CN102050473A - Process for preparing flame retardant grade magnesium hydroxide by ammonia method - Google Patents
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Abstract
The invention discloses a process for preparing flame retardant grade magnesium hydroxide by an ammonia method. The process comprises the following steps of: adding purified brine of which the Mg<2+> concentration is 40g/L and ammonia water into a reaction kettle and reacting for 60 minutes at 40 DEG C, wherein the ammonia excessive coefficient is 2.5; filtering and washing reaction slurry; and then drying and pulverizing to obtain a fibroid magnesium hydroxide crystal product. Compared with the prior art, through testing and researching, the process determines an optimal technological condition for producing the magnesium hydroxide by an ammonia method, effectively improves the conversion rate of magnesium, improves the filtering property of a filter cake through adding pure magnesium hydroxide as a seed crystal and solves the problem of difficult filtering because the filter cake changes along with the washing pH; the obtained magnesium hydroxide product conforms to the standard of the HG/T3607-2000 I grade of the flame retardant grade magnesium hydroxide, and indicated through TEM (Transverse Electric and Magnetic Field) morphology analysis, the product is fibroid crystal; and the magnesium hydroxide of the fibroid crystal has good dispersity and flowability.
Description
Technical field
The present invention relates to the technology that a kind of ammonia process prepares flame-proof magnesium hydroxide, belong to the preparing technical field of magnesium hydroxide products.
Background technology
Magnesium hydroxide is as Halogen, inorganic additive flame retardant, be in the present inorganic additive flame retardant no matter from comprehensive function or technical and economic evaluation is kind preferably, therefore be subjected to the extensive concern of countries in the world.Making full use of the various magnesium raw materials that contain, quicken the development of magnesium hydroxide, satisfy the domestic and international market demand, is one of important development direction of current magnesia chemical industry.
Titanium is smelted and is mainly produced by magnesium reduction process at present, and principal reaction is as follows:
TiO
2+2Cl
2+C＝TiCl
4+CO
2
TiO
2+2Cl
2+2C＝TiCl
4+2CO
2
TiCl
4+2Mg＝Ti+2MgCl
2
The a large amount of byproduct magnesium chloride of output in the production process, because these byproduct purity are higher, foreign matter content is few, in the deep processing process, can simplify technology, reduce investment, therefore smelting by-product product magnesium chloride being carried out that deep processing makes the higher magnesium salts product of value, improves added value is a kind of effective means to its comprehensive utilization, will very big economic benefit and the social benefit of generation.
The preparation of magnesium hydroxide products is mainly by following two kinds of approach at present: the one, and utilize the natural brucite resource through producing, utilize natural brucite production magnesium hydroxide technology simple, the product purity height, but be subjected to the region restriction big; The 2nd, make by the reaction conversion method by containing magnesium raw material, the purity of its product is decided on material purity and technological process control, is the main production method that present magnesium hydroxide is produced.The reaction conversion method uses by raw material and is divided into two kinds: the one, and with obtaining magnesium oxide behind the roasting of magnesium-containing ore process, digestion, the filtering drying, again magnesium oxide is carried out hydration and prepare magnesium hydroxide; It is big that this method is handled material choice, but need to drop into special preparation of ore, roasting apparatus, the investment cost height, and being suitable for to found the factory is purpose, to produce high-purity magnesium oxide, the additional magnesium hydroxide of producing; The 2nd, in bittern, add alkaline matter and directly be settled out magnesium hydroxide, comprise calcium hydroxide method, sodium hydroxide method and ammonia process.Calcium hydroxide method is with Ca (OH)
2As the neutralization precipitation agent, the advantage of this method is that precipitation agent is easy to get, production technique is simple, but because product granularity little (it is following to reach 0.5um), poly-attached tendency is big, be difficult to sedimentation, filtration and washing and easily adsorb impurity, make product purity low, this method is mainly used in the less demanding magnesium hydroxide preparation of product purity.Sodium hydroxide method be with NaOH as the neutralization precipitation agent, it is higher to obtain product and purity that different grain size distributes in process of production by the adding speed of control sodium hydroxide; But because sodium hydroxide alkalescence is strong, can generate colloidal precipitation as condition control is improper, product cut size is less than normal, brings difficulty for the control of product and filtration.Ammonia process is to be the neutralization precipitation agent with ammoniacal liquor, because a little less than the alkalescence of ammoniacal liquor, thereby crystal grain-growth is easy to control in the reaction process, can make high-purity magnesium hydroxide products, also can generate the megacryst granule product by control neutralization precipitation condition, product is applicable to the industries high to purity requirement such as medicine, chemical reagent and electronic-grade magnesium hydroxide; This method is the method that present domestic production magnesium hydroxide generally adopts, but because
Can make Mg (OH)
2Solubleness increases, and causes this method productive rate lower.
