Cement kiln coal-saving agent using waste solid and waste liquid as well as preparation method and application of cement kiln coal-saving agent

Abstract

The invention belongs to the technical field of waste resource utilization and coal saving agents, and discloses a cement kiln coal saving agent using waste solid and waste liquid as well as a preparation method and application of the cement kiln coal saving agent. The cement kiln coal saving agent using the waste solid and waste liquid comprises the following raw materials in percentage by mass: 50-60% of iron-containing acidic waste liquid, 10-20% of red mud, 5-10% of a grinding aid dispersant, 1-3% of a sulfur-fixing agent and the balance of water. The iron-containing acid waste liquid and the red mud are used as main raw materials and matched with the grinding aid dispersant and the sulfur-fixing agent, the combustion efficiency of coal is improved through the combined action, no adverse effect is generated on the production process and performance of cement, and meanwhile harmless treatment and resource utilization of waste solid and waste liquid are achieved.

Description

Technical Field

[0001] This invention belongs to the field of waste resource utilization and coal-saving agent technology, specifically relating to a coal-saving agent for cement kilns utilizing waste solids and liquids, its preparation method, and its application. Background Technology

[0002] Coal, as the core fuel in cement clinker production, directly impacts the production efficiency, operating costs, and even core economic benefits of cement enterprises, making it a key factor influencing the stability and economics of the entire cement production process. In the clinker calcination stage, the heat released from coal combustion provides the necessary conditions for clinker burning, and its combustion efficiency directly determines the energy consumption level, thus significantly impacting the company's market competitiveness. However, with the advancement of global industrialization, coal consumption continues to rise. Furthermore, as a non-renewable resource, long-term large-scale mining has led to a continuous decline in coal reserves, resulting in an increasingly tight global coal supply. This situation not only drives up coal procurement costs but also brings severe raw material supply pressure and operational challenges to the cement industry, which is highly dependent on coal.

[0003] As a traditional high-energy-consuming industry, the cement industry has a huge demand for coal, and coal consumption costs account for a significant proportion of the total cost of cement production. Energy conservation and emission reduction have become core demands for the industry's sustainable development. Against this backdrop, improving coal combustion efficiency and reducing coal consumption through technological means has become an important path for cement companies to reduce costs, increase efficiency, and alleviate resource pressure. The research and application of coal-saving agents is a key breakthrough in achieving this goal, and it has crucial practical significance and strategic value for promoting the green and low-carbon transformation of the cement industry and advancing its sustainable development. Currently, most existing coal-saving agent products on the market are designed for industrial combustion scenarios such as boilers, making it difficult to fully adapt to the needs of cement production.

[0004] Meanwhile, the demand for resource utilization of industrial solid waste and wastewater is becoming increasingly urgent. Aluminum smelting solid waste, namely red mud, is a highly alkaline solid waste residue discharged during the extraction of alumina from bauxite. Due to the difficulty in removing the bound chemical alkalis and their high content, the harmless utilization of red mud has always been challenging. With the development of the aluminum industry, the amount of red mud discharged from alumina production is increasing daily, making the maximum resource utilization of red mud imperative. Furthermore, sludge treatment plants generate large amounts of wastewater during sludge treatment. The addition of acids and transition metal salts during the treatment process to precipitate harmful heavy metals in the sludge and wastewater results in high levels of acidic substances and transition metal ions. Direct discharge of this wastewater would pollute water bodies, soil, and other ecological environments. Its harmless treatment and resource recycling are also significant challenges facing the industry. Therefore, developing coal-saving agents for cement kilns that utilize waste solids and wastewater can not only meet the current energy-saving needs of the cement industry but also solve the disposal problems of these two types of waste, aligning with the concept of green development. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the shortcomings of the existing technology by providing a coal-saving agent for cement kilns that utilizes waste solids and liquids, as well as its preparation method and application. The agent uses iron-containing acidic waste liquid and red mud as the main raw materials, combined with grinding aids, dispersants and desulfurizers, to improve the combustion efficiency of coal. This not only has no adverse effect on the cement production process and its performance, but also achieves the harmless treatment and resource utilization of waste solids and liquids.

