A system for producing superheated steam using a rotary hearth furnace with multiple stages of waste heat

Abstract

The present application relates to a kind of system for producing superheated steam by multi-stage waste heat of rotary hearth furnace, belong to metallurgical waste heat recovery technical field.It includes sequentially connected water supply subsystem, first heat exchange subsystem, second heat exchange subsystem, boiler subsystem and superheating subsystem.Water supply subsystem is used to supply desalted water to first heat exchange subsystem;First heat exchange subsystem uses first flue gas to preheat desalted water;Second heat exchange subsystem uses preheated desalted water to cool DRI discharged by rotary hearth furnace, and uses heat exchange when cooling to heat desalted water again, form steam-water mixture;Boiler subsystem uses second flue gas discharged by rotary hearth furnace to heat steam-water mixture to saturated steam;Wherein, second flue gas is formed after dust removal treatment by powder collection to form the first flue gas;Superheating subsystem uses third flue gas generated by flue gas furnace to convert saturated steam into superheated steam.The present application can carry out cascade recovery to flue gas discharged by rotary hearth furnace, product sensible heat and flue gas furnace waste heat, and improve energy utilization efficiency.

Description

Technical Field

[0001] This invention belongs to the field of rotary hearth furnace waste heat recovery technology, and relates to a system for producing superheated steam using multi-stage waste heat from a rotary hearth furnace. Background Technology

[0002] Rotary hearth furnaces, with their strong adaptability to raw materials, low energy consumption, and excellent product quality, have become the preferred process for treating iron- and zinc-containing dust and sludge in the steel industry. This process typically uses steel plant by-product gas as its main fuel. The high-temperature flue gas generated during production, after waste heat recovery and purification, is discharged into the atmosphere, but the final exhaust temperature still reaches 140℃~200℃, indicating insufficient waste heat recovery. Simultaneously, the product DRI discharge temperature reaches as high as 900℃~1100℃, releasing a large amount of sensible heat during cooling, which is also not effectively utilized. Furthermore, the flue gas furnace used for drying green balls has a high and stable outlet flue gas temperature, also possessing considerable heat recovery potential. Currently, there is no integrated system for the cascade recovery of multi-stage waste heat from the rotary hearth furnace (rotary hearth furnace flue gas, product DRI sensible heat, and flue gas furnace flue gas) and the production of superheated steam, resulting in low energy utilization efficiency. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a system for producing superheated steam using multi-stage waste heat from a rotary hearth furnace, so as to solve the problem of insufficient waste heat recovery in existing rotary hearth furnace production lines, thereby improving the waste heat recovery and utilization rate and enhancing the overall energy efficiency of the production line.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A system for producing superheated steam using multi-stage waste heat from a rotary hearth furnace, comprising a water supply subsystem, a primary heat exchange subsystem, a secondary heat exchange subsystem, a boiler subsystem, and a superheating subsystem connected in sequence.

[0005] The water supply subsystem supplies demineralized water to the primary heat exchange subsystem; the primary heat exchange subsystem preheats the demineralized water using first flue gas; the secondary heat exchange subsystem uses the preheated demineralized water to cool the DRI discharged from the rotary hearth furnace, and uses the heat exchange during the cooling of the DRI to reheat the demineralized water, forming a steam-water mixture; the boiler subsystem uses the second flue gas discharged from the rotary hearth furnace to heat the steam-water mixture into saturated steam; wherein the second flue gas is treated by dust collection and removal to form the first flue gas; the superheating subsystem uses the third flue gas generated by the flue gas furnace to convert the saturated steam into superheated steam.

[0006] Furthermore, the primary heat exchange subsystem includes a shell-and-tube heat exchanger, and the water supply subsystem is connected to the inlet of the shell-and-tube heat exchanger via a main water supply pipeline. The outlet of the shell-and-tube heat exchanger supplies preheated demineralized water to the secondary heat exchange subsystem. The demineralized water flows through the tube side of the heat exchanger, and the first flue gas flows through the shell side of the heat exchanger.

