DD272288A1 - METHOD FOR HYDRATISING MAGNESIUM OXIDE FROM THERMAL MAGNESIUM CHLORIDE CLIP - Google Patents

Abstract

The invention includes a method of hydrating magnesium oxide from thermal magnesium chloride cleavage. The invention relates to the hydration of magnesium oxide from the one- and / or two-stage magnesium chloride cracking process in a continuous process. According to the invention, a pre-hydration stage is followed by a continuous wet milling followed by a post-hydration stage. Active cyclone oxide from the single-stage cracking process is fed only after the milling stage. By virtue of the invention, the MgO is hydrated almost completely and a degree of hydration of 95% is achieved.

Description

Field of application of the invention

01 invention can be applied in the basic industry and relates to the process of hydration of magnesium oxide, which is produced by thermal dissociation of Magnesiumchororkholen or Magnetiumchloridhydrateri.

Characteristic of the known state of the art

In one-step MgO production process, the preconcentrated MgCl 5 floatation is carried out in a so-called pyrolysis reactor or spray rust reactor. Due to the Speilfik the reactor is a division of the cleavage product into the so-called cone product, which is deposited at the bottom of the reactor, and in the cyclone product, which discharged through the exhaust gas from the reactor and upper downstream mechanical separation organs, ium example, a twin siyklonanlage separated ,

In the two-step process, a MgClr.sub.2 hydrate is produced in a spray dryer from a concentrated MgCl.sub.2 solution which is then thermally separated after separation from the Qas stream in a cleavage reactor. Partially, each of the two stages is operated in direct current, integral is the Spaltverfehren | edoch a GegenstromproieQ. The separation of the cleavage product takes place in a cyclone plant arranged between the tube reactor and the spray dryer. The cleavage product acts as a product mass flow.

The majority of the thermal splitting methods have in common that as a rule the cleavage product was exposed to high thermal loads. whereby his activity is negatively affected. This has negative effects on the further stages of processing, such as briquetting and sintering, and on the process. It must be accepted for this reason, quality losses, for example, the grain weight.

It is known that in order to achieve good briquetting and sintering behavior, the magnesium oxide prepared by thermal cracking must be subjected to a structural bouncing mold such that the magnesium oxide is hydrolyzed and then re-dried and calcined. It is also known that the highest possible degree of hydration must be sought.

The hydration is generally carried out as follows:

Via mechanical Austragt- and transporting members passes daa entire product in a stirred reactor in which it at elevated temperatures lt \ *, n is angemaitcht 90Ό example with water.

The water is presented. The process takes place within several hours, after which further processing takes place, for example, by clarification and filtration at least once, and by using sufficiently large rectors and parallel or series connection, the hydration can also be carried out quasi - continuously

Hydration temperature wwd «n if necessary, the Hydratlslargeflße does direct or indirect way · strangled. Dutch upper run becomes dab ·! For example, the suspension is transferred to the second tube reactor in the same way as the dehydration is done. Daa remaining · MgO »oil ikh nahaiu volliilndlg tu Mo (OH), umiatian, wherein the Hydratltiargrad> OO protanl be great.

A high degree of hydration with dabai is very good · Brikaulatbarkelt and high 8lntaidicht ·. (XaM methodology, for example, in Journal .New Bargbautachllk * 16 (1MB) 3,8alta 293, dargaitalh, hlar «patlall mh • Inam ROhrraaktor, followed by thickener and filter with Waste iwlsche.Diaa talgt that dia hydratiation and daa dissolving out of chlorine compounds also technically difficult alnd.

In the expectation, investigations on the llllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll the hydration that the reaction rate decreases sharply after a few hours owing to the hydroxide layer forming on the particles, which inhibits the further reaction with the MgO still present.

Expression for lat dl · found experimentally reproducible · flattening In the eratan 3 hour rising Hydratlsierkurve, which then asymptotically a value closer, the cone oxide is about at a Hydratislargrad of 75%.

In practice, only Hydretislergrada of 65 to 7OH are achieved accordingly.

As a result, inadequate briquetting and sintering behavior occurs. In addition, in subsequent apparatuses (for example, thickener or liquidator) turn off the Mg (OH), with the remaining free MgO come.

Additional difficulties arise from the fact that coarse particles (angasintertea Materiel, agglomerates, aborted Anslue) contained in Kot.usprodukt in the single-stage process, which hardly hydrate under the conditions described above. In addition, they pass into the poured-on apparatus, accumulate there, and disturb production disturbances, and it must also be accepted that not completely completely hydrate-lysed particles and impurities, for example alkali chlorides, are included in the further processing product In the case of unstable processes, coarse particles do not enter into the cyclone plant, but if they are produced in the cracking or spray dryer, they are separated and subjected to special mechanical treatment before being re-pulped, but you are poorly affected The separation of these interfering end-points, even after mechanical treatment, is almost impossible by inspection of the conical product or other products.Experiments have failed even when using a high-quality Zlck-Zack-Sichtanlage e product temperature is also a major obstacle to classifying processes in general. Moreover, on average, the particle size is so small (single-stage at 10-20 μm, generally 40-60 μm) that screenings are hardly technically feasible and sightings as mentioned above are also impracticable. There are the following suggestions for improving hydration: repeated mashing of the product with water (DD WP 147939), addition of electrolytes such as NH ₄ Cl, MgCl ₁ . MgSO _4. CaCl 2 (DD WP 239081, DD WP 74461, DD WP 241247), addition of filling agents such as NeOH (DD WP 220951).

