid used, M2, is calculated based on the chloride ion concentration. The formula is as follows:

[0052] M2(m 3 ) = V 步骤(2)清相 ×(Cl - Concentration -0.25) ÷ 71 ÷ 1.84;

[0053] Where: 0.25 is the correction constant, Cl - The unit of concentration is tons per 100m³ 3 V 步骤(2)清相 The unit is m 3 ;

[0054] The calculation shows that:

[0055] M2(m 3 = 800 × (3.950 - 0.25) ÷ 71 ÷ 1.84 = 22.66;

[0056] S2: The smaller of the calculated amounts, M1 and M2, is used: 22.27m 3 Add concentrated sulfuric acid as needed;

[0057] The 22.27m was produced using a flow feed method. 3 Concentrated sulfuric acid was added to 800m 3 In the clear phase, the reaction is continuously stirred to produce a mixed solution containing hydrochloric acid and calcium sulfate;

[0058] The resulting mixture was filtered using a belt filter, and the filter cake consisted of calcium sulfate. The remaining 280 mg / L of the clarified phase was then used for filtration. 3 The calcium sulfate solids are washed, and then the washed calcium sulfate product is transferred to the calcium sulfate stockpile. The filtrate is a hydrochloric acid solution with a concentration of 3.73 wt%. The filtrate is filtered for the first time using a plate and frame filter press, and then fed into a buffer tank.

[0059] SO4 in the hydrochloric acid solution after the first plate and frame filtration 2- The concentration is 0.35 wt%. Because calcium sulfate is a trace element and affects the quality and yield of gelatin, it is necessary to remove the sulfate ions (SO4). 2- Barium chloride was added to the hydrochloric acid solution after the first plate and frame filtration to remove sulfate ions (SO4). 2- ), where the amount of barium chloride used is according to Ba 2+ SO4 2-Barium chloride was added in batches at a molar ratio of 1:1 to the hydrochloric acid solution after the first plate and frame filtration. The mixture was stirred and then sent to a plate and frame filter press for a second filtration to obtain solid barium sulfate. The solid barium sulfate was then transported to the stockpile. The resulting filtrate was dilute hydrochloric acid, containing SO42-. 2- The concentration is 60 ppm, and it is sent to the acid leaching process for use.

[0060] The remaining 120m 3 The clear phase is used to react with calcium oxide to prepare calcium hydroxide, and the obtained calcium hydroxide is used to extract dicalcium phosphate from the wastewater of the acid leaching process.

[0061] The benefits that can be obtained by using the above method are calculated as follows: a total of 1200m³ of supernatant was treated. 3 However, an additional 100m is required for use. 3 Tap water, therefore the benefit is based on saving 1100m³ of water. 3 calculate:

[0062] Acid hydrolysis 800m 3 The clarified solution requires 41.0 tons of 98% concentrated sulfuric acid, which yields 100 tons of 30% concentrated hydrochloric acid, producing 55.9 tons of calcium sulfate (excluding water of crystallization). The yield of dicalcium phosphate increases by 5%, resulting in an additional 6 tons of dicalcium phosphate. Currently, the price of concentrated sulfuric acid is 650 yuan / ton, concentrated hydrochloric acid is 360 yuan / ton, and dicalcium phosphate is 3200 yuan / ton. Calcium sulfate is recycled free of charge. The price of barium chloride is 3200 yuan / ton, and barium sulfate is 2800 yuan / ton; 5.05 tons of barium chloride are needed, yielding 5.66 tons of barium sulfate. The price of barium sulfate is 2800 yuan / ton. The operating cost of dicalcium phosphate production in the calcium phosphate workshop is 500 yuan / ton. By utilizing the clarified solution obtained from the supernatant, 1100 m³ of water is saved daily. 3 Tap water and emission reduction 1100m 3 External wastewater is priced at 2 yuan / ton for tap water. External wastewater costs 1.7 yuan / ton, and environmental treatment costs 1.8 yuan / ton. Daily operating costs are:

[0063] The production cost of hydrochloric acid + barium sulfate + dicalcium phosphate - concentrated sulfuric acid - barium chloride - labor, ultrafiltration, filter press, etc. = 360*100 + 2800*5.66 + 3200*6 + 1100*(2+1.7+1.8) - 41.0*650 - 3200*5.05 - 500*(6+5.66) - 1300*7 = 18193 yuan.

[0064] After the renovation was completed, not only were the external drainage standards improved, but the daily profit also increased by 18,193 yuan.

[0065] The above method was used to reuse dilute hydrochloric acid, and it was found that it had no impact on the quality of bone gelatin products.

[0066] Furthermore, the experiment revealed that the amount of concentrated sulfuric acid added to the clear phase significantly affects the quality of the bone gelatin product. The effects of excessive and moderate amounts of concentrated sulfuric acid on the resulting intermediates, macerated bone extract, and the final product, dilute gelatin solution, were investigated below.

