CN103951302A - Multipurpose high-calcium expansion clinker and ...

Embodiment Present inventor is through repetition test and performing creative labour, successfully developed can expand for multi-purpose high calcium ripe and preparation method thereof. The chemical reaction mechanism that high calcium expansive clinker is applied to other products is, grog and auxiliary material are manufactured to powder-like product, and with water mix, fCaO aquation becomes Ca (OH) 2, and strong heat release, produce volumetric expansion.The size expanding and the absolute content of fCaO are proportional.When f-CaO >=75%, the stress that this expansion forms is enough large, can breaking up rock, concrete structures, and produce the soundless demolishing agent of high efficiency of successful Multiple Type.When suitable minimizing clinker dosage, adjusting reduce f-CaO absolute content, this expansion can be controlled to optimum range, effective compensation concrete shrinkage, and produce the cement expansive material that successful full remuneration is shunk. For reach above-mentioned two kinds of uses simultaneously, principle of design of the present invention is as follows: The feature of grog provided by the present invention is that to take well-crystallized's fCaO be essential mineral, effective content>=75%; In addition, containing 8-12%C 3s, containing 8-13%C 4aF; And do not allow to exist C 3a mineral.Why do not allow C 3a exists, and to be the too fast aquation of soundless cracking agent in order preventing from manufacturing, to cause spray orifice; For the short loss of coagulating, cause slump of cement expansive material that prevents from manufacturing. In a kind of embodiment of the preparation method of grog of the present invention: first prepare high calcium expansion raw material, then use precalciner kiln mature calcined material.In raw material, the weight ratio of each raw material is Wingdale 95-98%, iron powder 2-5%; Require CaO>=54% in Wingdale, Fe in iron powder 2o 3>=70%; Do not allow to allocate into clay, bauxitic clay, gypsum etc. in raw material.In addition, Al in the raw material that use in the application 2o 3with Fe 2o 3bi Zhi≤0.64, to guarantee Al 2o 3only and Fe 2o 3form C 4aF and do not form C 3a, Fe 2o 3only form C 4aF and do not form CF.The present invention is why without clay, bauxitic clay, gypsum preparation raw material, be to guarantee there is higher fCaO effective content in the grog of preparation, and reduce while effectively preventing from calcining, skinning accident, effectively prevent the discharge of SO2 obnoxious flavour. It should be appreciated by those skilled in the art that when using limestone mine masonry to originate for calcium oxide, the calcium oxide content that it finally provides is relevant to calcium carbonate content and Wingdale grade wherein.In this application, iron powder refers to the iron ore through ore dressing.Iron ore is rhombohedral iron ore.Therefore, the present invention's raw material used this restriction can wait and be all following weight percent and define, the content of Wingdale is counted with CaO content: the content of 51.3-52.9%, iron powder is with Fe 2o 3content count 1.4-3.5%, each weight percent is all the gross weight based on Wingdale and iron powder.The distortion of foregoing description is all in spirit according to the invention. - ℃ of the suitable control calcining temperature of the present invention and liter weigh ± 50g/L, with being beneficial to fCaO, form good crystalline state, can as unslaked lime, not meet water and digest rapidly. In the present invention, in order to obtain the high calcium expansive clinker that meets above-mentioned requirements, calcining temperature is ± 20 ℃.For fear of mixing too much coal ash, and avoid producing reducing atmosphere, avoid or alleviate ring formation, must select the fat coal of ash content≤10%, volatile matter 30-35%, sulphur in ash content, alkali content should be low as far as possible. The device using in grog manufacture of the present invention does not have special requirement, can be rotary kiln, shaft kiln or tunnel furnace. Below in conjunction with specific embodiment, the present invention is described in more detail. The preparation of embodiment 1 high calcium