Low-Light Endoscopic Imaging Method And Its Application For Blast Furnace Burden Surface Detection

The blast furnace ironmaking process is a crucial step in the steel industry,which is a pillar industry of the national economy.However,it is also the most energy-consuming and emission-intensive process in the steel industry.The blast furnace smelting reactions are complex and complicated,and the blast furnace smelting process is dynamic are changeable,which necessitates the real-time monitoring of the operating status and key parameters of the blast furnace as feedback information for regulating furnace conditions,thereby ensuring stable operation of the blast furnace.The topography information of the blast furnace burden surface,which can reflect the smelting state and the gas flow distribution,which is one of the important reference information for discovering abnormal furnace conditions and optimizing the burden distribution operation.Therefore,real-time and online acquisition of topography information of the blast furnace burden surface is of great significance for stabilizing blast furnace operation,optimizing gas flow distribution,improving smelting energy efficiency,and reducing energy consumption and carbon emissions.Visible imaging technology offers advantages of intuitive visualization with rich information,which can directly display the morphology distribution and motion state of the blast furnace burden surface.Therefore,it has enormous potential for blast furnace burden surface monitoring.However,the blast furnace is a large-scale and closed countercurrent reaction vessel with a complex and harsh environment of high temperature,dust,and weak light,which poses significant challenges to visible imaging technology.Existing visible light imaging technologies face several limitations,such as insufficient illumination,low imaging quality,limited imaging range,and unstable imaging status.The limited performance of blast furnace surface detection based on visible light imaging technology restricts the development of blast furnace smelting to digitalization,automation and low carbonization.To address the problem posed by the complex and harsh environmental factors of the blast furnace when using visible light imaging technology to detect its surface,this thesis comprehensively and systematically explores various aspects such as imaging methods,instrument design,installation optimization,and system development.It proposes a Low-light Endoscopic Imaging Method and Its Application for Blast Furnace Burden Surface Detection.This method has successfully obtained clear burden surface videos with a large range and rich morphology information in realtime online detection.The main research achievements and innovations are as follows:(1)A low-light imaging method based on brightness-response range matching is proposed.To solve the issue of insufficient illumination for imaging the blast furnace burden surface caused by weak light environments with local dynamic strong light interference,a weak light imaging method based on brightness-response range matching has been proposed.Firstly,a photoelectric-digital signal conversion model for the entire optical imaging process of the burden surface was constructed to reveal the interference mechanism of weak overall light and strong local light on high-quality imaging of the burden surface.Based on this,weak light imaging performance is improved by increasing the relative aperture of the imaging optical system,extending the transmission path,and using an image sensor with high photoelectric conversion efficiency.Simultaneously,an automatic exposure algorithm based on adaptive analog gain has been designed to suppress strong light interference,match the brightness range of the burden surface with the response range of the optical imaging equipment,and achieve imaging with rich morphology information.This method also provides a new approach for high-quality imaging in similar lighting conditions.(2)An endoscopic imaging optical system with large depth of field,wide field of view,and large aperture is designed.To overcome the challenges of low-quality burden surface imaging caused by high temperature and large spatial range in the furnace,a large depth of field,wide field of view,and large aperture endoscopic imaging optical system for the burden surface has been designed.Firstly,the quantitative relationship between imaging characteristic parameters is described based on the principles of geometric optics.Secondly,the design indicators that are best matched to the blast furnace are calculated based on an analysis of its characteristics.Finally,under the guidance of optical design principles,an optical structure with multiple imaging stages is proposed,consisting of a retroreflecting objective and a rod lens relay system,according to the design indicators.This results in an endoscopic imaging optical system with a large aperture,a wide field of view of 60 degrees,a clear imaging range of 0.8m to infinity,and an aperture number of 5,with an overall length of 1.6m,enabling clear imaging of the burden surface.This design also provides a reference for the analysis of performance indicators and structural design of imaging optical systems for large enclosed containers.(3)A method for improving the imaging range of the burden surface based on equipment installation posture optimization is proposed.To address the challenges of limited imaging range caused by the complexity of equipment and high temperatures in the closed blast furnace,a method for improving the imaging range of the burden surface based on equipment installation posture optimization is proposed.Firstly,an original model for the burden surface optical imaging equipment’s field of view coverage based on spatial coordinate transformation is constructed to provide a way to describe the three-dimensional coverage range of the optical imaging equipment.Secondly,a calculation method for the imaging area of the burden surface is given by combining the distribution characteristics of the burden surface and the field of view coverage model,revealing the quantitative relationship between the equipment installation posture and the imaging area of the burden surface.Then,a field of view coverage enhancement algorithm based on particle swarm optimization is proposed to provide an effective means for optimizing the installation posture to maximize the effective imaging area of the burden surface.This method effectively increases the coverage area of the optical imaging equipment’s field of view on the burden surface and achieves an improved imaging range of the burden surface.Additionally,this method provides a reliable way to improve the coverage range of the optical imaging equipment on the target area.(4)A real-time and on-line detection system of blast furnace burden surface is developed.To solve the problem of unstable imaging status of equipment caused by high temperature,high dust,and high-frequency vibration in blast furnaces,a real-time online detection system for blast furnace burden surface is developed.Firstly,an inner-pipe endoscope consisting of a water-air dual cooling structure protective shell and an integrated imaging system is developed to overcome the harsh environment of high temperature,high pressure,and dust vibration in the blast furnace.Then,a burden surface monitoring platform is developed to meet the industrial software requirements for burden surface detection.Finally,the real-time online detection system for blast furnace burden surface is applied in the blast furnace site,providing real-time and informative blast furnace burden surface videos for on-site personnel,and laying a data foundation for researchers to study the operating mechanisms and reveal the smelting laws.