CN115286269A - A method for improving the stability of clinker by using industrial flue gas - Google Patents

Abstract

A method for improving the stability of clinker by utilizing industrial flue gas. The invention relates to the technical field of construction material preparation. The following steps are included: Step 1, after the conventional cement raw meal is calcined at a high temperature by a conventional calcination process, and cooled to room temperature naturally or accelerated to obtain conventional clinker; Step 2, the clinker obtained in step 1 is crushed or ground to a particle size ≤1mm, store it in the clinker silo; Step 3, inject the flue gas containing CO ₂ into the clinker silo to ensure that the CO ₂ concentration in the clinker silo is at least 80% of the injected flue gas, so as to obtain clinker with excellent stability . In step 3, the flue gas injection time is 30 min to 360 min. In step 3, the concentration of CO ₂ in the flue gas containing CO ₂ is ≥20%. The present invention effectively reduces the content of main components (namely free calcium oxide and magnesium oxide) in the clinker that are unfavorable to the stability of the cement through the carbonization treatment of the prepared clinker by industrial flue gas, and accordingly generates carbonate with stable performance. It provides a new way to improve or enhance the stability of clinker.

Description

A method of improving the stability of clinker by using industrial flue gas

technical field

The invention relates to the technical field of building material preparation, in particular to a method for improving the stability of clinker by using industrial flue gas.

Background technique

The stability of cement, also known as cement volume stability, reflects the uniformity of the volume change of cement in the process of setting and hardening, and is one of the key indicators for cement production enterprises and engineering units; cement with unqualified stability is one of the causes of engineering accidents one.

The stability of cement is mainly due to the quality of the clinker. After the silicate clinker is calcined by the conventional calcination process, there are generally a small amount of free calcium oxide and magnesium oxide remaining. According to the relevant theory of cement hydration, the water content of free calcium oxide and magnesium oxide Melting will cause the cement specimen to expand and crack, causing stability problems. How to ensure the stability of clinker becomes the key to the quality control of cement stability. The currently known methods for improving the stability of clinker mainly focus on the control of the clinker firing process, and there is no effective method for improving the stability of clinker that has been produced. Li Weining proposed a way to improve the stability of the kiln clinker by humidifying the combustion-supporting air in the vertical kiln calcination in the article "Methods for Improving the Stability of Cement and Improving the Quality of Clinker", but this method is relatively difficult to control the amount of water sprayed. Strict, excessive water spray will reduce the clinker strength.

Cement and lime industries, as typical high-carbon emission industries, are the focus of attention during the implementation of the national "double carbon" policy. Taking the cement industry as an example, the annual output of cement in my country is about 2.3 billion tons. Based on clinker accounting for 80%, the national annual output of clinker is about 1.84 billion tons. The carbon emission per ton of clinker is 850-860kg, and the annual carbon dioxide emission is about 1.56 billion tons, accounting for about 15% of the country's total carbon emissions. In the process of addressing climate change, carbon emissions trading is considered the most operational policy tool from a long-term perspective. The national carbon market will be launched on July 16, 2021. Thermal power companies will take the lead in entering the national carbon trading market. Petrochemical, chemical, building materials, steel, non-ferrous metals, papermaking, and aviation will be included in seven other high-emission industries one after another. The allocation of carbon emission quotas Focusing on free distribution, timely introduction of paid distribution, and reducing the total carbon emissions of clinker through low-cost means have become the key development and research directions of the cement industry in the future.

Contents of the invention

Aiming at the above problems, the present invention provides a method for improving the stability of clinker by using industrial flue gas to effectively improve the stability of clinker while absorbing CO ₂ in industrial flue gas and reducing the total amount of industrial carbon emissions.

The technical solution of the present invention is: a method for improving the stability of clinker by using industrial flue gas, comprising the following steps:

Step 1. After the conventional cement raw meal is calcined at a high temperature by a conventional calcination process, it is naturally or accelerated cooled to room temperature to obtain conventional clinker;

Step 2, crushing or grinding the clinker prepared in step 1 to a particle size ≤ 1mm, and storing it in a clinker warehouse;

Step 3, injecting the flue gas containing CO ₂ into the clinker storehouse, ensuring that the CO ₂ concentration in the clinker storehouse is at least 80% of the injected flue gas, and producing clinker with excellent stability.

Specifically, the flue gas injection time in step 3 is 30 minutes to 360 minutes.

Specifically, the concentration of CO ₂ in the flue gas containing CO ₂ in step 3 is ≥20%.

Specifically, the flue gas containing CO ₂ includes the flue gas emitted from the cement industry or the flue gas emitted from the lime industry.

Specifically, the temperature of the flue gas in step 3 is 200°C to 500°C.

Beneficial effects of the present invention:

1) The present invention effectively reduces the content of the main components (ie, free calcium oxide and magnesium oxide) in the clinker that are unfavorable to the stability of cement through the carbonization treatment of the clinker produced by industrial flue gas, and correspondingly generates carbonic acid with stable performance. Salt provides a new way to improve or enhance the stability of clinker.

