CN101234769B - Technique for preparing high purity ultra-fine magnesium hydroxide by sodium hydroxide method - Google Patents
Technique for preparing high purity ultra-fine magnesium hydroxide by sodium hydroxide method Download PDFInfo
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Abstract
The invention discloses a process for preparing high-purity ultrafine magnesium hydroxide by a sodium hydroxide method; by using a crystal seed decomposition method, purified brine and crystal seed of the magnesium hydroxide are added to a reaction pool to be mixed and temperature is kept at 60-80 DEG C; then solution of the sodium hydroxide is added to the reaction pool to carry out the precipitation reaction, crystallization and aging; after the reaction is finished, slurry of the magnesium hydroxide is filtered and washed; cake after filter is dried and crashed, the crystal product of the magnesium hydroxide is obtained. Compared with the prior art, the process for preparing the high-purity ultrafine magnesium hydroxide accelerates agglomeration and growth of the magnesium hydroxide crystal by adding the crystal seed, solves the problem of the difficulty for filtering and washing the filter cake by using the prior sodium hydroxide method to produce the magnesium hydroxide, and directly utilizes the slurry of the magnesium hydroxide generated by the reaction as the crystal seed to carry out cyclic decomposition. The process flow is simple and the process parameter can be easily controlled. The production process is pro-environment without producing pollutant. At the same time, the purity of the magnesium hydroxide obtained by the process and the recovery rate of the magnesium are very high; furthermore, the purity of the by-product sodium chloride is high. The process for producing the magnesium hydroxide has great development prospect.
Description
Technical field: the present invention relates to a kind of technology of preparing high purity ultra-fine magnesium hydroxide by sodium hydroxide method, 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
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; 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 owing to Mg (OH) in ammonia gonosome system
2Solubleness is big, causes this method productive rate lower.
Though the sodium hydroxide method technical process is simple, controlled variable is difficult for grasping.The applicant learns by further research: adopt decomposition of crystal seed to produce magnesium hydroxide, by crystal seed accelerate magnesium hydroxide crystal agglomeration, grow up, can greatly improve sodium hydroxide method and produce magnesium hydroxide and easily form colloidal precipitation, be difficult to the shortcoming of filtering, washing; If the magnesium hydroxide slip that directly utilizes reaction to generate carries out the crystal seed circulation as crystal seed and decomposes, can more effectively utilize the crystal grain balance in original slurries, quicken the crystal grain distribution equilibrium state of new crystallisation process, with particle dissolving branch laxity, the uneven shortcoming of avoiding adopting dried crystal seed to exist of size-grade distribution
Summary of the invention:
The objective of the invention is to: the technology that a kind of preparing high purity ultra-fine magnesium hydroxide by sodium hydroxide method is provided.The present invention has explored the processing condition that industrial sodium hydroxide decomposition of crystal seed method is produced high purity ultra-fine magnesium hydroxide by experimental study, having studied influences the influence to the magnesium hydroxide rate of recovery and filtration, scourability of a plurality of factors that crystal seed circulation decomposes, determine preferable sodium hydroxide decomposition of crystal seed method manufacturing condition, when guaranteeing high magnesium transformation efficiency, solved the problem that sodium hydroxide method is produced the magnesium hydroxide cake filtration, washed difficulty.
The present invention is achieved in that the technology of preparing high purity ultra-fine magnesium hydroxide by sodium hydroxide method is: adopt the decomposition of crystal seed method, with mixing, keep temperature in purified brine and the solid hydrogen magnesium oxide crystal seed adding reaction tank is 60～80 ℃, again sodium hydroxide solution is added and carry out precipitin reaction in the reaction tank, the crystallization ageing, reaction finishes the back and extracts magnesium hydroxide slurry filtration, washing, filter cake drying, pulverizing promptly get the high purity ultra-fine magnesium hydroxide crystal product.
Preferred technology is: adopt wet crystal seed circulation decomposition method, purified brine is mixed, keeps temperature with preceding secondary response gained magnesium hydroxide slip in reaction tank be 60～80 ℃, again sodium hydroxide solution is added and carry out precipitin reaction in the reaction tank, the crystallization ageing, reaction finishes the back and extracts partly magnesium hydroxide slurry filtration, washing, filter cake drying, pulverizing promptly get the high purity ultra-fine magnesium hydroxide crystal product, and the conduct of residual hydrogen magnesium oxide slip is the crystal seed of secondary response down.
Mg in the above-mentioned bittern
2+Concentration is 20～60g/L, is preferably 40g/L; The crystal seed coefficient is 0.5～2 in the reaction tank, is preferably 1; The base excess coefficient is 1.01～1.05, is preferably 1.03～1.05; Crystallization ageing temperature is 50～90 ℃, is preferably 90 ℃; The crystallization digestion time is 0.5～2 hour, is preferably 1 hour.
Described washing process adopts the gradation washing: liquid-solid ratio L/S=8,40 ℃ of wash temperatures, washing time 10 minutes, or adopt continuous washing; Be preferably and adopt the drip washing of continous vacuum suction filtration.
