WO2015039198A1

WO2015039198A1 - Process for producing a chemical composition for the production of an active additive that can be used as a portland clinker substitute, chemical composition and use of said composition

Info

Publication number: WO2015039198A1
Application number: PCT/BR2014/000208
Authority: WO
Inventors: Clair CERON
Original assignee: Votorantim Cimentos S/A; Companhia Brasileira De Alumínio
Priority date: 2013-09-20
Filing date: 2014-06-24
Publication date: 2015-03-26
Also published as: BR102013024226B1; BR102013024226A2

Abstract

The present application relates to a process for producing a composition for partially substituting Portland clinker. The bauxite processing waste (red mud) initially undergoes a chemical treatment step, wherein (limestone) carbonates and silica derivatives (sand, silica clays, etc) are added until contents of SiO₂ > 30%, CaO > 10% and Na₂O < 10% are obtained. Following homogenization, the material is treated with heat (between 1000°C and 1500°C), partially melting and acquiring, upon cooling, a dark grey colour and free CaO content below 1.0%. The final product is then ground to a grain size distribution of 0.01-5 inches. The present application also relates to the composition produced by said process and use thereof, as a substitute for up to 30% of the Portland clinker in pozzolanic cements.

Description

Process for obtaining chemical composition for active addition production capable of replacing Portland clinker, chemical composition and use thereof

composition

[001] The present invention relates to a bauxite waste treatment process called red mud (red mud ^r ) for the production of active addition capable of substituting Portand clinker, preferably 1.0 to 50.0% Portland clinker. . Red mud is generated from the Bayer Process in the production of aluminum oxide. Its field of application is the manufacture of concrete cement and mortar.

State of the Art

The Bayer process of producing aluminum oxide from bauxite consists in solubilizing the alumina present in bauxite as gibbsite (AI (OH) 3 or AI2O3.3H2O), known in the aluminum industry as "Useful Alumina". , in caustic soda (NaOH) solution at a temperature of 150 ° C (digestion). This produces a supersaturated solution of sodium aluminate and the other bauxite components, called bauxite residue (RB), which are in the form of solids and are separated by the settling and filtration process. The generated RB, which still contains alkalinity even after washing, is usually deposited in wet or dry waste storage ponds. Storage of this material due to its high alkalinity and cation exchange capacity can cause serious environmental damage and requires a large area for disposal.

[003] The amount of RB generated in the process is directly related to the quality of the ore and its components. Its ratio may vary from 0.5 to 2 tons of RB per tonne of aluminum oxide produced.

[004] As a matter of knowledge, the Rio Branco cement factory is a large consumer of fly ash pozzolan from power plants coal base. A noteworthy example is the capping material of the Rio Branco cement limestone mine, which has sufficient kaolinitic clay for the production of good quality pozzolan, however, it has about 14% Fe203 in its chemical composition, making the pozzolan color after calcination brick red, making its application in cement manufacturing impossible due to the effect on the final (brownish) coloration of the product, which the market rejects.

Tables 1 and 2 below show the typical chemical compositions of bauxite and Bauxite Residue produced in the city of Alumínio - SP.

An alternative to the problems caused by the huge production of Bauxite Waste is the development of technologies for its reuse.

[007] The origin of the technology referred to in this patent application was the solution to the problem of the pozzolan's reddish color, thus seeking alternatives to change the pozzolan's color from red to dark gray or black, such that the final color of the cement was not changed.

Some documents dealing with this subject have been found in the literature, as described below:

