A built-in vortex combustion device and a combustion system for treating RDF in a cement decomposition furnace

Abstract

The present invention discloses a built-in vortex combustion device and a combustion system for treating RDF in a cement decomposition furnace, comprising a first cylinder and a second cylinder, wherein the second cylinder is connected above the first cylinder and communicated with the first cylinder; the second cylinder adopts a cylindrical structure with a volute, and a plurality of tertiary air inlets are evenly distributed at the rotary tangent line of the volute; a plurality of RDF feeding inlets are arranged on the top surface of the second cylinder; a preheated raw material feeding inlet is arranged on the top surface of the second cylinder outside the tertiary air inlet. The present invention can realize that RDF is in a suspended state in the vortex combustion device, and the combustion speed is much faster than that of accumulated combustion. The vortex combustion device is arranged as a built-in structure, and there is no need to introduce tertiary air separately.

Description

Technical Field

[0001] The invention relates to the field of cement production and alternative fuel application, and in particular to a built-in vortex combustion device and a combustion system for treating RDF in a cement decomposition furnace. Background Art

[0002] At present, the use of refuse-derived fuel (RDF) as an alternative fuel for cement decomposition furnaces is becoming more and more widespread. More and more cement plants have begun to use RDF as a fuel for cement decomposition furnaces, partially or completely replacing traditional fossil fuel coal. Based on cost factors, RDF is generally made from urban domestic waste after simple pre-treatment such as sorting and crushing. It has a high moisture content, large fluctuations in calorific value and ash content, and low quality. Using it as an alternative fuel for cement decomposition furnaces has a greater impact on the stable operation of the firing system and the production and quality of clinker, resulting in a generally low fuel substitution rate.

[0003] The existing devices for burning alternative fuel RDF in cement calciners mainly include FLSmidth's HOTDISC hot plate furnace, ThyssenKrupp's PREPOL-SC step furnace, KHD's Compared with cement decomposition furnaces, they are all external, and the following problems are common in the use of external pre-combustion devices: (1) RDF is mainly in a piled state in the pre-combustion device, and the combustion speed is slow, which affects the RDF disposal volume; (2) A separate tertiary air flow needs to be introduced, which affects the air control and operating stability of the cement clinker burning system; (3) The ash produced after combustion enters the decomposition furnace in a discontinuous or stranded manner, which can easily cause fluctuations in the operating conditions of the system; (4) The device has a complex structure, is heavy and occupies a large space, and the system is complex and expensive. Summary of the invention

[0004] Purpose of the invention: The first purpose of the present invention is to provide a built-in vortex combustion device that can fully disperse RDF and effectively increase the amount of RDF handled without the need to introduce tertiary air separately; the second purpose of the present invention is to provide a cement decomposition furnace combustion system for handling RDF with a simple structure and without the need for an external pre-combustion device.

[0005] Technical solution: The built-in vortex combustion device of the present invention includes a first cylinder and a second cylinder, the second cylinder is connected to the top of the first cylinder and communicated with the first cylinder; the second cylinder adopts a cylindrical structure with a volute, and a plurality of tertiary air inlets are evenly distributed on the rotary cutting line of the volute; a plurality of RDF feeding inlets are arranged on the top surface of the second cylinder; a preheated raw material feeding inlet is arranged on the top surface of the second cylinder at a position outside the tertiary air inlet.

[0006] A plurality of pulverized coal burners are evenly arranged on the top surface of the second cylinder and the outer wall of the first cylinder.

[0007] The preheated raw material feeding inlet adopts a square structure and is inclined outward. The preheated raw material feeding inlet is connected to the tertiary air inlet. The preheated raw material feeding inlet is inclined to facilitate feeding and material dispersion. After the preheated cement raw material enters the vortex combustion device, it rotates with the tertiary air to be protected by the wall.

[0008] The tertiary air inlet is in a rectangular structure, which is conducive to the formation of swirl flow by the tertiary air.

[0009] The outer shells of the first cylinder and the second cylinder are made of steel plates, and the inner linings are made of fire-resistant insulation materials.

[0010] The first cylinder is configured as a conical structure, and a first constriction is configured at the bottom of the first cylinder for connecting to the smoke chamber.

[0011] A second constriction is arranged on the top surface of the second cylinder body for connecting to a cement decomposition furnace.

