Resource treatment method of red mud

Abstract

The invention discloses a resource treatment method of red mud, the method comprises the steps of ingredient mixing, heating mineralization, solid-liquid separation, magnetic separation and the like, by using the method, iron and aluminum in the red mud can be extracted, alkali in the red mud can be removed, and red mud reduction and resource utilization are realized.

Description

Technical Field

[0001] The invention belongs to the field of "chemistry and metallurgy", in particular to the field of resource recycling and environmental protection, and particularly to a comprehensive utilization of red mud solid waste. Background Art

[0002] Red mud is the main solid waste discharged during the production of alumina. It is a strongly alkaline, reddish, muddy waste. Due to its variable composition and complex phase, the resource management of red mud has been a global problem since the last century and has attracted much attention from the industry.

[0003] Future research on the utilization of red mud should focus on reducing the stock, reducing the incremental volume, and utilizing all components of red mud on a large scale, supplemented by developing high value-added functional materials, implementing multi-channel and diversified waste-free comprehensive utilization, and improving resource utilization.

[0004] In order to alleviate the shortage of iron ore resources in my country and the red mud discharge pressure of the alumina industry, the method of the present invention uses liquid phase mineralization technology to treat red mud, and this technology can be used to comprehensively recover iron, aluminum and alkali metals in red mud. While mineralizing iron oxide, the residual alkali in the red mud is used to dissolve aluminum, and then the aluminum-containing mother liquor is separated by solid-liquid separation and the iron oxide is separated by magnetic separation. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the shortcomings of existing red mud management and comprehensive utilization, the present invention provides a red mud resource management method, that is, using liquid phase mineralization technology, which can achieve the purpose of resource management while realizing red mud reduction.

[0007] (II) Technical solution

[0008] To achieve the above purpose, the liquid phase mineralization technology adopted by the present invention is: after mixing red mud with mineralizer, regulator and crystal nucleating agent, the iron in the red mud is mineralized into Fe 3 O 4 and form crystals, while utilizing the residual alkali (R 2 O=K 2 O+Na 2 O) and regulator leaching Al in red mud 2 O 3 , the method comprises the following steps:

[0009] (1) Mixing ingredients: Mix the original red mud with mineralizer, regulator, crystal nucleating agent, etc. and water in a set ratio to form a slurry.

[0010] (2) Heating mineralization: Add the slurry into a closed reaction vessel, stir and heat to a set temperature, and keep the temperature to react for a predetermined time.

[0011] (3) Solid-liquid separation: The slurry after the reaction is separated into solid and liquid and washed by dehydration equipment to obtain mother liquor and filter cake.

[0012] (4) Magnetic separation: Add the filter cake into a blender, add clean water, stir and disperse, and then use wet magnetic separation to separate the iron ore and secondary red mud.

[0013] The above method adopts liquid phase mineralization technology, which can simultaneously realize the mineralization of iron in red mud, the growth of Fe3O4 crystals and the leaching of Al2O3, which is convenient for subsequent separation and resource utilization.

[0014] Attached Figure 1 This is the process flow chart of liquid phase mineralization technology.

[0015] Preferably, the set ratio in step (1) is: the ratio of red mud (dry basis), mineralizer, regulator, crystal nucleating agent and water is 100: (2-10): (1-20): (0-20): (200-800). A more preferred ratio is 100: (4-10): (4-12): (3-15): (300-600).

[0016] Preferably, the red mud in step (1) is Bayer process red mud, sintering process red mud, or combined process red mud, more preferably Bayer process red mud.

[0017] Preferably, the mineralizer in step (1) is any crushed biomass, such as plant branches, leaves, roots, seeds and mixtures thereof, plant processing products such as starch, dextrin, sucrose, protein, residues (dregs, dregs, bran, bran, crumbs, etc.) and animal feces. Although these biomass materials can be used as mineralizers in the method of the present invention, for the sake of breadth and economy, the more preferred scheme is starch and by-product residues of plant processing.

[0018] Preferably, the regulator in step (1) is a siliceous material (quartz powder, silicon dioxide, etc.) or sodium hydroxide, calcium oxide or calcium hydroxide, calcined dolomite, etc. The inventors believe that, for the consideration of subsequent red mud construction materials, it is not appropriate to use magnesium-containing raw materials as the regulator; for the consideration of red mud dealkalization, a more preferred solution is quartz powder or lime powder.

