FR2760003A1 - Iron-rich cement clinker - Google Patents

Abstract

A novel iron-rich cement clinker contains bauxite waste (as red mud) and limestone or other calcium oxide-containing material. Also claimed are: (1) hydraulic cements which (i) are obtained from the above cement clinker; (ii) are produced from unwashed red mud and contain (by wt.) 9.60% SiO2, 6.80% Al2O3, 27.40% Fe2O3, 6.00% TiO2, 40.20% CaO, 3.42% MgO, 2.00% Na2O, 0.08% K2O, 1.57% loss on ignition and 0.32% moisture; and (iii) are produced from washed red mud and contain (by wt.) 9.52% SiO2, 6.00% Al2O3, 27.80% Fe2O3, 6.00% TiO2, 40.32% CaO, 3.60% MgO, 2.00% Na2O, 0.09% K2O, 1.70% loss on ignition and 0.29% moisture; and (2) production of iron-rich cement clinker from red mud and of hydraulic cements and mortars from this cement clinker by mixing 50-60% ground lime-containing material (below 150 mu m size) with 40-50% red mud, adding a wetting or leaching agent and granulating or pelleting, firing or sintering at 1175-1250 deg C for 5-120 min, cooling and grinding.

Description

 The present invention relates to a slag (or "clinker") of iron-rich cement, a hydraulic cement and a hydraulic mortar essentially consisting of red mud from bauxite waste and from materials containing calcium oxide. The invention also relates to a process for manufacturing an iron-rich cement slag and a hydraulic mortar or cement from the slag by using mixtures of red mud bauxite waste obtained during the production of alumina and d an aluminous material from bauxite by the Bayer process, and from limestone or the like containing calcium oxides. The product obtained by the process according to the present invention by suitable treatment of the abovementioned raw materials is mixed with organic and mineral materials giving products of high mechanical strength and of high density which have good bonding and cementing properties, for example setting time, consistency and maneuverability.

 In general, iron-rich cements contain iron oxide in amounts up to 45% by weight, and they are known as ferrite cements. The silica content is usually less than 20% by weight, the lime content is between 35 and 65% by weight, while the alumina content does not usually exceed 25% by weight. These cements are made from mixtures of clays containing iron oxide or iron ore from waste and limestone, and slag is usually produced between 1175 ct 1250-C. Cement, as is known in this field, has a low mechanical resistance due to a poor hydration character which is usually less than 10 MPa after twenty-eight days of hydration.

 The present invention essentially relates to a process for the preparation of an iron-rich cement having increased mechanical strength, that is to say greater than 10 MPa, by hydration, using red mud, if although the process is more cost effective and efficient.

 Another subject of the invention is the provision of a process for the preparation of a hydraulic cement from cement slags prepared from red mud, so that the protection of the environment in the vicinity of an industry aluminum manufacturing is improved.

 Thanks to the process of the invention, a general improvement in the quality of the product is obtained satisfactorily, scrvice performance and nature of the raw materials used, allowing cost reductions.

The invention relates to a process constituting an alternative for the manufacture of an iron-rich cement, containing approximately 25% by weight of fcr oxide, from red mud which contains significant amounts of impurities such as oxide. of titanium and soda.

The invention relates, in other aspects, to a method which facilitates:
(i) preparation of raw materials,
(ii) the preparation of mixers and agglomerates before sintering which facilitates information on the final sintering,
(iii) setting the temperature and sintering conditions,
(iv) treatment of the sintered material to obtain hydraulic cements,
(v) increasing the quality of the hydraulic cement by adding organic and mineral materials giving a hydraulic material of high and lasting mechanical strength,
(vi) the use of raw materials not used until now, that is to say red mud, for the manufacture of a product, so that the environmental conditions are better near a aluminum production plant that uses bauxite as a raw material, and
(vii) the provision of processing technology and its adaptation to industrial sectors working on a large scale, on a small scale or on a very small scale.

 These methods have been found to have the following advantages.

