黄磷炉渣提取白炭黑和磷酸氢钙的研究

【作者】 苏毅；

【导师】 杨显万；

【作者基本信息】 昆明理工大学 ， 有色冶金， 2008， 博士

【摘要】 黄磷炉渣是电炉法生产黄磷时产出的固体废弃物,工业上每生产1吨黄磷将产出8～10吨炉渣。根据我国黄磷的生产现状,目前我国黄磷企业实际年产出黄磷炉渣600～750万吨,其中云南省年产出黄磷炉渣300～400万吨。目前,黄磷炉渣主要用于生产农用硅钙肥、水泥、混凝土、磷渣砖及瓷质砖,产品品质较低,且用量有限,大部分以废渣堆积,既浪费资源,又污染环境。黄磷炉渣富含CaO和SiO₂及少量铁、铝、镁和其它元素,可用于生产含钙和含硅产品。本论文通过采用磷酸浸出黄磷炉渣,以磷酸二氢钙和磷酸氢钙的形式分离渣中钙元素及其它杂质元素后,通过精制、煅烧等工艺制备出优质的白炭黑产品,同时利用浸出液得到磷酸氢钙产品,开发了一条处理黄磷炉渣的新工艺。黄磷炉渣中硅、钙主要以CaO·SiO₂、3CaO·2SiO₂和2CaO·SiO₂等形式存在,热力学研究表明,在采用磷酸进行浸出时,这些化合物能与磷酸自发反应,分别生成水合二氧化硅和磷酸二氢钙、磷酸氢钙,同时黄磷炉渣中含有的杂质元素如Fe（以磷铁形式存在的铁除外）、Al、Mg等也将与磷酸反应生成相应的磷酸盐,根据这些磷酸盐在水中及磷酸溶液中溶解度的变化规律,通过采用过量的磷酸使用量以使黄磷炉渣磷酸浸出完毕后浸出液中含有足够的游离磷酸,可提高磷酸二氢钙和磷酸氢钙及杂质元素磷酸盐在浸出液中的溶解度,保证它们溶解在浸出液中,而硅则以水合二氧化硅沉淀析出,实现硅钙分离的目的,同时得到白炭黑和磷酸二氢钙或磷酸氢钙产品。实验研究表明:采用磷酸浸出黄磷炉渣,以磷酸二氢钙和磷酸氢钙分离钙等元素后,浸出渣经洗涤、干燥、煅烧,可得到SiO₂含量达到95%以上的白炭黑样品。磷酸浸出黄磷炉渣的最佳工艺条件为:磷酸用量80ml,反应温度为自然升降温,反应时间0.5小时,液固比5:1,搅拌速度400rpm。黄磷炉渣磷酸浸出过程可用有固相产物生成的粒径不变的收缩未反应核模型描述,磷酸浸出过程的表观速率受液膜层的扩散过程控制,在303.15K时的液膜扩散系数为1.68×10^-4m²/s。由于黄磷炉渣中含有的C、以磷铁形式存在的铁不与磷酸反应,在采用磷酸浸出黄磷炉渣时它们将残留在浸出渣中,同时磷酸浸出时生成的杂质磷酸盐也将有一部分残留在浸出渣中,因而浸出渣含有较多的杂质,所以通过磷酸浸出得到的白炭黑样品外观呈灰白略带淡红色,白度仅达到61.51%,需进行进一步处理。根据热力学分析,采用硝酸溶液进行精制处理,渣中含有的杂质元素C、Fe（以FePO₄形式存在的铁除外）、Al、Ca、Mg等均能与硝酸反应,分别生成二氧化碳和相应的可溶性硝酸盐,与浸出渣分离。实验研究表明:由黄磷炉渣经磷酸浸出得到的粗制白炭黑产品,采用硝酸溶液精制,精制除铁率可达到99%,精制白炭黑产品中铁含量可降至0.02%左右,产品白度达到90%以上。精制的最佳工艺条件为:初制白炭黑原料15克时,硝酸浓度8%,反应时间2.0小时,反应温度70℃,液固比4:1,搅拌速度300rpm。精制除铁过程可用有固相产物生成（惰性物料层）的粒径不变的收缩未反应核模型描述,精制过程的速率受界面化学反应过程控制,精制化学反应的表观活化能E_a=30.662kJ/mol,化学反应级数为0.6746。以黄磷炉渣为原料,采用磷酸浸出,以磷酸二氢钙和磷酸氢钙分离钙元素后,经精制、洗涤、干燥等工艺处理后,得到的白炭黑产品其它各项指标均能达到白炭黑产品的质量要求,但其外观仍然呈现灰白色,白度仅达到67.83%,但样品通过700℃煅烧0.5小时后可得到符合HG/T3061-1999标准的A级白炭黑产品。该产品经X-射线衍射和电镜分析确定为无定形二氧化硅、样品平均粒径66～68μm,粒径在2～200μm之间的二氧化硅占90%以上,二氧化硅含量达到97%,白度88%,比表面积205cm²/g,DBP吸油值2.01ml/g,Fe、Cu、Mn等杂质含量均能达到白炭黑产品的质量要求。黄磷炉渣采用磷酸浸出分离得到的浸出液,含有大量的磷酸二氢钙、磷酸氢钙、16～18%的游离磷酸及炉渣带入的杂质元素氟。为了有效的利用浸出液中的游离磷酸和得到含氟合格的磷酸氢钙产品,本研究采用真空蒸发、浓缩结晶、分离,母液返回浸出阶段循环利用,结晶体二次重溶制备磷酸氢钙的工艺处理磷酸浸出液。为了充分利用渣中的钙元素制备磷酸氢钙产品,将磷酸浸出液和滤渣一洗液混合后进行浓缩结晶,经分离磷酸二氢钙和磷酸氢钙混合晶体后,母液返回浸出阶段用于黄磷炉渣的浸出,当混合液真空浓缩至原液量的50%时,母液返回黄磷炉渣浸出,与直接浸出比较,可使工业磷酸用量降低37.5%,有效利用浸出液中的游离磷酸,使工业磷酸的用量明显降低。磷酸浸出液和一洗液的混合液经真空浓缩得到磷酸二氢钙和磷酸氢钙混合晶体后,经二次溶解、一步中和,可得到含氟量为0.08～0.10%的饲料级磷酸氢钙产品。产品质量中的钙、磷、氟均达到HG2636-2000饲料级磷酸氢钙产品的质量要求。本论文采用磷酸浸出黄磷炉渣,经精制、洗涤、干燥、煅烧及浸出液结晶循环利用等工艺处理,同时得到市场容量极大的白炭黑和磷酸氢钙产品,论文在产品开发思路和工艺技术方面具有创新性。项目属固体废弃物资源循环再利用技术,可充分利用废弃物资源,达到可持续发展的目的,解决黄磷生产企业的废物处理问题,具有明显的社会效益和经济效益。更多还原

