Production process of synthetic bone meal for bone china

Abstract

The invention relates to the technical field of bone china, and particularly discloses a production process of synthetic bone meal for bone china, which comprises the following steps: S1, mixing calcium hydroxide and water according to a mass ratio of 1: 3 to prepare a calcium hydroxide emulsion; s2, the calcium hydroxide emulsion sequentially passes through four iron removal devices to be subjected to iron removal treatment, and the content of Fe2O3 in a final product is smaller than or equal to 0.12%; s3, hot-process phosphoric acid with the mass fraction of 85% and water are mixed according to the volume ratio of 1: 1, and a phosphoric acid solution is obtained; s4, under the condition of continuous stirring, uniformly adding the phosphoric acid solution into the calcium hydroxide emulsion according to the stoichiometric ratio calculated by complete reaction; by adopting the four-stage series iron removal device and combining online feedback adjustment, metal impurities in raw materials are effectively removed; the dripping speed and the reaction temperature of the phosphoric acid solution are accurately controlled in cooperation with a constant flow pump, and the uniformity and the stability of a reaction system are ensured, so that the chemical purity of the synthesized bone meal is remarkably improved, impurity interference is reduced, and a high-quality product with high whiteness and high light transmittance is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of bone china, and particularly relates to a production process of synthetic bone powder for bone china. Background Technique

[0002] Bone china, as a fine ceramic material mainly made of animal bones or calcium phosphate, etc., and fired at high temperature, has been widely used in the fields of tableware, tea sets and art decorations due to its excellent light transmittance, whiteness and relatively high mechanical strength. In recent years, with the improvement of people's living standards and the change of aesthetic concepts, the quality requirements for bone china have been increasing day by day, especially stricter standards have been put forward for the purity of raw materials and the uniformity of products. In this context, as a key raw material for bone china production, the optimization and innovation of the preparation process of synthetic bone powder are particularly important.

[0003] Traditionally, the preparation of synthetic bone powder mostly uses natural bones as raw materials and obtains it through a series of cumbersome steps such as crushing, degreasing, pickling, and calcination. Although this process meets the basic requirements of bone china production to a certain extent, there are many deficiencies. First of all, the source of raw materials is limited. The supply of animal bones is affected by multiple factors such as region, season and animal epidemics, resulting in unstable raw material supply and large cost fluctuations. Secondly, natural bones often contain relatively high metal impurities such as Fe2O3, and these impurities are difficult to be completely removed during the calcination process, thus affecting the whiteness and light transmittance of the product. Moreover, the degreasing and pickling steps in the traditional process not only have high energy consumption and large pollution, but also are difficult to completely remove the organic residues in the raw materials, resulting in high porosity and reduced strength of the porcelain body. Particularly crucial is that the synthetic bone powder prepared by the traditional process often has large batch differences in composition and performance, and it is difficult to ensure the consistency and stability of the product. Therefore, it needs to be improved by the staff. Summary of the Invention

[0004] The purpose of the present invention is to provide a production process of synthetic bone powder for bone china to solve the problems put forward in the above background technique.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A production process of synthetic bone powder for bone china includes the following steps:

[0007] S1. Mix calcium hydroxide and water according to a mass ratio of 1:3 to make a calcium hydroxide emulsion;

[0008] S2. Pass the calcium hydroxide emulsion through 4 iron removal devices in sequence for iron removal treatment to make the Fe2O3 content in the final product ≤ 0.12%.

[0009] S3. Mix hot-process phosphoric acid with a mass fraction of 85% and water in a volume ratio of 1:1 to obtain a phosphoric acid solution;

[0010] S4. Under continuous stirring, add the phosphoric acid solution uniformly to the calcium hydroxide emulsion according to the stoichiometric ratio calculated for complete reaction, with a reaction time of not less than 2 hours to obtain a white precipitate;

[0011] S5. After the reaction is completed, adjust the pH value of the reaction system to 9 - 10;

[0012] S6. After dehydrating, filtering, and drying the white precipitate, calcine it at a high temperature of 1280 °C - 1300 °C to obtain synthetic bone meal with a CaO content ≥ 55.36% and a P2O5 content ≥ 41.40%.

[0013] Preferably, the calcium hydroxide emulsion is prepared by stirring with a high-speed shear emulsifier, with a stirring speed of not less than 2000 rpm and a stirring time of not less than 30 minutes.

[0014] Preferably, the iron removal device includes a permanent magnet iron remover, an electromagnetic iron remover, a gradient magnetic field separator, and a pipeline type superconducting iron remover, and the four-stage iron removal devices are used in series.

[0015] Preferably, the addition of the phosphoric acid solution is controlled by a constant flow pump, with a dropping speed of 1.5 mL / min·L reaction system, and the reaction temperature is maintained at 60 ± 5 °C.

