阅读说明：本技术 间歇式水热法制备超细珊瑚绒状环保用氢氧化镁的工艺 (Process for preparing superfine coral velvet-shaped environment-friendly magnesium hydroxide by batch hydrothermal method ) 是由 翟俊 傅涛 宗俊 于 2020-12-07 设计创作，主要内容包括：本发明公开了间歇式水热法制备超细珊瑚绒状环保用氢氧化镁的工艺,包括以下步骤：S1、镁矿轻烧；S2、混合浆液；S3、一次水热；S4、二次水热；S5、陈化；S6、抽滤；S7、滤饼干燥；S8、研磨；本方案通过对镁矿进行轻烧、粉碎等一定前处理后再运用间歇式水热法,控制水热温度、水热时间、间歇时间、间歇次数、抽滤时间、烘干温度、烘干时间等过程后,制备出了超细的珊瑚绒状Mg(OH)_2,这种氢氧化镁粒径小,比表面积大,加上其特殊的形貌,在水处理环保方面具有十分重要的应用,另外这种氢氧化镁在使用后经过一定的处理可以作为前驱物,重新用来制备这种或其他形式的镁盐产品,达到循环使用的效果。(The invention discloses a process for preparing superfine coral velvet-shaped environment-friendly magnesium hydroxide by an intermittent hydrothermal method, which comprises the following steps: s1, light burning of magnesium ores; s2, mixing the slurry; s3, primary hydrothermal treatment; s4, secondary hydrothermal; s5, aging; s6, suction filtering; s7, drying a filter cake; s8, grinding; according to the scheme, after magnesium ore is subjected to light burning, crushing and other certain pre-treatments, an intermittent hydrothermal method is applied, and the processes of hydrothermal temperature, hydrothermal time, intermittent times, pumping filtration time, drying temperature, drying time and the like are controlled, so that the superfine coral velvet Mg (OH) is prepared 2 The magnesium hydroxide has small particle size and large specific surface area, and has very important application in the aspect of water treatment environmental protection due to the special appearance, and in addition, the magnesium hydroxide can be used as a precursor after being used and can be reused for preparing magnesium salt products in other forms, so that the effect of recycling is achieved.)

1. The process for preparing the superfine coral velvet-shaped environment-friendly magnesium hydroxide by the batch hydrothermal method is characterized by comprising the following steps of:

s1, light burning of magnesium ore: not all the magnesium oxide can easily react with water to generate magnesium hydroxide, the light-burned magnesium oxide can almost completely react, the medium-burned or heavy-burned magnesium oxide can not completely react, and the magnesium ore is taken as a raw material and is lightly burned for 3-5h at the temperature of 750 ℃ in 550-₂And MgCO₃After the light-burning process, Mg (OH)₂And MgCO₃H in (1)₂O and CO₂Lost to yield MgO;

s2, slurry mixing: taking water as a reaction medium, putting the MgO in the step S1 into a stirrer, fully stirring and hydrating for 5-30min at normal temperature to uniformly obtain MgO slurry, wherein the main function of the step is to promote the fusion of magnesium oxide and water, and simultaneously a small amount of magnesium oxide in the system can be converted into a magnesium hydroxide matrix at normal temperature;

s3, primary hydrothermal: transferring the slurry into a high-pressure reaction kettle, carrying out high-temperature high-pressure reaction for 1.0-2.5h at the hydrothermal temperature of 180 ℃ and 250 ℃, and cooling for 2.5-4.5h after the reaction; at the moment, part of magnesium oxide in the system is converted into magnesium hydroxide;

s4, secondary hydrothermal: then raising the hydrothermal temperature in the high-pressure reaction kettle to 180 ℃ and 220 ℃, and carrying out high-temperature and high-pressure reaction for 3.5-5.5h, so that most of magnesium oxide in the system is converted into magnesium hydroxide;

wherein the principle of step S3-4 is that magnesium ions and H in MgO in the slurry₂The hydroxyl ions in O are subjected to fixed growth reaction at high temperature and high pressure to obtain Mg (OH) with the required shape₂，