[0019] The inventors have found that the sodium silicate slag known in the alumina industry is mainly a compound of sodium silicate and sodium aluminate or calcium aluminate. As long as a suitable regulator is selected, the CaO and SiO in the slurry can be 2 The molecular ratio of is 0.9-1.1, which can transform sodium silicate and calcium aluminate into calcium silicate, and can make sodium oxide and aluminum oxide form sodium aluminate and enter the liquid phase to achieve the purpose of extraction.

[0020] Preferably, the nucleating agent in step (1) is magnetite, and more preferably, it is the iron ore concentrate obtained by magnetic separation in step (4).

[0021] Preferably, step (1) includes using water. The water quality of the water should not be lower than the requirements of Class IV in the "Surface Water Environmental Quality Standard" (GB3838-2002), such as surface water, groundwater, industrial water, drinking water, etc., and can also be recycled water or condensed water; more preferably, the washing water of step (3) is used.

[0022] Preferably, the heating mineralization in step (2) is to add the slurry into a closed reaction container, keep the slurry in a moving state and heat it to a set temperature for a predetermined time. The thermal system is: using chemical heat and physical heat, the slurry is heated to above 150°C and kept at a constant temperature for more than 30 minutes.

[0023] The mineralizer described in the present invention is a biomass raw material. The physical and chemical properties of biomass are relatively stable and generally insoluble in water and common organic solvents. However, under the combined action of alkalinity, heating, pressure and metal ions, biomass can react with water, and the oxygen bridges of starch, protein, cellulose and lignin in the biomass are broken. At the same time, water molecules are added, and the biomass changes from long-chain molecules to short-chain molecules, and the oxygen bridges are broken to form reducing substances. Reaction temperature, time, alkali dosage and metal ions all have a certain influence on the alkaline degradation of biomass. Rising temperature, increased pressure and increased alkali dosage will increase the degradation rate of biomass. In addition, Ca in red mud 2+ , Fe 3+ 、Al 3+ Mg 2+ The presence of etc. will accelerate the reaction process, and these conditions are exactly what is needed to mineralize iron in red mud and leaching aluminum in red mud.

[0024] Modern research on supercritical water gasification of biomass (such as Mao Taoxiu, Tian Senlin, etc.: "Research Progress on the Principle of Supercritical Water Gasification of Cellulose and Lignin", "New Chemical Materials", Vol. 43, No. 7, July 2015) shows that the biomass gasification process is reforming, water-gas shift and methanogenesis, see equations (1), (2), (3) and (4), respectively.

[0025] CH n O m +(1-m)H2O→(n / 2+1-m)H 2 +CO (1)

[0026] CO+H 2 O→CO 2 +H 2 (2)

[0027] CO+3H 2 →CH 4+H 2 O (3)

[0028] CO 2 +4H 2 →CH 4 +2H 2 O (4)

[0029] These new gasification products (CO, H 2 , CH 4 etc.) are all reductive. For example, hydrogen atoms, under the catalytic action of alkali, can reduce the goethite in red mud and Fe in hematite. 3+ Partially converted to Fe 2+ And form magnetite crystals.

[0030] Fe 3+ +H·+OH-→Fe 2+ +H 2 O (5)

[0031] Preferably, the slurry movement state in step (2) is stirring the slurry or making the slurry flow.

[0032] Preferably, the set temperature in step (2) is to heat and keep the slurry at 150°C or above; more preferably, 200°C to 400°C; and more preferably, 250 to 300°C.

[0033] Preferably, the predetermined time in step (2) is to heat the slurry to the set temperature and then keep the temperature constant (insulated) for more than 30 minutes; more preferably, it is 60 to 180 minutes; and more preferably, it is 80 to 120 minutes.

[0034] Preferably, the solid-liquid separation in step (3) further comprises washing, in which the slurry after the reaction is separated into mother liquor and filter cake by a dehydration device, in order to wash out the alkali (K 2 O+Na 2 O) and extract the aluminum oxide therein, and can be washed with clean water more than twice. The dehydration equipment may include an applicable centrifugal dehydrator, a belt dehydrator, a vacuum dehydrator, a plate and frame filter press, etc. Those skilled in the art can implement this step by using well-known solid-liquid separation and washing techniques and equipment. The present invention does not make claims and limitations to this, nor does it provide embodiments.