[0012] The present invention also includes a combustion system for treating RDF in a cement decomposition furnace, including a built-in vortex combustion device. The system also includes a cement kiln tail smoke chamber and a decomposition furnace. The built-in vortex combustion device is arranged between the cement kiln tail smoke chamber and the decomposition furnace. The vortex combustion device adopts a built-in structure and does not need to introduce tertiary air separately.

[0013] Beneficial effects: Compared with the prior art, the present invention has the following beneficial effects: (1) RDF is in a suspended state in the vortex combustion device, and the combustion speed is much faster than that of accumulated combustion; (2) The RDF combustion area in the vortex combustion device has a high temperature, strong turbulent pulsation, high oxygen content, and large space, and RDF has a suitable residence time, which is beneficial to the gas-solid heat and mass transfer process and enhances the rapid ignition and combustion of RDF; the RDF after preliminary combustion and the generated ash are fully dispersed by the high-speed airflow, and are continuously and evenly brought into the cement decomposition furnace, which greatly increases the disposal amount and application range of RDF; with the help of coal powder combustion regulation, the RDF combustion in the decomposition furnace is realized. The heat replacement rate of the raw material is ≥50%; (3) The vortex combustion device is located between the smoke chamber and the decomposition furnace. It is a built-in structure and does not need to introduce tertiary air separately. It is easy to control the balance between the kiln and the tertiary air of the cement burning system, which is beneficial to the operation of the system and the stability of the clinker production and quality; (4) After the preheated cement raw material enters the vortex combustion device, it is protected by the wall with the rotation of the tertiary air, while preventing the raw material from entering the combustion area too early. The higher temperature in the center of the combustion device can be controlled, which is beneficial to the enhancement of RDF combustion; (5) The built-in vortex combustion device is light in weight and does not require additional installation and operation space. It is simple to arrange and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of the built-in vortex combustion device of the present invention;

[0015] Figure 2 A top view of the built-in vortex combustion device of the present invention;

[0016] Figure 3 This is a schematic diagram of the structure of the combustion system of the cement decomposition furnace for treating RDF according to the present invention. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is described in detail below in conjunction with specific implementation methods and the accompanying drawings of the specification.

[0018] The decomposition furnace alternative fuel RDF is dried, gasified and initially burned in the built-in vortex combustion device of the present invention, and partially or completely replaces the cement decomposition furnace fuel coal. Figure 1 As shown, the built-in vortex combustion device of the present invention includes a first cylinder 1 and a second cylinder 2, and the second cylinder 2 is connected above the first cylinder 1 and communicated with the first cylinder 1. The outer shells of the first cylinder 1 and the second cylinder 2 are made of steel plates, and the inner lining is made of fire-resistant and heat-insulating materials to improve the overall firmness and high temperature resistance of the device. The second cylinder 2 adopts a cylindrical structure with a volute, and a plurality of tertiary air inlets 3 are evenly distributed on the tangent line of the volute. In this embodiment, the number of the tertiary air inlets 3 is two, and the tertiary air inlets 3 are arranged in a square structure, which is conducive to the formation of swirls by the tertiary air. Two RDF feeding ports 4 are arranged on the top surface of the second cylinder 2. A preheated raw material feeding inlet 5 is arranged on the top surface of the second cylinder 2, and the preheated raw material feeding inlet 5 is located outside the tertiary air inlet 3; specifically, the preheated raw material feeding inlet 5 adopts a square structure and is tilted outward, which is conducive to material dispersion. The preheated raw material feeding inlet 5 is connected with the tertiary air inlet 3. After the material enters the preheated raw material feeding inlet 5, it can rotate with the tertiary air and adhere to the wall to protect the outer wall. A plurality of pulverized coal burners 6 are evenly arranged on the top surface of the second cylinder 2 and the outer wall of the first cylinder 1. A second constriction 8 is arranged on the top surface of the second cylinder 2 for connecting to a cement decomposition furnace. The first cylinder 1 is arranged as a conical structure, and a first constriction 7 is arranged at the bottom of the second cylinder 2 for connecting to a smoke chamber.