The reaction formula is as follows: MgO + H₂O→Mg(OH)₂

S5, aging: after a period of aging, if the aging step is not carried out, the nucleation of the magnesium hydroxide crystal is not facilitated, and the crystal form is extremely incomplete;

s6, suction filtration: then, carrying out suction filtration for 20-50min to obtain a magnesium hydroxide filter cake with higher water content;

s7, drying a filter cake: drying the filter cake in an oven at 80-150 ℃ for 300 min;

s8, grinding: finally grinding to prepare the superfine coral fleece-like Mg (OH) with the medium particle size (D50) of less than 2-5 mu m₂Wherein the smallest D50 is only 0.65-1.05 μm, the specific surface area is as high as 5.50-7.50m2/g, and the crystal structure of the product is stable and contains less impurities.

2. The batch hydrothermal process for preparing superfine coral velvet-like environmentally friendly magnesium hydroxide according to claim 1, wherein in step S1, light burning is performed by using a reverberatory furnace, a suspension furnace, a multi-layer furnace, a rotary kiln or a shaft kiln.

3. The batch hydrothermal process for preparing superfine coral velvet-like environment-friendly magnesium hydroxide as claimed in claim 1, wherein the reaction ratio of the materials in the step S2 is H₂O: MgO is 7.0-15.0.

4. The batch hydrothermal process for preparing superfine coral velvet-like environment-friendly magnesium hydroxide according to claim 1, wherein the aging at normal temperature is performed in step S5 for 1-2 h.

5. The batch hydrothermal process for preparing superfine coral velvet-like environment-friendly magnesium hydroxide according to claim 1, wherein the step S5 is further: steam is used as a drying medium, a magnesium hydroxide filter cake obtained by filtering and washing is firstly subjected to slurry drying at the temperature of 110-130 ℃ to obtain a wet magnesium hydroxide product with the water content of less than 30%, and the wet magnesium hydroxide product enters a rotary flash evaporation micro-powder drying machine to be dried at the temperature of 130-160 ℃ to obtain a product with the water content of less than 0.2%.

Technical Field

The invention relates to the field of magnesium hydroxide preparation processes, in particular to a process for preparing superfine coral velvet-shaped environment-friendly magnesium hydroxide by an intermittent hydrothermal method.

Background

The composite material filled with the composite material can lower the surface temperature in the flame by releasing bound water and absorbing a large amount of latent heat when being heated and decomposed, and has the effects of inhibiting the decomposition of polymers and cooling the generated combustible gas. The magnesium oxide generated by decomposition is a good refractory material, and can also help to improve the fire resistance of the synthetic material, and the water vapor emitted by the magnesium oxide can also be used as a smoke suppressant. Magnesium hydroxide is a well-known excellent flame retardant with triple functions of flame retardance, smoke suppression and filling in the rubber and plastic industry. The product can be widely used in high polymer materials such as rubber, chemical industry, building materials, plastics, electronics, unsaturated polyester, paint, coating and the like.

The sulfur dioxide can be used as a flue gas desulfurizer in the aspect of environmental protection and can replace caustic soda and lime to be used as a neutralizer for acid-containing wastewater. It is also used as oil additive to prevent corrosion and remove sulfur. In addition, the method can also be used for refining granulated sugar, serving as a heat preservation material and manufacturing other magnesium salt products in the electronic industry and the medicine.

In recent years, the national requirements on environmental protection are more and more strict, great funds and energy are invested in the treatment of wastewater, and magnesium hydroxide is also very important as an alkaline substance in the aspect of water treatment.

Disclosure of Invention

The invention aims to provide a process for preparing superfine coral velvet-shaped environment-friendly magnesium hydroxide by an intermittent hydrothermal method, so as to solve the problems in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme:

the process for preparing the superfine coral velvet-shaped environment-friendly magnesium hydroxide by an intermittent hydrothermal method comprises the following steps:

s1, light burning of magnesium ore: not all the magnesium oxide can easily react with water to generate magnesium hydroxide, the light-burned magnesium oxide can almost completely react, the medium-burned or heavy-burned magnesium oxide can not completely react, and the magnesium ore is taken as a raw material and is lightly burned for 3-5h at the temperature of 750 ℃ in 550-₂And MgCO₃After the light-burning process, Mg (OH)₂And MgCO₃H in (1)₂O and CO₂Lost to yield MgO;

