Natural gas and coal gas mixing device and gas supply system for belt roaster

Abstract

The application discloses a natural gas and coal gas mixing device and a gas supply system for a belt-type roaster, and belongs to the technical field of gas mixing for belt-type roasters. The natural gas and coal gas mixing device comprises an inner cylinder which is connected in series in a pipeline for conveying converter gas or blast furnace gas, an outer cylinder which is sleeved on the outer periphery of the inner cylinder, a natural gas inlet pipe which is arranged on the outer cylinder, a spraying assembly which is arranged on the cylinder wall of the inner cylinder, and a flow guide vane which is fixed to the inner part of the outlet end of the inner cylinder. An annular cavity is formed between the inner wall of the outer cylinder and the outer wall of the inner cylinder, and the volume of the annular cavity is less than or equal to the flow volume of natural gas per second to form a positive pressure. Natural gas enters the annular cavity through the natural gas inlet pipe, is injected into the inner cylinder through the spraying assembly under the action of the positive pressure, is mixed with converter gas or blast furnace gas, and then forms spiral flow through the flow guide vane. The different pressure and different calorific value gas is fully mixed at one time, so that the calorific value of the mixed gas can be maximally utilized.

Description

Technical Field

[0001] This application belongs to the field of gas mixing technology for belt roasters, and particularly relates to a natural gas and coal gas mixing device and a gas supply system for belt roasters. Background Technology

[0002] The gas fuels used in the pelletizing process of a belt roaster generally include coke oven gas, natural gas, and mixtures of natural gas with converter gas or blast furnace gas. In plants without coke oven gas, natural gas is usually mixed with converter gas or blast furnace gas to reduce fuel costs. In practical engineering applications, the uniformity of the mixed gas directly affects combustion completeness and thermal efficiency. The more uniform the mixture, the more fully the proportion of low-calorific-value gas can be utilized, and the lower the fuel cost.

[0003] However, natural gas differs significantly from converter gas or blast furnace gas in terms of pressure, calorific value, and composition. The uniformity of the mixed gas directly affects combustion completeness and thermal utilization efficiency. Therefore, how to uniformly mix fuels with different pressures, calorific values, and compositions in a single operation has been a long-standing technical challenge that urgently needs to be addressed. Summary of the Invention

[0004] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a natural gas and coal gas mixing device and a gas supply system for a belt roaster, which realizes the one-time thorough mixing of gas with different pressures and calorific values, thereby ensuring that the calorific value of the mixed coal gas is maximized.

[0005] In a first aspect, this application provides a natural gas and coal gas mixing device, which includes: The inner cylinder is connected in series in the pipeline that transports converter gas or blast furnace gas. The outer cylinder is fitted around the outer periphery of the inner cylinder, and the inner wall of the outer cylinder and the outer wall of the inner cylinder form an annular cavity. Natural gas inlet pipe, which is installed on the outer cylinder, is used to introduce natural gas into the annular cavity; An injection assembly, disposed on the inner cylinder wall, is used to inject natural gas from the annular cavity into the inner cylinder; and, The guide fan blades are fixedly installed inside the outlet end of the inner cylinder to make the mixed airflow form a spiral flow. The volume of the annular cavity is configured to be less than or equal to the volume of the incoming natural gas flow rate per second, so as to create positive pressure within the annular cavity.

[0006] According to the natural gas and coal gas mixing device of this application, by configuring the volume of the annular cavity to be less than or equal to the flow rate of natural gas per second, a continuous positive pressure environment is ensured within the annular cavity, allowing natural gas to actively enter the inner cylinder via injection. Natural gas is then injected into the coal gas via an injection assembly, achieving one-time mixing of gases with different pressures, calorific values, and compositions. A guide fan blade creates a spiral flow in the mixed gas stream, further enhancing the mixing effect. The synergistic effect of these three elements ensures thorough mixing of natural gas with converter gas or blast furnace gas, maximizing the calorific value of the mixed gas, improving heat utilization efficiency, and reducing gas usage costs.

[0007] According to one embodiment of this application, the spraying assembly includes multiple rows of spraying units evenly distributed circumferentially and axially along the inner cylinder wall. Each row of spraying units includes multiple spraying units evenly distributed circumferentially along the inner cylinder, and the multiple rows of spraying units are arranged at intervals along the axial direction of the inner cylinder.

[0008] According to one embodiment of this application, at least one of the plurality of spray units in a column has a different spray angle than the other spray units; and / or, At least one of the multiple injection units in a row has a different length than the other injection units.

