WO2023284332A1 - Method for deeply removing arsenic and mercury in crude selenium - Google Patents

Abstract

The present invention relates to the technical field of scattered metal purification. Disclosed is a method for deeply removing arsenic and mercury in crude selenium. Arsenic and mercury are easily volatilized together with selenium by means of distillation, and impurities, arsenic and mercury, in selenium are relatively complex, partially exist in the form of compounds, and are difficult to deeply remove by means of simple filtration. In the present invention, a crude selenium material is melted in a reaction kettle, suction filtration is performed under a negative pressure condition to achieve separation of a main element, selenium, from large-particle arsenic and mercury so as to obtain a selenium melt having relatively high purity, vacuum distillation is performed on the collected selenium melt or a condensed selenium ingot in a vacuum furnace, selenium is volatilized in a steam form and condensed to achieve further separation of the main element, selenium, from arsenic and mercury, so as to deeply remove arsenic and mercury in crude selenium slag, thereby well achieving recycling of hazardous wastes.

Description

A method for deep removal of arsenic and mercury in crude selenium

This application claims the priority of the Chinese patent application submitted to the China Patent Office on July 16, 2021, with the application number CN202110803334.2 and the title of the invention "A Method for Deeply Removing Arsenic and Mercury from Crude Selenium", all of which The contents are incorporated by reference in this application.

technical field

The invention belongs to the technical field of purification of scattered metals, and in particular relates to a method for deeply removing arsenic and mercury in crude selenium.

Background technique

Selenium is a kind of scattered metal, its abundance in the earth's crust is only 5×10 ^-6 %, and it exists in a dispersed state. Selenium is widely used in the fields of materials, metallurgy, chemical industry, agriculture and medical treatment. With the development of semiconductors, solar cells, thermoelectric materials and the rise of selenium-rich agriculture, the demand for selenium is increasing day by day. Selenium has become a support for high-tech development and new materials. key materials for development. In recent years, with the different sources of coarse selenium slag, selenium slag high in arsenic and mercury has become more common, and their treatment has become more complicated. Both arsenic and mercury are highly toxic substances, listed as hazardous waste, and are initially compiled and referenced by the list of carcinogens published by the International Agency for Research on Cancer of the World Health Organization. In the process of purifying selenium by vacuum distillation, due to the volatility of arsenic and mercury, the content of arsenic and mercury in the obtained selenium products is relatively high, which seriously affects the product quality. Therefore, it is urgent to develop a green and sustainable separation and purification technology for arsenic and mercury in crude selenium slag.

CN110745789 discloses a crude selenium purification method. By adding a regulator to the crude selenium slag, the impurity elements in it are oxidized to change the occurrence state of the impurity components, and then use the properties of the impurity components and selenium under vacuum conditions. The difference between selenium and impurities is achieved by vacuum distillation. CN109319746 discloses a method for purifying crude selenium by vacuum distillation-sodium sulfite combined method. First, the crude selenium raw material is vacuum distilled in a vacuum furnace, and then the crude selenium volatiles are dissolved according to the ratio of liquid-solid ratio (5-10):1. In the sodium sulfite solution, the pH of the filtered filtrate is adjusted to 5-6 by adding hydrochloric acid or sulfuric acid, and finally selenium is precipitated in the form of precipitation. Although this method can realize the removal of arsenic and mercury in selenium, the refined selenium with a purity of 99.99% can be obtained , but need to consume a large amount of sodium sulfite solvent, and produce a large amount of waste water.

CN106946233 discloses a method for vacuum refining and purification of crude selenium. The crude selenium material can produce 99.9% industrial grade selenium after melting, degassing and vacuum distillation. 350°C, 250-400°C and 500-1000°C, the vacuum degree is 1-20Pa, and the distillation time is 3-4h.

CN112357893 discloses a method for purifying crude selenium by fusion filtration. The crude selenium raw material is heated and melted at 300-550° C., and then the obtained melt is filtered. The pore size of the filter is 30-500 mesh. This method can obtain a purity of 99 % around industrial grade selenium. The selenium products produced by these methods belong to industrial-grade crude selenium, and the mercury content in the processed raw materials is low, and the mercury removal effect is not obvious.

Contents of the invention

Aiming at the problems and deficiencies in the above-mentioned prior art, the present invention provides a method for deep removal of arsenic and mercury in coarse selenium slag, that is, the two-stage physical process of negative pressure suction filtration-vacuum distillation is used to purify crude selenium. Efficient removal of arsenic and mercury in selenium products has the characteristics of short process cycle, low cost, green and energy saving, and specifically includes the following steps:

(1) The crude selenium material is heated and melted in the reactor, and the resulting melt is subjected to negative pressure suction filtration, so that the main element selenium, arsenic, and mercury are separated for the first time to obtain an industrial-grade selenium melt; negative pressure suction During the filtration process, the filter screen adopts multi-stage filtration, and the aperture of the filter screen is 500-1500 mesh;

(2) The industrial-grade selenium melt obtained in step (1) is subjected to vacuum distillation in a vacuum furnace to realize the separation of the main element selenium from arsenic and mercury again, and the output meets the selenium specified in Se999 in the YS/T223-3007 standard product.

