Method for preparing large-grain magnesium hydroxide by taking highly acid ammonium salt as crystal control agent

A technology of magnesium hydroxide and crystal control agent, applied in magnesium hydroxide and other directions, can solve the problems of high water content in the filter cake, difficult to filter and wash, and high concentration of free ammonia, achieve high purity, increase utilization rate, and low investment cost Effect

Active Publication Date: 2011-11-09
ZHEJIANG HAIHONG HLDG
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the magnesium hydroxide produced by the current process is a colloidal precipitate with fine particles (less than 5 microns), which is difficult to filter and wash, and the water content of the filter cake is high, and the raw materials before the reaction need to be pretreated to remove boron
The concentration of free ammonia in the reaction system is high, which is easy to cause environmental pollution
At present, there are reports on the preparation process of high-purity magnesium hydroxide, but the precipitating agent is liquid ammonia, and the ammonia gas and atomized ammonia water obtained by evaporation are complicated in process and high in equipment investment, which is very different from this technology.

Method used

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  • Method for preparing large-grain magnesium hydroxide by taking highly acid ammonium salt as crystal control agent
  • Method for preparing large-grain magnesium hydroxide by taking highly acid ammonium salt as crystal control agent
  • Method for preparing large-grain magnesium hydroxide by taking highly acid ammonium salt as crystal control agent

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0042] Continuous

[0043] (1) configuration concentration is the magnesium chloride solution of 4mol / L;

[0044] (2) Add 0.2mol ammonium chloride as a crystal control agent in the reactor, heat to 80°C and maintain a constant temperature;

[0045] (3) Mix the prepared magnesium chloride solution and ammonia according to the MgCl 2 : NH 3 = The ratio of 1: 2 is added to the reaction kettle at the same time, and it is constantly stirred;

[0046] (4) Product discharge After reacting to a certain degree, the magnesium hydroxide crystal slurry is discharged continuously through the overflow outlet that the liquid surface goes out;

[0047] (5) After the obtained magma is precipitated, the clear night of the upper layer is discharged; the lower layer of sediment is filtered, washed and dried to obtain solid magnesium hydroxide.

Embodiment 2

[0049] Intermittent

[0050] (1) configuration concentration is the magnesium chloride solution of 2mol / L;

[0051] (2) Add 1 mol of ammonium chloride in the reactor as a crystal control agent, heat to 90°C and maintain a constant temperature;

[0052] (3) Add ammonia water to the reaction kettle at a rate of 4mL / min, and control the MgCl 2 : NH 3 =1:1.8, after the reaction is completed, inject the reaction solution into the settling tank, and settle for 30 minutes;

[0053] (4) After the obtained magma is precipitated, the clear night of the upper layer is discharged; the lower layer of precipitate is filtered, washed and dried to obtain magnesium hydroxide solid.

Embodiment 3

[0054] Embodiment 3: difference with embodiment 1 is: strong acidic ammonium salt is ammonium sulfate.

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Abstract

The invention discloses a method for preparing large-grain magnesium hydroxide by taking highly acid ammonium salt as a crystal control agent. In the method, magnesium chloride is used as a raw material to prepare the magnesium hydroxide, 1 to 4 mol / L solution of magnesium chloride is prepared and added with a small amount of highly acid ammonium salt serving as the crystal control agent and ammonia water at a certain concentration serving as a precipitator to prepare the large-grain magnesium hydroxide. The reaction process can be performed continuously or discontinuously. The magnesium hydroxide with granularity of 10 to 40 microns and purity of 98 to 99.5 percent can be obtained. The product ammonium salt is used for preparing the ammonia water by a lime milk ammonia evaporation process and is recycled. The method has the advantages of large granularity and high purity of products, multiple specifications, low cost, no environmental pollution and easy industrialization.

Description

technical field [0001] The invention belongs to the technical field of metallurgy and inorganic non-metallic materials, and mainly relates to a method for preparing large-grain magnesium hydroxide by using strongly acidic ammonium salt as a crystal control agent. Background technique [0002] At present, foreign countries use brine or seawater as raw material and milk of lime as precipitant to prepare magnesium hydroxide. In China, there is research work on using ammonia water to prepare magnesium hydroxide, but the obtained product has low purity, small particle size, and difficult filtration, so this technology cannot be achieved. standard. The magnesium hydroxide product of this technology has large particles, high purity and simple process, which is beneficial to realize industrialization. [0003] At present, the techniques for preparing magnesium hydroxide from bischofite mainly include the following: [0004] (1) milk of lime method [0005] Using bischofite as raw...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01F5/20
Inventor 陈海贤邵平平董梅
Owner ZHEJIANG HAIHONG HLDG
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