1. The thermal state calcium-added modified stainless steel slag is characterized in that 80-95 wt% of stainless steel slag and 5-20 wt% of calcium oxide are heated in a high-temperature furnace to react to generate the modified stainless steel slag, and the preparation method comprises the following steps:

preparing a mixture: mixing stainless steel slag and calcium oxide to form a mixture A;

(2) and (3) pressing and forming: pressing the mixture a into a material cake b with the diameter of 30mm and the thickness of 8mm by using a die with the inner diameter of 30mm and pressurizing for 10 seconds under the pressure of 50 kN;

(3) and (3) calcining: placing the pressed material cake b into a high-temperature furnace, and calcining at 1225-1275 ℃ for 100-200 min to form a material cake c;

(4) quenching: cooling the material cake C generated in the step (3) in a high-temperature furnace, taking out the material cake C when the temperature is reduced to 700 ℃, and rapidly cooling the material cake C to room temperature;

(5) milling: grinding the material cake c by using a disc grinder and a ball mill until the specific surface area is 320-²Per kg, obtaining modified stainless steel slag powder; after grinding, putting the modified stainless steel slag powder into a drying box, and drying at 105 ℃ to constant weight; then adding 5 percent of dihydrate gypsum, and uniformly mixing to obtain the thermal state calcium-added modified stainless steel slag.

2. The thermal state calcium-added modified stainless steel slag according to claim 1, which is characterized in that: the stainless steel slag comprises the following main chemical components in percentage by mass: 43.72-47.72% of CaO and SiO₂ 29.65%~33.65%、MnO₂ 4.72%~6.84%、MgO 4.72%~5.82%、Cr₂O₃ 1.03%~1.96%、Al₂O₃ 1.03%~1.76%、Fe₂O₃ 0.15%~0.98%。

3. The thermal state calcium-added modified stainless steel slag according to claim 1, which is characterized in that: before mixing, the stainless steel slag is ground into 350kg/m specific surface area by a disc grinder and a ball mill³The stainless steel slag powder is put into a drying box and dried to constant weight at 105 ℃.

4. The thermal state calcium-added modified stainless steel slag according to claim 1, which is characterized in that: the calcium oxide contains 97-99% of CaO by mass and has a particle size of less than 1 mm.

5. The thermal state calcium-added modified stainless steel slag according to claim 1, which is characterized in that: and (4) quenching in the step (4) is specifically to blow by a high-power electric fan at room temperature after being taken out, and the cooling rate is kept at 120 and 140 ℃/min.

6. A use method of thermal state calcium-enriched modified stainless steel slag is characterized in that: mixing the thermal state calcium-enriched modified stainless steel slag of any one of claims 1 to 8 with cement in a ratio of 3: 7, mixing uniformly.

Background

The steel slag is solid waste obtained by cooling molten waste with the temperature above 1400 ℃ in the steel making process. The discharge amount of the steel slag is about 10-15% of the steel yield. According to the data of the national statistical bureau, the yield of the crude steel in China in 2017 is 83172.8 ten thousand tons, and the yield is increased by 5.7 percent on the same scale, so the yield of the steel slag in 2017 is about 10812.5 ten thousand tons. In the state 'fifteen-over-ten development plan', the comprehensive utilization rate of the steel slag is required to reach more than 86%, zero emission is basically realized, however, the current situation of the Chinese comprehensive utilization is far away from the plan, so far, the comprehensive utilization rate of the steel slag is only 30%, and a great space is provided for improvement.

The steel slag is only randomly piled due to large production amount and low utilization rate, which not only occupies a large amount of land, but also causes great pollution to the environment. Firstly, heavy metal ions and alkali metal ions contained in the steel slag can permeate into soil along with rainwater, so that the property of the soil is changed, and the growth of crops is influenced; harmful ions in the steel slag permeate into underground water, so that nearby water bodies are polluted, and the health of people is further influenced; and the dust generated after the stacked steel slag is naturally pulverized can also float into the air, which not only causes pollution to the atmospheric environment, but also causes harm to the health of human beings.