Above-mentioned ammonia process technical process is simple, and controlled variable is easy to grasp.But since anti-molten, the low and filtrate composition complexity of the rate of recovery of magnesium in the ammonia process, ammonia process is bigger to atmospheric pollution simultaneously, also need increase corresponding ammonia still process equipment as reclaiming ammonia, and as not considering the recovery of ammonia, byproduct ammonium chloride price is lower.Therefore ammonia process is applicable to specially and founds the factory, and furthers investigate this technology and can be scale operation in the future and lay the first stone.
Summary of the invention:
The objective of the invention is to: provide a kind of ammonia process to prepare the technology of flame-proof magnesium hydroxide.The present invention by experimental study the influences of ammonia process being produced the magnesium hydroxide rate of recovery and strainability of a plurality of factors, determined comparatively ideal ammonia process manufacturing condition, when effectively improving the magnesium transformation efficiency, solved the problem of filter cake with washing PH variation filtration difficulty.
The present invention is achieved in that the technology that ammonia process prepares flame-proof magnesium hydroxide is: with Mg
2+Concentration is in the purified brine and ammoniacal liquor adding reactor of 40g/L, ammonia excess coefficient 2.5, and reaction is 60 minutes under 40 ℃ of temperature, and reaction slurry filters, washing, and dry then, pulverizing promptly get fibrous magnesium hydroxide crystal product.
For improving the strainability of filter cake, in reaction solution, add the pure cerium hydroxide magnesium of reacting weight 20% as crystal seed.
Described washing process adopts the drip washing of continous vacuum suction filtration.
Used raw brine is from the byproduct magnesium chloride in the titanium smelting process.
The reaction mechanism that ammonia process prepares magnesium hydroxide is as follows:
NH
3-H
2O→NH
4OH
MgCl
2+2NH
4OH→Mg(OH)
2↓+2NH
4Cl
In order to improve magnesium transformation efficiency and the cake filtration performance that ammonia process prepares magnesium hydroxide, obtain meeting the product of flame-proof magnesium hydroxide standard, the contriver explores and studies its preparation process condition by test, and is specific as follows:
One, test raw material and equipment
Table 1 stock chart
| Material name | Composition | |
| Magnesium chloride | In bulk, plate crystal, Mg 96%～99% | |
| Ammoniacal liquor | 2.5L barreled, analytical pure, NH 3?25％ | |
| Sodium hydroxide | 500g is bottled, analytical pure, sheet, 99% | |
| Sodium hydroxide | In bulk, technical pure, sheet, 94%～96% |
Test used key instrument, equipment is as shown in table 2:
Table 2 test apparatus, equipment
| Instrument, device name | Model, specification |
| The electronics Libra | AR1140/C |
| The electronics Libra | PL2002 |
| Electronic speed governing agitator | JJ-1 |
| Adjustable electric cooking stove | 2kw |
| Vacuum pump | 2XZ-2 |
| Baking oven | 20～300℃ |
| Retort furnace | 20～1300℃ |
| Planetary corundum ball mill | SQM-4L |
| 722 type spectrophotometers | 722 |
| The PH meter | PHS-25 |
| Ultrasonic oscillator | Section leads 720011 |
Two, testing program and result
At first carried out single factor experiment to influencing magnesium hydroxide crystalline reaction factor, obtained the basic technology condition with this, as investigating index, Consideration is as follows with Mg transformation efficiency and cake filtration performance in test:
(1) bittern concentration Mg
2+(g/L);
(2) Tc (℃);
(3) crystallization time (min);
(4) ammonia excess coefficient.
Single reaction cumulative volume is controlled to be 500ml.
The cake filtration performance is mainly considered at identical slurry volume (500ml), filtration area (104M
2), the length of filtration time under vacuum tightness (0.03Pa) condition.
