AU2006346015A1

AU2006346015A1 - A floatation process for desulfurization and desiliconization of bauxites

Info

Publication number: AU2006346015A1
Application number: AU2006346015A
Authority: AU
Inventors: Xiangqing Chen; Zhiyou Chen; Wangxing Li; Junwei Ma; Xiangbin Xu; Weizhen Yan; Zhonglin Yin
Original assignee: Aluminum Corp of China Ltd
Current assignee: Aluminum Corp of China Ltd
Priority date: 2006-07-06
Filing date: 2006-12-06
Publication date: 2008-01-17
Anticipated expiration: 2026-12-06
Also published as: RU2422212C2; WO2008006264A1; AU2006346015B2; CN100398216C; RU2009100061A; CN1868599A

Description

UfC n6rvP AM44. CERTIFICATE OF VERIFICATION 1, ZHOU, Tie Of China Patent Agent (H.K.) Ltd. state that the attached document is a true and complete translation to the best of my knowledge of International Patent Application No. PCT/CN200O603314. Dated this day of 2008 Signature of Translator - WO 2008/006264 A Flotation Process for Desulfurization and Desiliconization of Bauxites Technical Field 5 The present invention relates to a flotation process for desulfurization and desiliconization of bauxites, which concerns a process for flotation of bauxites, especially a process for desulfurization and desiliconization of low-grade bauxite ores containing sulfur. 10 Background of the Invention Bauxites are a major raw material in aluminum industry, and also an essential raw material for preparing refractory materials, high performance abrasive materials, high alumina cement, ceramics, chemicals and medicines. If a bauxite ore contains is sulfur, either in a high or low content, it will have great impacts on the process stability in the production of alumina by the Bayer process. Sulfides in bauxites are primarily pyrite, isomeric marcasite and greigite. Pyrite starts to react with an alkaline liquor at 180*C, while marcasite and greigite are more easily decomposed by the alkaline liquor to produce S2, SO3, S0 4 2 -, S 2 2 -, and S 2