The internal reasons for the low utilization of steel slag are its complex composition, low activity and poor stability. At present, the research on the activity excitation of the steel slag in China is only limited to end modification, namely, the optimization and the promotion of specific physical properties such as fineness, morphology and gradation are only carried out on the steel slag consisting of given minerals, or the improvement is only carried out on the hydration environment of steel slag micro powder, but the low activity of the steel slag is not realized to be mainly related to the formation of the steel slag. The steel slag is formed in a complex multi-liquid phase environment, the formed crystals are complete, the defects are few, and a large amount of impurity minerals are contained, so that the hydration activity of the steel slag is low. And the steel slag has high alkalinity, and the slag contains a large amount of f-CaO and f-MgO, so that the volume of the steel slag is unstable.

Disclosure of Invention

The invention provides thermal-state calcium-increasing modified stainless steel slag and a using method thereof, and solves the problems of low hydration activity and unstable volume of the conventional steel slag.

In order to solve the technical problem, the technical scheme of the invention is realized as follows:

the thermal state calcium-added modified stainless steel slag is prepared by heating 80-95 wt% of stainless steel slag and 5-20 wt% of calcium oxide in a high temperature furnace to react to generate modified stainless steel slag, and the preparation method comprises the following steps:

(1) preparing a mixture: mixing stainless steel slag and calcium oxide to form a mixture A;

(2) and (3) pressing and forming: pressing the mixture a into a material cake b with the diameter of 30mm and the thickness of 8mm by using a die with the inner diameter of 30mm and pressurizing for 10 seconds under the pressure of 50 kN;

(3) and (3) calcining: placing the pressed material cake b into a high-temperature furnace, and calcining at 1225-1275 ℃ for 100-200 min to form a material cake c; the cake c has a micro-melting phenomenon in the temperature range, which proves that the stainless steel slag powder a and the analytically pure calcium oxide have a solid-phase reaction, if the temperature is lower than the temperature range, the stainless steel slag powder a and the analytically pure calcium oxide can have incomplete reaction to generate more other unrelated minerals, and if the temperature is higher than the temperature range, the stainless steel slag powder a and the analytically pure calcium oxide can have a melting phenomenon and are adhered to a crucible;

(4) quenching: cooling the material cake C generated in the step (3) in a high-temperature furnace, taking out the material cake C when the temperature is reduced to 700 ℃, and rapidly cooling the material cake C to room temperature;

(5) milling: grinding the material cake c by using a disc grinder and a ball mill until the specific surface area is 320-²Per kg, obtaining modified stainless steel slag powder; after grinding, putting the modified stainless steel slag powder into a drying box, and drying at 105 ℃ to constant weight; then adding 5 percent of dihydrate gypsum, and uniformly mixing to obtain the thermal state calcium-added modified stainless steel slag.

Preferably, the stainless steel slag comprises the following main chemical components in percentage by mass: 43.72-47.72% of CaO and SiO₂ 29.65%~33.65%、MnO₂ 4.72%~6.84%、MgO 4.72%~5.82%、Cr₂O₃ 1.03%~1.96%、Al₂O₃ 1.03%~1.76%、Fe₂O₃ 0.15%~0.98%。

Wherein, preferably, the stainless steel slag is ground into the specific surface area of 350kg/m by a disc grinder and a ball mill before being mixed³The stainless steel slag powder is put into a drying box and dried to constant weight at 105 ℃.

Wherein, preferably, the CaO content in the calcium oxide is 97-99% by mass, and the grain diameter is less than 1 mm.

Wherein, preferably, the quenching in the step (4) is specifically to blow by a high-power electric fan at room temperature after being taken out, and the cooling rate is kept at 120-.

A using method of thermal state calcium-increasing modified stainless steel slag comprises the following steps of mixing the thermal state calcium-increasing modified stainless steel slag and cement in a proportion of 3: 7, mixing uniformly.

The modification principle of the modified carbon steel slag is as follows:

10CaO+SiO₂+6Al₂O₃+Fe₂O₃＝3CaO·3Al₂O₃·CaSO₄(calcium sulphoaluminate) +2 CaO. SiO₂(dicalcium silicate) +4CaO 3Al₂O₃·Fe₂O₃(tetracalcium aluminoferrite)

The three minerals in the reaction formula are all minerals with high gelling activity. In addition, tricalcium silicate is the main gelling mineral in ordinary portland cement, and the reaction formula is as follows:

