CN111943534B - Process for preparing portland cement by utilizing red mud - Google Patents

Process for preparing portland cement by utilizing red mud Download PDF

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CN111943534B
CN111943534B CN202010907902.9A CN202010907902A CN111943534B CN 111943534 B CN111943534 B CN 111943534B CN 202010907902 A CN202010907902 A CN 202010907902A CN 111943534 B CN111943534 B CN 111943534B
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red mud
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washing
sodium
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CN111943534A (en
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陶予敏
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Kuqa Hongshi Cement Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B7/00—Hydraulic cements
    • C04B7/24—Cements from oil shales, residues or waste other than slag
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C1/00—Magnetic separation
    • B03C1/005—Pretreatment specially adapted for magnetic separation
    • B03C1/015—Pretreatment specially adapted for magnetic separation by chemical treatment imparting magnetic properties to the material to be separated, e.g. roasting, reduction, oxidation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C1/00—Magnetic separation
    • B03C1/02—Magnetic separation acting directly on the substance being separated
    • B03C1/30—Combinations with other devices, not otherwise provided for
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D7/00—Carbonates of sodium, potassium or alkali metals in general
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
    • C01F7/06—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process
    • C01F7/0693—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process from waste-like raw materials, e.g. fly ash or Bayer calcination dust
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
    • C01F7/14—Aluminium oxide or hydroxide from alkali metal aluminates
    • C01F7/141—Aluminium oxide or hydroxide from alkali metal aluminates from aqueous aluminate solutions by neutralisation with an acidic agent
    • C01F7/142—Aluminium oxide or hydroxide from alkali metal aluminates from aqueous aluminate solutions by neutralisation with an acidic agent with carbon dioxide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/44—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water
    • C01F7/441—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C01G49/02—Oxides; Hydroxides
    • C01G49/08—Ferroso-ferric oxide [Fe3O4]
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B7/00—Hydraulic cements
    • C04B7/36—Manufacture of hydraulic cements in general
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B7/00—Hydraulic cements
    • C04B7/36—Manufacture of hydraulic cements in general
    • C04B7/38—Preparing or treating the raw materials individually or as batches, e.g. mixing with fuel
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B7/00—Hydraulic cements
    • C04B7/36—Manufacture of hydraulic cements in general
    • C04B7/38—Preparing or treating the raw materials individually or as batches, e.g. mixing with fuel
    • C04B7/40—Dehydrating; Forming, e.g. granulating
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B7/00—Hydraulic cements
    • C04B7/36—Manufacture of hydraulic cements in general
    • C04B7/43—Heat treatment, e.g. precalcining, burning, melting; Cooling
    • C04B7/44—Burning; Melting
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency

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Abstract

The invention discloses a process for preparing portland cement by utilizing red mud. The red mud is sent into an alkali extraction and alumina extraction unit to obtain sodium carbonate, alumina and low-sodium and low-alumina red mud, then the low-sodium and low-alumina red mud is sent into a drying and granulating unit to be dried and granulated, then the low-sodium and low-alumina red mud is sent into a reducing unit to be reduced through reducing gas, ferric oxide in the low-sodium and low-alumina red mud is reduced into ferroferric oxide, then the low-sodium and low-alumina red mud is sent into a grinding unit to be ground, then the ground low-sodium and low-alumina red mud is sent into a magnetic separation unit to remove the ferroferric oxide in the low-sodium and low-alumina red mud to obtain low-sodium and low-alumina red mud, and then the low-sodium and low-alumina red mud and limestone are evenly mixed and then sent into a unit to be burned to obtain silicate cement clinker. In the invention, the red mud is fully utilized to obtain soda ash, alumina, ferroferric oxide, low-sodium low-aluminum low-iron red mud, and the low-sodium low-aluminum low-iron red mud and limestone are utilized to prepare portland cement, thereby being beneficial to energy conservation and emission reduction.

Description

Process for preparing portland cement by utilizing red mud
Technical Field
The invention belongs to the technical field of red mud utilization, and particularly relates to a process for preparing portland cement by utilizing red mud.
