Method for producing cement mineralizer from ardealite in zero-carbon manner

Abstract

The invention discloses a method for producing a cement mineralizer from ardealite in a zero-carbon manner, which comprises the following steps: adding water, a precipitator, an interface agent and a carbon affinity agent into ardealite, uniformly mixing to obtain ore pulp, pumping the ore pulp into a flotation column for flotation, and carrying out filter pressing on foams discharged from the top of the flotation column to obtain the cement mineralizer, and screening underflow discharged from the bottom of the flotation column to obtain quartz slag and purified gypsum, adding a dehydrating agent into the purified gypsum, uniformly mixing, and carrying out filter pressing to obtain the gypsum retarder. The method has the characteristics of short flow, high separation efficiency, low cost and environmental protection.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of building materials, in particular to a cement mineralizer produced by extracting fluorine and phosphorus from phosphogypsum. BACKGROUND

[0002] Cement is an important basic raw material for national economic construction, and the sustainable development of the cement industry is an important foundation and rigid demand to support social development. However, cement is also one of the main sources of carbon emissions, and high energy consumption and high carbon emissions have become a bottleneck restricting the sustainable and high-quality development of the cement industry. The cement industry is facing great pressure to save coal and reduce carbon.

[0003] The sintering of cement clinker is a complex reaction process. The solid phase reaction is first carried out, and then the solid-liquid reaction process begins with the increase of temperature and the formation of liquid phase. In the production process of clinker, the decomposition of CaCO3 and the formation of liquid phase consume a large amount of energy, and the reaction speed of each process in the reaction process of clinker is relatively slow, which affects the yield and quality of clinker. By adding a small amount of mineralizer to the raw material and then calcining, the burnability of the raw material can be improved, the yield and quality of the clinker can be improved, and the energy consumption can be reduced.

[0004] Mineralizers are divided into single mineralizers and composite mineralizers according to their types. Single mineralizer is a mineralizer that only plays a mineralization role (such as CaF2). Composite mineralizer is two or more mineralizers used at the same time (such as CaSO4, CaF2, and Ca3(PO4)2 added at the same time). Generally, the mineralization effect of composite mineralizer with reasonable proportion is better than that of single mineralizer.

[0005] Phosphogypsum is a by-product of the wet-process phosphoric acid industry, and its main component is gypsum. For every ton of phosphate fertilizer (calculated as P2O5), 4.5-5.0 tons of phosphogypsum is produced. In 2021, China's phosphogypsum production was 75 million tons, of which 30 million tons were utilized, with a comprehensive utilization rate of 40.0%. The remaining part was stored locally, and the storage amount of phosphogypsum in China has exceeded 830 million tons. Phosphogypsum contains free phosphoric acid, organic matter, fluorides and other impurities. Large-scale storage will pose an environmental safety risk. How to reasonably utilize and dispose of phosphogypsum is a difficult problem faced by the sustainable development of the wet-process phosphoric acid industry. Although the patent "A method for physical and chemical whitening of phosphogypsum and preparation of cementitious materials" separates and processes phosphogypsum, it does not achieve high-quality utilization of phosphorus and fluorine. The phosphogypsum content in black phosphogypsum is relatively high, and it is only used as gypsum products. The air distribution plate is used inside the flotation column in this patent, which cannot produce fine bubbles, and the air distribution plate is easy to block, affecting normal production [Tan Hongbin, Ma Xiaoling, Dong Faqin. A method for physical and chemical whitening of phosphogypsum and preparation of cementitious materials: China, 201910186821.1[P]. 2019.3.13]. Although the use of packed flotation columns can produce fine bubbles, the packing material occupies the volume of the column, and the agglomerated phosphogypsum also blocks the channel, affecting normal production, and increasing cost and operating energy consumption. The patent "A method for utilizing organic matter in phosphogypsum" collects the organic matter in phosphogypsum and uses it as a raw material for biogas production, but it does not achieve high-quality utilization of phosphorus and fluorine. The patent uses conventional equipment, and the flotation efficiency is low [Tan Hongbin, Liu Mingxue, Dong Faqin, et al. A method for utilizing organic matter in phosphogypsum: China, 201810308594.0[P]. 2018.4.9].

[0006] The present application provides a method for producing cement mineralizer from phosphogypsum, which can realize the cascade high-quality utilization of phosphogypsum and avoid the use of natural mineralizers, thereby saving resources. SUMMARY

[0007] To solve the problems in the prior art, the present application provides a method for producing cement mineralizer from phosphogypsum with zero carbon emission. Compared with the prior art, the present method has the characteristics of short process, high efficiency, low cost and green environmental protection, and has significant economic and social benefits.

