CN104556753A - Steel slag cement - Google Patents

Abstract

The invention discloses a steel slag cement. The raw material of the steel slag cement is composed of the following components by weight percentage: 80-95% of cement raw material; 5-20% of steel slag; wherein the cement raw material is ordinary portland cement For the raw meal, the particle size of the steel slag is 5mm-30mm. The steel slag cement of the invention reduces cost and has high quality.

Description

a steel slag cement

technical field

The invention relates to the technical field of cement, in particular to a steel slag cement.

Background technique

The main composition of steel slag is the same as that of cement, and its mineral phase is also similar. Therefore, some people have proposed to use steel slag as a raw material for cement production. At the same time, there is a certain amount of iron in steel slag, which can replace part of iron in cement production. pink.

As a by-product of steel production, steel slag has a large output. The accumulation of steel slag occupies a large amount of land. On the other hand, the silicon, manganese, phosphorus, sulfur and other substances in steel slag seep into the ground, which will also cause damage to the environment. Therefore, using steel slag as a raw material for cement production is to use the steel slag produced in steel production for waste utilization, which is an effective means for sustainable development and circular economy development, so that environmental protection and economic development can be coordinated. However, although the components of steel slag and cement are similar, the activity of steel slag is extremely low due to the difference in mineral phases. Therefore, how to stimulate the potential gelling performance of steel slag and ensure the economy of steel slag reuse and reduce energy consumption , is the key to the recycling of steel slag.

Steel slag itself has no independent water activity, but the potential activity of steel slag can be effectively stimulated by physical and chemical means. At present, in the cement production process in the prior art, the steel slag is ground to replace a part of the iron powder and calcined together with the raw meal. However, due to the low liquid phase temperature of the steel slag, it is easy to cause the problem of crusting in the rotary kiln. A corresponding production process is formed. At the same time, due to the high requirement for fineness, the pre-grinding of steel slag also causes a large increase in production cost. Therefore, the use of steel slag to produce cement in the prior art has problems such as high cost and poor quality, resulting in crusting of the rotary kiln.

Contents of the invention

In view of this, an embodiment of the present invention provides a steel slag cement, the main purpose of which is to reduce costs and improve quality.

In order to achieve the above object, the present invention mainly provides the following technical solutions:

On the one hand, the embodiment of the present invention provides a kind of steel slag cement, its raw material is composed of the following components by weight percent:

Cement raw meal 80-95%;

Steel slag 5～20%;

The cement raw meal is ordinary Portland cement raw meal, and the particle size of the steel slag is 5mm-30mm.

As a preference, the steel slag cement is calcined with a cement rotary kiln, wherein an opening is added at the tail of the cement rotary kiln at the far end of the fire, and the steel slag is added to the cement rotary kiln through the increased opening at the kiln tail, and the steel slag gradually moves toward the cement rotary kiln. The fire end moves and the partially molten steel slag is mixed with other raw materials in the kiln.

Preferably, the gradient of the cement rotary kiln is 3.5-4.0%, and the rotation speed is 3.0-4.0r/s.

As a preference, the maximum temperature of the gas in the cement rotary kiln cannot be lower than 1500°C, and the maximum surface temperature of the cement raw meal and steel slag is not lower than 1400°C.

Preferably, the amount of liquid phase is controlled between 20% and 30% during the calcination process.

As a preference, the decomposition rate of the cement raw meal is 90-95%, the fuel can be completely burned in the calciner and the rotary kiln, the temperature in the tertiary air pipe is 18-22m/s, and the primary air volume of the multi-channel coal pipe accounts for the theoretical air demand. The proportion of the amount should not be greater than 15%.

Compared with prior art, the beneficial effect of the present invention is:

The steel slag cement of the embodiment of the present invention adds granular steel slag on the basis of the existing common Portland cement raw material, without grinding, thus ensuring low cost. In addition, by adding steel slag at the kiln tail, the steel slag gradually moves to the fire end in the kiln, and the steel slag is partially melted and mixed with other raw materials in the kiln to produce Portland cement. During the calcination process, the crystal form of the steel slag is changed to increase the activity of the steel slag through high-temperature reconstruction, and the reaction and recombination between the steel slag and the cement raw material occur, and the activity of the steel slag is significantly improved. The liquid phase of the mixture in the furnace can be adjusted by adding steel slag particle size to prevent the problem of crusting in the rotary kiln due to the reduction of the eutectic point of the mixture due to the addition of steel slag.

Detailed ways

The present invention will be described in further detail below in conjunction with specific examples, but not as a limitation of the present invention. In the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, the particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

The contents in the examples of the present invention are all weight percentages.