【Abstract】 The yellow phosphorus slag is a solid waste of producing yellow phosphorus in electrical furnace,There are 8-10 t slag produced when 1t yellow phosphorus is produced in industry.According to the present status of producing yellow phosphorus in China,Chinese yellow phosphorus plants may discharge 6-7.5 million tons yellow phosphorus slag per year,in which there are 3-4 million tons yearly in Yunnan.At present,yellow phosphorus slag is mainly used in producing silicon-calcium fertilizer,cement,concrete,phosphorus slag brick and so on.But both the value of the product are lower and the utilizing rate of the slag are limited, the majority of them are accumulated and it cause resources waste and environment pollution.Yellow phosphorus slag contains a lot of CaO,SiO₂ and a few of Fe,Al,Mg and other elements,it may be applied to producing Ca and Si product.The paper studies technology of producing the high quality precipitated silica and CaHPO₄·2H₂O,in which yellow phosphorus slag is leached by phosphoric acid, calcium and the other element impurities is separated in form of Ca（H₂PO₃）₂, CaHPO₄ and impurity phosphates,then purified and calcined.The new technology of processing yellow phosphorus slag is obtained.The silicon and calcium exist mainly in form of CaO·SiO₂,3CaO·2SiO₂ and 2CaO·SiO₂ and so on in yellow phosphorus slag.The thermodynamics study presents that the react between these compounds and phosphoric acid can carries on spontaneously when yellow phosphorus slag is leached by phosphoric acid and form SiO₂·nH₂O,Ca（H₂PO₃）₂ and CaHPO₄ respectively,the impurity element such as Fe （exception phosphorus-iron）,Al,Mg and so on in the yellow phosphorus slag react also with phosphoric acid to form their phosphate simultaneously.According to solubility of these phosphate in water and phosphoric acid solution,the solubility of Ca（H₂PO₃）₂ and CaHPO₄ and the impurity element phosphate in the lixivium may are enhanced when the excessive phosphoric acid are used in the course of leaching and maintains enough amount of phosphoric acid in the lixivium and can guaranteed them dissolving in the lixivium,so the silicon is separated in form of SiO₂·nH₂O precipitation from the lixivium.The SiO₂·nH₂O and Ca（H₂PO₃）₂·H₂O or CaHPO₄· 2H₂O can be obtained simultaneously by separation silicon and calcium in yellow phosphorus slagThe experimental study indicated that the precipitated silica with SiO₂ 95%can be obtained after yellow phosphorus slag is leached by phosphoric acid solution and the calcium is separated in form of Ca（H₂PO₃）₂ and CaHPO₄,then leached dregs are washed,dried and calcined.The optimum technical conditions of leaching yellow phosphorus slag with phosphoric acid are:phosphoric acid 80ml,natural reaction temperature,reaction time 0.5 hours,fluid solid ratio 5:1 and stirring speed 400rpm. The leaching process of yellow phosphorus slag with phosphoric acid may be described by the unreacted shrink core model with solid resultant and the invariable particle size and the apparent rate of leaching process is controlled by diffusion process in liquid film.Its diffusion coefficient in liquid film is 1.68×10^-4m²/s at 303.15KBecause C and the Fe in form of phosphorus-iron in the yellow phosphorus slag do not react with the phosphoric acid,they will remain in the leaching dregs when yellow phosphorus slag is leached by the phosphoric acid,and some of the impurity phosphate formed will also remain in the leaching dregs simultaneously,thus the leaching dregs contain many impurities.The appearance of precipitated silica sample obtained by leaching yellow phosphorus slag with the phosphoric acid is grayish white with slight red and white degree reach only 61.51%,so it must be treated further.According to the thermodynamic analysis,when the leaching dregs are purified by the nitric acid solution the impurity element C,Fe（exception FePO₄）,Al,Ca,Mg and so on contained in the dregs can react with the nitric acid into the carbon