[0016] Preferably, the dehydration of the white precipitate is carried out using a plate and frame filter press, controlling the moisture content of the filter cake ≤ 25%.

[0017] Preferably, the drying is carried out using a stepped drying process, first drying at 105 °C for 2 hours, and then drying at 80 °C for 4 hours.

[0018] Preferably, the calcination process is carried out in a weakly reducing atmosphere, with the CO concentration controlled at 0.5% - 1%, and the calcination time is 2 hours.

[0019] Preferably, the whiteness of the synthetic bone meal (Hunter whiteness, D65 light source) ≥ 92%, and the particle size D50 = 3.5 ± 0.5 μm.

[0020] Preferably, the addition amount of the synthetic bone meal in the bone china body formula is 40% - 45%.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] (1) By adopting a four-stage series iron removal device (permanent magnet, electromagnetic, gradient magnetic field, superconducting) and combining on-line feedback regulation, the metal impurities in the raw materials are effectively removed; the dropping rate of the phosphoric acid solution and the reaction temperature are precisely controlled with a constant current pump to ensure the uniformity and stability of the reaction system, thereby significantly improving the chemical purity of the synthesized bone powder, reducing impurity interference, and obtaining high-quality products with high whiteness and high light transmittance.

[0023] (2) By introducing a seed induction technology during the reaction process and combining high-temperature calcination under a weak reducing atmosphere, the crystal form transformation path of calcium phosphate is precisely regulated to inhibit the formation of adverse phases; the stepped drying process and the dehydration and pressure filtration technology avoid material caking and ensure the uniformity of the precursor, thereby greatly enhancing the crystal integrity and thermal stability of the synthesized bone powder and endowing it with excellent mechanical strength and sintering activity.

[0024] (3) By adopting an integrated device of a tubular reactor, a pipeline iron removal system and a rotary kiln for calcination, continuous operation of the whole process from raw material mixing to finished product calcination is realized; key parameters (such as viscosity, iron content, pH) are real-time regulated through on-line monitoring technology to reduce manual intervention. Thereby significantly improving production efficiency and product consistency, breaking through the production capacity limit of traditional processes, and meeting the requirements of large-scale industrialization. Description of the Drawings

[0025] Figure 1 is the preparation flow chart of the present invention. Detailed Embodiments

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] Embodiment 1:

[0028] Please refer to Figure 1 shown, a production process of synthetic bone powder for bone china, comprising the following steps:

[0029] S1. Preparation of calcium hydroxide emulsion: Weigh 10 kg of analytical pure calcium hydroxide (Ca(OH)2, purity ≥ 95%) and add 30 kg of deionized water (conductivity ≤ 0.1 μS / cm). Stir with a high-speed shear emulsifier (model XH-2000) at 2200 rpm for 35 minutes, and pass through a 325-mesh stainless steel sieve to remove undispersed particles to obtain a uniform milky white suspension.

[0030] S2. Four-stage iron removal treatment

[0031] Iron removal device configuration:

[0032] First stage: Permanent ferrite magnetic rod (magnetic field strength 2000 Gauss), flow rate control 2 m 3 / h;

[0033] Second stage: Electromagnetic iron remover (5000 Gauss, power 1.2 kW), material residence time 15 seconds;

[0034] Third stage: Gradient magnetic field separator (magnetic field gradient 0.5 T / m), separation frequency set at 5 Hz;

[0035] Fourth stage: Pipeline type superconducting iron remover (cooled to -269 °C with liquid helium), magnetic field strength 8 T.

[0036] Detection result: The content of Fe2O3 after treatment decreased from the initial 0.25% to 0.10%, meeting the requirement of ≤0.12%.

[0037] S3. Preparation of phosphoric acid solution: Take 5 L of 85% thermal phosphoric acid (H3PO4, density 1.689 g / cm 3 ), mix it with 5 L of deionized water in a 40 °C constant temperature water bath, and stir with a magnetic stirrer (600 rpm) until a homogeneous and transparent solution is obtained.

[0038] S4. Neutralization reaction: A 50 L glass-lined reactor, an anchor stirrer (45 rpm), the jacket is connected with circulating water for temperature control. The phosphoric acid solution is slowly added to the calcium hydroxide emulsion through a constant flow pump (flow rate 1.5 mL / min·L), the reaction temperature is maintained at 60 ± 2 °C, and the pH is monitored in real time.

[0039] Endpoint determination: Stop adding acid when the conductivity change rate < 0.5% / min, and the total reaction time is 2 hours and 15 minutes.

[0040] S5. pH adjustment: After the reaction, add ammonia water (concentration 25%) dropwise to adjust the pH to 9.8, and continuously stir for 20 minutes to make the system homogeneous.