Background
In the prior art, alumina is mostly produced by using a Bayer process, which mainly uses alkaline solution to dissolve solid-phase alumina hydrate in bauxite into sodium aluminate, then the sodium aluminate is treated to obtain aluminum hydroxide, and the aluminum hydroxide is roasted to obtain the alumina. After bauxite is subjected to alkaline solution to dissolve out solid-phase alumina hydrate, the red mud is formed by the residual impurities such as soil, iron, titanium, silicon dioxide and the like. The main component of the red mud waste liquid is sodium aluminate which can be written asNaAlO 2 Or is Na 2 O•Al 2 O 3 The red mud also contains sodium in a combined form, such as sodium silicate, written as Na 2 SiO 3 Can also be written as Na 2 O•SiO 2 。
In the prior art, the utilization of the red mud in the aspect of building materials is difficult because the red mud contains more alkali, namely Na 2 The content of O is high, and the high alkali content makes the building material made of the red mud easy to deteriorate when meeting water and carbon dioxide, so that the durability and reliability of the building material are reduced, and great potential safety hazards are caused.
In the building material aspect, portland cement plays an important role, and portland cement clinker is mainly composed of calcium oxide (CaO) and silicon dioxide (SiO) 2 ) Aluminum oxide (Al) 2 O 3 ) And iron oxide (Fe) 2 O 3 ) And (4) forming. Iron oxide is one of the important chemical components in clinker, can react with calcium oxide and aluminum oxide to generate tetracalcium aluminoferrite, but when the iron oxide content in cement is too high, 4CaO 2 O 3 •Fe 2 O 3 And 3 CaO. Al is reduced 2 O 3 And 3 CaO. Al 2 O 3 Too large a content of (b) results in a decrease in cement strength, and therefore, it is necessary to strictly control the iron content in portland cement in order to produce high quality portland cement.
Disclosure of Invention
In order to solve the problems in the background art and achieve the aim of preparing portland cement with high economic value and high reliability by utilizing red mud at lower cost, the invention provides a process for preparing portland cement by utilizing red mud.
A process for preparing portland cement by utilizing red mud comprises the following steps: the red mud is sent into an alkali extraction and alumina extraction unit to obtain sodium carbonate, alumina and low-sodium and low-aluminum red mud, and then the low-sodium and low-aluminum red mud is sent into a drying and granulating unit to enterDrying and granulating, sending the low-sodium low-aluminum red mud into a reduction unit, wherein the reduction unit is essentially a reduction furnace, reducing ferric oxide in the low-sodium low-aluminum red mud into ferroferric oxide by reducing gas in the reduction furnace, sending the low-sodium low-aluminum red mud into a grinding unit for grinding, then sending the ground low-sodium low-aluminum red mud into a magnetic separation unit for removing the ferroferric oxide in the low-sodium low-aluminum red mud to obtain the low-sodium low-aluminum low-iron red mud, and if the low-sodium low-aluminum red mud is not reduced by the reducing gas, because the ferric oxide has no magnetism, the magnetic separation unit can not remove the iron in the red mud, but can not remove the iron in the red mud, thus the 3CaO 2 O 3 The content of the sodium-containing, low-aluminum and low-iron red mud is too high, so that the strength of the portland cement is reduced, the low-sodium, low-aluminum and low-iron red mud and limestone are uniformly mixed and then ground, the ground mixture is sent into a clinker unit to be burnt, and in the process, the limestone is burnt into lime to obtain portland cement clinker; the cooking unit is heated by flame, high-temperature flue gas generated by the cooking unit is used as a heat source to enter the waste heat boiler, process water is introduced into a cold material flow inlet of the waste heat boiler, and the process water exchanges heat with the high-temperature flue gas and is converted into steam for the drying and granulating unit to use.