dioxide and the corresponding soluble nitrate respectively and are separated from the leaching dregs.The experimental study indicats that when precipitated silica prepared from yellow phosphorus slag by the phosphoric acid leaching is purified by nitric acid solution,Fe content in the precipitated silica purified can decrease to about 0.02%,the removal rate of iron reach 99%and white degree is above 90%.The optimum purification technical conditions are:the nitric acid concentration 8%,reaction time 2.0 hours,reaction temperature 70℃,fluid solid ratio 4:1,stirring speed 300 rpm.The purification process may be described by the unreacted shrink core model with solid resultant（inert material）and the invariable particle size and the purification process rate is controlled by chemical reaction step on interface.Its apparent activation energy Ea is 30.662kJ/mol and its reaction order is 0.6746.After yellow phosphorus slag is leached by phosphoric acid solution and the calcium is separated in form of Ca（H₂PO₃）₂ and CaHPO₄,then leaching dregs are purified,washed,dried,the other item of the precipitated silica product obtained can all reach the quality requirement of the precipitated silica product,but its appearance is still grayish white and white degree reach only 67.83%.But the precipitated silica products reach A grade of the HG/T3061—1999 standard when the sample is calcined 0.5 hours at 700℃.The product is amorphous silicon dioxide, average grain diameter is 66～68μm,the silicon dioxide of particle size 2～200μm account for above 90%by X-ray diffraction and electron microscope analysis. The silicon dioxide content of the product is 97%,white degree 88%,specific surface area 205cm²/g,DBP absorbability value 2.01ml/g and the content of Fe,Cu, Mn can achieve the quality requirement of the precipitated silica product.The lixivium obtained from leaching yellow phosphorus slag by phosphoric acid contains a lot of Ca（H₂PO₃）₂,CaHPO₄,phosphoric acid and impurity element fluorine.In order to use phosphoric acid in the lixivium effectively and obtain qualified CaHPO₄·2H₂O product,the lixivium is treated by the vacuum evaporation,the concentration crystallizing,separation,circulation use of the mother liquor by returning to leaching stage.In order to preparation CaHPO₄·2H₂O product by using the calcium element fully,the mixture of the lixivium and first wash solution is concentrated by vacuum and then crystallized and separated,the mother liquor is used in leaching the yellow phosphorus slag by returning to leaching stage.When intermixture solution is concentrated to 50%of original liquid volume and is used in leaching the yellow phosphorus slag by returning to leaching stage,amount of using the industry phosphoric acid may be decreased 37.5% compared with the direct leaching,the industry phosphoric acid used is reduced obviously.The feed grade-CaHPO₄·2H₂O with F 0.08～0.10%can be obtained after the mixture of the lixivium and first wash solution is concentrated by vacuum and crystallized and separated,then the mixture crystal of Ca（HPO₄）₂·H₂O and CaHPO₄·2H₂O obtained is dissolved again,neutralize.The content of Ca,P,F in the product can reach quality requirement of HG2636-2000 feed grade-calcium hydrogen pyrophosphate The paper researches a technology which yellow phosphorus slag is leached by phosphoric acid solution,then leaching dregs are purified,washed,dried,calcined and the mixture of the lixivium and first wash solution is used circularly and obtain precipitated silica and calcium hydrogen pyrophosphate simultaneously,so the paper has the innovation in the application of yellow phosphorus slag and the processing technology.The project is a technology which use the solid waste resources circularly,may use the waste resources fully,achieved the goal of the continuable development and solve waste treatment question of yellow phosphorus enterprise,so it will has the obvious social efficiency and the economic efficiency.更多还原