[0035] Preferably, the magnetic separation in step (4) is to add the filter cake into a mixer, add clean water, stir and disperse, and then use a wet magnetic separator to separate the iron ore and secondary red mud. More preferably, in step (4), the wet magnetic separator is a wet permanent magnetic drum magnetic separator, more preferably a double drum wet magnetic separator.

[0036] Preferably, in step (4), the iron concentrate has a magnetite content greater than 70%, and other technical indicators and quality indicators are as shown in Table 1.

[0037] Table 1 Technical quality indicators of iron ore concentrate

[0038] Element TFe <![CDATA[SiO 2 ]]> S P index ≥67％ ≤4.6％ ≤0.15％ ≤0.09％

[0039] Preferably, in step (4), the secondary red mud is alkali (R 2 O=K 2 O+Na 2 O) content is less than 1%.

[0040] The inventors have found that after the reaction and separation in the above steps, secondary red mud is easier to filter than original red mud, has lower alkali and iron content, and is more suitable for building material applications and extraction of valuable metals. Furthermore, the incompletely hydrolyzed biomass in secondary red mud can increase the calorific value of raw materials in the cement industry, increase the plasticity of raw materials and reduce the degree of frost in the production of shaped building materials, and increase the entropy retention capacity of soil in soil utilization.

[0041] Most preferably, a method for resource recovery of red mud, a feasible technical solution comprises the following steps:

[0042] (1) The mass ratio is red mud (dry basis): mineralizer: regulator: crystal nucleating agent: water = 100: (4-10): (4-12): (3-15): (300-600);

[0043] (2) adding raw materials into a reaction vessel and stirring to form a slurry;

[0044] (3) In a closed reaction vessel, the slurry is heated to 250-300° C. with continuous stirring at a speed of 250-350 rpm, and the pressure is increased and the temperature is kept constant for reaction for 60-120 min.

[0045] (4) releasing the slurry after the reaction and filtering it with a spiral centrifuge while it is still hot; filtering out the mother liquor and returning it to the alumina process;

[0046] (5) The filtered cake is then washed with hot water above 50°C and filtered twice. The washing water can be used in step (1).

[0047] (6) The washed filter cake is added to a mixer together with clean water, stirred and dispersed, and then separated by a double-drum wet magnetic separator into iron concentrate and secondary red mud. DETAILED DESCRIPTION

[0048] The present invention is further described in detail below with reference to examples.

[0049] The purpose of the present invention is to provide a method for resource management of red mud. The method of the present invention uses solid waste red mud produced by the alumina industry as the basic raw material, and is a method for resource management and comprehensive utilization of red mud with a short process, simple method and simple investment. The method can be used to extract metal resources such as iron, sodium and aluminum from red mud.

[0050] The red mud resource treatment method of the present invention comprises the following raw materials: red mud, a mineralizer, a regulator, a crystal nucleating agent and water.

[0051] According to the most preferred method, a method for resource recovery of red mud, a feasible technical solution includes the following steps:

[0052] (1) The proportion of each raw material by mass is red mud (dry basis): mineralizer: regulator: crystal nucleating agent: water = 100: (4-10): (4-12): (3-15): (300-600);

[0053] (2) adding raw materials into a reaction vessel and stirring to form a slurry;

[0054] (3) In a closed reaction vessel, the slurry is heated to 250-300° C. with continuous stirring at a speed of 250-350 rpm, and the pressure is increased and the temperature is kept constant for reaction for 60-120 min.

[0055] (4) releasing the slurry after the reaction and filtering it with a spiral centrifuge while it is still hot; filtering out the mother liquor and returning it to the alumina process;

[0056] (5) The filtered cake is then washed with hot water above 50°C and filtered twice. The washing water can be used in step (1).

[0057] (6) The washed filter cake is added to a mixer together with clean water, stirred and dispersed, and then separated by a double-drum wet magnetic separator into iron concentrate and secondary red mud.

[0058] In the following examples and comparative examples, various mineralizers, regulators and crystal nucleating agents are dried, ground, sieved, and -200 mesh is taken as raw material.

[0059] Example 1: Red mud produced by a company in Baise, Guangxi was selected and analyzed to find that its main components were Fe2O3, Al2O3, R2O, CaO and SiO2, as shown in Table 2 below.