[0009] According to one embodiment of this application, each column of spraying units includes a plurality of spraying unit groups arranged at uniform intervals along the circumference, and each spraying unit group includes a plurality of spraying units arranged at intervals along the circumference, the spraying directions of the plurality of spraying units being at an angle to each other.

[0010] According to one embodiment of this application, each spray unit group includes three spray units, namely a spray hole, a spray short pipe, and a spray long pipe; the spray direction of the spray hole is perpendicular to the axial direction of the inner cylinder; the spray direction of the spray long pipe forms a 30° angle with the spray direction of the spray hole; and the spray direction of the spray short pipe forms a 60° angle with the spray direction of the spray hole.

[0011] According to one embodiment of this application, each column of spraying units includes two spraying unit groups, which are arranged symmetrically about the axis of the inner cylinder.

[0012] According to one embodiment of this application, the natural gas and coal gas mixing device includes a plurality of natural gas inlet pipes, which are spaced apart and evenly distributed along the circumference of the outer cylinder.

[0013] According to one embodiment of this application, the total flow area of ​​all injection units of the injection assembly is smaller than the total flow area of ​​multiple natural gas inlet pipes.

[0014] According to one embodiment of this application, the inner diameter of the outer cylinder is 200 mm to 400 mm larger than the outer diameter of the inner cylinder.

[0015] Secondly, this application provides a gas supply system for a belt roaster, the gas supply system for the belt roaster including a natural gas and coal gas mixing device as in any embodiment of the first aspect, the natural gas and coal gas mixing device being connected in series in the converter gas or blast furnace gas supply pipeline of the belt roaster, for mixing natural gas with converter gas or blast furnace gas and then supplying it to the burners.

[0016] The beneficial effects of the gas supply system for the belt roaster provided in the second aspect of this application are the same as those of the natural gas and coal gas mixing device provided in the first aspect, and will not be repeated here.

[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0018] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a side view of the natural gas and coal gas mixing device provided in the embodiments of this application; Figure 2 This is an axial view structural schematic diagram of the natural gas and coal gas mixing device provided in the embodiments of this application.

[0019] Figure label: 1. First flange; 2. Inner cylinder; 3. Outer cylinder; 4. Natural gas inlet pipe; 5. Second flange; 6. Guide fan blade; 7. Injection short pipe; 8. Injection long pipe. Detailed Implementation

[0020] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0021] The following is for reference. Figure 1 and Figure 2 This application describes a natural gas and coal gas mixing apparatus according to embodiments thereof.

[0022] Please see Figure 1 and Figure 2This application provides a natural gas and coal gas mixing device, including an inner cylinder 2, an outer cylinder 3, an annular cavity, a natural gas inlet pipe 4, an injection assembly, and guide fan blades 6. The inner cylinder 2 is connected in series in a pipeline transporting converter gas or blast furnace gas. The outer cylinder 3 is fitted around the outer periphery of the inner cylinder 2, and the inner wall of the outer cylinder 3 and the outer wall of the inner cylinder 2 form an annular cavity. The natural gas inlet pipe 4 is disposed on the outer cylinder 3 for introducing natural gas into the annular cavity. The injection assembly is disposed on the cylinder wall of the inner cylinder 2 for injecting the natural gas from the annular cavity into the inner cylinder 2. The guide fan blades 6 are fixedly disposed inside the outlet end of the inner cylinder 2 to create a spiral flow of the mixed gas. The volume of the annular cavity is configured to be less than or equal to the flow rate per second of the introduced natural gas to create positive pressure within the annular cavity.

[0023] The pipeline for transporting converter gas or blast furnace gas is an external network pipeline within the plant area, and its diameter is determined according to the mixed gas load required by the project. The inner cylinder 2 is connected in series within this pipeline, serving as the main flow channel for the mixed gas. The inner cylinder 2 can be cylindrical, and its two ends can be connected to the external network pipeline via the first flange 1 to facilitate the installation, disassembly, and maintenance of the entire unit. The inner diameter of the inner cylinder 2 can be the same as the inner diameter of the external network pipeline to avoid additional pressure loss or eddies during gas transmission.

[0024] The outer cylinder 3 is fitted around the outer periphery of the inner cylinder 2, forming an annular cavity between them. The outer cylinder 3 and the inner cylinder 2 can be coaxially arranged to ensure that the width of the annular cavity is uniform throughout the circumference of the inner cylinder 2, which is beneficial for the uniform distribution of natural gas within the cavity and for maintaining stable pressure. The two ends of the outer cylinder 3 can be sealed to the outer wall of the inner cylinder 2, for example, through welding or flange connections, to prevent natural gas leakage from both ends of the annular cavity. The annular cavity is used to temporarily store the introduced natural gas and its volume configuration creates a positive pressure environment.