Document CN101439938 deals with a rapid method for the treatment of hardening of ferrous aluminate made of red mud. The method comprises a) processing the red sludge, ie drying, grinding and filtering through a 100 mesh sieve, b) calculating the ingredients in a raw material composition by formulating clinker aggregate minerals including G2S , G4A3S and OAF; c) weigh the raw materials by weight percentage: 40 to 55% of red mud, 20 to 30% of limestone, 1.5 to 3% of iron dust, 20 to 30% of aluminum ores and it 5% of gibbsite; (d) mixing and calcining by uniformly mixing and grinding the ingredients in which the calcining temperature is between 1250 ° C and 1350 ° C; ee) prepare different types of fast hardening ferrous aluminate cement. The fast hardening of ferrous aluminate cement has the advantages that the fast hardening of ferrous aluminate cement has high initial strength, good cold resistance, corrosion resistance and high impermeability. Ferrous aluminate cement is suitable for cold weather, recovery, projected concrete preparation, prefabricated limb production, and so on. In addition, fast hardening cement using red mud creates greater social benefit and economic benefit. Document C 102500592 deals with processing the alkaline content in red alumina sludge comprising: i) reducing the red alumina sludge and transporting it to a dealkylation reaction tank, ii) performing the dealkylation, transmitting the sludge to a vacuum filter after washing, perform solid-liquid separation and transmit the solid in a rotary kiln, iii) perform calcination reduction and calcium addition in the alkaline material, iv) transport the red slurry in a separator, separating magnetic and non-magnetic parts, transport the magnetic part in a mill, perform pressure filtration of the non-magnetic part, and dry using a dry mortar.

Document PI9602657-0 deals with a red mud bauxite residue produced by the Bayer Process, treated in various centrifuges and re-grinding tanks to successively wash and remove water from the red mud. A final concentrated liquor is obtained in a first upstream centrifuge stage which is rich in alumina and caustics for their recovery and reuse. The concentrated red mud cake produced in the final downstream centrifuge / wash step is lower in caustic and alumina concentration allowing for environmentally acceptable disposal. The concentrated red mud cake is re-rolled and mixed with bauxite sand for disposal in a dry stacked damming area.

PI9602530-1 deals with a process in which red sludge, the residue in the production of alumina by the Bayer Process, is leached with sulfuric and hydrochloric acids under stirring and heating. The solid residue is separated from the solution containing the extracted metal ions by filtration. The solid residue containing silicates, low aluminum and titanium content, low calcium, magnesium, sodium, potassium and iron content is a low cost raw material for the in vitro ceramic industry. For the manufacture of in vitro-ceramic materials, this residue is fused and the vitreous mass is crystallized by heat treatment. Iron II present in the filtered solution is oxidized to iron III by the oxidizing action of hydrogen peroxide and is precipitated as ferric hydroxide by the addition of a caustic solution. After separation by filtration aluminum is recovered from the solution by precipitation as aluminum hydroxide by the addition of the same caustic solution as previously used.

Prior art documents deal with the correction of the reddish coloration of calcined clay to gray by mixing coal with clay during burning in a reducing environment, which requires special equipment for this, increasing the costs. unattractively.

In contrast, the technology under this patent uses at least 70% red mud, correcting the chemical composition with limestone to a minimum of 10% CaO, and with silicose material to a minimum percentage. 30% SiO 2. Said red sludge is burned at temperatures in the order of 1250 ° C, resulting in a product that has no hydraulic properties per se. Thus, it is an active addition that only acquires cementing properties when combined with Portland cement clinker, and to complement the mineralogy of the material produced is mainly amorphous material.

Goals:

[0015] This patent application is intended to make it feasible to use existing raw materials in already open mining areas, thus avoiding the opening of new deposits at greater distances from the factories by costing them and increasing CO2 emissions due to transport over long distances.

Still in the environmental field, this application prevents new dam lakes from being opened. This means preventing an area of about 50-70 acres from being contaminated as the soil of these dam lakes is not recoverable and useful. for only 5 years, apart from the fact that these lakes have very high pH (their waters are very caustic) and have their ecosystems totally damaged. In the world there are cases of breaches of barriers of lakes with deposit of "red mud" or bauxite waste, with disastrous consequences for the population and the environment. Finally, both monitoring a lake for this type of deposit and creating new lakes are very expensive for the industry and still represent damage to nature and dangers to humans.

In addition, the coloring of the pozzolan was a limiting factor to its use. Thus, the purpose of this application is to solve the problem of the many deposits of raw materials for the production of pozzolans that are red in color, or become red after calcination, making their use in cement manufacture impossible. The present application describes an alternative to changing the color of bauxite residues (Red mud ") from red to dark gray or black, such that the final color of the cement is not changed.

In view of the state-of-the-art documents, the main advantage of using this technology is that it can transform an environmentally toxic waste into a product of important commercial and social value such as Portland cement, thereby reducing pressure on the environment. environment in various areas, mining the cement, landfills for the aluminum plant, bringing strong benefits to society as a whole, and creating an important synergy between the cement and aluminum industries.