 (i) The use of a suitable proportion of red mud and limestone or any other material containing lime with impurity levels of less than 10%, generally adopted by the cement industry, with a ore ground to a small particle size, after sintering in the form of nodules or granules, gives a product with a hydraulic phase after sintering at temperatures between 1 200 and 1250 ° C. suitable for cements containing about 25 to 27% by weight of iron oxide.

 (ii) It was also found according to the invention that these red mud could be used directly with their normal content of impurity of carbonate of sodium hydroxide obtained in the installation during the manufacture of alumina from bauxite by the Bayer process. , or after treatment, as indicated according to the invention, that is to say preferably with reduction of the impurity of sodium carbonate to the extent necessary, by an additional treatment. In both cases, the product is a hydraulic cement.

 (iii) The use of organic compounds and adjuvants has been found to improve the hydraulic properties of the product, such as its setting time and its final strength.

 (iv) It has also been found that the use of mineral materials, such as high-yield slag and gypsum, modified the setting time and could in certain cases give greater mechanical resistance to the final product.

 (v) The process gives a quick setting cement which can be modified by adding organic and mineral additives.

 Thus, the present invention relates to an iron-rich cement slag comprising red mud waste from bauxite and limestone and the like containing calcium oxides.

 The invention also relates to a hydraulic cement or a mortar obtained from an iron-rich slag containing waste red mud from bauxite and limestone or the like containing calcium oxide.

 The invention also relates to a process for producing iron-rich cement slag and hydraulic mortars or cements from red mud, comprising grinding a material containing lime to a dimension less than 150 μm, the mixture from 50 to 60% of the ground material to 40 to 50% of red mud, the addition of a wetting or leaching agent and the formation of granules or nodules by known methods, cooking or sintering the granules -nodules resulting at a temperature between 1175 and 1250 C with a holding time between 5 and 120 min at maximum temperature, cooling to room temperature, and grinding of the sintered mass cooked to obtain the cement rich in iron.

 The wetting-leaching agent used in this process can in particular cut water.

 In addition, organic binders such as molasses, dextrin, starch and the like can also be added to the mixture.

 The composition of the ingredients of the iron-rich cement slag and that of the hydraulic cement are the same or more or less the same. The essential difference is the fineness, that is to say the reduction in particle size and / or the addition of additives in small quantities to the cement.

In a first embodiment, the invention relates to an improved process for the production of iron-rich cement slags and hydraulic cement powder, the process comprising mixing an assembly comprising:
(a) minerals containing calcium, having (i) 0.00 to 1.28% by weight of alumina, (ii) 0.01 to 3.46% by weight of silica, (iii) 0.22 to 1.16% by weight of iron oxide, (iv) 0.00 to 0.32% by weight of titanium oxide, (v) 1.42 to 2.56% by weight of magnesia, and (vi ) alkaline oxides in an amount not exceeding 0.5% by weight, their loss on ignition being between 34 and 44% by weight,
(b) an iron-rich material, such as red mud, containing (i) 4.0 to 8.3% by weight of silica, (ii) 20 to 29% by weight of alumina, (iii) 29 to 41% by weight of iron oxide, (iv) 7.7 to 17.6% by weight of titanium oxide, (v) 0.6 to 5.1% by weight of calcium oxide, (vi ) 11.09 to 0.77% by weight of alkaline materials, in particular sodium hydroxide, and (vii) a loss on ignition of between 0.38 and 15% by weight, with grinding of the calcareous material, mixing of the ingredients then formation of granules or nodules with the addition of wetting agents and organic binders allowing compression to configurations which can be easily sintered in a discontinuous manner or in continuous ovens, with sintering of the mass at temperatures between 1 175 and 1,250 ° C., then with mass cooling for the formation of an active material ready for use in the cement manufacturing technique, so that the cement slag produced is bro yé, by conventional methods. The method according to the invention is described in detail below.

Mixture of materials containing lime and red mud
An intimate and homogeneous mixture of materials containing lime and red mud is produced. The lime-containing material is first crushed and ground in jaw crushers and ball mills commonly used in the cement industry. The crushed material containing lime is mixed with dry red mud in the form of agglomerated dry lumps. The mixing is carried out in ball mills or in suitable ribbon mixers. The particle size of the mixture is preferably very small but not less than 100 µm. The range of compositions of the raw materials used and the composition of the product are indicated in Tables 1 and 2 which follow. However, these ranges do not include other conventional ingredients and impurities.