These procedures do not turn the desired success, since in this way the hydroxide layer inhibiting the reaction is not eliminated, not by intensifying intensively the stirring process. The addition of such substances also leads tu increased demands on the WaKh and Filterproieß. It is a high purity product. should be honored. Sintered surfaces are not activated by the previous methods and agglomerates hardly destroyed. Furthermore, proposals for dry milling dea exhausts before the Hydrolotslsung In a disintegrator confesses (DE-OS 3246650). As a result, the coarse constituents of the cone can be destroyed, but the above-mentioned inhibiting effect of the Mg (OH) layer of the particles during hydration is not abolished. In addition, alch results in an increase in undesirable fines, apart from the thermal load of the grinding units. The intensification of the suspension at 100 ° C. proposed in the patent DO WP 220951 for the elimination of undesired oxide-oil oxide structures leads to high wear of the aggregates, to material problems as well as to high energy consumption. Trottdem solidified agglomerates, t.B. Lugs or sintered particles, not activated. DD WP 46225 proposes the eight-hour wet milling of the deaerating oeoxidea in a ball mill and a subsequent cold inling. For such a process huge equipment (several mills) are necessary to ensure the necessary production throughput on an industrial scale tu. In addition, Naßmahlversuche have reported over a long period of time a rapidly decreasing degree of vermination or degree of digestion and delivered substantial fixed portions, which have led to enormous difficulties until turn halting process in the Ki tion or thickening of the suspension and in the subsequent filtration. The discontinuous process, even with increased aggregate number and quasi-continuous operation, also requires a much higher monitoring and operating effort.

ZW of the invention

The aim of the invention is to achieve with minimal energy and equipment expense without Zusati of chemicals almost complete hydration of Sprühröstoxides, in order to create the conditions for a high purity product tu, which has a good Brikettier- and sintering behavior after calcination.

Explanation of the essence of the invention The invention is based on the technical object, in a continuous technical Hydrotisierprozeß magnesium oxide

a nearly complete one-and / or two-stage hermetic splitting process of magnesium chloride

Reacting magnesium hydroxide, so that the product has a degree of hydration a 95%. According to the invention, this object is achieved as follows: The cleavage product is prehydrated in a hydrator at 80 ... 95 * C with stirring (degree of hydration 50 .. 45%). Subsequently, the suspension is continuously introduced into a Naßmahlaggregat, z. B. in a continuously working Ball mill, wherein the vorhydretlslerte product is briefly subjected to a wet grinding in such a way that rJabel a Activation by exposure of reactive surfaces and elimination of external disturbances inhibits reaction Hydroxldechlcht the particles takes place. In this case, agglomerates and other coarse fractions of 8% fluoride are used

destroyed and activated for hydration.

Due to the continuous Nauvermahlung with low Verwellielt the Hydratlilervorgang is accelerated significantly. Cs

a reaction rate is reached, which corresponds to the initial phase and from which a significant increase in the

Hydratlslergredea results. The suspension gelled out of the cheese granulate and continuously removed is added in another Hydretlslerapparet, which is also formed ata tube reactor, registered. It was found that in this the qussl

Renewed Raise continues to be forfeited.

The division of the cleavage product in the single-stage slit process in the cone and Zyklonprudukt leads tu another Embodiment of the invention. It was found that the cyclone oxide trud; the high temperatures used in the one-stage process ice

reactive product behavior. This is surprising, since the main part of the Zyklonoxids certainly in the so-called

NaQione or burner level of Reaktora has undergone significant thermal stresses. It is already inside of the priesthood Time completely hydrat'slert, thus it requires no mechanical activation. Surprisingly, it was found that the addition of the Zyklopproduktes In leaving the Naßmahlstufe Suspension stream hydration is further accelerated. In the procedure according to the invention, the product leaving the hydrotreater system has a hydrate rating> 90%, which

By intensively shaping the wet wetness hydration still values as much as 95% can be increased.

In the two-stage cleavage process, it has proved to be advantageous, mechanically vorierklelnerte Ansltte from the Feed the spray drier only after wet grinding, while pellets from the cleavage reactor must always be fed before Wet grinding can be abandoned. These amines from the cleavage reactor must, like the cone product from the single-stage cleavage process and

corresponding amines are first loosened by swelling by partially reacting at the surfaces.