Example 1

The ordinary Portland cement raw meal is calcined in the cement rotary kiln, and an opening is added at the end of the cement rotary kiln at the far end of the fire, and steel slag is added to the cement rotary kiln through the opening at the end of the kiln, and the steel slag gradually moves closer to the cement rotary kiln. The fire end is moved, and the steel slag is partially melted and mixed with other raw materials in the kiln to finally obtain steel slag cement. The cement raw meal is composed of limestone, clay and iron powder. The specific ratio of raw materials is: limestone 74.1%, clay 18%, iron powder 2.9%, steel slag 5%. The particle size range of steel slag is between 5mm-30mm. The slope of the cement rotary kiln is 3.5-4.0%, and the rotation speed is 3.0-4.0r/s to ensure that the steel slag and cement raw materials are fully mixed and even. The maximum temperature of the gas in the cement rotary kiln cannot be lower than 1500°C, and the maximum temperature of the surface of the cement raw meal and steel slag is not lower than 1400°C, to ensure the temperature required for the change of the mineral phase of the steel slag itself and the reaction with the cement raw meal at the interface. The amount of liquid phase is controlled between 20% and 30% during the calcination process to ensure that no skinning of the kiln is caused. The decomposition rate of cement raw meal is 90-95%. The fuel can be completely burned in the calciner and rotary kiln. The temperature in the tertiary air pipe is 18-22m/s. The ratio of the primary air volume of the multi-channel coal pipe to the theoretical air demand is not greater than 15%.

Example 2

The difference between this embodiment and embodiment 1 is that the specific ratio of raw materials is: limestone 70.2%, clay 17.1%, iron powder 2.7%, steel slag 10%.

Example 3

The difference between this embodiment and embodiment 1 is that the specific ratio of raw materials is: 66.3% of limestone, 16.1% of clay, 2.6% of iron powder, and 15% of steel slag.

Example 4

The difference between this embodiment and embodiment 1 is that the specific ratio of raw materials is: 62.4% of limestone, 15.2% of clay, 2.4% of iron powder, and 20% of steel slag.

In the embodiment of the present invention, the clinker rate value is set to be between 0.90-0.92 for the limestone saturation coefficient (KH). Cement raw materials, that is, limestone, clay, iron powder (using iron tailings) three raw materials are pre-ground before cement firing, the grinding fineness is less than 8% in the 80um square hole sieve, and the steel slag is not The powder is passed through a square hole sieve, and the granular steel slag with a particle size of 5mm to 30mm is sieved. After the calcination is completed, the mixture is cooled by a grate cooler, and the temperature of the clinker leaving the cooler is not higher than the ambient temperature of 70°C.

Next, the cement raw meal without steel slag is used as a comparative example to test the compressive strength of the cement clinker mortar specimens of the embodiment of the present invention and the comparative example. See Table 1 below for details. Wherein the ratio of comparative example is limestone 78%, clay 19%, iron powder 3%.

Table 1

As can be seen from Table 1, the performance of the steel slag cement obtained in the embodiment of the present invention is basically the same as that of the existing ordinary Portland cement, but the cost of the embodiment of the present invention is far lower than that of the existing ordinary Portland cement, and A large amount of steel slag as waste can be consumed, which protects the environment.

In addition, after comparison, it is found that the fineness and dosage of steel slag affect its clinker mineral types, mineral content and hydration properties, as follows:

Compared with the existing blending of steel slag after grinding, the blending of steel slag in the form of coarse particles in the embodiment of the present invention can reduce the firing temperature of clinker, increase the amount of liquid phase, and promote the absorption of free calcium oxide. And because the steel slag has poor grindability, it needs a lot of energy consumption to grind it into a powder form. In addition, the embodiments of the present invention control the particle size of steel slag, which can control the amount of liquid phase in the cement rotary kiln.

After X-ray diffraction and infrared spectrum analysis, it is found that after the steel slag is mixed with coarse particles in the embodiment of the present invention, the content of the iron-aluminum phase increases, which can easily replace the silicon phase in the steel slag, and generate more calcium aluminate and calcium aluminoferrite .

According to X-ray diffraction and heat of hydration analysis, after the steel slag is mixed with coarse particles in the embodiment of the present invention, the C2S and C3S brought in by it can play the role of crystal seeds in the firing process of clinker, promoting the C2S And the formation of C3S, the growth rate increases, and the crystal particle size increases, which causes the exothermic peak of the hydration reaction to be delayed and the heat release to decrease. The incorporation of coarse-grained steel slag is beneficial to the preparation of low-heat cement.

The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Anyone skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present invention. Should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (6)

1. a steel slag cement, is characterized in that, its raw material is very made up of by weight following component:

Cement slurry 80 ~ 95%;

Slag 5 ~ 20%; Wherein

Described cement slurry is ordinary Portland cement raw material, and the particle diameter of described slag is 5mm-30mm.

2. steel slag cement according to claim 1, it is characterized in that, described steel slag cement cement rotary kiln is calcined, wherein increase opening at the cement rotary kiln tail being positioned at fire end far away, the opening that slag increases from kiln tail is added cement rotary kiln, slag moves to nearly fire end gradually in cement rotary kiln, and mixes with other starting material in kiln after slag partial melting.

3. steel slag cement according to claim 2, is characterized in that, the gradient of described cement rotary kiln is 3.5-4.0%, and rotating speed is 3.0-4.0r/s.

4. steel slag cement according to claim 2, is characterized in that, in described cement rotary kiln, maximum gas temperature can not lower than 1500 DEG C, and cement slurry and slag hot face temperature are not less than 1400 DEG C.

5. steel slag cement according to claim 2, is characterized in that, in control calcination process, amount of liquid phase is between 20%-30%.

6. steel slag cement according to claim 2, it is characterized in that, described cement slurry rate of decomposition is 90-95%, fuel is energy perfect combustion in decomposing furnace and rotary kiln, in tertiary-air pipe, temperature is 18-22m/s, and the ratio of the primary air flow reasonable opinion air requirement of Multi-channel coal pipe should not be greater than 15%.