DD299875A7 - METHOD FOR THE PRODUCTION OF BRIKETTABLE MGO STRUCTURES - Google Patents

Abstract

The invention relates to a method for producing a brikettierfaehigen magnesium oxide powder, which is obtained by thermal decomposition and further processed in several stages. The aim and the object of the invention are to eliminate the material-related Brikettierschwierigkeiten obtained from Spruehroestoxiden MgO powders. According to the invention, the object is achieved by desulfating the MgCl 2 solution fed to the pyrolysis with CaCl 2, an excess of 2-10 g / l in the resulting solution and hydrating the resulting MgCl 2 -containing MgO pyrolysis product with water to give Mg (OH) 2 in which, by addition of hydroxyl ions, the composition of the aqueous phase is to be adjusted so that MgCl 2 concentrations of 0.2 to 5 g / l are maintained and then the Mg (OH) 2 is filtered, washed and calcined by known methods ; manufacture; Method; pyrolysis; briquetting; Spruehroestoxid; CaCl2; MgCl2 concentration}

Description

Field of application of the invention

The invention relates to a method for producing a Brikottiorfähigon magnesium oxide powder from Sprühöst-MgO, which was obtained by thermal decomposition of magnesium chloride solution in a pyrolysis and converted by hydration and calcination in a pure reactive MgO powder, then by briquetting on roller presses and sintering in the high-temperature shaft furnace high-purity MgO sinter is further processed. The invention can be applied to eliminate the Brikettiersci usually occurring in this process in the calcined MgO-Kauster to ensure an economical production of MgO sinter by this method.

Characteristic of the known state of the art In the practical realization of the process of producing MgO sinter from sprayed oxide, it has been found that

the briquetting ability of the product prepared in this way by MgO hydration and subsequent calcination

MgO powder is subject to strong fluctuations and is generally much lower than the briquetting ability of MgO powder,

obtained from seawater installations and magnesites (Uzberg, Neorganiceskie Materialy, USSR, Vol. 19, No. 9, pp. 1318-1321;

Gardner / Messing, Thermochimica Acta, The Netherlands 78 (19841, p. 17-24). It was repeatedly stated that, despite occasionally falling briquetting yields, no oino was worth mentioning Change in chemical purity is still observed in other measurable chemical-physical quality parameters

could be. The investigation of Kato A. (Ceramic Bulletin Vol. No. 4/1987) proves the outstanding influence of the

Manufacturing process on the morphology of the MgO powder and sen further processability. In evaluation of the prior art, there are various solutions that improve the dos Briquetting in MgO products obtained by the pyrolysis process. To improve the Brikettierausbringens was described in DE-OS 2060089, DD-WI '74461, DE-OS 2529744, DD-WP 230522 and Steinicke (Christall Research & Technology Berlin 18 [1983], p. 793-798) proposed such a MgO powder Influencing the microstructure to change so that an improvement in Brikettierfähigkeit occurs. In the technical Execution is then the application of vibrating jet and planetary mills as well as of disintegrators, which a high To cause energy input into the material, described. These units are usually limited in their throughput

and require high investment and operating costs.

According to DD-WP 220951 an intensive stirring at 100 ⁰ C in the hydration process to solve the Brikettierproblem Energy inputs of 10 to 100kW / m ³ proposed to disrupt the mechanical damage of the briquetting To effect hollow sphere structures. This is done by adding a small percentage (0.1 to 1%) of magnesium hydroxide

be promoted, which is freshly precipitated from MgCl ₂ solution by alkaline precipitation with NaOH. The realization of this

Va ^! Ante is also associated with high operating costs. According to DD-WP 218077, the task is accomplished by converting the

heavy or non-brikettable MgO powder in a pre-granulate with 6-15% water added when using

Intensive mixers, which can then be briquetted well on roller presses, solved. The disadvantage of this solution is that an additional, the operating costs burdening process stage required

and that the improvement in Brikettierfähigkeit be purchased with a decrease in Kornraumgewichtes in the sinter

According to DD-WP 236081 a process for the preparation of a brikettierfähigen MgO powder is described, which is a total Hydration of the spray toughened MgO to MgO hydroxide by the application of a combination of process parameters using the Accelerate hydration, has to content. It is described that a slight excess of CaCl ₂ in the Sprühöstprozeß used MgCl ₂ solution with contributes to the formation of the briquetting disturbing structures too

prevent. According to DE-OS 2608567 it is known to start from a desired CaCl ₂ content in the starting solution of 10-25 g / l. Furthermore, US Pat. No. 3,484,195 discloses to desulfate MgCl ₂ solutions by means of CaCl ₂ .