[0006] To solve the technical problem proposed in this invention, this invention provides a coal-saving agent for cement kilns that utilizes waste solids and liquids, comprising the following raw materials in the following mass percentages: 40%~60% iron-containing acidic waste liquid, 10%~20% red mud, 5%~10% grinding aid and dispersant, 1%~3% sulfur-fixing agent, and the remainder being water.

[0007] Preferably, the coal-saving agent for cement kilns comprises the following raw materials in the following mass percentages: 50%~60% iron-containing acidic waste liquid, 15%~20% red mud, 5%~8% grinding aid dispersant, 1%~2% sulfur-fixing agent, and the remainder being water.

[0008] In the above scheme, the pH of the iron-containing acidic wastewater is ≤1, the iron ion concentration is 20%~30%, and the sulfate ion concentration is 20%~30%. The iron-containing acidic wastewater is preferably wastewater generated from the acidification treatment of chemical sludge produced by wastewater treatment plants. The iron ions and sulfate ions in the wastewater originate from inorganic polymeric flocculants added during wastewater treatment, and the inorganic polymeric flocculant is preferably polyferric sulfate.

[0009] In the above scheme, the red mud is Bayer process red mud with a pH of 10-12, a water content of ≤8%, and a Fe2O3 content of 40%-60%, an Al2O3 content of 10%-20%, and a CaO content of 1%-10%.

[0010] In the above scheme, the particle size of the red mud is <1mm.

[0011] In the above scheme, the grinding aid dispersant is silicon dioxide modified with triethanolamine and sucrose fatty acid ester.

[0012] In the above scheme, the preparation method of the grinding aid dispersant is as follows: after uniformly dispersing silica in water, triethanolamine is first added, and a first reaction is carried out under stirring and heating conditions. Then, sucrose fatty acid ester is added, and a second reaction is carried out under stirring and heating conditions to obtain the grinding aid dispersant.

[0013] Furthermore, the particle size of the silica is <10μm.

[0014] Furthermore, the mass ratio of the silica to the volume of water is 1 g: (30~70) mL.

[0015] Furthermore, the mass ratio of triethanolamine to silicon dioxide is (5~10):1.

[0016] Furthermore, the reaction temperature of the primary reaction is 50~70℃, and the reaction time is 30~60min.

[0017] Furthermore, the mass ratio of the sucrose fatty acid ester to silicon dioxide is (5~10):1.

[0018] Furthermore, the secondary reaction is carried out at a temperature of 60-80°C for 1-2 hours.

[0019] In the above scheme, the sulfur-fixing agent is a mixture of nano-titanium dioxide, calcium carbonate and cerium oxide.

[0020] Furthermore, the mass ratio of the nano-titanium dioxide, calcium carbonate, and cerium oxide is (1~2):(0.5~1):1.

[0021] Furthermore, the particle size of the nano-titanium dioxide is 60~80nm.

[0022] Furthermore, the calcium carbonate has a particle size of <10 μm.

[0023] Furthermore, the cerium oxide has a particle size of <10 μm.

[0024] This invention also provides a method for preparing a coal-saving agent for cement kilns using waste solids and liquids, comprising the following steps: First, add grinding aid, dispersant, desulfurizer and water to the iron-containing acidic waste liquid and stir evenly. Then add red mud and stir evenly. The resulting suspension is the coal-saving agent for cement kilns.

[0025] The present invention also provides an application of a coal-saving agent for cement kilns using waste solids and liquids. The application method is as follows: the coal-saving agent for cement kilns is sprayed onto the coal blocks before grinding.

[0026] In the above scheme, the amount of coal-saving agent sprayed in the cement kiln is 0.08% to 0.1% of the coal mass.