2) China, as a big cement country, also ranks first in the world in terms of cement clinker output, based on 0.8% of free calcium oxide and 3.50% of magnesium oxide, it can absorb 4.48% of CO ₂ when fully reacted, and the annual output of clinker in the country is 1.84 billion tons According to calculations, 82.4 million tons of CO ₂ can be absorbed. The 2021 China Carbon Market Annual Report shows that the average price of China's annual carbon allowances is 42.85 yuan/ton, which can indirectly reduce the carbon emission cost of the cement industry by 3.532 billion yuan, which has considerable development potential and prospects.

3) Using the high temperature in industrial flue gas, the secondary activation of clinker can be realized, and the hydration activity of clinker can be improved, which is beneficial to the improvement of clinker activity.

Description of drawings

Fig. 1 is the flow chart of the implementation of the method of the present invention.

Detailed ways

In view of the strict requirements on the stability of cement put forward by major projects, combined with the current national urgent needs for green and low-carbon transformation of high-carbon emission industries, and with the goal of clinker green, low-carbon, and high-quality preparation, the present invention proposes a method of using industrial The method for improving the stability of clinker by flue gas aims to effectively improve the stability of clinker while absorbing CO ₂ in industrial flue gas and reducing the total amount of industrial carbon emissions.

Carbon capture and utilization technology is known as one of the most effective measures to achieve carbon neutrality and carbon peaking goals. The low-cost capture or direct utilization of _CO2 in flue gas is the core goal of carbon capture and utilization technology . According to the theory of acid-base neutralization, free calcium oxide and magnesium oxide in clinker are typical highly active alkali metal oxides, which can theoretically react with other acid gases such as _CO2 to form carbonates with good stability, such as Calcium Carbonate and Magnesium Carbonate. It can improve the stability of clinker and reduce carbon emissions in the cement industry. Free calcium oxide in clinker is generally 0.3%~1.3%, with an average value of about 0.8%, and magnesium oxide is generally 1.0%~4.8%, with an average value of 3.50%. Based on 0.8% of free calcium oxide and 3.50% of magnesium oxide, 4.48% of CO ₂ can be absorbed when fully reacted, and 82.4 million tons of CO ₂ can be absorbed based on the national annual clinker output of 1.84 billion tons. According to the 2021 China Carbon Market Annual Report, The average price of China's annual carbon quota is 42.85 yuan/ton, which can indirectly reduce the carbon emission cost of the cement industry by 3.532 billion yuan, which has considerable development potential and prospects.

A method for improving the stability of clinker by using industrial flue gas, comprising the following steps:

Step 1. After the conventional cement raw meal is calcined at a high temperature by a conventional calcination process, it is naturally or accelerated cooled to room temperature to obtain conventional clinker;

Step 2, crushing or grinding the clinker prepared in step 1 to a particle size ≤ 1mm, and storing it in a clinker warehouse;

In the present invention, the purpose of crushing or grinding the clinker to a particle size ≤ 1mm is:

The rate of gas-solid reaction in the production and preparation process is related to the gas concentration and contact area at the same time. The reaction rate of free calcium oxide and magnesium oxide in the clinker and _CO2 is inversely proportional to the particle size or fineness of the clinker, that is, the finer the particle size or fineness The smaller, the quicker and fuller the response.

Step 3, injecting the flue gas containing CO ₂ into the clinker storehouse, ensuring that the CO ₂ concentration in the clinker storehouse is at least 80% of the injected flue gas, and producing clinker with excellent stability.

It is further defined that the flue gas injection time in step 3 is 30 minutes to 360 minutes.

It is further defined that the concentration of CO ₂ in the flue gas containing CO ₂ in step 3 is ≥20%.

Under the condition of high-concentration _CO2 atmosphere, the free calcium oxide and magnesium oxide in the silicate clinker will be gradually carbonized, that is, they will react with _CO2 to form calcium carbonate and magnesium carbonate.

Further defined, _CO2 -containing flue gas includes, but is not limited to, flue gas emitted from the cement industry or flue gas emitted from the lime industry.

It is further defined that the temperature of the flue gas in step 3 is 200°C to 500°C, which can reactivate the clinker to increase the hydration activity of the clinker.

Example 1

A method for improving the stability of clinker by using industrial flue gas. First, ordinary portland cement clinker is fired by conventional technology, and the clinker is quickly cooled to room temperature, crushed to a particle size of ≤1mm, and transferred to the clinker storage. The cement kiln flue gas is continuously fed into the clinker warehouse, the CO ₂ content of the flue gas is 24%, and the actual CO ₂ content in the warehouse is 21%. The modified ordinary Portland cement clinker was prepared after continuously feeding flue gas for 180 minutes. Then mix and grind according to the ratio of 94% clinker and 6% gypsum to make Portland cement.