Table 1: composition of raw materials
Ingredients Red mud Limestone Fly ash
SiO2 7.29 0.82 60.16
2 3 29.25 1.28 23.83
Fe203 29.95 0.22 4.53
TiO2 9.40 0.32 1.30
CaO - 53.17 3.65
MgO - 1.42 1.23
Na2O 0.63 0.22 0.20
K2O - 0.08 1.82
Loss on ignition 15.29 42.20 3.28
Table 2. Chemical analysis of the product
(red mud cement!
I (with red mud II (with red mud
unwashed) washed)
SiO2 9.60 9.52
A1203 6.80 6.00
Fe2O3 27.40 27.80
TiO2 6.00 6.00
CaO 40.20 40.32
MgO 3.42 3.60
Na2O 2.00 2.00
K2O 0.08 0.09
Loss on ignition 1.57 1.70
Humidity 0.32 0.29
Granulation of the mixture of materials containing lime and red goats
After mixing, the mass is granulated using a tableting press or formed into nodules by agglomeration apparatus for the production of granules having a thickness of approximately 20 mm or of nodules having a diameter of 8 to 121 mm approximately. During granulation, a suitable binder, generally organic with a low ash content, is mixed with water. The granules are dried or preheated before sintering. The binders usually used in this operation are molasses, dextrin, starch or organic gums. Oven waste dust cement can also be used.

Adjustment of the premix composition according to the cooking atmosphere
In the case of sintering carried out in a liquid fuel cooking atmosphere, fly ash or coal ash mix with the composition formed from red mud and lime. Coal ash or fly ash may have a diameter of less than about 0.500 mm and preferably less than 0.150 mm. The composition of the ash contains (i) 55 to 62% by weight of silica, (ii) 15 to 28% of alumina, (iii) 3 to 8% by weight of iron oxide, and (iv) 2 to 55 % by weight of lime. In the case of units heated with pulverized coal, it is not necessary to mix the ashes with the raw materials beforehand, before granulation. The ash from the pulverized coal enters the cement during the firing process.

Cooking of granules or nodules of raw materials in the form of a premix
The cooking of raw materials in granulated or nodulized form is intended to be carried out at a temperature of between 1,175 and 1,250 ° C. with a time for maintaining at the maximum temperature of between 5 and 120 min. The furnace can be small or large, of the discontinuous or continuous type, with liquid, gas, electric or coal fuel, with air circulation in the furnace, or a static atmosphere of air can be present in the furnace. In the currently preferred method, the material to be cooked is intended to be removed-cooled from the batch or rotary oven at a temperature of 800 to 850 ° C. after the end of the sintering. However, the product can also be prepared by slow deceleration of the product.

Dimensioning of the fired material to the fineness of the cement
The nodules or granules compressed and sintered after cooling to room temperature, either by quenching or by cooling from the elevated temperature, are intended to be crushed and ground in an apparatus used in the art such as jaw crushers, cylinder crushers and ball mills which can be of the continuous or discontinuous type. The product is intended to be crushed and ground to a particle diameter of less than about 0.150 mm and preferably has a specific surface, measured by the Blaine technique used in the cement industry, of at least 3000 cm2 / g. The treatment waste can be recycled into a new composition so that the granules have greater mechanical strength.

 The powdered product is intended to be mixed with dry organic or mineral materials suitable for adjusting the setting time and the hydraulic property, and they are then stored by airtight packaging in the absence of moisture, for example in drums or plastic bags intended to protect the product from attack by humidity. Setting agents can also be added in liquid form when the hydraulic material is made from cement.