1. bittern concentration is to the influence of crystallization reaction
Fixing under the situation of other test conditions the MgCl of preparation different concns
2Solution carries out the reaction of single factor, determining suitable reaction density, and test conditions and the results are shown in Table 3:
Table 3 bittern concentration influences test-results to crystallization reaction
Because ammoniacal liquor will take certain volume, compounding high concentration bittern is restricted, so bittern concentration is up to 60g/L, draws transformation efficiency (%)-C according to the data of table 3
Mg 2+(g/L) graphic representation can find out that transformation efficiency is higher when bittern concentration is 40g/L, (C when low strength range
Mg 2+＜40g/L), increase Mg
2+Concentration can obviously improve transformation efficiency, and change above transformation efficiency behind the 40g/L and slow down, and with Mg
2+Concentration increase solution is glue and is difficult to filter, and transformation efficiency is on a declining curve, thereby selects the bittern concentration of 40g/L to carry out next step test.
2. Tc is to the influence of crystallization reaction
After having determined bittern concentration, carried out the single factor experiment of Tc to crystallization reaction, to determine preferable Tc, test conditions and result such as table 4:
Table 4 Tc influences test-results to crystallization reaction
According to table 4 data draw transformation efficiency (%)-Tc (℃) graphic representation, discovery locates to occur a weight break point at 60 ℃, two crests appear up and down at this point, and the solution on this some the right is glue and is difficult to filter, the crystallization effect that reacts under this temperature is poor, crest to these both sides is investigated: consider from energy consumption of reaction and transformation efficiency, choose 40 ℃ and carry out next step test as preferable temperature of reaction.
3. crystallization time is to the influence of crystallization reaction
Under preferable reaction density and Tc, crystallization time has been carried out single factor experiment, to determine the preferable reaction times, test conditions and result such as table 5:
Table 5 crystallization time influences test-results to crystallization reaction
With the reaction times increase, transformation efficiency improves gradually, at 10～25min time period, solution O H
-Concentration is higher, generates a large amount of Mg (OH)
2, along with OH is carried out in reaction
-Density loss, reaction tends towards stability, and behind 30min, reaction conversion ratio changes little, and after the reaction times surpassed 70min, reacting completely made transformation efficiency improve, and continues reaction and makes the Mg (OH) that generates again
2Anti-molten, cause transformation efficiency to descend, and after surpassing 70min, because the anti-molten Mg (OH) that causes
2Grain refining, solution is deadlocked seriously to be difficult to filter, consider from saving time, improve transformation efficiency and strainability, with 30min as the preferable reaction times.
4. the ammonia excess coefficient is to the influence of crystallization reaction
Find in the process of the test that the Mg transformation efficiency is on the low side, this is because ammoniacal liquor low alkalinity and Mg (OH)
2The higher institute of solubleness extremely in order to improve the Mg transformation efficiency, has carried out the single factor experiment of ammonia excess coefficient and crystallization reaction, test conditions and result such as table 6 in ammonia gonosome system:
Table 6 ammonia excess coefficient influences test-results to crystallization reaction
Can find out by testing data, increase with ammonia volume, the Mg rate of recovery improves gradually, reaction end of a period pH value is increased to 10～11 by 7～8, the Mg transformation efficiency has reached the high value that ammonia process is produced, but the raising of PH has also brought the result of strainability variation simultaneously, in view of single factor experiment is difficult to determine the excessive combined influence with other factors of ammonia, carried out orthogonal test so all influence factors are combined, to determine optimum reaction condition.
5. orthogonal test
The fundamental test condition that has been drawn ammonia process by above-mentioned single factor experiment is:
Mg
2+Concentration: 40g/l
Reaction times: 30min
Temperature of reaction: 40 ℃
Excess coefficient: 1.8
The Mg transformation efficiency is 73% with this understanding, for investigating the combined influence of a plurality of factors to crystallization reaction, has carried out orthogonal test and has determined optimum reaction condition, factor and level such as table 7 that orthogonal test is considered:
Table 7 orthogonal test level of factor table
According to listed factor and level, choose L
9(3)
4Orthogonal table arrangement test, the gauge outfit of test, test-results and interpretation of result are as shown in table 8:
Arrangement of table 8 orthogonal test and test-results
The primary and secondary that is drawn factor by orthogonal experiments is: excess coefficient-temperature-time-concentration, and the ammonia excess coefficient has the greatest impact, and three levels of should getting are 2.5; Temperature factor is also very big to the transformation efficiency influence, gets promptly 40 ℃ of two levels; Reaction times takes second place and gets a horizontal 30min; Mg
2+Concentration is not obvious to the test-results influence, considers to get two horizontal 40g/l in conjunction with the single factor experiment result; Drawing optimum test condition thus is:
Table 9 optimum test condition table
Recheck test is the result show, the Mg transformation efficiency is 79.5%～81.84% with this understanding.