Example 2

A method for improving the stability of clinker by using industrial flue gas. First, ordinary portland cement clinker is fired by conventional technology, and the clinker is quickly cooled to room temperature, crushed to a particle size of ≤1mm, and transferred to the clinker storage. The lime kiln flue gas is continuously fed into the clinker storehouse, the CO ₂ content of the flue gas is 36%, and the actual CO ₂ content in the warehouse is 29%. The modified ordinary Portland cement clinker was prepared after continuously feeding flue gas for 180 minutes. Then mix and grind according to the ratio of 94% clinker and 6% gypsum to make Portland cement.

Example 3

A method for improving the stability of clinker by using industrial flue gas. Firstly, medium-heat Portland cement clinker is fired by conventional technology, and the fired clinker is rapidly cooled to room temperature, crushed to a particle size of ≤1mm, and transferred to the clinker storage. The cement kiln flue gas is continuously fed into the clinker warehouse, the CO ₂ content of the flue gas is 26%, and the actual CO ₂ content in the warehouse is 22%. The modified medium-heat Portland cement clinker was prepared after continuously feeding flue gas for 180 minutes. Then mix and grind according to the ratio of 94% clinker and 6% gypsum to make Portland cement.

Example 4

A method for improving the stability of clinker by using industrial flue gas. Firstly, the low-heat Portland cement clinker is fired by the conventional process, and the burned clinker is rapidly cooled to room temperature, crushed to a particle size ≤ 1mm, and transferred to the clinker storage. The cement kiln flue gas is continuously fed into the clinker warehouse, the CO ₂ content of the flue gas is 29%, and the actual CO ₂ content in the warehouse is 23%. The modified low-heat Portland cement clinker was prepared after continuously feeding flue gas for 180 minutes. Then mix and grind according to the ratio of 94% clinker and 6% gypsum to make Portland cement.

The unmodified clinker used in Examples 1-4 was mixed at a ratio of 94% clinker and 6% gypsum and ground to prepare the cement of the control group. Determination of free calcium oxide (f-CaO) and free magnesium oxide (f-CaO) content according to GB/T 176-2017 cement chemical analysis method, water consumption, setting time and stability inspection according to GB/T 1346-2011 cement standard consistency Methods The stability of the cement in each example and control group was tested by Rayleigh clip method. The volume stability and free calcium oxide and free magnesium oxide contents of each embodiment and control group are shown in Table 1.

Table 1 Volume stability and free calcium oxide, free magnesium oxide content of each embodiment, control group

According to the reference GB/T 17671-1999 cement mortar strength test method (ISO method), the cement mortar strength test piece was made and the physical property test was carried out, and the physical properties of the examples and the control group were compared. The development of compressive strength of each embodiment and control group is shown in Table 2.

Table 2 each embodiment, control realize volume stability and calcium oxide content

The patent of the invention aims to use the free calcium oxide and magnesium oxide in the silicate clinker to absorb carbon dioxide in the industrial flue gas, realize the overall improvement of the stability and quality of the clinker, and at the same time achieve the goal of low-carbon preparation of the clinker, and improve the quality of the clinker It provides a new path for the low-carbon transformation of traditional high-carbon emission industries.

Regarding the content disclosed in this case, the following points need to be explained:

(1) The drawings of the embodiments disclosed in this case only relate to the structure involved in the embodiments disclosed in this case, other structures can refer to the general design;

(2) In the case of no conflict, the embodiments disclosed in this case and the features in the embodiments can be combined with each other to obtain new embodiments;

The above are only the specific implementation methods disclosed in this case, but the protection scope of the present disclosure is not limited thereto, and the protection scope disclosed in this case should be based on the protection scope of the claims.

Claims (5)

1. A method utilizing industrial flue gas to improve clinker stability, is characterized in that, comprises the following steps: Step 1. After the conventional cement raw meal is calcined at a high temperature by a conventional calcination process, it is naturally or accelerated cooled to room temperature to obtain conventional clinker; Step 2, crushing or grinding the clinker prepared in step 1 to a particle size ≤ 1mm, and storing it in a clinker warehouse; Step 3, injecting the flue gas containing CO ₂ into the clinker storehouse, ensuring that the CO ₂ concentration in the clinker storehouse is at least 80% of the injected flue gas, and producing clinker with excellent stability. 2. A method for improving the stability of clinker by using industrial flue gas according to claim 1, characterized in that, the flue gas injection time in step 3 is 30min~360min. 3. A method for improving the stability of clinker by using industrial flue gas according to claim 1, characterized in that, in step 3, the CO ₂ concentration in the CO ₂ -containing flue gas is ≥ 20%. 4. A method for improving the stability of clinker by utilizing industrial flue gas according to claim 1, characterized in that the _CO2 -containing flue gas comprises flue gas discharged from the cement industry or flue gas discharged from the lime industry. 5. A method for improving the stability of clinker by using industrial flue gas according to claim 1, characterized in that the temperature of the flue gas in step 3 is 200°C-500°C.

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