3CaO+SiO₂＝3CaO·SiO₂

however, tricalcium silicate can only exist stably at 1250 ℃, and when the temperature is lower than 1250 ℃, the tricalcium silicate can be decomposed into dicalcium silicate (2 CaO. SiO) by slow cooling₂Also the main gelling mineral in ordinary portland cement) and calcium oxide, while dicalcium silicate belongs to metastable mineral, there are five crystal transformation in the cooling process, when the temperature is reduced from 1250 ℃, the crystal transformation starts (principle explanation), the transformation process is shown in fig. 1. :

wherein gamma type is inactive, so when the temperature is about 700 ℃, the dicalcium silicate crystal form is in the transition period of alpha and beta, the invention takes out the modified carbon steel slag C and takes a quenching measure, the crystal lattice of the modified carbon steel slag C is not in time to rearrange into gamma, and the beta type is reserved, according to the research, the invention shows that:

1) β -C2S is a metastable high-temperature mineral existing at normal temperature, and therefore its structure is thermodynamically unstable;

2) calcium ions in the beta-C2S have irregular coordination, so that the calcium ions have higher activity;

3) the presence of impurities and stabilizers in the beta-C2S structure also increases its structural activity.

The invention has the beneficial effects that:

(1) in the process of modifying the carbon steel slag, CaO contained in the stainless steel slag is required to be additionally doped for modification, the carbon steel slag is industrial solid waste and has the defects of large production amount and low utilization rate, and the method can effectively reduce or solve the problem of environmental pollution caused by accumulation of the industrial solid waste and change waste into valuable.

(2) In the preparation process of the sulphoaluminate modified carbon steel slag, the sulphoaluminate modified carbon steel slag is treated by a quenching method after being calcined, various mineral crystal form components cannot be rearranged in the quenching process, and the dicalcium silicate crystal form is kept as a beta type, so that the maximum activity of minerals can be excited.

(3) The carbon steel slag is modified and then mixed with cement mortar, so that the activity index of a mortar test block is greatly improved, the highest activity indexes of 3d and 28d are close to 100%, and the test block has good stability through tests and can be used as a mixed material to be doped into cement.

Drawings

Fig. 1 is a schematic diagram of the transformation principle of tricalcium silicate crystal form.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to specific embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The embodiment provides a thermal state calcium-added modified stainless steel slag, which is prepared by heating 85.4 wt% of stainless steel slag and 14.6 wt% of calcium oxide in a high-temperature furnace to react, wherein the preparation method comprises the following steps:

(1) preparing a mixture: mixing stainless steel slag and calcium oxide to form a mixture A;

(2) and (3) pressing and forming: pressing the mixture a into a material cake b with the diameter of 30mm and the thickness of 8mm by using a die with the inner diameter of 30mm and pressurizing for 10 seconds under the pressure of 50 kN;

(3) and (3) calcining: placing the pressed material cake b into a high-temperature furnace, and calcining for 150min at 1225-1275 ℃ to form a material cake c; the cake c has a micro-melting phenomenon in the temperature range, which proves that the stainless steel slag powder a and the analytically pure calcium oxide have a solid-phase reaction, if the temperature is lower than the temperature range, the stainless steel slag powder a and the analytically pure calcium oxide can have incomplete reaction to generate more other unrelated minerals, and if the temperature is higher than the temperature range, the stainless steel slag powder a and the analytically pure calcium oxide can have a melting phenomenon and are adhered to a crucible;

(4) quenching: cooling the material cake C generated in the step (3) in a high-temperature furnace, taking out the material cake C when the temperature is reduced to 700 ℃, and rapidly cooling to room temperature, wherein the rapidly cooling is specifically that after the material cake C is taken out, a high-power electric fan is adopted to blow the material cake C at room temperature, and the cooling rate is kept at 136 ℃/min;

(5) milling: the cake c was ground using a disk mill and a ball mill to a specific surface area of 350m²Per kg, obtaining modified stainless steel slag powder; after grinding, putting the modified stainless steel slag powder into a drying box, and drying at 105 ℃ to constant weight; then adding 5 percent of dihydrate gypsum, and uniformly mixing to obtain the thermal state calcium-added modified stainless steel slag.

The stainless steel slag comprises the following main chemical components in percentage by mass: CaO 45.72%, SiO₂31.65%、MnO₂ 5.72%、MgO 5.64%、Cr₂O₃ 1.54%、Al₂O₃ 1.37%、Fe₂O₃ 0.60%。

Wherein the stainless steel slag is ground into the specific surface area of 350kg/m by a disc grinder and a ball mill before being mixed³The stainless steel slag powder is put into a drying box and dried to constant weight at 105 ℃.