Description of the Figures

The invention will be better understood in the light of the accompanying figures, given by way of example only, but not limitation, in which:

- Fig 1: Flowchart of bauxite waste reuse. - Fig 2: Thermographic evaluation of the reduction of thermal consumption for the production of the active addition of red sludge when compared with a typical clinker flour.

- Fig 3: Red mud burn test in laboratory:

1 - sample of red mud;

2 - testing of the firing step in the laboratory;

3 - red mud at a temperature of 1250 ° C after burning.

- Fig 4: Photos of the pilot furnace specially designed and built for the development of this order, unique equipment in Brazil.

4 is a front view of the pilot oven;

5 is a side view of the pilot oven;

6 - active addition sample collected inside the pilot oven;

7 - end of batch - discharge of the material produced.

- Fig 5: Red sludge and its processing stages up to specimens, in which the color change of said red sludge can be verified after its processing, to evaluate the cement mixing performance.

8 - wet red mud

9 - dry red mud

10 - calcined red mud

11 - red mud with lime

12 - red mud with cement

- Fig. 6: Graphic of the qualification tests of the active addition made with red mud. IAP- with lime = pozzolanic activity index with lime. IAP-CAL = pozzolanic activity index with lime. IAP CIM = pozzolanic activity index with cement. MPA = mega Pascal. - Hg. 7: Performance graph of active addition in cement and concrete. MPA = mega Pascal.

- Fig 8: Graph of the results of the first bench tests to evaluate the performance of the active addition produced with RED-MUD against Brazilian Pozolana standards (active addition). The first tests were not satisfactory until the chemical composition and firing temperature were properly adjusted. The pilot furnace test (Figure 4) already contemplated the temperature and chemical composition adjustments, and for this reason the minimum standard requirements were met. As a result, the performance efficiency of the active addition thus produced in cements and concretes, whose results were satisfactory, and equivalent to those obtained when using typical pozzolans such as flyash, was evaluated. IAP = pozzolanic activity index.

- Fig. 9: Graph of the results of the performance evaluation of the active addition with cement and concrete, where it can be seen that the mechanical performance meets the needs of cement and concrete manufacturing and meets the requirements of the Brazilian cement standards. Mpa = Mega Pascal

Brief Description of the Invention

A process for obtaining a chemical composition for active addition production capable of replacing Portland clinker comprising the following steps:

(a) chemical treatment: to the bauxite processing residue is added limestone or calcium carbonate derivatives and sand or silica derivatives or silica clays until a S1O2> 30%, CaO> 10%% and α 2 O <10.0%; preferably S1O2 between 30 and 40%, CaO between 10 and 15%, and a2O between 4 and 6.0%;

(b) homogenization step: the mixture obtained in the previous item undergoes the homogenization process; (c) heat treatment: thereafter the mass of the mixture obtained in process (b) is heated to a temperature between 1000 ° C to 1500 ° C with partial melting and color change;

(d) cooling: the cooling process occurs in a satellite or grid chiller;

(e) final product: the final product is obtained when the color of the active addition is dark gray, with performance similar to ⁿ fly ash "e. the presence of free CaO is less than 1.0%;

(f) grinding: the final product is then subjected to the grinding process in conjunction with Portland cement clinker to produce cements containing the active addition according to Brazilian standard NBR 12653, and particle size in the range of 0.01 to 5 inches. size.

Detailed Description of the Invention

The bauxite residue named ⁿ red-mud 'has in its chemical composition high iron contents, which makes the material red intense.

It is known that not all bauxite residues can be transformed into pozzolans or in active addition only by the calcining effect, as the chemical compositions of the residues are very varied.

Thus, the technology proposed in the present invention differs from the others because it is mandatory to adjust the chemical composition of the waste, and after its calcination at high temperature in a preferential range from 1150 ° C to 1300 ° C, we have as The result is an active addition of a high performance dark gray color capable of partially replacing clinker without loss of mechanical performance in the cement and concrete resulting from its application. Thus, the process of obtaining the chemical composition for use of active addition of Portland clinker substituent becomes highly due to the fact that there is a reduction in the carbon emission of the cement produced with the partial replacement of the Portland clinker.