[0041] S6. Post-treatment

[0042] Dehydration: Filter press with plate and frame (filter cloth pore size 5 μm) until the water content of the filter cake is 23%;

[0043] Drying: Step-type drying oven (105 °C × 2 h → 80 °C × 4 h), material thickness ≤ 3 cm;

[0044] Calcination: Loaded in an alumina crucible, heated to 1290 °C at a rate of 5 °C / min in a weak reducing atmosphere (CO concentration 0.8%), held for 2 hours, and then cooled to 300 °C with the furnace and taken out.

[0045] Product performance verification:

[0046] Chemical composition: CaO 55.42%, P2O5 41.45%, Fe2O3 0.10%;

[0047] Physical properties: Hunter whiteness 93.2%, D50 particle size 3.4 μm, flexural strength 125 MPa;

[0048] Application test: When making porcelain with an addition amount of 45%, the light transmittance is 39.1% (2 mm), and the glaze glossiness is 96 GU (60° angle).

[0049] Example 2:

[0050] High-purity optimization process

[0051] S1. Raw material pretreatment: Wash industrial-grade Ca(OH)2 three times with 0.1 mol / L EDTA solution to remove trace metal impurities.

[0052] S2. Enhanced iron removal process: On the basis of the four-stage iron removal in Example 1, add an on-line iron ion detector (model FeSense-3000) to adjust the power of the electromagnetic iron remover in real-time feedback. Finally, the Fe2O3 content is reduced to 0.07%, which is better than the standard requirements.

[0053] S3. Reaction kinetics optimization: Adopt a segmented dropping strategy: Drop 70% phosphoric acid solution (1.8 mL / min·L) in the first hour, and drop the remaining 30% (1.2 mL / min·L) in the next hour. The total reaction time is 2 hours. Through on-line XRD monitoring, it is confirmed that amorphous calcium phosphate is formed in the middle stage of the reaction and transformed into crystalline hydroxyapatite in the final stage.

[0054] S4. Calcination crystal form control: Introduce crystal seeds for induction: Add 0.5 wt% β-TCP crystal seeds (particle size 100 nm) before calcination, and adjust the heating program to: The heating rate is 3 °C / min before 800 °C (to promote crystal nucleus formation), and the heating rate is 8 °C / min from 800 to 1300 °C (to promote crystal growth).

[0055] XRD analysis shows that the β-TCP phase content reaches 99.1%, and α-TCP < 0.5%.

[0056] Improvement of application performance:

[0057] The light transmittance of the porcelain body is increased to 41.3% (2 mm), and the glaze glossiness is 98 GU;

[0058] Thermal shock stability test: Quench from 200 °C to 20 °C and cycle 10 times without cracks (better than the requirements of GB / T3298-2008).

[0059] Example 3:

[0060] Continuous industrial production

[0061] S1. Continuous emulsification system: A twin-screw continuous emulsifier (production capacity 500 kg / h) is used, and calcium hydroxide and water are mixed online at a ratio of 1:3, and the viscosity is monitored in real time (control range 1500 ± 200 cP).

[0062] S2. Pipe-type iron removal system: A four-stage series electromagnetic iron removal pipe (diameter 200 mm) is designed, with each stage having a length of 3 m, and the magnetic field intensities are 0.5 T, 1.2 T, 2.0 T, and 3.5 T in sequence, and the total residence time of the material is 120 seconds.

[0063] The on-line iron content analyzer shows that Fe2O3 ≤ 0.09%.

[0064] S3. Continuous neutralization reaction: A tubular reactor (length 15 m, diameter 300 mm) is used, with a built-in static mixing unit.

[0065] Process parameters: Phosphoric acid solution and calcium hydroxide emulsion are continuously fed at a volume ratio of 1:2.67, the reaction temperature is 65 °C, and the residence time is 2.5 hours.

[0066] S4. Spray drying - calcination integration: The dehydrated filter cake is centrifugally spray-dried (inlet temperature 180 °C, outlet temperature 85 °C) to obtain the microsphere precursor; the calcination is carried out in a rotary kiln (length 20 m, inclination angle 2°), and the temperature in the kiln is controlled in zones:

[0067] Preheating zone (800 - 1000 °C): Residence time 30 minutes;

[0068] High-temperature zone (1280 - 1300 °C): Residence time 45 minutes;

[0069] Cooling zone (air-cooled to below 80 °C).

[0070] Large-scale production indicators:

[0071] Daily output: 12 tons of synthetic bone meal;

[0072] Product consistency: The CaO content fluctuates by ±0.15%, and the P2O5 fluctuates by ±0.12%;

[0073] Energy consumption: 38% lower than the batch process (measured power consumption 1.2 kWh / kg).