Further, the alkali extraction and alumina extraction unit comprises a mixing and diluting unit, firstly, in the mixing and diluting unit, diluting red mud to obtain dilute red mud, then washing the dilute red mud to obtain washing liquor containing sodium aluminate and dilute red mud, carbonizing the washed dilute red mud, reacting the carbonized dilute red mud with gas with reaction components of carbon dioxide, reacting sodium silicate which is indissolvable in the dilute red mud to generate sodium carbonate dissolved in a liquid phase, and washing the reacted dilute red mud again to obtain washing liquor containing sodium carbonate and low-sodium low-aluminum red mud; and in addition, collecting washing liquor containing sodium aluminate and washing liquor containing sodium carbonate to obtain mixed washing liquor, sending one part of the mixed washing liquor to a mixed dilution unit for diluting the red mud, evaporating and concentrating the other part of the mixed washing liquor, carbonizing the evaporated and concentrated mixed washing liquor, reacting the carbonized mixed washing liquor with gas with a reaction component of carbon dioxide, converting the sodium aluminate in the mixed washing liquor into aluminum hydroxide precipitate and sodium carbonate, then filtering, separating the aluminum hydroxide precipitate from the sodium carbonate solution, drying and roasting the aluminum hydroxide precipitate, reacting to generate aluminum oxide, and evaporating and drying the sodium carbonate solution to obtain dried sodium carbonate.
Further, after diluting the red mud to obtain diluted red mud, carrying out m-grade water washing on the diluted red mud, wherein m is greater than 3, collecting washing water of each-grade water washing, sending the washing water to the previous grade to be used as washing water for washing the diluted red mud, and finally collecting the washing water for washing the diluted red mud from the 1 st grade in the m-grade water washing to be used as washing water containing sodium aluminate; when the reacted dilute red mud is washed, n-grade washing is adopted, wherein n satisfies m + n >6, when the n-grade washing is carried out, the washing water of each grade of washing is collected and sent to the previous grade as the washing water for washing the red mud, finally, the washing water for washing the dilute red mud is collected from the 1 st grade of the n-grade washing, sent to the m-grade of the m-grade washing as the washing water for washing the dilute red mud, steam is used as a heat source in the evaporation concentration process before carbonizing the mixed washing water and the process of evaporating and drying the sodium carbonate solution, the condensed water generated in the heat exchange process by the steam is collected and is supplemented into the n-grade washing as the washing water of the n-grade washing, and finally, the washing water for washing the dilute red mud is collected at the 1 st grade of the m-grade washing to obtain the washing water containing the sodium aluminate and the mixed washing water of the washing water containing the sodium carbonate.
Furthermore, a secondary aluminum extraction unit is also arranged; before the red mud is sent to the alkali extraction and aluminum oxide extraction unit, the red mud firstly enters a secondary aluminum extraction unit, and aluminum oxide in the red mud is dissolved out by using concentrated sodium hydroxide.
Further, concentrated sodium hydroxide is used at a concentration of 30% to 40%.
Further, in the reduction unit, when the reduction is completed, the reducing gas used is hydrogen or carbon monoxide.
Further, in the reduction unit, when reduction is performed using a reducing gas, nitrogen gas is also mixed into the reducing gas to produce an inert atmosphere at the time of reduction.
Further, the reduction temperature was maintained at 600 ℃ or higher during reduction in the reduction unit.
Further, in the milling unit, the low-sodium low-alumina red mud is milled to 200 meshes by a ball mill.
Further, the device also comprises a pre-magnetic separation unit; the low-sodium low-aluminum red mud sent out from the reduction unit is firstly sent into a pre-magnetic separation unit, iron is removed through pre-magnetic separation, ferroferric oxide particles are enriched, the obtained low-sodium low-aluminum low-iron red mud and limestone are uniformly mixed and then ground, the obtained low-sodium low-aluminum low-iron red mud and limestone are sent into a clinker unit to be burned to obtain portland cement clinker, the ferroferric oxide particles obtained through pre-magnetic separation are sent into a grinding unit to be ground, and then the ground ferroferric oxide particles are sent into a magnetic separation unit to be magnetically separated, so that high-grade ferroferric oxide is obtained.
