Research On Key Technologies Of Multi-component Gas Monitoring In Heating Furnace Combustion Process

Industrial heating furnaces are accompanied by energy consumption and the generation of large amounts of high temperature process gases during the production cycle.Real-time temperatures and component gas concentrations in the furnace reflect the degree of combustion process.Monitoring the key parameters of the combustion process can further feedback and optimize the furnace combustion process control.In addition to the "peak carbon dioxide emission and carbon neutrality" background and the low carbon development goals put forward in recent years.Steel companies have become increasingly interested in monitoring the internal temperature and component concentration of their furnace.Therefore,this paper proposes a time-division multiplexed laser absorption spectroscopy technique for the measurement of multicomponent gas concentration in industrial heating furnace.The calibration of gas concentration is completed by measuring the furnace temperature in combination with colorimetric thermometry.The continuous monitoring of the key parameters of the combustion process of the heating furnace is achieved.The main work and research contents are as follows:(1)For the detection requirements of key combustion gas components and concentrations in the heating furnace.Two simultaneous multi-component gas detection methods are investigated.The method is based on the wide scanning range of a mid-infrared continuous-wave quantum cascade laser,combined with wavelength modulation spectroscopy and harmonic processing.Simultaneous detection of three gases within a single scan cycle from a single light source is achieved.Based on the multi-wavelength and narrow bandwidth characteristics of near-infrared semiconductor lasers.The wavelengths required for detection can be flexibly selected.Combines wavelength modulation spectroscopy with time-division multiplexed scanning techniques.Simultaneous detection of multi-component gases in different wavelength bands within a single scan period.The measurement precision and accuracy of the system are analyzed by designing two configurations of multi-gas detection systems,respectively.Continuous monitoring was performed to demonstrate the feasibility of both methods.Provide support for the method design of the multi-component gas monitoring system in the heating furnace.(2)To meet the demand for high-precision and wide range detection of critical combustion gases in heating furnaces,and to solve the problem of optical path misalignment caused by the unstable structure of the optical machine in the open optical path.Combines the technical advantages of direct absorption spectroscopy and wavelength modulation spectroscopy.The direct absorption signal and the harmonic signal are simultaneously derived by splitting and filtering the detection signal.A wide dynamic range of concentration detection is achieved by automatic switching based on the threshold of the detection concentration variation point.Design of a stepper motor based optical path auto-alignment adjustment system.A closed-loop optical path autoalignment adjustment method is used to complete the stepper motor-controlled optical path auto-alignment.Solved the optical path misalignment problem.(3)Aiming at the problem of high background temperature of industrial heating furnace,many types of detected gases and complex furnace working conditions.By studying the concentration correction method of gases in the combustion process under high temperature background,the influence factors of temperature on the spectral detection are analyzed.A gas concentration correction method based on colorimetric thermometry assistance is proposed to realize the online correction of gas concentration under high temperature background.At the same time,a multi-component gas monitoring system with an opposite-beam foldback optical machine structure on the same side of the transceiver is developed,and the installation structure of the system on the complex furnace is optimized.Semiconductor lasers with center wavelengths of 764 nm and 1567 nm were selected to achieve simultaneous detection of O2 and CO by the same optical path in a single optical structure.Long-term monitoring of billet temperature and gas component concentration in the heating furnace of a domestic steel company was carried out.Based on the monitoring data,detailed analysis of the billet temperature distribution characteristics,component gas concentration distribution characteristics,and heating process characteristics of the furnace heating section and soaking section were conducted.The results show that the system can accurately and online monitor the temperature and gas concentration in the furnace.It can provide effective data support for monitoring the combustion process of the heating furnace and has good guidance significance for the combustion control of the furnace.