[0024] The technology of the present application is a process for obtaining chemical composition for active addition production comprising the following steps:

(a) chemical treatment: to the bauxite processing residue is added limestone or calcium carbonate derivatives and sand or silica derivatives or silica clays to a Si0 ₂ > 30%, CaO> 10%% content. and Na ₂ 0 <10.0%; preferably SiO ₂ between 30 and 40%, CaO between 10 and 15%, and Na ₂ O between 4 and 6.0%;

(b) homogenization step: the mixture obtained in the previous item undergoes the homogenization process;

(c) heat treatment: thereafter the mass of the mixture obtained in process (b) is heated to a temperature between 1000 ° C to 1500 ° C with partial melting and color change;

(d) cooling: the cooling process occurs in a satellite or grid chiller;

(e) final product: the final product is obtained when the color of the active addition is dark gray, with performance similar to fly ash and the presence of free CaO is less than 1.0%;

The composition comprising the bauxite processing residue has a SiO ₂ content> 30% and CaO> 10%, ie the SiO2: CaO ratio is 3: 1 and gray in color, similar to cement. . The end result is obtained by a mixture of red clay + limestone + silica clay + burning at a preferred temperature range of 1150 ° C to 1300 ° C, even more preferably 1250 ° C. This combination produces an active addition with characteristics suitable to Brazilian Standards (NBR 12653).

The correction of the chemical composition, the high firing temperature above 1150 ° C with partial melting of the material and color change, are the main innovations of this process in relation to existing technologies. The state of the art makes no mention of color change and firing temperatures above 1000 ° C, as existing technologies recommend burning of the material at temperatures of 500 ° C to 900 ° C.

[0028] The new product is a high performance active addition that allows up to 30% replacement of cement with satisfactory cement performance, significantly contributing to the reduction of carbon emissions from cement and concrete.

1. Chemical treatment of bauxite residue:

[0029] The process according to the invention departs from processing residues of bauxite or alumina which are generally reddish in color due to excess iron (Fe203) in the composition causing the material to turn red after burning. This coloration is a major barrier to its use in cement manufacturing, as this market is very conservative and strongly rejects any change in cement coloration.

The usual composition of this waste is also known by the name of red sludge (Vc mucf) and is generally disposed of as sludge in landfills. The basic chemical composition of this residue is mainly the components AI2O3, Fe203, S1O2, GaO and a20. Its coloring is due to the presence of iron ions, which in this case is about 20% of the composition of the red mud. It has now been found that in order to eliminate red staining and further improve the mineralogical properties of this residue its S1O2 content must be> 30% and CaO> 10%. For this purpose, to the alumina residue must be added limestone + clay of suitable chemical composition in such a way as to meet the aforementioned condition in a molar or mass ratio ranging from 10:30 to CaO and 30:50 of S1O2 or silicates. or sand in relation to the waste mass to be treated.

Preferably the a2O percentage of the alumina residue is reduced by chemical processing and filtration to values less than 6.0% by mass.

2. Homogenization step:

The mixture obtained in the previous item undergoes the homogenization process.

3. Heat Treatment:

The dough obtained in the homogenization process is introduced in a rotary oven and heated to a temperature greater than 1000 ° C or partial melting temperature, preferably between about 1150 ° C to 1500 ° C, even more preferably 1250 ° C. for more than 30 minutes or until the color turns from red to dark gray or black.

Partial fusion process is critical to ensure the pozzolanic property of the calcined material and also to correct the color of the active addition from red to dark gray and / or black, as well as to optimize the cooling process in satellite chillers. and / or grilles. The presence of 10 to 50% of liquid in the calcined material is fundamental to guarantee the above mentioned properties.

4. Cooling:

[0036] The cooling process takes place in either a satellite (cement kiln chiller type), or a grid (also a kiln chiller type) chiller. cement). After the product cooling step, it is collected in silos and / or covered deposits.

5. Final Product:

[0037] The final product is obtained when the color of the active addition is dark gray, with performance similar to ⁿ fly as "and the presence of free CaO is less than 1.0% and much of its mineralogical structure is amorphous. or not crystalline.

