Rotary hearth furnace waste heat boiler system with two-stage flue gas regenerative cycle

Abstract

The utility model discloses a rotary hearth furnace waste heat boiler system with two-stage smoke regenerative circulation. The rotary hearth furnace waste heat boiler system comprises an inlet flue, a waste heat boiler radiation heat exchange chamber, a waste heat boiler convection heat exchange chamber and an outlet flue which are sequentially connected in series in the smoke flow direction. One end of a flue gas regenerative circulation header pipe is led out from an outlet flue, the other end of the flue gas regenerative circulation header pipe is connected into a frequency conversion fan, an outlet of the frequency conversion fan is divided into two paths, one path is connected into the waste heat boiler radiation heat exchange chamber through a first-stage flue gas regenerative circulation pipe, and the other path is connected into the waste heat boiler convection heat exchange chamber through a second-stage flue gas regenerative circulation pipe; and the first-stage flue gas regenerative circulating pipe and the second-stage flue gas regenerative circulating pipe are respectively provided with a flue gas flow regulating valve which is used for regulating the flue gas amount returned to the radiation heat exchange chamber and the convection heat exchange chamber. High-temperature flue gas and low-temperature flue gas can be fully mixed by regulating and controlling the reflux quantity of the low-temperature flue gas, the flue gas temperature is rapidly reduced, rapid condensation and sedimentation of high-melting-point materials are facilitated, dust deposition and corrosion of the heating surface of a boiler are relieved, and subsequent dust removal equipment is protected.

Description

Technical Field

[0001] This utility model belongs to the field of flue gas waste heat utilization technology, and relates to a rotary hearth furnace waste heat boiler system with two-stage flue gas reheat circulation. Background Technology

[0002] Rotary hearth furnace technology is a technique that reduces iron ore in materials under high temperature and a specific atmosphere, producing metallized pellets and other products that can be used as raw materials for blast furnaces or electric arc furnaces. With the development of the steel industry and the country's increasing emphasis on environmental protection, more and more rotary hearth furnace production lines have been built in China to process waste materials such as iron-zinc dust from steel plants, achieving resource recycling and reducing environmental pollution. The flue gas temperature generated during rotary hearth furnace production reaches as high as 1000-1300℃. A waste heat boiler is usually installed after the rotary hearth furnace to utilize this waste heat, generating steam for power generation or for production and domestic use. The exhaust gas temperature of the waste heat boiler is generally set at 180-200℃ to meet the temperature requirements of the subsequent bag filter dust collection process. However, because the waste materials entering the rotary hearth furnace are very complex in composition, containing not only iron and zinc but also alkali metals, chlorides, sulfides, etc., and with different melting points and freezing points, the composition of the flue gas generated during rotary hearth furnace production is also very complex. In production practice, when this part of the flue gas enters the rotary hearth furnace waste heat boiler, it often causes ash accumulation and corrosion on the heating surface. In severe cases, it can cause flue blockage and pipe rupture, which in turn leads to boiler shutdown and production stoppage.

[0003] The ash accumulation and corrosion of rotary hearth waste heat boilers are closely related to the temperature and velocity of the flue gas. Firstly, for the boiler inlet section with high flue gas temperatures, a large cavity radiant cooling chamber is used. This utilizes the principle of radiant heat transfer to rapidly reduce the flue gas temperature, while high-melting-point materials in the flue gas solidify and settle within the radiant chamber. Secondly, due to the influence of radiant heat transfer efficiency, the temperature of the flue gas at the outlet of the radiant heat exchange chamber is generally controlled at around 650-700℃ before entering the convective heat exchange surface of the waste heat boiler. According to relevant literature and practical experience, the corrosiveness is most intense when the flue gas temperature is in the 500-700℃ range; therefore, this temperature range must be avoided. Additionally, appropriately increasing the flue gas velocity on the convective heat exchange surface helps remove ash. Thirdly, the exhaust gas temperature of the waste heat boiler is generally set at 180-200℃. This avoids both low-temperature corrosion of the boiler outlet heat exchange surface due to excessively low exhaust gas temperature and burnt-out dust collector bags due to excessively high exhaust gas temperature. However, current rotary hearth waste heat boilers face a significant bottleneck: flue gas temperature and volume are entirely dependent on the rotary hearth combustion process, and cannot be flexibly and autonomously adjusted based on the real-time operating conditions of the waste heat boiler. This significantly limits the boiler's ability to handle complex operating conditions and adds difficulty to solving problems such as ash accumulation and corrosion, urgently requiring the industry to explore innovative solutions. Therefore, it is necessary to design a new rotary hearth waste heat boiler system with flue gas temperature and volume regulation functions to ensure that the rotary hearth waste heat boiler operates under optimal conditions, avoiding and reducing boiler ash accumulation and corrosion. Utility Model Content

