A basic pellet and a method for producing the same

Abstract

The application provides a kind of basic pellet, utilize carbon-containing dust of iron and steel industry and solid waste phosphogypsum of phosphorus chemical industry as raw material, the method for producing basic pellet, the method comprises the following steps: phosphogypsum, carbon-containing dust and iron concentrate are mixed according to certain proportion, and a certain amount of bentonite is used as balling raw material after being matched outside.A large amount of carbon in carbon-containing dust of iron and steel industry is ingeniously utilized, calcium sulfate in phosphogypsum is reduced and decomposed into calcium oxide to improve the basicity of pellet, and a large amount of iron component in carbon-containing dust can also be used as balling raw material, which will not significantly reduce the low grade of pellet.The calcium, iron component and carbon in phosphogypsum and carbon-containing dust are reasonably utilized and increased in value, and waste is turned into treasure, which not only can large-scale absorb carbon-containing dust and phosphogypsum, but also reduces the production cost of basic pellet.

Description

Technical Field

[0001] This invention relates to the field of basic pellets for blast furnaces, and more specifically, to a basic pellet and its preparation method. Background Technology

[0002] Phosphogypsum is a by-product solid waste of the phosphate chemical industry. In the wet-process phosphoric acid production, 5 tons of phosphogypsum are generated for every ton of phosphoric acid produced. However, due to the high impurity content in phosphate rock, some impurities react with sulfuric acid during wet-process phosphoric acid production to form precipitates that mix with the phosphogypsum. This reduces the purity of calcium sulfate and increases the content of harmful elements, making the phosphogypsum difficult to utilize. my country currently has approximately 600 million tons of phosphogypsum stockpiled, while the annual usage is very limited. The indiscriminate dumping of large quantities of acidic phosphogypsum not only occupies land and pollutes the environment but also wastes a significant amount of resources.

[0003] In various processes of steel production, carbonaceous dust such as blast furnace ash, sintering coke, and dust collector ash are generated. In addition to carbon components, these carbonaceous dusts also contain a large amount of iron components and are generally used for return to the sintering batch. However, excessive use of carbonaceous dust will reduce the permeability of the sintering bed and worsen the sintering performance.

[0004] Calcium sulfate requires 1300℃ to decompose into calcium oxide and sulfur dioxide under an oxidizing atmosphere. However, this temperature is far above the pelletizing sintering temperature, making it impossible to achieve the oxidative decomposition of calcium sulfate at the roasting temperature of the pelletizing process. This invention cleverly utilizes the reducing property of carbon in carbon-containing dust to significantly reduce the decomposition temperature of calcium sulfate from 1300℃ to 800℃. The resulting calcium oxide can increase the basicity of the pellets, producing alkaline pellets.

[0005] Alkaline pellets are high-quality ironmaking raw materials developed to meet the new requirements for refined feedstocks in blast furnaces. Compared to traditional sintered ore, pellets have uniform particle size, high iron content, and good reducibility, making them an excellent blast furnace feedstock.

[0006] In summary, using a blend of phosphogypsum, carbonaceous dust, and iron concentrate as raw materials for alkaline pellet production not only allows for the added value and harmless utilization of phosphogypsum and carbonaceous dust, but also allows the sulfur in the phosphogypsum to decompose into sulfur dioxide during high-temperature combustion, which can then be returned to the sulfuric acid production process via a desulfurization system. Simultaneously, utilizing the calcium in the neutralization slag increases the basicity of the pellets, reducing the production cost of alkaline pellets. Summary of the Invention

[0007] This invention provides an alkaline pellet and its preparation method to solve the problem that calcium sulfate requires 1300℃ to decompose in an oxidizing atmosphere to produce calcium oxide and sulfur dioxide, but this temperature is far higher than the pellet sintering temperature, and the oxidative decomposition of calcium sulfate cannot be achieved at the calcination temperature of the pelleting process.

[0008] According to one aspect of the present invention, an alkaline pellet is provided, wherein the components and weight percentage content of the alkaline pellet are 10-15% phosphogypsum, 10-20% carbonaceous dust, 70-90% iron concentrate, and 1.0-2.5% bentonite.