The coloration of the active addition is measured according to the CIE L * a * b * (CIELAB) colorimetric model. This model describes all colors visible to the human eye, where a color is located by three values: L (luminance, expressed as a percentage), where L = 0.0 refers to absolute black (colorless) and L = 100.0 refers to absolute white (reflects all colors); a and b are two color ranges ranging from green to red and blue to yellow respectively with values ranging from -120 to +120.

6. Grinding:

The final product is then subjected to the grinding process in conjunction with Portland cement clinker to produce cements containing the active addition according to the Brazilian standard NBR 12653, and particle size in the range of 0.01 to 5 inches in size.

Preferably, the composition of the active addition through the use of red mud is as follows in table 3 below:

In addition to limestone as a CaO supplier so that the minimum CaO percentage is greater than 10%, any CaO-containing source such as basic blast furnace slag, other industrial wastes such as lime sludge from CaO can be added. gas scrubbing and / or other sources of calcium.

Thus, the active addition composition of the present invention comprises bauxite processing residue having a S1O2 content> 30%, a CaO content> 10%, a Na2O content <6.0% and a maximum coloration of L = 10. at 50, preferably L = <40.

Thus, color correction using the addition of limestone + high calcination temperature corrected the problem, making it feasible to use existing raw materials in already open mining areas, thus avoiding the opening of new deposits to Longer distances from factories costing them and increasing CO2 emissions from transport over long distances, as well as preventing a large area from being contaminated, since dam pond soil is not recoverable and is useful for only 5 years .

Example 1:

Below is the comparative table between the chemical composition of the raw material of clinker manufacture called common raw flour and the active addition of the present invention. The flour referred to in this table is the raw material prior to calcination for the manufacture of Portland cement clinker.

Table 4: Comparison of the common flour chemical composition and active addition of the present invention.

Numerous bench tests were performed according to figures 3 to 7. The tests were performed to define the ideal chemical composition and temperatures to obtain the desired properties for the material (active addition). Thus, the pure red mud was calcined at temperatures of 500 ° C, and after each test the mineralogical compositions of the product formed and their performance as active addition were evaluated. Identifying the minimum chemical composition necessary to obtain the desired properties and the appropriate temperature to obtain the gray color, a pilot furnace test was performed (Figure 5), to obtain the material in larger scale in order to evaluate the performance of the active addition produced. in cement mixtures with 15% and 30% substitution percentages of Portland cement, evaluating the performance of active addition in cement and concrete in tests recommended by the Brazilian standards (Figure 7).

100% of red mud of the following composition was broken down to the final chemical composition (Figure 5, sub-item 12).

Table 5: Red mud composition and active addition composition of the present invention.

Example 3:

Eligibility tests for Brazilian NBR 12653 Standards of Active Addition manufactured with red mud (Table 6).

Test 1 - Red sludge heated to temperature> 1150 ° C. When evaluated according to NBR 12653, the test for measuring pozzolanic activity with lime was zero, when the minimum limit of NBR 12653 is 6.0 Mpa, indicating that the material thus produced is not a pozzolan. In cement testing, the value obtained was 74% of the reference value and the minimum norm value is 75.0%. Thus, it was confirmed in the previous test that the material is not a pozzolan capable of meeting the requirements of the Brazilian standard.

Test 2 - In the second test was added 20% silicose material to correct the percentage of red mud S1O2. After calcination under the same conditions as in test 1, the pozzolanic activity index with lime was evaluated and a value of 2.2 Mpa was obtained, when the minimum pozzolanic activity index is 6.0 Mpa. However, in the evaluation with cement, the value obtained was 84%, when the minimum limit is 75%; therefore, the product is only partially approved.

Test 3 - Due to the unsatisfactory results of tests 1 and 2, 10% limestone was added to the composition of test 2 in order to obtain a mixture with a minimum value of 30% S1O2 and 10% CaO. With this new composition and calcination under the same conditions of previous tests, material was obtained whose evaluation of the pozzolanic activity index with lime was 3.5 Mpa, and the pozzolanic activity index with cement was 94.4%, when the value minimum required by standard is 75.0%. Test 4 - For test # 4 the chemical composition of test # 3 was maintained, but the percentage of a20 was reduced from 12.0% to less than 6.0%, which was the change in the composition that was missing. so that the results to be obtained with the active addition allowed the fulfillment of the Brazilian norms. Thus, we can observe that the IAP (Pozoic Activity Index) with lime obtained in test No. 4 was 6.2 Mpa, and the minimum norm value is 6.0 Mpa. The IAP test (Pozoic Activity Index) with cement obtained in test No. 4 was 94% when the minimum of the Brazilian standard is 75.0%. Thus, these results confirm that the active admixture thus produced fully meets the requirements of Brazilian standards for this product to be able to partially replace Portland clinker in the manufacture of Portland cement.