Compared with the prior art, the invention has the following beneficial effects: (1) in the invention, the components in the red mud stacked as waste are fully utilized through various processes to obtain soda ash, alumina, ferroferric oxide and low-sodium low-aluminum low-iron red mud, and the low-sodium low-aluminum low-iron red mud and limestone are utilized to prepare the silicate cement with high economic value, so that the cost is low and the economic value of the product is high; (2) by utilizing the stacked waste red mud, energy is saved and emission is reduced; (3) in the process, the reduced low-sodium low-aluminum red mud is subjected to pre-magnetic separation, most of components except iron are removed, so that ferroferric oxide particles are enriched, then the reduced low-sodium low-aluminum red mud is subjected to milling, and then the reduced low-sodium low-aluminum red mud is subjected to magnetic separation to obtain high-grade magnets and low-sodium low-aluminum low-iron red mud, so that a lot of load is reduced during milling, the milling efficiency is favorably improved, and the energy conservation and emission reduction are favorably realized.
Drawings
FIG. 1: the process diagram of the first embodiment.
FIG. 2 is a schematic diagram: the process flow diagram of the alkali extraction and alumina extraction unit is shown.
FIG. 3: the process diagram of the second example is shown.
In the figure: 1. the device comprises an alkali extraction and alumina extraction unit, a 1.1 mixing and diluting unit, a 2 drying and granulating unit, a 3 reducing unit, a 4 grinding unit, a 5 magnetic separation unit, a 6 clinker unit, a 7 secondary aluminum extraction unit and a 8 pre-magnetic separation unit.
Detailed Description
The embodiments of the present invention will be described in conjunction with the drawings in the specification, and the embodiments are disclosed for the purpose of illustrating the invention rather than limiting the invention, and all technical solutions which are simple to replace, combine and develop on the basis of the present invention shall fall within the protection scope of the present invention.
Example one
As shown in fig. 1 and fig. 2, in the process for preparing portland cement by using red mud, the red mud is sent to an alkali extraction and alumina extraction unit 1 to obtain sodium carbonate, alumina and low-sodium and low-alumina red mud, then the low-sodium and low-alumina red mud is sent to a drying and granulating unit 2 to be dried and granulated, then the low-sodium and low-alumina red mud is sent to a reducing unit 3 to be reduced by reducing gas to reduce ferric oxide in the low-sodium and low-alumina red mud into ferroferric oxide, then the low-sodium and low-alumina red mud is sent to a grinding unit 4 to be ground, then the ground low-sodium and low-alumina red mud is sent to a magnetic separation unit 5 to remove the ferroferric oxide in the low-sodium and low-alumina red mud to obtain the low-sodium and low-alumina red mud, the low-sodium and low-alumina red mud and limestone are uniformly mixed and then ground, and then are sent to a clinker unit 6 to be burned to obtain portland cement clinker; the burning unit 6 is a cement rotary kiln heated by flame, high-temperature flue gas generated by the burning unit is used as a heat source to enter a waste heat boiler, process water is introduced into a cold material flow inlet of the waste heat boiler, and the process water exchanges heat with the high-temperature flue gas and is converted into steam for the drying and granulating unit 2 to use.
The alkali and alumina extraction unit 1 comprises a mixing and diluting unit 1.1, firstly, diluting red mud in the mixing and diluting unit 1.1 to obtain dilute red mud, then washing the dilute red mud to obtain washing liquor containing sodium aluminate and the dilute red mud, carbonizing the washed dilute red mud, reacting the carbonized dilute red mud with gas with carbon dioxide as a reaction component, reacting indissolvable sodium silicate in the dilute red mud to generate sodium carbonate dissolved in a liquid phase, washing the reacted dilute red mud, and then filtering to obtain washing liquor containing the sodium carbonate and low-sodium low-aluminum red mud; in addition, washing liquor containing sodium aluminate and washing liquor containing sodium carbonate are collected to obtain mixed washing liquor, one part of the mixed washing liquor is sent to a mixed dilution unit 1.1 for diluting red mud, the other part of the mixed washing liquor is evaporated and concentrated, the evaporated and concentrated mixed washing liquor is carbonized, reacts with gas with carbon dioxide as a reaction component, sodium aluminate in the mixed washing liquor is converted into aluminum hydroxide precipitate and sodium carbonate, the aluminum hydroxide precipitate is separated from the sodium carbonate solution through filtration, the aluminum hydroxide precipitate is dried and roasted, aluminum oxide is generated through reaction, and the sodium carbonate solution is evaporated and dried to obtain dried sodium carbonate.