[0009] Based on the above scheme, the preferred option is that the calcium sulfate content in the phosphogypsum is 70-90%.

[0010] Based on the above scheme, the preferred option is that the carbon content in the carbon-containing dust is 10-30% and the iron grade is 40-60%.

[0011] Based on the above scheme, the preferred option is that the iron concentrate includes magnetite and hematite, and its iron grade is 60-68%.

[0012] The present invention also provides a processing method for preparing the alkaline pellets, comprising the following steps: Step A1: Prepare raw materials of phosphogypsum, carbonaceous dust and iron concentrate in proportion and perform high-pressure roller milling. Step A2: Prepare bentonite from the raw material processed in step A1 and pelletize it on a pelletizing machine to form a spherical structure; Step A3: The pellets are sieved to obtain green pellets with a particle size of 8-16 mm, and then dried, preheated, calcined and cooled to obtain alkaline pellets.

[0013] Based on the above scheme, the preferred option is step A2, after preparing the bentonite, the alkalinity of the raw material is above 0.6 and the iron content is above 58%.

[0014] Based on the above scheme, in step A3, the drying is divided into two stages, with the first stage drying temperature being 120-200℃ and the time being 3-10 minutes, and the second stage drying temperature being 200-400℃ and the time being 5-10 minutes.

[0015] Based on the above scheme, in step A3, during the preheating process, the first preheating temperature is 500-600℃ and the time is 5-10 minutes, and the second preheating temperature is 900-1000℃ and the time is 10-15 minutes; during the roasting process, the roasting temperature is 1200℃ and the time is 25-40 minutes.

[0016] This invention discloses an alkaline pelletizing process and its preparation method. By using phosphogypsum, carbon dust, and iron concentrate as raw materials, and preparing bentonite, a large amount of phosphogypsum can be consumed, reducing mineral waste. Furthermore, the reducing properties of carbon in the large amount of carbon-containing dust from the steel industry are utilized to reduce and decompose the calcium sulfate in the phosphogypsum into calcium oxide, thereby increasing the alkalinity of the pellets. Simultaneously, the large amount of iron contained in the carbon dust can also be used as a pelletizing raw material without significantly reducing the grade of the pellets. This invention rationally and valuablely utilizes the carbon, calcium, and iron components in phosphogypsum and carbon dust, turning waste into treasure. It not only enables large-scale disposal of carbon dust and phosphogypsum but also reduces the production cost of alkaline pellets. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a flowchart of the preparation method of the alkaline pellets of the present invention. Detailed Implementation

[0018] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0019] It should be understood that, when used in this specification and the appended claims, the term "comprising" indicates the presence of a descriptive feature, integral, step, operation, element, and / or component, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or sets.

[0020] To keep the drawings concise, only the parts relevant to the invention are shown schematically in each figure, and they do not represent the actual structure of the product. Furthermore, for ease of understanding, in some figures, only one of components with the same structure or function is shown schematically, or only one is labeled. In this document, "one" can mean not only "only one" but also "more than one".

[0021] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0022] In the embodiments shown in the accompanying drawings, the directional indications (such as up, down, left, right, front, and back) used to explain the structure and movement of the various components of the invention are relative rather than absolute. These descriptions are appropriate when these components are in the positions shown in the drawings. If the descriptions of the positions of these components change, these directional indications also change accordingly.

[0023] Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0025] Please see Figure 1 The present invention discloses an alkaline pellet, wherein the alkaline pellet comprises, by weight percentage, 10-15% phosphogypsum, 10-20% carbon-containing dust, 70-90% iron concentrate, and 1.0-2.5% bentonite. The phosphogypsum contains 70-90% calcium sulfate, the carbon-containing dust contains 10-30% carbon and has an iron grade of 40-60%, and the iron concentrate includes magnetite and hematite, with an iron grade of 60-68%.

[0026] The present invention also provides a processing method for preparing the alkaline pellets, comprising the following steps: Step A1: Prepare the raw materials of phosphogypsum, carbonaceous dust and iron concentrate in the above proportions, and then perform high-pressure roller milling. Step A2: Prepare bentonite from the raw material processed in step A1 and pelletize it on a pelletizing machine to form a spherical structure; Step A3: The pellets are sieved to obtain green pellets with a particle size of 8-16 mm, and then dried, preheated, calcined and cooled to obtain alkaline pellets.