[0007] Furthermore, the water supply subsystem is also connected to the outlet of the shell-and-tube heat exchanger via a bypass pipeline to adjust the outlet water temperature of the shell-and-tube heat exchanger.

[0008] Furthermore, the outlet water temperature of the shell-and-tube heat exchanger is adjusted to be maintained between 40°C and 60°C.

[0009] Furthermore, the boiler subsystem includes a waste heat boiler, in which the steam-water mixture enters the steam drum of the waste heat boiler for steam-water separation, and the separated saturated steam is drawn out from the steam outlet of the steam drum and sent to the superheat subsystem.

[0010] Furthermore, the boiler subsystem also includes a deaerator, in which the steam-water mixture first enters the deaerator to remove dissolved oxygen from the water before entering the steam drum in the waste heat boiler.

[0011] Furthermore, the superheating subsystem includes a superheater, the saturated steam enters the superheater tube bundle, the third flue gas enters the superheater shell and flows through the outside of the tube bundle, and the saturated steam in the tube bundle exchanges heat with the third flue gas to be heated and converted into superheated steam.

[0012] Furthermore, the system also includes an intelligent monitoring and control subsystem, which includes monitoring elements and a controller; the monitoring elements are installed on the medium pipelines of the water supply subsystem, the primary heat exchange subsystem, the secondary heat exchange subsystem, the boiler subsystem, and the superheating subsystem; the controller controls each subsystem according to the signals from the monitoring elements.

[0013] Furthermore, the monitoring elements include a temperature sensor, a pressure sensor, and a flow sensor.

[0014] The beneficial effects of this invention are as follows: Other advantages, objectives, and features of the 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, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0015] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a structural block diagram of a system for producing superheated steam using multi-stage waste heat from a rotary hearth furnace, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the cooling machine structure; Figure 3This is a schematic diagram of the monitoring element arrangement. Detailed Implementation

[0016] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0017] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the 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.

[0018] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, 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 the present invention 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 the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0019] like Figure 1 As shown, an embodiment of the present invention provides a system for producing superheated steam using multi-stage waste heat from a rotary hearth furnace. The system includes a water supply subsystem, a primary heat exchange subsystem, a secondary heat exchange subsystem, a boiler subsystem, a superheating subsystem, and an intelligent monitoring and control subsystem. Each subsystem is connected in sequence to perform cascade recovery of multi-stage waste heat from the rotary hearth furnace production line, ultimately producing superheated steam.

[0020] 1. Water supply subsystem The water supply subsystem is used to deliver qualified demineralized water to the primary heat exchange subsystem, and it includes the main water supply pipeline and the bypass pipeline.

[0021] The main water supply pipeline is directly connected to the inlet of the shell-and-tube heat exchanger in the primary heat exchange subsystem, ensuring a normal supply of demineralized water. Simultaneously, the bypass pipeline of the water supply subsystem is connected to the outlet of the shell-and-tube heat exchanger. A bypass regulating valve on the bypass pipeline controls the bypass flow rate, enabling precise regulation of the outlet water temperature and ensuring it remains stably within the optimal range of 40℃ to 60℃, thus creating conditions for the stable operation of subsequent subsystems.

[0022] 2. Primary heat exchange subsystem The primary heat exchange subsystem utilizes the waste heat (approximately 150℃~200℃) of the flue gas discharged from the dust collection and removal equipment to preheat the demineralized water. The primary heat exchange subsystem includes a shell-and-tube heat exchanger, connecting pipes, and a first flow regulating valve.

[0023] The flue gas inlet of the shell-and-tube heat exchanger is connected to the flue gas outlet of the dust collection and removal equipment. Flue gas from the dust collection and removal equipment flows through the shell side of the heat exchanger, where it undergoes counter-current heat exchange with the demineralized water flowing in the tube side, preheating the demineralized water to 40℃~60℃. The outlet of the shell-and-tube heat exchanger is connected to the inlet of the secondary heat exchange subsystem via a connecting pipe, allowing the preheated demineralized water to enter the next heating stage. The first flow regulating valve is located on the connecting pipe.

