Process for resource utilization of high-concentration wastewater using steelmaking slag treatment process

Abstract

The present invention relates to a process for resource utilization of high-concentration wastewater in a steelmaking slag treatment process, and specifically comprises the following steps: S1, first, after treatment in a hot and stuffy slag pool is completed, the high-concentration wastewater is injected into the slag pool, and the treated slag aggregate is used to adsorb suspended matter such as organic matter and heavy metals in the wastewater; S2, after the addition of the high-concentration wastewater is completed, most of the free water in the slag is waited to enter the circulating water system, and the slag is waited to be dried and put into use; the present invention utilizes fluoride ions in the high-concentration wastewater to react with the circulating water in the slag treatment process, thereby reducing the concentration of calcium and magnesium ions in the circulating water, which is conducive to the recycling of the slag circulating water; the high-concentration wastewater is resource utilized, the organic matter in the high-concentration wastewater is decomposed, and the decomposed organic matter is used to reduce the high-valent iron oxide in the steel slag, which can increase the amount of iron-containing substances recovered by magnetic separation of the steel slag.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-concentration wastewater treatment in steel enterprises, and specifically relates to a process for resource utilization of high-concentration wastewater by utilizing steelmaking slag treatment procedures. Background Art

[0002] Steel companies use a large amount of water in many production processes, including coking, sintering, ironmaking, steelmaking, and steel rolling. Wastewater discharged during steel production comes from production process water, equipment and product cooling wastewater, equipment and site flushing water, etc. 70% of wastewater comes from cooling water, and wastewater discharged from the production process accounts for a small part. The main pollutants in steel company wastewater include inorganic suspended solids, organic oxygen-demanding substances, chemical toxic substances, heavy metals, acids and alkalis, and thermal pollution. Steel companies face great pressure to recycle, treat, and reuse all factory wastewater and truly achieve "zero discharge" of industrial wastewater. In particular, the resource utilization of high-concentration wastewater (also called high-concentration brine or concentrated wastewater) generated by the centralized wastewater treatment system of steel companies is an industry-wide problem.

[0003] The composition of concentrated brine from the centralized sewage treatment plant of Xinjiang Bayi Iron and Steel Co., Ltd. is shown in the following table:

[0004] After consulting the literature, it was found that the technical staff of Meigang Chuming published a paper entitled "Analysis of Comprehensive Wastewater Treatment in Steel Enterprises" in the fourth issue of "Meigang Science and Technology" magazine in 2013. The paper stated that "comprehensive wastewater mainly refers to two forms of wastewater in steel enterprises: one is the mixed wastewater formed by the total drainage system of steel enterprises collecting production wastewater, rainwater and even domestic sewage from multiple processes in the enterprise in a combined system; the other is that in some steel enterprises with relatively complete circulating water treatment systems and facilities, there are still sporadic wastewater that cannot be solved by the circulation systems of each unit and wastewater that must be discharged from each unit. They must be centrally treated to improve the water circulation rate." In the sixth issue of "Metallurgy and Materials" magazine in 2019, a paper entitled "Environmental Impact Assessment Study on the Use of Wuhan Iron and Steel Coking Comprehensive Wastewater for Blast Furnace Slag Water Quenching" was published. "In view of the fact that Wuhan Iron and Steel Corporation uses water from the Yangtze River to quench blast furnace slag, which consumes a lot of water and has high costs, in order to improve the water quenching effect of blast furnace slag and enhance the quality of blast furnace slag, the effects of using treated coking wastewater for blast furnace slag quenching on blast furnace slag and the surrounding atmosphere were studied on the basis of coagulation, precipitation and oxidation of coking wastewater. The results show that after 5 cycles of water quenching with the treated coking comprehensive wastewater, the cyanide concentration in the cooling water is stable at around 0.006 mg / L, the volatile phenol concentration is stable at around 0.002 mg / L, and the sulfide concentration is stable at around 0.011 mg / L. The concentrations of cyanide, volatile phenol and sulfide in the evaporated water vapor after water quenching are stable at around 0.001 mg / L within a range of 1m."

