Low-carbon-emission high-magnesium Portland cement clinker and preparation method thereof

Abstract

The invention discloses a low-carbon-emission high-magnesium Portland cement clinker and a preparation method thereof. The clinker rate value is controlled as follows: KH is equal to 0.87-0.93, SM is equal to 2.4-2.8, and IM is equal to 1.3-1.8; the content of magnesium oxide in the clinker is 3-6%, and the content of zinc oxide in the clinker is 0.01-0.025%. The high-magnesium low-grade limestone is adopted as the ingredient, the clinker liquid phase amount is increased by increasing the magnesium oxide content, and meanwhile, the galvanized sludge is added to promote clinker sintering and improve the strength performance of the clinker; the firing temperature is reduced by increasing the liquid phase, the fuel carbon emission is reduced, the limestone consumption can be reduced by increasing the clinker strength, and the raw material carbon emission is reduced; under the same clinker strength condition, the unit clinker carbon emission is reduced by more than 10%.

Description

Technical Field

[0001] The invention belongs to the technical field of utilizing low-carbon emission silicate cement clinker, and in particular relates to a low-carbon emission high-magnesium silicate cement clinker and a preparation method thereof. Background Art

[0002] The cement industry is the largest carbon emitter after the power and steel industries. The carbon emissions of the cement industry mainly come from the decomposition of raw limestone and the carbon dioxide produced by fuel combustion. The firing temperature of cement clinker reaches 1450℃. By lowering the firing temperature, the amount of fuel can be reduced and carbon emissions can be reduced. On the other hand, cement clinker minerals play a role in strength and increase the activity of clinker minerals, which can reduce the amount of carbonate in the raw materials and reduce clinker carbon emissions.

[0003] The increase in magnesium oxide content in clinker can increase the liquid phase of clinker. High-magnesium low-grade limestone is an interlayer rock with a high magnesium content. It is often discarded as waste or sold as aggregate in the cement production process, which not only affects environmental safety, but also causes waste of mining resources. With the large-scale consumption of high-quality limestone resources by cement manufacturers, in order to reduce production costs and maintain production operations, more and more companies are forced to use high-magnesium low-grade limestone to produce cement clinker, resulting in an increase in the magnesium oxide content in the clinker, which brings about an increase in the amount of liquid phase. Although the increase in the amount of liquid phase brings certain operational difficulties to the clinker burning, it also provides conditions for promoting the absorption of calcium oxide during the clinker calcination process.

[0004] With the rapid development of the electroplating industry, the electrogalvanizing process produces a large amount of electroplating wastewater. Electrogalvanizing sludge is produced by adding solid sediment to the electrogalvanizing wastewater. Due to the high zinc content in electrogalvanizing sludge, it is difficult to treat it harmlessly and the recycling cost is high. As an industrial solid waste, the large amount of galvanizing sludge is difficult to handle and urgently needs a large-scale disposal method. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a low-carbon emission high-magnesium silicate cement clinker and a preparation method thereof, which solves the problem of resource waste and environmental pollution caused by the stacking of high-magnesium low-grade limestone and galvanized sludge, and makes full use of the magnesium oxide in the high-magnesium low-grade limestone to increase the clinker liquid phase, and the zinc element in the galvanized sludge to promote the clinker burning, etc., significantly reducing the clinker burning temperature and fuel consumption, improving the performance of the clinker, and reducing the carbon emission of the clinker.

[0006] The present invention is achieved in that:

[0007] A low-carbon emission high-magnesium silicate cement clinker, wherein the clinker rate values ​​are controlled as follows: KH=0.87-0.93, SM=2.4-2.8, IM=1.3-1.8; the magnesium oxide content in the clinker is 3.0-6.0%, and the zinc oxide content in the clinker is 0.01-0.025%.

[0008] Preferably, the raw materials of low-carbon emission high-magnesium silicate cement clinker include: calcium raw materials, silicon raw materials, aluminum raw materials, iron raw materials and activators.

[0009] Further preferably, the calcium raw material is high-magnesium low-grade limestone, the siliceous raw material is sandstone, the aluminum raw material is clay, the iron raw material is iron tailings, and the activator is galvanized sludge.

[0010] More preferably, the zinc oxide content in the galvanizing sludge is 0.1-1.0%, and the galvanizing sludge addition amount is 2-10%.

[0011] More preferably, the magnesium oxide content in the high-magnesium low-grade limestone is 3.5-6.0%.