S

3 2 -, which results in 20 loss of NaOH. In addition, S2- and SO 4 - act as the dispersant so that iron is dissolved in a colloidal form, which affects the settling performance of the red mud and results in turbidity of the overflow. Meanwhile, the steel products are significantly eroded by S2. in the solution so that the apparatus is prone to damages. The sintering process for producing alumina suffers from high energy consumption and high cost 25 on one hand, and has a serious impact on the environment and the apparatus on the other hand. Thus, high-sulfur containing bauxites must be desulfurized so as to fulfill the eligible requirements before they can be used for economical production of alumina by the Bayer process. 30 In the current processes for desulfurization and desiliconization of sulfur-containing bauxites, a primary fine-grinding process (with a grinding fineness of about 90% -0.074mm) is used. In the cases wherein the pH value is from 9 to 10, a high amount WO 2008/006264 (3333 g/ton of crude ore) of alkyl dithiocarbonate is used as the collector for in the reverse flotation for desulfurization. Then, sodium dodecyl sulfate is used as the auxiliary collector for the salts of the fatty acids in the flotation for desiliconization. The alumina recovery is higher than 80%. It can be seen that the amount of the 5 flotation agent used in the current processes is relatively high, and the alumina recovery is low. Thus, it is of big interest to develop a novel flotation agent and a new flotation process for desulfurization and desiliconization of such kind of bauxites. 1o Contents of the invention The object of the present invention is to overcome the shortcomings in the aforesaid prior art, such as the poor dispersibility and high specific surface area of the ore slurry after the primary fine grinding, high flotation agent consumption, and weak 15 performance of the collector. The object is achieved by providing a high efficient flotation process for desulfurization and desiliconization of sulfur-containing bauxites having a low Al/Si ratio, which can effectively reduce the amount of the flotation agent, ensure the quality of the flotation concentrates and improve the flotation process parameters. 20 The present invention provides a flotation process for desulfurization and desiliconization of bauxites, characterized in that a reverse flotation process for desulfurization and a normal flotation process for desiliconization are performed sequentially, wherein the mid-low grade bauxites containing sulfur are subjected to 25 the reverse flotation for desulfurization after a primary grinding and the desulfurized middlings are subjected to the normal flotation for desiliconization after a stage regrinding. The flotation process for desulfurization and desiliconization of bauxites according 30 to the present invention is further characterized in that the reverse flotation for desulfurization comprises subjecting the bauxites to a primary grinding to obtain a fineness of 60%-85% -0.074mm and then bringing the ore slurry into action with a 2 WO 2008/006264 flotation agent to perform the reverse flotation for desulfurization and obtain sulfides tailings and bauxite middlings in the cell, wherein ethyl xanthate (sodium ethylxanthate) or ethyl thio carbamate (sodium diethyldithiocarbamate) in an amount of 100-500 g/ton of ore is used as the collector, copper sulphate in an 5 amount of 50-500 g/ton of ore is used as the conditioning agent, the so-called Frother 2 (a mixture of pine camphor oils, primarily c-terpineol (the content thereof being higher than 82%), produced by Luchang Trading Co., Ltd, Qingdao, China), in an amount of 20-150 g/ton of ore is used as the frothing agent. 1o The flotation process for desulfurization and desiliconization of bauxites according to the present invention is further characterized in that the normal flotation for desiliconization comprises subjecting the desulfurized bauxite middlings in the cell to a secondary grinding to obtain a fineness of 75%-92% -0.074mm and then bringing the slurry into action with a flotation agent for desiliconization of bauxites 15 by normal flotation to perform the normal flotation for desiliconization and produce the froth bauxite concentrates, wherein a saponified naphthenic acid and a fatty acid compounded in a ratio of 1:5-200 are used as the collector in an amount of 700-1600 g/ton of ore, sodium carbonate in an amount of 2000-5000 g/ton of ore is used to adjust the pH value, sodium hexametaphosphate in an amount of 50-200 g/ton of ore 20 is used as the conditioning agent. The flotation process for desulfurization and desiliconization of bauxites according to the present invention is further characterized in that the reverse flotation for desulfurization comprises one or two times of roughing, scavenging and cleaning. 25 The flotation process for desulfurization and desiliconization of bauxites according to the present invention is further characterized in that the normal flotation for desiliconization comprises one or two times of roughing, scavenging and cleaning. 30 The process according to the present invention comprises the reverse flotation for desulfurization by using a primary grinding process and the flotation for desiliconization after a stage grinding. Meanwhile, the process further comprises the 3 WO 2008/006264 flotation agent used therein. The flotation agents used in the process according to the present invention are an effective collector - ethyl xanthate which is selected and can be suitably used for 5 desulfurization of sulfur-containing bauxites, combined with the conditioning agent - copper sulphate; and a high efficient compounded collector for desiliconization of bauxites by normal flotation, which is developed by compounding a saponified fatty acid with a naphthenic acid in a certain ratio. 10 The naphthenic acids used in the present invention comprise all the naphthenic acids commonly used by those skilled in the art, and mixtures thereof, preferably, carboxylic acids of C 5 -cycloalkanes having the following formula or derivatives thereof, or mixtures thereof,

H

2 - CH 15 R -CH

CH

2 - CH - (CR 2 ) H n -COOH wherein n is an integer ranging from 0-5; R is a saturated or unsaturated, linear or branched CI-Cl 0 aliphatic hydrocarbyl. 20 The fatty acids in the present invention are all the fatty acids commonly used by those skilled in the art, or mixtures thereof, e.g., C 8