[0008] A method for producing cement mineralizer from phosphogypsum with zero carbon emission, which comprises the following steps in sequence:

[0009] The phosphogypsum is mixed with water, a precipitant, an interface agent, and a carbonophilic agent to obtain a slurry, the slurry is pumped into a flotation column for flotation, the foam discharged from the top of the flotation column is filtered to obtain a cement mineralizer, the underflow discharged from the bottom of the flotation column is screened to obtain quartz residue and purified gypsum, and a dehydrating agent is added to the purified gypsum to obtain a gypsum retarder after mixing and filtering; the precipitant is one of calcined raw material and steel slag powder; the interface agent is one of sodium dodecyl sulfonate, triethanolamine soap, and cresylic acid; the carbonophilic agent is one of palmitic acid, oleic acid, and diesel oil; the dehydrating agent is one of polyoxyethylene, melamine, and anthracene sulfonic acid formaldehyde condensate; the flotation column is composed of an ultrasonic generator, a column, a bubble generator, and a foam collecting tank; and the power used in the production process is one of photovoltaic power and wind power.

[0010] The water is added in an amount of 300-500% of the mass of the phosphogypsum.

[0011] The precipitant is added in an amount of 3-8% of the mass of the phosphogypsum.

[0012] The interface agent is added in an amount of 0.05-0.5% of the mass of the phosphogypsum.

[0013] The carbonophilic agent is added in an amount of 0.05-0.5% of the mass of the phosphogypsum.

[0014] The dehydrating agent is added in an amount of 0.05-0.5% of the mass of the phosphogypsum.

[0015] Compared with the prior art, the present application has the following advantages:

[0016] The precipitant is one of calcined raw material and steel slag powder, and the precipitant generates calcium phosphate and calcium fluoride with soluble phosphorus and soluble fluorine, which are used as the cement mineralizer in the flotation process, thus being beneficial to the resource utilization of phosphorus and fluorine. The calcined raw material is raw material discharged from a cement plant, and the main component is calcium oxide, which is beneficial to reducing the production cost of the mineralizer. The steel slag powder is fine powder ground from steel slag, and the main components are calcium oxide, magnesium oxide, and silicon oxide, which are beneficial to resource recycling.

[0017] The interface agent is one of sodium dodecyl sulfonate, triethanolamine soap, and cresylic acid, and the interface agent can improve the surface tension of water, which is beneficial to the generation of micro-bubbles after air is introduced, and is beneficial to the flotation separation of impurities in the phosphogypsum.

[0018] The carbonophilic agent is one of palmitic acid, oleic acid, and diesel oil, and the carbonophilic agent has poor compatibility with water, can be adsorbed on the surface of organic matters, fine particle impurities such as calcium phosphate and calcium fluoride in the phosphogypsum, changes the surface properties of the impurities, and makes the impurities hydrophobic and easy to float with bubbles, thus realizing the high-quality utilization of calcium phosphate and calcium fluoride.

[0019] The bottom stream discharged from the bottom of the flotation column is screened to obtain quartz residue and purified gypsum. The quartz residue mainly contains quartz and is used as fine aggregate of concrete or road material.

[0020] One of polyoxyethylene, melamine, anthracene sulfonic acid formaldehyde; the dehydrating agent is adsorbed on the surface of the purified gypsum to squeeze out the adsorbed water on the surface of the gypsum and reduce the water content of the gypsum; without the dehydrating agent, the water content of the purified gypsum after pressure filtration is 16%; under the same pressure filtration of the pressure filter, after the dehydrating agent is added, the water content of the gypsum retarder is 7-13%, which avoids the high water content of the gypsum retarder, the poor sliding of the gypsum retarder in the discharging pipeline and the influence on production. The polyoxyethylene dehydrating agent is prepared by introducing polyoxyethylene on the styrene-maleic acid copolymer with tetrahydrofuran as the solvent. The amino sulfonic acid dehydrating agent is prepared by using sodium p-aminobenzenesulfonate and phenol as raw materials through addition and polycondensation reaction to finally form a macromolecule with a certain degree of polymerization. The anthracene sulfonic acid formaldehyde dehydrating agent is prepared by sulfonating anthracene with concentrated sulfuric acid, then cooling the reaction product and hydrolyzing, and then condensing the sulfonated anthracene with formaldehyde.

[0021] The flotation column is composed of an ultrasonic generator, a column, a bubble generator, a foam collecting tank and a feeding pipe.