[0025] The volume of the annular cavity is configured to be less than or equal to the volumetric flow rate of the introduced natural gas per second. The volumetric flow rate of natural gas per second refers to the volumetric flow rate of natural gas introduced into the annular cavity per unit time under standard operating conditions. By limiting the volume of the annular cavity to less than or equal to this flow rate, the residence time of natural gas within the annular cavity does not exceed one second, thereby creating a continuous positive pressure state within the annular cavity. This positive pressure state serves two purposes: first, it ensures that the pressure of the natural gas within the annular cavity is higher than the pressure of the converter gas or blast furnace gas inside the inner cylinder 2, allowing the natural gas to actively enter the inner cylinder 2 via injection; second, it prevents the backflow of converter gas or blast furnace gas into the annular cavity during pressure fluctuations in the inner cylinder 2, thus preventing eddies or obstruction and ensuring the stability and continuity of the mixing process.

[0026] In some embodiments, the inner diameter of the outer cylinder 3 is 200 mm to 400 mm larger than the outer diameter of the inner cylinder 2. This difference can be selected according to actual engineering needs, for example, 200 mm, 250 mm, 300 mm, 350 mm, or 400 mm. The radial width of the annular cavity is half of this difference. By limiting this size range, the annular cavity has sufficient volume to form a positive pressure environment, while avoiding an excessively large cavity that could lead to insufficient natural gas pressure or delayed response.

[0027] A natural gas inlet pipe 4 is installed on the outer cylinder 3. One end of the natural gas inlet pipe 4 is connected to the annular cavity, and the other end is connected to the natural gas external supply pipeline. The natural gas inlet pipe 4 is used to introduce municipal natural gas into the annular cavity. A control valve may be installed on the natural gas inlet pipe 4 to regulate the flow rate of natural gas. In some embodiments, the natural gas and coal gas mixing device includes multiple natural gas inlet pipes 4, which are spaced apart and evenly distributed along the circumference of the outer cylinder 3. For example, there may be three natural gas inlet pipes 4, which are evenly distributed along the circumference of the outer cylinder 3 at 120° intervals to ensure that natural gas enters the annular cavity simultaneously from multiple circumferential positions, making the pressure and concentration distribution of natural gas in the cavity more uniform. The number of natural gas inlet pipes 4 may also be two, four, or more, and this application does not specifically limit this.

[0028] The injection assembly is mounted on the wall of the inner cylinder 2. It is used to inject natural gas from the annular cavity into the inner cylinder 2. The injection assembly consists of multiple injection channels penetrating the wall of the inner cylinder 2, with one end of each channel opening into the annular cavity and the other end opening into the internal flow channel of the inner cylinder 2. The injection assembly guides the natural gas from the annular cavity into the interior of the inner cylinder 2 and injects it at a certain direction and speed into the converter gas or blast furnace gas flowing through the inner cylinder 2, achieving initial mixing of the two gases.

[0029] The guide vane 6 is fixedly installed inside the outlet end of the inner cylinder 2. The guide vane 6 is located downstream of the injection assembly along the airflow direction. The guide vane 6 is used to create a spiral flow in the mixed airflow. The guide vane 6 may include blades fixed to the inner wall of the inner cylinder 2, with the blades at a certain torsional angle relative to the axis of the inner cylinder 2. When the mixed airflow passes through the guide vane 6, it changes from axial flow to a rotating spiral turbulent state under the guidance of the blades, thereby extending the mixing path and enhancing the mixing effect. The guide vane 6 can be made of a steel plate, with one end fixed to the inner wall of the inner cylinder 2 and the other end twisted at a certain angle relative to the fixed end, such as 90° or 180°. There can be one or more guide vanes 6; when multiple guide vanes 6 are provided, they can be evenly arranged circumferentially along the inner cylinder 2.

[0030] In actual operation, converter gas or blast furnace gas flows in from the inlet end of the inner cylinder 2 and flows forward along the axial direction of the inner cylinder 2. Natural gas enters the annular cavity through the natural gas inlet pipe 4. Since the volume of the annular cavity is configured to be less than or equal to the flow rate of natural gas per second, a positive pressure environment is formed within the annular cavity. Under the action of positive pressure, natural gas is injected into the interior of the inner cylinder 2 from the annular cavity at a certain speed and direction through the injection assembly, contacting and mixing with the flowing converter gas or blast furnace gas. After the injection and mixing are completed, the mixed gas continues to flow forward. When it passes through the guide fan blade 6, it forms a spiral flow under the guidance of the guide fan blade 6, and the mixed gas is further thoroughly mixed during the rotation and forward movement. Finally, the uniformly mixed gas is discharged from the outlet end of the inner cylinder 2 and supplied to the subsequent burners.