expansive clinker Prepare the raw material of following mass percent: Wingdale 96%, iron powder 4%, wherein in Wingdale, the content of CaO is 54%, Fe in iron powder 2o 3content be 73%, Al 2o 3with Fe 2o 3ratio be 0.49, above-mentioned raw materials pulverizing, combined grinding are made to raw material, with precalciner kiln mature calcined material at ℃, calcining fuel used is coal, pit ash content is 9%, volatilizing is divided into 32%, and the mineral composition of resulting high calcium expansive clinker is as follows: the effective content 80% of fCaO; In addition, containing 9%C 3s, containing 11%C 4aF; And not containing C 3a mineral.The granular state of knot of this grog is 15mm, the heavy g/L of liter. Embodiment 2 Prepare the raw material of following mass percent: Wingdale 95%, iron powder 5%, wherein in Wingdale, the content of CaO is 60%, Fe in iron powder 2o 3content be 75%, Al 2o 3with Fe 2o 3ratio be 0.51, above-mentioned raw materials pulverizing, combined grinding are made to raw material, with precalciner kiln mature calcined material at ℃, calcining fuel used is coal, pit ash content is 10%, volatilizing is divided into 35%, and the mineral composition of resulting high calcium expansive clinker is as follows: the effective content 84% of fCaO; In addition, containing 10%C 3s, containing 8%C 4aF; And not containing C 3a mineral.The granular state of knot of this grog is 20mm, the heavy g/L of liter. Embodiment 3 Prepare the raw material of following mass percent: Wingdale 98%, iron powder 2%, wherein in Wingdale, the content of CaO is 62%, Fe in iron powder 2o 3content be 75%, Al 2o 3with Fe 2o 3ratio be 0.53, above-mentioned raw materials pulverizing, combined grinding are made to raw material, with precalciner kiln mature calcined material at ℃, calcining fuel used is coal, pit ash content is 8%, volatilizing is divided into 35%, and the mineral composition of resulting high calcium expansive clinker is as follows: the effective content 82% of fCaO; In addition, containing 12%C 3s, containing 10%C 4aF; And not containing C 3a mineral.The granular state of knot of this grog is 15mm, the heavy g/L of liter. One of application of embodiment 4 high calcium expansive clinkers With the high calcium expansive clinker that embodiment 1 obtains, manufacture high-grade soundless cracking agent.Decapacitation is produced I, the II of national Specification, outside the product of three models of III, the high heat beyond can also production standard, super I type, super III type product for extremely frigid zones; Expanded the Application Areas of product, specific product performance is in Table 1 Table 1 Two of the application of embodiment 5 high calcium expansive clinkers The full offset-type cement expansive material of manufacturing with the high calcium expansive clinker that embodiment 1 obtains, auxiliary material is sulfoaluminate clinker, Al 2o 3≤ 32%; Anhydrite, SO 3≤ 46%.Under standard test condition, in 7d water, limited expansion rate, all higher than standard index, can reach 5-10 * 10 -4, all>=0, compensation efficiency reaches 100% to the dry empty limited expansion rate of 21d.Shrinkage-compensating effect to the above high strength grade of C60 concrete is particularly outstanding, and the compensation efficiency of dry empty 28d reaches 80%～100%, during to an age period, still remains on more than 50%. The present invention is through practical proof, reliable, feasible.With high calcium expansive clinker provided by the invention, produce complete compensatory cement expansive material, swelling agent is for the reinforced concrete wall engineering of thick 40mm, long 400m, for sectional area 1m 2concrete filled steel tube engineering, for preparing cement based high-strength grouting material, for making the reinforced concrete member of self-stress value 1.2Mpa, all or success. The above embodiment is only the preferred embodiments of the present invention, and is not the exhaustive of the feasible enforcement of the present invention.For persons skilled in the art, any apparent change of under the prerequisite that does not deviate from the principle of the invention and spirit, it having been done, within all should being contemplated as falling with claim protection domain of the present invention.