[0027] In step A2, after preparing the bentonite, the alkalinity of the raw material is above 0.6 and the iron content is above 58%. In step A3, the drying is divided into two stages. The first stage drying temperature is 120-200℃ and the time is 3-10 minutes. The second stage drying temperature is 200-400℃ and the time is 5-10 minutes.

[0028] In step A3, during the preheating process, the first preheating temperature is 500-600℃ and the time is 5-10 minutes, and the second preheating temperature is 900-1000℃ and the time is 10-15 minutes; during the roasting process, the roasting temperature is 1200℃ and the time is 25-40 minutes.

[0029] This invention discloses an alkaline pelletizing process and its preparation method. By using phosphogypsum, carbon dust, and iron concentrate as raw materials, and preparing bentonite, a large amount of phosphogypsum can be consumed, reducing mineral waste. Furthermore, the reducing properties of carbon in the large amount of carbon-containing dust from the steel industry are utilized to reduce and decompose the calcium sulfate in the phosphogypsum into calcium oxide, thereby increasing the alkalinity of the pellets. Simultaneously, the large amount of iron contained in the carbon dust can also be used as a pelletizing raw material without significantly reducing the grade of the pellets. This invention rationally and valuablely utilizes the carbon, calcium, and iron components in phosphogypsum and carbon dust, turning waste into treasure. It not only enables large-scale disposal of carbon dust and phosphogypsum but also reduces the production cost of alkaline pellets.

[0030] Example 1 The specific process for producing alkaline pellets by reducing and decomposing phosphogypsum using carbon-containing dust as described in this embodiment includes the following steps: Using wet-process phosphate phosphogypsum from Yichang, Hubei Province, blast furnace dust, and iron concentrate as pelletizing raw materials, the raw materials were mixed in the specified proportions, pretreated by high-pressure roller mill, and then bentonite was added before entering the pelletizing process. The green pellets were screened, with 8-16mm particles selected as qualified green pellets. These green pellets were then fed onto a chain grate machine for drying and preheating, followed by calcination in a rotary kiln. After sufficient oxidation and consolidation, the pellets were cooled in an annular cooler to finally obtain the finished pellet ore.

[0031] Specifically, the composition of the pelletizing raw materials is as follows: 10% phosphogypsum, of which the calcium sulfate content is 87%; 12% blast furnace ash, of which the carbon content is 15% and the iron grade is 55%; 78% iron concentrate, whose main component is Fe3O4, the iron grade is 67%, and the silica content is 2.9%. The binder is bentonite, with a dosage of 1.6%.

[0032] In the above scheme, the first stage drying temperature is 150℃ and the time is 4 minutes; the second stage drying temperature is 350℃ and the time is 5 minutes; the first stage preheating temperature is 550℃ and the time is 8 minutes; the second stage preheating temperature is 900℃ and the time is 7 minutes; and the calcination temperature is 1220℃ and the time is 25 minutes.

[0033] After the roasted pellets enter the annular cooler, the pellet temperature in the first stage of the annular cooler is 800-850℃, the pellet temperature in the second stage of the annular cooler is 400-450℃, and the pellet temperature in the third stage of the annular cooler is 100-150℃. After the finished pellets are discharged from the discharge port of the annular cooler, they enter the finished pellet conveyor belt and are sent to the ore bin.

[0034] Using the above raw material ratio and process parameters, qualified alkaline pellets can be produced. The final finished pellets have an iron content of 58.75%, a compressive strength of over 2500N, and a binary basicity of 1.2. All indicators of the finished pellets are qualified.

[0035] Example 2 The specific process for producing alkaline pellets by reducing and decomposing phosphogypsum using carbon-containing dust as described in this embodiment includes the following steps: Using wet-process phosphate phosphogypsum from Yichang, Hubei Province, sintering dust, and iron concentrate as pelletizing raw materials, the raw materials were mixed in the specified proportions, pretreated by a high-pressure roller mill, and then bentonite was added before entering the pelletizing process. The green pellets were screened, with 8-16mm particles selected as qualified green pellets. These green pellets were then fed onto a chain grate machine for drying and preheating, followed by calcination in a rotary kiln. After sufficient oxidation and consolidation, the pellets were cooled in an annular cooler to finally obtain the finished pellet ore.