After diluting red mud to obtain dilute red mud, carrying out m-grade water washing on the dilute red mud, wherein m =4, collecting washing water of each grade of water washing, sending the washing water to the previous grade as washing water for washing the dilute red mud, and finally collecting the washing water for washing the dilute red mud from the 1 st grade in the m-grade water washing as washing water containing sodium aluminate; when the reacted dilute red mud is washed by water, n-grade water washing is adopted, wherein n =4, m + n >6 is satisfied, when n-stage water washing is carried out, the washing water of each stage of water washing is collected and sent to the previous stage to be used as the washing water for washing the red mud, finally, the washing water for washing the diluted red mud is collected from the 1 st stage of the n-stage water washing and sent to the m th stage of the m-stage water washing, namely, the 4 th stage, as washing water for washing the dilute red mud of the 4 th stage, steam is used as a heat source in the evaporation and concentration process before the carbonization of the mixed washing water and the process of evaporating and drying the sodium carbonate solution, and collecting the condensed water generated in the heat exchange process of the steam as the nth stage in the n-stage water washing, namely, the washing water of the 4 th-stage washing is supplemented into the n-stage washing, and finally, the washing water for washing the diluted red mud is collected at the 1 st stage of the m-stage washing to obtain the washing liquid containing the sodium aluminate and the mixed washing liquid containing the sodium carbonate.
In the reduction unit 3, when the reduction is completed, the reducing gas used is hydrogen, and at the same time, nitrogen is mixed into carbon monoxide to produce an inert atmosphere during the reduction, while the reduction temperature is maintained at 600 ℃.
In the milling unit 4, the low-sodium low-alumina red mud is milled to 200 mesh by a ball mill.
Example two
As shown in fig. 2 and 3, in the process for preparing portland cement by using red mud, the red mud is sent to an alkali extraction alumina unit 1 to obtain sodium carbonate, alumina and low-sodium low-alumina red mud, then the low-sodium low-alumina red mud is sent to a drying granulation unit 2 to be dried and granulated, then the low-sodium low-alumina red mud is sent to a reduction unit 3 to be reduced by reducing gas to reduce the ferric oxide in the low-sodium low-alumina red mud into ferroferric oxide, the low-sodium low-alumina red mud sent from the reduction unit 3 is firstly sent to a pre-magnetic separation unit 8 to be de-ironed by pre-magnetic separation, the obtained low-sodium low-alumina low iron and limestone are evenly mixed and ground after clinker is sent to a unit 6 to be burned to obtain portland cement clinker, the iron obtained by pre-magnetic separation is sent to a grinding unit 4 to be ground, and then sent to a magnetic separation unit 5 to obtain high-grade ferroferric oxide. The burning unit 6 is a flame-heated cement rotary kiln, high-temperature flue gas generated by the burning unit is used as a heat source and enters a waste heat boiler, process water is introduced into a cold material flow inlet of the waste heat boiler, and the process water exchanges heat with the high-temperature flue gas and is converted into steam for the drying and granulating unit 2 to use.
The alkali-extracting and alumina-extracting unit 1 comprises a mixing and diluting unit 1.1, firstly, diluting red mud in the mixing and diluting unit 1.1 to obtain dilute red mud, then washing the dilute red mud to obtain washing liquor containing sodium aluminate and the dilute red mud, carbonizing the washed dilute red mud, reacting the carbonized dilute red mud with gas with reaction components of carbon dioxide, reacting insoluble sodium silicate in the dilute red mud to generate sodium carbonate dissolved in a liquid phase, washing the reacted dilute red mud again, and then filtering to obtain washing liquor containing the sodium carbonate and low-sodium low-aluminum red mud; in addition, washing liquor containing sodium aluminate and washing liquor containing sodium carbonate are collected to obtain mixed washing liquor, one part of the mixed washing liquor is sent to a mixed dilution unit 1.1 for diluting red mud, the other part of the mixed washing liquor is evaporated and concentrated, the evaporated and concentrated mixed washing liquor is carbonized again and reacts with gas with reaction components of carbon dioxide, the sodium aluminate in the mixed washing liquor is converted into aluminum hydroxide precipitate and sodium carbonate, the aluminum hydroxide precipitate is separated from the sodium carbonate solution through filtration, the aluminum hydroxide precipitate is dried and roasted, aluminum oxide is generated through reaction, and the sodium carbonate solution is evaporated and dried to obtain dried sodium carbonate.