-C

20 saturated fatty acids or mixtures thereof, unsaturated fatty acids such as oleic acid, linoleic acid, linolenic acid, elaeostearic acid or mixtures thereof, and such as one or more selected from 25 bean oil acid, cotton oil acid, tea oil fatty acid, linseed oil acid and tung oil fatty acid. The flow of the process according to the present invention is designed based on the nature of the ores to involve desulfurization with rough grinding, desiliconization 30 with fine grinding and the respective flotation. First, after a primary rough grinding, the agent for desulfurization by reverse flotation is added for the flotation of 4 WO 2008/006264 bauxites for desulfurization. Then the process and agent for a normal flotation for desiliconization are used for the stage desiliconization after a stage fine grinding so as to improve the quality of bauxites and fulfill the requirements on the production of alumina by the Bayer process, and to widen the resources of bauxites. On the 5 other hand, the amount of the flotation agent can be further reduced by developing a high efficient collector. The production and economic indexes can thus be improved. The flotation process with rough grinding is suitable for desulfurization of sulfides due to the coarse dissemination size thereof. The desulfurization process with rough 1o grinding used in the present invention decreases the energy consumption in the grinding, greatly reduces the amount of the collector for sulfides, and reduces the interference of the flotation agent on the further flotation for desiliconization. High efficient desulfurization is achieved by the selected high effective collectors. Due to the fine dissemination size of the silicate gangue, fine grinding is required for the 15 ores so as to allow the grain liberation to take place. Then, flotation for desiliconization is conducted by using a high efficient flotation agent. The use of the developed high efficient collectors for the normal flotation enhances the collection of diasporite minerals and the flotation separation thereof from the silicate gangue. 20 The present invention uses the stage grinding process so that sulfides with coarse dissemination size are separated preferentially by flotation and are then subjected to fine grinding for desiliconization, which is advanced and stable in the process. Under the action of the high efficient flotation agent for sulfides and the advanced flotation agent for desiliconization of bauxites, good production and economic 25 indexes are achieved. Better effects of staged desulfurization and desiliconization are achieved for the sulfur-containing bauxite crude ore of diasporite type containing 0.5-5% S, 55-72% A1 2 0 3 and 2-19% SiO 2 and having a low Al/Si ratio. Bauxite concentrates having an Al/Si ratio of 7-15 are obtained, which concentrates can be directly used for the production of alumina by the Bayer process and thus bring 30 about notable economic benefits. The process of the present invention is suitable for flotation desulfurization and 5 WO 2008/006264 desiliconization of sulfur-containing low grade bauxites. For bauxites having a high Al/Si ratio, it is possible to only use the preceding primary process for desulfurization. For the sulfur-containing low grade bauxites, the secondary desiliconization process is conducted after the primary desulfurization is completed. 5 The process of the present invention has a broad prospect of application. Mode of carrying out the invention The present invention provides a flotation process for desulfurization and 1o desiliconization of bauxites in which a reverse flotation process for desulfurization and a normal flotation process for desiliconization are performed sequentially. The sulfur-containing mid-low grade bauxites are subjected to the reverse flotation for desulfurization after a primary grinding and then subjected to the normal flotation for desiliconization after a stage regrinding. The reverse flotation for desulfurization 15 comprises subjecting the bauxites to the primary grinding to obtain a fineness of 60%-85% -0.074mm and then bringing the ore slurry into action with the flotation agent to perform the reverse flotation for desulfurization and obtain sulfide tailings and bauxite middlings in the cell, wherein ethyl xanthate or ethyl thio carbamate in an amount of 100-500 g/ton of ore is used as the collector, copper sulphate in an 2o amount of 50-500 g/ton of ore is used as the conditioning agent, the Frother 2 in an amount of 20-150 g/ton of ore is used as the frothing agent. The normal flotation for desiliconization comprises subjecting the desulfurized bauxite middlings in the cell to the secondary grinding to obtain a fineness of 75%-92% -0.074mm and then bringing the ore slurry into action with the normal flotation agent for 25 desiliconization of bauxites to perform the normal flotation for desiliconization and produce the froth bauxite concentrates, wherein a saponified naphthenic acid and a fatty acid compounded in a ratio of 1:5-200 are used as the collector in an amount of 700-1600 g/ton of ore, sodium carbonate in an amount of 2000-5000 g/ton of ore is used to adjust the pH value, sodium hexametaphosphate in an amount of 50-200 30 g/ton of orei s used as the conditioning agent. Further explanations are provided below in combination with specific examples. 