工业级氟硅酸钠制备白炭黑与氟化钠的新工艺研究

发布时间：2018-09-17 17:13

【摘要】：氟硅酸钠作为磷化工产业链的主要副产物之一,有着很强的腐蚀性和较强的毒性,任其排放会对环境造成严重影响。据统计,每生产100万吨磷肥(折P2O5),就有将近超过6万吨的氟硅酸钠副产物,而2016年国内磷肥产量预计可达2060万吨(折P2O5)左右,届时副产物氟硅酸钠将会超过100万吨,加上其他行业产生的量,氟硅酸钠年产生量将达近两百万吨。如此数量的氟硅酸钠如不加以利用而直接废弃,不仅会造成资源的严重浪费,还会给环境带来巨大的破坏。本课题采用两种不同化学工艺,以氟硅酸钠为基本原料,将氟硅酸钠中的氟源转化成氟化钠,硅源转化成白炭黑,同时获得两种附加值更高的化工产品。在获得经济效益的同时,减少污染,保护环境,意义重大。本实验制氟化钠和白炭黑采用了外加晶种分步法和表面活性剂纯碱法两种方法,讨论了两种方法的多个单因素对实验的影响,并通过正交实验分析分别对两种制备工艺进行优化,获得制备白炭黑和氟化钠的最佳工艺条件。外加晶种分步法制白炭黑和氟化钠的工艺路线是以磷肥副产氟硅酸钠和氨水为原料,先制备晶种,后经在玻璃反应器中添加晶种、原料沉淀反应、搅拌陈化、过滤分离得滤液和滤渣,滤液经加氢氧化钠溶液、真空反应浓缩、结晶、过滤、干燥得氟化钠产品,滤渣经硫酸调pH、过滤洗涤、干燥得白炭黑产物。外加晶种分步法制备白炭黑的最佳工艺条件:稀氨水占制晶种反应体积的4.7%,表面活性剂浓度为0.5%,外加晶种添加量占反应总体积的5%,快速反应滴加的氨水与总氨水体积比为0.2,反应温度为70℃,氟硅酸钠与总氨水的摩尔比为1:8,反应pH终点为8.5,陈化6小时。外加晶种分步法制备氟化钠的最佳工艺条件:反应浓缩温度60℃,蒸发量为80%,氢氧化钠的浓度为20mol/L,陈化温度为20℃,陈化时间为30min。表征结果显示制备得到的白炭黑一次粒子粒度分布为正态分布,中位径在20nm,DBP值为3.52ml/g,比表面积为178.19m2/g;制备得到的氟化钠晶体的平均粒径在110μm,在XRD图中有着明显氟化钠的晶形衍射峰。表面活性剂纯碱法制备白炭黑和氟化钠的工艺路线是以磷行业副产氟硅酸钠和纯碱为原料,先加表面活性剂,后分步加纯碱,再经液固流态化分离装置分离得氟化钠和白炭黑后,再经后续处理工艺得到更加纯净的白炭黑和氟化钠。表面活性剂纯碱法制白炭黑和氟化钠的较佳工艺条件:快速加入的碳酸钠溶液与总碳酸钠体积比为0.3,氟硅酸钠和碳酸钠的摩尔比为1:3,表面活性剂浓度为0.3%,反应温度为85℃,反应时间为3h,分离装置母液流速为24L/h。通过自行设计的液固流态化分离装置,氟化钠和白炭黑能有效的分离,二氧化硅和氟化钠的纯度分别92.18%和98.92%。表征结果显示制备得到的白炭黑粒度分布呈正态分布,中位径在208nm,DBP值为3.16ml/g,比表面积为112.24m2/g;制备得到的氟化钠晶体的平均粒径在170μm,在XRD图中有着明显氟化钠的晶形衍射峰。试验证明,本课题建立的外加晶种分步法和表面活性剂纯碱法的两种工艺路线,都能使氟硅酸钠中的氟、硅元素得到有效利用,转化成经济价值更高的氟化钠和白炭黑,工艺路线可行。
[Abstract]:Sodium fluosilicate, as one of the main by-products of phosphorus chemical industry chain, is highly corrosive and toxic, and its discharge will seriously affect the environment. According to statistics, for every 1 million tons of phosphate fertilizer (P2O5), there are nearly 60,000 tons of sodium fluosilicate by-products, and in 2016 the domestic phosphate fertilizer output is expected to reach 20.6 million tons (P2O5). About 1 million tons of sodium fluosilicate, the by-product, will be produced by other industries, and the annual output of sodium fluosilicate will reach nearly 2 million tons. In order to obtain economic benefits, reduce pollution and protect the environment, it is of great significance to convert the fluorine source of sodium fluosilicate into sodium fluoride and silicon source into silica. The influence of several single factors of the two methods on the experiment was discussed, and the optimum technological conditions for the preparation of silica and sodium fluoride were obtained by orthogonal experimental analysis. The technological route for the preparation of silica and sodium fluoride by-product of phosphate fertilizer was the step-by-step method with the addition of crystal seeds. Sodium silicate and ammonia water were used as raw materials to prepare seeds, then added seeds in glass reactor, precipitation reaction of raw materials, agitation aging, filtration and separation of filtrate and filter residue, filtrate through sodium hydroxide solution, vacuum reaction concentration, crystallization, filtration, drying of sodium fluoride products, filtrate residue through sulfuric acid pH adjustment, filtration washing, drying of silica products. The optimum technological conditions for the preparation of silica were as follows: dilute ammonia water accounted for 4.7% of the reaction volume, the concentration of surfactant was 0.5%, the addition of seed accounted for 5% of the total reaction volume, the volume ratio of ammonia water to total ammonia water was 0.2, the reaction temperature was 70%, the molar ratio of sodium fluosilicate to total ammonia water was 1:8, and the reaction pH was 0.5%. The optimum technological conditions for the preparation of sodium fluoride were as follows: reaction concentration temperature 60 C, evaporation rate 80%, concentration of sodium hydroxide 20 mol / L, aging temperature 20 C, aging time 30 min. The characterization results showed that the primary particle size distribution of the prepared silica was normal, and the median diameter was 20 nm, D BP value is 3.52 ml/g, specific surface area is 178.19 m2/g; the average diameter of the prepared sodium fluoride crystal is 110 micron, and there is obvious crystal diffraction peak of sodium fluoride in XRD diagram. The technological route of preparing white carbon black and sodium fluoride by-product sodium fluosilicate and soda ash in phosphorus industry is to add surfactant first, then step by step. Sodium fluoride and silica were separated by Liquid-Solid Fluidization separator with soda ash, and then purified silica and sodium fluoride were obtained by subsequent treatment. The optimum technological conditions for the preparation of silica and sodium fluoride by surfactant soda were as follows: the volume ratio of sodium carbonate solution added quickly to total sodium carbonate was 0.3, sodium fluosilicate and sodium carbonate was 0.3. The molar ratio of sodium fluoride to silica was 1:3, the concentration of surfactant was 0.3%, the reaction temperature was 85 C, the reaction time was 3 h, and the mother liquor flow rate was 24 L/h. The purity of silica and sodium fluoride were 92.18% and 98.92% respectively. The particle size distribution of silica was normal distribution with a median diameter of 208 nm, DBP value of 3.16 ml/g and a specific surface area of 112.24 m2/g. The average particle size of the prepared sodium fluoride crystal was 170 micron, and there were obvious diffraction peaks of sodium fluoride in the XRD diagram. The technological route can effectively utilize fluorine and silicon in sodium fluosilicate and convert it into sodium fluoride and silica with higher economic value. The technological route is feasible.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ127.2;TQ131.12

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