CN1041402C - Controlling method used in the synthesizing course of directly making lithium bromide - Google Patents

Abstract

The present invention relates to a controlling method used in the synthesizing process of directly preparing lithium bromide, which belongs to the technical field of the preparation of lithium bromide. When liquid bromine, lithium carbonate and reducing agents containing ammonium are used for direct oxidation and reduction so as to synthesize and prepare the lithium bromide, two-step method is adopted to synthesize the lithium bromide, namely that the quantitative reducing agents containing ammonium and the quantitative liquid bromine carry out pre-reaction, and then surplus materials are gradually added for preparing eligible lithium bromide solution under the condition of mixing. By adopting the present invention, the reaction time can be shortened, the energy consumption can be reduced, and the production capacity can be increased. The present invention is suitable for the control of the synthesizing process of directly oxidizing and reducing for preparing lithium bromide by compound or mixture which contain ammonium, liquid bromine and lithium carbonate, such as NH4 OH, (NH4) 2 CO3, CO (NH4) 2, NH3, NH4 HCO3, etc.

Description

Control method for synthesis process of directly preparing lithium bromide

The present invention belongs to the field of inorganic chemistry and alkali metal, and relates to the technical field of lithium bromide preparation.

The molecular formula of the lithium bromide is LiBr, the molecular weight is 86.845, and the density (25 ℃) is 3464Kg/m³Melting point 547 ℃ boiling point1265 deg.C. The anhydrous lithium bromide is white cubic crystal or granular powder, is non-toxic, odorless, salty and bitter, is very easy to deliquesce, is easily soluble in water, ethanol and ether, and can be dissolved in organic solvents such as methanol, acetone and ethylene glycol. Depending on the crystallization conditions, lithium bromide can form lithium bromide monohydrate, lithium bromide dihydrate, lithium bromide trihydrate, and mixtures thereof, respectively, with water.

Lithium bromide is a high-efficiency water vapor absorbent and an air humidity regulator, and a 50-55% lithium bromide mixed solution is used as an absorbent, namely a refrigerant, of a refrigerating machine. In organic chemistry, lithium bromide is used as a scavenger of hydrogen chloride, an expanding agent for organic fibers (e.g. wool, hair). In the medical industry as hypnotics and sedatives, and also as electrolytes and chemical agents for certain advanced batteries, such as lithium batteries.

The preparation of Lithium bromide was reported in 1992 in the journal "Lithium Products March" (method for producing Lithium compounds), foreign and industrialLithium bromide is mainly prepared by neutralization, i.e. by neutralizing LiOH and Li with HBr acid₂CO₃To obtain the compound. In China, the main method for producing LiBr is still based on the neutralization method, and an iron bromide method for preparing lithium bromide by taking scrap iron, bromine and lithium carbonate as raw materials is reported, but the two methods are expensive. However, a redox direct synthesis has recently emerged, using urea as the reducing agent; hydrogen peroxide (Xinjiang Wulu wood lithium salt research institute) is used as a reducing agent; ammonia and its compounds (research institute of Qinghai salt lake, academy of Chinese sciences) are also used as reducing agents.

The research institute of Qinghai salt lake of Chinese academy of sciences has completed "research on new technique for preparing lithium bromide (small test report)" and "research on new technique for preparing lithium bromide (enlarged test report)" in 1987 and 1991, respectively, which are methods for preparing lithium bromide crystalline solid from lithium carbonate, liquid bromine and ammonia water. The amplification device is built.

The general chemical reaction equation is as follows: ………(1)

during synthesis, lithium carbonate is firstly prepared into suspension, reducing agent is added, liquid bromine is added at a certain speed under the condition of continuous stirring to prepare the lithium bromide solid crystal LiBr, then filtration and separation are carried out, and the reaction liquid is evaporated, concentrated, cooled, crystallized, separated and dried to obtain the solid crystal LiBr product.

As can be seen from the chemical reaction formula (1), during the synthesis reaction of lithium bromide, 1/2 moles of CO were produced for every mole of lithium bromide produced₂And 1/6 moles of nitrogen. Meanwhile, according to the calculation of reaction thermodynamics,a chemical reaction in the middle of the reaction, with a reaction equilibriumconstant K ═ e²³¹Almost infinite. That is, the reaction proceeds very quickly and very completely. This is so fast that about 15 litres of CO are formed for each mole of lithium bromide formed₂And N₂Gases, because the reaction proceeds very violently, the volume of the reaction mass increases a lot, often causing flash, loss of the mass, or other dangers due to improper control. The reaction is often incomplete due to flash.

The invention also uses lithium carbonate, liquid bromine and ammonia, ammonium salt reducing agent (containing NH)₄ ^-NH of ions₄OH、(NH₄)₂CO₃、CO(NH₂)₂、NH₃、NH₄HCO₃Ammonia-containing compounds and the like) as raw materials to prepare lithium bromide solution and lithium bromide crystalline solid.

The present invention aims at overcoming the said demerits and controlling the synthesis speed and process. Methods for controlling the rate of the synthesis reaction generally include: (1) controlling the reaction temperature; (2) controlling the feeding speed of one or two materials; (3) a certain material is added for a plurality of times. The three control methods play a certain control role, but prolong the reaction time. Therefore, the key technology of the invention is to adopt a synthesis method of completing the chemical reaction formula (1) in two steps in the same reaction vessel, namely preparing the pre-synthesis solution firstly, and then reacting the pre-synthesis solution with the rest raw materials to obtain the lithium bromide. Thus, the whole reaction is fast, stable and easy to control, and the whole synthesis reaction time is almost shortened by half.