Used raw brine is byproduct magnesium chloride or the plate crystal magnesium chloride in the titanium smelting process.
Described sodium hydroxide solution is that the concentration of preparing with sheet technical grade sodium hydroxide is the solution of 300～350g/l.
The reaction mechanism that sodium hydroxide method is produced magnesium hydroxide is as follows:
MgCl
2+2NaOH→Mg(OH)
2↓+2NaCl
The present less use of sodium hydroxide method is because the sodium hydroxide price is higher on the one hand, the difficult control of processing parameter on the other hand.But by relatively finding, as adopt industrial sodium hydroxide as raw material, then the relative ammonia process of the cost of sodium hydroxide method is low, and its value and market are much larger than ammonia process byproduct ammonium chloride after purifying for sodium hydroxide method byproduct sodium-chlor, so the applicant furthers investigate the technology that sodium hydroxide method prepares magnesium hydroxide.
Because of sodium hydroxide is alkaline strong, can generate colloidal precipitation as test conditions control is improper, bring difficulty to product filtration, washing.For addressing these problems, the applicant explores and studies the processing condition that sodium hydroxide method prepares magnesium hydroxide by test, and is specific as follows:
One, test raw material and equipment
Test in May, 2006 in Guizhou University's Materials science and metallurgical engineering institute metallurgical test center deployment, main raw material is got the sheet Magnesium Chloride Anhydrous by titanium factory, tests raw materials used as following table:
| Material name | Composition | The place of production |
| Magnesium chloride | In bulk, plate crystal, Mg 96%～99% | Zunyi Titanium Factory |
| Sodium hydroxide | 500g is bottled, analytical pure, sheet, 99% | Chongqing chemical reagent work |
| Sodium hydroxide | In bulk, technical pure, sheet, 94%～96% | Zun Yi alkali factory |
Test used key instrument, equipment is as shown in the table:
| 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) crystal seed coefficient
(3) crystallization time (h);
(4) Tc (℃);
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 1:
Table 1 bittern concentration influences test-results to crystallization reaction
Data according to table 1 can be found out; When bittern concentration from low to high the time, the cake filtration performance is by good variation, and the magnesium hydroxide agglomeration is not serious when lower concentration, and newborn crystal grain is more smooth the carrying out of seed surface secondary nucleation.And with Mg
2+The raising of concentration, the magnesium hydroxide agglomeration of generation is serious, and solution is gel and is difficult to filter.Weigh according to strainability and output, select the bittern concentration of 40g/L to carry out next step test.
2. the crystal seed coefficient is to the influence of crystal property
The test that initial stage carries out shows, under the situation of not adding any additives, the magnesium hydroxide that the sodium hydroxide method crystallization forms is colloidal, is difficult to or at all can't washing and filtering, after adding additives such as flocculation agent, dispersion agent, the phenomenon of coacervation of colloid does not have substantial improvement.So attempted the interpolation crystal seed, by evidence: adopt the method for adding crystal seed can effectivelyly improve the magnesium hydroxide agglomeration, solution can filter, wash.Therefore on the pre-stage test basis, carried out of the test of crystal seed coefficients R to the crystal property influence, because of the sodium hydroxide method level of response more complete, so test only with the filtration time of solution as investigating index, test conditions and test-results are as shown in table 2:
Table 2 crystal seed coefficients R influences test-results to crystal property
Because the strong precipitin reaction of sodium hydroxide alkalescence is rapid, magnesium hydroxide crystallites a large amount of in short period of time generate, when not adding crystal seed, newly-generated trickle grain growing is that the process of large size crystal grain is extremely slow, these trickle crystal grain are reunited with being suspended in and are made solution be gluey in the solution, adding flocculation agent only is the agglomeration of facilitating crystal grain by opposite electrical charges attract, does not form large size crystal grain in fact.Can find out by testing data, increasing strainability with the crystal seed amount improves, the newly-generated magnesium hydroxide that is incorporated as of crystal seed provides nucleus, promoted carry out of newborn crystal grain at the seed surface secondary nucleation, shortened the time of crystal growth, while motion of a large amount of crystal seeds under stirring action is flushed in and has hindered the colloidal reunion to a certain extent, has played the dispersive effect.Take all factors into consideration the influence of crystal seed consumption and reaction volume, choose the crystal seed coefficient of R=1 as the later stage test.
3. crystallization time is to the influence of crystal property
Add crystal seed and can improve magnesium hydroxide colloidal crystal property greatly, add crystal seed post crystallization performance over time for investigating, carried out the single factor experiment of crystallization time to the crystal property influence, seek suitable crystallization time value, test-results is as shown in table 3:
Table 3 crystallization time influences test-results to crystal property
Test-results shows: crystallization time length is not remarkable to the crystal property influence, and strainability prolongs in time and changes not quite, and choosing crystallization time is 1h.