Wherein, the CaO content in the calcium oxide is 98 percent by mass, and the grain diameter is less than 1 mm.

Example 2

The embodiment provides a thermal state calcium-added modified stainless steel slag, which is prepared by heating 80 wt% of stainless steel slag and 20 wt% of calcium oxide in a high-temperature furnace to react, and the preparation method comprises the following steps:

(1) preparing a mixture: mixing stainless steel slag and calcium oxide to form a mixture A;

(2) and (3) pressing and forming: pressing the mixture a into a material cake b with the diameter of 30mm and the thickness of 8mm by using a die with the inner diameter of 30mm and pressurizing for 10 seconds under the pressure of 50 kN;

(3) and (3) calcining: placing the pressed material cake b into a high-temperature furnace, and calcining for 100min at 1225-1275 ℃ to form a material cake c; the cake c has a micro-melting phenomenon in the temperature range, which proves that the stainless steel slag powder a and the analytically pure calcium oxide have a solid-phase reaction, if the temperature is lower than the temperature range, the stainless steel slag powder a and the analytically pure calcium oxide can have incomplete reaction to generate more other unrelated minerals, and if the temperature is higher than the temperature range, the stainless steel slag powder a and the analytically pure calcium oxide can have a melting phenomenon and are adhered to a crucible;

(4) quenching: cooling the material cake C generated in the step (3) in a high-temperature furnace, taking out the material cake C when the temperature is reduced to 700 ℃, and rapidly cooling to room temperature, wherein the rapidly cooling is specifically that after the material cake C is taken out, a high-power electric fan is adopted to blow the material cake C at room temperature, and the cooling rate is kept at 120 ℃/min;

(5) milling: the cake c was ground using a disk mill and a ball mill to a specific surface area of 320m²Per kg, obtaining modified stainless steel slag powder; after grinding, putting the modified stainless steel slag powder into a drying box, and drying at 105 ℃ to constant weight; then adding 5 percent of dihydrate gypsum, and uniformly mixing to obtain the thermal state calcium-added modified stainless steel slag.

The stainless steel slag comprises the following main chemical components in percentage by mass: 43.72% of CaO and SiO₂29.65%、MnO₂ 4.72%、MgO 5.82%、Cr₂O₃ 1.03%、Al₂O₃ 1.76%、Fe₂O₃ 0.15%。

Wherein, the stainless steel slag is ground into the specific surface area of 350kg/m by a disc grinder and a ball mill before being mixed³The stainless steel slag powder is put into a drying box and dried to constant weight at 105 ℃.

Wherein, the CaO content in the calcium oxide is 97 percent by mass, and the grain diameter is less than 1 mm.

Example 3

The embodiment provides a thermal state calcium-added modified stainless steel slag, which is prepared by heating 95 wt% of stainless steel slag and 5 wt% of calcium oxide in a high-temperature furnace to react, and the preparation method comprises the following steps:

(1) preparing a mixture: mixing stainless steel slag and calcium oxide to form a mixture A;

(2) and (3) pressing and forming: pressing the mixture a into a material cake b with the diameter of 30mm and the thickness of 8mm by using a die with the inner diameter of 30mm and pressurizing for 10 seconds under the pressure of 50 kN;

(3) and (3) calcining: putting the pressed material cake b into a high-temperature furnace, and calcining for 200min at 1225-1275 ℃ to form a material cake c; the cake c has a micro-melting phenomenon in the temperature range, which proves that the stainless steel slag powder a and the analytically pure calcium oxide have a solid-phase reaction, if the temperature is lower than the temperature range, the stainless steel slag powder a and the analytically pure calcium oxide can have incomplete reaction to generate more other unrelated minerals, and if the temperature is higher than the temperature range, the stainless steel slag powder a and the analytically pure calcium oxide can have a melting phenomenon and are adhered to a crucible;

(4) quenching: cooling the material cake C generated in the step (3) in a high-temperature furnace, taking out the material cake C when the temperature is reduced to 700 ℃, and rapidly cooling to room temperature, wherein the rapidly cooling is specifically that after the material cake C is taken out, a high-power electric fan is adopted to blow the material cake C at room temperature, and the cooling rate is kept at 140 ℃/min;

(5) milling: the cake c was ground using a disk mill and a ball mill to a specific surface area of 380m²Per kg, obtaining modified stainless steel slag powder; after grinding, putting the modified stainless steel slag powder into a drying box, and drying at 105 ℃ to constant weight; then adding 5 percent of dihydrate gypsum, and uniformly mixing to obtain the thermal state calcium-added modified stainless steel slag.

