CN114477948A

CN114477948A - Method for preparing high-temperature-resistant steel slag brick by accelerated carbonization

Info

Publication number: CN114477948A
Application number: CN202210062823.1A
Authority: CN
Inventors: 林忠财; 仲心卓; 罗双
Original assignee: Hunan University
Current assignee: Hunan University
Priority date: 2022-01-19
Filing date: 2022-01-19
Publication date: 2022-05-13
Anticipated expiration: 2042-01-19
Also published as: CN114477948B

Abstract

The invention discloses a method for preparing a high-temperature-resistant steel slag brick by utilizing accelerated carbonization, wherein the high-temperature-resistant steel slag brick is prepared by mixing 100 percent of steel slag powder and water; during preparation, the ground converter steel slag industrial waste is used as a raw material, low water-solid ratio and high forming pressure are adopted for pressing and forming to obtain a blank brick, the blank brick is placed in a high-temperature reaction kettle, and carbon dioxide gas or industrial flue gas is introduced for accelerated carbonization and maintenance to obtain the high-temperature resistant steel slag brick. The invention prepares the steel slag brick by utilizing industrial waste generated by steel making, and utilizes carbon dioxide to accelerate curing to achieve the effect of high temperature resistance, has short curing time and high strength, can bear the high temperature of up to 600 ℃, does not need cement clinker, has low cost and conforms to the environmental protection concept of green buildings.

Description

Method for preparing high-temperature-resistant steel slag brick by accelerated carbonization

Technical Field

The invention relates to the field of solid waste utilization and the technical field of accelerated carbonization, in particular to a method for preparing a high-temperature-resistant cement-free steel slag brick by utilizing accelerated carbonization.

Background

The steel slag is difficult to utilize as resources due to the problems of low hydration activity, poor volume stability and the like, however, researches show that the two problems can be effectively solved by accelerating carbonization. Accelerated carbonization of steel slag can produce large amounts of calcium carbonate to achieve sufficient strength and durability. In order to facilitate the carbonization process and to avoid the risk of volume stability, it is often used in the form of a steel slag brick.

The brick structure has the defect of poor high temperature resistance, for example, the compressive strength of the M10 mortar clay brick is reduced by 35 percent when the temperature reaches 300 ℃, which greatly limits the use of the brick structure in high temperature resistant engineering. In addition, the use requirements of places needing high-temperature operation, such as the interior of an industrial chimney, a high-temperature workshop and the like, on the brick structure are increasingly improved, the requirement on the high-temperature resistance of the brick structure is also increasingly high, and the conventional brick structure is difficult to meet the industrial requirements. The strength of the carbonized steel slag product is mainly provided by calcium carbonate generated after carbonization, and the calcium carbonate has high thermal stability, so the carbonized steel slag has excellent high-temperature resistance. According to the existing problems of the steel slag and the accelerated carbonization principle, the invention adopts a method for preparing the high-temperature-resistant steel slag brick by using a carbonization curing mode, and solves the problems of low resource utilization rate of the steel slag and insufficient high-temperature resistance of the brick structure.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a method for preparing a high-temperature-resistant steel slag brick by utilizing accelerated carbonization. The innovativeness of the method is that the carbonization curing environment is high temperature and high pressure, the curing efficiency is high, and the steel slag block prepared by curing has higher strength and better high temperature resistance.

In order to achieve the purpose, the invention adopts the following technical scheme:

1. selecting ground converter steel slag as the only raw material for manufacturing the steel slag brick, wherein the grain size of the steel slag is less than 75 mu m, and the specific surface area of the steel slag is 2.7-2.9 m²(ii) per gram, density of 3.3-3.5 g/cm3, CaO content of more than 40%, SiO₂The content is more than 15 percent

2. Adding water: the steel slag powder and water are weighed according to the standard that the mass ratio (water-solid ratio) of the steel slag powder is 0.12-0.18, and the water for blending is divided into two parts on average and added in two times. The stirring time is more than or equal to 30s each time, and the stirring process should be kept at a constant speed to prevent the steel slag powder from caking;