[0060] Table 2 Main chemical components of dried red mud from a company in Baise, Guangxi (wt%)

[0061] Element <![CDATA[Fe 2 THE 3 ]]> <![CDATA[Al 2 THE 3 ]]> <![CDATA[SiO 2 ]]> CaO <![CDATA[R 2 The]]> content 36.6 18.8 8.5 17.6 3.6

[0062] A red mud resource management method of the present invention has the following preferred specific implementation steps:

[0063] (1) The ratio of red mud (dry basis): dry bagasse powder: quartz powder: magnetite powder: water is 100: 8: 8: 3: 400;

[0064] (2) adding raw materials into a reaction vessel and stirring to form a slurry;

[0065] (3) In a closed reaction vessel, set the speed to 300 rpm and continue stirring until the material is discharged;

[0066] (4) Heat the slurry to 300°C and then increase the pressure and keep the temperature to react for 120 minutes.

[0067] (5) releasing the slurry after the reaction and filtering it while hot; filtering out the mother liquor and returning it to the alumina process;

[0068] (6) The filtered cake is then washed with 75°C hot water and filtered twice. The washing water can be used in step (1).

[0069] (7) The washed filter cake is added to a mixer together with clean water, stirred and dispersed, and then separated by a double-drum wet magnetic separator into iron concentrate and secondary red mud.

[0070] Through the above methods, the resource management effect of red mud is as follows:

[0071] (1) The yield of iron concentrate obtained is 45.6% of red mud, and the iron ore grade (TFe) is 70.1%;

[0072] (2) The moisture content of secondary red mud is 25.5%, Na 2 The O content is 0.65%.

[0073] Comparative Example 1:

[0074] The steps are basically the same as those in Example 1, except that the quartz powder in step (1) is replaced with quicklime powder in equal amounts. After the above method, the resource recovery effect of red mud is as follows:

[0075] (1) The yield of iron concentrate obtained is 25.3% of red mud, and the iron ore grade (TFe) is 60.2%;

[0076] (2) The moisture content of secondary red mud is 27.6% and the Na2O content is 1.5%.

[0077] Analysis of this comparative example 1 shows that, since the raw red mud contains 17.6% CaO and 8.5% SiO2, the addition of quicklime powder makes the silicon required for the formation of calcium silicate obviously insufficient, and the purpose of mineralization and dealkalization cannot be achieved.

[0078] Comparative Example 2:

[0079] The steps are basically the same as those in Example 1, except that the temperature in step (4) is adjusted from 300°C to 200°C. After the above method, the resource recovery effect of red mud is as follows:

[0080] (1) The yield of iron concentrate obtained is 25.6% of red mud, and the iron ore grade (TFe) is 62.8%;

[0081] (2) The moisture content of secondary red mud is 29.3% and the Na2O content is 0.8%.

[0082] Analysis of Example 1 and Comparative Example 2 shows that the heating temperature has a significant impact on the resource recovery effect.

[0083] Comparative Example 3:

[0084] The steps are basically the same as those in Example 1, except that the time in step (4) is adjusted from 120 min to 60 min. After the above method, the resource recovery effect of red mud is as follows:

[0085] (1) The yield of iron concentrate obtained is 37.2% of red mud, and the iron ore grade (TFe) is 68.5%;

[0086] (2) The moisture content of secondary red mud is 28.3% and the Na2O content is 0.9%.

[0087] Analysis of Example 1 and Comparative Example 3 shows that extending the reaction time is beneficial to improving the resource recovery effect.

[0088] Comparative Example 4:

[0089] The steps are basically the same as those in Example 1, except that the dry bagasse powder in step (1) is replaced with rice husk powder. After the above method, the resource management effect of red mud is as follows:

[0090] (1) The yield of iron concentrate obtained is 46.8% of red mud, and the iron ore grade (TFe) is 68.9%;

[0091] (2) The moisture content of secondary red mud is 27.6% and the Na2O content is 0.9%.

[0092] Analysis of Example 1 and Comparative Example 4 shows that in the resource management of red mud, the effects of rice husk powder and bagasse powder are similar.

[0093] Example 2: Dehydrated red mud produced by a company in Zibo, Shandong Province was selected and its moisture content was 40%. After drying, the main component of the dried red mud was Fe 2 O 3 、Al 2 O 3 , CaO, SiO 2 and R 2O, etc., as shown in Table 3 below.

