A method for stabilizing a reducing slag includes the steps of: subjecting a reducing slag which contains an alkaline earth metal oxide to a drying treatment, so as to obtain a dried reducing slag; mixing a urease-producing bacterium, a fermentation medium, and a nutrient, followed by conducting a fermentation treatment, so as to obtain a fermentation product containing urease; subjecting the fermentation product to a foam fractionation treatment, so as to obtain a foam containing urease; mixing the dried reducing slag, the foam containing urease, and urea, followed by conducting a urea hydrolysis reaction and a precipitation reaction in sequence, so as to obtain a product containing a stabilized reducing slag and a residual liquid; and subjecting the product to a solid-liquid separation treatment, so as to separate the stabilized reducing slag and the residual liquid from the product.
Legal claims defining the scope of protection, as filed with the USPTO.
. A method for stabilizing a reducing slag, comprising the steps of:
. The method as claimed in, wherein in step (b), the urease-producing bacterium is an aerobic bacterium selected from the group consisting of, and a combination thereof.
. The method as claimed in, wherein in step (b), the urease-producing bacterium is an anaerobic bacterium selected from the group consisting of, and combinations thereof.
. The method as claimed in, wherein in step (c), the foam fractionation treatment is conducted by introducing a gas into the fermentation product containing urease, so as to generate the foam containing urease.
. The method as claimed in, wherein the gas is air.
. The method as claimed in, wherein in step (a), the reducing slag is subjected to a sterilization treatment before or simultaneously with the drying treatment, the sterilization treatment being conducted using ultraviolet light.
. The method as claimed in, wherein in step (a), the dried reducing slag is further subjected to a sterilization treatment after the drying treatment, the sterilization treatment being conducted using ultraviolet light.
. The method as claimed in, wherein in step (a), the drying treatment is conducted using sunlight.
. The method as claimed in, wherein in step (b), the fermentation treatment is conducted at a temperature ranging from 15° C. to 40° C. for a time period ranging from 16 hours to 120 hours.
. The method as claimed in, wherein in step (c), the foam fractionation treatment is conducted at a temperature ranging from 15° C. to 40° C.
. The method as claimed in, wherein in step (d), the urea hydrolysis reaction and the precipitation reaction are conducted at a temperature ranging from 15° C. to 40° C.
Complete technical specification and implementation details from the patent document.
This application claims priority to Taiwanese Invention Patent Application No. 113111694, filed on Mar. 28, 2024, the entire disclosure of which is incorporated by reference herein.
The present disclosure relates to a method for disposing a waste, and more particularly to a method for stabilizing a reducing slag.
With an increased demand for steel products, an amount of a steel slag generated in a steelmaking process is also increased. However, due to a poor stability of the steel slag, a recycling efficiency of the steel slag is low, resulting in a large amount of the steel slag being discarded as waste, thus causing harm to the environment and giving rise to environmental protection issues. Therefore, enhancing the stability of the steel slag to increase recycling value thereof is an urgent issue that needs to be addressed.
CN 113860779 A discloses a method for pretreating a steel slag using a microorganism, which includes the following steps: (a) inoculatinginto a sterilized culture medium at a controlled pH value ranging from 6 to 8, followed by cultivating in a constant-temperature shaking incubator for a time period ranging from 12 hours to 24 hours, so as to obtain a bacterial solution with a total bacterial concentration ranging from 10cells/mL to 10cells/mL; (b) adding urea into the bacterial solution, followed by uniformly stirring and then cultivating in the constant-temperature shaking incubator for a time period ranging from 0.5 hours to 1.0 hour, so as to obtain a liquid culture; and (c) immersing a steel slag in the liquid culture for a time period ranging from 12 hours to 72 hours.
Although a stabilized steel slag can be obtained by the method of CN 113860779 A, the content of carbonate ions in the liquid culture formed in step (b) is low due to the low concentration of urease in the bacterial solution obtained in step (a), and hence in step (c), the steel slag is required to be immersed in the liquid culture for a relatively long period of time (at least 12 hours) to obtain the stabilized steel slag that meets usage standards.
In view of the aforesaid, there is still a need to develop an effective way for stabilizing a reducing slag in a relatively short period of time.
Therefore, an object of the present disclosure is to provide a method for stabilizing a reducing slag, which can alleviate at least one of the drawbacks of the prior art.
According to the present disclosure, the method includes the steps of:
For the purpose of this specification, it will be clearly understood that the word “comprising” means “including but not limited to”, and that the word “comprises” has a corresponding meaning.