[0027] The main concept and principle of this invention are as follows: The resource utilization of iron-containing acidic wastewater and red mud is a challenging problem in existing technologies. For example, applying iron-containing acidic wastewater alone to coal-saving agents in cement kilns results in excessive acidity that accelerates machine wear. Similarly, applying red mud alone can easily lead to efflorescence in the hardened cement, and the metal ions in red mud exist in the form of solid oxides. Incomplete reactions can cause the metal ions to accumulate internally, leading to severe scaling and even blockages and production shutdowns. This invention combines the two. The addition of red mud absorbs excess acidic substances from the iron-containing acidic wastewater, converting the metal oxides in the red mud into ionic states. Ionic metals are more suitable for oxidation-reduction cycles, thus accelerating coal combustion. Furthermore, the alkalinity of the red mud itself is reduced. This combination accelerates coal combustion while reducing the impact of acidity and alkalinity on the machinery. Ferric sulfate in the iron-containing acidic wastewater decomposes at high temperatures to produce active oxygen and porous iron oxides, directly oxidizing the combustible components in the pulverized coal and lowering the ignition point. Red mud itself is rich in metal oxides such as Fe2O3 and Al2O3. These components have catalytic activity and can promote the pyrolysis of coal and the combustion of coke. The ferric sulfate in the iron-containing acidic waste liquid produces a synergistic catalytic effect with the metal oxides (especially iron oxides) in the red mud, which has higher catalytic activity than single components and promotes more complete combustion of coal.

[0028] However, red mud is a solid with a complex composition, while sludge wastewater is a liquid containing both inorganic and organic solutions. Direct mixing of the two does not result in complete dissolution, leading to sedimentation and stratification at the bottom. To address this, this invention introduces a grinding aid dispersant to improve the situation through the dispersing effect of silica. However, unmodified silica particles are prone to agglomeration, which weakens their positive effects. Therefore, triethanolamine and sucrose fatty acid esters are used to modify silica. The addition of triethanolamine helps break up silica agglomerates and preliminarily modifies its surface through adsorption or weak interactions. The basic groups of triethanolamine interact weakly with the hydroxyl groups on the silica surface, preventing particle agglomeration through steric hindrance. Sucrose fatty acid esters provide physical coating and functionalization. Their hydrophilic sucrose groups are anchored on the silica surface, which has been preliminarily activated by triethanolamine, while the hydrophobic long fatty acid chains extend outward to form an organic molecular layer, reducing the surface tension at the oil-water interface and solving the stratification problem after mixing red mud and iron-containing acidic wastewater. The unmodified triethanolamine and sucrose fatty acid esters in the grinding aid dispersant have a synergistic effect. When added to coal, they produce a "wedge-crack" effect, reducing the surface energy and hardness of coal particles. At the same time, they are adsorbed on the surface of coal particles. Through the steric hindrance effect and the regulation of surface charge, electrostatic repulsion is generated between coal particles, thereby making the coal powder relatively dispersed and easier to burn.

[0029] In addition, a sulfur-fixing agent was introduced. After the sulfur-fixing agent was mixed with red mud, the alkalinity of the red mud provided a good alkaline chemical environment for sulfur fixation, which can achieve simultaneous and efficient sulfur fixation and reduce SO2 emissions. The cerium oxide in the sulfur-fixing agent stores and releases oxygen and catalyzes the reaction. The ferric sulfate in the red mud and iron-containing acidic wastewater accelerates SO2 oxidation. The nano-titanium dioxide in the sulfur-fixing agent serves as a carrier. The three work together to solve the problem of low efficiency in high-temperature sulfur fixation and achieve ultra-high efficiency.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses iron-containing acidic wastewater and red mud as main raw materials, combined with grinding aids, dispersants, and desulfurizing agents, to prepare a coal-saving agent for cement kilns. This agent significantly improves coal combustion efficiency, has no adverse effects on the cement production process or its performance, and simultaneously achieves the harmless treatment and resource utilization of waste solids and liquids. The process route is simple and easy to operate, the raw materials are widely available and inexpensive, requiring no complex production equipment or high investment, making it easy to achieve large-scale industrial production. Its widespread application can not only promote energy conservation, emission reduction, and green transformation in the cement industry, but also drive the resource utilization of waste from related industries such as aluminum and chemicals, promoting the coordinated development of the industrial chain, and has significant social, environmental, and economic benefits. Detailed Implementation