6 WO 2008/006264 Example 1 The specific flotation processes for desulfurization and desiliconization of the crude 5 bauxites from the area of Chuandongwan-Huihe, Nanchuan, which comprise 59.74% of A1 2 0 3 , 11.39% of Si0 2 , and 1.73% of sulfur and have an Al/Si ratio of 5.24, were provided as follows. a) Primary desulfurization process l0 The bauxites were ground by using a ball mill. Sodium carbonate in an amount of 4200 g/ton of crude ore was added into the ball mill. 75% of the ground product had a fineness of -0.074mm, and the overflow concentration of the classifier was 38%. Copper sulphate as the activating agent in an amount of 140 g/ton, the collector in an 15 amount of 240 g/ton, and Frother 2 as the frothing agent in an amount of 80 g/ton were added to the ground slurry in a stirring tank. After sufficient stirring, the mixture was fed into a flotation machine to perform reverse flotation for desulfurization, wherein the slurry concentration for flotation ranged from 14-37% and the pH value of the slurry was maintained at about 8.1. With a closed flow of 20 one roughing, one cleaning, and middlings recycling in order, the flotation froth sulfur concentrates were produced. b) Stage desiliconization process 25 The desulfurized concentrates were subjected to the secondary grinding so that the grinding fineness is 86%. The pH value of the slurry was adjusted to 9.5. A collector formed by compounding the naphthenic acids (refined naphthenic acids produced by Intercontinental Vast Fine Chemical industry Co., Ltd, Boluo, Guangdong, China, primarily containing carboxylic acids of C 5 -naphthene and derivatives thereof, and 30 further comprising a small amount of carboxylic acids of C 3 -, C 4 - and C 6 -naphthene and derivatives thereof, the total amount of naphthnic acids being about 90%) with oleic acid in a ratio of 1:15 was added in an amount of 1160 g/ton, and sodium 7 WO 2008/006264 hexametaphosphate as the conditioning agent was added in an amount of 60 g/ton. The roughing and concentrating concentrations ranged from 18-32%; the scavenging concentration was 7-15%. After a closed flotation flow of one roughing, two cleanings, one scavenging and middlings recycling in order, qualified bauxite 5 concentrates and a small amount of bauxite tailing products were obtained. The beneficiation indexes obtained by using said process can be found in Table 1. Tale 1 Beneficiation indexes obtained by using the above process Collector for Primary Product name A1 2 0 3 % Si0 2 % Al/Si S% Yield% Recovery% desulfurization crude ore 59.74 11.39 5.24 1.73 100.00 100.00 sulfur concentrate 24.15 5.94 4.07 29.94 5.13 2.07 ethyl xanthate Aluminum 66.91 6.45 10.37 0.18 76.26 85.41 concentrate aluminum tailings 40.16 33.13 1.21 0.31 18.61 12.51 crude ore 59.74 11.39 5.24 1.73 100.00 100.00 sulfur concentrate 25.36 5.94 4.27 28.16 5.13 2.18 ethyl thio carbamate aluminum 66.86 6.74 9.92 0.29 74.58 83.47 concentrate aluminum tailings 42.25 29.85 1.42 0.35 20.29 14.35 10 Example 2 Only the following primary desulfurization process was performed for a high-sulfur and high Al/Si ratio bauxite ore in Nanchuan. 15 Bauxites were ground by using a ball mill. Sodium carbonate in an amount of 4200 g/ton of crude ore was added into the ball mill. 72% of the ground product had a fineness of -0.074m. The overflow concentration of the classifier was 39.25%. Copper sulphate as the activating agent in an amount of 120 g/ton, ethyl xanthate as 8 WO 2008/006264 the collector in an amount of 260 g/ton, and Frother 2 as the frothing agent in an amount of 80 g/ton were added to the ground slurry in a stirring tank. After sufficient stirring, the mixture was fed into a flotation machine to perform reverse flotation for desulfurization, wherein the slurry concentration for flotation ranged 5 from 14-37% and the pH value of the slurry was maintained at about 8.1. After a closed flow of one roughing, two cleanings, one scavenging, and middlings recycling in order, flotation froth sulfur concentrates and bauxite concentrates in the cell were produced. The beneficiation indexes can be found in Table 2. 10 Tale 2 Beneficiation indexes obtained by using ethyl xanthate as collector Product name Yield% A1 2 0 3 % Sio 2 % Al/Si S% A1 2 0 3 recovery% S recovery% aluminum concentrate 90.70 71.21 7.3 9.75 0.36 97.68 8.82 sulfur concentrate 9.30 16.52 2.32 8.5 36.4 2.32 91.18 crude ore 100.00 66.12 6.84 9.67 3.7 100.00 100.00 9

