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针对碳碱法处理硼精矿生产硼砂过程中存在的反应时间长、操作不安全、能耗高、资源利用率低等缺点，本论文结合侯氏制碱法，提出用侯氏制碱法的中间产物NaHCO3 直接处理硼精矿熟料制取硼砂的新工艺，为开发加工东北硼铁矿提供了新的工艺思路。本论文对硼精矿熟料在NaHCO3溶液中的溶出过程、NaHCO3-Na2B4O7-H2O理想体系的溶解度和初级成核动力学、硼砂在NaHCO3水溶液体系中的结晶过程进行了研究。系统考察了液固质量比、NaHCO3用量、反应温度、反应时间、搅拌速度等工艺条件对溶出过程的影响。在液固质量比为2.1，NaHCO3用量为理论用量的150%，溶出温度为100℃，溶出时间为60 min，搅拌速度为400 r/min时，硼精矿熟料的碳解率最高，硼的提取率可达92.88%。硼精矿熟料的物相主要为金云母、遂安石、利蛇纹石和橄榄石，硼精矿熟料与NaHCO3溶液反应，最终得到的终硼泥的物相中出现了MgCO3，Na2Mg(CO3)2新物相，遂安石物相消失。考察了各浸出工艺条件对硼精矿熟料中杂质元素浸出率的影响：Ca元素的浸出率在液固比超过1.7:1后增加不明显，Fe元素、Mg元素的浸出率在液固质量比超过2.3:1后几乎不再增加，Al元素、Si元素的浸出率在所考察范围内随着液固比的增加一直增大；碳酸氢钠用量超过理论用量的100%后，Fe元素、Mg元素的浸出率随碳酸氢钠用量增加增大不明显，Al元素、Si元素的浸出率在所考察范围内随着碳酸氢钠用量的增加而增加，碳酸氢钠用量超过理论用量的150%后，Ca元素的浸出率增加不明显；Ca元素的浸出率的最佳浸出温度为100℃，在120℃时，Fe、Mg、Si元素的浸出率最高，Al元素的浸出率在所考察浸出温度范围内随浸出温度升高而增加。Ca、Fe、Mg元素的最佳浸出时间为60 min，Al、Si元素的浸出率在所考察浸出时间范围内随浸出时间增加而增大；Fe、Mg、Si、Al元素的浸出率随着搅拌速度的加快而增大，Ca元素的浸出率随搅拌速度增加变化不大。测定了298 K和308 K时的NaHCO3-Na2B4O7-H2O体系的溶解度等温线，可知可用冷却结晶法将硼砂晶体从NaHCO3溶液中结晶出来。同时测定了NaHCO3-Na2B4O7-H2O体系的结晶成核诱导期，实验结果表明 NaHCO3-Na2B4O7-H2O体系属于易结晶体系。析出硼砂晶体在较高结晶温度下为椭圆状或不规则晶体形成的聚结体；较低温度下，随着过饱和度的增加，析出硼砂晶体由圆片状变为三棱柱状。分析了不同结晶条件下的晶体物相，所得晶体物相均为硼砂。对硼砂在NaHCO3溶液中的结晶过程进行研究，系统考察了结晶时间、结晶温度、溶液过饱和度和搅拌速度等工艺参数对结晶过程的影响。结晶时间增长，对晶体生长有利，所得硼砂晶体粒径增大。在结晶时间小于90 min时，随着结晶时间的增加，硼砂晶体的结晶率增加，结晶时间超过90 min后，硼砂结晶率增加不明显。结晶温度的升高使得小粒径硼砂晶体数增加，对硼砂结晶过程是不利的。溶液的过饱和度越大，所得硼砂晶体的粒径越小，过饱和度比较大的情况下，对硼砂晶体的生长变大是不利的。搅拌速度越大，硼砂晶体粒径越小。;Preparing borax by CO2-soda method has many shortcomings, such as long reaction time, unsafe operation, high energy consumption, low resource utilization rate. In order to solve these problems, a new process which combining with Hou’s process for soda production, NaHCO3 as the intermediate product of Hou’s process for soda production was used to react with boron concentrate to prepare borax was proposed. It provides a new process for the exploitation and utilization of ludwigite in northeast China. In this paper, the leaching of boron concentrate in NaHCO3 solution, the solubility and primary nucleation dynamics of NaHCO3-Na2B4O7-H2O ideal system and the crystallization process of borax in the NaHCO3 aqueous solution were studied.The effects of liquid-solid mass ratio, NaHCO3 consumption, reaction temperature, reaction time and stirring speed on the leaching process of B was investigated systematically. The results showed that under the optimum conditions of mass ratio of liquid to solid of 2.1:1, sodium bicarbonate consumption of theoretical amount of 150%, leaching temperature of 100℃, leaching time of 1 h, stirring speed of 400 r/min, leaching rate of B reached 92.88%. The major phases in the calcined boron concentrate were suanite, lizardite, phlogopite and olivine. After boron concentrate reacted with the NaHCO3 solution, with the suanite phase disappearing, the major phases in the boron sludge obtained were MgCO3 and Na2Mg(CO3)2.The effects of process conditions on leaching rate of the impurity elements in boron concentrate were investigated. When the mass ratio of liquid to solid was more than 1.7:1, the leaching rate of Ca increased unobviously. The increase of the leaching rate of Fe element and Mg element was not obvious, if the mass ratio of liquid to solid was more than 2.3:1. In