[0004] In view of this, the purpose of this utility model is to provide a rotary hearth furnace waste heat boiler system with two-stage flue gas reheat circulation. This rotary hearth furnace waste heat boiler system can adjust the flue gas temperature and flue gas volume of each stage, so that the rotary hearth furnace waste heat boiler can operate under the best working conditions, avoiding and reducing the occurrence of boiler ash accumulation and corrosion.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] A rotary hearth furnace waste heat boiler system with two-stage flue gas regenerative circulation includes an inlet flue, a waste heat boiler radiant heat exchange chamber, a waste heat boiler convective heat exchange chamber, and an outlet flue connected in series according to the flue gas flow direction. One end of the flue gas regenerative circulation main is led out from the outlet flue, and the other end is connected to a variable frequency fan. The variable frequency fan participates in adjusting the total amount of regenerative flue gas according to the actual operating conditions. The outlet of the variable frequency fan is divided into two paths: one path is connected to the waste heat boiler radiant heat exchange chamber through a primary flue gas regenerative circulation pipe, and the other path is connected to the waste heat boiler convective heat exchange chamber through a secondary flue gas regenerative circulation pipe. This guides the low-temperature flue gas on the outlet flue back to the boiler radiant heat exchange chamber and the boiler convective heat exchange chamber, and mixes it with the high-temperature flue gas, thereby reducing the temperature of the inlet flue gas. Flue gas flow regulating valves are respectively installed on the primary and secondary flue gas regenerative circulation pipes, which can participate in adjusting the amount of flue gas returning to the radiant heat exchange chamber and the convective heat exchange chamber according to the actual operating conditions.

[0007] Furthermore, each of the main flue gas reheat circulation pipe, the primary flue gas reheat circulation pipe, and the secondary flue gas reheat circulation pipe is equipped with a vibrator to shake off the accumulated ash adhering to the pipes. The number of vibrators is selected according to the length, size, and degree of ash accumulation of the reheat pipes.

[0008] Furthermore, the main flue gas reheat circulation pipe, the primary flue gas reheat circulation pipe, and the secondary flue gas reheat circulation pipe are all equipped with ash discharge ports. When the ash accumulation reaches a certain level, it is cleaned through these discharge ports.

[0009] The beneficial effects of this utility model are as follows:

[0010] In this invention, the inlet section of the waste heat boiler adopts a radiant heat exchange chamber design. Utilizing the principle of radiant heat exchange, the flue gas temperature is rapidly reduced, causing high-melting-point materials in the flue gas to solidify and settle within the radiant chamber. Simultaneously, a primary flue gas reheat circulation pipe is installed at the inlet section of the radiant heat exchange chamber to recirculate the low-temperature flue gas from the tail end of the waste heat boiler, mixing it with the high-temperature flue gas. This rapidly reduces the flue gas temperature, facilitating the condensation and settling of high-melting-point materials. A variable-frequency fan on the main reheat circulation pipe and a flue gas flow regulating valve on the primary flue gas reheat circulation pipe jointly adjust the amount of low-temperature flue gas flowing back based on the flue gas temperature at the inlet of the radiant heat exchange chamber, thereby regulating the inlet flue gas temperature of the radiant heat exchange chamber. Since the outlet flue gas temperature of the radiant heat exchanger chamber, which is also the inlet flue gas temperature of the convection heat exchanger chamber, is generally controlled at around 650-700℃, and the corrosiveness is most severe when the flue gas temperature is in the 500-700℃ range, a secondary flue gas recirculation pipe is installed at the inlet section of the convection heat exchanger chamber. This recirculates the low-temperature flue gas from the tail end of the waste heat boiler back and mixes it with the high-temperature flue gas, ensuring that the temperature of the mixed flue gas is below 500℃, thus avoiding the area of ​​intense corrosion. The variable frequency fan installed on the main recirculation pipe and the flue gas flow regulating valve installed on the secondary flue gas recirculation pipe can jointly regulate the amount of low-temperature flue gas returning based on the flue gas temperature at the inlet of the convection heat exchanger chamber of the waste heat boiler, thereby regulating the inlet flue gas temperature of the convection heat exchanger chamber. Furthermore, while lowering the inlet flue gas temperature of the convection heat exchanger chamber, the increased flue gas volume leads to a higher flue gas velocity, which is beneficial for removing ash deposits from the convective heating surfaces. In addition, when the flue gas temperature at the outlet of the waste heat boiler is too high, the flue gas temperature can be reduced through regenerative circulation to prevent the filter bags of the downstream dust collector from burning out. In fact, reducing the inlet flue gas temperature of the radiant heat exchanger and the convective heat exchanger can also be achieved by mixing in cold air, but since the flue gas temperature is much higher than the cold air temperature, this would result in a significant energy loss, which is avoided by using flue gas regenerative circulation. Furthermore, since the regenerative circulation flue gas still contains some ash, the vibrators and ash vents installed on the regenerative circulation main pipe, the primary flue gas regenerative circulation pipe, and the secondary flue gas regenerative circulation pipe facilitate ash removal.