[0024] 3. Secondary heat exchange subsystem The secondary heat exchange subsystem is used to further heat the preheated demineralized water. It includes a finished product cooler, as well as connecting pipes and a second flow regulating valve.

[0025] The high-temperature DRI (approximately 900℃~1100℃) discharged from the rotary hearth furnace directly enters the finished product cooler. The finished product cooler is a horizontal rotary structure, such as... Figure 2 As shown, its cylinder is a membrane water-cooled wall. During the rotation of the cooler, the high-temperature DRI and the demineralized water flowing inside the membrane water-cooled wall undergo efficient heat exchange. After absorbing the sensible heat released by the DRI, the temperature of the demineralized water further increases, forming a steam-water mixture of about 100°C to 110°C; while the DRI is cooled to below 200°C and then discharged.

[0026] The outlet of the secondary heat exchange subsystem is connected to the inlet of the boiler subsystem via a connecting pipe, which transports the steam-water mixture to the next process. The second flow regulating valve is installed on the connecting pipe.

[0027] The finished product cooler integrates product cooling and waste heat recovery into one unit, with a compact structure and high heat exchange efficiency.

[0028] 4. Boiler Subsystem The boiler subsystem is used to process the steam-water mixture into saturated steam. The boiler subsystem includes a deaerator and a waste heat boiler (including a steam drum) connected in sequence, as well as connecting pipes and a third flow control valve. The flue gas inlet of the waste heat boiler is connected to the high-temperature flue gas outlet of the rotary hearth furnace.

[0029] The specific workflow of the boiler subsystem is as follows: The high-temperature steam-water mixture from the secondary heat exchange subsystem first enters the deaerator, where dissolved oxygen is removed through thermal deoxygenation. The deaerated steam-water mixture then enters the steam drum of the waste heat boiler, where steam-water separation occurs. The separated saturated water is returned to the waste heat boiler for recirculation and heating to continuously evaporate steam. The separated saturated steam (below 300℃) is drawn from the steam drum outlet and sent to the superheated subsystem via a connecting pipe. A third flow control valve is located on this connecting pipe.

[0030] 5. Superheated Subsystem The superheating subsystem is used to convert saturated steam into superheated steam. This subsystem includes a superheater, connecting pipes, and a fourth flow control valve. The flue gas inlet of the superheater is connected to the flue gas outlet of the flue gas furnace.

[0031] The specific workflow of the superheated subsystem is as follows: The superheater's heat source is taken from the flue gas furnace. The high-temperature flue gas (approximately 600℃~700℃) generated by burning by-product coal gas in the furnace is introduced into the superheater shell and flows through the outside of the heat exchange tube bundle, where it efficiently exchanges heat with the saturated steam flowing inside the tube bundle. After absorbing heat, the saturated steam's temperature rises, becoming superheated steam that meets the requirements. The superheater's steam outlet is connected to the external steam network via a connecting pipe, delivering the produced superheated steam to the plant's steam network for use by various users. A fourth flow regulating valve is installed on the connecting pipe.

[0032] 6. Intelligent Monitoring and Control Subsystem The intelligent monitoring and control subsystem includes monitoring elements and controllers.

[0033] The monitoring elements include temperature detection units, pressure detection units, and flow detection units, which are respectively installed on the critical medium pipelines of the water supply subsystem, primary heat exchange subsystem, secondary heat exchange subsystem, boiler subsystem, and superheating subsystem. Figure 3 As shown in this embodiment, the temperature detection unit, pressure detection unit, and flow detection unit are preferably temperature transmitters (TT), pressure transmitters (PT), and flow transmitters (FT), respectively, used to transmit the detection signals to the controller. Figure 3 In this context, FCV stands for flow control valve.

[0034] The controller is responsible for centrally receiving and processing the signals from the aforementioned sensors, and issuing commands according to preset logic to achieve automatic regulation. Simultaneously, the controller communicates with the main controller of the rotary hearth furnace production line to achieve data exchange and coordinated control in response to changes in production line load.