[0022] The ultrasonic generator is a common ultrasonic generator used in ultrasonic cleaners, which is used to generate ultrasonic waves to the ore pulp in the flotation column. The use of ultrasonic waves helps to break the agglomerates in the ore pulp; and through the stirring and vibration of the ultrasonic waves, the entrainment of the floating foam to the gypsum is reduced, and the content of the gypsum in the cement mineralizer is reduced; too high content of the gypsum in the mineralizer will increase the concentration of sulfur dioxide in the tail gas of the cement kiln, which will affect the environment. The ultrasonic waves can also improve the surface chemical properties of the minerals, promote the emulsification of the reagents, increase the use efficiency of the reagents and reduce the amount of the reagents.

[0023] The column is a hollow metal cylinder, which is made of one of stainless steel and carbon steel lined with polytetrafluoroethylene, both of which can achieve the purpose. The ultrasonic generator, the bubble generator, the foam collecting tank and the feeding pipe are all installed on the column.

[0024] The bubble generator is one of an air direct type bubble generator and a gas-liquid mixed flow type bubble generator, both of which can achieve the purpose. The bubble generator is located at the lower part of the column, and the number of bubble generators is arranged according to the cross-sectional area of the column. One to five bubble generators are arranged per square meter of the cross-sectional area of the column. The bubble generator generates a large number of small bubbles that can be uniformly dispersed in the column, avoiding strong turbulent stirring of the gas flow to the ore pulp.

[0025] The air direct bubble generator is composed of a needle valve, a bubble spray hole, and an automatic closing device. High pressure gas is sprayed at high speed from the throat of the nozzle, and a large number of small diameter bubbles are formed through shearing action of the ore pulp. The automatic closing device can ensure that the spray pipe remains closed and sealed when not pressurized or when unexpected pressure loss occurs, preventing ore pulp from flowing in and ensuring that the gas dispersion system does not be affected in normal operation due to blockage. The spray pipe nozzle has a variety of different models available for use, and by adjusting the number of spray pipe openings and the size of the spray pipe nozzle, the air supply pressure and flow rate of the flotation column can be adjusted to ensure sufficient air dispersion in the column. The bubble generator can be easily inserted and extracted during operation of the flotation column, making it convenient for inspection and maintenance.

[0026] The ore pulp mixed flow bubble generator includes a pulp nozzle, an air suction chamber, a throat pipe, a throat pipe outlet section, and a diffusion pipe. The working principle is that the high-speed injected ore pulp mixes with air in the throat pipe, and a large number of bubbles are generated when the mixture is discharged through the diffusion pipe. From the perspective of fluid mechanics, the circulating ore pulp is used as the working medium, and the pressurized working medium is sprayed from the nozzle to form a high-speed jet. In the air suction chamber, negative pressure is generated to suck and compress air, i.e., air is sucked into the jet, the surface of the jet rubs against the surrounding air, and the air is carried away by the high-speed jet. The fluid particles and air particles exchange positions in the throat pipe, and finally are discharged at high speed through the diffusion pipe.

[0027] The foam collection tank is located at the upper part of the column, and its outer edge is lower than the column. The bubbles in the column flow into the collection tank, and the material carried by the bubbles is collected. The collected material is finally discharged from the outlet at the low end of the tank.

[0028] The flotation column has the characteristics of energy saving and high separation efficiency. The mineralizing agent floated from the phosphogypsum is a composite mineralizing agent containing calcium fluoride, calcium phosphate, gypsum, and alkali. When the dosage of the mineralizing agent in cement raw materials is 3-10wt%, the calcination temperature of cement clinker is reduced by 50-100℃, and the carbon reduction effect is good.

[0029] The organic matter content in the gypsum retarder is less than 0.01%, and it does not contain soluble phosphorus and soluble fluorine. Its effect on the performance of cement clinker is equivalent to that of natural gypsum. The strength of some examples 3d is slightly better than that of cement with natural gypsum as a retarder, and the maximum difference in initial setting time is 12 minutes, which avoids the disadvantages of low early strength and long setting time of cement when using phosphogypsum as a retarder. The performance of cement clinker also includes standard consistency water consumption, cement mortar fluidity, and cement compatibility with water reducing agent. Compared with cement with natural gypsum as a retarder, the difference is less than 1%. The floated gypsum retarder can replace natural gypsum, thereby protecting the natural gypsum resource.