 Iron-rich cement in fine powder when mixed with water and organic and mineral materials, if necessary, hardens to form a hard mass. The setting time can be set between zero and 240 min, and the mechanical strength after seven days of hardening can be between 0.4 and 14.6 MPa. Cement can also be formed with sand in the amount of one part by weight of cement for three parts by weight of sand and 0.4 part of water, giving mechanical strengths after seven days up to 22.7 MPa with suitable organic or mineral additives. As indicated in the cement technique, it is also possible to produce concretes with coarse aggregates such as crushed stones, sand and cement in proportions of 4, 2 and 1 parts, with 0.5 part of water.

 The invention will now be described with reference to the examples which follow dc implementation of the invention cn practical. However, these examples do not limit the scope of the invention.

Example 1
40 parts by weight of red mud and 60 parts by weight of limestone are mixed after grinding the limestone so that they pass through a sieve with orifices of 0.150 mm. The mixture is compressed in the form of granules at a pressure of 100 to 1120 bar after humidification with water at the rate of 11% by weight, before drying at 110 ° C. The material is then cooked at 1,200 + 25 ° C, then preferably by maintaining the temperature at 1,200 'C, and the moisture content is then reduced to approximately 3% by weight by prior drying in a batch type oven. .

 The sintered mass is removed from the oven at approximately 800 ° C., then is cooled in air and then cooled to room temperature. The product is ground in a ball mill, a pot mill or a vibratory energy mill so that the material passes through a sieve with orifices of 0.075 mm, with a specific Blaine surface of approximately 3000 cm2 / g, giving a cementitious product.

Example2
40 parts by weight of red mud and 63 parts by weight of limestone, as in Example 1, were mixed with an additional 5 parts by weight of fly ash from a thermal power plant. The material is mixed with approximately 7 to 9% by weight of water containing 3 to 5% by weight of organic binder such as dextrin, molasses or starch. The mass is nodulated in a nodule making machine and is dried at approximately 150 ° C. to a moisture content which does not exceed 3% by weight. The nodules are transmitted to a continuous rotary type oven with a maximum temperature maintained at 1,200 + 25 ° C, preferably around 1,200in. The nodules can come out of the oven at a temperature between 750 and 850 C and are quenched in air.

 The cooked nodules are ground in ball mills to a fineness less than that which gives a specific surface of 3000 cm2 / g and the cement is thus obtained. The main mineral phases are calcium aluminoferrite, calcium aluminate, calcium silicate and calcium aluminosilicates containing iron, known in the art as gehelimite, and calcium titanate.

Example 3
Red mud is washed in tap water. Washing is carried out by disposing of the red mud in water for 24 hours and then by removing the water. The operation reduces the soda ash content of the red mud. Red mud washed with tap water having a reduced soda content at the rate of 40 parts by weight is mixed with 63 parts by weight of ground limestone and 5 parts by weight of fly ash for the formation of a mass of material. first analogous to that of Example 2. The material is treated as described in Example 2 and gives a cement having reduced amounts of iron incorporated into the calcium aluminosilicates.

Example 4
Red mud washed with tap water and having a reduced sodium hydroxide content at the rate of 40 parts by weight is mixed with 60 parts by weight of crushed limestone to form a mass of raw material similar to that of Example 1. The material is treated as described in Example 1 and gives a cement having phases of calcium aluminoferrite, calcium aluminate and calcium aluminosilicate and calcium titanate.

Example 5
An iron-rich cement powder produced in Example 2 in an amount of 100 parts by weight is mixed with 40 parts by weight of water in a paddle mixer. For this purpose, 2% of citric acid adjuvant is added and the paste is shaped so that it takes 45 minutes. The resistance obtained after seven days is 23 MPa by compression.

Example 6
50 parts by weight of an iron-rich cement powder produced in Example 3 are mixed with 50 parts by weight of cooled and finely ground blast furnace slag powder having a size of less than 75 m, and the mass is mixed to 40 parts by weight of water. The addition of 0.5 part by weight of citric acid adjuvant and 0.5 part by weight of lithium chloride salt adjuvant is carried out with water. The product gives a mechanical resistance of 15 MPa in compression after seven days of hydration including six days underwater.

Example 7
100 parts by weight of iron-rich cement produced in Examples 1 to 5 are mixed with 300 parts by weight of sand. The mixture is combined with 3 parts by weight of gypsum and 40 parts by weight of water in a paddle mixer for 2 min and then poured into blocks. The blocks give a mechanical resistance of 6 MPa by compression after twenty-eight days of storage, including twenty-seven days underwater.