4. Tc influences crystal property
Add crystal seed post crystallization performance with variation of temperature for investigating, carried out the single factor experiment of Tc to the crystal property influence, seek suitable Tc, test-results is as shown in table 4:
Table 4 Tc influences test-results to crystal property
Raising along with temperature, magnesium hydroxide crystalline filtration washing improves, and comparatively high temps has promoted crystalline growth velocity, and the generation of large size crystal grain has improved the crystalline strainability, this mechanism with the magnesium hydroxide hydrothermal modification is consistent, thereby chooses 90 ℃ for Tc.
5. orthogonal test
Roughly determined the basic technology condition such as the table 5 of sodium hydroxide method by above-mentioned single factor experiment:
Table 5 fundamental test condition:
| Factor | The crystal seed coefficients R | Crystallization time h | Tc ℃ | C Mg 2+ g/l |
| Value | 1 | 1 | 90 | 40.0 |
Magnesium transformation efficiency＞98% with this understanding, filtration time＜24min.
For obtaining preferable test conditions, comprehensive single factor experiment result has carried out orthogonal test, and a nearly step is investigated optimum test condition, factor and level such as table 6 that orthogonal test is considered:
Table 6 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 7:
Arrangement of table 7 orthogonal test and orthogonal experiments
The primary and secondary that is drawn factor by orthogonal experiments is: temperature-concentration-time-R, and having the greatest impact of Tc should be got promptly 90 ℃ of three levels, and the concentration factor affecting is also very big, and two levels of getting are Mg
2+=40g/l, reaction times and crystal seed coefficient are little to the influence of crystal property, get two levels respectively in conjunction with the single factor experiment result, draw best decomposition of crystal seed condition thus to be:
Table 8 decomposition of crystal seed condition
| Factor | The crystal seed coefficients R | Crystallization time h | Tc ℃ | C Mg 2+ g/l |
| Value | 1 | 1 | 90 | 40.0 |
6. base excess coefficient test
Pre-stage test shows that sodium hydroxide and magnesium chloride are more complete, magnesium average conversion＞97%, but for the purity that reclaims the chlorine in the washing lotion as far as possible and improve sodium-chlor, the excessive degree of sodium hydroxide has been carried out experimental study to the influence of crystal property, all the other test conditionss are undertaken by top condition except that the sodium hydroxide addition is variable, and test conditions and result are as shown in table 9:
Table 9 base excess coefficient influences test-results to crystal property
| Sequence number | The base excess coefficient | Mg g/l in the filtrate | Mg transformation efficiency % |
| 1 | 1.01 | 1.22 | 97.90 |
| 2 | 1.05 | 0.45 | 99.29 |
| 3 | 1.10 | - | ＞99％ |
As seen from the experiment: the magnesium transformation efficiency is about 97% when adding sodium hydroxide by theoretical amount, and difference is little when adding alkali number and improve 1%, the higher purity that is unfavorable for sodium-chlor of Mg content in the filtrate; Add alkali number and bring up to 5% back magnesium transformation efficiency＞99%, the Mg concentration in the solution can be reduced to 0.15g/l～0.55g/l; Bring up in 10% rear filtrate magnesium and can't measure when adding alkali number, but this moment become thickness and strainability variation of reaction solution, show that by further fine setting test the base excess coefficient is the most suitable 1.03～1.05.
7. filter cake washing research
Because of magnesium hydroxide granularity with respect to the NH method that sodium hydroxide method is produced wants thin, so the washing filter cakes performance is poor than the NH method, in order to make the product purity conformance with standard and to reclaim Cl as far as possible
-, a washing filter cakes has been carried out technical study, investigated the effect of gradation washing and continuous washing respectively.
The influence to scourability of wash temperature, washing time, liquid-solid ratio has been investigated in gradation washing, investigates the scourability quality by filtration time and detersive efficiency.A filter cake is sized mixing with distilled water, and the control water yield is adjusted liquid-solid ratio, agitator treating at a certain temperature, and the certain hour after-filtration is analyzed Cl in the filtrate
-Cubage detersive efficiency η
Wash
Table 10 washing orthogonal test level of factor table
For guaranteeing the filter cake homogeneity, adopted the filter cake average sample of 2L decomposition of crystal seed to carry out washing test, the filter cake composition is as shown in table 11.
Table 11 filter cake composition
| Water ratio (%) | Mg 2+(％) | Cl -(％) |
| 56.7 | 11.97 | 16.24 |
Choose L
9(3)
4Orthogonal table arrangement test, the gauge outfit of test, test-results and interpretation of result are as shown in table 12:
Arrangement of table 12 orthogonal test and test-results
The primary and secondary that is drawn factor by orthogonal experiments is: liquid-solid ratio-time-temperature, liquid-solid ratio has the greatest impact, and gets two horizontal L/S=8, and temperature is got promptly 40 ℃ of levels, and it is 10min that washing time is got a level, draws best single wash condition thus to be:
Table 13 single wash test conditions
| Factor | Liquid-solid ratio L/S | Washing time min | Wash temperature ℃ |
| Value | 8 | 10 | 40 |
The recheck test result shows Cl
-Detersive efficiency η
Wash=93.09%, through Cl%=4.15% in the filter cake after the washing.The gradation wash result shows: the efficient of washing is better, but technology is too loaded down with trivial details, and filtrate volume is bigger, thereby considers to adopt continuous washing technology that filter cake is washed.