[0067] It should be noted that the amount of concentrated sulfuric acid added should not be excessive, based on 800 mg / L. 3 Clear phase meter, flow rate 22..27m 3 Concentrated sulfuric acid; adding excess concentrated sulfuric acid is based on 800m 3 Clear phase meter, add 25.0 ml of concentrated sulfuric acid. 3 .

[0068] Table 1 shows the results of the investigation of the obtained intermediate, osteocalcin leaching. (Based on 25 tons / tank) Table 1

[0069]

[0070] Table 2 shows the results of the investigation of the obtained intermediate, lycopene.

[0071] Table 2

[0072] Add concentrated sulfuric acid intermediate name same weight volume Appearance Remark However, excessive amounts Soaked bone powder <![CDATA[Small (38.5m 3 )]]> No foreign matter on the surface Odorless excess Soaked bone powder <![CDATA[Large (39.8m 3 )]]> Adhesive calcium sulfate It easily produces an ammonia smell.

[0073] Table 3 shows the results of the examination of the obtained dilute adhesive product.

[0074] Table 3

[0075] Add concentrated sulfuric acid Product Name Electrical conductivity (US / cm) color However, excessive amounts Diluted adhesive 400-700 normal excess Diluted adhesive 1200-1700 Slightly darker

[0076] Increased conductivity of the product's dilute solution leads to a higher load on the ion exchange column, increased regeneration frequency, higher consumption of purified water, and consequently, higher ash content, affecting product quality.

[0077] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A method for treating wastewater in bone gelatin production, characterized in that, Including the following steps: (1) The supernatant after separating the dicalcium phosphate product from the wastewater in the acid leaching process is treated by ultrafiltration membrane to obtain a concentrated phase and a clear phase, respectively; the flux of the ultrafiltration membrane is 5-10 L / (m²). 2 (˙h), aperture 1000 Daltons; (2) Take 60-70% of the clear phase and mix it with concentrated sulfuric acid to react and produce a mixed solution containing hydrochloric acid and calcium sulfate; (3) The mixture is filtered to obtain calcium sulfate solid and hydrochloric acid filtrate, the hydrochloric acid filtrate being used in the acid leaching process; If there is any residue after washing the calcium sulfate solid with the clear phase, the remaining clear phase is used to react with calcium oxide to prepare calcium hydroxide, and the calcium hydroxide is used to extract dicalcium phosphate from the wastewater of the acid leaching process. The supernatant after separating the dicalcium phosphate product from the wastewater in the acid leaching process is first adjusted to pH 4.0-4.2, and then treated with an ultrafiltration membrane. The amount of concentrated sulfuric acid used is determined by the following steps: S1: Calculate the amount of concentrated sulfuric acid to be used based on the calcium ion concentration and chloride ion concentration in the clear phase, respectively: The amount of concentrated sulfuric acid used, M1, is calculated based on the calcium ion concentration using the following formula: M1(m 3 ) = V 步骤(2)清相 ×0.95×Ca 2+ Concentration ÷ 40 ÷ 1.84; Where: 0.95 is the correction constant, Ca 2+ The unit of concentration is tons per 100m³ 3 V 步骤(2)清相 The unit is m 3 ; The amount of concentrated sulfuric acid used, M2, is calculated based on the chloride ion concentration using the following formula: M2(m 3 ) = V 步骤(2)清相 ×(Cl - Concentration -0.25) ÷ 71 ÷ 1.84; Where: 0.25 is the correction constant, Cl - The unit of concentration is tons per 100m³ 3 V 步骤(2)清相 The unit is m 3 ; S2: Add concentrated sulfuric acid based on the smaller of the calculated amounts of M1 and M2.

2. The processing method according to claim 1, characterized in that, The calcium sulfate solid was washed with the residual clear phase to obtain the calcium sulfate product.

3. The processing method according to claim 1, characterized in that, The hydrochloric acid filtrate is purified to obtain a dilute hydrochloric acid product, which is used in the acid leaching process. The purification process includes a first plate and frame filtration, sulfate removal treatment, and a second plate and frame filtration.

4. The processing method according to claim 3, characterized in that, The reagent used for the sulfate removal treatment is barium chloride.

5. The processing method according to claim 4, characterized in that, The sulfate removal treatment includes: (1) After the hydrochloric acid-containing filtrate is filtered once by plate and frame filter, the concentration of sulfate ions is measured and the sulfate ion content is calculated. (2) According to Ba 2+ SO4 2- Barium chloride was weighed in a molar ratio of 1:

1. (3) Add barium chloride to the hydrochloric acid filtrate after the first plate and frame filtration, stir and react, and then send the reaction mixture to the plate and frame filter for a second plate and frame filtration to obtain solid barium sulfate product. The resulting filtrate is dilute hydrochloric acid, which is sent to the acid leaching process for use.

6. The processing method according to claim 1, characterized in that, The concentrated phase obtained from the ultrafiltration process is used as animal feed.

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