[0031] According to the natural gas and coal gas mixing device provided in this application embodiment, by configuring the volume of the annular cavity to be less than or equal to the flow rate of natural gas per second, a continuous positive pressure environment is ensured within the annular cavity, allowing natural gas to actively enter the inner cylinder 2 via injection. Natural gas is then injected into the coal gas via an injection assembly, achieving one-time mixing of gases with different pressures, calorific values, and compositions. The guide fan blades 6 create a spiral flow in the mixed gas stream, further enhancing the mixing effect. The synergistic effect of these three elements ensures thorough mixing of natural gas with converter gas or blast furnace gas, maximizing the calorific value of the mixed gas, improving heat utilization efficiency, and reducing gas usage costs.

[0032] Please see Figure 1 and Figure 2 According to some embodiments of this application, the spraying assembly may include multiple rows of spraying units evenly distributed circumferentially and axially on the inner cylinder 2. Each row of spraying units includes multiple spraying units evenly distributed circumferentially along the inner cylinder 2, and the multiple rows of spraying units are arranged at intervals along the axial direction of the inner cylinder 2.

[0033] Each row of injection units refers to the collection of all injection units arranged along the entire circumference of the inner cylinder 2 at the same axial position. Multiple rows of injection units are arranged at intervals along the axial direction of the inner cylinder 2, with a certain axial spacing between adjacent rows. Each row of injection units can be evenly distributed along the axial direction of the inner cylinder 2, meaning the axial spacing between adjacent rows is equal, to ensure uniform injection volume of natural gas at all positions along the axial direction. Each row of injection units includes multiple injection units evenly distributed along the circumference of the inner cylinder 2, meaning the circumferential angle between adjacent injection units in the same row is equal, to ensure uniform injection volume of natural gas in all directions along the circumference. By arranging the injection units in a uniformly distributed manner both circumferentially and axially on the cylinder wall of the inner cylinder 2, natural gas can be injected simultaneously from all directions and positions within the inner cylinder 2, achieving full and uniform contact between natural gas and coal gas.

[0034] In some embodiments, the injection unit is a channel structure penetrating the wall of the inner cylinder 2. The injection unit can be an injection hole, i.e., a through hole directly formed in the wall of the inner cylinder 2, which has a simple structure and is easy to manufacture. The injection unit can also be a short injection pipe 7, i.e., a short pipe extending a certain length from the wall of the inner cylinder 2 into the interior of the inner cylinder 2, with its injection outlet located inside the inner cylinder 2, which facilitates natural gas entering the mainstream gas flow at a greater depth. The injection unit can also be a long injection pipe 8, i.e., a long pipe extending a considerable distance from the wall of the inner cylinder 2 into the interior of the inner cylinder 2, with its injection outlet closer to the central area of ​​the inner cylinder 2, enabling direct injection of natural gas to the core of the gas flow. Injection units of different lengths and forms can achieve different injection depths, which is beneficial for creating a multi-layered mixing effect.

[0035] In some embodiments, the number of spray units in each row of spray units can be determined according to the diameter of the inner cylinder 2. For example, when the diameter of the inner cylinder 2 is small, six spray units can be set in each row, with an included angle of 60° between two adjacent spray units; when the diameter of the inner cylinder 2 is large, eight, ten or more spray units can be set in each row. The number of rows of spray units along the axial direction of the inner cylinder 2 can also be determined according to the length of the inner cylinder 2, for example, three, four, five or more rows can be set. The axial spacing between two adjacent rows can be determined according to specific design requirements to ensure a continuous and uniform spray coverage in the axial direction.

[0036] Please see Figure 1 and Figure 2 According to some embodiments of this application, at least one of the multiple spray units in a row may have a different spray angle than the other spray units; and / or, at least one of the multiple spray units in a row may have a different length than the other spray units.

[0037] In some embodiments, the angle between the injection direction of each injection unit and the axial direction of the inner cylinder 2 can be different within the same row of injection units. For example, the injection direction of some injection units can be perpendicular to the axial direction of the inner cylinder 2, i.e., injected radially along the inner cylinder 2, so that natural gas is injected radially into the gas flow; the injection direction of some injection units can be inclined towards the downstream direction of the inner cylinder 2, i.e., at an acute angle to the axial direction of the inner cylinder 2, so that natural gas is injected obliquely forward into the gas flow, forming a co-current mixing with the gas flow; the injection direction of some injection units can be at an angle to the radial direction of the inner cylinder 2. By setting injection units with different injection angles in the circumferential direction, natural gas can be injected into the inner cylinder 2 from different directions, forming multi-angle cross-mixing with the gas flow, which is beneficial to improving the mixing uniformity.