The stainless steel slag comprises the following main chemical components in percentage by mass: 47.72% of CaO and SiO₂29.65%、MnO₂ 6.84%、MgO 4.72%、Cr₂O₃ 1.96%、Al₂O₃ 1.03%、Fe₂O₃ 0.98%。

Wherein, the stainless steel slag is ground into the specific surface area of 350kg/m by a disc grinder and a ball mill before being mixed³The stainless steel slag powder is put intoAnd drying in a drying box at 105 ℃ to constant weight.

Wherein, the CaO content in the calcium oxide is 99 percent by mass, and the grain diameter is less than 1 mm.

Example 4

The embodiment provides a thermal state calcium-added modified stainless steel slag, which is prepared by heating 86 weight percent of stainless steel slag and 14 weight percent of calcium oxide in a high-temperature furnace to react, and the preparation method comprises the following steps:

(1) preparing a mixture: mixing stainless steel slag and calcium oxide to form a mixture A;

(2) and (3) pressing and forming: pressing the mixture a into a material cake b with the diameter of 30mm and the thickness of 8mm by using a die with the inner diameter of 30mm and pressurizing for 10 seconds under the pressure of 50 kN;

(3) and (3) calcining: putting the pressed material cake b into a high-temperature furnace, and calcining for 180min at 1225-1275 ℃ to form a material cake c; the cake c has a micro-melting phenomenon in the temperature range, which proves that the stainless steel slag powder a and the analytically pure calcium oxide have a solid-phase reaction, if the temperature is lower than the temperature range, the stainless steel slag powder a and the analytically pure calcium oxide can have incomplete reaction to generate more other unrelated minerals, and if the temperature is higher than the temperature range, the stainless steel slag powder a and the analytically pure calcium oxide can have a melting phenomenon and are adhered to a crucible;

(4) quenching: cooling the material cake C generated in the step (3) in a high-temperature furnace, taking out the material cake C when the temperature is reduced to 700 ℃, and rapidly cooling to room temperature, wherein the rapidly cooling is specifically that after the material cake C is taken out, a high-power electric fan is adopted to blow the material cake C at room temperature, and the cooling rate is kept at 130 ℃/min;

(5) milling: the cake c was ground using a disk mill and a ball mill to a specific surface area of 360m²Per kg, obtaining modified stainless steel slag powder; after grinding, putting the modified stainless steel slag powder into a drying box, and drying at 105 ℃ to constant weight; then adding 5 percent of dihydrate gypsum, and uniformly mixing to obtain the thermal state calcium-added modified stainless steel slag.

The stainless steel slag comprises the following main chemical components in percentage by mass: CaO 45.36%, SiO₂32.15%、MnO₂ 5.68%、MgO 5.62%、Cr₂O₃ 1.56%、Al₂O₃ 1.39%、Fe₂O₃ 0.62%。

Wherein, the stainless steel slag is ground into the specific surface area of 350kg/m by a disc grinder and a ball mill before being mixed³The stainless steel slag powder is put into a drying box and dried to constant weight at 105 ℃.

Wherein, the CaO content in the calcium oxide is 98 percent by mass, and the grain diameter is less than 1 mm.

Application example

Mixing the modified stainless steel slag powder and Portland cement in a ratio of 3: 7, preparing the mixture into a standard sample with the size of 40mm multiplied by 160mm according to GB/T17671-1999 Cement mortar Strength test method (ISO method), and testing the flexural strength and compressive strength after curing to a specified age, wherein the test results of the mortar are shown in Table 1.

TABLE 1 mortar test results

Note: group 0 is the portland cement mortar test result; the S0 group is formed by grinding carbon steel slag and portland cement in a ratio of 3: 7, testing results of the mortar after mixing according to the proportion; S1-S4 are the sulphoaluminate modified carbon steel slag and the portland cement of examples 1-4, respectively, in the ratio of 7: 3, and (3) testing the mixed mortar.

The result shows that after the modifier is added, the activity index of the mortar test block is greatly improved, the activity indexes of 3d and 28d are both close to 100% at most, and the flowability is good. And tests show that the test block has good stability and can be used as a mixed material to be doped into cement.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.