After diluting red mud to obtain dilute red mud, carrying out m-grade water washing on the dilute red mud, wherein m =4, collecting washing water of each grade of water washing, sending the washing water to the previous grade as washing water for washing the dilute red mud, and finally collecting the washing water for washing the dilute red mud from the 1 st grade in the m-grade water washing as washing water containing sodium aluminate; when the reacted dilute red mud is washed by water, n-grade water washing is adopted, wherein n =5, m + n >6 is satisfied, when n-stage water washing is carried out, the washing water of each stage of water washing is collected and sent to the previous stage to be used as the washing water for washing the red mud, finally, the washing water for washing the diluted red mud is collected from the 1 st stage of the n-stage water washing and sent to the m-th stage of the m-stage water washing to be used as the washing water for washing the diluted red mud of the m-th stage, in the evaporation concentration process before carbonizing the mixed washing liquid and the evaporation drying process of the sodium carbonate solution, steam is used as a heat source, and collecting condensed water generated in the heat exchange process of the steam, supplementing the condensed water into the n-level water washing as the washing water of the n-level water washing, and finally, and collecting washing water for washing the diluted red mud in the 1 st stage of m-stage water washing to obtain washing liquid containing sodium aluminate and mixed washing liquid containing sodium carbonate.
A secondary aluminum extraction unit 7 is also arranged; before the red mud is sent to the alkali extraction and alumina extraction unit 1, the red mud firstly enters a secondary aluminum extraction unit 7, and alumina in the red mud is dissolved out by using concentrated sodium hydroxide with the concentration of 40 percent.
In the reduction unit 3, carbon monoxide is used as the reducing gas when the reduction is completed, and in the reduction unit 3, nitrogen gas is further mixed into the reducing gas when the reduction is performed using the reducing gas, so that an inert atmosphere during the reduction is produced, and the reduction temperature is 700 ℃.
In the milling unit 4, the low-sodium low-alumina red mud is milled to 200 mesh by a ball mill.
EXAMPLE III
The third example is not substantially different from the second example, and the secondary aluminum extraction unit 7 is provided in the same manner, except that in the secondary aluminum extraction unit 7, alumina in the red mud is eluted using a concentrated sodium hydroxide solution having a concentration of 30%.
The above embodiments are not detailed in the prior art.

Claims (5)

1. A process for preparing portland cement by utilizing red mud is characterized by comprising the following steps: the red mud is sent into an alkali extraction and alumina extraction unit (1) to obtain sodium carbonate, alumina and low-sodium and low-aluminum red mud, then sending the low-sodium low-aluminum red mud into a drying and granulating unit (2), drying and granulating, sending the low-sodium low-aluminum red mud into a reduction unit (3), reducing with carbon monoxide, mixing with nitrogen gas to produce inert atmosphere during reduction, maintaining the reduction temperature above 600 deg.C, so as to reduce the ferric oxide in the low-sodium low-aluminum red mud into ferroferric oxide, then the low-sodium low-aluminum red mud is sent into a milling unit (4) to be milled, then, sending the ground low-sodium low-aluminum red mud to a magnetic separation unit (5), removing ferroferric oxide in the low-sodium low-aluminum red mud to obtain low-sodium low-aluminum low-iron red mud, uniformly mixing the low-sodium low-aluminum low-iron red mud and limestone, grinding the mixture, and sending the mixture to a clinker unit (6) for burning to obtain portland cement clinker; the cooking unit (6) is heated by flame, high-temperature flue gas generated by the heating is used as a heat source to enter the waste heat boiler, process water is introduced into a cold material flow inlet of the waste heat boiler, and the process water exchanges heat with the high-temperature flue gas and is converted into steam for the drying and granulating unit (2) to use;
