Method for preparing anhydrous magnesium carbonate through magnesium-containing mother solution

Abstract

A method for preparing anhydrous magnesium carbonate through a magnesium-containing mother solution includes the following steps of firstly, adjusting the pH value, wherein ammonia gas is introduced into the magnesium-containing mother solution till the pH value is 10.0-12.0 to obtain Mg(OH)2 slurry; secondly, conducting CO2 carbonizing, wherein CO2 is introduced till the pH value is 7.5-8.0 to obtain a carbonized mother solution; thirdly, conducting pyrolysis separation, wherein the carbonized mother solution is heated and decomposed to separate solid and liquid and obtain MgCO3.3H2O solid salt and a pyrolysis separation mother solution; fourthly, conducting calcining, wherein MgCO3.3H2O is calcined to obtain anhydrous magnesium carbonate. Calcining is further conducted to obtain magnesium oxide. The MgCO3.3H2O obtained through pyrolysis separation is large in granularity, the filter separation performance is good, the carrying amount of the mother solution is small, the MgO content reaches up to 47.3%, and the total yield of magnesium ions reaches up to 92.8%; the purity of the MgO product is high, and inorganic ammonium salt type by-products can be co-produced; the method is simple in process, beneficial to industrial production, low in cost, green and environmentally friendly.

Description

technical field [0001] The invention relates to a method for preparing anhydrous magnesium carbonate, in particular to a method for preparing anhydrous magnesium carbonate with magnesium-containing mother liquor. Background technique [0002] Magnesium is an alkaline-earth metal element essential to participate in the normal life activities and metabolic processes of organisms. It is also an important basic raw material in the chemical industry, aviation and nuclear industries. It is known as "the green engineering material with the most potential for development and application in the 21st century." ", is an important strategic metal material, ranking eighth in the earth's crust. As one of the countries with the most abundant magnesium resources in the world, my country's total reserves account for 22.5% of the world, and it is also the most important driver of demand in the Asia-Pacific region and even the world. With the rapid development of aviation, aerospace industry,...

AI Technical Summary

Problems solved by technology

[0004] In recent years, literature has reported a lot of researches on utilizing magnesium-containing mother liquor to produce magnesium products, such as CN101698490A, CN102849761A, CN103803607A, CN104261442A etc. respectively disclose the method of utilizing magnesium salt solution and ammonia water, liquid ammonia or mixed alkali to extract magnesium hydroxide technology, but the obtained products all show small particle size, are not easy to filter, and are difficult to implement industrialization; CN10170641A discloses a process for recovering magnesium from magnesium sulfate solution, which also uses ammonia precipitation and CO 2 Magnesium is recovered by carbonization, but two-step alkalization is required, and the process is complicated. Causticization with calcium hydroxide or calcium oxide introduces other ions, which increases the subsequent separation process; ammonia water precipitates magnesium hydroxide in one step and pyrolysis product basic carbonic acid The difficult problem of filtering magnesium still exists; CN102653408A adopts pyrolysis of higher temperature (80~105 ℃) to obtain basic magnesium carbonate, and does not fundamentally solve the industrial problem of difficult filtering; CN1059407C also adopts higher temperature (80~105 ℃). 100°C) pyrolysis directly results in the precipitation of magnesium carbonate, however, magnesium carbonate is a very easily hydrolyzed inorganic salt, and it is easier to form Mg(OH) with lower solubility in the aqueous environment. 2 Precipitation, extremely difficult to filter; although CN101760642A and CN101760643A respectively improved the decompression evaporation process and ammonia recovery process on the basis of CN10170641A, reduced energy consumption, enriched product categories, and reduced environmental pollution problems, but none of them precipitated products Propose a fundamental solution to improve the filtration performance