[0005] From the above literature description, it can be seen that there is currently no process for resource utilization of high-concentration wastewater in the steelmaking slag treatment process. Summary of the Invention

[0006] The purpose of the present invention is to provide a process for resource utilization of high-concentration wastewater by using steelmaking slag treatment process, thereby solving the problems existing in the prior art.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] The process of utilizing high-concentration wastewater from the steelmaking slag treatment process as a resource includes the following steps:

[0009] S1. First, after the treatment in a hot slag pool is completed, high-concentration wastewater is injected into the slag pool, and the treated steel slag aggregate is used to absorb suspended matter such as organic matter and heavy metals in the wastewater;

[0010] S2. After the addition of high-concentration wastewater is completed, wait until most of the free water in the slag enters the circulating water system, and wait for the steel slag to dry before use;

[0011] S3. Add the dried slag to a slag tank filled with liquid slag and let it stand for about 30 minutes. Pour the hot slag in the slag tank into the slag pool to decompose organic matter with the hot slag and reduce heavy metal compounds in the slag.

[0012] S4. Repeat the above operations, and continuously add the steel slag that absorbs high-concentration sewage into the slag tank filled with liquid steel slag. After standing for 30 minutes, pour it into the slag pool. After the slag pool is full, stand for 60 minutes, and then treat it according to the conventional slag treatment process. The tailings can be utilized according to the normal resource utilization process.

[0013] Preferably, the slag temperature after the hot slag pool treatment in S1 is controlled at 100-200°C.

[0014] Preferably, the amount of high-concentration wastewater added to S1 is 300-500 kg per ton of steel slag.

[0015] Preferably, the amount of dried steel slag added in S3 is 100-250 kg per ton of liquid steel slag.

[0016] Preferably, the steel slag aggregate in S1 is a porous alkaline substance with strong alkalinity. The steel slag aggregate contains the following components: metallic iron, calcium oxide, magnesium oxide and manganese oxide, which can react with oil in sewage to form grease salts, which exist in the steel slag aggregate.

[0017] Preferably, steel slag can adsorb organic matter and heavy metals in sewage, and the chloride ions in sewage can react with f-MgO in steel slag aggregate to form magnesium chloride, which further reacts with f-MgO in steel slag to form a precursor of magnesia cement, thereby improving the gelling properties of steel slag.

[0018] Preferably, the specific steps of adsorbing organic matter and heavy metals in sewage by steel slag are as follows:

[0019] T1. Add steel slag to liquid steel slag and use the C and H generated by the cracking of oil and organic matter at around 960℃ to reduce the high-valent heavy metal oxides in the steel slag. The main reactions are:

[0020] CxHyCOOCnHm+Q→(x+n)C+(y+m)H+H2O

[0021] C + CuO = Cu + CO

[0022] FeO+C=Fe+CO

[0023] Fe2O3+3C=2Fe+3CO

[0024] The metals and metal oxides in the slag are recovered through screening and magnetic separation processes during the magnetic separation process, and are reused as iron-containing raw materials in the steelmaking or ironmaking process.

[0025] T2. Ammonia nitrogen compounds entering the slag treatment circulating water undergo decomposition reactions under alkaline and high-temperature conditions to generate nitrogen and water, achieving harmless transformation;

[0026] T3. The F- ions entering the slag circulating water react with the Ca2+ and Mg2+ ions in the water to form insoluble fluorides, thus achieving harmless transformation of hazardous substances. The main chemical reactions are as follows:

[0027] 2F-+Ca2+=CaF2

[0028] 2F-+Mg2=MgF2;

[0029] T4. Some harmful substances that do not participate in the chemical reaction eventually enter the steel slag. Since steel slag is an overburned silicate cement clinker, it forms hydration products after the steel slag is recycled. Harmful substances exist in the hydration products. The mineralization and storage of harmful substances (As, Cd, etc.) achieve the purpose of harmlessness.