In the practical application of the method according to DD-WP 236081, however, the briquetting problem could in principle

not be solved.

Object of the invention

The aim of the invention is to eliminate briquetting difficulties associated with the briquetting of MgO powders obtained from sprayed oxides. With the achievement of a high MgO Brikettierausbringens should be possible without the use of an additional energy-intensive process stage, the economic production of high-rouge and high-density MgO sintered from a Sprühöst-MgO.

Explanation of the essence of the invention Oer invention is the technical object of the formation of the labeling disturbing structures without the To prevent involvement of an additional stage of the process, so that Bristittierung the MgO powder aufwalzen- and Briquetting presses with high Brikettausbringen is given. The invention solves the task exclusively by targeted changes in the process control. It has been found that well briquettable MgO structures form when concentrated to 540 ~ 560g / l MgCl ₂ MgCl ₂ solution is desulphated prior to thermal decomposition in the pyrolysis reactor by the addition of calcium chloride solution

and the reaction reaction is conducted so that the MgCl ₂ solution after desulfurization has a CaCl ₂ excess of 2-10 g / L.

In the; Process stage hydration, the real substance system is characterized by the presence of the following ions and solids,

since complete decomposition of the MgCl ₂ to MgO and hydrogen chloride gas in the pyrolysis reactor does not take place: Mg ", Cl"",OH", Mg (OH) ₂ , CaSO ₄ .

Depending on the variation in the chemical composition of Sprühöstoxides change

ion ratio in the hydration of MgO to Mg (OH) ₂ in the solution. Depending on the Mg ** and OH ~ excess in the

System noticeable influence on the micro and macro structure. It has surprisingly been found that dio

for good briquetting material conditions are given only if the hydration conditions are adjusted so that the resulting reaction solution has a MgCl ₂ content of 0.2g / l to 5g / l, preferably 0.2-0.8g / l. In order to allow the process to proceed in this area, according to the invention, the uncleaved MgCl ₂ in the

Sprühöstoxid (maximum 5% MgCl ₂ admissible) during hydration by addition of hydroxyl ions (KOH, Ca (OH) ₂ , NaOH

ua.) be buffered.

By this process control according to the invention, the formation of harmful for briquetting structures that are in

the material systems MgO-Mg (OH) ₂ -MgCI ₂ -H ₂ O / MgO-Mg (OH) ₂ -MgSO ₄ -H ₂ O as Magnesiumchloridhydrate or

Magnesium oxysulfate hydrates can be avoided. In the application of this modified process control according to the invention even the cleaning product from the Roasted gas system of pyrolysis, which may have a MgCl ₂ content up to 20%, fed back to the processing process

and converted into briquetting structures.

The briquetting structures prepared in accordance with the invention also become MgO-Kauster in the calcination of Mg (OH) ₂

not destroyed, so that the Brikettierwalzenpressen a good brikettierfähiges MgO powder can be supplied. The solution according to the invention is explained in more detail in the following embodiment:

Ausiührungsbelsplel 1

20m ³ noble brine of the composition

436 g / l MgCl ₂ , 23.8 g / l MgSO ₄ , 1.9 g / l KCl, 5.4 g / l NaCl

with a density of 1.33 g / cm ³ become with 1.78 m ³ a. 25% CaCl ₂ solution (density 1.23 g / cm) at θμογ temperature of 45 ⁰ C reacted.