It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Taiwan or any other country.
Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by a person skilled in the art to which the present disclosure belongs. One skilled in the art will recognize many methods and materials similar or equivalent to those described herein, which could be used in the practice of the present disclosure. Indeed, the present disclosure is in no way limited to the methods and materials described.
The present disclosure provides a method for stabilizing a reducing slag, which includes the following steps (a) to (e).
In step (a), a reducing slag which contains an alkaline earth metal oxide is subjected to a drying treatment, so as to obtain a dried reducing slag. The alkaline earth metal oxide is selected from the group consisting of calcium oxide, magnesium oxide, and a combination thereof.
In step (b), a urease-producing bacterium, a fermentation medium, and a nutrient are mixed, followed by conducting a fermentation treatment, so as to obtain a fermentation product containing urease.
In step (c), the fermentation product containing urease obtained in step (b) is subjected to a foam fractionation treatment, so as to obtain a foam containing urease. A concentration of the urease in the foam is greater than a concentration of the urease in the fermentation product.
In step (d), the dried reducing slag obtained in step (a), the foam containing urease obtained in step (c), and urea are mixed, followed by conducting a urea hydrolysis reaction and a precipitation reaction in sequence, so as to obtain a product containing a stabilized reducing slag and a residual liquid.
In step (e), the product obtained in step (d) is subjected to a solid-liquid separation treatment, so as to separate the stabilized reducing slag and the residual liquid from the product.
<Step (a)>
Examples of the reducing slag may include, but are not limited to, a blast furnace slag, a basic oxygen furnace slag, and an electric arc furnace slag. In certain embodiments, the reducing slag includes silicon dioxide (SiO) in an amount ranging from 22 wt % to 29 wt %, calcium oxide (CaO) in an amount ranging from 48 wt % to 50 wt %, magnesium oxide (MgO) in an amount ranging from 6 wt % to 10 wt %, aluminum oxide (AlO) in an amount ranging from 14 wt % to 18 wt %, and ferric oxide (FeO) in an amount ranging from 1 wt % to 2 wt %.
According to the present disclosure, the drying treatment is conducted using sunlight to heat the reducing slag, thereby removing moisture from the reducing slag. During the drying treatment, the reducing slag is stirred using a mixing machine so as to accelerate progression of the drying treatment. In certain embodiments, by virtue of the drying treatment, the moisture content in the reducing slag is reduced to not greater than 10%. In certain embodiments, the drying treatment is conducted at a temperature ranging from 15° C. to 40° C.
In certain embodiments, in step (a), the reducing slag is subjected to a sterilization treatment before or simultaneously with the drying treatment. In certain embodiments, in step (a), the dried reducing slag is further subjected to a sterilization treatment after the drying treatment. A sequence of the drying treatment and the sterilization treatment is not limited. In an exemplary embodiment, the drying treatment is conducted first, followed by conducting the sterilization treatment.
In certain embodiments, the sterilization treatment is conducted at a temperature ranging from 15° C. to 40° C. In certain embodiments, the sterilization treatment is conducted using ultraviolet light to irradiate the reducing slag or the dried reducing slag. During the sterilization treatment, the reducing slag or the dried reducing slag is tumbled using a mixing machine with a conveyor belt and a roller shovel so as to accelerate progression of the sterilization treatment.
<Step (b)>
In certain embodiments, the urease-producing bacterium is an aerobic bacterium. Examples of the aerobic bacterium may include, but are not limited to,, and a combination thereof. In an exemplary embodiment,is deposited at the Bioresource Collection and Research Center (BCRC) of the Food Industry Research and Development Institute (FIRDI) (No. 331, Shih-Pin Rd., Hsinchu City 300, Taiwan) under an accession number BCRC 11596, and is also deposited at the American Type Culture Collection (ATCC) (10801 University Boulevard, Manassas, Va. 20110-2209., USA) in accordance with the Budapest Treaty under an accession number ATCC 11859, andis deposited at the BCRC of the FIRDI under an accession number BCRC 16048, and is also deposited at the ATCC in accordance with the Budapest Treaty under an accession number ATCC 21332. Both strains are known and readily available to the public.