[0012] Preferably, the sintering temperature of the low-carbon emission high-magnesium Portland cement clinker is 1350-1400°C, which is 50-100°C lower than that of ordinary Portland cement clinker.

[0013] Preferably, the low-carbon emission high-magnesium Portland cement clinker has a carbon emission per unit clinker reduced by more than 10% compared with ordinary Portland cement clinker under the same 28-day compressive strength conditions.

[0014] The method for preparing the above-mentioned low-carbon emission high-magnesium silicate cement clinker comprises the following steps:

[0015] S1, crushing and homogenizing calcium raw materials, silicon raw materials, aluminum raw materials and iron raw materials and sending them to the blending warehouse;

[0016] S2, the raw materials prepared in step S1 are measured according to the set ratio, and the measured raw materials are sent to the raw material mill, and the raw material fineness is controlled at 80 micron sieve residue of 10-18%;

[0017] S3, the raw meal discharged from the mill is sent to the raw meal storage for homogenization;

[0018] S4, the homogenized raw material is preheated and then calcined, and the galvanized sludge is sprayed into the decomposition furnace in proportion, the outlet temperature of the decomposition furnace is controlled not to be higher than 880°C, and the apparent decomposition rate is controlled to be greater than 85%, and the hot raw material after decomposition is fed into the kiln for calcination, and the firing temperature is controlled to be 1350-1400°C;

[0019] S5. The clinker discharged from the kiln enters the grate cooler for rapid cooling to obtain low-carbon emission high-magnesium silicate cement clinker.

[0020] The main idea of ​​the present invention is to introduce magnesium oxide into the clinker through high-magnesium low-grade limestone, thereby increasing the amount of clinker calcination liquid phase. Under this condition, sufficient liquid phase provides a convenient way for the migration of zinc elements in galvanized sludge in the high-temperature liquid phase, promotes the accelerated formation of silicate minerals, and at the same time improves the activity of clinker minerals. The strength performance of clinker is improved, and the use of calcium raw materials such as calcium carbonate can be reduced under the same clinker strength conditions, reducing raw material carbon emissions. The clinker calcination temperature is reduced from 1450°C to 1350-1400°C, which significantly reduces the coal consumption for burning and reduces the fuel carbon emissions during the clinker calcination process.

[0021] According to the principle of cement technology, when the magnesium oxide content in the clinker is greater than 2%, the clinker becomes high-magnesium silicate clinker. The calculation formula of the liquid phase amount of high-magnesium silicate clinker is shown in formula (1):

[0022] Liquid phase volume (%) = 3.0A + 2.25F + M + R (1)

[0023] In the formula: A is the aluminum oxide (Al2O3) content in the clinker, F is the iron oxide (Fe2O3) content in the clinker, M is the magnesium oxide (MgO) content in the clinker, and R is the alkali content in the clinker.

[0024] It can be seen from Formula 1 that when other conditions remain unchanged, the amount of clinker liquid phase increases with the increase of magnesium oxide content in clinker. When high-magnesium low-grade limestone is used to replace ordinary limestone for calcining clinker, the magnesium oxide content in clinker increases and the amount of liquid phase increases. The inventors have found through a large number of experiments that although magnesium oxide in clinker can increase the amount of clinker liquid phase, magnesium oxide has no mineralization effect. When the amount of clinker liquid phase reaches 28-30%, there is still about 5% of free calcium oxide in the clinker that is not absorbed, while the normal production of ordinary Portland cement clinker requires a free calcium oxide content of about 1%. Therefore, it is necessary to take measures to promote the absorption rate of calcium oxide by cement clinker minerals under higher liquid phase conditions.

[0025] After a large number of experimental studies, the inventors found that since galvanized sludge contains a large amount of zinc, under the condition of sufficient liquid phase amount during the clinker burning process, zinc can reduce the clinker formation temperature and accelerate the clinker transition minerals to absorb calcium oxide to form clinker minerals and increase the activity of clinker minerals, thereby improving the performance of the clinker.

[0026] By using high-magnesium low-grade limestone and galvanized sludge as raw materials to calcine cement clinker, magnesium oxide can increase the amount of liquid phase in clinker calcination, and zinc element accelerates the reaction of clinker minerals under liquid phase conditions, so that cement clinker can be fired at a lower calcination temperature of 1350-1400℃, significantly reducing fuel consumption and improving clinker strength. This will make it possible to produce low-carbon emission high-magnesium silicate cement clinker.