[0038] In some embodiments, within the same row of injection units, the lengths by which each injection unit extends radially into the inner cylinder 2 can vary. For example, some injection units can be injection orifices with their outlets flush with the inner wall of the inner cylinder 2, allowing natural gas to enter the inner cylinder 2 from the inner wall surface; some injection units can be short injection pipes 7 with their outlets extending a certain distance into the inner cylinder 2, allowing natural gas to enter the inner cylinder 2 from the near-wall region; and some injection units can be long injection pipes 8 with their outlets extending to near the center region of the inner cylinder 2, allowing natural gas to enter the inner cylinder 2 from the core region. By setting injection units of different lengths, natural gas can be injected simultaneously from different radial depths in the gas flow, ensuring that natural gas is distributed in the surface, middle, and core layers of the gas flow, effectively preventing natural gas from being concentrated in only a localized area, thereby improving the mixing effect.

[0039] In some implementations, a single column of spray units can contain multiple spray units with different spray angles and lengths. That is, the angles and lengths of some spray units are different from those of other spray units, creating differentiated spraying in both angle and length dimensions, further enhancing the mixing effect.

[0040] Please see Figure 1 and Figure 2 According to some embodiments of this application, each column of spray units may include a plurality of spray unit groups arranged at uniform intervals along the circumference, and each spray unit group includes a plurality of spray units arranged at intervals along the circumference, the spraying directions of the plurality of spray units being at an angle to each other.

[0041] Each injection unit group comprises multiple injection units, which are distributed circumferentially along the inner cylinder 2, with a certain circumferential distance between adjacent injection units. Each injection unit within the same group has a different injection direction, and these directions are at angles to each other; that is, no two injection units have the same injection direction, and there is an angular difference between each injection direction. By combining multiple injection units with different injection directions into an injection unit group, natural gas within that group can be simultaneously injected into the inner cylinder 2 from multiple different angles, achieving multi-angle cross-injection.

[0042] Each row of injection units may include multiple injection unit groups, which are evenly spaced along the circumference of the inner cylinder 2. The circumferential angle between any two adjacent injection unit groups is equal. For example, when each row of injection units includes two injection unit groups, the two injection unit groups are arranged 180° apart circumferentially, i.e., axially symmetrical about the axis of the inner cylinder 2. When each row of injection units includes three injection unit groups, the three injection unit groups are arranged 120° apart circumferentially. When each row of injection units includes four injection unit groups, the four injection unit groups are arranged 90° apart circumferentially. By evenly arranging multiple injection unit groups circumferentially, the inner cylinder 2 has multi-angle injection capability in all directions around the circumference, ensuring the uniform distribution of natural gas in all circumferential positions.

[0043] Please see Figure 1 and Figure 2 According to some embodiments of this application, each spray unit group may include three spray units, which may be a spray orifice, a short spray pipe 7, and a long spray pipe 8, respectively. The spray direction of the spray orifice is perpendicular to the axial direction of the inner cylinder 2. The spray direction of the long spray pipe 8 forms a 30° angle with the spray direction of the spray orifice. The spray direction of the short spray pipe 7 forms a 60° angle with the spray direction of the spray orifice.

[0044] The injection hole is a through hole opened on the wall of the inner cylinder 2, and its outlet is flush with the inner wall surface of the inner cylinder 2. The axis of the injection hole is perpendicular to the axis of the inner cylinder 2, that is, the injection hole is set along the radial direction of the inner cylinder 2, and natural gas is injected into the interior of the inner cylinder 2 in the radial direction when it is ejected from the injection hole.

[0045] The long injection pipe 8 is a pipe that penetrates from the wall of the inner cylinder 2 into the interior of the inner cylinder 2, and its length extending into the interior of the inner cylinder 2 is greater than the length of the short injection pipe 7. The injection direction of the long injection pipe 8 forms a 30° angle with the injection direction of the injection hole, that is, the long injection pipe 8 is deflected by 30° relative to the radial direction of the inner cylinder 2.

[0046] In some embodiments, the outlet end of the injection tube 8 can be deflected toward the downstream direction of the inner cylinder 2, so that the natural gas is injected obliquely forward.