[0036] The composition of the above pelletizing raw materials is as follows: 8% phosphogypsum, of which the calcium sulfate content is 85%; 10% sintering dust, of which the carbon content is 13% and the iron grade is 58%; 82% iron concentrate, the main component of which is Fe3O4, the iron grade is 66%, and the silicon dioxide content is 3.5%. The binder is bentonite, with a dosage of 1.8%.

[0037] In the above scheme, the first stage drying temperature is 160℃ and the time is 3 minutes; the second stage drying temperature is 350℃ and the time is 7 minutes; the first stage preheating temperature is 580℃ and the time is 10 minutes; the second stage preheating temperature is 900℃ and the time is 6 minutes; and the calcination temperature is 1200℃ and the time is 20 minutes.

[0038] After the roasted pellets enter the annular cooler, the pellet temperature in the first stage of the annular cooler is 800-850℃, the pellet temperature in the second stage of the annular cooler is 400-450℃, and the pellet temperature in the third stage of the annular cooler is 100-150℃. After the finished pellets are discharged from the discharge port of the annular cooler, they enter the finished pellet conveyor belt and are sent to the ore bin.

[0039] Using the above raw material ratio and process parameters, qualified alkaline pellets can be produced. The final finished pellets have an iron content of 59.90%, a compressive strength of over 2500N, and a binary basicity of 0.7. All indicators of the finished pellets are qualified.

[0040] Finally, the method described in this application is merely a preferred embodiment and is not intended to limit the scope of protection of this invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. An alkaline pellet, characterized in that, The alkaline pellets are composed of 10-15% phosphogypsum, 10-20% carbon-containing dust, 70-90% iron concentrate, and 1.0-2.5% bentonite, with the sum of the weight percentages of the phosphogypsum, carbon-containing dust, iron concentrate, and bentonite being 100%. During roasting, the calcium sulfate in the phosphogypsum is reduced and decomposed into calcium oxide by the carbon in the carbon-containing dust, thereby increasing the basicity of the pellets. The iron component in the carbon-containing dust is used as a pelletizing raw material and enters the pellets. The carbon content in the carbon-containing dust is 10-30%, and the iron grade is 40-60%.

2. The alkaline pellet as described in claim 1, characterized in that, The calcium sulfate content in the phosphogypsum is 70-90%.

3. The alkaline pellet as described in claim 1, characterized in that, The iron concentrate includes magnetite and hematite, and its iron grade is 60-68%.

4. A processing method for preparing the alkaline pellets of claim 1, characterized in that, Includes the following steps, Step A1: Prepare the raw materials of phosphogypsum, carbon-containing dust and iron concentrate according to the proportions of claim 1, and perform high-pressure roller milling. Step A2: Prepare bentonite from the raw material processed in step A1 and pelletize it on a pelletizing machine to form a spherical structure; Step A3 involves sieving the pellets to obtain green pellets with a particle size of 8-16 mm, followed by drying, preheating, calcining, and cooling to obtain alkaline pellets. During the calcination process, the carbon in the carbon-containing dust reduces and decomposes the calcium sulfate in the phosphogypsum into calcium oxide.

5. The processing method as described in claim 4, characterized in that, Step A2: After preparing the bentonite, the alkalinity of the raw material is above 0.6 and the iron content is above 58%.

6. The processing method as described in claim 4, characterized in that, In step A3, the drying process is divided into two stages. The first stage of drying is carried out at a temperature of 120-200℃ for 3-10 minutes, and the second stage of drying is carried out at a temperature of 200-400℃ for 5-10 minutes.

7. The processing method as described in claim 4, characterized in that, In step A3, during the preheating process, the first preheating temperature is 500-600℃ and the time is 5-10 minutes, and the second preheating temperature is 900-1000℃ and the time is 10-15 minutes; during the roasting process, the roasting temperature is 1200℃ and the time is 25-40 minutes.

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