s2, slurry mixing: taking water as a reaction medium, putting the MgO in the step S1 into a stirrer, fully stirring and hydrating for 5-30min at normal temperature to uniformly obtain MgO slurry, wherein the main function of the step is to promote the fusion of magnesium oxide and water, and simultaneously a small amount of magnesium oxide in the system can be converted into a magnesium hydroxide matrix at normal temperature;

s3, primary hydrothermal: transferring the slurry into a high-pressure reaction kettle, carrying out high-temperature high-pressure reaction for 1.0-2.5h at the hydrothermal temperature of 180 ℃ and 250 ℃, and cooling for 2.5-4.5h after the reaction; at the moment, part of magnesium oxide in the system is converted into magnesium hydroxide;

s4, secondary hydrothermal: then raising the hydrothermal temperature in the high-pressure reaction kettle to 180 ℃ and 220 ℃, and carrying out high-temperature and high-pressure reaction for 3.5-5.5h, so that most of magnesium oxide in the system is converted into magnesium hydroxide;

wherein the principle of step S3-4 is that magnesium ions and H in MgO in the slurry₂The hydroxyl ions in O are subjected to fixed growth reaction at high temperature and high pressure to obtain Mg (OH) with the required shape₂，

The reaction formula is as follows: MgO + H₂O→Mg(OH)₂

S5, aging: after a period of aging, if the aging step is not carried out, the nucleation of the magnesium hydroxide crystal is not facilitated, and the crystal form is extremely incomplete;

s6, suction filtration: then, carrying out suction filtration for 20-50min to obtain a magnesium hydroxide filter cake with higher water content;

s7, drying a filter cake: drying the filter cake in an oven at 80-150 ℃ for 300 min;

s8, grinding: finally grinding to prepare the superfine coral fleece-like Mg (OH) with the medium particle size (D50) of less than 2-5 mu m₂Wherein the smallest D50 is only 0.65-1.05 μm, the specific surface area is as high as 5.50-7.50m2/g, and the crystal structure of the product is stable and contains less impurities.

Further, in the step S1, the light burning is generally performed by using a reverberatory furnace, a suspension furnace, a multi-layer furnace, a rotary kiln or a shaft kiln.

Further, the material reaction ratio H in the step S2₂O: MgO is 7.0-15.0.

Further, the step S5 adopts normal temperature aging for 1-2 h.

Further, the step S5 may also be: steam is used as a drying medium, a magnesium hydroxide filter cake obtained by filtering and washing is firstly subjected to slurry drying at the temperature of 110-130 ℃ to obtain a wet magnesium hydroxide product with the water content of less than 30%, and the wet magnesium hydroxide product enters a rotary flash evaporation micro-powder drying machine to be dried at the temperature of 130-160 ℃ to obtain a product with the water content of less than 0.2%.

Compared with the prior art, the invention has the beneficial effects that:

according to the scheme, after magnesium ore is subjected to light burning, crushing and other certain pre-treatments, an intermittent hydrothermal method is applied, and the processes of hydrothermal temperature, hydrothermal time, intermittent times, pumping filtration time, drying temperature, drying time and the like are controlled, so that the superfine coral velvet Mg (OH) is prepared₂The magnesium hydroxide has small particle size and large specific surface area, and has very important application in the aspect of water treatment environmental protection due to the special appearance, and in addition, the magnesium hydroxide can be used as a precursor after being used and can be reused for preparing magnesium salt products in other forms, so that the effect of recycling is achieved.

Drawings

FIG. 1 is a schematic flow chart of a process for preparing superfine coral velvet-shaped environment-friendly magnesium hydroxide by a batch hydrothermal method.

FIG. 2 is an SEM photograph of superfine coral velvet-like environmentally friendly magnesium hydroxide prepared by a batch hydrothermal method.

FIG. 3 is another SEM photograph of superfine coral velvet-like environmentally friendly magnesium hydroxide prepared by a batch hydrothermal method.

Detailed Description

The technical solution of the present patent will be described in further detail with reference to the following embodiments.