[0094] Table 3 Main chemical components of dried red mud from a company in Zibo (wt%)

[0095] Element <![CDATA[Fe 2 THE 3 ]]> <![CDATA[Al 2 THE 3 ]]> <![CDATA[SiO 2 ]]> CaO <![CDATA[R 2 The]]> content 38.9 16.2 7.5 1.5 4.1

[0096] A red mud resource management method of the present invention has the following preferred specific implementation steps:

[0097] (1) The ratio of dehydrated red mud: starch: slaked lime powder: iron ore concentrate: water is 100: 6: 5: 2: 300;

[0098] (2) adding raw materials into a reaction vessel and stirring to form a slurry;

[0099] (3) In a closed reaction vessel, set the speed to 250 rpm and continue stirring until the material is discharged;

[0100] (4) heating the slurry to 300° C. and then increasing the pressure and keeping the temperature to react for 90 minutes;

[0101] (5) releasing the slurry after the reaction and filtering it while hot; filtering out the mother liquor and returning it to the alumina process;

[0102] (6) The filtered cake is then washed with 60°C hot water and filtered twice. The washing water can be used in step (1);

[0103] (7) The washed filter cake is added to a mixer together with clean water, stirred and dispersed, and then separated by a double-drum wet magnetic separator into iron concentrate and secondary red mud;

[0104] Through the above methods, the resource management effect of red mud is as follows:

[0105] (1) The yield of the obtained iron concentrate is 49.3% of the dehydrated red mud, the iron ore grade (TFe) is 72.2%, and the calculated iron extraction rate is 91.5%;

[0106] (2) The moisture content of secondary red mud is 23.6% and the R2O content is 0.6%.

[0107] Comparative Example 5:

[0108] The steps are basically the same as those in Example 2, except that the proportion of ingredients in step (1) is changed to:

[0109] Dehydrated red mud: pig manure powder: slaked lime powder: iron concentrate: water = 100: 8: 5: 2: 300; after the above method, the resource management effect of red mud is as follows:

[0110] (1) The yield of the obtained iron concentrate was 48.9% of the red mud, the iron ore grade (TFe) was 72.0%, and the calculated iron extraction rate was 90.5%;

[0111] (2) The moisture content of secondary red mud is 24.2% and the Na2O content is 0.7%.

[0112] Analysis of Example 2 and Comparative Example 5 shows that in the resource management of red mud, the effect of pig manure powder is close to that of starch.

[0113] Example 3: Dehydrated red mud produced by a company in Binzhou, Shandong Province was selected and its moisture content was 41.8%. After drying, the main component of the dried red mud was Fe 2 O 3 、Al 2 O 3 , CaO and SiO 2 Etc., as shown in Table 4 below.

[0114] Table 4 Main chemical components of dried red mud from a company in Binzhou, Shandong Province (wt%)

[0115] Element <![CDATA[Fe 2 THE 3 ]]> <![CDATA[Al 2 THE 3 ]]> <![CDATA[SiO 2 ]]> CaO <![CDATA[R 2 The]]> content 38.5 17.0 7.6 1.7 4.4

[0116] A method for recycling red mud of the present invention, a preferred specific implementation method thereof is: basically according to the process of Example 2, only the temperature condition of step (4) is changed, and the recycling effect of red mud is as follows:

[0117] Table 5 The resource utilization effect of red mud under various temperature conditions.

[0118]

Claims

1. A method for resource recovery of red mud, characterized in that its basic process consists of the steps of ingredient mixing, heating mineralization, solid-liquid separation, magnetic separation and the like.

2. The mixing of ingredients according to claim 1, It is characterized in that Calculated by weight, the components are: 100 parts of red mud (dry basis), 2 to 10 parts of mineralizer, 1 to 20 parts of regulator, 0 to 20 parts of crystal nucleating agent, and 200 to 800 parts of water.

3. The mineralizer according to claim 2, It is characterized in that The mineralizer is powdered biomass.

4. The regulator according to claim 2, It is characterized in that The regulator is powdered lime, quartz or silicon dioxide.

5. The heating mineralization according to claim 1, It is characterized in that The process conditions of the heating mineralization are: adding the slurry of the above components into a closed reaction container, heating to above 150° C., and keeping the temperature for more than 30 minutes.

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