Patent Application
20240190764
The disclosure relates to the field of cement preparation, and more specifically, to a low-carbon cement clinker and a method for preparing the same.
Within Portland cement, the primary contributor to strength is the alite mineral (a solid solution of tricalcium silicate, C3S), which forms at approximately 1450° C., featuring a substantial CaO content up to 73.7%. Hence, the elevated carbon emissions associated with Portland cement clinker primarily stem from the high-temperature formation process of the alite minerals. When compared to belite (a solid solution of dicalcium silicate, C2S) that contains a 65.1% CaO and swiftly forms at temperatures exceeding 1250° C., belite demonstrates reduced carbon emissions along with a proportional decrease in energy consumption and carbon emissions. Anhydrous calcium sulfoaluminate (C4A3$) features a CaO content of 36.8% and forms at a lower temperature (1300° C.). Furthermore, calcium sulfosilicate (ternesite, C5S2$), containing 58.33% CaO, emerges from the reaction between belite and anhydrite at temperatures ranging from 1150 to 1250° C. Therefore, both of these mineral materials exhibit energy-saving properties and contribute to low emissions. By conducting thorough calculations of carbon emissions, it has been determined that the carbon emissions of different minerals, namely C3S, C2S, C4A3$, and C5S2$, amount to 579 kg/t, 511 kg/t, 216 kg/t, and 458 kg/t, respectively. Consequently, the advancement of a new low-carbon cement clinker, primarily composed of minerals such as C2S, C4A3$, and C5S2$, which have lower calcium content and reduced energy requirements, emerges as practical strategy for accomplishing carbon reduction within the cement industry.
Calcium sulfoaluminate cement clinker mainly consists of minerals such as C4A3$, C2S, and tetracalcium aluminoferrite (C4AF). Despite being classified as low-carbon cement clinker, the manufacturing of calcium sulfoaluminate cement clinker demands substantial utilization of non-renewable resources, particularly high-quality bauxite (Al2O3>60%). Consequently, the manufacturing process results in elevated expenses and restricts the broad-scale implementation of calcium sulfoaluminate cement clinker. Furthermore, calcium sulfoaluminate cement demonstrates limited strength growth during the later stages, and there is even a risk for decreased strength, which primarily qualifies calcium sulfoaluminate cement for use in urgent construction projects.
To address the aforementioned technical shortcomings, the disclosure augments the content of belite or incorporates ternesite to produce a low-carbon cement clinker. This results in an improved performance of the conventional calcium sulfoaluminate cement clinker as it undergoes the maturation and advancement processes following its production. The hydration of cement clinker involves intricate interactions among different compounds. For instance, the hydration products of C4A3$ stimulate the hydration of C5S2$, and excessive hydration products of C5S2$ will inhibit the hydration of C2S. As a result, it is crucial to plan and regulate the proportions of different minerals. The disclosure addresses the challenge of controlling the compositional ratio between minerals in the low-carbon cement clinker, achieving targeted and stable control to produce the low-carbon cement clinker with outstanding performance in both the early and later stages.
The disclosure provides a method for formulating and preparing a low-carbon cement clinker. The low-carbon cement clinker features reduced carbon emissions and outstanding performance, with higher strengths in both the early and late stages in comparison to ordinary Portland cement clinker.
The composition of the low-carbon cement clinker is defined by the specific ranges of values for the following parameters:
In a class of this embodiment, the low-carbon cement clinker comprises raw materials as follows:
A method for preparing the low-carbon cement clinker, comprising:
In a class of this embodiment, in 2), the specific values of the parameters are calculated using the following formulas:
where, five oxides CaO, Al2O3, SO3, SiO2, and Fe2O3 are expressed as percentages by mass; the limestone saturation coefficient Cs considers the content of SO3 to regulate the proportion of lime and silicate, and is adjusted based on the alkalinity coefficient C.
The following advantages are associated with the disclosure.
The low-carbon cement clinker demonstrates outstanding performance, comparable to or even exceeding that of the current Portland cement clinker. This highlights its promising versatility for broad implementation and as a feasible alternative to the ordinary Portland cement, which in turns contributes significantly to the sustainable advancement of the cement industry.
To further illustrate the disclosure, embodiments detailing a low-carbon cement clinker and a method for preparing the same are described below. It should be noted that the following embodiments are intended to describe and not to limit the disclosure.
The composition of the low-carbon cement clinker is defined by the specific ranges of values for the following parameters:
The low-carbon cement clinker comprises five types of raw materials, comprising:
A method for preparing the low-carbon cement clinker, comprising:
In a class of this embodiment, in 2), the specific values of the parameters are calculated using the following formulas:
where, five oxides CaO, Al2O3, SO3, SiO2, and Fe2O3 are expressed as percentages by mass; the limestone saturation coefficient Cs considers the content of SO3 to regulate the proportion of lime and silicate, and is adjusted based on the alkalinity coefficient C.
The requirement to define specific ranges of the parameter values for the oxide composition of the low-carbon cement clinker arises from the following considerations: the strength properties of the cement clinker depend on the interactive and cooperation of diverse minerals throughout the hydration procedure. The specific ranges ensure that the mineral composition of the low-carbon cement clinker is in an optimally balanced and well-matched state. While enhancing the reactivity of low-activity minerals such as calcium sulfoaluminate and belite in the low-carbon cement clinker, the specific ranges also ensure the optimal balance in the content ratios of crucial minerals, such as calcium sulfoaluminate, to minerals like free gypsum or belite in the low-carbon cement clinker. Moreover, the specific ranges achieve the optimal spatial and temporal coordination and collaboration between crystalline hydration products such as ettringite and gel-like hydration products like calcium silicate hydrate (C—S—H), ensuring excellent performance throughout the early, mid, and late-stage of the low-carbon cement clinker.