[0011] Other advantages, objectives, and features of this invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination and study, or may be learned from practice of this invention. The objectives and other advantages of this invention can be realized and obtained through the following description. Attached Figure Description

[0012] To make the objectives, technical solutions, and advantages of this utility model clearer, the preferred embodiments of this utility model will be described in detail below with reference to the accompanying drawings, wherein:

[0013] Figure 1This is a schematic diagram of the rotary hearth furnace waste heat boiler system with two-stage flue gas reheating circulation in this utility model.

[0014] Attached diagram labels: 1-Inlet flue; 2-Radiant heat exchange chamber of waste heat boiler; 3-Convection heat exchange chamber of waste heat boiler; 4-Outlet flue; 5-Variable frequency fan; 6-Flue gas flow regulating valve; 7-Flue gas reheat circulation main pipe; 8-Primary flue gas reheat circulation pipe; 9-Secondary flue gas reheat circulation pipe; 10-Vibrator; 11-Ash discharge port. Detailed Implementation

[0015] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this utility model. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0016] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the present invention. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0017] In the accompanying drawings of this utility model, the same or similar reference numerals correspond to the same or similar components. In the description of this utility model, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing this utility model 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. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting this utility model. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0018] Please see Figure 1This is a rotary hearth furnace waste heat boiler system with a two-stage flue gas reheating circulation, comprising an inlet flue duct 1, a waste heat boiler radiant heat exchange chamber 2, a waste heat boiler convective heat exchange chamber 3, and an outlet flue duct 4 connected in series according to the flue gas flow direction; one end of the flue gas reheating circulation main pipe 7 is led out from the outlet flue duct 4, and the other end is connected to a variable frequency fan 5, which participates in adjusting the total amount of reheating flue gas according to the actual operating conditions; the outlet of the variable frequency fan 5 is divided into two paths, one of which is connected to the waste heat boiler radiant heat exchange chamber 3 through the primary flue gas reheating circulation pipe 8. One path leads to the radiant heat exchanger 2, and the other path leads to the waste heat boiler convection heat exchanger 3 via the secondary flue gas reheat circulation pipe 9. This allows the low-temperature flue gas on the outlet flue 4 to be drawn back to the boiler radiant heat exchanger and the boiler convection heat exchanger, and mixed with the high-temperature flue gas, thereby reducing the temperature of the inlet flue gas. Flue gas flow regulating valves 6 are installed on the primary flue gas reheat circulation pipe 8 and the secondary flue gas reheat circulation pipe 9, which can participate in the adjustment of the amount of flue gas returned to the radiant heat exchanger and the convection heat exchanger according to the actual operating conditions.

[0019] Vibrators 10 are installed on the main flue gas reheat circulation pipe 7, the primary flue gas reheat circulation pipe 8, and the secondary flue gas reheat circulation pipe 9 to shake off the accumulated ash adhering to the pipes. The number of vibrators 10 is selected according to the length, size, and degree of ash accumulation of the reheat pipes.

[0020] The main flue gas reheat circulation pipe 7, the primary flue gas reheat circulation pipe 8, and the secondary flue gas reheat circulation pipe 9 are all equipped with ash discharge ports 11. When the ash accumulation reaches a certain level, it is cleaned through these discharge ports.

[0021] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of this utility model without departing from the spirit and scope of this technical solution, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.

Claims

1. A rotary hearth furnace waste heat boiler system with two-stage flue gas reheat circulation, characterized in that: It includes an inlet flue, a waste heat boiler radiant heat exchange chamber, a waste heat boiler convection heat exchange chamber, and an outlet flue, connected in sequence according to the flue gas flow direction; one end of the flue gas reheat circulation main is led out from the outlet flue, and the other end is connected to a variable frequency fan. The outlet of the variable frequency fan is divided into two paths: one path is connected to the waste heat boiler radiant heat exchange chamber through a primary flue gas reheat circulation pipe, and the other path is connected to the waste heat boiler convection heat exchange chamber through a secondary flue gas reheat circulation pipe; flue gas flow regulating valves are respectively installed on the primary and secondary flue gas reheat circulation pipes to regulate the amount of flue gas returning to the radiant and convection heat exchange chambers.

2. The rotary hearth furnace waste heat boiler system with two-stage flue gas reheat circulation according to claim 1, characterized in that: The main flue gas reheat circulation pipe, the primary flue gas reheat circulation pipe, and the secondary flue gas reheat circulation pipe are all equipped with vibrators to shake off the accumulated ash adhering to the pipes.

3. The rotary hearth furnace waste heat boiler system with two-stage flue gas reheat circulation according to claim 1, characterized in that: The main flue gas reheat circulation pipe, the primary flue gas reheat circulation pipe, and the secondary flue gas reheat circulation pipe are all equipped with ash discharge ports. When the ash accumulation reaches a certain level, it is cleaned through these discharge ports.

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