Claims

1. A flotation process for desulfurization and desiliconization of bauxites, characterized in that said process comprises a reverse flotation for desulfurization 5 and a normal flotation for desiliconization, wherein the sulfur-containing mid-low grade bauxites are subjected to the reverse flotation for desulfurization after the primary grinding and then to the normal flotation for desiliconization after a stage regrinding.

2. The process according to claim 1, characterized in that the reverse flotation 1o for desulfurization comprises subjecting the bauxites to the primary grinding to obtain a fineness of 60%-85% -0.074mm and then bringing the ore slurry into action with the flotation agent to perform the reverse flotation for desulfurization and obtain sulfide tailings and bauxite middlings in the cell, wherein ethyl xanthate or ethyl thio carbamate in an amount of 100-500 g/ton of ore is used as the collector, 15 copper sulphate in an amount of 50-500 g/ton of ore is used as the conditioning agent, Frother 2 in an amount of 20-150 g/ton of ore is used as the frothing agent.

3. The process according to claim 1, characterized in that the normal flotation for desiliconization comprises subjecting the desulfurized bauxite middlings in the cell to a secondary grinding to obtain a fineness of 75%-92% -0.074mm and then 20 bringing the ore slurry into action with the normal flotation agent for desiliconization of bauxites to perform the normal flotation for desiliconization and produce the froth bauxite concentrates, wherein a saponified naphthenic acid and a fatty acid compounded in a ratio of 1:5-200 are used as the collector in an amount of

700-1600 g/ton of ore, sodium carbonate in an amount of 2000-5000 g/ton of ore is 25 used to adjust the pH value, sodium hexametaphosphate in an amount of 50-200 g/ton of ore is used as the conditioning agent. 4. The process according to claim 3, characterized in that said naphthenic acid is a carboxylic acid of a C 5 -cycloalkane having the following formula or a derivative thereof, or a mixture thereof, 30 10 WO 2008/006264 H2 -CH 2 R-CH CH 2 - CH - (CH2) n -- COOH 5 wherein n is an integer ranging from 0-5; R is a saturated or unsaturated, linear or branched CI-C 1 0 aliphatic hydrocarbyl. 5. The process according to claim 3, characterized in that said fatty acid is a saturated C 8 -C 20 fatty acid or a mixture thereof. 6. The process according to claim 3, characterized in that said fatty acid is 1o selected from the group consisting of oleic acid, linoleic acid, linolenic acid, elaeostearic acid and a mixture thereof. 7. The process according to claim 3, characterized in that said fatty acid is oleic acid. 8. The process according to claim 3, characterized in that said fatty acid is one is or more selected from the group consisting of bean oil acid, cotton oil acid, tea oil fatty acid, linseed oil acid and tung oil fatty acid. 9. The process according to claim 1 or 2, characterized in that the reverse flotation for desulfurization comprises one or two times of roughing, scavenging, and cleaning. 20 10. The process according to claim 1 or any one of claims 3-8, characterized in that the normal flotation for desiliconization comprises one or two times of roughing, scavenging, and cleaning. I1