the investigation range, the leaching rate of Al element and Si element increased with the increase of the mass ratio of liquid to solid. When the sodium bicarbonate consumption was more than 100% of the theoretical amount, the leaching rate of Fe element and Mg element increased unobviously as the sodium bicarbonate consumption increased. In the investigation range, with the increase of sodium bicarbonate consumption, the leaching rate of Al element and Si element increased. When the sodium bicarbonate consumption was more than 150% of the theoretical amount, the increase of the leaching rate of Ca element was not obvious. The optimum leaching temperature of Ca element was 100℃. The leaching rate of Fe element, Mg element and Si element was highest at the leaching temperature of 120℃. In the investigation range, the leaching rate of Al element increased with leaching temperature increased. The optimum leaching time of Ca element, Fe element and Mg element was 60 min. In the investigation range, the leaching rate of Al element and Si element increased with the increase of leaching time. The leaching rate of Fe element, Mg element, Si element and Al element increased with the increase of stirring speed, and the leaching rate of Ca element changed little with the increase of stirring speed.The solubility isotherm of NaHCO3-Na2B4O7-H2O system at 298 K and 308 K was measured, and it was known that the crystal of borax could be crystallized from the NaHCO3 solution by cooling crystallization method. At the same time, the nucleation induction period of NaHCO3-Na2B4O7-H2O system was measured. The experimental results indicated that NaHCO3-Na2B4O7-H2O system belongs to easy crystal system. At higher crystallization temperature, the borax crystal obtained was aggregate formed by elliptical or irregular crystals. At lower crystallization temperature, the morphology of borax crystal obtained changed from round sheet to triangular prism. The phases of crystals obtained at different crystalline conditions were analyzed. The crystals were all borax.The crystallization process of borax in NaHCO3 solution was studied. The effects of crystallization time, crystallization temperature, solution oversaturation and stirring speed on the crystallization process were investigated systematically. The increase of crystallization time was good for crystal growth, and the partical size of borax crystal obtained increased. When the crystallization time was less than 90 min, the crystallization rate of borax crystal increased with the increase of crystallization time. The increase of crystallization rate of borax crystal was not obvious, when the crystallization time was less than 90 min. The increase of crystallization temperature which was adverse for the crystal process of borax increased the number of small size borax crystals. When the solution saturation was higher ,the particle size of borax crystal obtained was smaller. High solution saturation was not good for the crystal growth. With stirring speed increasing, the particle size of borax crystal obtained became smaller.
|李玉花. 碳酸氢钠浸出硼精矿制备硼砂的新工艺[D]. 中国科学院研究生院,2018.|
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