[0047] The injection short pipe 7 is a pipe that penetrates from the wall of the inner cylinder 2 into the interior of the inner cylinder 2. Its length extending into the inner cylinder 2 is less than the length of the injection long pipe 8, but greater than the length of the injection orifice. The injection direction of the injection short pipe 7 forms a 60° angle with the injection direction of the injection orifice, meaning the injection short pipe 7 is deflected 60° relative to the radial direction of the inner cylinder 2. In some embodiments, the outlet end of the injection short pipe 7 can be deflected downstream of the inner cylinder 2, with a deflection angle greater than that of the injection long pipe 8.

[0048] Injection orifices, short injection pipes 7, and long injection pipes 8 are arranged circumferentially at intervals within the injection unit group. The injection directions of the three injection units are different, injecting natural gas into the inner cylinder 2 from radial, small-angle inclined, and large-angle inclined directions, respectively. Simultaneously, the lengths of the three injection units extending into the inner cylinder 2 are also different, achieving injection depths at near-wall, middle layer, and center, respectively. Through this dual differentiation design of angle and length, each injection unit group can achieve three-dimensional injection coverage in a local area, significantly improving the mixing efficiency of natural gas and coal gas. Furthermore, this gradient angle design causes the natural gas to advance in a spiral shape after entering the inner cylinder 2, further enhancing the mixing efficiency.

[0049] Please see Figure 1 and Figure 2 According to some embodiments of this application, each column of spraying units may include two spraying unit groups, which are arranged symmetrically about the axis of the inner cylinder 2.

[0050] Each injection unit consists of two injection unit groups, located at the same axial position within the inner cylinder 2 and spaced 180° apart circumferentially. The two injection unit groups are axially symmetrical about the axis of the inner cylinder 2, meaning their radial positions within the inner cylinder 2 are symmetrical about the axis. This arrangement ensures that the jet flow field created by the two injection unit groups inside the inner cylinder 2 is symmetrical about the axis, which is beneficial for forming a uniform natural gas distribution across the cross-section of the inner cylinder 2 and avoids flow deviation or localized uneven concentration.

[0051] The injection units in the two injection unit groups are staggered circumferentially to create a more uniform injection coverage. For example, the injection holes in the first injection unit group and the second injection unit group are circumferentially opposite each other, meaning the line connecting the centers of the two injection holes passes through the central axis of the inner cylinder 2. Similarly, the short injection pipes 7 in the two injection unit groups are opposite each other, as are the long injection pipes 8. Through this axisymmetric arrangement, the natural gas injection flow field inside the inner cylinder 2 exhibits good symmetry and uniformity.

[0052] Please see Figure 1 and Figure 2 According to some embodiments of this application, the natural gas and coal gas mixing device may include a plurality of natural gas inlet pipes 4, which are spaced apart and evenly distributed along the circumference of the outer cylinder 3.

[0053] Three natural gas inlet pipes 4 can be installed, arranged at 120° intervals along the circumference of the outer cylinder 3. All three natural gas inlet pipes 4 connect to the annular cavity between the outer cylinder 3 and the inner cylinder 2. Natural gas enters the annular cavity simultaneously from the three inlet pipes 4, forming three inlet points circumferentially. Because the three inlet points are evenly distributed along the circumference of the outer cylinder 3, the natural gas can rapidly diffuse and evenly distribute itself circumferentially after entering the annular cavity, which is beneficial for balancing the pressure and concentration of natural gas within the annular cavity.

[0054] In some embodiments, the number of natural gas inlet pipes 4 may be two, arranged 180° apart circumferentially; or four, arranged 90° apart circumferentially. The specific number of natural gas inlet pipes 4 can be determined according to the volume of the annular cavity and the flow rate requirement of natural gas, and this application does not impose a specific limitation on this.

[0055] In some embodiments, each natural gas inlet pipe 4 may extend radially along the outer cylinder 3. A second flange 5 may be provided at the end of the natural gas inlet pipe 4 extending beyond the outer wall of the outer cylinder 3 for connection to the external natural gas supply pipeline, facilitating disassembly and maintenance of the device. The length of each natural gas inlet pipe 4 extending beyond the outer wall of the outer cylinder 3 can be determined according to the engineering installation space; for example, it may extend 300mm to 500mm to allow space for flange installation and connection.

[0056] Please see Figure 1 and Figure 2 According to some embodiments of this application, the total flow area of ​​all injection units of the injection assembly can be less than the total flow area of ​​the plurality of natural gas inlet pipes 4.