Example 8
100 parts by weight of iron rich cement produced in cxcmples 1 to 5 are mixed with 300 parts by weight of normal sand composed of three fractions, 100 parts by weight of each of qualities I, II and III as defined in the art , preferably, quality I has dimensions greater than 1 mm, quality II dimensions less than 1 mm and greater than 500 Hm and quality III dimensions less than 500 hum. This mixture is associated with 45 parts by weight of water and 0.2 parts by weight of sodium citrate and the mass can then harden. The setting time is approximately 20 min and the mechanical strength by compression after twenty-eight days of storage, including twenty-seven days underwater, is 6.9 MPa.

Example 9
An iron-rich cement produced as described in Example 3, in an amount of 100 parts by weight, was mixed with 300 parts by weight of normal sand described in Example 8 and 2 parts by weight of calcium saccharate and 45 parts by weight of water in a paddle mixer. The mass takes 15 min and gives a compression resistance of 12.4 MPa after seven days of hydration, including six days underwater.

Example 10
100 parts by weight of an iron-rich cement produced as described in Example 3 are mixed with 200 parts by weight of sand and 400 parts by weight of crushed stones. 0.15 part by weight of sorbitol and 0.1 part by weight of citric acid are then added with 55 parts by weight and the mixture is mixed for 2 min. The mass takes 20 minutes and the mechanical resistance after twenty-eight days of hydration, including twenty-seven days underwater, is 6 MPa.

Claims (11)

 1. Iron-rich cement slag, characterized in that it contains bauxite waste in the form of red mud and limestone or other materials containing calcium oxides.  calcium.  red and limestone or the like containing oxide  characterized in that it comprises bauxite waste in the form of sludge  2 Hydraulic cement obtained from an iron-rich slag,  3. Hydraulic cement, characterized in that it is produced from  unwashed red mud, cement containing the following ingredients in  weight percentages:  SiO2 9.60  A1203 6.80  Fe203 27.40  Ti02 6.00  CaO 40.20  MgO 3.42  Na2O 2.00  K2O 0.08  Loss on ignition 1.57  Humidity 0.32  4. Hydraulic cement, characterized in that it is produced from  washed red mud, and that it contains the following ingredients in percentages by weight:  SiO2 9.60 9.52  2 3 6.80 6.00  Irons3 27.40 27.80  TiO2 6.00 6.00  CaO 40.20 40.32  MgO 3.42 3.60  Na2O 2.00 2.00  K2O 0.08 0.09  Loss on ignition 1.57 1.70  Humidity 0.32 0.29  5. A method of manufacturing an iron-rich cement slag and hydraulic cements or mortars from slag, from red mud, characterized in that it comprises grinding a material containing lime to a dimension less than 150 μm, the thorough mixing of 50 to 60% of the ground material with 40 to 50% of red mud, the addition of a wetting or leaching agent and the formation of granules or nodules by known methods, addition or sintering of the granules or nodules at a temperature between 1,175 and 1,250 ° C, with a holding time of 5 to 120 min at the maximum temperature, cooling to room temperature, and grinding the cooked mass- sintered for the formation of iron-rich cement slag.  6. Method according to claim 5, characterized in that the leaching agent is water.  7. Method according to claim 5, characterized in that binders used are chosen from molasses, dextrin, starch, organic gums and cement dust from oven waste.  8. Method according to claim 5, characterized in that the red mud is mixed with 0 to 5% by weight of fly ash or of coal when the sintering-cooking is carried out in an atmosphere obtained with a liquid fuel.  9. Method according to claim 5, characterized in that the sintered product is ground to a particle size of less than 0.150 mm.  10. Method according to claim 5, characterized in that it is intended for the preparation of a hydraulic cement, associated with conventional mineral organic materials and dc water.  11. Method according to claim 5, characterized in that the red mud used is washed with water so that the carbonate content of sodium hydroxide is reduced before mixing with the materials containing lime.