[0035] The preset logic includes: Based on the temperature signal of the preheated demineralized water at the outlet of the shell-and-tube heat exchanger, adjust the opening of the bypass regulating valve on the water supply subsystem to maintain the outlet water temperature stably between 40 and 60°C.

[0036] Adjust the rotation speed of the finished product cooler according to the DRI temperature discharged from the cooler to control the residence time of the DRI in the cooler, thereby ensuring the heat exchange effect and the discharge temperature.

[0037] Based on the set target temperature of superheated steam, the flow rate of flue gas introduced into the superheater shell is adjusted to control the heat exchange and ensure that the output superheated steam temperature meets the standard.

[0038] The controller communicates with the main controller of the rotary hearth furnace production line and adjusts the operating parameters of each subsystem in a coordinated manner according to changes in the overall load of the production line (such as changes in flue gas volume and DRI output) to achieve dynamic balance.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention 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 solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A system for producing superheated steam using multi-stage waste heat from a rotary hearth furnace, characterized in that, The system comprises a water supply subsystem, a primary heat exchange subsystem, a secondary heat exchange subsystem, a boiler subsystem, and a superheating subsystem, which are connected in sequence. The water supply subsystem supplies demineralized water to the primary heat exchange subsystem; the primary heat exchange subsystem preheats the demineralized water using the first flue gas; the secondary heat exchange subsystem uses the preheated demineralized water to cool the DRI discharged from the rotary hearth furnace, and uses the heat exchange during the cooling of the DRI to reheat the demineralized water, forming a steam-water mixture; the boiler subsystem uses the second flue gas discharged from the rotary hearth furnace to heat the steam-water mixture into saturated steam; wherein, the second flue gas is treated by dust collection and removal to form the first flue gas; the superheating system uses the third flue gas generated by the flue gas furnace to convert the saturated steam into superheated steam.

2. The system according to claim 1, characterized in that, The primary heat exchange subsystem includes a shell-and-tube heat exchanger. The water supply subsystem is connected to the inlet of the shell-and-tube heat exchanger via a main water supply pipeline. The outlet of the shell-and-tube heat exchanger supplies preheated demineralized water to the secondary heat exchange subsystem. The demineralized water flows through the tube side of the heat exchanger, and the first flue gas flows through the shell side of the heat exchanger.

3. The system according to claim 2, characterized in that, The water supply subsystem is also connected to the outlet of the shell-and-tube heat exchanger via a bypass pipeline to regulate the outlet water temperature of the shell-and-tube heat exchanger.

4. The system according to claim 3, characterized in that, The outlet water temperature of the shell-and-tube heat exchanger is adjusted to be maintained between 40°C and 60°C.

5. The system according to claim 1, characterized in that, The boiler subsystem includes a waste heat boiler. The steam-water mixture enters the steam drum in the waste heat boiler for steam-water separation. The separated saturated steam is drawn out from the steam outlet of the steam drum and sent to the superheat subsystem.

6. The system according to claim 5, characterized in that, The boiler subsystem also includes a deaerator. The steam-water mixture first enters the deaerator to remove dissolved oxygen from the water before entering the steam drum in the waste heat boiler.

7. The system according to claim 1, characterized in that, The superheating subsystem includes a superheater. The saturated steam enters the superheater tube bundle, and the third flue gas enters the superheater shell and flows through the outside of the tube bundle. The saturated steam in the tube bundle exchanges heat with the third flue gas and is heated to become superheated steam.

8. The system according to any one of claims 1 to 7, characterized in that, The system also includes an intelligent monitoring and control subsystem, which includes monitoring elements and a controller. The monitoring elements are installed on the medium pipelines of the water supply subsystem, the primary heat exchange subsystem, the secondary heat exchange subsystem, the boiler subsystem, and the superheating subsystem. The controller controls each subsystem based on the signals from the monitoring elements.

9. The system according to claim 8, characterized in that, The monitoring elements include a temperature sensor, a pressure sensor, and a flow sensor.

Images