[0031] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0032] In the following examples, the iron-containing acidic wastewater used is wastewater generated from the acidification treatment of chemical sludge produced by sewage treatment plants. It contains a high concentration of iron ions and sulfate ions, which are derived from the inorganic polymeric flocculant polyferric sulfate added during sewage treatment. Its pH is 1, the iron ion concentration is 25%, and the sulfate ion concentration is 25%. The red mud used is Bayer process red mud with a pH of 10, a water content of 5%, a Fe2O3 content of 50%, an Al2O3 content of 15%, a CaO content of 3%, and a particle size of 50-100 μm. The silica used has a particle size of 1-5 μm, the nano-titanium dioxide has a particle size of 70 nm, the calcium carbonate has a particle size of 1-5 μm, and the cerium oxide has a particle size of 1-5 μm.

[0033] Example 1 A coal-saving agent for cement kilns utilizing waste solids and liquids comprises, by mass percentage: 40% iron-containing acidic waste liquid, 10% red mud, 10% grinding aid and dispersant, 3% desulfurizing agent, and 37% water. In preparation, the grinding aid and dispersant, desulfurizing agent, and water are first added to the iron-containing acidic waste liquid and stirred until homogeneous. Then, the red mud is added and stirred until homogeneous again to obtain the coal-saving agent for cement kilns. Wherein: The grinding aid dispersant is silicon dioxide modified with triethanolamine and sucrose fatty acid ester. The specific preparation method is as follows: After uniformly dispersing silicon dioxide in water, the mass ratio of silicon dioxide to water is 1g:50mL. First, triethanolamine is added, with a mass ratio of triethanolamine to silicon dioxide of 7:1. The mixture is stirred and reacted at 60℃ for 30min. Then, sucrose fatty acid ester is added, with a mass ratio of sucrose fatty acid ester to silicon dioxide of 8:1. The mixture is stirred and reacted at 80℃ for 1h.

[0034] The sulfur-fixing agent is a mixture of nano-titanium dioxide, calcium carbonate, and cerium oxide. The specific preparation method is as follows: mix nano-titanium dioxide, calcium carbonate, and cerium oxide evenly in a mass ratio of 1:0.5:1.

[0035] Example 2 A coal-saving agent for cement kilns utilizing waste solids and liquids comprises, by mass percentage: 60% iron-containing acidic waste liquid, 20% red mud, 5% grinding aid and dispersant, 1% desulfurizing agent, and 14% water. In preparation, the grinding aid and dispersant, desulfurizing agent, and water are first added to the iron-containing acidic waste liquid and stirred until homogeneous. Then, the red mud is added and stirred until homogeneous again to obtain the coal-saving agent for cement kilns. Wherein: The grinding aid dispersant is silicon dioxide modified with triethanolamine and sucrose fatty acid ester. The specific preparation method is as follows: After uniformly dispersing silicon dioxide in water, the mass ratio of silicon dioxide to water is 1g:50mL. First, triethanolamine is added, and the mass ratio of triethanolamine to silicon dioxide is 6:1. The mixture is stirred and reacted at 70℃ for 40min. Then, sucrose fatty acid ester is added, and the mass ratio of sucrose fatty acid ester to silicon dioxide is 9:1. The mixture is stirred and reacted at 70℃ for 1.5h.

[0036] The sulfur-fixing agent is a mixture of nano-titanium dioxide, calcium carbonate, and cerium oxide. The specific preparation method is as follows: mix nano-titanium dioxide, calcium carbonate, and cerium oxide evenly in a mass ratio of 1.5:1:1.