In certain embodiments, the urease-producing bacterium is an anaerobic bacterium. Examples of the anaerobic bacterium may include, but are not limited to,, and combinations thereof. In an exemplary embodiment, the anaerobic bacterium is selected from the group consisting ofGKM3 which is deposited at the BCRC of the FIRDI under an accession number BCRC 910787, and is also deposited at the ATCC in accordance with the Budapest Treaty under an accession number ATCC 14917,GKG6 which is deposited at the BCRC of the FIRDI under an accession number 81178, and is also deposited at the ATCC in accordance with the Budapest Treaty under an accession number ATCC 7469,GKF3 which is deposited at the BCRC of the FIRDI under an accession number BCRC 910824, and combinations thereof. These strains are known and readily available to the public.
According to the present disclosure, the types and components of the fermentation medium may vary based on the urease-producing bacterium to be used. Examples of the fermentation medium may include, but are not limited to, M9 minimal medium, lysogeny broth, Tris-buffered basal medium containing yeast extract, sodium bicarbonate basal medium, and phosphate-buffered basal medium. In certain embodiments, the fermentation medium includes a nitrogen source and a carbon source. Examples of the nitrogen source may include, but are not limited to, tryptone and yeast paste. Examples of the carbon source may include, but are not limited to, glucose and glycerol. In certain embodiments, the fermentation medium further includes an inorganic salt. An example of the inorganic salt may include, but is not limited to, sodium chloride.
According to the present disclosure, the types of the nutrient may vary based on the urease-producing bacterium to be used. Examples of the nutrient may include, but are not limited to, a carbon source, a nitrogen source, and an inorganic salt. Examples of the carbon source may include, but are not limited to, glucose, glycerol, and muscovado sugar. Examples of the nitrogen source may include, but are not limited to, tryptone, yeast paste, and ammonium sulfide. An example of the inorganic salt may include, but is not limited to, sodium chloride.
According to the present disclosure, the procedures and conditions of the fermentation treatment are within the expertise and routine skills of those skilled in the art.
According to the present disclosure, the fermentation treatment is conducted at a temperature ranging from 15° C. to 40° C. for a time period ranging from 16 hours to 120 hours. In certain embodiments, the fermentation treatment is conducted at a pH value ranging from 5 to 9. In certain embodiments, the fermentation treatment is conducted at an aeration rate ranging from 0.15 vvm to 1.00 vvm (volume of sparged air to volume of culture medium per minute). In certain embodiments, the fermentation treatment includes a first fermentation process and a second fermentation process. In the first fermentation process, a mixture, which is formed by mixing the urease-producing bacterium, the fermentation medium, and the nutrient, is subjected to the fermentation treatment until an optical density (OD) of the mixture is measured to be not less than 1.0. Thereafter, in the second fermentation process, the mixture continues to be subjected to the fermentation treatment for a certain time period so as to produce a surfactant, such that the thus obtained fermentation product further contains the surfactant in addition to the urease. The surfactant is capable of facilitating foam formation during the foam fractionation treatment in step (c), thereby enabling the foam to carry the urease and assisting in the execution of step (d). Examples of the surfactant may include, but are not limited to, a protein-based surfactant and a peptide-based surfactant. In certain embodiments, the first fermentation process is conducted at a temperature ranging from 15° C. to 40° C. for a time period ranging from 16 hours to 48 hours. In certain embodiments, the second fermentation process is conducted at a temperature ranging from 15° C. to 40° C. for a time period of 72 hours.
<Step (c)>
In certain embodiments, the foam fractionation treatment is conducted by means of a foam fractionation column. The foam at different vertical heights within the foam fractionation column has a different concentration of the urease. In other words, as the vertical height increases, the concentration of the urease in the foam formed from the fermentation product also increases, so that the foam with different concentration gradient of urease is fractionated. Therefore, a length of the foam fractionation column affects a degree of urease enrichment in the foam. According to the present disclosure, in step (c), the foam fractionation treatment is conducted by introducing a gas into the fermentation product containing urease, so as to generate the foam containing urease. In certain embodiments, a flow rate of the gas ranges from 0.1 L/min to 1.0 L/min. Different gas flow rates result in different foam sizes which are categorized based on a magnitude of the gas flow rate to obtain the foams with different degrees of moisture content, thereby facilitating obtainment of the foams with different concentrations of the urease. An example of the gas may include, but is not limited to, air. In certain embodiments, the foam fractionation treatment is conducted at a temperature ranging from 15° C. to 40° C. for a time period ranging from 2 hours to 5 hours. In certain embodiments, the gas is introduced into the fermentation product containing the urease using an air disperser with multiple pores. A size of the pores may be adjusted according to a required size of an air bubble. Examples of the air disperser may include, but are not limited to, a sintered glass sparger, and a sintered metal sparger.