The technical scheme of the invention is that the direct synthesis reaction process is divided into two stepsTo carry outI.e. first using a stoichiometric amount of an ammonium-containing reducing agent NH₄OH、(NH₄)₂CO₃、CO(NH₄)₂、NH₃、NH₄HCO₃One or the mixture of the compounds and liquid bromine are pre-reacted in a reactor under stirring and normal temperature to generate NH₄A pre-synthesis of Br, and then stepwise addition of the remaining starting materials, e.g. Li, in stoichiometric amounts with stirring₂CO₃And preparing qualified LiBr solution.

The process flow block diagram of the present invention is shown in figure 1.

The structure of the synthesis device in FIG. 1 is schematically shown in FIG. two.

In FIG. 1, in the synthesis apparatus, an acceptable LiBr solution of about 35% concentration obtained by the 2-step method is fed to a first filtration apparatus, and the remaining Li is₂CO₃After the impurity skills of solid such as silt are filtered, the solution is sent to a first concentration device to be concentrated to about 50 percent LiBr solution, and then the solution is sent to a purification device to remove NH in the solution₄ ⁺Impurities, etc., and then enters a second filtering device to remove Ca⁺、Mg⁺、Ba⁺And (5) carrying out plasma to prepare a qualified solution containing LiBr with the concentration of about 50%. This solution can be sold in liquid LiBr product form (e.g. as a refrigerant). Or further entering a second concentration device and a crystallization separation device to prepare qualified LiBr crystalline solid products, such as lithium bromide dihydrate crystals.

The specific structure of the synthesis apparatus in fig. 1 is schematically shown in fig. two, and in fig. 2: 1-a feeding funnel; 2-a stirring device; 3-container (e.g. beaker); 4-a thermometer; 5-synthetic solution.

The present invention notices that: (1) the chemical reaction is in solid, liquid and gasIn the coexistence of the two components; (2) because the reaction speed is high, the power is large, the chemical reaction basically has no induction period, and the reaction can be rapidly carried out at normal temperature or lower temperature; (3) CO generated by the reaction along with the increase of the viscosity of the feed liquid in the reaction process₂、N₂The gas foaming action is very strong; (4) the effective volume utilization coefficient of the reaction vessel is very low; (5) how to make the synthesis reaction proceed rapidly and smoothlyStable and easy to operate, and simultaneously has high yield of the product and high conversion rate of raw materials, which is the key for controlling the oxidation reduction in the synthesis process. The reaction speed is controlled by a cooling water cooling method, so that the energy consumption is high and the reaction is insensitive; the reaction speed is controlled by a method of quantitatively adding liquid bromine and reducing agent, although the reaction speed is sensitive, the reaction time is relatively prolonged, the measurement is accurate, if a slight error occurs, the reaction cannot be controlled, and the reaction liquid increases suddenly, so that flash or other dangers are caused. Therefore, the invention abandons the conventional control method, but separately carries out an intermediate reaction which determines the synthesis reaction speed in advance, namely, in the same reaction vessel 3, firstly, industrial liquid bromine or industrial ammonia water and an ammonia-containing compound are quantitatively added as reducing agents through a funnel 1 in the first step, and are stirred to generate NH₄Br pre-synthesis solution, and the second step of using the pre-synthesis solution and the rest raw materials such as industrial Li₂CO₃Reaction, namely, Li is added intothe reaction kettle in a quantitative and constant speed under the stirring of the stirring device 2₂CO₃The powder is continuously reacted to obtain qualified LiBr solution with the concentration of about 35%. And the reaction solution is sent to a first filtering device for filtering and impurity removal in the next step, so that the reaction speed is high, the reaction is stable and easy to control, and the reaction time is shortened by half compared with the reaction time by using a conventional control method.

Example (b): by adopting the two-step method of the synthetic reaction and the two-step method of the synthetic reaction used by a certain research institute in China, 212 ml of industrial liquid bromine, 208 ml of industrial ammonia water and 308 g of industrial lithium carbonate are respectively measured to carry out the synthetic reaction, and the reaction results are as follows: the method only takes 60 minutes and takes 120-150 minutes for control by a synthesis reaction method used by a certain research institute in China.

The invention is characterized in that:

1. the energy consumption is low, and the energy consumption in the synthesis process is reduced to about 50 percent.

2. The process is fast, stable and easy to control, and the time is only half of the original time.

3. The synthesis capacity can be improved by nearly one time without increasing any investment.

4. The operation procedure is not increased.

5. The method is economical and reasonable, and does not increase any investment.

The invention is suitable for use with NH₄OH、(NH₄)₂CO₃、CO(NH₄)₂、NH₃、NH₄HCO₃The process control of preparing lithium bromide by direct oxidation reduction of ammonium-containing compounds and mixtures thereof, bromine and lithium carbonate.

Claims (1)

1. A control method for the synthetic process of lithium bromide by direct method is characterized in that the synthetic process of lithium bromide is carried out in two steps, firstly, stoichiometric ammonium-containing reducing agent and liquid bromine are stirred at normal temperature for reaction to generate ammonium bromide-containing pre-synthetic liquid, and then, stoichiometric lithium carbonate solid powder is added under the stirring condition to prepare qualified lithium bromide solution.

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