[0037] Example 3 A coal-saving agent for cement kilns utilizing waste solids and liquids comprises, by mass percentage: 55% iron-containing acidic waste liquid, 15% red mud, 8% grinding aid and dispersant, 2% desulfurizing agent, and 20% water. In preparation, the grinding aid and dispersant, desulfurizing agent, and water are first added to the iron-containing acidic waste liquid and stirred until homogeneous. Then, the red mud is added and stirred until homogeneous again to obtain the coal-saving agent for cement kilns. Wherein: The grinding aid dispersant is silicon dioxide modified with triethanolamine and sucrose fatty acid ester. The specific preparation method is as follows: After uniformly dispersing silicon dioxide in water, the mass ratio of silicon dioxide to water is 1g:50mL. First, triethanolamine is added, and the mass ratio of triethanolamine to silicon dioxide is 10:1. The mixture is stirred and reacted at 50℃ for 60min. Then, sucrose fatty acid ester is added, and the mass ratio of sucrose fatty acid ester to silicon dioxide is 5:1. The mixture is stirred and reacted at 60℃ for 2h.

[0038] The sulfur-fixing agent is a mixture of nano-titanium dioxide, calcium carbonate, and cerium oxide. The specific preparation method is as follows: mix nano-titanium dioxide, calcium carbonate, and cerium oxide evenly in a mass ratio of 2:0.5:1.

[0039] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that no red mud is added.

[0040] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that no iron-containing acidic waste liquid is added.

[0041] Comparative Example 3 The only difference between Comparative Example 3 and Example 2 is that no grinding aid or dispersant is added.

[0042] Comparative Example 4 The only difference between Comparative Example 4 and Example 2 is that unmodified silica was used directly as a grinding aid dispersant.

[0043] Comparative Example 5 The only difference between Comparative Example 5 and Example 2 is that silica, triethanolamine and sucrose fatty acid esters are mixed evenly at room temperature as a grinding aid dispersant.

[0044] Comparative Example 6 Comparative Example 6 used a coal-saving agent for cement kilns from the market, whose main components are a mixture of transition metal compounds such as copper and manganese and organic matter.

[0045] Comparative Example 7 Comparative Example 7 used a traditional boiler coal-saving agent, whose main components are a mixture of alkali metal compounds such as sodium chloride and other organic substances.

[0046] The coal-saving agents of each embodiment and each comparative example were applied separately. The application method was as follows: the coal-saving agent was sprayed onto the coal block before grinding, and the spraying amount was 0.1% of the coal block mass. Then, the coal blocks were ground together to below 90μm and sent into the cement kiln for production and coal combustion testing. A benchmark group without coal-saving agent was set up. The test results of each group are shown in Table 1.

[0047] Table 1 Performance Test Results

[0048] Compared to the baseline group, the examples showed significantly lower ignition and burnout temperatures, indicating that the addition of the combustion aid made the pulverized coal easier and more completely combustible. The decrease in combustion intensity indicated that the combustion aid improved the localized high temperature during pulverized coal combustion. The increase in the combustion characteristic index and maximum combustion rate showed the enhancement of the overall combustion performance of pulverized coal by the combustion aid. Comparative Examples 1 and 2 did not add red mud or iron-containing acidic waste liquid. Compared to the examples, the decrease in ignition and burnout temperatures relative to the baseline was smaller, and the effects of other thermogravimetric data such as combustion intensity were not as good as those of the examples. Furthermore, the addition of iron-containing acidic waste liquid or red mud alone had a certain negative impact on cement production. Comparative Example 3 did not add grinding aid dispersant, Comparative Example 4 used silica as a grinding aid dispersant but did not modify it, and Comparative Example 5 used a simple mixture of silica, triethanolamine, and sucrose fatty acid ester as a grinding aid dispersant. Compared to the examples, the three groups showed smaller decreases in ignition and burnout temperatures relative to the baseline, higher combustion intensity, and lower combustion characteristic index and maximum combustion rate. Among them, Comparative Example 3, without the addition of grinding aid and dispersant, performed the worst in thermogravimetric data. Comparative Examples 4 and 5, one without modification of silica and the other simply mixed, neither demonstrated the effect of modified silica. In contrast, the embodiments modified silica by utilizing the weak interaction between the basic groups of triethanolamine and hydroxyl groups, preventing coal particle agglomeration through steric hindrance. Furthermore, the hydrophilic sucrose groups of sucrose fatty acid esters provided physical coating and functionalization, reducing the surface tension at the oil-water interface. This improved the combustion environment of the coal powder and promoted the function of other components of the combustion aid, thus increasing overall combustion efficiency. Comparative Examples 6 and 7 are similar products on the market and traditional coal-saving agents for boilers; their improvement in coal powder combustion effect is far inferior to that of the embodiments of this invention.