[0030] The waste water generated by filtering and purifying the foam and the gypsum filter press can be used as the water added to the phosphogypsum, so that the water is recycled. Since the waste water does not contain soluble phosphorus, soluble fluorine and other impurities, it does not need to be treated and can be directly recycled and utilized, thereby avoiding the cost of waste water treatment. The filter press used in the filtering is a plate and frame filter press. Since the precipitant is added to the phosphogypsum, the ore pulp is strongly alkaline with a pH value of 12.5 or above, which is beneficial to the generation of calcium phosphate and calcium fluoride; and the corrosion to the metal equipment is weak, which is beneficial to the improvement of the service life of the equipment and the reduction of the production cost.

[0031] The power used in the production process is green power, i.e. one of photovoltaic power and wind power, and the purpose can be achieved; the devices for power consumption in the production process mainly include a bubble generator, an ultrasonic generator, an ore pulp pump, a liquid level controller and a control system; the green power has the characteristics of not emitting carbon dioxide and zero carbon; the storage of the green power adopts sodium ion batteries, which guarantees the stable power consumption in production and also has the characteristic of low cost. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The figure is a structural schematic diagram of the flotation column involved in the present application. DETAILED DESCRIPTION

[0033] The present application will be further described in detail below in combination with specific embodiments.

[0034] The present application discloses a method for producing a cement mineralizer by using phosphogypsum with zero carbon, which comprises the following steps: adding water, a precipitant, an interface agent and a carbonophilic agent into the phosphogypsum to mix uniformly to obtain an ore pulp, pumping the ore pulp into a flotation column for flotation, filtering the foam discharged from the top of the flotation column to obtain the cement mineralizer, and screening the underflow discharged from the bottom of the flotation column to obtain quartz residue and purified gypsum; and adding a dewatering agent into the purified gypsum to mix uniformly and filter to obtain a gypsum retarder. The adding amounts of the water, the precipitant, the interface agent and the carbonophilic agent are shown in Table 1. The calcium phosphate and calcium fluoride contents in the dewatering agent and the mineralizer, the water content in the gypsum retarder, the initial setting time of the Portland cement with 4.5wt% of the gypsum retarder added and the 3d compressive strength are shown in Table 2.

[0035] Table 1

[0036]

[0037] Table 2

[0038]

[0039]

[0040] Note: The initial setting time of the Portland cement prepared by using the same cement clinker and adding 4.5wt% of natural gypsum is 110min, and the 3d compressive strength is 31.4MPa.

[0041] From the examples 1 to 15, it can be concluded that the gypsum retarder obtained has a water content of ≤13%, a silicate cement initial setting time of ≥104 min, and a 3d strength of ≥31.4 MPa, which meets the requirements of the relevant standards for cement. The examples of the present application can all be implemented and the purposes of the present application can be achieved, and the present application is not limited to these examples.

Claims

1. A method for producing cement mineralizer using zero-carbon phosphogypsum, characterized in that: The method comprises the following steps: adding water, a precipitant, an interface agent and a carbophilic agent to phosphogypsum, mixing the mixture evenly to obtain slurry, pumping the slurry into a flotation column for flotation, filtering foam discharged from the top of the flotation column to obtain a cement mineralizer, screening the underflow discharged from the bottom of the flotation column to obtain quartz slag and purified gypsum, adding a dehydrating agent to the purified gypsum, mixing the mixture evenly and filtering the mixture to obtain a gypsum retarder; wherein the precipitant is one of calcined raw meal and steel slag powder; the interface agent is one of sodium dodecylsulfonate, triethanolamine soap and cresol acid; the carbophilic agent is one of palmitic acid, oleic acid and diesel; the dehydrating agent is one of polyoxyethylene, aminosulfonic acid and anthracenesulfonic acid formaldehyde; the flotation column comprises an ultrasonic generator, a column, a bubble generator and a foam collecting tank; and the electricity used in the production process is one of photovoltaic power and wind power.

2. The method for producing cement mineralizer from phosphogypsum with zero carbon as claimed in claim 1, characterized in that: The amount of water added is 300-500% of the mass of the phosphogypsum.

3. The method for producing cement mineralizer from phosphogypsum with zero carbon as claimed in claim 1, characterized in that: The amount of the precipitant added is 3-8% of the mass of the phosphogypsum.

4. The method for producing cement mineralizer from phosphogypsum with zero carbon as claimed in claim 1, characterized in that: The amount of the interface agent added is 0.05-0.5% of the mass of the phosphogypsum.

5. The method for producing cement mineralizer from phosphogypsum with zero carbon as claimed in claim 1, characterized in that: The amount of the carbonophilic agent added is 0.05-0.5% of the mass of the phosphogypsum.

6. The method for producing cement mineralizer using zero-carbon phosphogypsum according to claim 1, characterized in that: The amount of the dehydrating agent added is 0.05-0.5% of the mass of the phosphogypsum.

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