<Step (d)>
By virtue of conducting the urea hydrolysis reaction, the urease in the foam hydrolyzes the urea to produce carbonate ions which subsequently undergoes the precipitation reaction with the alkaline earth metal oxide in the dried or sterilized reducing slag, resulting in a formation of a carbonate salt precipitate, thereby converting the dried or sterilized reducing slag into the stabilized reducing slag. In certain embodiments, the urea hydrolysis reaction and the precipitation reaction are conducted at a temperature ranging from 15° C. to 40° C.
The stabilized reducing slag can be used as an aggregate in concrete. In addition, the stabilized reducing slag has a low content of the alkaline earth metal oxide, and hence does not exhibit expansion when in contact with water, which prevents serious damage such as cracking or crumbling of a cured material formed by the concrete, thereby achieving a goal of recycling the reducing slag for resource utilization.
<Step (e)>
The solid-liquid separation treatment is not particularly limited and can be conducted using any conventional solid-liquid separation technique well known to those skilled in the art. Examples of the solid-liquid separation treatment may include, but are not limited to, a sedimentation separation treatment and a filtration separation treatment.
The disclosure will be further described by way of the following examples. However, it should be understood that the following examples are solely intended for the purpose of illustration and should not be construed as limiting the disclosure in practice.
A method for stabilizing a reducing slag of EX1 includes the following steps (a) to (e).
<Step (a)>
An electric arc furnace slag (serving as a reducing slag, ingredient: 25 wt % of SiO, 49 wt % of CaO, 8 wt % of MgO, 17 wt % of AlO, and 1 wt % of FeO) was introduced into a mixing machine, and was subjected to a stirring treatment and a drying treatment using sunlight at a temperature of 30° C. for a time period ranging from 12 hours to 48 hours so as to reduce an amount of moisture in the electric arc furnace slag to 10%, thereby obtaining a dried reducing slag. Thereafter, the dried reducing slag was introduced into a mixing machine with a roller shovel, and was subjected to a sterilization treatment using ultraviolet light at a temperature of 30° C., so as to obtain a sterilized reducing slag.
<Step (b)>
1000 L of a fermentation medium (ingredient: 20 g/L of tryptone, 5 g/L of sodium chloride, and 20 g/L of urea), 10 g of a nutritional composition (ingredient: 20 g/L of glucose, 20 g/L of muscovado sugar, and 20 g/L of tryptone), and(serving as a urease-producing bacterium, obtained as a commercial product BCRC 11596 from the Bioresource Collection and Research Center (BCRC) of the Food Industry Research and Development Institute (FIRDI)) were mixed, so as to form a mixture. Thereafter, the mixture was subjected to a fermentation treatment at a temperature of 30° C. for 24 hours to achieve an optical density (OD) value of 1.0, followed by continuously subjecting the mixture to the fermentation treatment at a temperature of 30° C. for 72 hours, so as to obtain a fermentation product containing 0.006 wt % of urease.
<Step (c)>
The fermentation product containing 0.006 wt % of the urease obtained in step (b) was subjected to a foam fractionation treatment by introducing air at a flow rate of 0.5 L/min into the fermentation product at a temperature of 30° C. for a time period of 3 hours, so as to obtain a foam containing 0.5 wt % of urease.
<Step (d)>
100 g of the sterilized reducing slag obtained in step (a), 60 mL of the foam containing 0.5 wt % of the urease obtained in step (c), and 12.02 g of urea were mixed, followed by conducting a urea hydrolysis reaction and a precipitation reaction in sequence at a temperature of 30° C. for a total time period of 6 hours, so as to obtain a product containing a stabilized reducing slag and a residual liquid.
<Step (e)>
The product obtained in step (d) was subjected to a solid-liquid separation treatment by gravity settling to separate the stabilized reducing slag and the residual liquid from the product, such that the stabilized reducing slag was located at the bottom and the residual liquid was located at the top.
The procedures and conditions in a method for stabilizing a reducing slag of the respective one of EX2 and EX3 were similar to those of EX1, except that the total time periods of the urea hydrolysis reaction and the precipitation reaction in step (d) were varied as shown in Table 1 below. In addition, in step (b), the OD value of the mixture determined in each of the methods of EX2 and EX3 was 1.0±0.2.
A method for stabilizing a reducing slag of EX4 included a first treatment of steps (a) to (e), a second treatment of steps (a′), (d′), and (e′), and a third treatment of steps (a″), (d″), and (e″) as follows.
Unknown
October 2, 2025
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