[0019] like Figure 3As shown, the present invention also includes a combustion system for treating RDF in a cement decomposition furnace, including a built-in vortex combustion device, a cement kiln tail smoke chamber and a decomposition furnace. The built-in vortex combustion device is arranged between the cement kiln tail smoke chamber and the decomposition furnace. The first cylinder 1 is connected to the cement kiln tail smoke chamber, and the kiln gas enters from the first cylinder 1 through the first constriction 7; the outlet of the second cylinder 2 is connected to the cement decomposition furnace cone 9, and the flue gas and materials in the built-in vortex combustion device enter the cement decomposition furnace cone 9 at high speed through the second constriction 8, and also have a material supporting function; all the tertiary air required for the combustion of the decomposition furnace fuel (generally above 900°C) are divided into two streams and enter the second cylinder 2 tangentially from the volute; RDF is added from two points from the RDF feeding port 4 on the top cover of the second cylinder 2; the C4 cyclone (with five-stage preheating) after multi-stage preheating The materials collected by the vortex combustion device (taking the vortex combustion device as an example) are dispersedly added from the preheated raw meal feeding inlet 5 through the material distribution valve, and adhere to the wall to protect the outer wall with the rotation of the tertiary wind. At the same time, the raw meal is prevented from entering the combustion area too early, which can control the higher temperature in the center of the device and is beneficial to strengthen the combustion of RDF; 4 groups of pulverized coal burners are arranged on the outer wall of the first cylinder 1, and 2 groups of pulverized coal burners are arranged on the top surface of the second cylinder 2. One or several groups of pulverized coal burners can be selected to feed pulverized coal according to the RDF feeding amount, actual on-site operation conditions and NOx control requirements, so as to adjust the temperature field of the vortex combustion device.

[0020] Since RDF enters the high-temperature tertiary air area inside the vortex combustion device, the RDF combustion area has a high temperature, strong turbulent pulsation, and appropriate oxygen content; the tangential flow guide and the second contraction 8 of the volute expand the range of this area, prolong the residence time of RDF in the combustion area, strengthen the gas-solid heat and mass transfer process, and are conducive to the rapid ignition and combustion of RDF; the RDF after preliminary combustion is brought into the decomposition furnace by the high-speed airflow and fills the furnace, is suspended and fully burned, and is organically integrated with the decomposition furnace, breaking through the bottleneck that conventional technology cannot achieve RDF suspension combustion, greatly improving the disposal amount and application scope of RDF, and can achieve a decomposition furnace fuel heat replacement rate of ≥50%.

[0021] In this embodiment, the clinker output reaches 12000t / d, the RDF addition amount is more than 2000t / d, and the heat replacement rate of the alternative fuel RDF accounts for more than 50% of the calciner fuel.

Claims

1. A built-in vortex combustion device, comprising a first cylinder (1) and a second cylinder (2), wherein the second cylinder (2) is connected above the first cylinder (1) and communicated with the first cylinder; characterized in that: The second cylinder (2) adopts a cylindrical structure with a volute, and a plurality of tertiary air inlets (3) are evenly distributed at the rotary cutting line of the volute. After the tertiary air enters the second cylinder (2) from the tertiary air inlet (3), a high-temperature tertiary air area is formed at the top of the second cylinder (2); a plurality of RDF feeding inlets (4) are arranged on the top surface of the second cylinder (2), and RDF enters the high-temperature tertiary air area from the plurality of RDF feeding inlets (4); a preheated raw material feeding inlet (5) is arranged on the top surface of the second cylinder (2) at a position outside the tertiary air inlet (3); A plurality of pulverized coal burners (6) are evenly arranged on the top surface of the second cylinder (2) and the outer wall of the first cylinder (1); The top surface of the second cylinder (2) is provided with a second constriction (8) for connecting to a cement decomposition furnace.

2. The built-in vortex combustion device according to claim 1, characterized in that: The preheated raw material feeding inlet (5) has a square structure and is inclined outwards. The preheated raw material feeding inlet (5) is connected to the tertiary air inlet (3).

3. The built-in vortex combustion device according to claim 1, characterized in that: The tertiary air inlet (3) is in a rectangular structure.

4. The built-in vortex combustion device according to claim 1, characterized in that: The outer shells of the first cylinder (1) and the second cylinder (2) are made of steel plates, and the inner linings are made of fire-resistant heat-insulating materials.

5. The built-in vortex combustion device according to claim 1, characterized in that: The first cylinder (1) is configured as a conical structure, and a first constriction (7) is provided at the bottom of the first cylinder (1) for connecting to the smoke chamber.

6. A combustion system for treating RDF in a cement decomposition furnace, characterized in that: The built-in vortex combustion device according to claim 1 is used, and the system also includes a cement kiln tail smoke chamber and a decomposition furnace, and the built-in vortex combustion device is arranged between the cement kiln tail smoke chamber and the decomposition furnace.

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