6. magnesium hydroxide washing
Pre-stage test is not considered washing, in order to obtain qualified magnesium hydroxide, needs the magnesium hydroxide that generates is washed a large amount of ammonium chlorides, NH that flush away is wherein contained
3Thereby crystallized product advanced filtration, wash studies, and washing process adopts the drip washing of continous vacuum suction filtration, and scourability is with the transformation efficiency and the Cl of magnesium hydroxide products
-Content is for detecting index.The magnesium hydroxide washing flow as shown in Figure 1.
After the solid-liquid separation, take quantitatively to add the water washing filter cake first in batches, by analysis early stage leacheate to contain Mg, chlorine, ammonia higher, can mix with former reaction filtrate, owing to residual more magnesium and excess of ammonia are arranged in the filtrate, thereby must be recycled, extraction NH wherein
3, ammonium chloride, magnesium chloride.Filtrate can be sent in the ammonia still, the excessive NH that adds when reclaiming reaction
3, solution extracts ammonium chloride by crystallisation by cooling after the ammonia still process, and the surplus solution evaporative crystallization reclaims magnesium chloride.The later stage leacheate can be used as system water supplement or directly opens a way and emits.
In washing process, find, slurry filtration and the early stage washing process in, the strainability of filter cake is fine.But during final wash, the unexpected variation of cake filtration performance consequently can't be washed, trace it to its cause, be because the reaction times not enough, the magnesium hydroxide crystal formation is incomplete, in the suction filtration process wash water wash away and filter cake compression causes crystal fracture, produce a large amount of thin brilliant obstructions due to the filter paper, begin to change when filtrate PH becomes 7～8 through observing, having under the ammoniacal liquor existence condition, because the reaction times deficiency, the magnesium hydroxide crystal growth not exclusively, along with ammonia concn weaken and the external force effect under, crystal grain is broken to produce a large amount of thin brilliant filter paper that stop up.For making the magnesium hydroxide crystal growth fully, on this orthogonal test basis, carried out prolonging the test of reaction times and interpolation crystal seed assisting crystallisation, optimum test condition is made amendment, reaction times is prolonged one times and the pure cerium hydroxide magnesium that adds reacting weight 20%～30% as crystal seed, test-results such as table 10:
Table 10 decomposition of crystal seed test-results
In the crystal seed amount is 10% o'clock, and the slip thickness can't filter, and the slurry filtration scourability was good in 30% o'clock, but transformation efficiency is on the low side, optimum through the seed load of overtesting 20%, further prolongs the reaction times more not obtain better effect.The test conditions that final definite ammonia process is produced magnesium hydroxide is:
Table 11 ammonia process test conditions
Recheck test is the result show, the Mg transformation efficiency is 79.5%～81% with this understanding.
7. product analysis
According to the test conditions of table 11, the gained magnesium hydroxide is analyzed after testing, and except that cl content exceeded standard slightly, all the other indexs all met the I class standard among the HG/T3607-2000.
The magnesium hydroxide analytical results
Calculating ammonia process gained magnesium hydroxide purity by analytical results is 99.23%, and cl content all reaches the I class standard in pre-stage test, so because the bigger analytical error (error of testing oneself is 0.10%～0.05%) of the low existence of cl content.Magnesium hydroxide has been carried out the analysis of TEM (transmission electron microscope) microstructure, analysis revealed: the gained magnesium hydroxide is a fibrous crystallization, average fibre diameter 6.7nm, mean length 200nm, length-to-diameter ratio are 30, the magnesium hydroxide crystallization is generally the laminar crystallization of hexagon, and fibrous crystallization all is better than the hexagon crystallization on crystalline dispersion property and flowability, is a kind of good fire retardant material.