Preferably, the crude selenium material in the present invention is crude selenium slag, the main mass percentages are as follows: Se 80-99%, As 0.001-3%, Hg 0.01-1%.

Preferably, the negative pressure suction filtration in the step (1) of the present invention is: by vacuuming under the filter screen, a certain pressure difference is formed between the upper and lower sides of the filter screen, and the pressure difference is above 100Pa.

Preferably, the melt is kept warm during negative pressure suction filtration in step (1) of the present invention.

Preferably, the melting temperature in step (1) of the present invention is 240-500° C., and the melting time is 20-60 minutes.

Preferably, the vacuum distillation temperature in the step (2) of the present invention is 250-450° C., the vacuum degree is 1-50 Pa, and the distillation time is 2-3 hours.

The present invention adopts negative pressure suction filtration-vacuum distillation combined process to purify crude selenium, deeply removes arsenic and mercury in selenium, first heats and melts crude selenium slag (containing 80-99% of selenium), and then carries out negative pressure suction filtration , and finally through vacuum distillation and refining, high-quality selenium products with a mass percentage of more than 99.9% can be produced more efficiently.

The fusion filtration section of the present invention utilizes the differences in the melting points of various metals and their compounds to melt selenium into a melt by controlling the temperature, and the impurity elements are distributed in the melt in the form of slag, and most of the volatile arsenic and arsenic are removed by filtration. Mercury; the vacuum distillation section is mainly used to remove non-volatile arsenic and mercury, which mainly exist in the form of compounds, and use the difference in vapor pressure between selenium and impurity components to remove the remaining arsenic and mercury and others by distillation Impurities. The negative pressure suction filtration section of the present invention vacuumizes under the filter screen, so that a certain pressure difference is formed between the upper and lower sides of the filter screen, and the smooth filtration of the selenium melt at low temperature is realized.

Beneficial effects of the present invention:

The method of the present invention can realize large-scale production in industry, and the recovery rate of selenium can reach more than 90%. Compared with other methods, the method can quickly and efficiently remove arsenic in selenium slag through only two physical separation processes And mercury, the process is simple, low cost, green and pollution-free; at the same time, impurity elements arsenic and mercury are further enriched and recovered in the form of slag.

Instructions attached

Fig. 1 is a process flow diagram of the present invention.

detailed description

The present invention will be described in further detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the content described.

Example 1

Weigh 200g of crude selenium whose main components are Se 96%, As 0.42%, and Hg 0.33%, put it on the stainless steel screen with an aperture of 500 mesh, put a receiving crucible under the screen, and put them together in the reaction kettle for heating and melting , after the temperature in the reactor reaches 250°C, that is, after the thick selenium inside is melted, vacuumize under the reactor, take it out after 30 minutes of heat preservation, and obtain 164.5g of selenium melt in the receiving basin; put the obtained selenium melt into the Vacuum distillation was carried out in a vacuum furnace with a vacuum degree of 1 Pa, a temperature of 270° C., and a heat preservation of 2 hours to finally obtain 162.9 g of selenium.

ICP-AES was used to quantitatively analyze the impurity elements arsenic and mercury. The contents of arsenic and mercury in selenium products were 3.75ppm and 287ppm respectively, and the removal rates reached 99.91% and 91.30% respectively; the direct recovery rate of selenium was calculated to be 81.45%.

Example 2

Weigh 200g of crude selenium whose main components are Se 96%, As 0.42%, and Hg 0.33%, put it on the stainless steel screen with an aperture of 1000 mesh, put a receiving crucible under the screen, and put them together in the reaction kettle for heating and melting , after the temperature in the reactor reaches 350°C, that is, after the thick selenium in the inside melts, vacuumize under the reactor, take it out after 30 minutes of heat preservation, and obtain 159.7g of selenium melt in the receiving basin; then put the obtained selenium melt into Vacuum distillation was carried out in a vacuum furnace with a vacuum degree of 30 Pa and a temperature of 400° C. for 2 hours to obtain 157.6 g of selenium.

ICP-AES was used to quantitatively analyze the impurity elements arsenic and mercury. The contents of arsenic and mercury in selenium products were 4.23ppm and 275ppm respectively, and the removal rates reached 99.90% and 91.67% respectively; the direct recovery rate of selenium was calculated to be 78.80%.