[0049] The above embodiments are merely examples for clear illustration and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, and any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A coal-saving agent for cement kilns utilizing waste solids and liquids, characterized in that, The raw materials include the following percentages by mass: 40%~60% iron-containing acidic waste liquid, 10%~20% red mud, 5%~10% grinding aid dispersant, 1%~3% sulfur fixative, and the remainder is water; the grinding aid dispersant is silicon dioxide modified with triethanolamine and sucrose fatty acid ester; the sulfur fixative is a mixture of nano titanium dioxide, calcium carbonate and cerium oxide.

2. The coal-saving agent for cement kilns utilizing waste solids and liquids according to claim 1, characterized in that, The coal-saving agent for cement kilns comprises the following raw materials in the following mass percentages: 50%~60% iron-containing acidic waste liquid, 15%~20% red mud, 5%~8% grinding aid dispersant, 1%~2% sulfur-fixing agent, and the remainder is water.

3. The coal-saving agent for cement kilns utilizing waste solids and liquids according to claim 1, characterized in that, The grinding aid dispersant is prepared by: uniformly dispersing silica in water, first adding triethanolamine, and carrying out a first reaction under stirring and heating conditions, then adding sucrose fatty acid ester, and carrying out a second reaction under stirring and heating conditions to obtain the grinding aid dispersant.

4. The coal-saving agent for cement kilns utilizing waste solids and liquids according to claim 3, characterized in that, The silica has a particle size of <10μm; the mass ratio of silica to water is 1g:(30~70)mL; the mass ratio of triethanolamine to silica is (5~10):1; the mass ratio of sucrose fatty acid ester to silica is (5~10):

1.

5. The coal-saving agent for cement kilns utilizing waste solids and liquids according to claim 3, characterized in that, The primary reaction is carried out at a temperature of 50-70°C for 30-60 minutes; the secondary reaction is carried out at a temperature of 60-80°C for 1-2 hours.

6. The coal-saving agent for cement kilns utilizing waste solids and liquids according to claim 1, characterized in that, The mass ratio of nano-titanium dioxide, calcium carbonate, and cerium oxide is (1~2):(0.5~1):1; the particle size of the nano-titanium dioxide is 60~80nm; the particle size of the calcium carbonate is <10μm; and the particle size of the cerium oxide is <10μm.

7. The coal-saving agent for cement kilns utilizing waste solids and liquids according to claim 1, characterized in that, The iron-containing acidic waste liquid has a pH ≤ 1, an iron ion concentration of 20%~30%, and a sulfate ion concentration of 20%~30%.

8. The coal-saving agent for cement kilns utilizing waste solids and liquids according to claim 1, characterized in that, The red mud is Bayer process red mud with a particle size <1mm, pH of 10~12, moisture content ≤8%, Fe2O3 content of 40%~60%, Al2O3 content of 10%~20%, and CaO content of 1%~10%.

9. A method for preparing a coal-saving agent for cement kilns utilizing waste solids and liquids as described in any one of claims 1 to 8, characterized in that, Includes the following steps: First, add grinding aid, dispersant, desulfurizer and water to the iron-containing acidic waste liquid and stir evenly. Then add red mud and stir evenly. The resulting suspension is the coal-saving agent for cement kilns.

10. The application of a coal-saving agent for cement kilns utilizing waste solids and liquids as described in any one of claims 1 to 8, characterized in that, The coal-saving agent for cement kilns is sprayed onto the coal blocks before grinding, with the spraying amount being 0.08% to 0.1% of the coal block mass.

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