8. ammonia process Economic and Efficiency Analysis
Through overtesting as can be known: 1 ton of magnesium chloride consumes 3.22 ton of 25% ammoniacal liquor, (99%) 0.6 ton of output magnesium hydroxide, and 0.9 ton of ammonium chloride, then the income of 1 ton of magnesium hydroxide of output is as shown in table 12:
Table 12 magnesium hydroxide production cost
Compared with prior art, the present invention has determined the optimum process condition of ammonia process production magnesium hydroxide by experimental study, effectively improved the transformation efficiency of magnesium, and improved the strainability of filter cake as crystal seed, solved filter cake changes filtration difficulty with washing PH problem by adding pure cerium hydroxide magnesium; The products obtained therefrom magnesium hydroxide meets flame-proof magnesium hydroxide HG/T3607-2000I grade standard, and the TEM morphology analysis shows that it is a fibrous crystallization, and this kind crystalline magnesium hydroxide has good dispersiveness and mobile.
Description of drawings:
Fig. 1 is a magnesium hydroxide washing process schema.
Embodiment:
Embodiments of the invention 1: the byproduct magnesium chloride in the titanium smelting process is dissolved in water into Mg
2+Concentration is the solution of 40g/L, add in the reactor together with ammoniacal liquor, ammonia excess coefficient 2.5, and the pure cerium hydroxide magnesium of interpolation reacting weight 20% is as crystal seed, reaction is 60 minutes under 40 ℃ of temperature, and reaction slurry filters, and adopts the drip washing of continous vacuum suction filtration, dry then, pulverizing promptly get fibrous magnesium hydroxide crystal product.Product meets flame-proof magnesium hydroxide HG/T3607-2000 I grade standard through check.
Embodiments of the invention 2: with Mg
2+Concentration is that purified brine and the ammoniacal liquor of 40g/L adds in the reactor, ammonia excess coefficient 2.5, and the pure cerium hydroxide magnesium of interpolation reacting weight 20% is as crystal seed, reaction is 60 minutes under 40 ℃ of temperature, reaction slurry filters, washing, and dry then, pulverizing promptly get fibrous magnesium hydroxide crystal product.Product meets flame-proof magnesium hydroxide HG/T3607-2000 I grade standard through check.
Claims (4)
1. an ammonia process prepares the technology of flame-proof magnesium hydroxide, it is characterized in that: be in the purified brine and ammoniacal liquor adding reactor of 40g/L with Mg2+ concentration, ammonia excess coefficient 2.5, reaction is 60 minutes under 40 ℃ of temperature, reaction slurry filters, washing, dry then, pulverizing promptly get fibrous magnesium hydroxide crystal product.
2. prepare the technology of flame-proof magnesium hydroxide according to the described ammonia process of claim 1, it is characterized in that: in reaction solution, add the pure cerium hydroxide magnesium of reacting weight 20% as crystal seed.
3. prepare the technology of flame-proof magnesium hydroxide according to the described ammonia process of claim 1, it is characterized in that: washing process adopts the drip washing of continous vacuum suction filtration.
4. prepare the technology of flame-proof magnesium hydroxide according to the described ammonia process of claim 1, it is characterized in that: used raw brine is from the byproduct magnesium chloride in the titanium smelting process.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108190924A (en) * | 2018-02-11 | 2018-06-22 | 中南大学 | A kind of preparation method for reducing magnesium hydroxide chlorinity |
| WO2021140856A1 (en) * | 2020-01-08 | 2021-07-15 | 三菱パワー株式会社 | System for producing magnesium hydroxide |
-
2009
- 2009-11-10 CN CN2009103095055A patent/CN102050473A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108190924A (en) * | 2018-02-11 | 2018-06-22 | 中南大学 | A kind of preparation method for reducing magnesium hydroxide chlorinity |
| CN108190924B (en) * | 2018-02-11 | 2019-10-22 | 中南大学 | A kind of preparation method reducing magnesium hydroxide chlorinity |
| WO2021140856A1 (en) * | 2020-01-08 | 2021-07-15 | 三菱パワー株式会社 | System for producing magnesium hydroxide |
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Application publication date: 20110511 |