Referring to fig. 1-3, the process for preparing superfine coral velvet-shaped environment-friendly magnesium hydroxide by a batch hydrothermal method comprises the following steps:

s1, light burning of magnesium ore: not all the magnesium oxide can easily react with water to generate magnesium hydroxide, and the light-burned magnesium oxide can almost completely reactThe magnesium oxide which is burnt in the middle or heavy process can not be completely reacted, and the magnesium ore is used as the raw material and is lightly burnt for 3 to 5 hours at the temperature of 750 ℃ at 550-₂And MgCO₃After the light-burning process, Mg (OH)₂And MgCO₃H in (1)₂O and CO₂Lost to yield MgO;

s2, slurry mixing: taking water as a reaction medium, putting the MgO in the step S1 into a stirrer, fully stirring and hydrating for 5-30min at normal temperature to uniformly obtain MgO slurry, wherein the main function of the step is to promote the fusion of magnesium oxide and water, and simultaneously a small amount of magnesium oxide in the system can be converted into a magnesium hydroxide matrix at normal temperature;

s3, primary hydrothermal: transferring the slurry into a high-pressure reaction kettle, carrying out high-temperature high-pressure reaction for 1.0-2.5h at the hydrothermal temperature of 180 ℃ and 250 ℃, and cooling for 2.5-4.5h after the reaction; at the moment, part of magnesium oxide in the system is converted into magnesium hydroxide;

s4, secondary hydrothermal: then raising the hydrothermal temperature in the high-pressure reaction kettle to 180 ℃ and 220 ℃, and carrying out high-temperature and high-pressure reaction for 3.5-5.5h, so that most of magnesium oxide in the system is converted into magnesium hydroxide;

wherein the principle of step S3-4 is that magnesium ions and H in MgO in the slurry₂The hydroxyl ions in O are subjected to fixed growth reaction at high temperature and high pressure to obtain Mg (OH) with the required shape₂，

The reaction formula is as follows: MgO + H₂O→Mg(OH)₂

In the system OH^-At a constant concentration, Mg²⁺The higher the concentration of [ Mg ]²⁺]·[OH^-]The larger the supersaturation degree is, the more the instantaneous nucleation speed of the magnesium hydroxide is greater than the growth speed of crystal nucleus, the crystal grain of the generated magnesium hydroxide is extremely small, the sedimentation time is prolonged, when the concentration of magnesium ions is lower, the growth of the crystal nucleus is more facilitated, the crystal grain is larger, and the sedimentation is faster; however, if the concentration of magnesium ions is too high, the salt concentration in the system is increased, the double electric layers of colloidal particles are compressed, and the distance between colloidal particles is reduced, so that the agglomeration of colloidal particles is aggravated, the dispersibility of the system is poor, the system is easy to settle, and the hydrogen prepared by the scheme is ultrafine coral velvet-shaped hydrogenMagnesium oxide, which does not require the crystal grain of magnesium hydroxide to be too large, so that supersaturated slurry with high concentration of magnesium ions is used for preparing magnesium hydroxide;

s5, aging: aging for 1-2h at normal temperature after a period of time of aging, wherein if the aging step is not carried out, the nucleation of the magnesium hydroxide crystal is not facilitated, and the crystal form is extremely incomplete;

s6, suction filtration: then, carrying out suction filtration for 20-50min to obtain a magnesium hydroxide filter cake with higher water content;

s7, drying a filter cake: drying the filter cake in an oven at 80-150 ℃ for 300 min;

the step can also be: steam is used as a drying medium, a magnesium hydroxide filter cake obtained by filtering and washing is firstly subjected to slurry drying at the temperature of 110-130 ℃ to obtain a wet magnesium hydroxide product with the water content of less than 30 percent, and the wet magnesium hydroxide product enters a rotary flash evaporation micro-powder drying machine to be dried at the temperature of 130-160 ℃ to obtain a product with the water content of less than 0.2 percent;

s8, grinding: finally grinding to prepare the superfine coral fleece-like Mg (OH) with the medium particle size (D50) of less than 2-5 mu m₂Wherein the smallest D50 is only 0.65-1.05 μm, the specific surface area is as high as 5.50-7.50m2/g, and the crystal structure of the product is stable and contains less impurities.

Although the preferred embodiments of the present patent have been described in detail, the present patent is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present patent within the knowledge of those skilled in the art.