The continuous washing process using is adding distil water (40 ℃) drip washing filter cake in batches, and table 14 is analytical resultss of gained magnesium hydroxide after the filter cake drip washing:
Table 14 continuous washing test-results
By filtrate is in batches analyzed discovery, Cl in the preceding filtrate several times
-Content higher (11～7g/l), but make batching or moisturizing usefulness, Cl in the later stage leacheate in the retrieval system
-Content lower (1～0.025g/l), can be considered as moisturizing retrieval system or directly discharging.
For observing the pattern and the crystallographic dimension of magnesium hydroxide crystal, prepared magnesium hydroxide has been carried out the analysis of TEM (transmission electron microscope) microstructure, the tem analysis result shows that prepared magnesium hydroxide is laminar hexagonal, the small amount of fibers of wherein mixing shape crystal, the atom diffraction figure of single crystal and TEM monocrystalline microgram show the magnesium hydroxide well-crystallized.
The TEM photo is carried out measuring result to be shown: prepared magnesium hydroxide crystal is laminar hexagonal, crystal particle diameter 250nm～310nm, and crystal thickness 10nm belongs to the submicron-grade superfine magnesium hydroxide.Find simultaneously in single decomposition of crystal seed process since to add the crystal seed microscopic dimensions big, cause crystallization that agglomeration is not exclusively arranged.
8. circulation crystal seed method technical study
Pre-stage test is the dried crystal seed of independent interpolation, dried decomposition of crystal seed is that finished product solid hydrogen magnesium oxide is joined in the reaction tank as crystal seed, find the fine grinding degree of dried crystal seed in the test and in solution the dissolving degree of scatter bigger to the crystallization reaction influence, big or dissolving jitter time deficiency can cause crystal property relatively poor as a crystal seed material.The magnesium hydroxide slurry of having taked the retained part reaction to finish in the later stage test, with the magnesium hydroxide that exists in the solution directly carries out next step production as crystal seed technology, promptly wet crystal seed circulation is decomposed.
Major advantage through the wet crystal seed circulation decomposition method of evidence is: with magnesium hydroxide slurry as crystal seed, the guarantor has treated the crystal grain equilibrium state in original slurries, can effectively utilize the crystal grain balance in original slurries, quicken the crystal grain distribution equilibrium state of new crystallisation process, shortened the grain growth time, dried crystal seed dissolving branch laxity, the uneven shortcoming of size-grade distribution have been overcome, save the dissolving dispersion process of dried crystal seed, size mixing technology is simple relatively, has reduced the crystal seed returning charge process in the dried crystal seed flow process.
The master operation of wet crystal seed circulation decomposition method is:
(1) with magnesium chloride and water or later stage washing lotion mixing preparation bittern;
(2) bittern being sent into reactive tank mixes with reservation magnesium hydroxide seed slurry;
(3) in reactive tank, add sodium hydroxide solution and carry out crystallization and ageing;
(4) extract the part magnesium hydroxide slurry after crystallization finishes and filter, wash the preparation magnesium hydroxide, the conduct of residue slurries is the crystal seed of crystallization reaction next time.
Carried out wet crystal seed round-robin test on the basis of single test, test conditions is as shown in Table 15:
Table 15 sodium hydroxide method test conditions
| Factor | The crystal seed coefficients R | Crystallization time h | Tc ℃ | C Mg 2+ g/l |
| Value | 1 | 1 | 90 | 40.0 |
The test initial stage adds dried crystal seed 48.5g (Mg
2+=27.6%, sodium-chlor=37.5%), adds magnesium chloride solution (Mg as starting usefulness at every turn
2+=65.07g/l) 300ml, sodium hydroxide solution (analytical pure, 330g/l) 200ml, reaction cumulative volume 1L gets 500ml slurry preparation magnesium hydroxide after the single reaction finishes, and the residue slurries are as secondary response crystal seed down.Table 16 provides 10 times test-results of circulation:
The table 16 crystal seed circulation decomposition run result that wets
10 actual magnesium output capacities of round-robin test are 95.31%, output capacity is on the low side mainly be because the crystal seed that begins to add be not pure cerium hydroxide magnesium, average sample is inhomogeneous and the filter cake operational losses, causes the magnesium rate of recovery on the low side.
