Method for dechlorination of zinc-comprising dust from electric arc furnaces by water washing (embodiments)

Abstract

FIELD: zinc production.SUBSTANCE: invention relates to improving the purity of zinc and can be used for the disposal of metallurgical production waste, namely electric arc furnace (EAF) dust. Dechlorination of zinc-comprising dust from electric arc furnaces with the following chemical composition, wt.%: iron 39.5-40.9; zinc 12.6-13.1; manganese 4.4-4.6; calcium 3.7-4.1; sodium 1.9-2.8; silicon 2.1-2.3; chlorine 1.7-2.0; potassium 1.6-1.7; lead 0.8-1.1; sulphur 0.8-0.9; copper 0.4-0.5, is carried out by washing with distilled water. According to the first option, washing is carried out under static conditions, with a solid to liquid ratio of 1:5 or 1:10 at a temperature of 20 °C with a holding time of 1 hour, the degree of chlorine removal is 90%. According to the second embodiment, washing is carried out under dynamic conditions, with stirring by a mechanical stirrer at a rotation speed of 400 rpm, with a solid to liquid ratio of 1:10, and a temperature of 20 °C with a holding time of 15 minutes, the degree of chlorine removal is 90%. In the temperature range from 20 to 60 °C with a holding time of 30 minutes, the purification rate is 99%.EFFECT: technology for removing chlorine from zinc-comprising material is simplified, and low-cost reagents are used.2 cl, 1 tbl, 2 ex

Description

[0001] The proposed invention relates to the production of zinc oxide and can be used to improve the quality of the zinc obtained during the disposal of electric arc furnace (EAF) dust.

[0002] This invention relates to zinc production, specifically to improving zinc purity, and can be used to recycle metallurgical waste, specifically electric arc furnace (EAF) dust. The invention enables the processing of EAF dust using the Waelz method to produce crude zinc oxide free of contaminants.

[0003] It is known that EAF dust is processed on a small scale using the Waelz process to extract zinc. However, the resulting zinc can be contaminated with impurities such as Cl, F, and Pb. These elements, when combined with zinc oxide, are difficult to remove. Therefore, a decision was made to pre-treat EAF dust before Waelz processing.

[0004] A method for removing chlorine and fluorine from dusty zinc-containing materials is known. Abdeev M.A., Kolesnikov A.V., Ushakov N.N. [Welz-Zinc-Lead-Containing Materials]. Moscow: Metallurgy. - 1985. - P.94]. The main essence of the method lies in oxidative roasting at a temperature of 650-700°C and processing of secondary sublimates. The main disadvantage of the method is the use of pyrometallurgical methods effective for removing chlorine; however, sublimation partially sublimes zinc and causes its loss.

[0005] A method for removing chlorine and fluorine from zinc-containing materials is known [SU 1135786, publ. Bulletin - 1985. - No. 3, C22B 7 / 02]. The essence of the method lies in the calcination of Waelz sublimates or slag sublimes, the capture of secondary sublimes and their two-stage washing with water-soda. The main disadvantage of this method is the use of an expensive two-stage pyrohydrometallurgical processing technology, which includes the use of a water-soda solution.

[0006] The closest patent in terms of technological essence and the achieved result is the Russian Federation patent "Method for removing chlorine and fluorine from dust-like zinc-containing materials" [RU 2317344 C1, C22B19 / 00, C22B7 / 02, filed 19.07.2006, published 20.02.2008]. The method includes calcining the materials to obtain sublimates containing chlorine and fluorine, and their leaching. In this case, leaching is carried out in a solution of sulfuric acid with the separation of the solid from the solution. Then, the solution is gradually purified from chlorine by precipitation with monovalent copper and from fluorine by precipitation with lime to obtain a fluorine-containing limecake. The cake is dried to a moisture content of 20-30% and then subjected to Waelz processing, which extracts zinc into Waelz oxide and converts fluorine and calcium into waste clinker. The main disadvantages of this method include the complex process chain and the use of expensive materials: monovalent copper and a water-soda solution.