Example 3

Take by weighing the thick selenium 200g that main component is Se 96%, As 0.42%, Hg 0.33%, be placed on the 1500 mesh stainless steel screen of aperture, put one deck screen again under the screen, then put a receiving crucible below, will They are put together in the reactor and heated and melted. After the temperature in the reactor reaches 500°C, that is, after the crude selenium inside is melted, vacuumize under the reactor, keep warm for 30min, and take it out to obtain 156.8g of selenium melt in the receiving basin. ; Then the obtained selenium melt was placed in a vacuum furnace for vacuum distillation, the vacuum degree was 10Pa, the temperature was 500° C., and the temperature was kept for 2 hours, and finally 154.2 g of selenium was obtained.

ICP-AES was used to quantitatively analyze the impurity elements arsenic and mercury. The contents of arsenic and mercury in selenium products were 1.56ppm and 132ppm respectively, and the removal rates reached 99.96% and 96.00% respectively; the direct recovery rate of selenium was calculated to be 77.10%.

Comparative example 1

Weigh 200g of crude selenium whose main components are Se 96%, As 0.42%, and Hg 0.33%, put it on the stainless steel screen with an aperture of 500 mesh, put a receiving crucible under the screen, and put them together in the reaction kettle for heating and melting , after the temperature in the reactor reached 250°C, that is, after the thick selenium in the inside melted, vacuumize it under the reactor, take it out after the insulation for 30min, and obtain 164.5g of selenium melt in the receiving basin.

ICP-AES was used to quantitatively analyze the impurity elements arsenic and mercury. The contents of arsenic and mercury in selenium products were 18.34ppm and 997ppm respectively, and the removal rates reached 99.56% and 69.79% respectively; the direct recovery rate of selenium was calculated to be 85.68%.

Comparative example 2

Weigh 200g of crude selenium whose main components are Se 96%, As 0.42%, and Hg 0.33%, and put it in a vacuum furnace for direct vacuum distillation at a vacuum degree of 1 Pa, at a temperature of 270°C, and keep it for 2 hours to finally obtain 169.2g of selenium.

ICP-AES was used to quantitatively analyze the impurity elements arsenic and mercury. The content of arsenic and mercury in the selenium product was 62.5ppm and 1819ppm respectively, and the removal rate reached 98.51% and 44.88% respectively; after calculation, the direct recovery rate of selenium was 88.13%.

It can be seen from the above examples that the preparation method of high-quality selenium provided by the present invention has realized the efficient removal of impurity elements in the coarse selenium slag, especially the difficult-to-remove elements arsenic and mercury, and the high yield of selenium, which has the advantages of technological The invention has the characteristics of brevity, low cost, green energy saving and the like; the high-quality selenium product prepared by the method provided by the invention has a purity of more than 99.99%, and has good economic value and industrial application value.

The descriptions of the above embodiments are only used to help understand the method and core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (6)

1. A method for deep removal of arsenic and mercury in crude selenium, characterized in that it comprises the following steps:

   (1) Heat and melt the crude selenium material in the reaction kettle, and carry out negative pressure suction filtration on the obtained melt, so that the main element selenium, arsenic, and mercury are separated for the first time to obtain an industrial-grade selenium melt; negative pressure suction filtration During the process, the filter screen adopts multi-stage filtration, and the aperture of the filter screen is 500-1500 mesh;

   (2) The industrial-grade selenium melt obtained in step (1) is subjected to vacuum distillation in a vacuum furnace to realize the separation of the main element selenium from arsenic and mercury again, and the output meets the selenium stipulated in Se999 in the YS/T223-3007 standard product.
2. The method for deeply removing arsenic and mercury in crude selenium according to claim 1, characterized in that: the crude selenium material is high-arsenic-mercury crude selenium slag, and the main mass percentages are as follows: Se 80-99%, As 0.001 ~3%, Hg 0.001~3%.
3. The method for deeply removing arsenic and mercury in crude selenium according to claim 1, characterized in that: the negative pressure suction filtration in step (1) is: by vacuuming under the filter screen, a certain pressure is formed up and down the filter screen Difference, pressure difference above 100Pa.
4. The method for deep removal of arsenic and mercury in crude selenium according to claim 1, characterized in that the melt is kept warm during negative pressure suction filtration in step (1).
5. The method for deep removal of arsenic and mercury in crude selenium according to claim 1, characterized in that: the melting temperature in step (1) is 240-500° C., and the melting time is 20-60 minutes.
6. The method for deeply removing arsenic and mercury in crude selenium according to claim 1, characterized in that: the temperature of vacuum distillation in step (2) is 250-450°C, the degree of vacuum is 1-50Pa, and the distillation time is 2-3h .

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