[0027] The zinc element in the galvanized sludge can produce a complex effect with the magnesium oxide in the clinker. Magnesium oxide increases the amount of liquid phase at a lower calcination temperature, and the zinc element can quickly migrate in the liquid phase, promoting the absorption of calcium oxide by the clinker minerals. Compared with the case without the addition of galvanized sludge, the free calcium oxide in the clinker was significantly reduced to less than 1% after the addition of galvanized sludge to the raw materials, indicating that the clinker was fired under low temperature conditions. By testing the strength of the clinker, it was found that the strength performance of the clinker increased by 3-5MPa after the addition of galvanized sludge, which shows that the zinc element has an activation effect on the clinker minerals. For every 100°C reduction in the firing temperature, the coal consumption per kilogram of clinker is reduced by 10 kilograms, and the carbon emissions of the clinker are reduced by more than 5% accordingly; the strength performance of the clinker is improved by 3-5MPa, which brings about a reduction of more than 5% in carbon emissions per unit of clinker, and the combined carbon reduction effect of the two reaches more than 10%.

[0028] The advantages and positive effects of the present invention are:

[0029] (1) The present invention proposes for the first time to use magnesium oxide introduced from high-magnesium low-grade limestone to increase the amount of liquid phase in the clinker burning process, and to couple the zinc element in the galvanized sludge to promote the formation of clinker minerals and improve their activity, thereby reducing carbon emissions per unit of clinker by more than 10%.

[0030] (2) The implementation of the present invention can utilize high-magnesium low-grade limestone and galvanized sludge on a large scale, significantly improving the comprehensive resource utilization rate of solid waste.

[0031] (3) The present invention opens up a new way for cement production enterprises to reduce production costs by using solid waste to produce high-magnesium silicate cement clinker, which is particularly beneficial for the cement industry to further reduce costs and increase efficiency through carbon trading. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] Examples 1 to 3

[0034] The embodiment of the present invention provides a method for preparing low-carbon emission high-magnesium silicate cement clinker, comprising the following steps:

[0035] S1, crushing and homogenizing calcium raw materials, silicon raw materials, aluminum raw materials and iron raw materials and sending them to the blending warehouse;

[0036] S2, the raw materials prepared in step S1 are measured according to the set ratio, and the measured raw materials are sent to the raw material mill, and the raw material fineness is controlled at 80 micron sieve residue of 10-18%;

[0037] S3, the raw meal discharged from the mill is sent to the raw meal storage for homogenization;

[0038] S4, the homogenized raw material is preheated and then calcined, and the galvanized sludge is sprayed into the decomposition furnace in proportion, the outlet temperature of the decomposition furnace is controlled not to be higher than 880°C, and the apparent decomposition rate is controlled to be greater than 85%, and the hot raw material after decomposition is fed into the kiln for calcination, and the firing temperature is controlled to be 1350-1400°C;

[0039] S5. The clinker discharged from the kiln enters the grate cooler for rapid cooling to obtain low-carbon emission high-magnesium silicate cement clinker.

[0040] The raw materials of low-carbon emission high-magnesium silicate cement clinker include: calcium raw materials, silicon raw materials, aluminum raw materials, iron raw materials and activators. The calcium raw materials are high-magnesium low-grade limestone, the silicon raw materials are sandstone, the aluminum raw materials are clay, the iron raw materials are iron tailings, and the activator is galvanized sludge.

[0041] In Examples 1 to 3, low-carbon emission high-magnesium silicate cement clinker is obtained by adjusting the amounts of calcium raw materials, silicon raw materials, aluminum raw materials, iron raw materials, and activators to control different clinker rate values.

[0042] Comparative Examples 1 to 3

[0043] Comparative Example 1 is ordinary Portland cement clinker burnt with ordinary limestone as the calcium raw material, and no galvanized sludge is added to the raw materials. The amounts of other raw materials are the same as those of Example 2.

[0044] Comparative Example 2 is ordinary Portland cement clinker burnt with ordinary limestone as the calcium raw material, galvanized sludge is added to the raw material, and the amounts of other raw materials are the same as those of Example 2.

[0045] Comparative Example 3 is a high-magnesium silicate cement clinker fired with high-magnesium low-grade limestone as a calcium raw material. No galvanized sludge is added to the raw materials. The amounts of other raw materials are the same as those in Example 2, and the rate value control is the same as that in Example 2.

[0046] The raw material fineness, firing temperature, clinker rate value, magnesium oxide and free calcium oxide content in the clinker and the 28-day compressive strength of the clinker of Examples 1-3 of the present invention and Comparative Examples 1-3 are specifically shown in Table 1.