This is not the case with the spray dryer, as they react quickly. The mechanical pre-shredding of the Ansltie, which can be deducted separately during business interruptions, Is always advantageous. To further accelerate the hydration, it has also proven to be advantageous to have the one in the Nsßmahlstufe Heat the suspension stream directly to ensure a suitable hydration temperature. That can

by means of a direct introduction of steam into the suspension or indirectly via the jacket of the mill or via special installations.

Ausführungsbelsplele Implementation Guide 1 In a laboratory apparatus, 800 ml of water 60'C heated, 180g of carbon monoxide from the single-stage thermal cleavage with the Composition 92.1% MgO, 1.3% MgCl ₁ , 3.8% Alkallchloride. Suspended 1.3% CeSO ₄ and stirred for 4.5 h. The product is wet-ground for 30 minutes. Thereafter,? 0 g of cyclone oxide from the single-stage

thermal cleavage of the mixture 79.8% MgO, 10.7% MgCl ₁ , 4.6% AUalichlotid, 0.8% CeSO ₄ added. It is stirred for another 4.0 hours.

In a long-term trial, the hydration-nitriding process is carried out in several stages: After 3.0 hours of prehydration, the cone product is wet-milled for 30 minutes, hydrated for a further 3.0 hours,

Wet-ground for 30 minutes, 20 g Zykonoxld added and hydrated for another 2.0 hours.

Sampling to determine Hydratlsiergrades took place after 4.5 hours ur.d 9.0 hours. The result list

are shown in the following overview.

Experimental conditions Degree of hydration after 4.5 h Degree of hydration after 9,0 h one-time wet treatment of the cone oxide; after 5.0 h additional cyclone oxide 00,1% 92.8% two-time Noßvermahlung of Konusoxides; n «: h 7,0 h Addition of cyclone oxide 73.2% 98.5% Verglek-hsversueh 160g Konusoxid + 20gZykonoxid unbehandeltP.Oh hydrated 60.2% 73.4%

Explanatory Leaflet I: In a laboratory apparatus 800 ml of water are heated to 80 * C, to 180g Sprühröstoxid the two-stage thermal cleavage

with the composition 98.5% MgO, 0.4% MgCl, 1.1% alkali chloride, 0.9% MgSO ₄ , added 0.8% CaSO ₄ and stirred for 4.5 h.

In Ιη · · (τ "another attempt is tl» t Spruhrflatoxld 3.0 8tund 'n vorhydratlilart naftvermahjen 30 minutes to hydretlslert 3.0 8tundan, wet ground again · 30 minutes but mala hydratlilert 2.0 hours. Di · Ρ · · obenahm For determination nea H / dreslergradea each time after 4.6 hours and 0.0 hours, the results are shown in the following table.

Experimental conditions Hydratatlons · degree after 4.6 h Hydratatlons · degree after 9,0 h unique NaHvermehtung 67.3% 96.2% iwelmalige Neßvermahtung 79.3% 97.8% Verglelchiversuch unbehendeltes product ββ.3% 80.1%

Claims (5)

· Claim: 1. A process for the hydration of magnesium oxide to the thermal magnesium chloride cleavage, wherein the cleavage product obtained after the cleavage is mixed with a certain amount of water, characterized dadureh that the product continuously in a first stage, consisting of one or more in series odor parallel Hydratlslerreaktoren It is then subjected to a mechanical stress in one or more wet-milling units connected in series or in parallel and continuously operated, and subsequently passed on to one or more series-connected or parallel-connected hydrotreater reactors for further hydration. 2. The method of claim 1, wherein the magnesium oxide is prepared by the one-stage cleavage process, the so-called Ruthner * method, and incurred a coarse cone product and a fine cyclone product, gekenmelehnet characterized in that the cone product passes through the three-stage process chain and the cyclone product advantageously wave and dae cyclone product Advantageously, the suspension stream leaving the wet milling stage is added or fed directly into the downstream hydrate sparger. 3. The method according to claim 1 and 2, gekenmelehnet characterized in that the Verweilieit in the hydration each several hours, preferably 1 to 3 hours, bergesugsweise. 4. The method according to claim 1 and 2, characterized in that the temperature in all Hyratlsierungsstufen, including the Naßmahlstufe, without exception, at T> 80 * C, preferably T> * 90 * C, is held, in case of need heat energy from the outside of the process is supplied. 6. The method of claim 1 and 2 for processing Ansitzen from the one and two-stage splitting method after their separation at Produktlonsuntcbrechungen, gekmelelten in that the Ansitze separately mechanically vorzerklelnert, the shredded Ansitzen from the spray dryer of the single-stage splitting method after wet grinding and the crushed Ansitzen from the tube reactor of the two-stage splitting process and the crushed Ansitze from de Sprühröstreaktor the one-stage Spaltverfehrens before wet grinding fed into the process.