[0007] The technical objective and result of the invention is the dechlorination of EAF dust by water washing with the selection of optimal parameters, which in turn allows obtaining “clean” EAF dust, ready for subsequent processing.

[0008] The technical task is achieved due to the fact that the EAF dust is subjected to water washing under various conditions, the main washing conditions can be considered: time, temperature, solid to liquid ratio, as well as dynamic mixing, it has been established that the transition of chlorine from EAF dust into solution reaches 98%, while preserving the main elements of zinc and iron in the dust.

[0009] The proposed method for dechlorinating EAF dust by water washing is as follows. Two variants of washing EAF dust with distilled water were conducted: one variant is characterized by water washing under static conditions; the second variant is characterized by water washing under dynamic conditions.

[0010] The technical result according to the first variant is achieved in that the method of dechlorinating zinc-containing dust of electric arc furnaces by water washing is characterized by the fact that the dust has the following chemical composition, mass%: iron 39.5-40.9; zinc 12.6-13.1; manganese 4.4-4.6; calcium 3.7-4.1; sodium 1.9-2.8; silicon 2.1-2.3; chlorine 1.7-2.0; potassium 1.6-1.7; lead 0.8-1.1; sulfur 0.8-0.9; Copper 0.4-0.5 is washed with distilled water under static conditions, with a solid to liquid ratio of 1:5 or 1:10 at a temperature of 20°C and a holding time of 1 hour, while the degree of purification from chlorine is 90%.

[0011] The technical result according to the second variant is achieved in that the method of dechlorinating zinc-containing dust of electric arc furnaces by water washing is characterized by the fact that the dust has the following chemical composition, mass%: iron 39.5-40.9; zinc 12.6-13.1; manganese 4.4-4.6; calcium 3.7-4.1; sodium 1.9-2.8; silicon 2.1-2.3; chlorine 1.7-2.0; potassium 1.6-1.7; lead 0.8-1.1; sulfur 0.8-0.9; Copper 0.4-0.5 is washed with distilled water under dynamic conditions, while stirring with a mechanical stirrer at a rotation speed of 400 rpm, at a solid to liquid ratio of 1:10, a temperature of 20°C and a holding time of 15 minutes, while the degree of purification from chlorine is 90%; and in the temperature range from 20 to 60°C and a holding time of 30 minutes, the degree of purification is 99%.

[0012] First variant. Zinc containing material (EDP dust) with the following chemical composition (dust composition is presented in wt.%): iron 39.5-40.9; zinc 12.6-13.1; manganese 4.4-4.6; calcium 3.7-4.1; sodium 1.9-2.8; silicon 2.1-2.3; chlorine 1.7-2.0; potassium 1.6-1.7; lead 0.8-1.1; sulfur 0.8-0.9; copper 0.4-0.5, was washed with distilled water under static conditions with a holding time of 1 to 72 hours; temperature ranges from 20 ° C to 80 ° C; The solid to liquid (s / l) ratio was varied among 1:1, 1:2, 1:5, 1:10, 1:15, and 1:20; washing was also carried out using recycled water. As a result of the experiments, the optimal conditions for static washing were selected, namely: holding time of 1 hour; temperature of 20°C; solid to liquid ratio of 1:10. Under these conditions, a decrease in chlorine in dust was observed from 2.0 wt.% to 0.2 wt.%, which corresponds to 90%.

[0013] Second option. Dynamic experiments on EAF dust dechlorination were conducted with continuous stirring of the solution on a mechanical stirrer at a rotation speed of 400 rpm. Based on previous studies on static washing with water, a decision was made to use a solid / liquid ratio of 1:10. The time interval for exposure to water varied from 10 minutes to 2 hours. The temperature range was from 20 to 80°C. When processing the experimental data, special attention should be paid to the results obtained with exposure times of 15 and 30 minutes and temperatures from 20 to 60°C. With these parameters, the maximum degree of dechlorination is observed (over 90% for 15 min and 20°C) up to complete removal of chlorine from EAF dust at a temperature of 60°C and a holding time of 30 minutes. An insignificant transition of zinc into the solution was detected.