This produces 640kg of gypsum, which is filtered off, with 43.9% adhering solution and 21, Om ³ desulphated solution of composition

423 g / l MgCl ₂ , 1.8 g / l KCl, 5.0 g / l NpCl

1.5 g / l CaSO ₄ , 5.0 g / l CaCl ₂ , density 1.300 g / cm ³

The entsulfatisierto solution is then entbort with ion exchange resins and fed to the pyrolysis. she will

concentrated and thermally split. This creates 4115kg Sprühöstoxid the composition:

MgO 90.05% MgCl ₂ 3.16% KCI 0.92% NaCl 2.55% CaCl ₂ 2.5-3% CaSO ₄ 0.77% bulk weight 610g / l.

The Sprühöstoxid is suspended in the hydration with 10.91 m ^{3 of} deionized water and in the temperature range of

85-94 ⁰ C reacted at an average residence time of 12 hours. By adding an equivalent amount of hydroxyl ions (calcium hydroxide, potassium or sodium hydroxide solution) in the liquid leaving the reaction, the MgCl ₂ concentration is adjusted so that in the reaction solution, a resulting content '. IgCI ₂ of 0.5g / l.

The resulting hydroxide has a degree of hydration of 90%. It is subjected to a double washing, tempered

and calcined in the deck oven according to proven regime.

This creates 3772 kg of causal composition

MgO 99.14%

CaO 0.35%.

The oyster is allowed on profiled roller presses with a 300 mm press belt and a belt force of 9.0-9.51 / cm Alveoli measuring 30mm x 2.5mm χ average 15mm (L x W x H) or to chopsticks of the dimension

90mm x 25mm x average 20mm with a bulk density of 1.9-2.1 g / cm ³ pressed.

The Briketterzeugung a press is between 2.3 to 3.0t / h (based on shaft furnace task). Embodiment 2

1000 kg of the product of the composition pyrolysis of the pyrolysis of the composition 45.1% MgO, 36.2% MgCl ₂ , 0.6% CaCl ₂ , 0.6% CaSO ₄ , 0.8% KCl, 1.3% NaCl and 14.4% of water are suspended with 1.21 m ^{2 of} deionized water and continuously reacted iu magnesium hydroxide in the temperature range of 70-90 ° C at oinor average residence time of 8 hours. By addition of hydroxillones, the decomposition process must be controlled very consistently, since the MgCl _{2 of} the cleaning product is predominantly in the form of complex hydrous oxide chloride compounds, so that a resulting MgCl 2 content of 5 g / l is maintained in the reaction solution, with a hydroxyl ion excess of 1 -IOg / m ³ . All in all, 4151 48% NaOH are needed to control the implementation process. The resulting hydroxide has a degree of hydration of 95%. It is processed analogously to Example 1 to 561 kg «auster the composition 98.9% MgO, 0.44% CaO. The resulting oyster is briquetted analogously to Example 1. The Briketterzeugung a press is between 1.5-2.0t / h (based on shaft furnace task), the density of Briket.s is between 1.9-2.1 g / cm ³ .

Documents considered:

DD-WP 236081 C 01 F 5/10

DD-WP 220951 C 01 F 5/06

DE-OS 2608567 C 01 F 5/10

US-PS 3484195 C 01 F 5/22 *

Claims (2)

1. A process for the preparation of Brikettierfähigen MgO structures in MgC ^ pyrolysis process, characterized in that the pyrolysis supplied MgCl ₂ solution (Nebon components MgSO ₄ , KCl, NaCl, CaSO ₄ ) with CaCl ₂ in excess of 2-10g / desulfurized in the resulting solution and the resulting MgCl ₂ -containing MgO pyrolysis product is hydrated with water to Mg (OH) ₂ , wherein by addition of hydroxyl ions, the composition of the aqueous phase is adjusted so that MgCl ₂ concentrations of 0.2 to 5 g / l are maintained and then the Mg (OH) _{2 is} filtered by known methods, washed and calcined. 2. The method according to claim 1, characterized in that preferably MgCl ₂ concentrations of 0.2 to 0.8 g / l are maintained.