3. weighing a proper amount of the mixture obtained in the step 1, keeping the mixture under the pressure of 5-15MPa for 20 +/-0.5 s, and then unloading to obtain the blank brick. Wherein the pressurization process should maintain the pressurization rate substantially equal. The apparent density of the steel slag brick is about 1.8-2.2g/cm³Initial porosity of about 20-30%;

4. and (3) putting the test block formed in the step (2) into a temperature-controlled pressure carbonization reaction kettle, wherein the preparation environment and the reaction kettle are sealed. CO in the kettle₂The gas can also be industrial flue gas or industrially prepared CO₂Gas, concentration should be kept at 20 + -1% or more, CO₂The pressure is kept at 0.1-0.5MPa, the temperature in the kettle is kept at 50 +/-0.5 ℃ to 70 +/-0.5 ℃, and the carbonization is accelerated for 1-2 hours under the environment of constant temperature and constant pressure;

the invention has the beneficial effects that:

1. the preparation method is simple, the curing time is short, the carbonization efficiency is high, and CO is₂The absorption rate reaches 12 percent. The compressive strength of the steel slag carbonized product obtained after the carbonization curing is accelerated for 2 hours can reach 60 MPa.

2. The product of the invention has excellent high temperature resistance, the strength is not reduced but improved at the high temperature of 200-600 ℃, compared with the conventional brick structure, the product can bear higher temperature and maintain good mechanical property, can be used in high-temperature workshops and other environments, and furthest develops the utilization value of the steel slag.

3. The preparation method provided by the invention recycles the industrial solid waste steel slag, does not need to add cement, and can reduce CO in the cement production process₂And (5) discharging. Meanwhile, the accelerated carbonization can convert greenhouse gas CO₂The carbonate is permanently and fixedly stored in the steel slag block, which is beneficial to the sustainable development of the civil engineering industry.

Drawings

FIG. 1 is a scanning electron microscope image of 2h steel slag brick accelerated in carbonization and maintenance

FIG. 2 is a scanning electron microscope image of the slag brick placed at a high temperature of 600 ℃ after accelerated carbonization and curing for 2 hours

Detailed Description

The present invention will be described in detail with reference to specific examples.

Example 1

The method for preparing the high-temperature-resistant steel slag brick by utilizing accelerated carbonization specifically comprises the following steps:

step one, using fine converter steel slag powder as a raw material for preparing bricks, wherein the average particle size of the steel slag powder particles is 6 microns;

step two, mixing the steel slag powder with water according to a water-solid ratio of 0.12, wherein the mixing water is divided into two parts on average and added in two times, and the mixing time is 30s each time, so as to form a mixture of the steel slag powder and the water;

step three, weighing a proper amount of the mixture obtained in the step two, pouring the mixture into a mold, placing the mold under a forming press, pressurizing to 15MPa at a constant speed, and unloading after keeping constant pressure for 20 s;

and step four, immediately putting the pressed and formed test block into a temperature-controlled pressure carbonization reaction kettle. The reaction kettle is heated to 70 ℃ in advance and kept at a constant temperature, after the test block is put in, the air inlet and the air outlet are opened, and CO with the concentration of 99 +/-1 percent is slowly introduced₂And (4) exhausting air in the reaction kettle, and closing the air outlet after two minutes. Adjusting the pressure gauge to make CO in the reaction kettle₂The pressure was maintained at 0.5 MPa. And (3) accelerating carbonization for 2 hours under the environment of constant temperature and constant pressure, and finishing the preparation of the high-temperature resistant steel slag brick.

Tests show that the compressive strength of the steel slag brick after accelerated carbonization for 2 hours is 60.1MPa, and CO₂The absorption rate is 12 percent, and the high temperature of 600 ℃ can be endured.