9. industrial sodium hydroxide circulation crystal seed method technical study
Pre-stage test adopts be analytical pure sodium hydroxide as raw material, in order to save cost thereby to consider to substitute with industrial sodium hydroxide and test, test conditions is pressed the pre-stage test condition, startup crystal seed 56.75g (Mg
2+=35.77%, sodium-chlor=16.65%), magnesium chloride 78.5g is dissolved in 300ml water at every turn, sodium hydroxide solution (technical grade NaOH=94%～96%, 346.5g/l) 200ml, reaction cumulative volume 1L, get 500ml slurry preparation magnesium hydroxide after the single reaction finishes, the conduct of residue slurries is the secondary response crystal seed down.The stoste of dope filtration is in order to preparation sodium-chlor, and filter cake is with distilled water continuously drip washing in batches, each wash water 200ml, and preceding twice wash water (washing lotion) returns batching, and table 17 provides the test-results of circulation 6 times:
The table 17 industrial sodium hydroxide crystal seed circulation decomposition run result that wets
The base excess coefficient is controlled at 1.03～1.05 in the process of the test, single Mg transformation efficiency is all more than 99%, because a washing lotion is back to batching, thereby in circulation a Cl content of washing than the height of pre-stage test, the 7th round-robin the finished product are delivered to Guizhou Normal University analyzing and testing center analyze, the result is shown in table 18:
Table 187# magnesium hydroxide analytical results
| Project | MgO ％ | CaO ％ | Cl ％ | Fe ％ | Acid non-soluble substance % | Loss on ignition % |
| Analytical value | 68.9 | 0.097 | 0.20 | 0.005 | 0.016 | 30.6 |
| The I class standard | ≥63.0 | ≤1.00 | ≤0.15 | ≤0.25 | ≤0.20 | ≥28.0 |
The Cl average content is 0.097% in 6 recycle hydrogen magnesium oxide, Mg average content＞41.3%, Mg (OH)
2Average purity＞99% meets and exceeds the I class standard among the HG/T3607-2000.
For the crystal formation of observing magnesium hydroxide in the working cycle changes, 1#, 4#, 6# sample have been carried out TEM (transmission electron microscope) analysis of micro-morphology, by the tem analysis result as can be known, circulation back gained magnesium hydroxide is identical with pre-stage test for the first time, has crystal agglomeration and crystal particle diameter big; Increase with cycle index, weaken to the 4th circulation back agglomeration, the reunion crystal begins to disperse, and crystal particle diameter reduces; Almost disappear to the 6th circulation back reunion, crystalline dispersion degree is big, and crystal particle diameter tends towards stability; The 7th round-robin magnesium hydroxide TEM photo and the 6th round-robin magnesium hydroxide TEM are basic identical, and this explanation increases with cycle index, and the magnesium hydroxide particle diameter in the slurries tends to balance, and has reached a steady state; Through measuring: the magnesium hydroxide by the industrial sodium hydroxide preparation is the laminar hexagonal of dispersed, crystal particle diameter 50nm～83nm, and crystal thickness 7nm belongs to the nano level superfine magnesium hydroxide.
To the stoste in the circulation, one washing lotion and leacheate are analyzed, the chlorine ratio that has drawn each several part washing lotion in the circulation is: stoste 60%～64%, one washing lotion 25%～29%, leacheate 2%～7%, one washing lotion is returned in the circulation as system water supplement, leacheate PH=7～8, show that by analysis harmful element is atomic, can reach the GB8978-1996 state sewage emission standard, can directly discharge or do the moisturizing retrieval system, stoste is extracted sodium-chlor after evaporating, 6 round-robin stostes are mixed the back evaporation and are prepared into sodium-chlor 353.24g, the chlorine output capacity is 61.08%, sample presentation analysis revealed sodium-chlor purity is 99.6%, substantially reach chemical pure sodium-chlor standard, after further purifying, can reach the top grade pure sodium chloride.
10. sodium hydroxide circulation crystal seed method process economics performance analysis
Adopt the wet decomposition of crystal seed explained hereafter magnesium hydroxide of industrial sodium hydroxide, 1 ton of magnesium chloride consumes 0.8654 ton of industrial NaOH (excessive 1.03), 0.6 ton of output super fine magnesium hydroxide (nano-grade, 99%), 0.75 ton in sodium-chlor (chemical pure 99.6%), then the income of 1 ton of magnesium hydroxide of output is shown in table 19:
Table 19 magnesium hydroxide production cost
Be the top grade pure sodium chloride as sodium-chlor is further purified, price can rise to more than 2800 yuan/ton.
Compared with prior art, major advantage of the present invention is:
1. accelerate the agglomeration of magnesium hydroxide crystal, grow up by adding crystal seed, greatly improved original sodium hydroxide method and produced magnesium hydroxide and easily form colloidal precipitation, precipitation is difficult to the shortcoming of filtering, washing.And directly utilize magnesium hydroxide slip that reaction generates as the crystal seed decomposition that circulates, can more effectively utilize the crystal grain balance in original slurries, quicken the crystal grain distribution equilibrium state of new crystallisation process, overcome the particle dissolving branch laxity, the uneven shortcoming of size-grade distribution that adopt dried crystal seed to exist.
