Extraction Of Germanium By Thermal Reduction Vacuum Evaporation

The lacking germanium resource is an important strategic resource, widely used in the infrared optics, optical fiber communication, aerospace, solar cells, nuclear detection, chemical catalyst, and many other national defense military and civilian fields, which is the key to support the development of national economy and national defense construction material, and germanium is the strategic purchasing and metal of China.Germanium resources only exist in the United States, China, Canada, Russia and some other countries in the world, the amount of germanium resources reserves in our country is only about 3500 tons, accounting for 40.7% of global germanium resources;and China is the world’s largest germanium production supplier, annual output of high-purity germanium is about 130 tons, accounting for 70% of global supply,in which germanium resources of Yunnan reserves 32% of China, and more than 65% of yield in China.Lincang Prefecture of Yunnan province has the world’s best-known lignite germanium ore resources, the content of germanium from lignite generally between 100 g/t ~ 600 g/t, after chain germanium volatilization fire smelting enriched we can get low grade germanium concentrate which germanium content is about 0.35 % ~ 1.50 %.This thesis mainly researched that how to extract germanium secondary from the low grade germanium concentrate produced in Lincang ‘s lignite coal germanium by reduction,volatilization and enrichment,which in order to improving the comprehensive utilization of germanium resource, reducing production cost, reducing the wet processing of environmental impact.Through experiment study, developed with sodium phosphite thermal reduction method to extract germanium volatilization enrichment in the mine, germanium, and sodium phosphite thermal reduction-vacuum evaporating concentration extraction of germanium in low grade germanium concentrate new process, get high grade reduction, germanium concentrate is used for the reduction of germanium concentrate again after alkaline oxidation pretreatment by hydrochloric acid distillation extraction germanium tetrachloride, then through purification and preparation of high-purity germanium dioxide.Through the experiment of germanium ore enrichment of thermal reduction method, high temperature and normal pressure piecewise volatilization, sodium phosphite thermal reduction of vacuum distillation separation enrichment and volatile alkali oxidation pretreatment and hydrochloric acid germanium reduction volatilization process and principle of the system such as research, analysis and put forward the germanium reduction volatilization and alkaline oxidation pretreatment process principle, finally determine the low grade reduction volatilization of germanium concentrate enrichment conditions and process parameters.The paper briefly introduces the distribution of germanium resources, the main use of the world, product yield, production technology, the main extraction methods. Then, researched and analysised of the effect on the germanium recovery equipment, temperature, evaporation and sodium hypophosphite heat reducing volatile conditions and other factors are analyzed and proposed the germanium mine fire enrichment concentrate germanium recovering rate low and improved method of existing germanium mine fire enrichment process. The test proposed in germanium ore add sodium hypophosphite thermal reduction volatilization method to improve the germanium ore smelting recovery rate, by adding 2.5 % sodium hypophosphite and the germanium volatilization rate is from 91 % to almost 100 %, nonvolatile residue in germanium grade reduces to 50 g/t.Focusing on sodium phosphite thermal reduction- vacuum evaporating concentration of germanium process method has carried on the systematic experimental study, and atmospheric temperature with piecewise roasting volatile enrichment method has carried on the comparative analysis, through the experiment on output of high grade reduction of germanium concentrate distillation separation of germanium in alkaline oxidation pretreatment and hydrochloric acid extraction method were studied.Through the design of germanium reduction volatilization furnace conditions by orthogonal experiment and single-factor experiment was carried out systematic research and analysis, at the same time, by adopting the method of thermodynamic principle and diffusion theory of reduction reaction and vacuum evaporation process were analyzed, and through the selection of reducing agent, reduction reaction process, such as volatile principle, for study, optimizing the best craft condition: evaporating temperature 1000 ℃, dosage of sodium phosphite 7.5%, vacuum degree, 500 Pa, carrier gas flow 2 L/min, volatile time 90 min, 30 mm material thickness, the germanium volatilization rate of 94.76% ~ 98.35%, under the condition of germanium content in the volatile residue reached 0.06% ~ 0.13%, concentrate grade of 12.68% ~ 12.68% of output reduction, enrichment ratio of 27 ~ 36 times.Compared with atmospheric volatile concentration, reducing low evaporation temperature below 200 ℃, the evaporating time shortens the 60 minutes, the 10 ~ 14 times higher enrichment ratio, germanium volatilization rate was increased by 22% ~ 32% from 62.78% ~ 74.50%, the enrichment of concentrates germanium content increased by 5% ~ 19%.Designed the experiment equipment of germanium, containing germanium materials test is put forward using alkaline oxidation pretreatment- hydrochloric acid distillation separation of germanium tetrachloride, then through hydrolysis by traditional distillation get high purity germanium dioxide, solved the method to get high grade reduction of germanium concentrate with conventional wet hydrochloric acid distillation process the problem of low recovery of germanium.Through the system research, optimization of process conditions for: water dosage is 2 times the weight of the germanium concentration, sodium hydroxide dosage is 30% of the weight of germanium concentrate, dosage of hydrogen peroxide(30%) 25% of the weight of germanium concentrate, pretreatment time of 1.5 h, distillation of hydrochloric acid dosage is nine times the weight of the germanium concentrate.This method can significantly increase the hydrochloric acid distillation recovery of germanium, germanium recovery rate increased to 97.90% after using this technology, and the recovery of germanium by conventional hydrochloric acid distillation process recovery rate can reach 65.16% when compared with the sulfuric acid leaching, tannin precipitation- hydrochloric acid distillation separation mention germanium by wet process, this method has high recovery efficiency of germanium, auxiliary materials consumption, simple equipment, process short, strong operability, low production cost, to avoid a large amount of emissions of waste water, waste gas and waste residue and processing, can thoroughly solve the wet processing technics germanium pollution to the environmentThe results of research show that using this process to recycle germanium from low grade germanium concentrate is feasible, with the advantage of high rate of recovery of germanium, environment friendly and wide adaptability to increase the rate of the comprehensive recovery of germanium, which reduce the production cost, save energy, emission reduction, protect the environment, and use the germanium resource more effectively. The results of this study expand the sodium hypophosphite thermal vacuum reduction volatile enriched germanium technology and alkaline pre oxidation treatment distillation extraction germanium technology in the field of rare metal application range.