[0030] The beneficial effects of the present invention are as follows: the present invention utilizes fluoride ions in high-concentration sewage to react with circulating water in the steel slag treatment process, thereby reducing the concentration of calcium and magnesium ions in the circulating water, which is beneficial to the recycling of the steel slag circulating water; the present invention utilizes high-concentration sewage as a resource, decomposes organic matter in the high-concentration sewage, and utilizes the decomposed organic matter to reduce high-valent iron oxide in the steel slag, which can increase the amount of iron-containing substances recovered by magnetic separation of the steel slag; the present invention reduces water consumption in the steel slag treatment process, and reduces the treatment cost of high-concentration sewage. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] The present invention is a process for resource utilization of high-concentration wastewater in the steelmaking slag treatment process, which specifically includes the following steps:

[0033] S1. After treatment in a hot slag tank, high-concentration wastewater is injected into the tank. The treated slag aggregate absorbs suspended solids such as organic matter and heavy metals in the wastewater. The slag temperature after treatment in the hot slag tank is controlled at 100-200°C. The amount of high-concentration wastewater added is 300-500 kg per ton of steel slag. Steel slag aggregate is a porous alkaline substance with a strong alkalinity. It contains metallic iron, calcium oxide, magnesium oxide, and manganese oxide. It reacts with oil in the wastewater to form grease salts, which are present in the slag aggregate.

[0034] S2. After the addition of high-concentration sewage, wait until most of the free water in the slag enters the circulating water system, and wait for the steel slag to dry before use; steel slag can adsorb organic matter and heavy metals in sewage, and the chloride ions in sewage can react with f-MgO in steel slag aggregate to form magnesium chloride, which further reacts with f-MgO in steel slag to form a precursor of magnesia cement, which can improve the cementitious properties of steel slag.

[0035] S3. Add the dried steel slag into a slag pot filled with liquid steel slag, let it stand for about 30 minutes, and pour the high-temperature steel slag in the slag pot into the slag pool. Use the hot steel slag to decompose organic matter and reduce heavy metal compounds in the steel slag. The amount of dried steel slag added in S3 is 100-250 kg per ton of liquid steel slag.

[0036] S4. Repeat the above operations, and continuously add the steel slag that absorbs high-concentration sewage into the slag tank filled with liquid steel slag. After standing for 30 minutes, pour it into the slag pool. After the slag pool is full, stand for 60 minutes, and then treat it according to the conventional slag treatment process. The tailings can be utilized according to the normal resource utilization process.

[0037] The specific steps of steel slag adsorbing organic matter and heavy metals in wastewater are as follows:

[0038] T1. Add steel slag to liquid steel slag and use the C and H generated by the cracking of oil and organic matter at around 960℃ to reduce the high-valent heavy metal oxides in the steel slag. The main reactions are:

[0039] CxHyCOOCnHm+Q→(x+n)C+(y+m)H+H2O

[0040] C + CuO = Cu + CO

[0041] FeO+C=Fe+CO

[0042] Fe2O3+3C=2Fe+3CO

[0043] The metals and metal oxides in the slag are recovered through screening and magnetic separation processes during the magnetic separation process, and are reused as iron-containing raw materials in the steelmaking or ironmaking process.

[0044] T2. Ammonia nitrogen compounds entering the slag treatment circulating water undergo decomposition reactions under alkaline and high-temperature conditions to generate nitrogen and water, achieving harmless transformation;

[0045] T3. The F- ions entering the slag circulating water react with the Ca2+ and Mg2+ ions in the water to form insoluble fluorides, thus achieving harmless transformation of hazardous substances. The main chemical reactions are as follows:

[0046] 2F-+Ca2+=CaF2

[0047] 2F-+Mg2=MgF2;

[0048] T4. Some harmful substances that do not participate in the chemical reaction eventually enter the steel slag. Since steel slag is an overburned silicate cement clinker, it forms hydration products after the steel slag is recycled. Harmful substances exist in the hydration products. The mineralization and storage of harmful substances (As, Cd, etc.) achieve the purpose of harmlessness.