2. washing process adopts the drip washing of multiple batches of continous vacuum suction filtration, and each batch washing lotion is respectively applied for: be rich in a large amount of sodium-chlor in the slip stoste, be used for vaporize draw chemical pure sodium-chlor; Contain a certain amount of Mg in one washing lotion
2+, be used for batching or system water supplement in the Returning process; Last leacheate shows that by analysis harmful element is atomic, can reach the GB8978-1996 state sewage emission standard, can directly discharge or do the moisturizing retrieval system.
3. prepared magnesium hydroxide products purity 〉=99% is better than the HG/T3607-2000I grade standard, and the analysis of TEM microstructure is the laminar hexagonal of dispersed, crystal particle diameter 50nm～83nm, and crystal thickness 7nm belongs to high purity ultra-fine magnesium hydroxide.Stoste is 99.6% through the sodium-chlor purity of vaporize draw, reaches chemical pure sodium-chlor standard substantially, can reach the top grade pure sodium chloride after further purifying.
4. technical process is simple, processing parameter is controlled easily, and the magnesium hydroxide purity and the magnesium rate of recovery (single production is 99%, cyclic production 〉=94%) of this technology acquisition are all high simultaneously, and the purity height can be supplied alkali factory as raw material to byproduct sodium-chlor because raw material impurity content is low.Production process environmental protection, unharmful substance produce, and technical process is suitable for small-sized founding the factory, and can be used for handling the non-quantitative magnesium chloride byproduct of titanium factory or other approach.
Description of drawings:
Fig. 1 produces the process flow sheet of magnesium hydroxide for wet crystal seed circulation decomposition method.
Fig. 2 produces the process flow sheet of magnesium hydroxide for doing the decomposition of crystal seed method.
Embodiment:
Embodiment 1:
The technology that sodium hydroxide is done decomposition of crystal seed method production high purity ultra-fine magnesium hydroxide is: with Mg
2+Concentration is that purified brine and the solid hydrogen magnesium oxide crystal seed of 20g/L adds in the reaction tank and mix, keep certain temperature (60～80 ℃), crystal seed coefficient 1.0, again sodium hydroxide solution (350g/l) is added in the reaction tank and carry out precipitin reaction, base excess coefficient 1.05, the crystallization ageing is 90 minutes under 70 ℃ of temperature, reaction finishes the back and extracts magnesium hydroxide slurry filtration, gradation washing (liquid-solid ratio L/S=8,40 ℃ of wash temperatures, washing time 10 minutes), and filtering slip stoste is used for vaporize draw chemical pure sodium-chlor; Be used for batching or system water supplement in the washing lotion Returning process.Filter cake drying, pulverizing promptly get the high purity ultra-fine magnesium hydroxide crystal product.(the magnesium rate of recovery is 99%).
Embodiment 2:
The technology that the wet crystal seed circulation decomposition method of sodium hydroxide is produced high purity ultra-fine magnesium hydroxide is: with Mg
2+Concentration is that the purified brine of 30g/L mixes, keeps certain temperature (60～80 ℃) with preceding secondary response gained magnesium hydroxide slip in reaction tank, crystal seed coefficient 0.5, again sodium hydroxide solution (300g/l) is added in the reaction tank and carry out precipitin reaction, base excess coefficient 1.01, the crystallization ageing is 120 minutes under 55 ℃ of temperature, reaction finishes the back and extracts partly magnesium hydroxide slurry filtration, continuous washing, and filtering slip stoste is used for vaporize draw chemical pure sodium-chlor; Be used for batching or system water supplement in the one washing lotion Returning process; Last leacheate can directly discharge or do the moisturizing retrieval system.Filter cake drying, pulverizing promptly get the high purity ultra-fine magnesium hydroxide crystal product.The conduct of residual hydrogen magnesium oxide slip is the crystal seed of secondary response down.(production of magnesium rate of recovery single is 99%, cyclic production 〉=94%).
Embodiment 3:
The technology that the wet crystal seed circulation decomposition method of sodium hydroxide is produced high purity ultra-fine magnesium hydroxide is: with Mg
2+Concentration is that the purified brine of 25g/L mixes, keeps certain temperature (60～80 ℃) with preceding secondary response gained magnesium hydroxide slip in reaction tank, crystal seed coefficient 1.5, again sodium hydroxide solution (320g/l) is added in the reaction tank and carry out precipitin reaction, base excess coefficient 1.03, the crystallization ageing is 30 minutes under 90 ℃ of temperature, reaction finishes the back and extracts partly magnesium hydroxide slurry filtration, the drip washing of continous vacuum suction filtration, and filtering slip stoste is used for vaporize draw chemical pure sodium-chlor; Be used for batching or system water supplement in the one washing lotion Returning process; Last leacheate can directly discharge or do the moisturizing retrieval system.Filter cake drying, pulverizing promptly get the high purity ultra-fine magnesium hydroxide crystal product.The conduct of residual hydrogen magnesium oxide slip is the crystal seed of secondary response down.(production of magnesium rate of recovery single is 99%, cyclic production 〉=94%).