[0014] The proposed method differs from the prototype in that it utilizes a simpler technology for removing chlorine from zinc-containing materials and uses inexpensive reagents. EAF dust is placed in a container and filled with water. The method can be implemented either with stirring or under static conditions. After washing, the dust is filtered and then dried.

[0015] The well-known method uses Waelz oxide to remove chlorine and fluorine, which significantly increases the cost of the process due to the inclusion of zinc-containing dust. The Waelz oxide is then processed using hydrometallurgical methods, which requires expensive reagents.

[0016] In the claimed method, dechlorination of zinc-containing dust is carried out with distilled water, which significantly simplifies the process and makes it cheaper.

[0017] Example 1. Selecting the optimal parameters for static washing. To determine the holding time in an aqueous solution, 50 g of the original dust of the following chemical composition were taken (dust composition is presented in wt.%): iron 39.5-40.9; zinc 12.6-13.1; manganese 4.4-4.6; calcium 3.7-4.1; sodium 1.9-2.8; silicon 2.1-2.3; chlorine 1.7-2.0; potassium 1.6-1.7; lead 0.8-1.1; sulfur 0.8-0.9; copper 0.4-0.5, 500 ml of water were poured into different containers); the solid to liquid ratio was 1:10. Then the mixture was kept for a certain time from 1 hour to 72 hours at room temperature. To determine the solid-to-liquid ratio, the mixture was held at room temperature for an equal amount of time, followed by a holding time of 1 hour. The following ratios were selected for the experiments: 1:1; 1:2; 1:5; 1:15; 1:20. After the holding time, the solution was drained and the sample was dried. To determine the optimal temperature, a sample of the original dust was heated in a drying oven with water. The experiments were conducted at temperatures of 20, 40, 60, and 80°C.Each sample was mixed in a container at a ratio of 1:10 (in separate flasks) with a holding time of 1 hour. For the repeated water rinsing experiments, the wastewater from the experiments was used; the holding time was 1 hour, the temperature was 20°C, and the ratio was 1:10. After the holding time, the solution was drained, and the sample was dried. The concentrations of chlorides and other elements in the solution were determined. The residue after rinsing was dried and examined under an electron microscope.

[0018] Static experiments with short time intervals (less than 1 hour) were not conducted. However, with washing times ranging from 1 hour to 72 hours, it was found that the transfer of chlorine from EAF dust into the aqueous solution depends only slightly on the holding time. During the experiments, the degree of dechlorination of EAF dust was approximately 90%, and the average chloride ion content in the solution was 2.9 mg / L. In subsequent experiments, a holding time of 1 hour was used. No zinc transfer into the aqueous solution was observed.

[0019] As a result of the experiments, it was found that the optimal solid to liquid ratio is 1:5 and 1:10, which is associated with the convenience of conducting experiments and the greatest reliability.

[0020] The experimental results revealed no zinc loss, and the degree of dechlorination also reached 90%. Similar transitions of the studied elements were observed at different solid-to-liquid ratios. Subsequent experiments were conducted at a ratio of 1:10 due to ease of implementation.

[0021] As a result of experiments to study the effect of temperature, the following was established: the transfer of chlorine occurs in full, regardless of temperature; the content of other elements remains at the same level.

[0022] Example 2. Selecting optimal parameters for dynamic mixing. A JOANLAB OS-15S overhead stirrer with a rotation speed of 100 to 1500 rpm was used for mixing. A UH-3030D heating plate with an operating temperature of ±10 to 350°C was used for heating. Based on previous studies on static water flushing, a solid / liquid ratio of 1:10 was used. The soak time in water varied from 10 minutes to 2 hours. The temperature range was from 20 to 80°C. Stirring was carried out at a constant speed of 400 rpm.

[0023] Dust dynamic mixing experiments revealed the following: chlorine (up to 90%) transfers into water at both maximum and minimum exposure times. Mixing significantly increases the rate of transfer of elements from dust to water.

[0024] When processing the experimental data, the results obtained with holding times of 15 and 30 minutes and temperatures from 20 to 60°C are particularly noteworthy. Under these parameters, the maximum degree of dechlorination is observed (over 90% for 15 minutes and 20°C), with complete removal of chlorine from EAF dust occurring at temperatures from 20 to 60°C and a holding time of 30 minutes. A slight release of zinc into solution was observed.