[0047] Table 1 Data of Examples 1-3 and Comparative Examples 1-3

[0048]

[0049] Note: The carbon emission reduction of Examples 1-3 is the percentage reduction relative to Comparative Example 1.

[0050] The data in Table 1 show that, compared with Comparative Examples 1-3, the firing temperature of Examples 1-3 is reduced from 1450°C to 1350-1400°C, the free calcium oxide content in the clinker is basically controlled at about 1%, and the magnesium oxide content in the clinker is higher than 3%, which indicates that the firing temperature of high-magnesium clinker is significantly reduced, fuel consumption is reduced, and fuel carbon emissions are reduced.

[0051] Compared with Comparative Examples 1-3, under the combined effect of magnesium oxide and zinc introduced from galvanized sludge, the 28-day compressive strength of the clinker in Examples 1-3 is increased by 3-5 MPa. Under the same clinker strength conditions, the amount of calcium raw material added can be reduced and the carbon emission of the raw materials is reduced.

[0052] Compared with comparative examples 1-3, the carbon emissions per unit clinker of embodiments 1-3 were reduced by more than 10%, demonstrating a good carbon reduction effect.

[0053] Although zinc was introduced into Comparative Example 2 by adding galvanized sludge, the activation effect of zinc on clinker minerals was not reflected due to the low magnesium oxide content in the clinker and the relatively small amount of liquid phase.

[0054] Although Comparative Example 3 increases the magnesium oxide content in the clinker, there is no zinc element as an activator, and the clinker sintering temperature and strength performance are not significantly improved. Compared with Example 2, the sintering temperature is higher, the strength is lower, and the carbon emission is higher.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents, and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-carbon emission high-magnesium silicate cement clinker, characterized in that: The clinker rate values ​​are controlled as follows: KH=0.87-0.93, SM-2.4-2.8, IM=1.3-1.8; the magnesium oxide content in the clinker is 3.0-6.0%, and the zinc oxide content in the clinker is 0.01-0.025%.

2. The low-carbon emission high-magnesium silicate cement clinker according to claim 1, characterized in that: The raw materials of the low-carbon emission high-magnesium silicate cement clinker include: calcium raw materials, silicon raw materials, aluminum raw materials, iron raw materials and activators.

3. The low carbon emission high magnesium silicate cement clinker according to claim 2, characterized in that: The calcium raw material is high-magnesium low-grade limestone; the silicon raw material is sandstone; the aluminum raw material is clay; the iron raw material is iron tailings, and the activator is galvanized sludge.

4. The low carbon emission high magnesium silicate cement clinker according to claim 3, characterized in that: The zinc oxide content in the galvanizing sludge is 0.1-1.0%, and the addition amount of the galvanizing sludge is 2-10%.

5. The low carbon emission high magnesium silicate cement clinker according to claim 3, characterized in that: The magnesium oxide content in the high-magnesium low-grade limestone is 3.5-6.0%.

6. The low carbon emission high magnesium silicate cement clinker according to claim 1, characterized in that: The sintering temperature of the low-carbon emission high-magnesium silicate cement clinker is 1350-1400° C., which is 50-100° C. lower than that of ordinary silicate cement clinker.

7. The low carbon emission high magnesium silicate cement clinker according to claim 1, characterized in that: Under the same 28-day compressive strength condition, the low-carbon emission high-magnesium silicate cement clinker has a unit clinker carbon emission reduced by more than 10% compared with ordinary silicate cement clinker.

8. A method for preparing low-carbon emission high-magnesium silicate cement clinker based on any one of claims 1 to 7, characterized in that: The following steps are involved: S1, crushing and homogenizing calcium raw materials, silicon raw materials, aluminum raw materials and iron raw materials and sending them to the blending warehouse; S2, weighing the raw materials prepared in step S1 according to the set ratio, sending the weighed raw materials to the raw material mill, and controlling the raw material fineness to be 10-18% of the 80 micron sieve residue; S3, the raw meal discharged from the mill is sent to the raw meal storage for homogenization; S4, the homogenized raw material is preheated and then calcined, and the galvanized sludge is sprayed into the decomposition furnace in proportion, the outlet temperature of the decomposition furnace is controlled not to be higher than 880°C, and the apparent decomposition rate is controlled to be greater than 85%, and the hot raw material after decomposition is fed into the kiln for calcination, and the firing temperature is controlled to be 1350-1400°C; S5. The clinker discharged from the kiln enters the grate cooler for rapid cooling to obtain low-carbon emission high-magnesium silicate cement clinker.

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