Embodiment 4:
The technology that the wet crystal seed circulation decomposition method of sodium hydroxide is produced high purity ultra-fine magnesium hydroxide is: with Mg
2+Concentration is that the purified brine of 40g/L mixes, keeps certain temperature (60～80 ℃) with preceding secondary response gained magnesium hydroxide slip in reaction tank, crystal seed coefficient 1.1, again sodium hydroxide solution (340g/l) is added in the reaction tank and carry out precipitin reaction, base excess coefficient 1.02, the crystallization ageing is 75 minutes under 90 ℃ of temperature, reaction finishes the back and extracts partly magnesium hydroxide slurry filtration, the drip washing of continous vacuum suction filtration, and filtering slip stoste is used for vaporize draw chemical pure sodium-chlor; Be used for batching or system water supplement in the one washing lotion Returning process; Last leacheate can directly discharge or do the moisturizing retrieval system.Filter cake drying, pulverizing promptly get the high purity ultra-fine magnesium hydroxide crystal product.The conduct of residual hydrogen magnesium oxide slip is the crystal seed of secondary response down.(production of magnesium rate of recovery single is 99%, cyclic production 〉=94%).
Embodiment 5:
The technology that the wet crystal seed circulation decomposition method of sodium hydroxide is produced high purity ultra-fine magnesium hydroxide is: with Mg
2+Concentration is that the purified brine of 40g/L mixes, keeps certain temperature (60～80 ℃) with preceding secondary response gained magnesium hydroxide slip in reaction tank, crystal seed coefficient 1.0, again sodium hydroxide solution (310g/l) is added in the reaction tank and carry out precipitin reaction, base excess coefficient 1.04, the crystallization ageing is 60 minutes under 80 ℃ of temperature, reaction finishes the back and extracts partly magnesium hydroxide slurry filtration, the drip washing of continous vacuum suction filtration, and filtering slip stoste is used for vaporize draw chemical pure sodium-chlor; Be used for batching or system water supplement in the one washing lotion Returning process; Last leacheate can directly discharge or do the moisturizing retrieval system.Filter cake drying, pulverizing promptly get the high purity ultra-fine magnesium hydroxide crystal product.The conduct of residual hydrogen magnesium oxide slip is the crystal seed of secondary response down.(production of magnesium rate of recovery single is 99%, cyclic production 〉=94%).
Embodiment 6:
The technology that the wet crystal seed circulation decomposition method of sodium hydroxide is produced high purity ultra-fine magnesium hydroxide is: with Mg
2+Concentration is that the purified brine of 50g/L mixes, keeps certain temperature (60～80 ℃) with preceding secondary response gained magnesium hydroxide slip in reaction tank, crystal seed coefficient 2.0, again sodium hydroxide solution (330g/l) is added in the reaction tank and carry out precipitin reaction, base excess coefficient 1.03, the crystallization ageing is 45 minutes under 85 ℃ of temperature, reaction finishes the back and extracts partly magnesium hydroxide slurry filtration, the drip washing of continous vacuum suction filtration, and filtering slip stoste is used for vaporize draw chemical pure sodium-chlor; Be used for batching or system water supplement in the one washing lotion Returning process; Last leacheate can directly discharge or do the moisturizing retrieval system.Filter cake drying, pulverizing promptly get the high purity ultra-fine magnesium hydroxide crystal product.The conduct of residual hydrogen magnesium oxide slip is the crystal seed of secondary response down.(production of magnesium rate of recovery single is 99%, cyclic production 〉=94%).
Embodiment 7:
The technology that the wet crystal seed circulation decomposition method of sodium hydroxide is produced high purity ultra-fine magnesium hydroxide is: with Mg
2+Concentration is that the purified brine of 60g/L mixes, keeps certain temperature (60～80 ℃) with preceding secondary response gained magnesium hydroxide slip in reaction tank, crystal seed coefficient 1.5, to add in the reaction tank near saturated sodium hydroxide solution again and carry out precipitin reaction, base excess coefficient 1.04, the crystallization ageing is 90 minutes under 50 ℃ of temperature, reaction finishes the back and extracts partly magnesium hydroxide slurry filtration, gradation washing (liquid-solid ratio L/S=8,40 ℃ of wash temperatures, washing time 10 minutes), and filtering slip stoste is used for vaporize draw chemical pure sodium-chlor; Be used for batching or system water supplement in the washing lotion Returning process.Filter cake drying, pulverizing promptly get the high purity ultra-fine magnesium hydroxide crystal product.The conduct of residual hydrogen magnesium oxide slip is the crystal seed of secondary response down.(production of magnesium rate of recovery single is 99%, cyclic production 〉=94%).