Example 2

step one, using fine converter steel slag powder as a raw material for preparing bricks, wherein the average grain size of the steel slag powder particles is 17 microns;

step two, mixing the steel slag powder with water according to a water-solid ratio of 0.12, adding water for two times and stirring for 30s each time to form a mixture of the steel slag powder and the water;

step three, weighing a proper amount of the mixture obtained in the step two, pouring the mixture into a mold, placing the mold under a forming press, pressurizing to 12MPa at a constant speed, and unloading after keeping constant pressure for 20 s;

and step four, immediately putting the pressed and formed test block into a temperature-controlled pressure carbonization reaction kettle. The reaction kettle is heated to 50 ℃ in advance and kept at a constant temperature, after the test block is put in, the air inlet and the air outlet are opened, and 99 +/-1% of CO is slowly introduced₂And (3) exhausting air in the reaction kettle, and closing the air outlet after 2 minutes. Adjusting the pressure gauge to make CO in the reaction kettle₂The pressure was maintained at 0.1 MPa. The preparation of the high temperature resistant steel slag brick can be finished by accelerating the carbonization for 2 hours under the environment of constant temperature and constant pressure (the temperature is 50 ℃ and the pressure is 0.1 MPa).

Tests show that the compressive strength of the steel slag brick after 2 hours of carbonization is 48.6MPa, and CO₂The absorption rate is 10.6%, and the high temperature of 600 ℃ can be endured.

The principle of the invention is as follows: the main carbonizable component in the steel slag is dicalcium silicate (C)₂S) is carbonized to form a gel structure with lower calcium-silicon ratio and longer chain length, and the gel structure has higher high-temperature stability. Meanwhile, in conventional cement-based blocks, the cement hydrates to form calcium silicate hydrate (C-S-H) gel, which is prone to unstable vaterite and aragonite formation during carbonization (decomposition before 720 ℃). The steel slag has almost no hydration activity and no C-S-H, and the invention utilizes the key point to manufacture the high-temperature resistant steel slag brick, and the high-temperature and high-pressure accelerated carbonization is carried out, so that calcite with the highest thermal stability is easy to generate (the decomposition temperature is 720-950 ℃). Therefore, the high-temperature resistant performance is excellent.

The secondary electron microscope pictures of the steel slag brick at 20 ℃ and 600 ℃ are respectively shown in figure 1 and figure 2. The comparison shows that the densely piled calcite observed at the temperature of 20 ℃ still exists at the temperature of 600 ℃, and the C-S-H of a net structure is not observed, so that the microstructure of the steel slag after accelerated carbonization cannot be damaged at high temperature, the stable calcite provides the strength of the steel slag brick at normal temperature and 600 ℃, and the excellent high-temperature resistance of the accelerated carbonization steel slag brick is proved.

While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A method for preparing a high-temperature-resistant steel slag brick by utilizing accelerated carbonization is characterized by comprising the following steps of:

fully mixing the steel slag powder and water to form a mixture of the steel slag powder and the water;

step two, obtaining a blank brick by using a pressure forming mode, and immediately putting the blank brick into a temperature-controlled pressure carbonization reaction kettle;

and step three, adjusting the carbonization pressure and temperature and keeping the temperature constant for 1-2 hours to obtain the high-temperature-resistant steel slag brick.

2. The method for preparing the high temperature resistant steel slag brick by using the accelerated carbonization as claimed in claim 1, is characterized in that: the average grain size of the fine converter steel slag powder is less than 75 mu m.

3. The method for preparing the high temperature resistant steel slag brick by using the accelerated carbonization as claimed in claim 1, is characterized in that: the water-solid ratio is 0.12-0.18, the blending water is divided into two parts on average, the two parts are added in two times, and the stirring time is more than or equal to 30s each time.

4. The method for preparing the high temperature resistant steel slag brick by using the accelerated carbonization as claimed in claim 1, is characterized in that: the forming pressure for preparing the brick is 5-15MPa, and the constant pressure is kept for 20 +/-0.5 s.

5. The method for preparing the high temperature resistant steel slag brick by using the accelerated carbonization as claimed in claim 1, is characterized in that: the temperature control pressure carbonization reaction kettle keeps sealed.

6. The method for preparing the high temperature resistant steel slag brick by using the accelerated carbonization as claimed in claim 1, is characterized in that: CO in the kettle₂The gas can be industrial flue gas or industrially prepared CO₂Gas, said CO₂The gas concentration should be kept at 20 + -1% and above, CO₂The pressure is kept at 0.1-0.5MPa, the temperature in the kettle is kept at 50 +/-0.5 ℃ to 70 +/-0.5 ℃, and the carbonization is accelerated for 1-2 hours under the environment of constant temperature and constant pressure.