Compared to current methods that involves a secondary calcination step for the conventional cement clinkers containing minerals like calcium sulfoaluminate, the low-carbon cement clinker requires just a single calcination step. This simplifies the process, reduces energy use, decreases emissions, lowers costs, and improves production efficiency.
The disclosed method modifies the specific ranges of the parameter values for the cement clinker to control the mineral composition ratios in the low-carbon cement clinker. The early strength of the cement depends on rapid hydration of clinker mineral C4A3$, the mid-stage strength is aided by the hydration of C5S2$, and the later-stage strength primarily arises from the hydration of C2S. The hydration processes of various minerals in the cement clinker are interrelated rather than independent. Hence, a well-founded choice and regulation of mineral components in the cement clinker contribute to creating a low-carbon cement clinker with outstanding performance and application results.
To clarify the disclosure and enhance understanding of the technical solutions and benefits, the following will offer a detailed description of the disclosure using examples and accompanying illustrations.
Tables 1 show the oxide compositions of the raw materials used in the examples.
Tables 2 and 3 show rate values and corresponding oxide compositions for a low-carbon cement clinker prepared in the example.
The raw materials, comprising fly ash, phosphogypsum, limestone, and bauxite were finely ground. Following the specific rate values, the oxide compositions were established, and the raw materials are proportioned based on the oxide components. The raw materials were weighted, ground and mixed in a mill to form a raw mixture. The raw mixture was blend with a certain amount of water or alcohol, pressed into a circular thin cake with a diameter of 3 cm, and subsequently dried in a drying oven. Next, the circular thin cake was heated in a high-temperature electric furnace using a silicon molybdenum rod. The temperature was gradually increased at a rate of 5° C./min until it reached 1200° C., at which point it was held steady for 30 minutes. After heating, the circular thin cake was removed and swiftly cooled using airflow, resulting in the formation of a clinker block. The clinker block was then crushed and finely ground. Measurement revealed that the finely ground clinker left a residue of 8.9% on a 45 μm sieve.
Tables 4 and 5 show rate values and corresponding oxide compositions for a low-carbon cement clinker prepared in the example.
The raw materials, comprising fly ash, phosphogypsum, limestone, and bauxite were finely ground. Following the specific rate values, the oxide compositions were established, and the raw materials are proportioned based on the oxide components. The raw materials were weighted, ground and mixed in a mill to form a raw mixture. The raw mixture was blend with a certain amount of water or alcohol, pressed into a circular thin cake with a diameter of 10 cm, and subsequently dried in a drying oven. Next, the circular thin cake was heated in a high-temperature electric furnace using a silicon molybdenum rod. The temperature was gradually increased at a rate of 5° C./min until it reached 1250° ° C., at which point it was held steady for 60 minutes. After heating, the circular thin cake was removed and swiftly cooled using airflow, resulting in the formation of a clinker block. The clinker block was then crushed and finely ground. Measurement revealed that the finely ground clinker left a residue of 9.1% on a 45 μm sieve.
Tables 6 and 7 show rate values and corresponding oxide composition for a low-carbon cement clinker prepared in the example.
The raw materials, comprising fly ash, phosphogypsum, limestone, and bauxite were finely ground. Following the specific rate values, the oxide compositions were established, and the raw materials are proportioned based on the oxide components. The raw materials were weighted, ground and mixed in a mill to form a raw mixture. The raw mixture was blend with a certain amount of water or alcohol, pressed into a circular thin cake with a diameter of 10 cm, and subsequently dried in a drying oven. Next, the circular thin cake was heated in a high-temperature electric furnace using a silicon molybdenum rod. The temperature was gradually increased at a rate of 5° C./min until it reached 1300° ° C., at which point it was held steady for 50 minutes. After heating, the circular thin cake was removed and swiftly cooled using airflow, resulting in the formation of a clinker block. The clinker block was then crushed and finely ground. Measurement revealed that the finely ground clinker left a residue of 8.7% on a 45 μm sieve.
XRD analyses were performed on the low-carbon cement clinkers prepared in Examples 1 to 3. The scanning rate was set at 4°/min, using a step size of 0.01°. The results of the XRD analyses are shown in
In each example, the low-carbon cement clinker was supplemented with an appropriate quantity of gypsum, maintaining a water-to-binder ratio of 0.5 and a sand-to-binder ratio of 3. The resulting mixture was used for conducting a test on mortar strength. A reference cement was used for comparative purposes, undergoing the same mortar strength test while adhering to identical water-to-binder ratio and sand-to-binder ratio. The compressive strengths of both the reference cement and the cement mortars made from the low-carbon cement clinker in Examples 1-3 were evaluated at different curing periods, especially at 1 day, 3 days, 7 days, 28 days, and 90 days, as depicted in
It will be obvious to those skilled in the art that changes and modifications may be made, and therefore, the aim in the appended claims is to cover all such changes and modifications.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202211569679.7 | Dec 2022 | CN | national |
This application is a continuation-in-part of International Patent Application No. PCT/CN2023/111955 with an international filing date of Aug. 9, 2023, designating the United States, now pending, further claims foreign priority benefits to Chinese Patent Application No. 202211569679.7 filed Dec. 8, 2022. The contents of all of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference. Inquiries from the public to applicants or assignees concerning this document or the related applications should be directed to: Matthias Scholl P. C., Attn.: Dr. Matthias Scholl Esq., 245 First Street, 18th Floor, Cambridge, MA 02142.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2023/111955 | Aug 2023 | WO |
| Child | 18536139 | US |