Claims (8)
1. the technology of a preparing high purity ultra-fine magnesium hydroxide by sodium hydroxide method is characterized in that: adopt the decomposition of crystal seed method, with Mg
2+Concentration is that purified brine and the solid hydrogen magnesium oxide crystal seed of 20～60g/L adds in the reaction tank and mix, the crystal seed coefficient is 0.5～2 in the reaction tank, keeping temperature is 60～80 ℃, again sodium hydroxide solution is added and carry out precipitin reaction in the reaction tank, 50～90 ℃ of crystallization ageings 0.5～2 hour, reaction finishes the back and extracts magnesium hydroxide slurry filtration, washing, and filter cake drying, pulverizing promptly get the high purity ultra-fine magnesium hydroxide crystal product.
2. according to the technology of the described preparing high purity ultra-fine magnesium hydroxide by sodium hydroxide method of claim 1, it is characterized in that: adopt wet crystal seed circulation decomposition method, Mg
2+Concentration is that the purified brine of 20～60g/L mixes in reaction tank with preceding secondary response gained magnesium hydroxide slip, the crystal seed coefficient is 0.5～2 in the reaction tank, keeping temperature is 60～80 ℃, again sodium hydroxide solution is added and carry out precipitin reaction in the reaction tank, 50～90 ℃ of crystallization ageings 0.5～2 hour, reaction finishes the back and extracts partly magnesium hydroxide slurry filtration, washing, filter cake drying, pulverizing, promptly get the high purity ultra-fine magnesium hydroxide crystal product, the conduct of residual hydrogen magnesium oxide slip is the crystal seed of secondary response down.
3. according to the technology of claim 1 or 2 described preparing high purity ultra-fine magnesium hydroxide by sodium hydroxide method, it is characterized in that: the base excess coefficient is 1.01～1.05.
4. according to the technology of the described preparing high purity ultra-fine magnesium hydroxide by sodium hydroxide method of claim 3, it is characterized in that: Mg in the bittern
2+Concentration is 40g/L; The crystal seed coefficient is 1 in the reaction tank; The base excess coefficient is 1.03～1.05; Crystallization ageing temperature is 90 ℃; The crystallization digestion time is 1 hour.
5. according to the technology of claim 1 or 2 described preparing high purity ultra-fine magnesium hydroxide by sodium hydroxide method, it is characterized in that: described washing process adopts the gradation washing: liquid-solid ratio L/S=8,40 ℃ of wash temperatures, washing time 10 minutes, or adopt continuous washing.
6. according to the technology of the described preparing high purity ultra-fine magnesium hydroxide by sodium hydroxide method of claim 5, it is characterized in that: washing process adopts the drip washing of continous vacuum suction filtration.
7. according to the technology of claim 1 or 2 described preparing high purity ultra-fine magnesium hydroxide by sodium hydroxide method, it is characterized in that: used raw brine is byproduct magnesium chloride or the plate crystal magnesium chloride in the titanium smelting process.
8. according to the technology of claim 1 or 2 described preparing high purity ultra-fine magnesium hydroxide by sodium hydroxide method, it is characterized in that: described sodium hydroxide solution is that the concentration of preparing with sheet technical grade sodium hydroxide is the solution of 300～350g/l.
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| CN105366697A (en) * | 2015-12-14 | 2016-03-02 | 苏州市泽镁新材料科技有限公司 | Preparation method of high-purity magnesium hydroxide |
| CN107344724B (en) * | 2016-05-04 | 2020-06-16 | 广州市睿石天琪能源技术有限公司 | Simple and efficient method for reducing magnesium content in salt lake brine |
| CN108059173A (en) * | 2018-01-09 | 2018-05-22 | 大连润琳科技有限公司 | Milk of lime desanding and method of comprehensive utilization |
| CN109437259A (en) * | 2018-11-13 | 2019-03-08 | 中国恩菲工程技术有限公司 | The continuous preparation method of magnesium hydroxide |
| CN110078101B (en) * | 2019-05-30 | 2022-02-01 | 福建农林大学 | Preparation and application of tea fungus disease resistant nano magnesium hydroxide |
| CN111468301B (en) * | 2020-04-17 | 2021-06-25 | 中南大学 | Method for recovering salt lake magnesium resource by fractional precipitation flotation |
| CN112320827A (en) * | 2020-10-10 | 2021-02-05 | 沈阳化工大学 | Process for preparing magnesium hydroxide by cyclic reaction |
| CN112624163A (en) * | 2020-12-01 | 2021-04-09 | 沈阳化工大学 | Magnesium hydroxide production process based on loop reactor |
| CN112537787A (en) * | 2020-12-01 | 2021-03-23 | 沈阳化工大学 | Magnesium hydroxide continuous production process based on horizontal circulating tube type reactor |
| CN113044861A (en) * | 2021-04-16 | 2021-06-29 | 乌兰中钰新材料有限公司 | Preparation method of high-purity flame retardant magnesium hydroxide |
| CN113307290B (en) * | 2021-05-20 | 2023-03-21 | 青海盐湖工业股份有限公司 | Agglomerated magnesium hydroxide with large particle size and preparation method thereof |
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