[0057] The total flow area of ​​all injection units in the injection assembly refers to the sum of the flow areas of all injection units. The flow area of ​​each injection unit refers to the minimum cross-sectional area of ​​its internal channel; for the injection orifice, it is its orifice diameter area; for the injection short pipe 7 and injection long pipe 8, it is its inner pipe cross-sectional area. The total flow area of ​​the multiple natural gas inlet pipes 4 refers to the sum of the flow areas of all natural gas inlet pipes 4, and the flow area of ​​each natural gas inlet pipe 4 is the cross-sectional area of ​​its internal channel.

[0058] The total flow area of ​​all injection units in the injection assembly is designed to be smaller than the total flow area of ​​the multiple natural gas inlet pipes 4. This ensures that the total inlet area of ​​natural gas entering the annular cavity from the natural gas inlet pipes 4 is greater than the total outlet area of ​​the annular cavity from the injection units. According to the principle of fluid continuity, with a constant flow rate, a decrease in flow area leads to an increase in flow velocity, creating an accumulation effect within the annular cavity, which helps maintain a positive pressure state within the annular cavity. This area constraint, combined with the configuration of the annular cavity volume, ensures that the annular cavity is always under positive pressure, allowing natural gas to enter the inner cylinder 2 via injection and preventing backflow of gas.

[0059] Please see Figure 1 and Figure 2 According to some embodiments of this application, the inner diameter of the outer cylinder 3 is 200 mm to 400 mm larger than the outer diameter of the inner cylinder 2.

[0060] In some embodiments, the difference between the inner diameter of the outer cylinder 3 and the outer diameter of the inner cylinder 2 ranges from 200 mm to 400 mm. This difference can be selected based on the actual engineering conditions and natural gas flow rate. When the natural gas flow rate is high, a larger difference can be selected to increase the volume of the annular cavity, ensuring sufficient natural gas reserves within the cavity to maintain positive pressure. When the natural gas flow rate is low, a smaller difference can be selected to reduce the cavity volume, making the match between the cavity volume and the natural gas flow rate per second more precise.

[0061] The difference between the inner diameter of the outer cylinder 3 and the outer diameter of the inner cylinder 2 can be 200mm, 250mm, 300mm, 350mm, or 400mm. Within this range, the annular cavity has a suitable radial width, which ensures that the annular cavity has sufficient volume to form a positive pressure environment, while preventing the natural gas from forming a stagnant or dead zone near the inner wall due to excessive cavity width, thus facilitating the flow and renewal of natural gas.

[0062] Please see Figure 1 and Figure 2In some embodiments, the overall length of the device is 1700mm, including two short-connecting pipes at both ends and the main body of the device in the middle. The main body is 1500mm long and consists of an inner cylinder 2, an outer cylinder 3, and an annular cavity between them. Each end has a 100mm long short-connecting pipe with the same inner diameter as the inner cylinder 2 and connected to the internal flow channel of the inner cylinder 2. The ends of the short-connecting pipes are equipped with flanges for connection to the external converter gas or blast furnace gas supply pipeline flanges. Through the flanges on the short-connecting pipes at both ends, the entire device can be connected as a single independent unit to the external pipeline network, facilitating installation, disassembly, and maintenance. In other embodiments, the overall length, the length of the main body, and the length of the short-connecting pipes at both ends can be adaptively adjusted according to the diameter of the inner cylinder 2 and the engineering installation space. For example, the overall length can be 1500mm~2000mm, the length of the main body can be 1300mm~1800mm, and the length of the short-connecting pipes can be 80mm~150mm.

[0063] Please see Figure 1 and Figure 2 Based on the same concept, this application also provides a gas supply system for a belt roaster, including a natural gas and coal gas mixing device as described above. The natural gas and coal gas mixing device is connected in series in the converter gas or blast furnace gas supply pipeline of the belt roaster, and is used to mix natural gas with converter gas or blast furnace gas and then supply it to the burner.

[0064] The belt calciner is a core piece of equipment in the pellet production process, and its burners require a mixture of coal gas with a certain calorific value as fuel. The gas supply system includes a converter gas or blast furnace gas supply pipeline, and a natural gas and coal gas mixing device connected in series within this pipeline. Converter gas or blast furnace gas is transported from the plant's pipeline network to the mixing device, while natural gas is simultaneously introduced. After mixing in the mixing device, the mixed coal gas is discharged from the outlet of the mixing device and transported via pipeline to the individual burners of the belt calciner.

[0065] The inner cylinder 2 of the mixing device is connected to the converter gas or blast furnace gas supply pipeline at both ends via flanges. The natural gas inlet pipe 4 of the mixing device is connected to the external natural gas network pipeline via flanges. The entire mixing device is an independent equipment unit in the gas supply system, which is convenient for installation, disassembly and maintenance.