[0025] Table 1 shows the results for a holding time of 30 min and a temperature range from 20°C to 60°C; in this time and temperature range, the maximum transfer of chlorine from EAF dust into solution is observed.

[0026] Table 1. Results of chemical analysis of washed EDP dust on an electron microscope at different holding times and temperatures, stirring, mass%

[0027] °C Min O Mg Al Si Cl K Ca Cr Mn Fe Cu Zn Pb Result 20°C - 15 19,13 1,34 0,16 2,21 0,19 - 4,5 0,49 5,99 49,25 0,66 15,32 0,77 100 40°C - 15 15,7 1,07 0,58 3,23 0,05 0,44 3,92 0,73 5,58 50,59 0,58 16,74 0,79 100 60°C - 15 19,18 1,19 0,31 3,03 0,11 0,37 4,12 0,57 5,57 48,47 0,27 15,60 1,39 100 80°C - 15 16,42 1,45 0,44 2,84 0,18 0,48 4,27 0,42 5,62 51,5 0,25 15,24 0,89 100 20°С - 30 15,59 1,64 0,71 3,53 0,01 0,25 4,97 0,53 5,51 51,77 0,68 14,46 0,73 100 40°С - 30 17,59 1,42 0,63 2,72 0,01 0,45 4,05 0,51 5,37 51,09 0,40 14,85 0,94 100 60°С - 30 18,05 1,54 0,43 2,93 0,00 0,47 4,48 0,44 5,79 48,88 0,88 15,43 0,71 100 80°C - 30 18,94 1,55 2,8 0,21 0,31 - 4,54 0,71 5,26 49,44 0,84 14,55 0,84 100 20°C - 60 18,61 1,1 0,77 3,46 0,17 0,36 3,93 0,44 5,45 48,34 0,73 15,35 1,28 100 40°С - 60 17,38 1,56 0,23 2,79 0,22 0,44 5,22 0,65 5,27 49,71 0,83 15,45 0,40 100 60°С - 60 18,46 1,38 0,55 2,98 0,14 0,4 5,78 0,49 5,1 48,49 0,96 13,89 1,38 100 80°С - 60 19,82 1,38 0,14 3,23 0,35 0,55 4,3 0,77 5,5 47,9 0,74 14,5 0,83 100

[0028] Thus, the technical result has been achieved, namely, dechlorination of EAF dust by static and dynamic washing with water.

Claims

1. A method for dechlorinating zinc-containing dust from electric arc furnaces by water washing, characterized in that the dust of the chemical composition, wt.%: iron 39.5-40.9; zinc 12.6-13.1; manganese 4.4-4.6; calcium 3.7-4.1; sodium 1.9-2.8; silicon 2.1-2.3; chlorine 1.7-2.0; potassium 1.6-1.7; lead 0.8-1.1; sulfur 0.8-0.9; copper 0.4-0.5 is washed with distilled water under static conditions, at a solid to liquid ratio of 1:5 or 1:10 at a temperature of 20°C and a holding time of 1 hour, wherein the degree of purification from chlorine is 90%.

2. A method for dechlorinating zinc-containing dust from electric arc furnaces by water washing, characterized in that the dust has the following chemical composition, wt.%: iron 39.5-40.9; zinc 12.6-13.1; manganese 4.4-4.6; calcium 3.7-4.1; sodium 1.9-2.8; silicon 2.1-2.3; chlorine 1.7-2.0; potassium 1.6-1.7; lead 0.8-1.1; sulfur 0.8-0.9; Copper 0.4-0.5 is washed with distilled water under dynamic conditions, while stirring with a mechanical stirrer at a rotation speed of 400 rpm, at a solid to liquid ratio of 1:10, a temperature of 20°C and a holding time of 15 minutes, while the degree of purification from chlorine is 90%; and in the temperature range from 20 to 60°C and a holding time of 30 minutes, the degree of purification is 99%.