Test No. 4 was carried out in a pilot kiln with the aim of producing a larger volume of material sufficient to perform the performance evaluation tests on cement and concrete. Figure 6 shows the evolution of results as a result of changes in chemical compositions.

We can evaluate the performance of active addition NBR 12653 in cement and concrete through the results obtained in the final tests of application of active addition of bauxite residues in cement and concrete manufacturing through Figure 7. Two evaluation tests were performed. of the active addition of bauxite residue in partial substitution to Portland clinker, replacing by 15% and 30%. The minimum results required by the Brazilian standards for both mixtures are mechanical strength obtained in standard mortar at 3 days, minimum of 10 Mpa (values obtained in the tests 15% = 27.7 MPa and 30% = 22.2 Mpa), mechanical resistances at 7 days, minimum of 20.0 Mpa (values obtained in the tests 15% = 31.4 Mpa and 30% = 25.7 Mpa), mechanical resistances at 28 days, minimum of 32.0 Mpa (values obtained we tests 15% = 37.8 Mpa and 30% 34.2 Mpa). Concrete performances do not need to meet the specific standard, however, they were compared with results obtained from similar cements produced with traditional pozzolans such as fly ash (fly ash, or ash produced in a power plant boiler), and the results obtained are equivalent. Therefore, it can be concluded that the active addition produced with the red mud of chemical composition corrected by the mentioned process meets all the requirements of the Brazilian pozzolan and cement standards, and allows the production of concretes with performance similar to the traditional pozzolans used. .

Claims

1. Process for obtaining chemical composition for active addition production capable of replacing Portland clinker characterized by the following steps:

(a) chemical treatment: to the bauxite processing residue is added limestone or calcium carbonate derivatives and sand or silica derivatives or silica clays until a S1O2> 30%, CaO> 10%% and a20 <10.0%; preferably S1O2 between 30 and 40%, CaO between 10 and 15%, and a20 between 4 and 6.0%;

(d) cooling: the cooling process occurs in a satellite or grid chiller;

(e) the end product: the end product is obtained when the active color is dark gray addition, with a similar performance ash ash FFY ⁿ "and the presence of free CaO is less than 1.0%;

Process according to Claim 1, characterized in that the alumina, CaO and S1O2 are added to the residue at a CaO: Si02 molar ratio which may vary from 10 to 30:30 to 50 with respect to the total mass to be treated. .

Process according to Claim 1, characterized in that the ratio of Si02: CaO is 3: 1, and Na20 <10.0%.

Process according to Claim 1, characterized in that the presence of free CaO is less than 2.0%, preferably between 0.5 and 1.0%, and much of its mineralogical structure is amorphous or non-crystalline. .

Process according to Claim 1, characterized in that the percentage of a20 of the alumina residue is reduced by chemical processing and filtration to values below 10.0 mass%, preferably between 2 and 6.0 mass%.

Process according to Claim 1, characterized in that the melting temperature is preferably from 1150 ° C to 1300 ° C for a period of time greater than 30 minutes or until the coloration turns from red to dark gray or Black

Chemical composition according to any one of the preceding claims, characterized in that it is a bauxite processing residue chemical composition for use in active addition with SiO 2> 30% and CaO> 10% and Na ₂ 0 <. 10.0% with change of its coloration from red to gray.

Chemical composition according to Claims 7 to 9, characterized in that the composition of the active addition consists of preferably from 9 to 12% CaO; 30 to 38% SiO ₂ ; 0.0 to 6.0% Na ₂ 0, relative to the total mass of the composition.

Chemical composition according to Claims 7 to 11, characterized in that the composition of the active additive consists even more preferably of: 11% CaO; 36% S1O2; <6% of a20.

Use of the chemical composition according to claims 7 to 11, characterized in that said composition can replace up to 30% Portland clinker in pozzolanic-type cements.