[0066] The gas supply system of the belt roaster may also include flow regulating valves, pressure measuring instruments and temperature measuring instruments installed upstream and downstream of the mixing device, for real-time monitoring and adjustment of gas flow and pressure parameters to ensure that the mixing device operates under rated conditions.

[0067] The gas supply system for a belt calciner provided in this application embodiment, by employing the aforementioned natural gas and coal gas mixing device, can fully and uniformly mix natural gas with converter gas or blast furnace gas, which have significant differences in pressure, calorific value, and composition. This ensures that the mixed coal gas supplied to the burners has a uniform composition and calorific value, which is beneficial to the stable combustion of the burners and the improvement of heat utilization efficiency, thereby reducing the gas usage cost of the belt calciner pelletizing process.

[0068] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0069] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0070] In the description of this application, "first feature" and "second feature" may include one or more of the features.

[0071] In the description of this application, "multiple" means two or more.

[0072] In the description of this application, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or the first and second features being in contact through another feature between them.

[0073] In the description of this application, the terms "above," "over," and "on top" for the first feature and the second feature include the first feature being directly above or diagonally above the second feature, or simply indicate that the first feature is at a higher horizontal level than the second feature.

[0074] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above 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 one or more embodiments or examples.

[0075] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A device for mixing natural gas and coal gas, characterized in that, include: The inner cylinder is connected in series in a pipeline for conveying converter gas or blast furnace gas; An outer cylinder is fitted around the outer periphery of the inner cylinder, and an annular cavity is formed between the inner wall of the outer cylinder and the outer wall of the inner cylinder. A natural gas inlet pipe is provided on the outer cylinder and is used to introduce natural gas into the annular cavity; An injection assembly is disposed on the cylinder wall of the inner cylinder and is used to inject natural gas from the annular cavity into the inner cylinder; as well as, The guide fan blade is fixedly installed inside the outlet end of the inner cylinder to make the mixed airflow form a spiral flow. The volume of the annular cavity is configured to be less than or equal to the flow rate of the introduced natural gas per second, so as to create positive pressure within the annular cavity.

2. The natural gas and coal gas mixing device according to claim 1, characterized in that, The spraying assembly includes multiple rows of spraying units evenly distributed circumferentially and axially on the inner cylinder wall. Each row of spraying units includes multiple spraying units evenly distributed circumferentially along the inner cylinder, and the multiple rows of spraying units are arranged at intervals along the axial direction of the inner cylinder.

3. The natural gas and coal gas mixing device according to claim 2, characterized in that, At least one of the plurality of spray units in a row has a different spray angle than the other spray units; And / or, At least one of the plurality of injection units in a column has a different length than the other injection units.

4. The natural gas and coal gas mixing device according to claim 2, characterized in that, Each column of the spraying unit includes multiple spraying unit groups arranged at uniform intervals along the circumference, and each spraying unit group includes multiple spraying units arranged at intervals along the circumference, with the spraying directions of the multiple spraying units forming an angle with each other.

5. The natural gas and coal gas mixing device according to claim 4, characterized in that, Each of the spray unit groups includes three spray units, namely a spray orifice, a short spray tube, and a long spray tube; the spray direction of the spray orifice is perpendicular to the axial direction of the inner cylinder; the spray direction of the long spray tube forms a 30° angle with the spray direction of the spray orifice; and the spray direction of the short spray tube forms a 60° angle with the spray direction of the spray orifice.

6. The natural gas and coal gas mixing device according to claim 4, characterized in that, Each column of the spraying unit includes two spraying unit groups, which are arranged symmetrically about the axis of the inner cylinder.

7. The natural gas and coal gas mixing apparatus according to any one of claims 1-6, characterized in that, The natural gas and coal gas mixing device includes multiple natural gas inlet pipes, which are spaced apart and evenly distributed along the circumference of the outer cylinder.

8. The natural gas and coal gas mixing device according to claim 7, characterized in that, The total flow area of ​​all injection units in the injection assembly is less than the total flow area of ​​the multiple natural gas inlet pipes.

9. The natural gas and coal gas mixing apparatus according to any one of claims 1-6, characterized in that, The inner diameter of the outer cylinder is 200mm to 400mm larger than the outer diameter of the inner cylinder.

10. A gas supply system for a belt roaster, characterized in that, The device includes a natural gas and coal gas mixing device as described in any one of claims 1 to 9, wherein the natural gas and coal gas mixing device is connected in series in the converter gas or blast furnace gas supply pipeline of the belt roaster, and is used to mix natural gas with converter gas or blast furnace gas and then supply it to the burner.

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