Clinker is the primary material of cement, and it is called as semi-finished product. Clinker is a granulated material made of raw meal powder obtained by grinding limestone and clay together by sintering the raw meal in a rotary furnace at °C-°C degrees.

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Produced clinker’s mineralogical structure effects clinker’s grinding energy. And it determines the behavior of cement by changing the parameters such as strength and setting time.

Our post deals with clinker mineral structure’s grindability effects.

Figure 1: Gray Cement Clinker

Cement Production and Energy Consumption

Cement production is an energy-intense process and approximately one third of the energy required to produce one ton of cement is consumed during grinding of clinker and additive materials.

Cement industry is one of the biggest industries using almost 3.5% of the world’s energy. In cement industries, 40% of the total energy consumed during the production process is used for grinding.

Grindability in cement production is important due to two factors. First, cement’s properties depend on the fineness and grain size distribution of the cement other than chemical and mineralogical compound of it. Second; 1/3 of energy expense in cement cost is spent for grinding. 80% more energy is spent in grinding hard clinker compared to soft clinker.

Chemical Compound and Grindability

Chemical and mineralogical compound play an important role in the grindability of clinker.                      Grindability is observed to decrease with the increase of Silicate module, Aluminum oxide and free Calcium oxide determined through the chemical analysis of clinkers.                                                                                                                                           

Clinker Microstructure and Grindability

Microstructure also has an effect on grindability alongside chemical and mineralogical elements. Heating and cooling speeds and furnace type are also effective in the formation of microstructure. Fine crystalline structure, especially small calcium silicate crystals, improve grinding. Large crystals not only make breaking down difficult, but they also increase the number of breaking areas.

Formation of Clinker Melt in the Production Process

Raw meal powder enters into the furnace system, it transitions into the melt phase, and clinker is obtained once furnace and cooling reactions are completed.

The first melt phase is formed at °C-°C. Clinker melt’s rate increases as the temperature rises and it reaches up to 20-30% in weight at °C depending on the chemical compound.

These temperatures enable alite formation which is the main content of Portland cement. As soon as sintering starts, high amounts of free Calcium oxide along with belite come out. With the melt phase, Calcium oxide and belite enter into the solid solution.

The Effect of Clinker Cooling on the Microstructure in the Production Process

Reactions occur in the rotary furnace at °C-°C. Clinker should be cooled off rapidly once the reactions are completed. This process preserves the presence of alite which is the main phase of clinker. Belite and tricalcium aluminate phase emerges as a result of clinker melt entering into reaction with a certain proportion of alite due to slow cooling process. In addition, alite is not stable under °C and it tends to decompose into belite and free Calcium oxide. Therefore, clinker requires a cooling process fast enough not to allow these reactions.

High cooling speed has the following effects: Grinding improves due to stress cracks in clinker. No alite dissolution occurs and this phase has a high amount. The fine crystalline aluminate and ferrite phases formed by shock cooling of clinker slow down cement hardening.

Clinker Phases

Clinker phases emerge as a result of reactions which occur during sintering of raw meal powder in the rotary furnace. These phases affect the behavior of clinker, thus the behavior of cement. Main phases of typical Portland cement are as follows: Alite (Tricalcium Silicate-C3S), Belite (Dicalcium Silicate-C2S), C3A (Tricalcium aluminate), C4AF (Tetracalcium Alumina Ferrite) Grinding becomes difficult when Alite/Belite rate and (Alite+Belite)/(C3A+C4AF) decrease in clinker phases.

Figure 2: Clinker View Under Microscope

Clinker view under microscope: Crystals with brown corners are alite crystals. Blue circular crystals are belite crystals. Frays seen around the circles are called fingertype and they indicate that alite crystals transformed into belites by decaying as a result of slow cooling.In addition, the sizes of crystals are also assessed. Crystal size is effective in grinding energy.

Clinker Phase – Alite (C3S)

Alite may range between 40-70% of the clinker mass. It reacts with water, and it is the phase which controls cement strength and hydration temperature. If the cooling speed is not too slow under °C, it can preserve its stability down to normal temperatures. At very slow cooling speeds, however, some parts of alite dissolve and belite forms. This is the component with high hydration capacity as colorless crystals provide the first high strength in clinker. The quality of cement is measured by its alite concentration. Depending on cooling degrees, clinker’s alite rate reaches 59.8% in slow cooling, 65.2% in fast cooling, and 70% in express cooling.