[0074] Application example:

[0075] Traditional natural bone meal production process

[0076] Raw material treatment: Using animal bones (such as cattle bones) as raw materials, after being crushed, degreased (soaked in organic solvents), and pickled (treated with dilute hydrochloric acid), they are calcined at 900 - 1000 °C for 2 - 3 hours to obtain natural bone meal.

[0077] Component characteristics: The main component is hydroxyapatite (Ca 10 (PO4)6(OH)2), containing organic residues (such as fat, collagen);

[0078] The content of Fe2O3 is relatively high (0.3% - 0.5%), due to the natural iron content in the bone and impurities introduced during the pickling process;

[0079] The whiteness is relatively low (Hunter whiteness 80 - 85%), and the light transmittance is about 30% (2mm thickness).

[0080] Process defects:

[0081] Dependent on animal bone raw materials, with limited sources and large fluctuations in composition;

[0082] Incomplete degreasing leads to high porosity and low strength of the porcelain body (flexural strength ≤ 90MPa);

[0083] The calcination temperature is low, the crystal development is incomplete, and the glossiness of the glaze surface ≤ 85GU.

[0084] Comparative Example 1:

[0085]

[0086] Conclusion: In Example 1, through four - stage iron removal and precise stoichiometric control, the content of Fe2O3 is significantly reduced, the whiteness and mechanical properties are improved, and the raw materials are not restricted by biological sources, which is suitable for industrial production.

[0087] Comparative Example 2:

[0088]

[0089]

[0090] Conclusion: In Example 2, through seed induction and optimization of the calcination atmosphere, the high - purity synthesis of the single crystal form of β - TCP is achieved, and without the pickling step, the thermal stability and optical properties of the product are significantly improved.

[0091] Comparative Example 3:

[0092]

[0093] Conclusion: In Example 3, through continuous equipment and automated control, efficient and low - energy - consumption large - scale production is achieved, and the product consistency far exceeds that of the traditional batch process, meeting the industrialization requirements of high - end bone china.

[0094] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A production process of synthetic bone powder for bone china, characterized in that, It includes the following steps: S1. Mix calcium hydroxide and water at a mass ratio of 1:3 to prepare a calcium hydroxide emulsion. S2. Pass the calcium hydroxide emulsion through 4 iron removal devices in sequence for iron removal treatment, so that the Fe2O3 content in the final product is ≤ 0.12%. S3. Mix hot-process phosphoric acid with a mass fraction of 85% and water at a volume ratio of 1:1 to obtain a phosphoric acid solution. S4. Under continuous stirring, add the phosphoric acid solution evenly to the calcium hydroxide emulsion according to the stoichiometric ratio calculated for complete reaction, and the reaction time is not less than 2 hours to obtain a white precipitate. S5. After the reaction is completed, adjust the pH value of the reaction system to 9 - 10. S6. After dehydrating, filtering, and drying the white precipitate, calcine it at a high temperature of 1280°C - 1300°C to obtain synthetic bone meal with a CaO content ≥ 55.36% and a P2O5 content ≥ 41.40%.

2. The production process of synthetic bone powder for bone china according to claim 1, characterized in that: The preparation of the calcium hydroxide emulsion is stirred by a high-speed shear emulsifier, the stirring speed is not less than 2000 rpm, and the stirring time is not less than 30 minutes.

3. The production process of synthetic bone powder for bone china according to claim 1, characterized in that: The iron removal device includes a permanent magnet iron remover, an electromagnetic iron remover, a gradient magnetic field separator, and a pipeline type superconducting iron remover, and the four-stage iron removal devices are used in series.

4. The production process of synthetic bone powder for bone china according to claim 1, characterized in that: The addition of the phosphoric acid solution is controlled by a constant flow pump, the dropping speed is 1.5 mL / min·L of the reaction system, and the reaction temperature is maintained at 60 ± 5°C.

5. The production process of synthetic bone powder for bone china according to claim 1, characterized in that: The dehydration of the white precipitate is carried out by a plate and frame filter press, and the water content of the filter cake is controlled to be ≤ 25%.

6. The production process of synthetic bone powder for bone china according to claim 1, characterized in that: The drying adopts a stepped drying process, first drying at 105°C for 2 hours, and then drying at 80°C for 4 hours.

7. The production process of synthetic bone powder for bone china according to claim 1, characterized in that: The calcination process is carried out in a weak reducing atmosphere, the CO concentration is controlled at 0.5% - 1%, and the calcination time is 2 hours.

8. The production process of synthetic bone powder for bone china according to claim 1, characterized in that: The whiteness of the synthetic bone meal is ≥ 92%, and the particle size D50 = 3.5 ± 0.5 μm.

9. The production process of synthetic bone powder for bone china according to claim 1, characterized in that: The addition amount of the synthetic bone meal in the bone china body formula is 40% - 45%.

Images