the alkali-extracting and alumina-extracting unit (1) comprises a mixing and diluting unit (1.1), firstly, diluting red mud in the mixing and diluting unit (1.1) to obtain dilute red mud, then washing the dilute red mud to obtain washing liquor containing sodium aluminate and the dilute red mud, carbonizing the washed dilute red mud, reacting the carbonized dilute red mud with gas with carbon dioxide as a reaction component, reacting indissolvable sodium silicate in the dilute red mud to generate sodium carbonate dissolved in a liquid phase, washing the reacted dilute red mud again, and then filtering to obtain washing liquor containing the sodium carbonate and low-sodium and low-aluminum red mud; in addition, collecting washing liquor containing sodium aluminate and washing liquor containing sodium carbonate to obtain mixed washing liquor, sending one part of the mixed washing liquor to a mixed dilution unit (1.1) for diluting the red mud, evaporating and concentrating the other part of the mixed washing liquor, carbonizing the evaporated and concentrated mixed washing liquor, reacting the carbonized mixed washing liquor with gas with a reaction component of carbon dioxide, converting the sodium aluminate in the mixed washing liquor into aluminum hydroxide precipitate and sodium carbonate, then filtering, separating the aluminum hydroxide precipitate from the sodium carbonate solution, drying and roasting the aluminum hydroxide precipitate, reacting to generate aluminum oxide, evaporating and drying the sodium carbonate solution to obtain dried sodium carbonate;
after diluting red mud to obtain dilute red mud, carrying out m-grade water washing on the dilute red mud, wherein m is more than 3, collecting washing water of each-grade water washing, sending the washing water to the previous grade as washing water for washing the dilute red mud, and finally collecting the washing water for washing the dilute red mud from the 1 st grade in the m-grade water washing as washing water containing sodium aluminate; when the reacted dilute red mud is washed by water, n-grade water washing is adopted, wherein n satisfies m + n >6, when n-stage water washing is carried out, the washing water of each stage of water washing is collected and sent to the previous stage to be used as the washing water for washing the red mud, finally, the washing water for washing the diluted red mud is collected from the 1 st stage of the n-stage water washing and sent to the m-th stage of the m-stage water washing to be used as the washing water for washing the diluted red mud of the m-th stage, in the evaporation concentration process before carbonizing the mixed washing liquid and the evaporation drying process of the sodium carbonate solution, steam produced by a waste heat boiler is used as a heat source, and the condensed water generated in the heat exchange process of the steam is collected and used as the washing water of the nth stage of water washing to be supplemented into the nth stage of water washing, and finally, and in the 1 st stage of m-stage water washing, collecting washing water for washing the diluted red mud to obtain washing liquid containing sodium aluminate and mixed washing liquid containing sodium carbonate.
2. The process for preparing portland cement by using red mud as claimed in claim 1, wherein the process comprises the following steps: a secondary aluminum extraction unit (7) is also arranged; before the red mud is sent to the alkali extraction and aluminum oxide extraction unit (1), the red mud firstly enters a secondary aluminum extraction unit (7), and aluminum oxide in the red mud is dissolved out by using concentrated sodium hydroxide.
3. The process for preparing portland cement by using red mud as claimed in claim 2, wherein the process comprises the following steps: the concentration of the concentrated sodium hydroxide used is 30-40%.
4. The process for preparing portland cement by using red mud as claimed in claim 1, wherein the process comprises the following steps: in the milling unit (4), the low-sodium low-aluminum red mud is milled to 200 meshes by a ball mill.
5. The process for preparing portland cement by using red mud as claimed in claim 1, wherein the process comprises the following steps: also comprises a pre-magnetic separation unit (8); the low-sodium low-aluminum red mud sent out from the reduction unit (3) is firstly sent into a pre-magnetic separation unit (8), iron is removed through pre-magnetic separation, the obtained low-sodium low-aluminum low-iron red mud and limestone are uniformly mixed and then ground, the obtained low-sodium low-aluminum low-iron red mud and limestone are sent into a clinker unit (6) to be burned to obtain portland cement clinker, the iron obtained through pre-magnetic separation is sent into a grinding unit (4) to be ground, and then the ground iron is sent into a magnetic separation unit (5) to obtain high-grade ferroferric oxide.
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