Clinker Phase – Belite (C2S)

Belite may range between 15-45% of the clinker mass. It has a circular crystalline form. Its crystal size is between 5-40 μm. Belite is less reactive compared to alite and contributes to strength at later ages. It is a hydraulic binder which hardens slowly.

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Clinker Phase – Tricalcium Aluminate (C3A)

It may range between 1-15% of the clinker mass. It is in cubic or orthorhombic form. Its crystal size varies between 1-60 μm. Its reaction with water is very fast and amorphous in structure. Hydration temperature is very high. It hardens immediately with water.

Clinker Phase – Tetracalcium Alumina Ferrite (C4AF)

It may range between 0-18% of the clinker mass. Its crystalline structure is dendritic and prismatic. It presents a thin and long view in the form of a sword in the crystalline section.

Clinker Phases and Crystalline Structure

Clinker silicate crystals’ grain size may be put forth by calculating equivalent diameters. Equivalent diameter is determined by calculating the arithmetic mean of the longest and shortest lengths which pass through the center of gravity of the cross-sectional area in a crystal cross-section. Alite crystals with equivalent diameters of 15-20 μm have positive impacts on the ease of grinding of clinker as well as the early strength of the cement.

Belite crystals with equivalent diameters of 25-60 μm may be a result of insufficient grinding of quartz grains in the raw mixture or of heating-cooling regime.

In summary, examining grain size distributions of silicate crystals through polarizing optic microscope and image processing software would guide the manufacturer for the raw material choice and optimization of heating-cooling regime.

In Rapidly Cooled Clinkers: There are cracks on the alite crystals in hexagonal crystal structure which are formed due to thermal pressing during express cooling process. These cracks increase hydraulic activity and grindability capacity. Crystal ends are sharp in a clinker which was properly cooled.

The size and shapes of pores (porosity) provide information about sintering conditions in microscopic examinations of the clinker. High porosity and large, long, and interconnected pores may indicate that the clinker was not adequately sintered. Small and round pores, on the other hand, are a sign of a good sintering.

Alite Phase Amount and Grindability: Job index value (kwh/ton;) decreases with the increase of alite amount in the clinker. This shows us that the energy amount required for grinding decreased.

Figure 3: The Relationship Between the Amount % of Alite Phase (C3S) in Clinker and Grindability of Clinker

Belite Phase Amount and Grindability: When belite amount is below 20% in the clinker, the energy demand required for grindability decreases with the increase in belite %. However, in case there is a certain amount of belite (around 22%), the grindability energy demand increases once again.

Figure 4: The Relationship Between the Amount % of Belite Phase (C2S) in Clinker and Grindability of Clinker

Intermediate Phase (C3A and C4AF) Amount and Grindability: With an increase in the intermediate phase of more than 6 – 6.5 %, energy requirement (kwh/ton) for grindability is observed to decrease.

Figure 5: The Relationship Between the Amount % of Intermediate Phase (C3A+ C4AF) in Clinker and Grindability of Clinker

Porosity and Grindability: In contrast to literature, the required energy demand for grindability was observed to increase in parallel with the increase in porosity amount in the clinker. The reason for this is seen when porosity’s fineness module is examined.

Figure 6: The Relationship Between the Amount % of Porosity in Clinker and Grindability of Clinker

Table-1: Comparison of Silicate Phases and Porosity’s Fineness Modules in Clinker Samples with Job Indexes

Grindability becomes easier with high alite content in the clinker, and it becomes more difficult with high belite content. High amount of liquid phase makes grindability of clinker easier.

Cement behavior may be altered by conducting studies on clinker chemistry and mineralogical phases during clinker production process. Therefore, clinker grinding energy varies as well depending on the phase structure. Energy recovery may be obtained in grinding by bringing the phase structures to the desired levels.

References:

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