[0049] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0050] The above content is merely an example and explanation of the concept of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A process for recycling high-concentration wastewater from a steelmaking slag treatment process, characterized in that: The specific steps include: S1. First, after the treatment in a hot and stuffy slag pool is completed, high-concentration wastewater is injected into the slag pool, and the treated steel slag aggregate is used to absorb organic matter and heavy metal suspended matter in the wastewater; S2. After the addition of high-concentration wastewater is completed, wait until most of the free water in the slag enters the circulating water system, and wait for the steel slag to dry before use; S3. Add the dried slag to a slag tank filled with liquid slag and let it stand for 30 minutes. Pour the hot slag in the slag tank into the slag pool to decompose organic matter with the hot slag and reduce heavy metal compounds in the slag. S4. Repeat the above operation, continuously add the steel slag that absorbs high-concentration sewage into the slag tank filled with liquid steel slag, let it stand for 30 minutes, then pour it into the slag pool. After the slag pool is full, let it stand for 60 minutes, and then treat it according to the conventional slag treatment process. The tailings are utilized according to the normal resource utilization process. Steel slag can absorb organic matter and heavy metals in sewage. Chloride ions in sewage can react with f-MgO in steel slag aggregate to form magnesium chloride, which further reacts with f-MgO in steel slag to form a precursor of magnesia cement, which can improve the cementitious properties of steel slag. The specific steps of steel slag adsorbing organic matter and heavy metals in wastewater are as follows: T1. Add steel slag to liquid steel slag and use the C and H generated by the cracking of oil and organic matter at 960℃ to reduce the high-valent heavy metal oxides in the steel slag. The main reactions are: CxHyCOOCnHm+Q→(x+n)C+(y+m)H+H2O C + CuO = Cu + CO FeO+C=Fe+CO Fe2O3+3C=2Fe+3CO The metals and metal oxides in the slag are recovered through screening and magnetic separation processes during the magnetic separation process, and are reused as iron-containing raw materials in the steelmaking or ironmaking process. T2. Ammonia nitrogen compounds entering the slag treatment circulating water undergo decomposition reactions under alkaline and high-temperature conditions to generate nitrogen and water, achieving harmless transformation; T3, F entering the slag circulating water - ions, and Ca in water 2+ Mg 2+ The ions react to form insoluble fluorides, achieving harmless transformation of hazardous substances. The main chemical reactions are as follows: 2F - +Ca 2+ =CaF2 2F - +Mg 2+ =MgF 2 ; T4. Some harmful substances that do not participate in the chemical reaction eventually enter the steel slag. Since steel slag is an overburned silicate cement clinker, it forms hydration products after the steel slag is recycled. Harmful substances exist in the hydration products. The mineralization and sealing of harmful substances achieve the purpose of harmlessness.

2. The process for recycling high-concentration wastewater from a steelmaking slag treatment process according to claim 1, characterized in that: The slag temperature after the hot slag pool treatment in S1 is controlled at 100-200°C.

3. The process for recycling high-concentration wastewater from a steelmaking slag treatment process according to claim 1, characterized in that: The amount of high-concentration wastewater added to S1 is 300-500 kg per ton of steel slag.

4. The process for recycling high-concentration wastewater using steelmaking slag treatment process according to claim 1 is characterized in that: The amount of dried steel slag added in S3 is 100 to 250 kg per ton of liquid steel slag.

5. The process for recycling high-concentration wastewater from a steelmaking slag treatment process according to claim 1 is characterized in that: The steel slag aggregate in S1 is a porous alkaline substance with strong alkalinity. The components contained in the steel slag aggregate include metallic iron, calcium oxide, magnesium oxide and manganese oxide, which can react with the oil in the sewage to form grease acid salts, which exist in the steel slag aggregate.

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